Shipulski On Design

Ask a company or team to do DFMA, and you get a great list of excuses on why DFMA is not applicable and won’t work. Product volumes are too low for DFMA, or too high; product costs are too low, or too high; production processes are too simple, or complex; production mix is too low, or too high.  That’s all crap – just excuses to get out of doing the work.  DFMA is applicable; it’s just a question of how to prioritize the work.

To prioritize the work, take a look at product volumes.  They’ll put you in the right ballpark. Here are three categories, low, medium, and high volume:

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Low Volume – 10 to 500 units per year

“Our volumes are too low.  We can’t do DFMA.”  Yes you can.  Here’s how to prioritize:

Eliminate fasteners and connectors. Products in this category are riddled with nuts, bolts, and washers.  Zero thought has been put into manufacturing – none.  Nothing fancy here, just eliminate fasteners with good joint design.  Joints have twice the number of required bolts, so take some out.  Also, try nuts with integrated star washers.  Do DFA on the highest part count subassembly to get rid of some parts and learn the tool. Do DFM on your most costly part.  Yes, one single part.  You’ll be tempted to do more, but don’t.  That’s not where the money is.

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Medium Volume – 500 to 5000 units per year

“Our volumes are too low and too high. (How can it be both?) We can’t do DFMA.” Yes you can.  Here’s how to prioritize:

Eliminate fasteners and connectors. Products in this category are riddled with nuts, bolts, and washers – use good joint design.  Do DFA on the whole product (all the subassemblies) to design out parts.  Take a special look at the wire harness if you have one (lots of connectors and wires) or create one from the loose wires. Add features to the remaining parts to reduce fasteners and connectors, e.g., tabs and slots in sheet metal.  Create features in the parts to aid in assembly – alignment, anti-rotation, and poke-yoke.  Do DFM on your five most costly parts.  Yes, five parts.  You’ll be tempted to do more, but don’t.  That’s not where the money is.

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High Volume – 10,000+ per year

“Our volumes are too high.  We can’t do DFMA.”  Yes you can.  Here’s how to prioritize:

Eliminate fasteners and connectors. Products in this category are riddled with nuts, bolts, and washers.  To start, do everything described in the Medium Volume category. You must use new manufacturing technologies, such as molding and forming, to further reduce part count.  Add features in parts to further improve assembly and add some process automation. Do DFM on your 10 most costly parts.  Yes, 10 parts. You’ll be tempted to do more, but don’t.  That’s not where the money is.

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The volume numbers for the categories are not absolute, they’re just guidelines. (For example, some companies in the Medium Volume category use molding to eliminate parts. Soft tooling can reduce tooling costs enough to make it work.)

The excuses and static thinking are powerful obstacles to overcome.  But with 50% savings on the line, it’s worth pushing through them.

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