Design Guidelines and Checklist

Design Guideline Benefit

Minimize Number of Parts Fewer part and assembly drawings Lower volume of drawings and instructions to control Less complicated assemblies Lower assembly error rate Fewer parts to hold to required quality characteristics Higher consistency of part quality Fewer parts to fail Higher rate of reliability

Minimize Number of Part Numbers Fewer variations of like parts Lower assembly error rate

Eliminate Adjustments No assembly adjustment errors Higher first-pass yield Eliminate adjustable components with high failure rates Lower failure rate

Make assembly Easy and Error-proofed Parts can not be assembled wrong Lower assembly error rate Obvious when parts are missing Lower assembly error rate Assembly tooling designed in to part Lower assembly error rate Parts are self-securing Lower assembly error rate No “force fitting” of parts Less damage to parts; better serviceability

Use Repeatable, Well Understood Processes Part quality is easy to control Higher part yield Assembly quality easy to control Higher assembly yield

Choose Parts that can Survive Process Operations Less damage to parts Higher yield Less degradation of parts Higher reliability

Design for Efficient and Adequate Testing Less mistaking “good” for “bad” product and visa versa Truer assessment of quality; less unnecessary rework

Lay Out Parts for Reliable Process Completion Less damage to parts during handling and shipping Higher yield; higher reliability

Eliminate Engineering Changes on Released Products Fewer errors due to changeovers and multiple revisions/revisions Lower assembly error rate

— Has a cross-functional team meeting been held involving all relevant members? (List the members)

— Have all significant characteristics been identified?

— Are all processes to be used, capable?

— What are the Cpk values? (any <1.33 will necessitate change of designs/process)

— Has known history/experience been reviewed? (warranty data, design manual)

— Has a parts standardization analysis been done?

— Are possible tolerances the maximum that are possible?

— Are new assembly methods/processes agreed with manufacturing/

— Are materials and components suitable for the fabrication method chosen, e.g.. tolerance on flange flatness-is this achievable at low cost or is additional machining required?

— Has an Error Proofing for Manufactuirng analysis been completed for the design.

Design for Manufacturability Checklist

Design for Assembly Checklist

— Will the proposed design fit the space envelope given by the customer without violating minimum allowed clearances?

— Has welded access been ensured?

— Have mating surfaces been minimized?

— Has access for assembly tools been ensured?

— Is the project an International project?

— Are there different manufacturing processes in different involved plants?

— Has the lead manufacturing team leader been identified?

— Are the specified materials available in all the involved countries?

— Which plant is coordinating the ordering of the material?

Design for Assembly Checklist, Continued

Materials

— Do weld materials and process conform to the approved standards?

— Are anti-corrosion properties adequate to give desired service life in the given service conditions?

— Is the formability of the material appropriate for the manufacturing process?

— Is the cost of the material justified by its material properties/application?

— Are leakage specifications capable for applicable manufacturing process?

Recyclability

— Is E Glass filling feasible with automatic equipment (exhaust)?

— Does the proposed design materials used allow recyclability to required standards?

Assembly Strategy Guidelines

• Design product so that subsequent parts can be added to a “foundation” part.

• Design foundation part so that I has features that allow it to be quickly and accurately positioned.

• Design product so parts are assembled from above or from the minimum number of directions.

• Provide unobstructed access for part and tools.

• Make parts independently replaceable.

• Order assembly so the most reliable goes in first; the most likely to fail-last.

• Make sure options can be added easily.

• Ensure the product’s life can be extended with future upgrades.

• Use sub-assemblies, especially if processes are different from the main assembly.

• Purchase sub-assemblies assembled and tested

Fastening

• Use the minimum number of total fasteners.

• Use fewer large fasteners rather than many small fasteners.

• Use the minimum number of types of fasteners.

• Make sure screws should have the correct geometry so that auto-feed screwdrivers are used.

• Use slotted nuts only when necessary.

• Use self tapping screws when applicable

• Eliminate fasteners by combining parts.

• Minimize use of fasteners with snap together features.

• Consider fasteners that push or snap on.

•Specify proper tolerances for press fits.

Assembly Motions

• Fastened parts are located before fastener is applied.

• Assembly motions are simple. • Assembly motions can be done with one hand or a robot.

•Assembly motions should not require skill or judgment.

• Products should not need any mechanical or electrical adjustments unless required for customer use.

• Minimize electrical cables; plug electrical sub-assemblies directly together.

• Minimize the number of types of cables.

Test

• Product can be tested to ensure desired quality.

• Sub-assemblies are structured to allow sub-assembly testing.

• Testing can be performed by standard test instruments

• Test instruments have adequate access.

• Minimize the test effort spent on product testing consistent with quality goals.

• Tests should be given adequate diagnostics to minimize repair time.

Part Design

• Use standard parts.

• Standardize design features.

• Minimize the number of part types.

• Minimize the number of total parts.

• Standardize on types of linear materials and then cut and mark as needed. • Consider pre-finished material.

• Combine parts and functions into a single part.

Part Shape

• Adhere to specific process design guidelines.

• Avoid right/left hand parts.

• Design parts with symmetry.

• If part symmetry is not possible, make parts very asymmetrical.

• Use chamfers and tapers to help parts engage.

• Provide registration and fixturing locations.

• Provide drainage for parts that are plated or washed.

• Tolerances are the widest consistent with functional, quality and safety objectives.

Handling by Automation

• Design and select parts that can be oriented by automation.

• Design parts to easily maintain orientation.

• Use parts that will not tangle when handled in bulk.

• Use parts that will not shingle when fed end to end.

• Use parts that do not adhere to each other or the track.

• Specify tolerances tight enough for automatic handling.

• Avoid flexible parts which are hard for automation to handle.

• Make sure parts can be presented to automation.

• Make sure that parts can be gripped by automation.

• Make sure parts are within machine gripper span.

• Make sure parts are within automation load capacity.

• Make sure parting lines, spues, gating or any flash do not interfere with gripping.

Repair and Maintenance

• Provide ability for tests to diagnose problems.

• Make sure that most likely tasks are easy to perform.

• Ensure repair tasks use the fewest tools.

• Use quick disconnect features.

• Ensure that failure or wear prone parts are easy to replace with disposable replacements.

• Provide inexpensive spare parts in the product.

• Ensure availability of spare parts.

• Use modular design to allow replacement of modules.

• Ensure modules can be tested, diagnosed and adjusted while in the product.

• Sensitive adjustments should be protected from accidental change.

• The product should be protected from repair and damage.

• Provide part removal aids for speed and damage prevention.

• Protect parts with fuses and overloads.

• Ensure any sub-assembly can be accessed.

• Access covers which are not removable should be self supporting in the open position.

• Connections to sub-assemblies should be accessible and easy to disconnect.

• Make sure repair, service, or maintenance tasks pose no safety hazards.

• Make sure sub-assembly orientation is obvious or clearly marked.

• Provide means to locate sub-assembly before fastening.

• Provide unobstructed access for parts and tools.

• Make parts independently replaceable.

• Order assembly so the most reliable goes in first; the most likely to fail - last.

• Design products for minimum maintenance.

• Design self correction capabilities in to products.

• Design products with self-test capability.

• Design products with test ports.

• Design in counters and timers to aid preventative maintenance.

• Specify key measurements for preventative maintenance.

• Include warning devices to indicate failures.

Error Proofing

• Use standard parts.

• Design parts with symmetry.

• Make part differences very obvious.

• Make sure that the wrong part cannot go into the intended position.

• Make sure that the part cannot go into the wrong position.

• Design so parts can not be installed in the wrong orientation.

• Revisions to the product design are clearly conveyed to manufacturing and implemented.

• Design so that omissions can not happen.

• Design so that subsequent part installation will sense previous part omission. • Design so that omissions would be visually obvious.

• Design so that omissions would be easy to see during inspection.

•Eliminate process steps that depend on operator’s memory.

•Revisions and changes do get documented and implemented.

Error Proofing

• Design so assembly or process sequence does not matter.

• Design so assembly steps can not happen in the wrong order.

• Design so assembly or process sequence is intuitively obvious.

• Clearly specify assembly or process order.

• Design without the need for timed process.

• Eliminate operator timed process.

• Make all timed operations the same.

• Make different timing very different.