Design for ManuFacturing
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Design for Manufacturing
ByRaghavendra(093303)Gangadhar(093304)Bhagwath(093306)
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Design for X Topics
Design for Manufacturing
Design for Production
Design for Assembly
Design for Recycling/Disposal
Design for Life Cycle
Prototyping
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Manufacturing cost is a key determinant of the economic success of a product since such success depends on the profit margin earned on each sale of the product and on how many units of the product the firm can sell. Profit margin is the difference between the manufacturer’s selling price and the cost of making the product.
Economically successful design is thus about ensuring high product quality while minimizing manufacturing costs and DFM is one method of achieving this
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DFM requires cross-functional team
DFM utilizes information of several types: Sketches, drawings, product specifications, and design
alternatives. A detailed understanding of production and assembly
processes Estimates of manufacturing costs, production volumes, and
ramp-up timing. DFM efforts commonly draw upon
expertise from manufacturing engineers ,cost accountants and production personnel, in addition to product designers.
DFM is performed throughout the Development process.
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DFM Method
1. Estimate the manufacturing costs.
2. Reduce the costs of components.
3. Reduce the costs of assembly.
4. Reduce the costs of supporting production.
5. Consider the impact of DFM decisions on other
factors.
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DFM Method
Estimate the ManufacutringCosts
Consider the Impact of DFMDecisions on Other Factors
Recompute theManufacturing Costs
Reduce the Costs ofSupporting Production
Reduce the Costs ofAssembly
Reduce the Costs ofComponents
Goodenough
?
N
Y
Acceptable Design
Proposed Design
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Estimate the Manufacturing Costs
Finished GoodsManufacturing System
Equipment Information Tooling
WasteServicesSuppliesEnergy
Raw Materials
Labor
PurchasedComponents
INPUT-OUTPUT MODEL OF A MANUFACTURING SYSTEM
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Definition of Manufacturing Cost:
• Sum of all the expenditures for the inputs of the system
(i.e. purchased components, energy, raw materials, etc.)
and for disposal of the wastes produced by the system
• Unit manufacturing cost is computed by dividing the
total manufacturing costs for some period(usually a
quarter or by a year) by the number of units of the
product manufactured during that period.
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Elements of the Manufacturing Cost of a Product
Manufacturing Cost
OverheadAssemblyComponents
Standard Custom LaborEquipmentand Tooling
SupportIndirect
Allocation
RawMaterial
Processing Tooling
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Fixed Costs vs. Variable Costs
• Fixed Costs – incurred in a predetermined amount, regardless of number of units produced
(i.e. setting up the factory work area or cost of an injection mold)
• Purchasing injection mold is example of fixed cost.
• Variable Costs – incurred in direct proportion to the number of units produced
(i.e. cost of raw materials)• Cost of raw materials is example of variable cost.
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ESTIMATING COSTS OF STANDARD COMPONENTS
• The costs of standard components are estimated by either
• Comparing each part to a substantially similar part the firm is already
is producing or purchasing in comparable volumes or
• Soliciting price quotes from vendors or suppliers.
ESTIMATING COSTS OF CUSTOM COMPONENTS
• When the custom component is a single part , we estimate its cost by
adding up the costs of raw materials ,processing and tooling.
• The raw materials costs can be estimated by computing the mass of
the part, allowing for some scrap, and multiplying by the cost per unit
mass of the raw material.
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• Processing costs include costs for the operator(s) of the processing
machinery as well as the cost of using the equipment itself.
• Tooling costs are incurred for the design and fabrication of the
cutters,molds,dies or fixtures required to use certain machinery to
fabricate parts
ESTIMATING THE COST OF ASSEMBLY
• Manual assembly costs can be estimated by summing the estimated
time of each assembly operation and multiplying by a labor rate.
• Assembly operations require from about 4 seconds to about 60
seconds each, depending upon the size of the parts , the difficulty of
the operation , and the production quantities .
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ESTIMATING THE OVERHEAD COSTS
• Most firms assign overhead charges by using overhead rates( also
called burden rates).
• Overhead rates are typically applied to one or two cost drivers.
• Cost drivers are parameters of the product which are directly
measurable.
• Overhead charges are added to direct costs in proportion to the
drivers.
• Under the ABC approach , a firm utilizes more and different cost
drivers and allocates all indirect costs to the associated cost drivers
where they fit best.
• As a result , the firm may have overhead rates applied to various
dimensions of product complexity
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• EXAMPLE REPRESENTING CALCULATION OF MANUFACTURING COST
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Reduce the Cost of Components
• Understand the Process Constraints and Cost Drivers
• Redesign Components to Eliminate Processing Steps
• Choose the Appropriate Economic Scale for the Part
Process
• Standardize Components and Processes
• Adhere to “Black Box” Component Procurement
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Understand the Process Constraints and Cost Drivers
Redesign costly parts with the same performance while avoiding high manufacturing costs.
Work closely with design engineers—raise awareness of difficult operations and high costs.
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Redesign Components to Eliminate Processing Steps
• Reduce the number of steps of the production process
• Eliminate unnecessary steps.
• Use substitution steps, where applicable.
• Analysis Tool – Process Flow Chart and Value Stream Mapping
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Choose the Appropriate Economic Scale for the Part Process
• Fixed costs divided among more units.
• Variable costs are lower since the firm can use more efficient processes and equipment.
Economies of Scale – As production volume increases, manufacturing costs usually decrease.
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Standardize Components and Processes
• Economies of Scale – The unit cost of a component decreases as the production volume increases.
• Standard Components—common to more than one product
• Analysis tools – group technology and mass customization
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Adhere to “Black Box” Component Procurement
• Black box—only give a description of what the component has to do, not how to achieve it.
• Successful black box design requires clear definitions of the functions, interfaces, and interactions of each component.
BLACK BOXCustomers Requirement Out Put
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Reduce the Costs of Assembly
• Design for Assembly (DFA) index
• Integrated Parts (Advantages and Disadvantages)
• Maximize Ease of Assembly
• Consider Customer Assembly
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The Assembly from Heaven*
• Can be assembled one-handed by a blind person
wearing a boxing glove
• Is stable and self-aligning
• Tolerances are loose and forgiving
• Few fasteners
• Few tools and fixtures
• Parts presented in the right orientation
• Parts asymmetric for easy feeding
• Parts easy to grasp and insert
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Design for Assembly Index
DFA index =(Theoretical minimum number of parts) x (3 seconds)
Estimated total assembly time
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Determining the Theoretical Minimum Number of Parts
• Does the part need to move relative to the rest of the assembly?
• Must the part be made of a different material from the rest of the assembly for fundamental physical reasons?
• Does the part have to be separated from the assembly for assembly access, replacement, or repair?
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Integrated Part Design
Home Hot Water System Family Part
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Comparison between Assembled & Integrated Parts
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Advantages of Integrated Parts
• Do not have to be assembled• Often less expensive to fabricate rather than the sum
of each individual part• Allows critical geometric features to be controlled by
the part fabrication process versus a similar assembly process
Disadvantages of Integrated Parts• Conflict with other sound approaches to minimize
costs• Not always a wise strategy
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Maximize Ease of Assembly
• Part is inserted from the top of the assembly
• Part is self-aligning• Part does not need to be oriented• Part requires only one hand for
assembly• Part requires no tools• Part is assembled in a single,
linear motion• Part is secured immediately upon
insertion
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Consider Customer Assembly
• Customers will tolerate some
assembly
• Design product so that customers
can easily and assemble correctly
• Customers will likely ignore
directions
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DFMA Example
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DFMA-Example 1 Analysis• DFMA Worksheet for Datum Design
• 133.0• 160.0• 4• 19• TOTALS
• 26.0• 34.2• 0• 4• Cover Screw
• 7.9• 9.4• 0• 1• Cover
• 3.8• 4.5• -• -• Reorient
• 4.2• 5.0• -• -• Thread lead
• 2.9• 3.5• 0• 1• Plastic bush
• 13.8• 16.6• 0• 2• End-plate screw
• 7.0• 8.4• 1• 1• End plate
• 13.3• 16.0• 0• 2• Standoff
• 8.8• 10.6• 0• 1• Setscrew
• 7.1• 8.5• 1• 1• Sensor Subassembly
• 17.5• 21.0• 0• 2• Motor Screw
• 7.9• 9.5• 1• 1• Motor Subassembly
• 10.2• 12.3• 0• 2• Bush
• 2.9• 3.5• 1• 1• Base
• Assembly Cost (cents)
• Assembly Time(s)• Theoretical Part Count
• Number• Item
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DFMA Example 1 Analysis
• Total actual assembly Time T1= 163 s
• Theoretical total part count is 4 and average assembly time is 3 s. Theoretical assembly time
T2= 4 x 3 s = 12 s
• Calculate Design Efficiency :
•
• or 7.362%
07362.0163
12
1
2 s
s
T
T
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DFMA Recommended redesign
• Bushes are integral to the base• Snap-on plastic cover replaces standoff, cover ,plastic bush, six screws.• Using pilot point screw to fix the base, which
redesign to be self-alignment.
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DFMA- An Improved Design
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DFMA Worksheet for an Improved Design
• 38.4
• 3.3
• 7.1
• 7.1
• 10.0
• 3.8
• 2.9
• Assembly Cost (cents)
• 4.2
• 46.0• 4• 7• TOTALS
• 4.0• 0• 1• Plastic Cover
• 0• 1• Setscrew • 8.5
• 1• 1• Sensor Subassembly
• 12.0• 0• 2• Motor Screw
• 4.5• 1• 1• Motor Subassembly
• 3.5• 1• 1• Base
• Assembly Time(s)
• Theoretical Part Count
• Number• Item
• 8.5
• -• -• Thread leads • 5.0
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DFMA Cost Differential Worksheet
.
• Totals
• Cover screw(4)
• Cover
• Plastic bush
• End-plate Screw
• Endplate
• Standoff(2)
• Setscrew
• Motor Screw(2)
• Bush(2)
• Base (Aluminum)
• Item
• Old Design
• 21.73• 35.44
• 0.40
• 8.00• Plastic Cover (include tooling)
• 8.05
• 0.10
• 0.20
• 5.89
• 5.19
• 0.10• Setscrew• 0.10
• 0.20• Motor Screw(2)• 0.20
• 2.40
• 13.43• Base (nylon)• 12.91
• Cost, $• Item• Cost,$
• New Design
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Improved Assembly Design Efficiency
• Total actual assembly Time T1= 46 s• Theoretical total part count is 4 and average
assembly time is 3 s. Theoretical assembly time T2= 4 x 3 s = 12 s
• Calculate Design Efficiency :
• or 26.087%
26087.046
12
1
2 s
s
T
T
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DFMA –Calculate Total Saving
Total Saving = Saving from Assembly Time Reduction + Saving from parts reduction = $0.95 + $13.71 = $14.66
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Estimate the ManufacutringCosts
Consider the Impact of DFMDecisions on Other Factors
Recompute theManufacturing Costs
Reduce the Costs ofSupporting Production
Reduce the Costs ofAssembly
Reduce the Costs ofComponents
Goodenough
?
N
Y
Acceptable Design
Proposed Design
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3.Reduce the Costs of Supporting Production
• Reduction in no of parts- reduction in inventory.
• Reduction in assembly content- reduces no of workers
• Standardizing no of parts- reduces demands on engineering support and quality control.
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Minimize Systemic Complexity
• Production system consist- many suppliers, parts,people,processes.
• Needs to be monitered.Comlexicity is driven by design.
• Minimize Systemic Complexity (inputs, outputs, and transforming processes)– Use smart design decisions
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Error Proofing – Anticipate possible failure modes– Take appropriate corrective actions in the early stages– Use color coding to easily identify similar looking, but
different parts
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5.Consider the Impact of DFM Decisions on Other Factors
• Development Time• Development Cost• Product Quality• External Factors
– Component reuse– Life cycle costs- cost of toxic disposal. warranty period cost.
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Conclusion
• DFM is aimed at reducing manufacturing cost while simultaneously improving product quality,development time, and development cost.
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References
• Ulrich, K. & Eppinger, S. (2000). Product Design and Development. Boston, MA: Irwin McGraw-Hill.
• Product Design for Assembly, Geoffrey Boothroyd and Peter Dewhurst, 1991, Boothroyd Dewhurst Inc.
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Thank you