Design for Manufacturing

ByRaghavendra(093303)Gangadhar(093304)Bhagwath(093306)

Design for X Topics

Design for Manufacturing

Design for Production

Design for Assembly

Design for Recycling/Disposal

Design for Life Cycle

Prototyping

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

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.

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.

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

Estimate the Manufacturing Costs

Finished GoodsManufacturing System

Equipment Information Tooling

WasteServicesSuppliesEnergy

Raw Materials

Labor

PurchasedComponents

INPUT-OUTPUT MODEL OF A MANUFACTURING SYSTEM

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.

Elements of the Manufacturing Cost of a Product

Manufacturing Cost

OverheadAssemblyComponents

Standard Custom LaborEquipmentand Tooling

SupportIndirect

Allocation

RawMaterial

Processing Tooling

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.

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.

• 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 .

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

• EXAMPLE REPRESENTING CALCULATION OF MANUFACTURING COST

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

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.

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

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.

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

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

Reduce the Costs of Assembly

• Design for Assembly (DFA) index

• Integrated Parts (Advantages and Disadvantages)

• Maximize Ease of Assembly

• Consider Customer Assembly

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

Design for Assembly Index

DFA index =(Theoretical minimum number of parts) x (3 seconds)

Estimated total assembly time

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?

Integrated Part Design

Home Hot Water System Family Part

Comparison between Assembled & Integrated Parts

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

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

Consider Customer Assembly

• Customers will tolerate some

assembly

• Design product so that customers

can easily and assemble correctly

• Customers will likely ignore

directions

DFMA Example

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

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

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.

DFMA- An Improved Design

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

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

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

DFMA –Calculate Total Saving

Total Saving = Saving from Assembly Time Reduction + Saving from parts reduction = $0.95 + $13.71 = $14.66

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

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.

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

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

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.

Conclusion

• DFM is aimed at reducing manufacturing cost while simultaneously improving product quality,development time, and development cost.

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.

Thank you