[gta02-core] New shields

Werner Almesberger werner at openmoko.org
Thu Sep 3 23:55:09 CEST 2009

Rask Ingemann Lambertsen wrote:
>    Assuming 20 pairs of shields (or 40 identical ones):

So he considers removable shields basically just as two normal
shields ? That's interesting. I would have thought they're a bit
harder, due to the complex bending and the dents.

> Etching		DKK 5000 (EUR 672) *
> * Same price for 100 pairs of shields if they fit on a sheet.
> Laser cutting	DKK 3000 (EUR 403)

Good, so it's not a big-ticket item for commercial prototypes.

> If the shields
> have bend lines (material thickness reduction) on the inside, it shouldn't
> be a problem to bend them over an edge.

Great !

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

Hmm, did he mention any specific aspect of the geometry ? All I could
think of is the tool diameter. If we assume 0.2 mm thickness, you
should be able to use a 12 mil endmill with a length of 0.45 mm and a
diameter of 0.3 mm. So that would define the smallest hole, the radius
of inner corners, and how deep you have to cut into a corner to fit a
rectangle [1].

[1] http://people.openmoko.org/werner/cnc/corner.ps

Did he mention anything about materials ? I.e., will anything that can
be soldered do or are there special requirements ?

>    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.

Now that's the kind of price I like :-) But the can is also fairly

Thanks a lot !

- Werner

More information about the gta02-core mailing list