DFX, Management of Technological Innovation, KV Patri 1 DFX Design for Manufacture, etc....

DFX, Management of Technological Innovation, KV Patri

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DFXDesign for Manufacture, etc.

• Standardization

• DFX

• Group Technology

• Concurrent Engineering


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The best design

is the simplest one that works.

- Albert Einstein


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Precision Vs Cost

Cos

t

Precision


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Cost of design

Cos

t of

Pro

duct

ion


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Client + User + Designer + Maker

Client+

User

Designer+ Maker

Client+

User

MakerDesigner Designer

UserClient

Maker


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Standard v. One-off Design (Time Comparison)

Set-up

Production

Set-up

Production

Standard One-off


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Standard v. One-off Design (Cost Comparison)

Standard One-off

LaborFactory

Overhead

Development

Material

Testing

DesignTech. OHLabor

Factory OH

Development

Material

Special Tests


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Standardization• Development costs eliminated.

• Training costs reduced.

• Fewer mistakes.

• Start-up costs reduced due to familiarity.

• Less debugging. Therefore, higher quality, lower lead time, and higher productivity.

• Tooling costs reduced since tools are already available.

• Production quantities higher because same parts are reused. Hence economies of scale and easier just-in-time (JIT) arrangements.


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What can be standardized• Engineering drawing formats, conventions and units.

• Design features (e.g. hole sizes, bend radii, snap-fit tabs)

• Parts: do not design new part if an existing part suffices.

• Fasteners: Have list of preferred but limited variety.

• Materials: It is enough to have a satisfactory material - not necessarily the optimum.

• Commercial parts (from catalogues).

• Linear materials (e.g. wire)should be standardized by diameter and material but not by length.

• Modules: easy installation and substitution.

• Processes and tooling.


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Group Technology (1)• As the demand for product variety is increasing, there is a

need to find ways of making batch manufacture economical. GT enables this.

• GT concentrates on components or parts rather than end products. Products may vary, but they usually have many similar parts. If these parts are grouped together, one can obtain economies of scale at the part level although the batch sizes for the end products continue to be small.

• Without GT, different product sections may process similar parts differently. Effort is duplicated leading to loss of overall efficiency.

• A separate production cell manufactures each family or group of parts.


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Group Technology (2)• Classification: assignment of parts into groups or families.

• Coding: Allocation of identities (numeric codes with each code digit having a certain predetermined meaning) to these groups. Several popular coding schemes are available. A factory may adopt one of these or develop its own. Commercial software are available to facilitate manual or semi-automated coding (e.g. MICLASS).

• A product designer must be aware of the groups and utilize them. Do not unnecessarily create parts which fall outside existing families.

• Standardization is a benefit of GT.

• Modularization is an extension of GT


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The Need for DFM

ProductionUse

Full ScaleDevelopment

Concept Validation

ConceptFormu-lation

Product Lifetime

% of Lifetime cost

Committed

Spent


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What is ‘X’ in DFX?• Design for Manufacture• Design for Assembly• Design for Quality• Design for Reliability• Design for Serviceability/Maintainability• Design for Safety• Design for the Environment• Design for User-Friendliness• Design for Shorter Time-to-Market


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Design for User-Friendliness• Human Factors Engineering: designing products that are

easy to understand, safe, and in proper scale to the human form.

• Ergonomics: attempts to provide harmony between people and the products they use, to make products fit people well.

• User-friendly: ease of operation, reliability of results in the initial use and repeatedly afterwards, user satisfaction with operation.

• The above should be considered at the concept design stage.


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Design for User-friendliness Principles (1) • Fit the product to the users: Fit to user’s knowledge of the world

and habits. Higher readings on dials should be clockwise. Knobs must tighten when rotated clockwise. Activating forces required should be compatible with human strength.

• Simplify tasks: Control operations should be designed to minimize planning, problem solving and decision making on the user’s part. In personal computers, macros combine a complex series of key strokes into a single stroke.

• Make things obvious: Controls must simulate the arrangement of the mechanism. In a refrigerator/freezer, if a single thermostat controls the flow of air into the two chambers, then do not give two thermostat control knobs.

• Place controls for a function adjacent to the device to be controlled. E.g. place knobs for tape-player adjacent to the tape cartridge mechanism in a tape player. Centralizing controls in neat rows may be aesthetic but is not user-friendly.


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Design for User-friendliness Principles (2) • Use mapping: Controls must reflect or map the mechanism. Pushing

the car seat positioning lever up should raise (not lower) the seat.

• Utilize constraints: Make the system fool-proof by incorporating constraints: an automobile that will not go into reverse when the car is moving forward; a car door will not lock unless the door handle is depressed.

• Provide feedback: The effect of each action should be immediate, obvious and clear to the user: periodic clicking sound and dashboard flashing light when a turn signal is activated in a car; a push button switch is confusing because one does not know whether it will turn the motor on or off - a sliding or lever will not have this problem.

• Provide clear displays: clear, visible, interpretable, distinctive, legible, intelligible, easily readable, etc.; analogue displays are more user friendly whereas digital displays are more precise.


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Design for User-friendliness Principles (3)• Anticipate user errors: alarm sounds when a wrong

control is actuated.

• Avoid awkward and extreme motions for the user: keep wrists straight; keep elbows in lower position; minimize bending and twisting; provide adjustments (adjustable seat) to eliminate awkwardness; controls should provide the force or power needed internally rather than using user’s force or power; handles should have rounded corners and have high friction for gripping; etc.

• Standardize: use standardized controls that are familiar to the user rather than developing your own. In some cars, an upward motion of the lever starts the wind-shield wipers. In others, the opposite is true!


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Design for (Ease of) Manufacture (1)• Minimize the number of parts: this minimizes the amount of

manufacturing work. Electronic devices have been particular succesful in this regard. Integrated circuits combine thousands of elements into one component. According to Noyce’s law, the number of circuit elements (resistors, transistors, etc.) incorporated into a single micro-chip doubles every year (due to continued innovation). Use ICs as much as possible and put as many elements into the IC as possible.

• Minimize the number of manufacturing steps: Surface Mount Technology reduces the number of steps. Pin-in-hole systems need bending and trimming of leads, inserting in the PCB, and then crimping of the leads. Hence the speed of assembly currently is only 25 pieces per minute. SMT avoids these problems and is able to enable assembly at 80 piece per minute.

• Be sensitive to the impact of each design decision on manufacturability: Heat sinks may prevent overheating of circuit elements, but they also lead to cold solders.


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Design for (Ease of) Manufacture (2)• Minimize or eliminate adjustments: Mechanical adjustments of

potentiometers, etc. are labor-intensive. Eliminate them by utilizing voltage regulators, feedback loops, etc. Positional adjustments of components are also expensive. Footprint designs of SMT boards should provide space for a good solder joint even if the part shifts slightly.

• Be aware that the objective wide spacing of components for manufacturability conflicts with the objective of ‘fine pitch’ to achieve miniaturization.

• Standardize: Standardize PCB dimensions so that standard fixtures can be used during wave soldering, cleaning, etc. Standardize the location of tooling holes and board thickness. When smaller boards suffice, design them such that multiple quantities can be cut from a larger standard board.

• Minimize unnecessary variety: Different hole sizes require drill changing.


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Importance of DFABoothroyd and Redford 1968

Experience shows that it is difficult to make large savings in cost by introduction of mechanized assembly in the manufacture of an existing product. In those cases where large savings are claimed , examination will show that often the savings are really due to changes in the design of the product necessitated by the new process. … Undoubtedly, the greatest cost savings are to be made by careful consideration of the design of the product and its individual component parts.


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Design for Assembly (1)• The optimum design is different for different methods of

assembly: manual assembly, hard automation with fixed tooling (for large quantities), flexible assembly (using robots) for medium batch sizes, etc.

• Minimize the number of parts: This reduces the number of assembly operations. According to Boothroyd and Dewhirst:

Design efficiency = (No. of parts) x 3s/ Assembly time (s)

Assembly time = sum of (handling + insertion) times.

Each part should be examined to see if it can be eliminated or combined with other parts. Two parts need to be separate only if there is relative motion between them, need to be of different materials, or it is necessary for assembly.


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Design for Assembly (2)• Combine parts: Incorporate hinges into plastic - plastic

can bend. Use internal springs - the functional metal part itself acts as a spring. Eliminate fasteners - use snap fits. Incorporate elements such as guides, bearings and covers into plastic parts - remember plastic has low friction. Put electrical and electronic components in one location and consolidate them. One PCB is preferable to several in several locations. A light switch and ventilation switch on the same mounting plate is preferable.

• Standardize designs and components.

• “Once a part is oriented, never lose that orientation.”: Assemble it, move it and ship it with its orientation retained.


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Design for Assembly (3)• Use subassemblies: Use modules (a PCB is a module).

• Avoid too many subassemblies at one time.

• Design parts so that they cannot be inserted incorrectly.

• Avoid the use of flexible parts. They can get tangled during handling.

• Avoid slippery parts. They are difficult to insert.

• Use layered, top-down assembly.

• Avoid connecting cables by using direct plug-in boards.

• Avoid switches and jumpers by configuring in software.

• Use consistent design strategy. Assembling SMT boards alone is easier than when SMT and PIH are mixed.


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Concurrent Engineering (1)• The traditional “Over the wall” approach: Designers

and manufacturing engineers do not communicate about the design. Design documents are transmitted to manufacturing without a pre-release review by manufacturing engineers.

• An improvement - The Sign-off Procedure: Manufacturing engineers approve and accept the design after it is completed but before it is released to production.

• Concurrent Engineering: Designers and manufacturing engineers work together on the design at the same time.

• Four Key Elements of Concurrent Engineering:


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Concurrent Engineering (2)1. Concurrence: Product and process design take place at the

same time.

2. Constraints: The limitations and capabilities of the available manufacturing processes are considered during the design phase itself. In recent times, software for evaluating specific DFX features are available. Hong Kong hasn’t yet learnt to use any.

3. Co-ordination: Products and process requirements and other objectives are closely co-ordinated during the design process (itself).

4. Consensus: (A Confucian value!) The full concurrent engineering team participates and agrees with major product design decisions.


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Concurrent Engineering (3)• I leave it to you to describe the advantages of CE. But

what are the risks associated with CE?

• Teams are more difficult to manage than individuals. Team meetings can take excessive time. Achieving team work may require delicate and diplomatic approach.

• Not all good designers are team players.

• Maybe, CE can be achieved without team work. May be designers can use DFX computer programs to evaluate their designs.

• There can be much resistance to change to CE (why?).

DFX, Management of Technological Innovation, KV Patri 1 DFX Design for Manufacture, etc....

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