FORUM LET’S GET PHYSICAL

instructions posted at workstations on the assembly line (see Figure 1).

We learned a few concrete design lessons that can reduce difficulties during assembly. For example, we now try to design asymmetrical attachment points (e.g., screw holes, snap fits) to ensure that there is only one way to attach one part to another.

The most important thing we could have done was to anticipate the PCB assembly process. Depending on the PCB, assembly may require some or all of the following steps: surface mount placement (first side), solder reflow in an oven, surface mount placement (second side), reflow (again), manual placement of through-hole components, wave soldering (this involves a wave pool of molten metal!), and finally, hand soldering if necessary.

If you can fit all your components on one side, you’ll save a couple steps. If you need wave soldering, you’ll have to orient your through-hole components so they’re less likely to be knocked askew by that deluge of melted solder.

If you can rely on automated processes and minimize manual soldering, you’ll save labor costs and reduce your error rate. To the inexperienced (as we were), this can sound like an intimidating list of considerations, but early factory visits can teach you a lot about these processes, especially if you are thinking ahead about what kind of impact it should have on your design.

TESTS ARE THE BEST

No matter how well you design your product, there will be a small percentage of errors in production that need to be caught and fixed. For every PCB you design, you’ll need to make another custom PCB to connect to and test it. You’ll need to make a test jig that runs those tests quickly and reliably.

mind and aimed for fewer different materials and manufacturing processes. As interaction designers, we’re already familiar with the notion that design must work creatively with constraints; design for manufacture introduces a new family of constraints related to an entire system of sourcing and assembly.

MAKE IT EASY
TO ASSEMBLE

While you were prototyping, you probably knew that prototype well and did a lot of work with your own hands.

When it comes to manufacturing, however, every piece that you have to artfully jiggle into place will present a problem on the assembly line.

While still prototyping, consider what it means for your device to be assembled by a stranger who may not know or care much about it, who might be bored or sleepy, or who might be thinking of finding a new job. Once you decide to manufacture a product, your documentation of the assembly process will be incredibly important. Expect to see some of your photographs and (translated)

Figure 1. Printed circuit boards assembled and ready for manual inspection. Note the assembly instructions posted on the upper right.

Along with your
assembly instructions,
your test plan will
be one of the most
important pieces
of documentation
you write.

Figure 2. Programming a test jig that was custom built to fit our PCB.