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Clam Shells

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Posted (edited)

The Nylon is every bit as bitchy as I remember it being, as concerns its habit to warp and distort while printing.  Be that as it may, the ways it decided to warp were not show stoppers for the test.  The wiggle problem was properly resolved by making the bottom of the shell flat, and  YES-- Cards with the "hang-out" in the back do in fact fit inside the clamshell, and then fit inside the PEB without wiggle. (Tested with TI RS232 card.)

 

Here are the files for the community.

 

PebShell_B.stlPebShell_A.stlPEB card clamshell side B.stpPEB card clamshell side A.stp

 

You will need screws.  I modeled these with just blind holes, but the holes are both deep enough and large enough to be "screw thread tapped" with a self-threading screw.  I sourced some suitable ones from the local Walmart.  They are #6 1/2 inch sheet metal screws.  They are self tapping, with a coarse thread.  The package looks like this:

 

c9630f0c-ddfd-41de-af64-742d31b01768.17f

To use them PROPERLY, you have to do a bit of a gentle procedure before assembling the shell:

 

Turn side A over to expose the screw posts. Start the screw with a manual screwdriver, and turn *VERY VERY SLOWLY*.  If it feels very tight, back the screw out a bit, then re-tighten, then continue.  Do this until about half the thread has been pulled into the screw post.  Do this for all 4 screw posts.  Remove the screws.

 

Turn side B over to expose the screw lands.  If you turned on supports, (which you NEED to do, to support the long PEB retention tabs!) you probably have support material in the counterbored holes, and will need to remove it.  We can kill 2 birds with one stone here--  Insert the screw as you did with side A, and turn very slowly.  As the screw penetrates and goes out the other side, it will put pressure on the support material, and lift it out of the recess.  Use a small metal tool to lift it the rest of the way, and pull it out.  Tap it through the rest of the way until thread is fully through, then back out the screws again.

 

Assemble the shell, with your card, lining up the LED, the back-porch (if applicable) and the 4 screw holes.  Like the original PEB shell, it has overhanging lips that mate between sides A and B.  (Some fiddling may be required.)  Insert screws one at a time into the shell via the counterbored hole sockets on the back of side B.  Screw the screws down until the heads are flush with the back of side B. (A small amount of head might still be raised, after fully tightening; This is fine, there is enough room between PEB cards that they wont interfere.)

 

These screws have been tested with both nylon and PLA prints.  PLA is more fragile. Be very gentle when tapping the posts.

 

Edited by wierd_w
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Lookin' really nice!

Does the replacement of the metal clamshell require the addition of a traditional heat sink or some other means to wick away the heat from each regulator?  This would be my only concern for some of the hotter-running cards.

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Posted (edited)

For vintage cards (like a Geneve), I would say that you could run a strip of heat pipe in there.  There is quite a lot of 'room' inside the shell.  You could shave off (break off?) a bit of the top of each of the bottom two screw posts, so that the shell still closes with the heat dissipation solution being pressed down onto the regulators.

 

Two of these would probably work?

https://guide.alibaba.com/shop/aluminum-heatsink-45mm-x-45mm-x-14mm-for-voltage-regulator-scr-mosfet_1003661028.html

Shave the bottom two screw posts down 1mm or so, and then utilize mechanical clamping (with some good thermal paste) to keep the heatsink pressed under the regulator, utilizing the through-hole design.

 

 

I really intended these replacement shells for more modern cards with more modern electronics in them though. (TIPI, modern SAMS, et al.)

Edited by wierd_w

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15 minutes ago, wierd_w said:

 

I really intended these replacement shells for more modern cards with more modern electronics in them. (TIPI, modern SAMS, et al.)

Oh, got it.  When I looked at the printed case it seemed to be built more for the older cards that required a case, like the 32K, etc.   I have a few cards like the TIPI PEB and HRD4000B where the front edge connector extends into the slot, so I wasn't certain how that would come into play.   Here's a picture for reference with cards from left to right: TI RS232, Geneve, Horizon 4000B, Myarc HFDC, SCSI card, TIPI-PEB, Myarc FDC, Horizon 3000. 

 

image.thumb.png.12aa5659042a054314e59c1f33f1115c.png

 

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I see.. I was unaware that the board makers had done this.

 

A minor modification would make it possible to enclose them, but would eliminate the rear retention tab completely. (It would extend the size of the "back porch" slot so that it covers the whole card area, allowing the entirety of the board to stick out.)

 

These kinds of things are why I include the .stp files. (so that you can easily modify the geometry in the CAD software of your choice)

 

 

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On 4/4/2021 at 1:13 AM, wierd_w said:

Your creality 5 might be able to do it, but it would be a tight fit.

 

Long direction end-to-end measurement of the model is 206mm.  (my printer has a 200mm max area).  Your Creality 5 has a 220mm x 220mm bed, so it should be able to do it.

Barely.

 

The huge Chiron I ordered is a bit overkill, but damnit, I am TIRED of dealing with the issue of "printer too small" :)

235x235 it says on both my 3 and 5

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5 hours ago, wierd_w said:

I see.. I was unaware that the board makers had done this.

 

A minor modification would make it possible to enclose them, but would eliminate the rear retention tab completely. (It would extend the size of the "back porch" slot so that it covers the whole card area, allowing the entirety of the board to stick out.)

 

These kinds of things are why I include the .stp files. (so that you can easily modify the geometry in the CAD software of your choice)

 

 

Pretty much every modern board has tabs at front and back to allow them to use the stabilization fingers in the card cages. Another major difference is the holes in the board--unless they support a heatsink, they are just not there, and even when they do, they are generally out of alignment with the case screw holes. Note that the metal cases also have some bumps and posts that go through the board in the vicinity of the 60-pin connector. The corresponding holes in the circuit cards are missing, and often, the studs/posts will impact components.

 

I have a few boards that I designed with all of the correct holes/spacing, but as I couldn't get enough board cases to make it practical, I didn't take that option too far. Having new cases available does increase the attractivity of doing boards for clamshells again though.

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Since I have the dehydrator (kinda) working, I can do long prints with nylon now, without the filament absorbing water like a depends undergarment.

 

As such, I have made some modifications to the previous design, specifically to stiffen the shell up a bit for use with the smurf-blue weed trimmer nylon. Once I test the changes, and am happy with them, I will upload them.

 

There is nothing wrong with the prior models; this is explicitly changes made specifically to add the extra stiffness needed for the nylon.

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