Anelok: a dummy case for AAA (2/2)

Werner Almesberger werner at almesberger.net
Sun May 24 00:00:21 UTC 2015


This all looks nice so far. However, the path to get there turned out
to be a lot stonier than I had expected. The problem is that my mill
is acting up badly along the Z axis, reducing the depth by up to
almost half of what the CAD model says.

Here is an example. This is what the slices look like in FreeCAD:

http://downloads.qi-hardware.com/people/werner/anelok/tmp/dummy-aaa/dummy-aaa-cad.png

And this is what came out:

http://downloads.qi-hardware.com/people/werner/anelok/tmp/dummy-aaa/dummy-aaa-sizes.jpg

The nominal thickness of 17.5 mm yielded pieces between 9.3 and 10.3 mm.
The jump from ~10 to ~9 mm may have been caused by setting the depth of
the bottom such that the mill would cut well below the floor of the upper
MDF block. By the way, double-sided adhesive tape and MDF form an
amazingly strong bond, making it quite an effort to pick the slices from
the block after milling.

The depths of the cut-outs for screw heads are even more puzzling:

Nominal		Measured	Factor
--------------- --------------- ---------------
 5 mm		3.7-4.0 mm	74-80%
 8 mm		 5.0 mm		63%
10 mm		5.6-6.3 mm	56-63%

Just weird.

- Werner



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