[Arm-netbook] microdesktop casework as DXF files for laser-cutting

Luke Kenneth Casson Leighton lkcl at lkcl.net
Thu Mar 30 13:14:36 BST 2017

crowd-funded eco-conscious hardware: https://www.crowdsupply.com/eoma68

On Thu, Mar 30, 2017 at 4:34 AM, Normand Chamberland <gemnoc at gmail.com> wrote:
> Hello,
> Thanks Mark. Just to give some context to these files:
> - This is a first draft. Even though Luke wrote he'd take care of it, I had
> already started the process with Mark last week.

 not a problem, let's use (keep going with) both approaches, each of
us will spot different things, by using different tools.

> I didn't spend more than a
> couple of hours on this last night and I didn't calculate precise
> clearances, the PCB as per Luke's STL model will fit but there may be too
> much or not enough clearance along X and Y axes (X and Y being parallel to
> the ground).

 what i'll do is 3D print all the parts from DXF-extrusion using
pyopenscad, and double-check them that way.

> - It requires 8 layers of 3mm wood panels, overall dimensions of casing
> (without screws) being 111mm wide by 115mm deep by 24mm high. Consequently
> the PCB is near flush to the front and rear of the casing.
> - For 3 layers, the panels are separated into a left side and a right side.
> 4th and 5th layer (from bottom) are identical.

 see my notes from overlapped-message.

> - If it was judged acceptable for the card reader to be exposed underneath
> the casing, the bottom layer could be removed to reduce the total number of
> layers to 7.

 6 if they're shifted... nehh let's not do that.

> - The PCB board sits on the 2nd layer, not having seen any picture of this
> board I don't now if components protrude underneath it (I know nothing about
> electronics). It may not be viable to have it sit on a flat surface that
> way.

 it's not.  the top edge (along the top side of the TOP layer) has no
components so can be used to hold down the PCB, likewise the bottom
edge (along the bottom side of the TOP layer).  but it's pretty tight:
about 1.5mm as you can see from where you've done an overlap running
alongside the DCjack.  you can't make it much more than that as you
end up running into the 20-pin header and 3.3v and 5v PMIC components.
looking at component placement you've actually probably got about 1mm
along the bottom edge, might have to make a C-shape (cut-out along
most of that bottom edge)

> - There are 11 lasercut wood pieces. That's a lot. Is the layered design
> definitive

 not really.  i do like it however.  i did consider a hybrid
3d-printed and (thinner) plywood technique, similar to for the laptop.

> (I guess that's what the backers will expect since that's what's
> shown on Crowd Supply), or could this be discarded in favour of a new design
> optimizing fabrication? A more classic box with dovetail joints may be less
> expensive, and allow more control on the fitting of the board. Something
> akin to
> https://images-na.ssl-images-amazon.com/images/I/91H9TOVowCL._SL1500_.jpg
> (but hopefully with better looks!)

 honest reaction: blegh.  you can't do curves, you can't ever hide the
dovetail joints no matter how hard you try.

> Luke, I know you prefer working with OpenSCAD,

 pyopenscad.  can't stand the scad "language".  i know people love it
who use it but for goodness sake writing your *own language* in a
specialist (small) field is never going to end well.  pyopenscad
treats scad as "not-for-reading machine code" which is as it should

> I was able to export my
> FreeCAD file to .csg which is a format recognized by OpenSCAD, but the
> generated text file is over 1MB and contains a series of multmatrix and
> polyhedrons with an unmanageable number of coordinates. Let me know if you
> want to have a look at it anyway.

 i have freecad installed so can view it - i just can't get my head
round editing.  too obtuse!

 btw are you having difficulties with rendering at all?  every 30-60
seconds of continuous rotating i get a "hang" - it's a known bug
somewhere in opengl / x11 - which can only be "fixed" by doing
ctrl-alt-f1 followed by ctrl-alt-f7.

 vincent full link (corrected) http://hands.com/~lkcl/kde_tablet/3dcase


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