Standoff and acrylic test

Standard PCB templates and project cases

Standoff and acrylic test

Postby ian » Tue Feb 07, 2012 7:22 am

Mouser order just came with the standoffs, so I tested out a case. This isn't a full test because we changed a bunch of stuff after I got the test panels cut, but we can see one corner.

This is (top to bottom):
6mm screw
3mm Acrylic
8mm standoff
1.6mm PCB
5mm standoff
12mm screw

It is ok. I think if all four were present it would work adequately. 1.5mm acrylic is definitely something I want to check out for cases this size (5031,6037).

At this point we need a new acrylic test with the correct hole placement. I also liked dsm's idea for multiple side panel cuts instead of one long one. We will also need to consider the spacing between the edge of the PCB and the placement of the side wall, in the current design it will be really tight.

Picture attached, and a pic of the standoff collection :) I need to get a multi-box thing for it.
Attachments
sob-test.jpg
test-standoffs.jpg
User avatar
ian
Crew
Crew
 
Posts: 10803
Joined: Mon Jul 06, 2009 6:14 am

Re: Standoff and acrylic test

Postby tayken » Wed Feb 08, 2012 11:14 pm

I will be cutting some acrylic today, so wait for some pictures later. :) Currently I have a few problems related to the script and one of them is having multiple slots instead of one long one. I guess once I manage to solve that the script will be complete.
User avatar
tayken
Developer
Developer
 
Posts: 1522
Joined: Sat Dec 12, 2009 10:58 am
Location: Tokyo, Japan

Re: Standoff and acrylic test

Postby ian » Thu Feb 09, 2012 8:14 am

Thanks for the update Tayken. I hope we can get together and talk about them next week :)
User avatar
ian
Crew
Crew
 
Posts: 10803
Joined: Mon Jul 06, 2009 6:14 am

Re: Standoff and acrylic test

Postby tayken » Thu Feb 09, 2012 2:36 pm

OK, did some cuts, I will send the pics tomorrow, they are not turning as good as I thought without daylight.

I tested the design with side panels. Doing some adjustment for the laser width works real good. I first tested it with some slotted connections, like as in the Twitter Printer stand, looked perfect! Then moved to the box. After cutting side panels were really hard to mount, I broke two slots on one top piece, one slot in the other. So the distance between the slot and the edge of the acrylic should have been bigger, the fit is real good and it holds the box together without some screws. :)

Second problem is assembly, which is the part we skipped. Not the using screws and nuts and bolts or magnets type of decision but actually putting the parts together. The side panels were really though to fit in place by themselves but in the end people have to put all 4 in at the same time because of the interlocks which is really problematic as today's test showed me. And I just had one slot per part, there will be more! So for the next trial I will make the tabs chamfered in order to make them go in easier. Might have to change the interconnect between side panels too so that people can put them one by one.
User avatar
tayken
Developer
Developer
 
Posts: 1522
Joined: Sat Dec 12, 2009 10:58 am
Location: Tokyo, Japan

Re: Standoff and acrylic test

Postby dsm » Thu Feb 09, 2012 3:50 pm

tab and slot size

tayken,

What thickness acrylic are you using? I've been designing with 1.5 mm acrylic (which looks better to me for smaller enclosures).
What slot-to-edge thickness are you using? I've been using 3.0 mm (or twice the 1.5 mm acrylic thickness).
What width slots are you using? Probably nominal acrylic thickness plus 0.05 mm to 0.10 mm?
What length slots are you using? Probably nominal 10 mm slot length plus 0.05 mm to 0.15 mm?

Some laser-cutter drivers adjust for the laser kerf automatically.
For example, if a hole or slot is being cut, the laser-cutter driver may assume that the laser path should be shifted inward so the hole or slot dimensions are correct.
Some laser-cutter drivers require that you adjust for the laser kerf manually in your design.
Some experimentation is often needed to get the results you desire.

The assembly problems you are experiencing sound like the parts are too tight.
Loose, but not too loose, is probably easier to assemble.
Remember that the hardware will hold the case together.

I made my sides of my prototype long enough to overlap the ends (simple butt joint).
I then inserted the case sides and case ends into the bottom window.
I then squeezed the case sides slightly to keep the case ends in position while adding the top window.
This was eventually accomplished.
Which is not too bad if you're just assembling the enclosure once.
But if one is opening and closing the enclosure a lot, you have a definite point.
This is not a particularly user friendly case closure scheme.

See (link) for an example.

Thanks for your time.

dsm
dsm
Full Member
Full Member
 
Posts: 216
Joined: Sun Jul 10, 2011 3:04 pm

Re: Standoff and acrylic test

Postby tayken » Fri Feb 10, 2012 10:22 am

dsm wrote:tab and slot size
What thickness acrylic are you using? I've been designing with 1.5 mm acrylic (which looks better to me for smaller enclosures).

I couldn't find any 1.5mm acrylic so this was done with 3 mm with an old design I had which I changed quickly for laser width.
dsm wrote:What slot-to-edge thickness are you using? I've been using 3.0 mm (or twice the 1.5 mm acrylic thickness).
What width slots are you using? Probably nominal acrylic thickness plus 0.05 mm to 0.10 mm?
What length slots are you using? Probably nominal 10 mm slot length plus 0.05 mm to 0.15 mm?

Slot-to-edge was 2 mm which is the problem, too thin. Will change that in the future. Ran out of time as I had some other designs to cut too. Width is 3 mm (spot on) but acrylic is about 3.1-3.2 mm thick when I actually measured it. Slot length is as the old version, 24 mm, same as the tab as I tried to see the tolerances with this test.
dsm wrote:Some laser-cutter drivers adjust for the laser kerf automatically.
For example, if a hole or slot is being cut, the laser-cutter driver may assume that the laser path should be shifted inward so the hole or slot dimensions are correct.
Some laser-cutter drivers require that you adjust for the laser kerf manually in your design.
Some experimentation is often needed to get the results you desire.

Did those tests, found out that the laser cutter does not do any adjustments by itself and laser width is 0.2 mm which was used for adjustments (mentioned in another old topic).
dsm wrote:The assembly problems you are experiencing sound like the parts are too tight.
Loose, but not too loose, is probably easier to assemble.
Remember that the hardware will hold the case together.

Yes, I agree with this, the parts are too tight. But if they are loose, then that does not look really professional. Maybe making slot widths = acrylic thickness + 0.15mm will solve this problem. Also making slot-to-edge parameter = 2x acrylic thickness.
dsm wrote:I made my sides of my prototype long enough to overlap the ends (simple butt joint).
I then inserted the case sides and case ends into the bottom window.
I then squeezed the case sides slightly to keep the case ends in position while adding the top window.
This was eventually accomplished.
Which is not too bad if you're just assembling the enclosure once.
But if one is opening and closing the enclosure a lot, you have a definite point.
This is not a particularly user friendly case closure scheme.

Maybe I can get bunch of cases made next time I'm using the laser cutter and I can send those to different people here to test. I can create some other side panels too. Now back to the drawing board for me. But here are the pictures for the case I did (which is held together by friction only) and some new cases for my OLS and BPv2. In both of the the USB connector opening was too small, so that was fixed, also in BP one I changed the IO connector opening to a tabbed one so that you cannot insert the cable other way around.
Attachments
2012021023560001.JPG
OLS case with USB hole fixed
2012021023560003.JPG
BPv2go case with new connector opening
2012021023570000.JPG
Case, top shot
2012021023570001.JPG
Case, side shot
User avatar
tayken
Developer
Developer
 
Posts: 1522
Joined: Sat Dec 12, 2009 10:58 am
Location: Tokyo, Japan


Return to Sick of Beige