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
MAKE IT EASY
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
your test plan will
be one of the most
Figure 2. Programming a test jig that was custom built to fit our PCB.