Hey, I’m working on a second run of my custom backplates to fix a few issues I discovered on the first one. One of the things I noticed when I got my Pocket and compared is that the mounting holes for the screws are countersunk. But when I get these manufactured, they’re just holes straight through.
Was there a second manufacturing step where you partially drilled out the mounting holes? We do have a drill press at my local hackerspace so I should be able to do that, just wanted to check if I’m missing something.
I exported the PCB files from the GitLab archive into .step files so I could mess with them in FreeCAD to chamfer the screw holes. PCBway just shipped the results to me, so I’ll let you know if it works out!
Yes, afaik there isn’t really a way to spec this in KiCAD so we asked the PCB manufacturer to do countersinking (actually counterbores) on those holes for us (they are from PCBBuy).
They turned out great. I had the back plates made to 1.6mm per the .STEP file instead of using their 1.5mm stock aluminum sheet, so they stick out a fraction of a millimeter when installed. I made the chamfers a too wide too, so the screws are also recessed a little. I also followed the recommendations to not have the headphone and port plates bead blasted due to the metal being too thin, but the mill marks and other imperfections are a lot more noticeable without the bead blasting.
The company accepted the 1.6mm CAD file to use the 1.5mm stock aluminum sheet and I adjusted the chamfer, so I have new plates on the way. I’ll see if that makes a difference. I also had them make new port plates that are bead blasted along with a keyboard and screen bezel.
If this works, I might even consider having the whole case re-done with a natural aluminum finish.
Got the updated parts today. I am very satisfied with the results. The only downside is that this thing seems noticeably heavier, but I can live with that!
There was a problem with the screen bezel, but that was a result of my own inexperience with CAD and failure to catch a difference between an older file and the latest one.
I just submitted an order at PCBWay asking for a counterbore on the mounting holes and got back a request for more information:
Diameter of the large hole
Diameter of the small hole
Depth
Direction
The small hole is of course the 2.2mm hole that was drilled properly on the first run. Is the larger circle in the User.Comments layer meant to be the larger hole to accommodate the screw head? And what depth did you have them drill to? Apologies if I’m missing some info that’s in the KiCad file somewhere.
I had to export the KiCad files into .step format and then figure out how to chamfer the edges in FreeCad. The PCBWay people were satisfied with those measurements.
The default chamfer length was 1mm, which I found too deep on my prototype, so I changed it to 0.9mm and the screws are much more flush. I also recommend selecting the stock 1.5mm aluminum sheet rather than having them mill it to 1.6mm.
Would either of you be willing to share your plate designs? I realise that there’s already a post about modifying the MNT design on their blog, but I’m still learning so additional examples are always useful.
I opened up the top back pcb in FreeCAD with the KicadStepUp Workbench, exported it to a .step file, chamfered the holes with a 0.9mm depth, and ordered one from JLCPCB’s CNC service. Total cost of 6160 aluminum with bead blasting was just under $12USD. Shipping cost more than the actual manufacture of the part! If it turns out well, I’m happy to share the designs publicly, I’ll post them on gitlab once I get my account created. I only did the top panel, but I might do the rest of the case pcbs in aluminum for the heck of it. I looked at copper, but the part ended up being about $30 and I wanted to make sure of fit before I ordered that. I may just end up getting it manufactured in copper so that it has better thermal mass for cooling capacity as I purchased the RK3588. I’ll check in a few months from now when I get both my part and my kit, and let you all know how it does.
Oh wow, I didn’t realize it would be that cheap! Very interested in seeing how this goes, I wonder if it’d add much cost to get a design engraved into the plate…
That’s my next project, I’m currently sketching a simple design into the lid with the intention of getting that version manufactured in copper if my first prototype fits properly and has no other issues. If I do find problems with it, I’ll send for another 6061 aluminum revision. I’d be curious to see how the bead blasting affects the design though, smaller or more delicate designs I could possibly see the introduction of defects, but admittedly I don’t know much about that particular process. I might get it hand-polished if it doesnt add too much cost
Anodized no, just bead blasted. The trick was I used their cnc service rather than their pcb printing service. I’m hopeful it falls within tolerances and fits well. Their pcb service was much more expensive, on the order of $15-20 ea with a 5x minimum buy.
So I cancelled my previous order (it hadn’t yet been approved) and uploaded a new part with a design engraved on the cover. Bead blasted, anodized aluminum (glossy black) with the engraving was just about $19 for the part, and $8 for shipping, bringing the total to just under $27. I finished the engraved piece before they approved my first revision, so I decided to skip right to the second revision and order that instead. Looking forward to that arriving!
