Final Design Review Report
Design of a Particulate Material
Compression Feed Screw for Research and
Data Collection
Submitted to:
Dr. Marcial Gonzalez
Dr. Carl Wassgren
Dr. Charles Jensen
Abhishek Paul
Submitted by:
The Feed Screw Speed Crew:
Marcus Gunyon
Mohammed Matar
Josh Meiners
Evan Selking
Yun-Jui Jeremy Tu
Rachel Wasem
8/4/2020
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Executive Summary:
Our mission was to produce a cost-effective, modular tabletop design of a compression
feed screw for formulation and validation of predictive models of torque, angular speed, and
mass flow. Currently, the project is prepared for fabrication, as all manufacturing and systems
design is complete. The team members’ leads, charter, and schedule can be found in Appendix
A, B and D. The focus of this phase has been finalization of the prototype and validation of met
engineering requirements, summarized in Table 1 below and detailed in Appendix Q:
Table 1: Customer Requirements and Validation of Parameters
Close attention to mitigation of risk (Appendix E) and adherence to the project budget
(Appendix C) resulted in a safe and readily accessible means of data model validation costing
tens of dollars instead of thousands per test. Providing a personal feed screw also allows for
more thorough improvement in the researcher’s models, leading to exponentially larger
improvements and smaller costs of feeding issues in multi-million dollar biorefineries, saving
them up to $1,000,000 per year. The final prototype, as pictured in Figure 1 below, was
mechanically and electronically designed to provide repeatable feeding experiments while
producing useful data for model validation.
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Figure 1: Photo-Realistic Render of Fully Assembled Device
The mechanical model was dimensioned as a scale model (Length: 53 in. Width: 9.5 in.
Height: 10.5 in., Weight: 103 lbs) of a provided basic feed screw. The team innovated this design
to include clamshelled casing, flexible chain coupling, a motor and modular supporting stand,
and a simulating, spring loaded back-pressure plate to resist flow of biomass. The basic model
alone was previously unable to collect or electronically record any operational data, lacked
flange connections, and only included 4 total parts. Perhaps the largest innovation made was the
creation of the pressure plate, made up of a 45 degree cone extruding to block the end of the
plug, forced against fed particulate material by 4 15 lbs/in springs. The springs are pushed by a
1/16 in. A36 Steel plate that butts up against a load cell, which is attached to a supported 9.5 in.
square plate. The 9.5 in. plate’s supports are then screwed into one of 5 potential steel insert
locations. These locations were chosen specifically to provide spring displacements that will
cause 50 psi, 30 psi, and 15 psi of pressure on the fed material. A closer view of the pressure
plate apparatus can be seen below in Figure 2. Appendix G illustrates all the innovations made to
the physical design, while Appendix H validates operability. Products of the design process,
including benchmarks and sketches exist in Appendices N and F respectively.
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Figure 2: Photo-Realistic Render of Pressure Plate Apparatus
The device allows for user control of motor speed, controlled by a potentiometer. Once
running, an Arduino collects readings of shaft speed, motor power, pressure load, torque, and
strain on 12 different bolt connections and records them each second. This data is placed into
visual time graphs, highlighting maximum and minimum values and when variations may occur.
The mass flow is also measured using a simple scale underneath the exit of the feed screw, from
which average mass flow is calculated by dividing mass collected by time of operation. A wiring
diagram, displaying the Arduino based circuit is seen below in Figure 3, while Figure 4 shows
the data table and example graph that the operator would see automatically updating while
running the device. Appendices I, J, and K contain further details, as well as the electronic
schematic, Arduino code, and a flow chart.
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Figure 3: Full Wiring Diagram
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Figure 4: Automatically Updating Example Graph and Data Collection Table
The parts as seen in Figure 1 will be manufactured 1 of 3 ways: Xometry custom
manufacturing, personal manufacturing at Bechtel Innovation Design Center, or pre-
manufactured part orders. Manufacturing drawings for parts produced in BIDC or Xometry can
be found in Appendix L, and links for any needed purchases are found in Appendix R. Further,
Appendices M, O and P outline what was learned from each of the three prototypes produced
during the project, the basic physics model of the device, and a list of standards referenced.
Appendix U was used to confirm the necessary tolerances of these manufactured parts.
Given all this information, the team requests that the researchers fabricate and assemble
the design using steps listed in Appendix S, the manufacturing plan laid out in Appendix T, and
apply all physical validations stated in Appendix Q before operating.
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Contents
Appendix 8
A: Team Members and Organization Structure 8
B: Charter 9
C: Business Case and Project Budget 10
D: Work Breakdown Structure and Project Schedule 13
E: Risk Mitigation 15
F: Sketches 17
G: Mechanical CAD 30
H: Mechanical CAE 36
J: Arduino Code 54
K: Flow Chart of Control/Operation 63
L: Manufacturing Drawings 67
M: What was Learned from the Low, Mid, and High-Fidelity Prototypes 86
N: Benchmark research 88
O: Basic Physics Model (Free Body Diagram) 91
P: Standards Referenced/Used/Applied 96
Q: Testing and Validation 98
R: Links to Purchased Components and Display Videos 100
S: Assembly Instructions 104
T: Manufacturing Plan 112
U: Table of Fits and Tolerances 115
NOTE:
For the Final Design Review (FDR), each Appendix was finalized. The updated
appendices from the Critical Design Review (PDR) exist in appendices A through P. While they
were created for the PDR, they reflect progress made in preparation for the CDR and FDR.
Significant changes from CDR to FDR can be found in Appendices F, G, H, J, L, M, P, Q, R, S
and T. All new appendices created specifically for the CDR exist after Appendix P.
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Appendix
A: Team Members and Organization Structure
The roles and coverage of the six members of the Feed Screw Speed Crew has not
changed since the CDR stage as seen in Table 2.
Table 2: Team Organization structure
Team Member Role Coverage Contact
Information
Rachel Wasem Research and Sketch
Artist
Sketches, WBS, Project
Schedule and Notebook,
Project Vision
Marcus Gunyon CAD Lead Dimensioning, Control of
files, Incorporating
sketches into CAD
Josh Meiners Organizer and Editor Formatting, Drafting,
Project Scoping,
Brainstorming
Mohammed
Matar
Risk Management
and FEA
Budgeting, FEA Analysis,
Manufacturing Research
Yun-Jui
(Jeremy) Tu
Controls and Coding Motor and Sensor Control,
Arduino Coding, Wiring
Flow Charts/ Diagrams
Evan Selking Instrumentation Research and Sensor
Selection, Sensor CAD
File Control
The project clients are shown in Table 3 with their contact information. Each client has
offered ideas, project guidance, and standards to be met by the team. They are available via
email at any time and have scheduled meetings with the team every week on Tuesdays at 9:00
AM.
Table 3: Client Organization structure
Client Contact
Abhishek Paul [email protected]
Dr. Carl Wassgren [email protected]
Dr. Marcial Gonzalez [email protected]
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B: Charter
Appendix B includes the project charter, shown below in Figure 5, which reflects the
final vision statement of the team and a basic overview of the project in the current FDR stage.
The project charter was last updated to include more risks and clarify some resources required
(such as machining and assembling).
Figure 5: Team charter stating a basic overview of the project
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C: Business Case and Project Budget
Appendix C provides the justification and financial planning of the project. Updated
business model benefits for the FDR have been appended to the end of this section.
The project budget was finalized for fabrication and is shown in Figure 6. The total cost
of the device is estimated to be $4,649.05 (92.98% of budget), with the addition of generous
estimates of $1,000 for shipping costs and $500 for the motor that still has yet to deliver a quote,
leaving $350.95 left in the $5,000 budget. The bulk of this cost ($1603.02) comes from the
manufacturing costs of the specialized casing and screw needed for this project. This
manufacturing will be done with Xometry, an on-demand industrial manufacturer of custom-
made parts. Having an outside manufacturer was chosen rather than writing machining
instructions for the clients for a few reasons. Firstly, as the clients are research professors at
Purdue University, the clients indicated they would rather receive completed parts and only have
to spend time doing minimal assembly. Secondly, the $5,000 budget leaves the team with this
option, and having professionals manufacture it will minimize risks that arise from having the
Feed Screw Speed Crew relay instructions to another team. Other parts that are simple shapes
and made out of either Aluminum 6061 or A36 Steel can be left for the researchers to assign to
an undergraduate for manufacturing utilizing the provided drawings in the Bechtel Innovation
and Design Center. Finally, profit is not the motivation for this project, and minimizing risks is
worth this added cost.
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Figure 6: Project Budget List
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The device will save researchers both time and money. The current arrangement requires
them to spend $10,000 for every test, while having to wait months for results from the industrial
model. A personal tabletop device therefore shortens the wait time for results to days or weeks,
allowing much more data to be gathered and more tests to be run in the same timespan. By
having a robust system, it allows them to have more confidence in their models and ensure their
robustness. On a larger scale, the estimation is that it will save industrial plants anywhere from
$100,000 to $1,000,000 per year. It will also allow them to collect data that the industrial plant
cannot provide.
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D: Work Breakdown Structure and Project Schedule
Appendix D contains documents that allow the team to plan and manage the project.
A work breakdown structure is seen below in Figure 7 that indicates the different tasks
that were completed throughout the different phases of the project. The chart was updated to
include the more detailed tasks done for the FDR, such as the Assembly Instructions and Testing
and Validation. These tasks have been put into a schedule seen in Figure 8. Specific tasks were
divided among the team members based upon their role assignments as seen in Table 1 and are
shown in the resources column.
Figure 7: Work Breakdown Structure highlighting the different tasks needed for the project
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Figure 8: Project schedule showing the timeline of the project
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E: Risk Mitigation
Appendix E includes the risk mitigation spreadsheet that was compiled by the team. It has been
updated to reflect the risks identified throughout the entirety of the project.
The team’s risk mitigation spreadsheet is seen in Table 3. The risk mitigation spreadsheet
was updated to reflect the risk mitigation strategies developed since the beginning of the project,
such as the installation of a specially designed mesh, allowing for only the particulate material
and the non-handle end of a stoking rod to enter the hopper. Damage to the device caused by
excessive torque due to blockages will be prevented by a torque limiter that will shut down the
device if a certain torque output is surpassed. There will also be a manual emergency stop button
unforeseen contingencies. Some new risks were identified, such as the risks arising from using a
custom manufacturer, Xometry, for the parts.
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Table 3: Risk Mitigation Spreadsheet
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F: Sketches
Appendix F contains the various sketches compiled over the course of the design process.
Additions to the sketches during preparation for the FDR can be found after Figure 16.
Figure 9 shows the different support methods explored by the team to hold the modular
barrels in place. The left design uses simple supports, the middle uses clamps, and the right uses
rotating arms. The clamp and arms were considered for their superior ability to adapt to
differently sized barrels, however the simplicity of the simple support coupled with a decreased
need for full adjustability rendered the simple support the best design choice. Therefore, Team
down selection led to the selection of the static support structure, as seen in Appendix G.
Figure 9: Sketch of potential support methods
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The decision matrix in Figure 10 was utilized to compare the three main group ideas for
how to support the device and its modular capabilities. Originally, the rotating pads was the
leading idea when it was incorrectly believed to have a need for vast variation in dimension.
Once it was clarified that the supports only needed to hoist similar parts with 2 differing inside
diameters, the normalization caused the simple supports to be the final chosen support frame
design.
Figure 10: Decision Matrix for Down Selection of Support Frame
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Figure 11 illustrates the location and usage of the RPM Hall Effect Sensor. A gear
attached to the rotating drive shaft will have teeth passing over the inducting sensor, registering a
readable angular velocity, that when wired to the Arduino will output the RPM of the driveshaft
and contribute to torque calculation. This gear and sensor combination can be placed anywhere
along the driveshaft in between the hopper and motor.
Figure 11: Sketch of RPM Hall Effect Sensor Location
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Figure 12 shows how the different sections will be attached using flanges in both a front
view and a side view to highlight the connections between the top and bottom halves of the
barrel as well as the connections between barrel sections. The strain gauges posted at the flanges
of the clamshell design will serve to measure load on the outer caging of the feed screw.
Figure 12: Sketch of assembled screw casing, front view and side view
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Figure 13 illustrates the mass flow system, within which biomass will flow out of the
plug and into a collection bin to be weighed. Alternative methods for mass flow measurement
were considered, but in Down Selection this was by far the least complicated and most cost-
efficient option. It is important to realize that the back pressure plate posted at the end of the plug
is representative of the pressure from what would be a chemical reactor. The plate is designed to
apply various amounts of pressure for testing of multiple different reactor needs.
Figure 13: Sketch of Back Pressure Plate and Mass Flow Sensor or Scale
Figure 14 illustrates the concepts created while exploring how to generate a controllable
and measurable back pressure. The first utilizes a load cell to measure the force applied by a
linear actuator. Fluctuations in the measured load during testing due to the forces applied by the
material exiting can be tracked. The middle concept utilizes springs to calculate the force exerted
when a linear actuator moves the plates closer together. Again, variations measured by the force-
sensitive plate can be tracked during experiments. However, this design could unevenly apply
back pressure as the material exiting will disproportionately compress the bottom springs. This is
improved on in the final design, which allows the plate to slide along rigid rods like the first
design to limit the possible rotation of the plate.
Figure 14: Sketches of Back Pressure Plate Concepts
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The decision matrix in Figure 15 was utilized to compare the three main ideas for the
pressure plate design. The deciding factors were the cost and ability to limit rotation to ensure
accurate force readings.
Figure 15: Decision Matrix for Back Pressure Plate
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Figure 16 shows different designs that were considered for the clamshell sections of the
tapered zone and the plug. The first would reduce the number of moving parts by connecting the
bolts to the casing by a pin, which would allow the bolts to be loosened and removed without
having as many pieces to keep track of. The hinge design would allow the two sections of the
flange to rotate and open without having to remove any parts, however it might not be able to
withstand the pressures inside
Figure 16: Alternative designs for clamshell
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Figure 17 represents a schematic drawing for the creation of the CAD model displaying
the coupling of the feed screw shaft to the motor’s drive shaft. Exiting the hopper, the screw
shaft encounters a large bearing that supports the shaft and allows free rotation. A 1 inch gap, the
shaft runs through the first of 3 bored sprockets. The first sprocket runs its teeth just above the
Hall-Effect sensor, incrementing each time a tooth passes by to measure the actual RPM of the
rotating screw. The middle sprocket is then coupled with the motor-side sprocket with a double
chain. The screw shaft ends inside the chained section, and the motor shaft begins. The Motor
shaft enters the motor-side sprocket, where it is attached to the motor just outside. This coupling
is a flexible coupling, meaning that up to 1 degree of misalignment between the motor shaft and
screw shaft will not affect the driving of the feed screw.
Figure 17: Screw/Motor Shaft Coupling Schematic
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Figure 18 displays a schematic drawing for the creation of the CAD model displaying the
back-pressure plate. The 45 degree conical steel plug is inserted into the end of the feed screw,
plugging both the 1.5 in. or 1.25 in inner diameter modular parts. A flange attached at the end of
the casing supports 4 0.25 in. diameter rods that act as rails for the following plates to slide upon,
and supports for the springs. The conical plug is part of a square A36 steel plate that sits on the
rails. Between this plate and the one to follow, 4 springs with a k value of 15 lbs/in apply axial
force to the conical plug plate along the rails. This pushes the plug into the casing to block
feeding material and apply a specific pressure to simulate chemical reactor back-pressure. The
A36 steel plate on the opposite side of the springs will be a simple 1/16 in. plate that will
experience the equal and opposite force from the springs, and push onto a load sensor attached to
the plate just to the right of it. The A36 steel plate containing the load cell, is then supported by
90 degree shelf supports. The location of these shelf supports will depend on the desired
pressure, compressing the springs a specific amount to apply a specific force to the specific area
of the feed exit, producing a predetermined pressure to the fed material.
Figure 18: Pressure Plate Schematic
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Figure 19 and 20 include a drawing and list to communicate the necessary location of the
shelf supports. The customer requirements state that pressures of 50 psi, 30 psi, and 15 psi need
to be able to be applied to both the 1.5 in. and 1.25 in. inner diameter parts. Since the areas will
differ, there are 6 locations for the shelf supports to sit in order to apply the listed pressures. The
supports will be bolted into the bottom plate in three locations, marked with press-fit inserts
supporting ¼ in. bolts. After calculation, it was found that 2 of the 6 cases only differed by 0.01
inches, meaning that only 5 total sets of holes were needed. Cases A through C in Figure 20
represent locations for the 1.5 in. diameter hole and apply 50 psi, 30 psi, and 15 psi respectively.
Cases D through F do the same, but for the 1.25 in. diameter case. These locations were
determined based on spring compression calculated from the excel sheet in Appendix H.
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Figure 19: Shelf Support Bolt Locational Schematic
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Figure 20: Horizontal Shelf Support Bolt Locations
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Figure 21 a schematic drawing for the creation of the CAD model displaying shelf
support bolt location in the vertical A36 steel plate holding the load cell. Each set of holes is
displaced by ½ in. to account for the separation of the bolt holes on the bottom plate.
Figure 21: Horizontal Shelf Support Bolt Locations
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G: Mechanical CAD
Appendix G demonstrates the final FDR design. It offers explanations regarding its concept and
the relationships between parts.
As seen below in Figures 22 and 23, a lot of progress has been made from the low-
fidelity prototype to the high-fidelity prototype. Many additions to the original provided CAD
file have been made, since this file only included a rough representation of the hopper, throat,
plug and screw. The additions include the clam-shelled designs of the throat and plug for access
in instances of blockage. A protective grate was added to the top of the hopper for limb safety.
All sensors, their locations, software, and circuit were created so that the operator is able to
produce data and store it for analysis. The motor was selected by the team, and configured to
couple with the feed screw shaft, while being electronically controlled by a RPM Potentiometer.
The team also designed the pressure plate at the exit of the feed screw, to provide multiple
different reactor-simulating back-pressures, including the use of steel plates, load cells to display
the exact force, and carefully placed mounts to achieve correct spring displacement. To present
the Mechanical CAD model, Figure 24 through Figure 32 display zoomed in views, and are
labeled with the portion of the design they emphasize.
Figure 22: Low-Fidelity Prototype
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Figure 23: High-Fidelity Prototype
Figure 24: Electronic Components Laid out and Wired
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Figure 25: Hopper Zoom with view of Feed Screw Within
Figure 26: Shaft Coupling Zoom with visible Hall-Effect Sensor Location
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Figure 27: Motor Support System and Control Panel
Figure 28: Backside view of Control Panel
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Figure 29: View of Main Body of Feed Screw Casing
Figure 30: Zoom of Spring Loaded Pressure Plate Apparatus
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Figure 31: View of Mass Flow System with Base Plate Mounted Load Cells
Figure 32: View of Pressure Plate’s Supporting Brackets, Mounted into the Base Plate
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H: Mechanical CAE
To analyze the material and thickness of the design, finite element analyses studies were
carried out in Solidworks. For preprocessing, a mesh was created using parabolic tetrahedral
elements with global element size of 9 mm was used as seen in Figure 33. 110827 nodes were
created (corresponding to 66714 elements). This fine mesh was used to avoid interference errors,
particularly in the hopper mesh section.
Figure 33: Visible Mesh for FEA
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To analyze the case, a pressure load was applied on the screw and plug sections as seen in
Figures 34 and 35 to simulate the pressure from the back reactor, leaving the base plate fixed.
The pressure is assumed to parabolically grow from 350 Pa at the beginning of the screw section
to a peak of 15 MPa at the screw-plug junction, with the pressure values being specified by the
clients. The pressure value then exponentially decays to a value equal to the back pressure
simulated (in this study a pressure of 0.3447 MPa, which amounts to 50 psi). Figures 36 and 37
show a graphical representation of the applied pressure function.
Figure 34: Pressure Loading Exponentially Increasing Along Junction
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Figure 35: Pressure Loading Exponentially Decreasing Along Screw
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Figure 36: Pressure Representation Along Screw, with 0 Distance at the Screw-Plug Intersection
Figure 37: Pressure Representation Along Junction, with 0 Distance at the Screw-Plug
Intersection
After applying the pressure load, the material of the case was selected to be 6061-T6
aluminum. With a maximum yield strength of 275 MPa and at a cost of $4.54/lb (See Budget in
Appendix C), the material was selected as a good balance between strength and affordability.
Due to the peak pressure value being applied at the screw-plug junction, the thickness of the
junction was also analyzed and chosen to ensure structural integrity of this critical point. With a
thickness of 0.25 inches, the displacement plot and the Von-Mises stress plot were generated.
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The displacement plot seen in Figure 38 determined a maximum displacement of
4.339*10-3 mm at the junction, indicating no major deformation overall.
Figure 38: Displacement Distribution on Casing (mm)
The Von Mises stress plot in Figure 39 indicated a maximum stress of 23.1 MPa at the
junction. With a maximum yield strength of 275 MPa, the casing is not expected to fail under the
applied pressure load and has a factor of safety of 11.9.
Figure 39: Von Mises Stress Distribution on Casing (N/mm2)
The results of the analyses show that with a material of 6061-T6 aluminum and a screw-
plug junction thickness of 0.25 inches, the case is able to handle the pressure load.
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Next, the shaft was also analyzed in Solidworks. For preprocessing, a similar mesh with a
size of 10mm (10714 elements) was used as seen in Figure 40. The base of the screw connected
to the motor was modeled to be fixed. To analyze the shaft, a constant torque of 300 Nm was
applied on the screw as seen in Figure 40 to simulate the motor acting on the shaft. The material
of the shaft was chosen to be AISI 4130 steel to handle the additional stress the screw may
experience. With a shaft outer diameter of 1 inch, the displacement plot and the Von-Mises stress
plot were generated.
Figure 40: Mesh and Torque Loading on Screw
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The displacement plot seen in Figure 41 determined a maximum displacement of 0.122
mm at the free end of the screw, indicating no major deformation overall.
Figure 41: Displacement Distribution on Screw (mm)
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The Von Mises stress plot in Figure 42 indicated a maximum stress of 38.5 MPa at the
connection with the motor. With a maximum yield strength of 460 MPa, the casing is not
expected to statically fail under the torque.
Figure 42: Von Mises Stress Distribution on Screw
A fatigue study was also performed to study the longevity of the screw. Due to the
alternating stresses of the model being below the minimum S-N curve values of AISI 4130 steel,
there is no expected damage from fatigue.
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The mass properties of the final assembly were analyzed and given in Figure 43. The
final mass of the assembly is estimated to be 103 pounds. Because the part is a tabletop design
and largely stationary, the principal axes, moments of inertia, and centers of mass are not of
primary concern.
Figure 43: Assembly Mass Properties
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Figure 44 is a picture of the excel document utilized to calculate the spring displacement
needed in order to apply a specific force in lbs to the end of the screw casing, so that when
material is fed through the exit hole, it experiences a pressure of 50 psi, 30 psi, or 15 psi based
on the exit area. For this application, the team used 15 lbs/in springs at a free length of 2.5
inches.
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Figure 44: Spring Displacement Calculation
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I: Electronic Schematics
Appendix I includes information, images, and relationships between the various sensors
and electrical components used in the system. Figure 49 was updated to show the new load cell
being considered for use in the force-sensitive plate, and Figure 52 was updated to show the new
motor to be used to drive the screw.
A Hall Effect sensor like the one in Figure 45 will be used to record motor position and
motor speed. This data will be used to help calculate the torque put on the screw. A Hall Effect
sensor measures the magnetic field around the sensor and uses that to determine speed and
position. This sensor will be installed near the shaft of the motor to read the rotation position of
the shaft and convert that over time to rpm of the shaft. This, along with the known power
supplied to the motor, will allow torque to be calculated.
Figure 45: Hall Effect Sensor to record motor position/speed
Strain Gauges, seen in Figure 46, will be inserted into the bolts to measure axial force,
strain, and vibration. These sensors will give insight into what is going on regarding the forces
experienced by the bolts. This will be essential data for the researchers. The strain gauges will be
installed on the clamshell bolts as well as the bolts fastening the shell to the base. The installation
of the gauges is as simple as inserting them into the bolt holes and sealing them in the holes with
adhesive. For the FDR, the strain gauges will be upgraded from the LB11 model to the TB21
model. This allows for compatibility with the arduino, allows for higher strain readings, and is
operational in a larger temperature range. The TB21 is a more durable, industrial sensor with
very little added cost.
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Figure 46: TB21 Strain Gauges for Measurements in Screws and Bolts
Figure 47 visualizes how the force within the barrel translates to the forces exerted on the
bolts. As can be seen, the horizontal forces offset each other, leaving only the vertical forces to
affect the bolts. The sensors in the bolts are bonded with a special adhesive to their insides so
that they experience the same forces as the bolts.
Figure 47: Force Diagrams of Pressure in the Screw Barrel and Force Exerted on the Bolts
An Emergency Stop button, in Figure 48, will need to be included in the design for safety
reasons. The E-Stop button will allow the user to shut the motor off should anything go wrong
while operating. A representation of the E-Stop button is seen below in Figure 48. The
emergency stop button will be installed on the base of the feed screw, near the hopper. This is the
most dangerous area for users so it is important to have the E-stop nearby. For the FDR, a
smaller, more inexpensive model of E-stop was chosen to reduce cost and fit more appropriately
on the model.
Figure 48: E-Stop button
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Since the CDR, a decision was made to move from one load cell to four smaller load
cells, one for each spring. This allows larger forces to be measured because each sensor will
ideally experience ¼ of the total load. This allowed the team to use a smaller sensor that was
capable of reading the expected load. The expected load was calculated by using the applied
back pressure from the springs and the plug area. These smaller sensors can give more precise
readings than one large sensor, are less bulky, and cheaper. The new sensor can be seen in Figure
49. The Degraw 50 kg load cell combo kit will be used on the high fidelity prototype. The kit
comes with 4 load cells and amplifiers to make them compatible with the arduino.
Figure 49: Degraw load cell that will be used to measure force on springs
Degraw 50 kg Load Cell with HX711 Amplifier are chosen because it is straightforward
and versatile. Each Degraw load cell shown in Figure 49 can measure up to 50kg. The HX711
amplifier sensor module can be used with 1 or 2 or 4 load cells and measure 50 ~ 100 ~ 200 kg.
Each strain gauge will need one HX711 amplifier and there are 12 strain gauges in total. A set of
4 load cells and 1 HX711 amplifier will be used for the measurement of mass flow while another
set of 1 load cell and 1 HX711 amplifier will be used for the pressure plate load. When using the
load cell, the load cell will need to be mounted on a surface with screws and bolts, so that the
weights/loads/forces exerted on the surface can be measured by the load cell.
The HX711 amplifier module shown in Figure 50 amplifies the voltage difference from
the Degraw load cell and then outputs the value. This value is not necessarily in gram, so it needs
to be calibrated using another Arduino calibration algorithm. Then the calibration value is then
put into the main Arduino code. The HX711 amplifier can receive values from 1 or 2 or 4 load
cells with different circuit wirings, where each load cell can measure up to 50 kg. Therefore, we
use only 1 load cell for the pressure plate measurement to save rooms needed and the measure
limit of 50 kg fits our requirements. On the other hand, we use 4 load cells for the mass flow
measurement to measure up to 200 kg. The HX711 is also used for the TB21 strain gauge sensor
to measure the strain inside of a certain screw. Each strain gauge connects to 1 HX711 amplifier
and 12 strain gauges are in use. Overall, 14 HX711 amplifier modules are used for the pressure
plates, mass flow and strain gauge measurements. Different calibration factors are needed for
different uses and will need to be input by the user to the main code.
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Figure 50: Degraw 50 kg Load Cell with HX711 Amplifier
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Figure 51: HiLetgo ACS712 30A Current Sensor Module 30A Range ACS712 Module
The voltage of the motor power supply shown in Figure 52 is 24 V fixed, which should
be provided from the wall outlet through a transformer. In order to calculate the power
consumption of the motor, the team needs either the current or the resistance of the motor and the
resistance is hard to measure. Therefore, an ACS712 current sensor will be used in series with
the motor to measure the current through the motor and the power can be calculated. The
ACS712 current sensor shown in Figure 26 can measure between positive and negative 20
Amperes, which covers the possible range of the current through motor, being lower than 1.5
Ampere based on the specification sheet. After the power consumption is calculated, a hall effect
sensor is used to measure the rotational speed of the motor in rpm. The current sensor and the
hall effect sensor are selected for easy use with Arduino.
Figure 52: MM 504-11 Low rpm High Torque DC Planetary Reduction Gear Motor 300w 24v
Page 52 of 115
The team selected the BMM504-4 Low rpm High Torque DC Planetary Reduction Gear
Motor 300w 24v reducer motor, seen in Figure 52. The motor provides 4 rpm motor speed and
543.4 N-m torque because at least 500 N-m is required for this motor. This motor provides a
large torque value at the expense of speed, for which the team has little use for. The
potentiometer shown in Figure 54 has 360-degree ticks so the user can adjust the input desired
motor speed very accurately. This motor was updated from the previous design due to the
previous design not meeting the torque and speed requirements set by the researchers. Also a
knob is a better choice because it is more user friendly.
Finally, the L298 H-bridge DC motor driver shown in Figure 53 is used to control the
motor with PWM signal. The two input pins of the motor driver receive digital signals for the
rotational direction of the motor. If either pin is 1 and the other is 0, then the motor will rotate in
one direction. On the other hand, if the pins are flipped, the motor will rotate in other direction.
In addition, the Arduino will input an PWM signal to the enable pin on the motor driver and
easily control the rotational speed of the motor can be easily and effectively controlled. If the
enable pin receives no PWM signal, then the motor will stop abruptly.
Figure 53: L298 Dual H Bridge DC Motor Driver Speed Controller
Page 53 of 115
Figure 54: Cylewet CYT1100 360 Degree Rotary Encoder Code Switch Digital Potentiometer with Push
Button 5 Pins and Knob Cap for Arduino
Page 54 of 115
J: Arduino Code
Appendix J includes the Arduino code. This code defines all variables however does not
yet utilize the real values that will be used in the program. Through it, the shape of the final
program and its functions can be seen.
Figure 55 lays out the full extent of the code, defining variables and functions and
including comments to indicate the purpose of each line. If a certain value needs testing and
calibration by the user before running the main code, the certain values are shown in the default
number of 9999. On the other hand, the connection pin numbers of wires are also expressed with
9999, because they are subject to change and the user can change them easily. For detailed
wiring procedures, please refer to the schematic wiring diagram.
Page 55 of 115
#include "HX711.h"
#define Kp 9999 // experiment to determine this, start by something small
#define Kd 9999 // experiment to determine this, slowly increase the speeds and adjust this value. ( Note: Kp <
Kd)
#define Maxspeed 9999 // the max speed for the motor before it become dangerous, should be slightly higher
than the rpm_max
#define calibration_factor 9999 //This value is obtained using the SparkFun_HX711_Calibration sketch for the
Strain Gauges
#define calibration_factor_PPloadcell 9999 //This value is obtained using the SparkFun_HX711_Calibration
sketch for the Pressure Plate load cell
#define calibration_factor_MFloadcell 9999 //This value is obtained using the SparkFun_HX711_Calibration
sketch for the Mass Flow load cell
#define DOUT01 9999 // The digital data pin number for the strain gauge 01
#define CLK01 9999 // The digital clock pin number for strain gauge 01
#define DOUT02 9999 // The digital data pin number for the strain gauge 02
#define CLK02 9999 // The digital clock pin number for strain gauge 02
#define DOUT03 9999 // The digital data pin number for the strain gauge 03
#define CLK03 9999 // The digital clock pin number for strain gauge 03
#define DOUT04 9999 // The digital data pin number for the strain gauge 04
#define CLK04 9999 // The digital clock pin number for strain gauge 04
#define DOUT05 9999 // The digital data pin number for the strain gauge 05
#define CLK05 9999 // The digital clock pin number for strain gauge 05
#define DOUT06 9999 // The digital data pin number for the strain gauge 06
#define CLK06 9999 // The digital clock pin number for strain gauge 06
#define DOUT07 9999 // The digital data pin number for the strain gauge 07
#define CLK07 9999 // The digital clock pin number for strain gauge 07
#define DOUT08 9999 // The digital data pin number for the strain gauge 08
#define CLK08 9999 // The digital clock pin number for strain gauge 08
#define DOUT09 9999 // The digital data pin number for the strain gauge 09
#define CLK09 9999 // The digital clock pin number for strain gauge 09
#define DOUT10 9999 // The digital data pin number for the strain gauge 10
#define CLK10 9999 // The digital clock pin number for strain gauge 10
Page 56 of 115
#define DOUT11 9999 // The digital data pin number for the strain gauge 11
#define CLK11 9999 // The digital clock pin number for strain gauge 11
#define DOUT12 9999 // The digital data pin number for the strain gauge 12
#define CLK12 9999 // The digital clock pin number for strain gauge 12
#define DOUT_PPloadcell 9999 // The digital data pin number for the Pressure Plate load cell
#define CLK_PPloadcell 9999 // The digital clock pin number for the Pressure Plate load cell
#define DOUT_MFloadcell 9999 // The digital data pin number for the Mass Flow load cell
#define CLK_MFloadcell 9999 // The digital clock pin number for the Mass Flow load cell
HX711 straingauge01;
HX711 straingauge02;
HX711 straingauge03;
HX711 straingauge04;
HX711 straingauge05;
HX711 straingauge06;
HX711 straingauge07;
HX711 straingauge08;
HX711 straingauge09;
HX711 straingauge10;
HX711 straingauge11;
HX711 straingauge12;
HX711 PPloadcell;
HX711 MFloadcell;
// Constant pin numbers on the Arduino which are connected to the electronic devices
const int Motorpin1 = 9999;
const int Motorpin2 = 9999;
const int ENA = 9999;
const int rpmpin = 9999;
const int currentpin = 9999;
const int EStoppin = 9999; // the pin number of the Emergency Stop button pin
const int potentiometer_pin = 9999; // the pin number of the potentiometer knob
Page 57 of 115
// Constant values for safety measures and the supply voltage of the motor
const int power_limit = 9999;
const int torque_limit = 9999;
const int voltage = 9999; // Fixed value from the power source and motor itself
const int rpm_max = 9999; // Fixed value from the motor itself
// Initialization
int EStopState = 0; // variable for reading the EStoppin status
int rpm_desired = 0;
int rpm = 0;
int current = 0;
int potentiometer_val = 0;
int power = 0;
int torque = 0;
int lastError = 0;
int error = 0;
int motorSpeedCorrection = 0;
int Motorspeed = 0;
// Data arrangement variables for data streaming to excel
const byte kNumberOfChannelsFromExcel = 6;
const char kDelimiter = ',';
const int kSerialInterval = 50;
unsigned long serialPreviousTime;
char* arr[kNumberOfChannelsFromExcel];
Page 58 of 115
void setup() {
Serial.begin(115200);
Serial.println("Basic Encoder Test:");
pinMode(rpmpin, INPUT);
pinMode(currentpin, INPUT);
pinMode(Motorpin1, OUTPUT);
pinMode(Motorpin2, OUTPUT);
pinMode(ENA, OUTPUT);
pinMode(EStoppin, INPUT);
straingauge01.begin(DOUT01, CLK01);
straingauge02.begin(DOUT02, CLK02);
straingauge03.begin(DOUT03, CLK03);
straingauge04.begin(DOUT04, CLK04);
straingauge05.begin(DOUT05, CLK05);
straingauge06.begin(DOUT06, CLK06);
straingauge07.begin(DOUT07, CLK07);
straingauge08.begin(DOUT08, CLK08);
straingauge09.begin(DOUT09, CLK09);
straingauge10.begin(DOUT10, CLK10);
straingauge11.begin(DOUT11, CLK11);
straingauge12.begin(DOUT12, CLK12);
PPloadcell.begin(DOUT_PPloadcell, CLK_PPloadcell);
MFloadcell.begin(DOUT_MFloadcell, CLK_MFloadcell);
straingauge01.set_scale(calibration_factor); //This value is obtained by using the
SparkFun_HX711_Calibration sketch for the Strain Gauges
straingauge02.set_scale(calibration_factor); //This value is obtained by using the
SparkFun_HX711_Calibration sketch for the Strain Gauges
straingauge03.set_scale(calibration_factor); //This value is obtained by using the
SparkFun_HX711_Calibration sketch for the Strain Gauges
straingauge04.set_scale(calibration_factor); //This value is obtained by using the
SparkFun_HX711_Calibration sketch for the Strain Gauges
straingauge05.set_scale(calibration_factor); //This value is obtained by using the
SparkFun_HX711_Calibration sketch for the Strain Gauges
straingauge06.set_scale(calibration_factor); //This value is obtained by using the
SparkFun_HX711_Calibration sketch for the Strain Gauges
straingauge07.set_scale(calibration_factor); //This value is obtained by using the
SparkFun_HX711_Calibration sketch for the Strain Gauges
straingauge08.set_scale(calibration_factor); //This value is obtained by using the
SparkFun_HX711_Calibration sketch for the Strain Gauges
straingauge09.set_scale(calibration_factor); //This value is obtained by using the
SparkFun_HX711_Calibration sketch for the Strain Gauges
Page 59 of 115
straingauge10.set_scale(calibration_factor); //This value is obtained by using the
SparkFun_HX711_Calibration sketch for the Strain Gauges
straingauge11.set_scale(calibration_factor); //This value is obtained by using the
SparkFun_HX711_Calibration sketch for the Strain Gauges
straingauge12.set_scale(calibration_factor); //This value is obtained by using the
SparkFun_HX711_Calibration sketch for the Strain Gauges
PPloadcell.set_scale(calibration_factor_PPloadcell); //This value is obtained by using the
SparkFun_HX711_Calibration sketch for the Pressure Plate load cell
MFloadcell.set_scale(calibration_factor_MFloadcell); //This value is obtained by using the
SparkFun_HX711_Calibration sketch for the Mass Flow load cell
straingauge01.tare(); //Assuming there is no weight on the scale at start up, reset the scale to 0
straingauge02.tare(); //Assuming there is no weight on the scale at start up, reset the scale to 0
straingauge03.tare(); //Assuming there is no weight on the scale at start up, reset the scale to 0
straingauge04.tare(); //Assuming there is no weight on the scale at start up, reset the scale to 0
straingauge05.tare(); //Assuming there is no weight on the scale at start up, reset the scale to 0
straingauge06.tare(); //Assuming there is no weight on the scale at start up, reset the scale to 0
straingauge07.tare(); //Assuming there is no weight on the scale at start up, reset the scale to 0
straingauge08.tare(); //Assuming there is no weight on the scale at start up, reset the scale to 0
straingauge09.tare(); //Assuming there is no weight on the scale at start up, reset the scale to 0
straingauge10.tare(); //Assuming there is no weight on the scale at start up, reset the scale to 0
straingauge11.tare(); //Assuming there is no weight on the scale at start up, reset the scale to 0
straingauge12.tare(); //Assuming there is no weight on the scale at start up, reset the scale to 0
PPloadcell.tare(); //Assuming there is no weight on the scale at start up, reset the scale to 0
MFloadcell.tare(); //Assuming there is no weight on the scale at start up, reset the scale to 0
delay(5000);
}
Page 60 of 115
void loop() {
EStopState = digitalRead(EStoppin);
rpm = analogRead(rpmpin); // Get the motor speed (rpm) from the hall effect sensor
current = analogRead(currentpin); // Get current through the motor from the current sensor
potentiometer_val = analogRead(potentiometer_pin); // reads the value of the potentiometer (value
between 0 and 1023)
rpm_desired = map(potentiometer_val, 0, 1023, 0, rpm_max); // scale it to use it as the desired rpm (value
between 0 and rpm_max)
power = current * voltage; // With the provided Voltage and Current of the motor, P = IV
torque = power / rpm;
lastError = 0;
error = rpm_desired - rpm;
motorSpeedCorrection = Kp * error + Kd * (error - lastError);
Motorspeed = rpm_desired + motorSpeedCorrection;
if(power > power_limit || torque > torque_limit){
Motor_Brake();
printf("Power or Torque value exceeds the limit value!!!\n");
}else if(EStopState == HIGH){
Motor_Brake();
printf("The Emergency Stop is pressed!!!\n");
}else{
Motor_Forward(Motorspeed);
}
if(Motorspeed > Maxspeed){
Motorspeed = Maxspeed; // prevent the motor from going beyond max speed
}
processIncomingSerial(); // Read Excel variables from serial port (Data Streamer)
processOutgoingSerial(); // Process and send data to Excel via serial port (Data Streamer)
lastError = error;
}
Page 61 of 115
void Motor_Forward(int MotorSpeed)
{
digitalWrite(Motorpin1, HIGH);
digitalWrite(Motorpin2, LOW);
analogWrite(ENA, MotorSpeed / rpm_max); // the PWM signal output to the Enable pin on L298 should be a
percentage
}
// Brake the motor
void Motor_Brake()
{
digitalWrite(Motorpin1, LOW);
digitalWrite(Motorpin2, LOW);
}
// OUTGOING SERIAL DATA PROCESSING CODE----------------------------------------
void processOutgoingSerial()
{
// Enter into this only when serial interval has elapsed
if((millis() - serialPreviousTime) > kSerialInterval)
{
// Reset serial interval timestamp
serialPreviousTime = millis();
Serial.print(EStopState);
Serial.print(kDelimiter);
Serial.print(rpm_desired);
Serial.print(kDelimiter);
Serial.print(rpm);
Serial.print(kDelimiter);
Serial.print(Motorspeed);
Serial.print(kDelimiter);
Serial.print(current);
Serial.print(kDelimiter);
Serial.print(power);
Serial.print(kDelimiter);
Page 62 of 115
Figure 55: Code to control Arduino
// INCOMING SERIAL DATA PROCESSING CODE----------------------------------------
void processIncomingSerial()
{
if(Serial.available()){
parseData(GetSerialData());
}
}
// Gathers bytes from serial port to build inputString
char* GetSerialData()
{
static char inputString[64]; // Create a char array to store incoming data
memset(inputString, 0, sizeof(inputString)); // Clear the memory from a pervious reading
while (Serial.available()){
Serial.readBytesUntil('\n', inputString, 64); //Read every byte in Serial buffer until line end or 64 bytes
}
return inputString;
}
// Seperate the data at each delimeter
void parseData(char data[])
{
char *token = strtok(data, ","); // Find the first delimeter and return the token before it
int index = 0; // Index to track storage in the array
while (token != NULL){ // Char* strings terminate w/ a Null character. We'll keep running the command until
we hit it
arr[index] = token; // Assign the token to an array
token = strtok(NULL, ","); // Conintue to the next delimeter
index++; // incremenet index to store next value
}
}
Page 63 of 115
K: Flow Chart of Control/Operation
Appendix K includes diagrams of the code in block format to see the relationship
between processes as well as the diagrams of the electrical connections.
As can be seen in the flowchart of Figure 56, the team will take input from the user for
the desired motor rotational speed in rpm. The error will be calculated by subtracting the actual
rotational speed measured by the hall effect sensor from the input desired speed. The error and a
PD controller are then used to adjust the PWM signal to keep the actual rotational speed as close
as possible to the desired speed.
Figure 56: Flowchart of Control for the motor control device
Figure 57 shows the final schematic wiring diagram corresponding to the Arduino code
and the flowchart. Wires such as ground and power are color-coded black and red respectively in
accordance with general wiring diagram practices. All pin numbers in a certain type are all
exchangeable. Only do not mix up the digital pins, analog pins and PWM pins with each other.
Page 64 of 115
Figure 57: Final schematic wiring diagram for the motor control device
As shown in Figure 57, the enable pin of the L298 motor controller is connected to the
PWM pin of the Arduino. On the other hand, the two input pins controlling the direction of the
motor of the L298 motor controller as well as the input of the emergency push button are
connected to the digital pins of the Arduino. A digital pin on Arduino will keep tracking the
emergency stop button, which is 1 if pressed and 0 if not pressed. Once the emergency button is
pressed, Arduino will send OFF value to the 2 digital pins on the motor driver and set the motor
speed to zero. Finally the power pins of the L298 motor driver will be connected to an external
12V power supply and a transformer might be needed depending on different situations.
The ACS712 current sensor will measure the current value through the motor and
Arduino can calculate the power consumption of the motor with the current value and the voltage
value of the motor. Next, the torque provided by the motor is calculated by the motor power in
watts and the motor speed in rpm. In addition to the emergency stop button, once the power or
the torque exceeds their corresponding limit values, the motor will be shut down with the same
method as well.
An analog pin on Arduino will keep taking the desired motor speed value from the user
through the potentiometer with a knob. Then the hall effect sensor will measure the actual motor
speed in rpm and send the value back to Arduino through an analog pin. The error, which is the
desired value subtracted by the actual value, will be used for a PD controller. The PD controller
will transmit a certain percentage of PWM signal to the L298 motor driver Enable pin to control
the motor speed and keep it as close to the desired speed. Therefore, the user should be able to
easily control the motor speed with the potentiometer knob outside of the machine without
changing and re-running the Arduino code.
Page 65 of 115
HX711 will measure and sum up all reading values from all load cells and use 2 digital
pins (DOUT and CLK) on Arduino. If the HX711 amplifier uses 4 load cells, measurement of
the mass flow rate for example, the 4 load cells will form a Wheatstone bridge. The Wheatstone
bridge circuit has 2 compression and tension resistors pairs. Once any of the 4 sensors are
pressed, the compression and tension resistor will change their resistance value in opposite
directions. Then the voltage readings at the two points will be slightly different, the voltage
difference is very small but can be measured, amplified and calibrated by the HX711 sensor
amplifier module to the weight or load for our purpose. Arduino will receive a value and convert
this value to our sensor value with its corresponding calibration factor, which would be acquired
before running the main code.
First, the user needs to input the HX711 library into Arduino. The library file “HX711-
master.zip” has been included in our submission and can also be found in the github link
provided in the Appendix of Purchase links. Then the user needs to run the Arduino code
“HX711_Calibration” to determine the calibration factor needed for each use of the HX711
modifier, which means the HX711 modules used with strain gauges, pressure plate and mass
flow need different calibration factors, based on their various units and approaches. When using
the calibration code, the user needs to put certain known weight on the sensor, and check if the
sensor reading is the same as the real known weight. The user can also adjust the calibration
factor by pressing “+” or “-” to increase or decrease the calibration factor. The adjusted final
calibration factors for different uses of HX711 are then substituted into the main code,
respectively.
If the HX711 only uses one load cell, then two 1000 Ohm resistors are required to form a
Wheatstone bridge circuit similar to the case of 4 load cells. For example, the measurement of
the pressure plate load only needs one load cell because the maximum reading of one load cell
(50kg) fits our requirements and saves some room for us. Also, each TB21 strain gauge needs
one HX711 amplifier, so 12 TB21 strain gauges need 12 HX711 amplifiers, with the same
structure of circuits. Therefore, as shown in the schematics on the top left, only one set of 1
TB21 strain gauge and 1 HX711 amplifier is shown within the blue dash line, in order to keep
the schematic organized and avoid redundancy.
The Arduino will collect all the sensor reading, including all calculated values and the
output motor speed to an Excel data sheet, instead of outputting to its serial monitor. Each
channel corresponds to a value output from the Arduino, separated by a delimiter (comma).
Totally 21 data values are to be exported from Arduino to the excel file, so there will be 21
channels. The line graphs of corresponding values are shown to the right of the data tables. An
instructional video for the feature of Arduino data streaming to Excel has been provided. The
data streaming feature in Excel is an add-in for full versions only and it needs to be enabled
through File > Options > Add-ins > Manage: Com Add-ins > Microsoft Data Streamer for Excel.
The Office 365 version provided by Purdue University has this add-in while free versions might
not have this add-in. The user will have to upload the code to Arduino Mega again after plugging
it in and then collect the data with Excel directly, without turning on the serial monitor in
Page 66 of 115
Arduino. The duration of the data history shown in the excel and the sampling frequency can be
changed in the Settings tab in the Excel file.
Page 67 of 115
L: Manufacturing Drawings
Appendix L contains the manufacturing drawings produced over the course of the
project, including assembly drawings, general part drawings, and purchased and modified part
drawings. The manufacturing drawings span pages 67 to 84.
The parts can be found in the following order:
1. Assembly …………………………………………………………………………..68
2. Frame components ……...…………………………………………………….……..70
3. Screw Casing …………………………………………………………….………….....79
4. Screw ……………………………………………………………..……….…………...82
5. Pressure Plate ……………………………………………………………….………….83
6. Purchased and Modified Parts ……………………………………….………….85
Page 68 of 115
Page 69 of 115
Page 70 of 115
7.11
R1.73
.50
6.61
.10
4.07
.25 x4
3.31
3.56 .25
.50
1.00
1.50
1.25 Dimensions symmetric across centerline
A A
B B
4
4
3
3
2
2
1
1
6061-T6 ALUMINUM
FEED SCREW SPEED CREW
1DO NOT SCALE DRAWING
Motor Back Frame
SHEET 1 OF 1
RW 08-03-2020
RW 08-03-2020
UNLESS OTHERWISE SPECIFIED:
Scale: 2:3 WEIGHT:
REVDWG. NO.
BSIZE
TITLE:
NAME DATE
COMMENTS:
CHECKED
DRAWN
125 µin FINISH
MATERIAL
DIMENSIONS ARE IN INCHES
TOLERANCES:
X.XXX±0.005
PROPRIETARY AND CONFIDENTIAL
THE INFORMATION CONTAINED IN THIS
DRAWING IS THE SOLE PROPERTY OF
THE FEED SCREW SPEED CREW. ANY
REPRODUCTION IN PART OR AS A WHOLE
WITHOUT THE WRITTEN PERMISSION OF
THE FEED SCREW SPEED CREW IS
PROHIBITED.
Page 71 of 115
7.110
R1.575
0.500 6.610
0.131
4.073
3.500
4.000
0.250
0.500
3.305
3.555
0.250 x4
Dimensions symmetric across centerline
A A
B B
4
4
3
3
2
2
1
1
6061-T6 ALUMINUM
FEED SCREW SPEED CREW
1DO NOT SCALE DRAWING
Mid Motor Frame
SHEET 1 OF 1
RW 08-03-2020
RW 08-03-2020
UNLESS OTHERWISE SPECIFIED:
SCALE: 3:4 WEIGHT:
REVDWG. NO.
BSIZE
TITLE:
NAME DATE
COMMENTS:
CHECKED
DRAWN
125 µinFINISH
MATERIAL
DIMENSIONS ARE IN INCHES
TOLERANCES:
X.XXX±0.005
PROPRIETARY AND CONFIDENTIAL
THE INFORMATION CONTAINED IN THIS
DRAWING IS THE SOLE PROPERTY OF
THE FEED SCREW SPEED CREW. ANY
REPRODUCTION IN PART OR AS A WHOLE
WITHOUT THE WRITTEN PERMISSION OF
THE FEED SCREW SPEED CREW IS
PROHIBITED.
Page 72 of 115
R1.000 R1.500
0.615
6.495
7.110
2.055
2.555
4.555
5.055
4.100
0.100
5.100
0.250 x2
3.247
3.555
0.250
0.500
0.750
Dimensions symmetric across centerline
A A
B B
4
4
3
3
2
2
1
1
6061-T6 ALUMINUM
FEED SCREW SPEED CREW
1DO NOT SCALE DRAWING
Hopper Frame Back
SHEET 1 OF 1
RW 08-03-2020
RW 08-03-2020
UNLESS OTHERWISE SPECIFIED:
SCALE: 2:3 WEIGHT:
REVDWG. NO.
BSIZE
TITLE:
NAME DATE
COMMENTS:
CHECKED
DRAWN
125 µinFINISH
MATERIAL
DIMENSIONS ARE IN INCHES
TOLERANCES:
X.XXX±0.005
PROPRIETARY AND CONFIDENTIAL
THE INFORMATION CONTAINED IN THIS
DRAWING IS THE SOLE PROPERTY OF
THE FEED SCREW SPEED CREW. ANY
REPRODUCTION IN PART OR AS A WHOLE
WITHOUT THE WRITTEN PERMISSION OF
THE FEED SCREW SPEED CREW IS
PROHIBITED.
Page 73 of 115
.62
6.49
7.11
.250 x2
R1.50
3.35
.10
4.10
R1.78
0°
45° 135°
3.25
3.56
.250 x2
.25 .50
A A
B B
4
4
3
3
2
2
1
1
6061-T6 ALUMINUM
FEED SCREW SPEED CREW
1DO NOT SCALE DRAWING
Hopper FrameSHEET 1 OF 1
RW 08-03-2020
RW 08-03-2020
UNLESS OTHERWISE SPECIFIED:
SCALE: 1:1 WEIGHT:
REVDWG. NO.
BSIZE
TITLE:
NAME DATE
COMMENTS:
CHECKED
DRAWN
125 µinFINISH
MATERIAL
DIMENSIONS ARE IN INCHES
TOLERANCES:
X.XXX±0.005
PROPRIETARY AND CONFIDENTIAL
THE INFORMATION CONTAINED IN THIS
DRAWING IS THE SOLE PROPERTY OF
THE FEED SCREW SPEED CREW. ANY
REPRODUCTION IN PART OR AS A WHOLE
WITHOUT THE WRITTEN PERMISSION OF
THE FEED SCREW SPEED CREW IS
PROHIBITED.
Page 74 of 115
.62
6.49
7.11
R1.50
.25 x2
.10
3.35
.75
0°
45° 135°
R1.76
3.56
.25
3.25
.25 x2
.50 View is symmetrical about centerline
A A
B B
4
4
3
3
2
2
1
1
6061-T6 ALUMINUM
FEED SCREW SPEED CREW
1DO NOT SCALE DRAWING
Big Plug Frame
SHEET 1 OF 1
RW 08-03-2020
RW 08-03-2020
UNLESS OTHERWISE SPECIFIED:
SCALE: 1:1 WEIGHT:
REVDWG. NO.
BSIZE
TITLE:
NAME DATE
COMMENTS:
CHECKED
DRAWN
125 µinFINISH
MATERIAL
DIMENSIONS ARE IN INCHES
TOLERANCES:
X.XXX±0.005
PROPRIETARY AND CONFIDENTIAL
THE INFORMATION CONTAINED IN THIS
DRAWING IS THE SOLE PROPERTY OF
THE FEED SCREW SPEED CREW. ANY
REPRODUCTION IN PART OR AS A WHOLE
WITHOUT THE WRITTEN PERMISSION OF
THE FEED SCREW SPEED CREW IS
PROHIBITED.
Page 75 of 115
7.11
.62 6.49
R.13 x2
R1.00
3.22
4.10
.10
3.25
3.56
.50 .25
.25 x2
.88
3.25
Dimensions are symmetric across centerline
A A
B B
4
4
3
3
2
2
1
1
6061-T6 ALUMINUM
FEED SCREW SPEED CREW
1DO NOT SCALE DRAWING
Small Plug FrameSHEET 1 OF 1
RW 08-03-2020
RW 08-03-2020
UNLESS OTHERWISE SPECIFIED:
SCALE: 1:1 WEIGHT:
REVDWG. NO.
BSIZE
TITLE:
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PROPRIETARY AND CONFIDENTIAL
THE INFORMATION CONTAINED IN THIS
DRAWING IS THE SOLE PROPERTY OF
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.50
2.00
2.00
1.79
2.22
.50
.50
.50
.13
.19
.44
.87
.86
6.29
9.79
1.79
2.22
.24 x30
16.31 11.61 1.25 12.87 9.41
1.06 5.30 .70 4.31 .70 3.40 1.06 3.50 5.25 1.01
52.01
3.28
3.31
3.30 3.25
3.31
4.75 3.56
2.70
.25 x20
1. Unless otherwise specified, dimensions are symmetric across the centerlines in both views
NOTES:
2. Every grouping of five holes in the enlarged view maintains the same relative location to each other. The leftmost and bottommost holes have been located in each group to apply the relative locations. This view is an enlarged section (1:1 scale) of the top view
A A
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C C
D D
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4.00
.30 1.00
3.15
6.85
3.68
5.00
.33 1.95
2.50
3.16
.50 x2
.72
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B B
C C
D D
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.74
A A
B B
C C
D D
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4.00
2.50
1.00
.25 x4
0°
45° 135°
225° 315°
1.25
.25
2.75
3.00
3.90
4.00
1.50
1.25
2.00
2.50
3.00
Dimensions symmetric across centerline
A A
B B
4
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Hopper
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Page 80 of 115
R.750
R.988
R1.263
R2.000
.250 x2
0°
45° 135°
R1.735
4.760
2.853°
47.853°
.250
3.910
.550
1.992
1.989
.986
.986
.250 x4
2.000
2.000
2.489
.100
1.000
4.010
4.910
5.010
R1.500
Dimensions are symmetrical across centerline
A A
B B
4
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Page 81 of 115
.250 x4
R2.000 R1.500
R.625
2.498
0°
45° 135°
R1.749 R1.249
.250 x4 45° .125
1.500
1.250
1.497
1.998
.100
1.000
5.000
5.900
6.000
.077
Dimensions are symmetric across centerline
A A
B B
4
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3
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PlugSHEET 1 OF 1
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.999 .848
8.740
14.500
20.125
.75°
1.000 4° .633
.380
A A
B B
4
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3
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2
2
1
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STEEL 4130
FEED SCREW SPEED CREW
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Page 83 of 115
3.00
3.00
.25 x4
1.50
1.50
2.50 0°
44.82° 134.82°
224.82° 314.82°
.50
60°
2.23
.50
.56
A A
B B
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.250 x4
9.500
9.500 .063
A A
B B
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.079 .453
Note: Bolt purchased from McMaster Carr
A A
B B
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YELLOW CHROMATE-PLATED ZINC
FEED SCREW SPEED CREW
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Page 86 of 115
M: What was Learned from the Low, Mid, and High-Fidelity Prototypes
Appendix M includes the insights gained from the design process of each stage as labeled
below. Lessons learned from the CDR have been included towards the bottom of this section.
Low-Fidelity Prototype:
From the low fidelity prototype the team learned that it must ensure modularity of parts,
proper sensor placement, and simple supports. While designing the modularity of the barrel, the
team learned it had to either maintain a constant outside diameter across all modular parts or
ensure the base structure was able to adjust to components of varying diameters.
Further insights gathered from the low-fidelity prototype were possible locations for
sensor placement. This forced each section to be considered separately in the design process.
For example, the motor and its connection were isolated and determined to be the best fit for a
hall effect sensor that will track the rotation of the shaft. Flanges were added to allow the barrel
to open and to provide locations for strain gauges to measure the stresses of the structure. A scale
was added to capture fed material to determine mass flow rate out, and the back pressure plate
was designed to incorporate a pressure sensor to allow the simulated pressure to be measured and
adjusted.
The final insights were in relation to the support structure. There were several designs
considered, but ultimately, the team learned it was simplest from a manufacturing and design
perspective to create a set of simple supports to elevate the screw system and connect it to the
baseplate.
Mid-fidelity Prototype:
The mid-fidelity prototype allowed the thicknesses of parts and tolerances in connection
areas to be validated. For example, the shaft was determined to be an R4 fit due to the pressures
experienced by that section of the shaft. For the bolts, an LC3 fit was determined to be proper
due to the tighter tolerances. This will prevent the internal casing from shifting and interfering
with the screw. The mid-fidelity prototype also required a deeper analysis of sensor locations.
The E-stop was placed on a panel for easy reach. The force plate and scale had to be designed to
not interfere with each other as they occupy a similar space. The force plate required a thicker,
reinforced section of the stand in order to provide support for the desired pressures.
FEA analysis was performed on the inside of the casing and was able to verify the
thickness was correct. The shaft was analyzed using a simple mathematical model and the
material properties and factors of safety were found to be much higher than desired. This allowed
a smaller design to be considered, however the current system was still viable within the
specified design parameters, so the design was not changed.
High-Fidelity Prototype:
When completing the high-fidelity prototype, the team updated and improved the back
pressure plate. A concern was raised about the springs being compressed by the material exiting
the plug and not falling into the collection bin. To combat this, the back pressure plate was
Page 87 of 115
changed to a conical shape without the tip. The center of the plate would be a flat circle the same
size as the screw. The angled sides interacting with the material will push the material radially
outwards, forcing it to fall into the bin. This will decrease the fluctuation of back pressure by
reducing the length fluctuation of the spring.
Another lesson learned regarding the back pressure plate was the need for additional
support to the wall supporting the springs (pushing the plate into the plug of the screw). To
overcome this, 2 L-brackets were added to the back of the plate. These L-brackets also make it
easier to move the support plate forward and backward to adjust the back pressure.
To create a prototype that is easier to work with, the inner diameter was scaled down
from 2” to 1.5” and 1.25” (2 test cases). This will allow testing to be done on a table top and
keep the device from getting too heavy. It will also cut costs. Since this device will only be used
for testing purposes, rather than full-scale production, a size-reduction made sense in every
aspect.
After discussing pros and cons of balancing rpm and torque in a motor, the team decided
it was best to sacrifice some speed for extra torque. This is because when testing, it will be more
important that the motor is able to push the material out when up against the back pressure, than
how fast the motor is able to turn. It was impossible to find a motor that fit the size requirement,
5+ rpm, and 500+ Nm torque. The team decided on a 24V DC Motor Low Rpm High Torque DC
Planetary Reduction Gear Motor that could spin at 4 rpm and had 543.4 Nm torque. This motor
has slightly under 5 rpm and is able to exceed the 500 Nm torque requirement. The team was
much more comfortable sacrificing speed for torque to reduce jamming of the material inside the
casing in a case where the motor would not be strong enough to push the material out, one of the
researchers’ main concerns.
Page 88 of 115
N: Benchmark research
Appendix N contains information relating to similar designs to the desired feed screw
that already exist. This includes multiple Figures that highlight different aspects of the
benchmarks.
The Screw and Barrel System by Dynisco
The price of this benchmark is not provided on their website. This design seems to
be very comprehensive and expensive, which goes against the requirement of keeping the
table-top feed screw inexpensive. Because our design only uses milled or pelleted biomass
into chemical reactor vessels, the feed screw can be simplified and focused to keep costs
low.
One of the existing benchmark solutions is The Screw and Barrel System by
Dynisco. Figure 58 shows the components of this screw and barrel system design. The
screw consists of three different sections: the feed zone, transition zone and metering zone.
The compression ratio, which is the ratio of the volume of the flight in the feed zone to the
volume of the flight in the metering zone, is 3:1 for their design. This design also provides
a variety of different screw types according to each material or process, such as the
extrusion screw shown in Figure 59. They also provide multiple methods to achieve screw
mixing in order to deliver the material at a constant and controllable rate. Figure 60 and
Figure 61 show the dispersive mixing and distributive mixing, respectively. The static
mixer in Figure 62 is the device to perform the mixing methods. The screen packs, with the
support of breaker plates, build up pressure in a machine to uniformly heat, melt, and mix
the material, as shown in Figure 63. Both AC and DC motors could be used in their design.
The price of this benchmark is not provided on their website. This design seems to
be very comprehensive and expensive, which goes against the requirement of keeping the
table-top feed screw inexpensive. Because our design only uses milled or pelleted biomass
into chemical reactor vessels, the feed screw can be simplified and focused to keep costs
low.
Figure 58: The Basic Extrusion Screw Design
Page 89 of 115
Figure 59: Elements of an Extrusion Screw
Figure 60: Dispersive Mixing
Figure 61: Distributive Mixing
Figure 62: Static Mixer
Page 90 of 115
Figure 63: Breaker Plate and Screen Pack
Page 91 of 115
O: Basic Physics Model (Free Body Diagram)
Appendix O contains free body diagrams and force analysis of different aspects of the
screw. Additional analysis from the FDR has been appended to the end.
The main forces concerning this project will be torque applied by the motor, pressure
from the back-pressure plate, and normal force by the tapered walls. The torque can be
calculated, utilizing a volt sensor attached to the motor, and an RPM sensor we plan to have
attached to the driveshaft. The back-plate pressure will be measured utilizing the force sensing
plate itself. Finally, the normal force on the tapered walls can be found using strain gauges
attached to the flanges holding the tapered, clamshell section together. These forces are shown
below in Figure 64.
Figure 64: Force Identification upon Powdered Microcrystalline Cellulose
Page 92 of 115
In Figure 65, to estimate the bending moment, the end of the shaft connected to the motor
was simulated as being fixed to the wall, disallowing rotation. The weight of the shaft was
calculated using the density of Aluminum 6061 (2.7 g/cm^3) and the volume of the shaft. This
then showed the shear forces and bending moment the shaft would experience at any point in its
operation due to the force of gravity. This estimation was used in the subsequent calculations as
the bending moment experienced by the shaft.
Figure 65: Force diagram of shaft
Page 93 of 115
Figure 66 calculates the factor of safety of the shaft in operation. Using the maximum
specified torque and the bending moment found in Figure 65 above, the factor of safety was
found to be 9.14 for normal operation and 8.184 for the possibility of a static failure in the first
load. The first factor of safety was calculated using the Goodman criteria because it is an
extremely conservative estimate. This should ensure a safe design. Both factors of safety are well
above the minimum factor of safety of 2, indicating this is a good design that could theoretically
be adjusted to reduce the factor of safety, thereby reducing space and cost of the system.
Figure 66: Factor of safety during operation of shaft
Page 94 of 115
Figure 67 calculates the minimum possible diameter for the desired factor of safety of 2
for the operation of the shaft. It uses the Goodman criteria to remain consistent with other
calculations of the factor of safety. Using this, it was found that the minimum acceptable
diameter to retain a factor of safety of 2 was 1.537 inches.
Figure 67: Minimum possible diameter calculations
Page 95 of 115
Figure 68 estimates the factor of safety in an instance where the material flowing through
the feeder compacts and the motor stalls. In this event, the weight of the shaft is supported on
both ends by the compacted material and the motor, so it experiences pure torsion. It used the
factor of safety of yielding to check for yielding. The factor of safety was found to be 8.203,
comparable to the value found previously for shaft operation. The equation was then rearranged
to solve for the minimum diameter of the shaft, which was found to be 1.829 inches. This
confirms that the current shaft design is within the desired factors of safety and can withstand the
forces experienced when the material plugs the feeder.
Figure 68: Factor of safety and minimum acceptable diameter during stall
Page 96 of 115
P: Standards Referenced/Used/Applied
Appendix P has been included to show the standards identified and used in the design of
the screw and casing. They are used to determine the tolerances needed for each mating section
of the system shown in Appendix Q.
The first reference used below in Figure 69 is the American National Standard Running
and Sliding Fits ANSI B4.1-1967 (R2004). This table aided in the creation of the table of fits and
tolerances, seen in Appendix Q. The table was located at the following link:
http://www.zpag.net/Usinage/standard_ansiB4_1_1967.htm. This link also contained tables for
LC fittings which were utilized for analysis of bolt hole tolerances.
Figure 69: American National Standard Running and Sliding Fits ANSI B4.1-1967 (R2004)
The following drawing in Figure 70 is a reference provided in class by Dr. Jensen. This
example part drawing helped the team formulate part drawings in preparation for FDR.
Page 97 of 115
Figure 70: Example Part Drawing
Page 98 of 115
Q: Testing and Validation
Pre-Fabrication Electronic Testing (Completed by Team)
Test 1: Arduino Coding:
To ensure the start button is able to begin operating the feed screw, the Arduino program
should be able to simulate rotating the screw, collecting speed, torque, pressure, mass flow rate,
clamshell and flange bolt strain, and begin accepting speed adjustment input by the RPM Knob.
Since the Hall Effect Sensor, Pressure Sensor, Mass Flow Scale, Current Sensor, and Strain
Gauges will not be providing any readings with this test, they may be temporarily replaced with
constants to be read for validation. This can be tested by:
● Apply constant test values temporarily replacing the readings from:
○ Hall Effect RPM Sensor
○ Load Cell (Pressure Plate)
○ Mass Flow Scale
○ Current Sensor
○ Each Strain Gauge
○ RPM Knob
● Apply “Print” functions to display the following information:
○ Print “The Screw ___(insert is or is not) rotating at ___(insert Hall Effect Sensor
Reading) RPM due to an input of ___(insert RPM Knob Reading) RPM with a
torque of ___(insert calculated Torque value) Nm. The Pressure Plate is exerting
___(insert calculated Pressure value from Load Cell) psi on material exiting the
feed screw at ___(insert calculated Mass Flow Rate) g/s. The Strain Gauges are
reading as follows: 1:___(1) 2:___(2) 3:
● Run the Arduino Code
● Activate the Start Button with a virtual positive
● Test Successful if all input values are reflected in the printed statement and update the
Data IN excel file and associated graphs
Completed? - YES
Test 2: Motion Tests of the Screw Turning and Pressure Plate Moving:
To ensure there are no instances of interference within the device during the turning of
the feed screw or the slight displacement of the pressure plate plug, videos were created
simulating the motion, and can be found within the FDR Presentation provided. The videos show
that in each case, motion causes no interference, and the physical prototype will be able to move
in a similar manner.
Completed? - YES
Test 3: Finite Element Analysis Results:
After putting both the outer casing and feed screw made of Aluminum 6061 and Steel
4130 respectively, through maximum stress analysis, as seen in detail in Appendix H, all factors
Page 99 of 115
of safety reach far above the team’s goal of 2. This shows that if put together correctly, the
device will not fail under static conditions. Due to the high fatigue strength of each of these
materials, the team can guarantee that the device will last a minimum of 5 years of 40 hour per
week operation.
Completed? - YES
Post-Fabrication Electronic and Mechanical Testing (Completed by Researchers)
Test 4: Service Checks on all means of Operation:
Before feeding material into the fabricated device, the user should attempt to run the
device without any material within. The following operations should work seamlessly before
feeding the microcrystalline cellulose:
● The screw turns when and only when the start button has been activated via the
controlling laptop/computer
● The screw stops turning when and only when the start button has been deactivated OR
the E-Stop has been engaged
● The Hall-Effect Sensor reading correctly reflects the input speed determined by the
position of the 10-click potentiometer
● The Pressure Plate pressure is correctly reflected by the load cell located on the supported
9.5 in. by 9.5 in. plate
○ This load cell should read nothing more than 50 lbs of force, otherwise material
may not be able to be pushed out, causing a blockage
● The protective mesh is in place and prevents any limbs from entering the turning feed
screw
● The strain gauges are able to see small readings from small pushes executed by the
operator
● The collection bin underneath the feed screw exit is in place and on top of the mass flow
reading load cells
Completed? - NO
Conclusions-
Once all of these tests have been successfully completed, the device will be ready to serve its
original purpose, and provide data based validation of existing predictive models to improve
industrial feed screws. It will be very cost effective when compared to the alternative $10,000
per run existing feed screw being used by the clients. The data it provides will also help in the
formation of new models, saving biorefineries up to $1,000,000 per year in feed screw
inefficiencies.
Page 100 of 115
R: Links to Purchased Components and Display Videos
Appendix R lists all purchased parts with their corresponding links for purchase. It allows the
team to easily relay information to the researchers to continue the project by assembling the
proposed solution.
E-Stop: The E-Stop button is used to stop the motor in the case of an emergency.
Link: https://www.amazon.com/TWTADE-Emergency-Pushbutton-
Switches%EF%BC%88Quality-years%EF%BC%89LA38-
11ZS/dp/B07C4YCYRZ/ref=sr_1_1_sspa?dchild=1&keywords=E-
STOP&qid=1596027474&sr=8-1-
spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEyUzFXTFZSUE5PWUZWJmVuY
3J5cHRlZElkPUEwNDUzMDM5MzNJMlVMOEZCQ0pJRCZlbmNyeXB0ZWRBZElkPUEwN
jQxOTYyMVBBWU1VRzZCUjBWVyZ3aWRnZXROYW1lPXNwX2F0ZiZhY3Rpb249Y2xp
Y2tSZWRpcmVjdCZkb05vdExvZ0NsaWNrPXRydWU=
Instructional Assembly: https://www.instructables.com/id/Emergency-Stop-Button/
Strain Gauges: The strain gauges will be inserted into the bolts to measure the strain and axial
forces experienced by the bolts.
Link: https://b2bstore.hbm.com/myHBM/app/displayApp/(layout=7.01-
16_153_6_9_70_34_65_73_134&citem=A01D4895C9E81EE895EA843B7658C4CDA01D489
5C9E81ED890E05C562A8991D1&carea=A01D4895C9E81EE895EA843B7658C4CD&xcm=h
bm_b2boccasionalcrm)/.do?rf=y
Instructional Assembly: https://www.hbm.com/en/7452/cylindric-strain-gauges-for-
measurements-in-bolts/
Strain Gauge Adhesive: The strain gauge adhesive will be used to adhere the sensors into the
bolts and make sure they are set in place.
Link: https://b2bstore.hbm.com/myHBM/app/displayApp/(cpgnum=1&layout=7.01-
16_153_6_9_70_34_65_73_134_6&uiarea=6&citem=0E3B0B4E540ACD18E1000000AC1099
34A549494869EF3C62E1000000AC10A039&carea=0E3B0B4E540ACD18E1000000AC10993
4&rdb=0&cpgsize=0)/.do?rf=y
Hall-Effect Sensor: The Hall-Effect sensor will be used to record the rotation of the screw and
be used to calculate angular speed of the screw.
Link: https://www.amazon.com/Effect-Magnetic-Sensor-Arduino-
MXRS/dp/B085KVV82D/ref=sr_1_3?dchild=1&gclid=Cj0KCQjwvIT5BRCqARIsAAwwD-
R3eooa8QBsY9M3pFyHJFGiAM9JoNIE4T_VHETSDFqiOW4jD79X9vcaAvyhEALw_wcB&h
vadid=410019012916&hvdev=c&hvlocphy=9016722&hvnetw=g&hvqmt=b&hvrand=25004802
6171785736&hvtargid=kwd-
300612634942&hydadcr=15827_11428628&keywords=hall+effect+sensor&qid=1596029495&
sr=8-3&tag=googhydr-20
Page 101 of 115
ACS712 Current Sensor: The current sensor will be used to measure the current supplied to the
motor to allow the motor power to be calculated.
Link: https://www.amazon.com/SMAKN%C2%AE-ACS712-Current-Detector-
Amperage/dp/B00N2EUPUG/ref=sr_1_1?dchild=1&keywords=ACS712&qid=1596028605&ref
inements=p_76%3A1249158011&rnid=1249156011&rps=1&s=industrial&sr=1-1
L298 DC Motor Driver: The motor driver is used to control the motor speed.
Link: https://www.amazon.com/DROK-Controller-Regulator-Industrial-
Optocoupler/dp/B06XGD5SCB/ref=sr_1_1?dchild=1&keywords=DC+Motor+Driver%2C+DRO
K+L298+Dual+H+Bridge+Motor+Speed+Controller+DC+6.5V-
27V+7A+PWM+Motor+Regulator+Board+12V+24V+Electric+Motor+Control+Module+Indust
rial+160W+with+Optocoupler+ Isolation&qid=1596028696&sr=8-1
Instructional Video: https://www.youtube.com/watch?v=kv-9mxVaVzE
Arduino Mega 2560 REV3 [A000067]: The Arduino is used as an open-sourced electronic
platform for the model.
Link: https://www.amazon.com/ARDUINO-MEGA-2560-REV3-
A000067/dp/B0046AMGW0/ref=sr_1_3?dchild=1&keywords=Arduino+MEGA+2560+REV3+
%5BA000067%5D&qid=1596028730&sr=8-3
4 pcs 50kg Load Cells and HX711 Combo Pack Kit: The four piece load cell and amplifier kit
is used to measure the spring force applied.
Link: https://www.amazon.com/Degraw-amplifier-weight-Arduino-
Bathroom/dp/B075Y5R7T7/
Instructional Video: https://www.youtube.com/watch?v=LIuf2egMioA
Instructional Assembly1: https://circuitjournal.com/50kg-load-cells-with-HX711
Instructional Assembly2: https://www.instructables.com/id/Arduino-Bathroom-Scale-
With-50-Kg-Load-Cells-and-H/
HX711 Library: https://github.com/olkal/HX711_ADC
Potentiometer: The potentiometer dial is used to control the speed of the motor.
Link: https://www.amazon.com/Cylewet-Encoder-Digital-Potentiometer-
Arduino/dp/B07DM2YMT4/ref=sr_1_12_sspa?dchild=1&keywords=arduino+potentiometer&qi
d=1596114814&sr=8-12-
spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEyQkZPWUYwRENBNUJYJmVu
Y3J5cHRlZElkPUEwMjEwMjUwMktWN0VFMThEVDI2RSZlbmNyeXB0ZWRBZElkPUEw
NDc2MTEyMzQ2TzdOOERTRVlHRSZ3aWRnZXROYW1lPXNwX210ZiZhY3Rpb249Y2xp
Y2tSZWRpcmVjdCZkb05vdExvZ0NsaWNrPXRydWU=
BM504-11 Motor: This is the motor chosen to drive the screw.
Page 102 of 115
Link: https://www.mcmaster-electric.com/24V-DC-Motor-Low-Rpm-High-Torque-DC-
Planetary-Reduction-Gear-Motor-MM504-pd20496067.html
Rods: These rods are used to keep the back-pressure plate from rotating when the springs are
being compressed.
Link: https://www.grainger.com/product/NB-Shaft-3FUH7
Springs: The springs are used to apply back pressure to the end of the feed screw casing.
Link: https://www.centuryspring.com/catalog/compression-
regular?page=product&cid=compression-regular&id=12473CS
Inserts: These press fit inserts are used to create a threaded outer diameter for the bolts to secure
into the base plate.
Link: https://www.mcmaster.com/97191A150/
Wires: These are wires used for the connection of electronic components.
Link: https://www.amazon.com/120pcs-Multicolor-Jumper-Arduino-
Raspberry/dp/B01BAXKDN4/ref=asc_df_B01BAXKDN4/?tag=hyprod-
20&linkCode=df0&hvadid=198075247191&hvpos=&hvnetw=g&hvrand=13742451337297765
677&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9016164&hvt
argid=pla-317965496827&psc=1
Resistors: These resistors are used as amplifiers for the strain gauges.
Link: https://www.amazon.com/EDGELEC-Resistor-Tolerance-Multiple-
Resistance/dp/B07QH5QLR1/ref=sr_1_1_sspa?crid=3AITE4Z0LMW49&dchild=1&keywords=
120+ohm+resistor&qid=1596379149&sprefix=120+ohm+%2Caps%2C345&sr=8-1-
spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEyRVhFVUlQQ0pDMlgyJmVuY3J
5cHRlZElkPUEwOTk1NzY4MjNKSUJaTjlDVzdRVyZlbmNyeXB0ZWRBZElkPUEwNjIxMT
M3Mk5TNjhOUTFUTlJZMyZ3aWRnZXROYW1lPXNwX2F0ZiZhY3Rpb249Y2xpY2tSZWR
pcmVjdCZkb05vdExvZ0NsaWNrPXRydWU=
Motor and Screw Sprockets and Hall-Effect Gear: This is a coupling socket used to be driven
by the motor to drive the screw.
Link (1in): https://www.grainger.com/product/POWER-DRIVE-Chain-Coupling-Sprocket-
6AGR4
Link (⅝ in): https://www.grainger.com/product/POWER-DRIVE-Chain-Coupling-
Sprocket-6AGR7
Connecting Chain: This connecting chain is used to connect the motor to the coupling sprocket.
Link: https://www.grainger.com/product/POWER-DRIVE-Double-Strand-Coupling-
Chain-6AGR2?cm_sp=Product_Details-_-Customers_Also_Purchased-_-AZIDPBR_BRDS-
Page 103 of 115
040120&cm_vc=AZIDPBR_BRDS-
040120&req=Customers_Also_Purchased&opr=AZIDPBR_BRDS-040120
Xometry Parts: This is the location of all the custom made parts from xometry.
Link: https://get.xometry.com/quote/25799-15000
Supports: The supports are to support the back pressure assembly and keep it in the correct
location.
Link: https://www.homedepot.com/p/Everbilt-12-in-x-8-in-Black-Heavy-Duty-Shelf-
Bracket-14337/206086895
Aluminum Plates: The aluminum plates are used for construction of the base plate and supports.
Link: https://www.midweststeelsupply.com/store/6061aluminumplate
Bolts: These bolts will be used to connect the clamshells as well as the supports
Link: https://www.mcmaster.com/bolts/head-type~hex/fastener-strength-grade-
class~grade-8/thread-size~10-32/thread-size~1-4-20/thread-size~1-4-32/length~0-75inches/
Nuts: These nuts are used with the bolts to secure the clamshell casing.
Link: https://www.mcmaster.com/nuts/hex-nuts/thread-size~10-32/thread-size~1-4-
20/thread-size~1-4-28/thread-size~1-4-32/medium-strength-steel-hex-nuts-grade-5/
Videos as Seen in PDR Presentation:
Assembly: https://youtu.be/RSZKWf1FJ-c
Throat: https://youtu.be/x8cvvGAOm84
Screw: https://youtu.be/DeaLk9zBOrE
Pressure plate: https://youtu.be/R45zu0PEFkQ
Page 104 of 115
S: Assembly Instructions
Baseplate
1: Starting from the side with 30 insert cavities, place support plates over the ¾ in. holes along
the long sides of the base plate in the following order:
a. Small Diameter Support Plate (¾ in. wide, 2 in. diameter semicircle cavity)
b. 4 Large Diameter Support Plates (¾ in. wide, 4 in. diameter semicircle cavity)
c. Tallest Support Plate (contains bolt holes for hopper bearing)
d. 4 in. wide Motor Support Block
e. Support Plate with side panel for E-Stop and RPM Knob
The Support Plate positions can be seen in the full assembly picture below:
2: Insert ¾” long bolts through each support plate and base plate.
2: Thread a nut onto each bolt underneath the base plate and tighten.
3: Hammer/Press Press-Fit inserts into each of the 30 cavities
4: Insert E-Stop and RPM Knob (Potentiometer) into the correct positions within the side panel
of the Support Plate. The back view of the control panel should look like the picture below:
Page 105 of 115
Hopper:
1: Place the hopper into position with the collection portion sitting on the tallest support plate
and the flange sitting between the two close proximity support plates.
2: Attach the large bearing with a bore diameter of 1 in. on the opposite side of the tallest support
plate, so that the bore lines up with the existing hole in the hopper
a. Nut and Bolt the bearing to the support plate using the only 2 larger diameter bolts and
nuts. The hopper should be pushed up against this bearing to be in the correct place.
3: After successful attachment of the bearing, the feed screw can be inserted through the large
opening in the hopper, with the 1 in. diameter shaft feeding through the bearing.
Progress thus far will resemble the picture below:
Feed Screw Shaft:
1: Once the Feed Screw has been fed through the bearing, slide on the two 1 in. bore diameter
sprockets, the first with its gear facing the hopper, and the second the gear facing away from the
hopper. These should come into direct contact with each other.
2: Slide the sprockets so that the gear side of the second sprocket lines up with the end of the
feed screw shaft
a. Insert Set screws into the sprockets to hold them in place on the feed screw shaft.
Motor:
1: Slide the ⅝ in. bore diameter sprocket onto the motor driveshaft, so that the gear side lines up
directly with the end of the motor shaft.
a. Insert a Set screw into the sprocket to hold it in place on the motor driveshaft.
2: Place the motor onto the 4” wide support plate, with the shaft pointing toward the hopper and
the fat end sitting on the support plate with the control panel.
Page 106 of 115
3: Maneuver the feed screw shaft so that the sprockets on the feed screw shaft and motor drive
shaft are mated on their gear sides.
4: Wrap the coupling chain around both gears and insert the locking pin to couple the two shafts
together as one.
Progress to this point would look similar to the rendered pictures below:
Page 107 of 115
Throat:
1: Take one half of the clam-shell throat and place the end flanges in between the sets of support
plates right next to the hopper.
2: 1 ½ in. bolts can now be fed through the support plates between the hopper and throat, and a
nut can be tightened on the opposite side, securing both the hopper and bottom half of the throat
to the support plates.
3: The top half of the throat can now be placed directly on top of the bottom half, and secured
through the 4 coinciding flaps with strain gauge inserted ¾ in. bolts, and tightened with a nut on
the bottom.
4: The same can be done through the coinciding top flange holes of the hopper, also with strain
gauge inserted bolts and a nut to tighten.
Plug:
1: Repeat the same steps as previously listed for the throat, first installing the bottom half of the
clam shelled plug and using a 1 ½ in. bolt and nut to secure it to the supporting plates holding the
throat.
2: The top half can again be laid on top of the bottom half, with flaps and flange connections
secured by strain gauge inserted ¾ in. bolts and nuts on the opposite sides
When finished with the throat and plug, the assembly should resemble the picture below, with
feed screw inside:
Page 108 of 115
Mass Flow Load Cells:
1: As seen above just to the left of the plug, 4 load cells should be attached to the baseplate, so
that pressed together they form a rectangle. The shorter sides of the load cells should be parallel
to the long sides of the base plate.
a. Later on when ready for testing, a simple container of any kind may be placed on these
load cells, which will measure the mass flow as a function of time.
Pressure Plate:
1: The 4 steel rods are to be inserted through the flange holes on the end of the plug, and bolts
are to be inserted into the threaded holes in the rods to secure them to the flange.
2: Once the rods are in place, the conical plug plate may be inserted onto the rods with the cone
side facing into the end of the plug.
3: Next, 4 springs are to be threaded onto the rods.
4: The 3 in. by 3 in. simple steel plate follows the springs
5: One singular load cell is to be attached in the exact center of the 9.5 in. by 9.5 in. steel plate,
which is then pushed onto the rods where the load cell will butt up against the simple plate,
which will butt up against the springs, which butt up against the conical plug plate, which will
butt up against the end of the plug.
Progress thus far will result in the pictures shown below:
Page 109 of 115
Shelf Supports (Brackets):
1: Finally, the 9.5 in. by 9.5 in. plate will be secured in place to the base plate using ¾ in. bolts.
As apparent, the base plate offers 5 sets of holes for each bracket. These sets are meant to
provide the springs with a specific displacement to cause a specific pressure on the exit of the
feed screw. The sets of holes produce the following pressures, moving from the most outer set to
the most inward set (Opposite bracket always mounts in the set of holes equidistant from the
center line):
● Outer Set: 50 psi for 1.5 in. inner diameter exit
● 30 psi for 1.5 in. inner diameter exit
● 15 psi for 1.5 in. inner diameter exit
● 50 psi for 1.25 in. inner diameter exit
● Inner Set: 15 psi for 1.25 in. inner diameter exit
○ NOTE: In order to achieve 30 psi for 1.25 in. inner diameter exit, the outermost
set of holes can be used.
2: Once the set of mounting holes has been chosen, secure the brackets to the base plate.
3: Use all 6 of the 10-32 bolts and nuts to attach the brackets to the 9.5 in. by 9.5 in. A36 Steel
Plate.
Through this step, the assembly should resemble the following picture:
Page 110 of 115
Electronics:
The following wiring diagram should be followed when assembling the circuit:
The location of most components will be the open portion of the base plate next to the motor.
However, the Hall-Effect Sensor should be located directly under the open geared sprocket,
mounted on the support plate with a side panel. Obviously, the strain gauges and load cells were
previously attached, and have specific locations that can be reached with wiring. Otherwise, the
circuit can be created resembling the picture below:
Page 111 of 115
It is important to note that only one set of resistors and Amplifiers are shown for simplicity of the
3D model, but each strain gauge and set of load cells will have its own set of each.
The final product should closely resemble the final prototype illustrated below:
Page 112 of 115
T: Manufacturing Plan
Appendix T lists the manufacturing plans for parts manufactured on-site by our clients.
These include all support plates and the baseplate, and exclude the complex parts sent to
Xometry for machining.
Table 4: Base Manufacturing
DRAWING NO: BASE
STE
P OPERATION DESCRIPTION EQUIPMENT
1 SECURE PART
Screw outer edges of stock plate to base of CNC
cutting surface
Bolts attached to CNC
base
2 CUT PROFILE 1/4 inch tool, multiple passes at 1/8 inch CNC Mill
3 DRILL HOLES 1/4 inch tool CNC Mill
4 SMOOTH Smooth edges to prevent sharp surfaces CNC Mill
Table 5: Frame Manufacturing (1 of 3)
DRAWING NO: SMALL PLUG FRAME, BIG PLUG FRAME, HOPPER FRAME, MID MOTOR FRAME
STE
P OPERATION DESCRIPTION EQUIPMENT
1
SECURE
PART
Screw outer edges of stock plate to base of CNC
cutting surface
Bolts attached to CNC
base
2 CUT PROFILE 1/4 inch tool, multiple passes at 1/8 inch CNC Mill
3 DRILL HOLES on the same face as step 2, using a 1/4 inch tool CNC Mill
4
SECURE
PART
Stand part vertically, Screw outer edges of stock
plate to base of CNC cutting surface
Bolts attached to CNC
base
5 DRILL HOLES 1/4 inch tool, multiple passes at 1/8 inch CNC Mill
6 SMOOTH Smooth edges to prevent sharp surfaces CNC Mill
Page 113 of 115
Table 6: Frame Manufacturing (2 of 3)
DRAWING NO: BIG HOPPER FRAME
STEP OPERATION DESCRIPTION EQUIPMENT
1 SECURE PART
Screw outer edges of stock plate to base of CNC
cutting surface
Bolts attached to
CNC base
2 CUT PROFILE 1/4 inch tool, multiple passes at 1/8 inch CNC Mill
3 SECURE PART
Flip over, screw outer edges of stock plate to
base of CNC cutting surface CNC Mill
4 CUT PROFILE 1/4 inch tool, multiple passes at 1/8 inch CNC Mill
5 SECURE PART
Stand part vertically, Screw outer edges of stock
plate to base of CNC cutting surface
Bolts attached to
CNC base
5 DRILL HOLES 1/4 inch tool, multiple passes at 1/8 inch CNC Mill
6 SMOOTH Smooth edges to prevent sharp surfaces CNC Mill
Table 7: Back Plate Manufacturing
DRAWING NO: BACK PLATE
STEP OPERATION DESCRIPTION EQUIPMENT
1 SECURE PART
Screw outer edges of stock plate to base of CNC
cutting surface
Bolts attached to CNC
base
2 DRILL HOLES 1/4 inch tool CNC Mill
3 SMOOTH Smooth edges to prevent sharp surfaces CNC Mill
Page 114 of 115
Table 8: Pressure Plate Manufacturing
DRAWING NO: PRESSURE PLATE
STEP OPERATION DESCRIPTION EQUIPMENT
1 SECURE PART
Screw outer edges of stock plate to base of CNC
cutting surface
Bolts attached to
CNC base
2
CUT VERTICAL
PROFILE 1/4 inch tool, multiple passes at 1/8 inch CNC Mill
3 DRILL HOLES 1/4 inch tool CNC Mill
4 SMOOTH Smooth edges to prevent sharp surfaces CNC Mill
Table 9: Frame Manufacturing (3 of 3)
DRAWING NO: MOTOR BACK FRAME
STEP OPERATION DESCRIPTION EQUIPMENT
1 SECURE PART
Screw outer edges of stock plate to base of CNC
cutting surface
Bolts attached to
CNC base
2 CUT PROFILE 1/4 inch tool, multiple passes at 1/8 inch CNC Mill
3 SECURE PART
Stand part vertically, Screw outer edges of stock
plate to base of CNC cutting surface
Bolts attached to
CNC base
4 DRILL HOLES 1/4 inch tool, multiple passes at 1/8 inch CNC Mill
5 SMOOTH Smooth edges to prevent sharp surfaces CNC Mill
Table 10: Bolt Manufacturing
DRAWING NO: BOLT
STEP OPERATION DESCRIPTION EQUIPMENT
1 SECURE PART Clamp screw Vertical Milling Machine Clamp
2 DRILL HOLE 2 mm tool Vertical Milling Machine
Page 115 of 115
U: Table of Fits and Tolerances
Appendix U lists the fits and tolerances required by the system. It allows the team to plan how it
will manufacture the parts and how tightly dimensions must be controlled.
Table 11 below lists the two shaft/hole fits present in our design post critical design. It
includes tolerances for both the hole in the hopper through which the feed screw shaft extrudes,
as well as the typical bolt connection present between flanges and clamshells.
Table 11: Fits and Tolerances
Fit Hole Size/Tolerance Shaft Size/Tolerance
Feed Screw into Hopper Hole MMC 4.5022 4.5 +0.0022, -0.0000
4.4981 4.495 -0.0014 -0.0050 LMC 4.5000 4.4900
1/4" Bolt into Flange Hole MMC 0.2509 0.25
+0.0006, -0.0000
0.2495 0.2495 -0.0006 -0.0000 LMC 0.2500 0.2489
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