Anelok: the 2015 case 2/2: first impressions

Werner Almesberger werner at
Mon Jan 19 23:21:08 UTC 2015

I first did a trial run for the bottom part on a piece of MDF. The
result was too fuzzy to even look much like a case, which is more or
less what I expected, but it confirmed that the basics were right
and the mill wouldn't go off and drill holes into itself.

I then went straigh to acrylic and the top part. This is what the
model looks like:

This kept the mill busy for some three hours, but the result looks
nice. Of the two 2014 boards (#1 and #2) I have made, #2 is in the
2014 case and #1 didn't have a case yet. You've already seen this
board in July/August:

Now it was time to cut board #1 in half and to put it into the new
top shell. This is the result:

As one can see, the main PCB does fit. It doesn't have a lot of
wiggle room, but that's intentional. Here is the vertical stacking:

The display is held laterally by a raised border and the rounded
barriers (one prominently in the foreground, the other one invisible
under the PCB in the background). It hangs loosely between PCB and
the window because I haven't put anything between PCB and display to
gently push it against the case.

Then there is a rim upon which the PCB rests. This is followed by a
rim that touches the sides of the PCB. And then there's the outer
wall into which also the bottom part slides.

This looks all very pretty, but there are problems.

First of all, the sidewall seems quite low. Here it is in more

Its height is 0.8 mm in the model, i.e., as much as the PCB, but it
looks more like 0.5 mm in real life. This needs more examination.

Then there is a blooper in the model:

The sub-board proudly sits on the rim that supports the main PCB but
that rim should not exist in the area of the sub-board. I simply
missed that one. Alas, this means that this case won't be usable for
putting the Anelok circuit inside.

But this mishap will make it an excellent candidate for experimenting
with aggressive window-polishing techniques. Nothing is wasted :)

The opening for the switch looks great:

Maybe it's a bit too narrow (in a future consumer version, there
should be a piece of plastic on the knob, so that the user never
touches the switch directly, but I'll keep things raw and simple in
prototypes), but that can be easily adjusted.

USB was less fortunate:

This should still work without problems, but the receptacle really
ought to be better centered.

There is a similar positioning error in the cut-out for the silo

The last problem is one of the PCB, and something I expected to
happen. It's caused by me not taking into account the real shape of
the lanyard cylinder when designing the PCB outline a long time ago:

The original PCB has right angles in these corners. I had to clip
off about 1 mm to make room for the curve the mill produces. Again,
something that can be easily corrected.

By the way, the asymmetry between the upper and the lower corner
is not a bug but the result of me using 2014 PCBs in the widened
2015 case. This makes the case 0.5 mm "too wide" on the top and the
bottom, and since the lanyard hole follows the case outline and not
the PCB edge, there is this gap in the Y direction.

In order to properly support the 2014 PCB, this case has thicker
walls and widened rims where the case sandwiches the board. Oh, and
I didn't mention the FPC. It went into the increased space without
even a hint of a problem. So the widening accomplished its goal
perfectly :)

- Werner

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