[gta02-core] New shields

[Rask Ingemann Lambertsen]

On Mon, Aug 31, 2009 at 10:30:30PM -0300, Werner Almesberger wrote:

> Perhaps the most interesting information would be:
> 
> - in general, how much does it cost to make the sort of shields we
>   have in GTA02 (maybe just show him the FreeRunner) in prototype
>   quantities.

   Assuming 20 pairs of shields (or 40 identical ones):
Etching		DKK 5000 (EUR 672) *
* Same price for 100 pairs of shields if they fit on a sheet.
Laser cutting	DKK 3000 (EUR 403)

   Thus he expects etching to be cheaper than laser cutting in quantities of
about 100 pairs or more.

   Add DKK 2000 (EUR 269) if you also want the shields bent. If the shields
have bend lines (material thickness reduction) on the inside, it shouldn't
be a problem to bend them over an edge.

   Wire electrical discharge machining[1] was also mentioned as a
possibility, but holes in the design will be inconvenient because of the
need to thread the wire through the holes.

> - in general, is this kind of shields a good choice or are there
>   better ones ? It's intentional that most of the shields are
>   removeable, and such shields are more expensive than non-removeable
>   ones.

   If forgot to ask about this, but the main difference I see is that
removable shields are two pieces each and that you will be able to fit fewer
of them per sheet of metal.

> - if he'd have to DIY, how would he do it ? Assume the availability of
>   a 3D CNC mill and shops that sell thin metals sheets, particularly
>   brass.

   Lars said he's not familiar with CNC mills, but thinks that the geometries
will cause problems. I think it would be worth trying.

   Finally, I asked about existing shields that you could simply order 20
of. Lars mentioned a 18 mm x 18 mm x 3.6 mm shield at DKK 4.77 (EUR 0.64) a
piece. I forgot to ask if the lid on that one is removable.

-- 
Rask Ingemann Lambertsen
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