Poka yoke, or Why a solid design database matters

Poka yoke, or Why a solid design database matters

So we have had a very hot summer thus far here in southwest Virginia. Not that it was any cooler or less humid when I was in Shenzhen for six weeks in late spring, but given that I am renovating an old home without central air while living in it, I am allowed to comment on the weather.

The old A/C units that came with the house were not up to the task, so rather than broil while we rip up half the house to install central air, off we go to the appliance store to buy some new window units. We bought several of the same model, and while I have never thought about an A/C unit needing a remote control, this model had remotes.

After I got them installed, we noticed a tiny little design flaw in the remote. See if you can spot it.

Poka yoke, or Why a solid design database matters

Were I a dedicated blogger, I would take one of these apart to show you the interior, but now that I have the wonder of a remote control for my A/C, I am not going to risk breaking one of these just for you. I prefer to luxuriate in my new found comfort like a stereotypical lazy American, thank you very much.

Were I to take the remote apart, you would see that the buttons are molded as one piece. Molding the buttons as a solid piece is the standard way of doing it, but by creating a part that was symmetrical (likely just a plain rectangle), the designer created a failure mode – the assembler could put the parts together backwards. What the designer should have done was analyze what could go wrong with the design – could it be assembled backwards? – and keyed one end so the the part was not symmetrical. Perhaps there is an internal feature that one end of the button strip could have been molded to mate with. Many companies I’ve worked with use the formal Failure Modes Effects Analysis (FMEA) process, and it is a great tool if you have the discipline to use it. The Japanese refer to this practice as“poka yoke” (mistake proofing), but often still translated as “idiot proofing”. I’m not a fan of that translation, because who’s the idiot – the guy would made the momentary mistake of putting it in backwards or the designer who created a flawed product?

PassageMaker often gets classified as a China sourcing company. While we do source products in China, that is only the smallest part of what we do. We are primarily a contract assembly company (with that label encompassing vendor coordination, inspection, the actual assembly, packaging, logistics, VAT rebates, etc.). And I can tell you that we see MANY severely flawed design databases, drawings that appear to have been made by someone who gave no thought to how to put the thing together.

If you are going to spend the money to have something made in China, a dollar’s worth of poke yoke is worth hundred times that in money saved doing inspections, warranty claims and just the general embarrassment of sending a functional part out into the world that is nonetheless defective.

In our Endorsed Service Provider network, we recommend two design engineering firms. Contract Engineering Services is based in Virginia, USA, and VentureTech is Dutch-owned, based in Shenzhen. Both do a fine job for our clients and even if you do your own engineering, I strongly urge you to learn from the lesson above and try an mistake proof your design. It might feel good to blame the Chinese assembly line worker, but who really made the mistake?

Your thoughts?

0 replies

Leave a Reply

Want to join the discussion?
Feel free to contribute!

Leave a Reply

Your email address will not be published. Required fields are marked *