[Arm-netbook] EOMA68 Computing Devices Update: 500 Micro Desktop PCB Assemblies
Luke Kenneth Casson Leighton
lkcl at lkcl.net
Sat Mar 23 16:56:25 GMT 2019
On Sat, Mar 23, 2019 at 3:56 PM Paul Boddie <paul at boddie.org.uk> wrote:
> Hello again,
hi paul good to hear from you
> It was nice to see this latest update on the project:
> "Just a brief update: Mike’s factory has assembled the 500 Micro Desktop PCBs,
> though the through-hole VGA connectors still need to be hand-soldered on.
> These are the simpler of the two boards, so all of the Micro Desktops are
> being done, whereas explained in a previous update, the more complex board,
> the EOMA68-A20, will only be done in a smaller test run of 100 at first."
> It must be satisfying to see all of this start to come together.
yeah - kinda weird as well, "um is that all it takes, you just have
to um wait for a factory to um make them??"
> On the topic of casings for the computer cards, I get the sense that there are
> no ready-made solutions for the outward-facing side of the cards, this despite
> most traditional PCMCIA/CardBus-profile cards exposing ports of different
> kinds (such as modems, network ports, like two cards I have from many years
> ago) and thus having similar requirements.
> I suppose 3D printing or some other creative casing solution isn't an option.
not a snowball in hell's chance. resin is too brittle, 3D printing
is far too inaccurate, and the plastic is extremely thin. 5 years ago
the ones we had stamped out for prototypes (laser-cutting i believe)
broke almost immediately.
> Injection moulding seems to be quite demanding,
it is. USD $10k is a not unreasonable budget... for soft tooling
that will produce decent pieces for the first 1,000 items, start to
wear out for the second 1,000 and produce shit thereafter.
that's $10k to $20k to *fail* to get it right, as in $10k to $20k
i do know someone in the UK who knows of a company that supplies
Formula 1 teams. their software is designed, thanks to the extreme
amount of work done for Formula 1, to *simulate* the injection mold
as a result, they *guarantee* that the molds that are CNC milled from
what their software outputs will work first time, and that includes
guarantees that bridges that the software recommends be put in place
to stop warping (against pull AND push pressures as the plastic cools
in the mold) will do the job.
my friend worked for a company that didn't use their software, to
manufacture a housing for an articulated lorry mirror. it was curved
(for aerodynamic reasons) so there was plenty of opportunity for
warping and stress / pressure fractures.
GBP 80,000 to ***FAIL*** to get it right.
the company had to then spend another GBP 45,000 on a second iteration.
injection-molding is a bitch.
so... i've instructed mike to tell the factory staff to get out the
cutters, and to snap off the front-facing part of the plastic.
at some point i may get made an extremely thin gluable / foldable
metal faceplate. an extremely thin metal sticker, basically, with the
holes for the MicroHDMI, MicroSD and USB-OTG.
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