[Arm-netbook] Solid wood corner prototype

[Tor, the Marqueteur]

Thought I'd give a try at how a solid wood version would come out. Here
is the result of about 45 minutes prototyping with a piece of 3/8" Cherry
I had lying around.

A couple notes: The 5/64" (.078", 1.98mm) bit has some tendency to
wander, as can be seen in the holes. I also goofed the measurement so
these are 11/16" instead of 9/16" wide. I didn't notice that until I was
nearly done, and figured that since they weren't actually going to be
used it didn't matter.

I also didn't add the slot for the PCB, mostly because I wasn't sure of
the size, and I didn't have the appropriate cutter lying close by. I
have a couple thoughts on that.

Tor

[Luke Kenneth Casson Leighton]

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


On Sun, Apr 30, 2017 at 7:44 AM, Tor, the Marqueteur

Post by Tor, the Marqueteur
Thought I'd give a try at how a solid wood version would come out. Here
is the result of about 45 minutes prototyping with a piece of 3/8" Cherry
I had lying around.

those look _great_.

Post by Tor, the Marqueteur
A couple notes: The 5/64" (.078", 1.98mm) bit has some tendency to
wander, as can be seen in the holes. I also goofed the measurement so
these are 11/16" instead of 9/16" wide. I didn't notice that until I was
nearly done, and figured that since they weren't actually going to be
used it didn't matter.

one of the holes is space-saving (for 3d-printing), the other is
essential (and is 3.5mm diameter) for the bolts to hold everything
together.

Post by Tor, the Marqueteur
I also didn't add the slot for the PCB, mostly because I wasn't sure of
the size, and I didn't have the appropriate cutter lying close by. I
have a couple thoughts on that.

hmm me too: a CNC lathe would do the trick. the slot is essential in
one of the parts for access to the PCMCIA eject-button.

http://hands.com/~lkcl/eoma/kde_tablet/3dcase/microdesktop_model2_corner.stl

l.

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[zap]

I just hope you use extremely strong wood Luke.

;)

Post by Luke Kenneth Casson Leighton
---
crowd-funded eco-conscious hardware: https://www.crowdsupply.com/eoma68
On Sun, Apr 30, 2017 at 7:44 AM, Tor, the Marqueteur

Post by Tor, the Marqueteur
Thought I'd give a try at how a solid wood version would come out. Here
is the result of about 45 minutes prototyping with a piece of 3/8" Cherry
I had lying around.

those look _great_.

Post by Tor, the Marqueteur
A couple notes: The 5/64" (.078", 1.98mm) bit has some tendency to
wander, as can be seen in the holes. I also goofed the measurement so
these are 11/16" instead of 9/16" wide. I didn't notice that until I was
nearly done, and figured that since they weren't actually going to be
used it didn't matter.

one of the holes is space-saving (for 3d-printing), the other is
essential (and is 3.5mm diameter) for the bolts to hold everything
together.

Post by Tor, the Marqueteur
I also didn't add the slot for the PCB, mostly because I wasn't sure of
the size, and I didn't have the appropriate cutter lying close by. I
have a couple thoughts on that.

hmm me too: a CNC lathe would do the trick. the slot is essential in
one of the parts for access to the PCMCIA eject-button.
http://hands.com/~lkcl/eoma/kde_tablet/3dcase/microdesktop_model2_corner.stl
l.
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[Luke Kenneth Casson Leighton]

---
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Post by zap
I just hope you use extremely strong wood Luke.
;)

whole device is under 100g, but yes hard-grain wood will be needed as
those are quite small grooves.

l.

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[Tor, the Marqueteur]

Post by Luke Kenneth Casson Leighton

Post by zap
I just hope you use extremely strong wood Luke.
;)

whole device is under 100g, but yes hard-grain wood will be needed as
those are quite small grooves.

Given the overall sizes and weights, most woods will work. I wouldn't
choose Oak by preference, but on the whole, the list of reasonably common
woods that can't be used is probably smaller than the list that can.
Maple or Birch would both be very good choices and match the plywood of
the rest of the case.

Given Maple prices around here (on the more expensive side of Maple), the
wood cost for 2000 of these should still come in under $50 US.

Tor

[Tor, the Marqueteur]

Post by Luke Kenneth Casson Leighton
---
crowd-funded eco-conscious hardware: https://www.crowdsupply.com/eoma68
On Sun, Apr 30, 2017 at 7:44 AM, Tor, the Marqueteur

Post by Tor, the Marqueteur
Thought I'd give a try at how a solid wood version would come out. Here
is the result of about 45 minutes prototyping with a piece of 3/8" Cherry
I had lying around.

those look _great_.

Thanks.

Post by Luke Kenneth Casson Leighton

Post by Tor, the Marqueteur
A couple notes: The 5/64" (.078", 1.98mm) bit has some tendency to
wander, as can be seen in the holes. ...snip...

one of the holes is space-saving (for 3d-printing), the other is
essential (and is 3.5mm diameter) for the bolts to hold everything
together.

That makes things easier, and the 9/64" bit is more stable. Looks like I
probably grabbed the numbers on that from an old version.

Post by Luke Kenneth Casson Leighton

Post by Tor, the Marqueteur
I also didn't add the slot for the PCB, mostly because I wasn't sure of
the size, and I didn't have the appropriate cutter lying close by. I
have a couple thoughts on that.

hmm me too: a CNC lathe would do the trick. the slot is essential in
one of the parts for access to the PCMCIA eject-button.
http://hands.com/~lkcl/eoma/kde_tablet/3dcase/microdesktop_model2_corner.stl

Yeah. At the complexity of the inside you have there, I don't see
anything short of CNC that that could reasonably do the job. Those sharp
inside corners are hard, but it looks like a single cutter pass can
probably run past far enough to work if that direction were taken.

Tor

[Bluey]

Post by Tor, the Marqueteur

Post by Luke Kenneth Casson Leighton

Post by Tor, the Marqueteur
I also didn't add the slot for the PCB, mostly because I wasn't sure of
the size, and I didn't have the appropriate cutter lying close by. I
have a couple thoughts on that.

hmm me too: a CNC lathe would do the trick. the slot is essential in
one of the parts for access to the PCMCIA eject-button.
http://hands.com/~lkcl/eoma/kde_tablet/3dcase/microdesktop_model2_corner.stl

Yeah. At the complexity of the inside you have there, I don't see
anything short of CNC that that could reasonably do the job. Those sharp
inside corners are hard, but it looks like a single cutter pass can
probably run past far enough to work if that direction were taken.

Not sure if you are looking for one but this reasonably-priced CNC kit machine seems to get good reviews on Amazon: https://www.bobscnc.com/collections/cnc-routers-engravers/products/e3-cnc-engraving-kit <https://www.bobscnc.com/collections/cnc-routers-engravers/products/e3-cnc-engraving-kit>

- Bluey

[Luke Kenneth Casson Leighton]

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

Post by Bluey
Not sure if you are looking for one but this reasonably-priced CNC kit
https://www.bobscnc.com/collections/cnc-routers-engravers/products/e3-cnc-engraving-kit

that's more than twice the cost of ones here in china :)

my friend found one that's not half bad - absolutely no endstops and
using threaded bar not even lead screws of course - but it works
surprisingly well and would do the job.

my only concern is: it's gonna take forever to machine 2000 parts,
which would need to be turned twice through 90 degrees *in different
axes*. that's a 5-axis CNC which starts to get a bit hairy.

l.

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[Bluey]

Post by Luke Kenneth Casson Leighton
---
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Post by Bluey
Not sure if you are looking for one but this reasonably-priced CNC kit
https://www.bobscnc.com/collections/cnc-routers-engravers/products/e3-cnc-engraving-kit

that's more than twice the cost of ones here in china :)
my friend found one that's not half bad - absolutely no endstops and
using threaded bar not even lead screws of course - but it works
surprisingly well and would do the job.
my only concern is: it's gonna take forever to machine 2000 parts,
which would need to be turned twice through 90 degrees *in different
axes*. that's a 5-axis CNC which starts to get a bit hairy.
l.

Oh, yeah, I saw plenty of ones that were cheaper but the reviews suggested that it would be prudent to give them a wide berth!

I was more thinking of the CNC for cutting any flat-ish timber components; although a 5-axis machine with sufficient precision (e.g., via a specialist milling service) could potentially be used to make moulds for plastic injection manufacture. How many component variations are there to make?





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[Bluey]

Post by Bluey

Post by Luke Kenneth Casson Leighton
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Post by Bluey
Not sure if you are looking for one but this reasonably-priced CNC kit
https://www.bobscnc.com/collections/cnc-routers-engravers/products/e3-cnc-engraving-kit

that's more than twice the cost of ones here in china :)
my friend found one that's not half bad - absolutely no endstops and
using threaded bar not even lead screws of course - but it works
surprisingly well and would do the job.
my only concern is: it's gonna take forever to machine 2000 parts,
which would need to be turned twice through 90 degrees *in different
axes*. that's a 5-axis CNC which starts to get a bit hairy.
l.

Oh, yeah, I saw plenty of ones that were cheaper but the reviews suggested that it would be prudent to give them a wide berth!
I was more thinking of the CNC for cutting any flat-ish timber components; although a 5-axis machine with sufficient precision (e.g., via a specialist milling service) could potentially be used to make moulds for plastic injection manufacture. How many component variations are there to make?

Just came across this on hackaday: https://hackaday.com/2016/02/09/learn-resin-casting-techniques-duplicating-plastic-parts/ <https://hackaday.com/2016/02/09/learn-resin-casting-techniques-duplicating-plastic-parts/>

Perhaps it could be a quick, effective, and affordable option once you’ve got a few sets of high-quality components printed?

Cheers, B.

[Tor, the Marqueteur]

Post by Luke Kenneth Casson Leighton
my only concern is: it's gonna take forever to machine 2000 parts,
which would need to be turned twice through 90 degrees *in different
axes*. that's a 5-axis CNC which starts to get a bit hairy.

The other direction to avoid 5-axis would be to make strips about 3' long
of appropriate size. Mill the dados with a suitable blade in a mini
table saw. A router in table can handle the corners for radius
consistency, or P150 in a palm sander (as I used) can do pretty nicely.
Then do a sanding of that in 3' lengths.

At this point, except for one lip by the dado that's nearly a rabbet the
entire thing becomes a 3-axis flat milling operation. Even that one I
suspect could be done by letting the cutter making the rabbet run just
past the PCB slot and tolerating the radius.

From there, the possibilities diverge. One option is to cut to corner
length pieces and find a way to secure them in a CNC. This has the
advantage of a consistent point to index from, but requires filling a jig
with lots of little pieces.

The other option is to load lengths into the CNC, but then either you
need the CNC to cut it for accuracy or you have to reference a CNC edge
for later cutting, because a small error in length will accumulate fast
and throw the whole thing out of tolerance.

Last would be drilling the holes. I just made a mark, lined several up
in the vise on my milling machine, and ran across them. Not hard, but it
would get a little tedious for 2000.

Looking another way, if the extrusion mold mentioned isn't so difficult,
then you just need about 170' of custom extrusion to load into the CNC or
cut into pieces and load.

Tor

Post by Luke Kenneth Casson Leighton
l.

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[Luke Kenneth Casson Leighton]

i was just thinking, if you had the appropriate cutters (like a router
/ plane with different width bits) it would be possible to just run
the parts through some sort of jig.

l.

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[Tor, the Marqueteur]

Post by Luke Kenneth Casson Leighton
i was just thinking, if you had the appropriate cutters (like a router
/ plane with different width bits) it would be possible to just run
the parts through some sort of jig.

This is definitely possible. With the corner design on my screen
(apparently the blue ones in the photos), all the different levels and
widths of cutout make it something I'd not want to think about doing that
way.

Still, it looks like it could be simplified a bit. You seem to have the
PCB slot both top and bottom, which is nice for interchangeability, but
could be dispensed with. I'm thinking about other possibilities, but I
can't yet visualise fully what the tolerances are relative to the
populated PCB.

I know revisions of the PCB are generally hard (at least if they involve
rerouting traces), but I have to ask what the implications of adding a
sixteenth to each side edge of the PCB for mounting would be. The length
front to back would remain the same. If that could be done and would
allow the full rectangle of the corner piece to be used, then there are
only two operations that would need to be done on the individual corner
piece, namely the stopped dado for the PCB (only one per corner, two
different corners) and the hole for assembly bolt.

Tor

Post by Luke Kenneth Casson Leighton
l.

--
Tor Chantara
http://www.fineartmarquetry.com/
808-828-1107
GPG Key: 2BE1 426E 34EA D253 D583 9DE4 B866 0375 134B 48FB
*Be wary of unsigned emails*
Stop spying: http://www.resetthenet.org/

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[Tor, the Marqueteur]

I never got a reply to this message, and seeing you ready to send the
microdesktop PCB to production, I thought I ought to make sure you saw
it, Luke.

Post by Tor, the Marqueteur

Post by Luke Kenneth Casson Leighton
i was just thinking, if you had the appropriate cutters (like a router
/ plane with different width bits) it would be possible to just run
the parts through some sort of jig.

This is definitely possible. With the corner design on my screen
(apparently the blue ones in the photos), all the different levels and
widths of cutout make it something I'd not want to think about doing that
way.
Still, it looks like it could be simplified a bit. You seem to have the
PCB slot both top and bottom, which is nice for interchangeability, but
could be dispensed with. I'm thinking about other possibilities, but I
can't yet visualise fully what the tolerances are relative to the
populated PCB.
I know revisions of the PCB are generally hard (at least if they involve
rerouting traces), but I have to ask what the implications of adding a
sixteenth to each side edge of the PCB for mounting would be. The length
front to back would remain the same. If that could be done and would
allow the full rectangle of the corner piece to be used, then there are
only two operations that would need to be done on the individual corner
piece, namely the stopped dado for the PCB (only one per corner, two
different corners) and the hole for assembly bolt.
Tor

Post by Luke Kenneth Casson Leighton
l.

--
Tor Chantara
http://www.fineartmarquetry.com/
808-828-1107
GPG Key: 2BE1 426E 34EA D253 D583 9DE4 B866 0375 134B 48FB
*Be wary of unsigned emails*
Stop spying: http://www.resetthenet.org/

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Sen

[Hrvoje Lasic]

On 30 April 2017 at 08:44, Tor, the Marqueteur <

Post by Tor, the Marqueteur
Thought I'd give a try at how a solid wood version would come out. Here
is the result of about 45 minutes prototyping with a piece of 3/8" Cherry
I had lying around.
A couple notes: The 5/64" (.078", 1.98mm) bit has some tendency to
wander, as can be seen in the holes. I also goofed the measurement so
these are 11/16" instead of 9/16" wide. I didn't notice that until I was
nearly done, and figured that since they weren't actually going to be
used it didn't matter.
I also didn't add the slot for the PCB, mostly because I wasn't sure of
the size, and I didn't have the appropriate cutter lying close by. I
have a couple thoughts on that.

ok, so I see this part is extruded profile in fact. One alternative is to
make it from aluminum. cost of tooling should not be more then couple of
hundred USD and you can order some qty for `trial`, prototyping etc.
producer will cut you this part as per your size. Basically you pay around
4 usd/kg and some more on cutting, all together not much. just idea.

[Luke Kenneth Casson Leighton]

On Thu, May 11, 2017 at 10:50 AM, Tor, the Marqueteur

Post by Tor, the Marqueteur
I never got a reply to this message, and seeing you ready to send the
microdesktop PCB to production, I thought I ought to make sure you saw
it, Luke.

i did see it - i either replied or decided i didn't have time to take
up the ideas: no on doing PCB redesigns, that's for sure: it's
something like $600 a shot for the layer 2 PCBs plus assembly and
takes about 3 weeks. time to move on. it's only 450 units. if it
was 5,000 i'd do things differently.

l.

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