PQP系列之DFM(Design For Manufacturing)
Design For Manufacturing
Why to use: Optimize the feasibility and manufacturing cost in volume production. It is a critical analysis to the product design to see if it can be realized in factory.
When to use: Transfer a product from laboratory or design to factory.
Where to use: NPI phase, product transit.
Who use: Manufacturer.
How to do: Finding a robust and cost effective design from a manufacturing perspective in this structured way (DFM) and submit the report to designer (customer).
How much: The findings and proposed solution should be less cost and no negative impact to quality and delivery.
When we outsource any component to suppliers, a DFM is required; and, when suppliers show insufficient capacity and/or capability to meet our demand, I’d challenge them why not do the DFM well. DFM, a necessary tool to anyone who committed his customer he can produce the product properly and wholly meet the specification.
Once I had a supplier who provides a copper sheet to me. Everything is working so well, the sample passed approval and the specification datasheet was signed. When we started mass production, unfortunately, almost all components failed on poor flatness. According to the drawing, the flatness spec is max. 10mm. It is out of supplier’s capability, and as supplier explained, the required spec is even larger than the flatness of raw material. The approved sample was made by manual flatten after stamping. Oh my God, that case almost killed my product. Supplier cannot meet our demand, so we have to change the whole milestone. It is a lesson learnt. I talk it here to remind all of you how critical this tool is. OK, let’s see how to do DFM well.
The first action is, please work out a team. The members are considered include, Production Engineer, Sourcing, Buyer, Quality Engineer, Planner, Supervisor, Mechanical Engineer, Testing Engineer. They can help you to analyze the specification in different views.
The second is, try to explode the product specification. For simple one, you can skip this step, but for complicated ones, you have to consider it. For a system, please flow this way: explode system to sub-systems, critical parts, and then to major parts, and then to units. You even need to disassemble it until all units are the lowest level, for example, a pin, a sheet, a shaft, etc.
The third is, to have analysis part by part. The analysis can be divided into 5 aspects: machining, moulding/tooling (if applicable), material, testing and standardization. Following are the details to present these aspects:
1. Machining: capacity, tolerance design, surface treatment, finish and cosmetic requirement, PCB layout and pad design, measurement, extrude angle, shrinking rate, best process design, etc.
2. Moulding/tooling: mould (stamping, casting, fixture) design, tooling (stencil, assembly jigs) design, marking, tolerance adjustment, etc.
3. Material: material limitation, material characteristics (any suggestion), etc.
4. Testing: testing method and process, factory setting, testing fixture design, etc.
5. Standardization: if something can be standardized to make performance better?
Finally, have the analysis in a suitable report form. The design problems and/or ambiguities that make manufacturing the part difficult / impossible / expensive in mass production should be identified with respective proposal. The report should be structured and easy to read. And then, submit the report to customer for review.
A good DFM can secure the transit process running smoothly and fewer risk occurring in downstream. It can demonstrate supplier’s capability to produce the product in volume retaining the demanded quality level, and also is to provide a structured approach for suppliers to communicate design / manufacturing requirements. Suppliers still can influence the design and requirement for the product through DFM with his professionalism, which is almost impossible later.
A bad DFM would kill a product and no one knows what problems may occur later. When you started mass production, you may got call from suppliers, ”Excuse me, I found the tolerance is too tighten, and we got almost 80% failure. Sorry, I cannot meet your demand this week.” “I wonder if you can loosen this spec because we really cannot do that.” My God, why not check this problem out in transit phase? Now the forecast is confirmed, all materials are ready except this one. It is my nightmare. And you?
Following is an example of a DFM-report
DFM <Design for manufacturing> review of resonator
Product number: XXX/XXX Version: XXX
Specification: no. 007 rev. A
Present: Mr. Product Engineer, Ms. Quality Engineer.
1. Tolerance design:
We have gone through every single measurement and tolerance on your drawing 007 rev. A. All but one tolerance width is comparable to other products we are producing.Dimension <123> 13,2 ±0,1 mm. The problem is to control tolerance width ±0,1 after the casting.
Proposal: Increase the tolerance width to ±0,15
2. Measurement design:
The measure to this dimension is more difficult and the datum is not standardized with others.
Action: change the datum from A to B.
3. Moulding design:
Our mould design engineer suggests an additional block on surface <C>. This must be discussed further since it might cause a mark on the opposite surface <E>.
4. No problems with other drawing requirement. Thanks!
仓促之间写完,谬误之处,欢迎您的指正.也不任欢迎互相交流.
xg_goo#163.com
Why to use: Optimize the feasibility and manufacturing cost in volume production. It is a critical analysis to the product design to see if it can be realized in factory.
When to use: Transfer a product from laboratory or design to factory.
Where to use: NPI phase, product transit.
Who use: Manufacturer.
How to do: Finding a robust and cost effective design from a manufacturing perspective in this structured way (DFM) and submit the report to designer (customer).
How much: The findings and proposed solution should be less cost and no negative impact to quality and delivery.
When we outsource any component to suppliers, a DFM is required; and, when suppliers show insufficient capacity and/or capability to meet our demand, I’d challenge them why not do the DFM well. DFM, a necessary tool to anyone who committed his customer he can produce the product properly and wholly meet the specification.
Once I had a supplier who provides a copper sheet to me. Everything is working so well, the sample passed approval and the specification datasheet was signed. When we started mass production, unfortunately, almost all components failed on poor flatness. According to the drawing, the flatness spec is max. 10mm. It is out of supplier’s capability, and as supplier explained, the required spec is even larger than the flatness of raw material. The approved sample was made by manual flatten after stamping. Oh my God, that case almost killed my product. Supplier cannot meet our demand, so we have to change the whole milestone. It is a lesson learnt. I talk it here to remind all of you how critical this tool is. OK, let’s see how to do DFM well.
The first action is, please work out a team. The members are considered include, Production Engineer, Sourcing, Buyer, Quality Engineer, Planner, Supervisor, Mechanical Engineer, Testing Engineer. They can help you to analyze the specification in different views.
The second is, try to explode the product specification. For simple one, you can skip this step, but for complicated ones, you have to consider it. For a system, please flow this way: explode system to sub-systems, critical parts, and then to major parts, and then to units. You even need to disassemble it until all units are the lowest level, for example, a pin, a sheet, a shaft, etc.
The third is, to have analysis part by part. The analysis can be divided into 5 aspects: machining, moulding/tooling (if applicable), material, testing and standardization. Following are the details to present these aspects:
1. Machining: capacity, tolerance design, surface treatment, finish and cosmetic requirement, PCB layout and pad design, measurement, extrude angle, shrinking rate, best process design, etc.
2. Moulding/tooling: mould (stamping, casting, fixture) design, tooling (stencil, assembly jigs) design, marking, tolerance adjustment, etc.
3. Material: material limitation, material characteristics (any suggestion), etc.
4. Testing: testing method and process, factory setting, testing fixture design, etc.
5. Standardization: if something can be standardized to make performance better?
Finally, have the analysis in a suitable report form. The design problems and/or ambiguities that make manufacturing the part difficult / impossible / expensive in mass production should be identified with respective proposal. The report should be structured and easy to read. And then, submit the report to customer for review.
A good DFM can secure the transit process running smoothly and fewer risk occurring in downstream. It can demonstrate supplier’s capability to produce the product in volume retaining the demanded quality level, and also is to provide a structured approach for suppliers to communicate design / manufacturing requirements. Suppliers still can influence the design and requirement for the product through DFM with his professionalism, which is almost impossible later.
A bad DFM would kill a product and no one knows what problems may occur later. When you started mass production, you may got call from suppliers, ”Excuse me, I found the tolerance is too tighten, and we got almost 80% failure. Sorry, I cannot meet your demand this week.” “I wonder if you can loosen this spec because we really cannot do that.” My God, why not check this problem out in transit phase? Now the forecast is confirmed, all materials are ready except this one. It is my nightmare. And you?
Following is an example of a DFM-report
DFM <Design for manufacturing> review of resonator
Product number: XXX/XXX Version: XXX
Specification: no. 007 rev. A
Present: Mr. Product Engineer, Ms. Quality Engineer.
1. Tolerance design:
We have gone through every single measurement and tolerance on your drawing 007 rev. A. All but one tolerance width is comparable to other products we are producing.Dimension <123> 13,2 ±0,1 mm. The problem is to control tolerance width ±0,1 after the casting.
Proposal: Increase the tolerance width to ±0,15
2. Measurement design:
The measure to this dimension is more difficult and the datum is not standardized with others.
Action: change the datum from A to B.
3. Moulding design:
Our mould design engineer suggests an additional block on surface <C>. This must be discussed further since it might cause a mark on the opposite surface <E>.
4. No problems with other drawing requirement. Thanks!
仓促之间写完,谬误之处,欢迎您的指正.也不任欢迎互相交流.
xg_goo#163.com
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