Anelok: refining the wedge

Werner Almesberger werner at almesberger.net
Sun May 31 05:06:29 UTC 2015


Bas Wijnen wrote:
> The feature size and positioning accuracy are not actually what causes
> most problems with prints; it's the deformations when the object cools
> (mostly during printing).

Hmm, maybe a quick hypothetical example could help to give me a
better idea of how good or bad things would be.

Let's assume we have a PCB of exactly 50.0 x 40.0 x 1.6 mm. Now if
we wanted to print a half-case with the following characteristics:

- bottom thickness: 1.5 mm
- sidewall thickness: 1.5 mm each
- gap between PCB and sidewalls: 0.2 mm on each side
- sidewall height: approx. 5 mm (from floor)

Something like this:
http://downloads.qi-hardware.com/people/werner/anelok/tmp/half-case/hc.png

Python script for FreeCAD:
http://downloads.qi-hardware.com/people/werner/anelok/tmp/half-case/hc.py

STL:
http://downloads.qi-hardware.com/people/werner/anelok/tmp/half-case/hc.stl

Also let's assume a moderate amount of post-processing. E.g.,
sanding, trimming any isolated flaws, maybe some surface treatment.

Based on your experience, would your expect  ...

- the PCB to fit ?
- the PCB to be able to bounce around ?
- the floor to be level ? (I.e., not bent or warped.)
- If you held the piece on one side and applied a ~100 g force on
  the other, would it bend by more than, say, 2 mm ?

  (I get something like 1-2 mm with an Anelok bottom case half,
  made of acrylic. The flexing of the assembled case is noticeable
  but tolerable. Also, the wedge-shaped case would be stockier and
  thus suffer less flexing, all other things being equal.)

Oh, and when you make parts that should mate, does the usual "nose"
on one side and undercut on the other work well with PLA and ABS ?
Or do such things tend to come apart easily ?

- Werner



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