REDESIGN OF THE LOWER CURVE PORTION OF THE BELT TRACK FOR
THE 1.5” PITCH, 60°, JORGENSEN HINGED STEEL BELT (MILLENIUM)
CONVEYOR.
By
Gregory D. Michalak
A Report Submitted For
MT-4901, CAPSTONE PROJECT
In Partial Fulfillment of the
Requirements for the Degree of
Bachelor of Science in Mechanical Engineering Technology
Milwaukee, Wisconsin
November, 2006
ABSTRACT
The purpose of this project is to fulfill the requirements for the degree of
bachelor’s of science in mechanical engineering technology. The project I chose to do
was the design of a part for a Jorgensen Conveyors Inc. Conveyor. This part would take
the place of 4 pieces currently welded together.
The purpose of this part is that it is part of the track for the belt to travel in. It is
positioned at the lower curve section of the conveyor where the belt transitions from the
horizontal to the 60° incline. See the Appendix for a drawing of this type of conveyor and
where this part would be located.
The manufacturing processes chosen to make this into one piece was the die
casting process.
Using the NADCA (North American Die Casting Association) Product Design for
Die Casting OEM Design Sourcebook and the help of my advisor for this project,
Professor Dave Gerow, a part was designed that can be casted using the popular die
casting process.
After the design was complete, aluminum alloy ANSI C443.0 was chosen as the
material for the purpose of this project and a structural static analysis using FEA was
performed on the part to ensure that it would be able to perform its intended function
under normal operating conditions. After concurrently using the solid modeling package
Solidworks student edition 2006 w/ CosmosWorks, the part was geometrically optimized.
Because the material used in this analysis has a ductility greater than 5%, which is
considered ductile, the failure theory used for this analysis was the ductile theory of Von-
Mises. Using the Von-Mises Stress, called the effective stress, the maximum value
1
according to Cosmosworks was 6443 PSI for the upper curve and 5851 PSI for the lower
curve. Since both values are below the yield strength of 17,000 PSI, the part according to
the theory will not yield. The smallest factor of safety for the upper and lower curve was
2.2 and 2.4 respectively.
This design according to my analysis will not fail. Further study will be taken as
to possible other materials to be used. The problem with die casting is that there are not
many materials to choose from and most are considered brittle (less than 5% ductility).
The design can be casted because of the features I put into the part which are: draft,
rounds, and uniform wall thicknesses. A cost analysis of this design compared to the
welding of four materials will be done at a future time. If it is proved that it cost more to
cast this piece than to weld four pieces together, other manufacturing processes will be
looked at such as: sand casting and investment casting.
Thanks to this project, I have gained more confidence in myself to perform finite
element analysis.
2
ACKNOWLEDGEMENTS
I would like to acknowledge Jorgensen Conveyors Inc. for giving me this
opportunity to fulfill my requirements for MT-4901.
I would also like to give acknowledgements to Professor Dave Gerow of MSOE
for his help with my project. He gave me much advice as to the design of the casting and
how to go about performing the FEA correctly. He also showed me how to verify
complicated designs using strength of materials theory that I didn’t know how to do
before.
3
TABLE OF CONTENTS
List of figures Pages 5-14
Introduction & Background Page 15
Discussion
Explanation of Casting Design Pages 16-17
Explanation of the FEA analysis Pages 18-20
Conclusion Pages 21-22
Bibliography Page 23
Appendix See attachments
4
LIST OF FIGURES
Figure A. Current pieces that are welded together for the lower curve piece
Figure B. The four pieces welded together to the inside of the conveyor casing
Skirt
Hot rolledM1044bar stock
5
Figure C. Front isometric view of initial casting design
Figure D. Front isometric view of final casting design
Direction belt moves in casting
Ribs designed into front of casting
skirt Upper curve and lower curve respectively
Bosses @ the bottom of the casting add material to the very bottom of the piece in case the belt would completely lose its tension and fall.
6
Figure E. Back isometric view of initial casting design
Section is cored out to reduce mass. In the final design ribs are employed to reinforce the wall of the skirt.
Buckling is evident here. Upper curve bends up while skirt portion bends down.
Figure F. Deformation Plot of original casting due to the loading on the upper curved portion.
7
Figure G. Back isometric view of final casting design
Figure H. Deformation Plot of final casting due to the loading on the upper curved
portion
Ribs designed into back of the casting
Skirt wall reinforced with ribs.
Not as much deformation as in the first design.
Welded on this edge
Welded on these edges
8
Figure I. Upper curve boundary conditions of final casting design for FEA
(front isometric view)
Figure J. Upper Curve boundary conditions of final casting design for FEA
(back isometric view)
9
Figure K. Lower Curve boundary conditions of final casting design for FEA
(front isometric view)
Figure L. Lower Curve boundary conditions of final casting design for FEA
(back isometric view)
10
Figure M. Stress analysis plot of upper curve of final design
Max. stress for upper curve section of final design
11
Figure N. Stress analysis plot of lower curve of final design
Max. stress for lower curve section of final design
12
Figure O. Point load deformation of upper curve (scaled to 300)
Figure P. Distributed load deformation of upper curve (same scale, 300)
Not a realistic deformation. Loads never act at a single point but are distributed over an area.
Much betterRepresentation of the loads acting on the upper curve.
13
Figure Q. Split lines shown on upper curve
Figure R. Resultant Reaction force for entire model for upper curved portion of the
analysis
Separate surfaces created. Intersections of these separate surfaces is where the forces were applied.
14
Figure S. Resultant reaction force for entire model for lower curve portion of the analysis
Figure T. A section of a 1.5” pitch conveyor belt
Figure U. Side view of the 1.5” pitch section of the belt
Rollers of the belt
1.5” pitch distance
15
INTRODUCTION & BACKGROUND
Jorgensen Conveyors Inc., headquartered in Mequon, Wisconsin, designs and
manufactures conveyors and material handling equipment.
In an attempt to save costs, a design for assembly project has been identified that
could save the company money. The current lower curve portion of the 1.5” pitch
Jorgensen conveyor is welded into an assembly using four parts. As shown in Figure A
on page 5, one of the pieces is a sheetmetal part (called the skirt) that Jorgensen forms in
a brake press but the material, 14 gage sheetmetal, is purchased from Award
Manufacturing at $.80/in. The other 3 pieces are hot rolled bar stock M1044 and are
purchased from Central Steel & Wire Company at a cost of $.45/in. As of 2006, it cost
Jorgensen $1.07/in. to weld (includes labor, materials, and tools). According to Jorgensen
Conveyors it costs $33.00 to manufacture that piece.
The objective of this design is to design a part that costs less than the current costs
to produce the curved piece for the belt track.
The constraints of this design are:
1) The dimensions of the part cannot be changed except for the wall thickness
2) The ability of the part to withstand the 325 lb force from the belt tension
3) That the part cost less than the current cost now to produce this assembly
During the design process, two designs were compared using FEA. The initial
design shown in Figures C & E on pages 6 & 7 had no ribs designed into any
portion of the part, and the final design does have ribs designed into it.
This report will focus on the final design and the reason for this decision.
16
DISCUSSION
Explanation of the casting design
The reason for the shape of the part is that in this area the belt transitions from
moving horizontal to an incline angle of 60°. If this part was not part of the conveyor
assembly, the belt would rise up due to the 325 lbs of tension on the belt and would
interfere with the casing of the conveyor and would not move. As shown in Figure D on
page 6, the belt moves in a clockwise direction with the rollers making contact with the
upper curve of the casting when moving up the incline and then when it comes around the
headshaft and transitions back down the incline the rollers make contact with the lower
curve of the casting design.
For the casting design I followed these rules according to the NADCA(north
American die casting association)[1]:
1) Uniform wall thickness
In both designs as shown in Figures C&D on page 6, a wall thickness of 0.156” is
maintained throughout the part.
2) Fillets and rounds at intersections between perpendicular surfaces
In Figures C &D on pgs. 6 & 7 the part has fillets and rounds where any two
perpendicular surfaces intersect. According to NADCA, fillets and rounds reduce the
stress concentration between those surfaces. A corner will have a much higher stress
concentration than a fillet or round will [1]. If there is too large a fillet or radius
according to Degarmo, Black, & Kohser, then this may create a hot spot [3]. This corner
is thicker in cross section than the wall thickness of the casting. These areas because they
are thicker tend to cool slower and tend to be areas of abnormal shrinkage[3]. When the
17
differences are large, the hot spot areas are likely to contain defects such as porosity or
voids, and the part is likely to fail in these areas[3].
3) Draft of 1°on surfaces where the die and casting surfaces would separate from each
other
According to NADCA, draft is highly desirable on surfaces of the part parallel to
the direction of withdrawl of the die from the casting because it allows the casting
to release easily from the die surfaces [1].
4) Ribs at the back end of the part that is cored out
In Figure G on page 8, ribs are designed into the part. The function of these ribs is
to keep strength in that portion of the casting while removing mass from it. As shown in
figures F & H on pages 7& 8, the ribs help reduce deformation in the skirt portion of the
part. The ribs are spaced approximately 1.5” apart, the distance the pitch of the belt is.
Pitch is the distance between the centers of two adjacent rollers and is shown in Figures T
& U on page 15.
5) Bosses added to increase strength at very bottom of part
The function of the bosses in Figure D on page 6 is to create a safety
mechanism built into the part in case the belt would lose its tension and
fall partly onto the bottom of the part. A Jorgensen conveyors belt could
weigh anywhere from 30 to 100 lbs or more for a 1.5” pitch conveyor.
18
Explanation of the Fea analysis
The Von - Mises criteria for ductile materials was used as a theoretical way to
verify that this part would not fail under normal operating conditions. The material
chosen for this design was aluminum die casting alloy C443.0. This material was chosen
mainly because it was one of the few with ductility greater than 5%.
The Von-Mises criterion was the chosen criterion used in this analysis over the
Maximum Principal Stress criterion and Tresca Criterion because it provides the best
correlation. The Tresca criterion provides good correlation, but is more conservative than
the Von-Mises criterion. The Maximum Principal Stress criterion produces
unconservative results for some loading conditions, and should not be used for ductile
materials [2].
A static linear analysis was chosen for this part because the part is fixed in space,
the loads acting on the part don’t vary with time, and the material behaves in a linear
fashion. The load put on both the upper and lower curves of the part is the chain pull of
the belt which is a constant 325 lbs.
Their were two separate analysis done: one for the upper curved portion of the
part when the belt is moving up the incline and the other when the belt is transitioning
from the incline to the horizontal. The reason for the two separate analysis is that their
cannot be tension in both the upper and lower portions of the belt if it’s to move; their has
to be slack in one portion of the belt for it to move.
For the upper curved analysis when the belt is transitioning from the horizontal to
the incline approximately 5 rollers will be in contact with the part. I approximated this
because each roller is spaced 1.5” between centers of the adjacent roller. I then divided
19
the 325 lb chain pull by 5 to give each roller an approximate force of 65 lbs acting
upward on the curve. Then I divided this force by the number three because this is how
many vectors I placed at each location. Spreading this force to three vectors distributed
the load better than a point load. A point load would not represent the surface of the
roller. Also, when a point load was applied at each location the deformation plot was not
representative of what the actual deformation should look like. You can see the difference
in the deformation in Figures O & P on page 13.
For the lower curve analysis when the belt is transitioning from the incline to the
horizontal approximately 7 rollers will be in contact with the part. The 325 lbs of force
was divided by 7 to give each roller an approximate force upwards on the surface of 47
lbs. I then divided this number by three, the number of vectors placed at each area. An
explanation as to why three vectors were chosen was given above.
In order to properly apply the loads to the part as they would be applied in the real
world, the areas where the loads were applied to were broken into separate surfaces using
datum points, planes, and split lines in Solidworks student edition 2006 w/ cosmosworks.
The split line function in solidworks allows you to split up an area into several areas. The
vertex of these intersecting areas is where you can apply loads to [4]. In Fig. Q on page
14 it shows that the upper surface was broken into individual surfaces.
The restraints chosen for this part were chosen by taking into consideration as to
how this part would be fixed in space. The back portion of the piece would be laying flat
against the inside surface of the casing, so an on flat face restraint was applied to this
surface. The vectors are pointing towards where the casing would be because it’s
preventing the part from translating in the positive z-direction (for this part the z-axis is
20
the x-axis). According to Sheppard & Tongue if a restraint prevents the translation of the
system in a given direction, then a force and or moment acts on the system at that
location of the restraint in the opposing direction [5]. The upper edge of the skirt was
given an immovable constraint because this is where a weld will be placed along, so no
translation or rotation will take place along that edge. Finally the curved cutouts, two on
each side, was given fixed constraints because this is also where a weld will be placed
along, so no translation or rotation will take place along those bottom edges. Figures I
thru L on pages 9 & 10 show the restraints by the use of green vectors.
Verification of Analysis
Using cosmosworks the verification was done using the reaction forces provided
in the study. In Figures R & S on pages 14 & 15 it shows that for the upper & lower
curve the reaction force equals the load of 325 lbs applied. (0.14 lbs error for upper curve
& (1.5 lbs error for lower curve)
21
CONCLUSION
The purpose of this project is to fulfill the requirements for the degree of
bachelor’s of science in mechanical engineering technology. The project I chose to do
was the design of a part for a Jorgensen Conveyors Inc. Conveyor. This part would take
the place of 4 pieces currently welded together.
The purpose of this part is that it is part of the track for the belt to travel in. It is
positioned at the lower curve section of the conveyor where the belt transitions from the
horizontal to the 60° incline.
The manufacturing processes chosen to make this into one piece was the die
casting process.
Using the NADCA (North American Die Casting Association) Product Design for
Die Casting OEM Design Sourcebook and the help of my advisor for this project,
Professor Dave Gerow, a part was designed that can be casted using the popular die
casting process.
After the design was complete, aluminum alloy ANSI C443.0 was chosen as the
material for the purpose of this project and a structural static analysis using FEA was
performed on the part to ensure that it would be able to perform its intended function
under normal operating conditions. After concurrently using the solid modeling package
Solidworks student edition 2006 w/ CosmosWorks, the part was geometrically optimized.
Because the material used in this analysis has a ductility greater than 5%, which is
considered ductile, the failure theory used for this analysis was the ductile theory of Von-
22
Mises. Using the Von-Mises Stress, called the effective stress, the maximum value
according to Cosmosworks was 6443 PSI for the upper curve and 5851 PSI for the lower
curve. Since both values are below the yield strength of 17,000 PSI, the part according to
the theory will not yield. The smallest factor of safety for the upper and lower curve was
2.2 and 2.4 respectively.
This design according to my analysis will not fail. Further study will be taken as
to possible other materials to be used. The problem with die casting is that there are not
many materials to choose from and most are considered brittle (less than 5% ductility).
The design can be casted because of the features I put into the part which are: draft,
rounds, and uniform wall thicknesses. A cost analysis of this design compared to the
welding of four materials will be done at a future time. If it is proved that it cost more to
cast this piece than to weld four pieces together, other manufacturing processes will be
looked at such as: sand casting and investment casting.
Thanks to this project, I have gained more confidence in myself to perform finite
element analysis.
23
BIBLIOGRAPHY
[1] North American Die Casting Association.1998. PRODUCT DESIGN FOR DIE CASTING, 5TH ed. Page 26, “Developing the Configuration.”
[2] Howard, William E. March 2004. “Failure Criteria.” Class notes from MT-3601: Finite Element Analysis. Professor Dr. William “Ed” Howard. MSOE, Milwaukee, Wisconsin. Available from author.
[3] Degarmo, Paul E., Black, J.T., Kohser, Ronald A. MATERIALS AND PROCESSES IN MANUFACTURING, 9Th ed. Chapter 13, Fundamentals of Casting, page 292.
[4] Tickoo, Sham. SOLIDWORKS for Designers Release 2005. Chapter 9, Advanced Modeling Tools-III, page 31.
[5] Sheppard, Sheri D., Tongue, Benson H. STATICS, ANALYSIS AND DESIGN OF SYSTEMS IN EQUILIBRIUM, 1ST ed. Chapter 6, DRAWING A FREE-BODY DIAGRAM, page 219.
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APPENDIX
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