I tried putting fans inside the case, which made it clear that if I add fans I should probably mount them underneath instead, which seems easier than trying to figure out what is best to change:
I really think passive cooling ought to be enough; having any fans at all is a workaround if it gets too hot.
After I started printing the case last night, I remembered that I had intended to fip the switch 180⁰ to put the receptacle at the bottom and the switch above it. Oh well.
This morning, I found that I have the… opportunity… to print it again with the switch flipped:
First failed bed adhesion I’ve had in a while. There are also some artifacts around the slots. So I’ll keep the black reset button that printed fine, flip the switch, and print in a different color later, slower, and probably one piece at a time so a print failure on one part doesn’t wreck other parts as it did here.
Also, the reset button was a snug fit in its hole because there was no clearance in the hole for it in the case, and it would have stuck down if pressed. I have now flipped the switch and added clearance around the reset button, and I plan to check all the hole sizes that showed up in the partially-complete print against hardware before I print again.
Flipping the switch took me a few tries to learn the best way in SolidWorks: I suppressed the one constraint that kept it from rotating it, dragged it around to rotate it, and unsuppressed that constraint, which now snapped it to the orientation I wanted.
This was a successful failure. I stopped the print early so it used less filament, yet I was able to get lots of measurements for what needs to change to make it successful. I think I had an example of everything I might need to change; we’ll see.
Not only did the tray detach while printing, but also the corners of the main box warped up slightly. I’m still getting used to PETG. @Eclsnowman can this be a result of the bed being too hot? I used the same settings that I’ve been using successfully for printing visors — 280⁰/75 first layer, 285⁰/70 subsequent layers — but those are only 5mm tall! 
I’d appreciate the benefit of your experience here. I’m (still) printing on glass because my PEI bed has reportedly left China a week ago but hasn’t yet made an appearance in the US, which probably means stuck in customs.
My personal opinion is never changed the temperature of your heated bed during a print. All you’re going to do is inherently cause a contraction which is exactly what you don’t want to happen during a print.
It should be able to be held down with the right first layer settings and bed preparation, But if it’s lifting from the corners you could always add round “lillypads” at the corners for adhesion instead of a brim which are easy to remove. Another trick I use at certain times is to take a big flat base and put some relief cuts in the model, then when it tries to contract it isn’t such a monolithic structure and it’ll contract internally more than across its entire length.
Also if your bed is glass chances are the temperature isn’t reading accurately at the glass compared to where your thermistor is actually taking the temperature. So you might have to go slightly up in temperature for good adhesion. You just have to be a little careful with PETG because on glass it can grab so well that when it contracts it can actually rip out chunks of glass.
Thanks for the advice, it makes sense!
I made more changes to the model before I print again. This includes making it a few mm taller so the fans fit, extra M5 mounting holes so I don’t have to tap the center holes on the front extrusion, a single access for the mini usb and microsd card on the controller board with a heavy chamfer to give better finger access to the microsd card (this time linked to the board for dimensions), a .5mm offset in the switch mount hole (it doesn’t fit otherwise) which I also inverted to put the switch at the top, and more I’ve forgotten. I pushed all the latest files to the git repository.
I wanted to make the cable routing openings be rounded instead of having 45⁰ straight sections, but every attempt I made for an hour make the entire case disappear, so I gave that up. It’s not important, that was just an attempt at a learning exercise. Edit: the case disappeared even if I rolled back to that point without modifying the model at all, so I charged ahead and made the rounded filleted openings I imagined.
Yes, I’m using a glass bed, coated with a good layer of hairspray. I’ll raise the temperature to 80⁰C, let it stabilize for a while before printing, and leave it be while printing. I have definitely taken chunks out of glass with PETG, so I know about that tendency. Actually building the enclosure I’ve been intending to make would be a good next step!
The PETG might benefit from more consistent temperatures from the enclosure I haven’t yet built for my other printer.
@Eclsnowman oh, another question about your design… In what you modeled, the back side (against the extrusion) is thinner than the outside shell opposite it. Is that on purpose because the outside shell needs to be stronger, or just an accident? (I can tweak it, I’m just curious whether you have experience that woud say that I shouldn’t tweak it.)
Yes, I made it thicker on the cover since that gets bolted on and might be more prone to being warped. Plus I wanted that chamfer on the outside which required the part be a little thicker.
It could be made thinner and remove the chamfer, but I might add an inner perimeter reinforcement rib that sits inside the case to give it more vertical stiffness. Pretty easy to do with projection offsets in the sketch from the existing holes and outer profile.
It should be fine; if I have trouble accessing the microsd card and want to make it thinner in another print, there are lots of ways. Thanks!
I didn’t feel like learning to model a differential screw (M5/M4) in solidworks, so you’ll have to imagine it going through the arm sticking out from the 2060, then through the flag that trips the interrupter. It looks like it could tear the endstop off, but actually I’ll set it up so that a hard stop prevents that. Each part is separately printable without supports.
I just have to decide whether to buy M4 and M5 dies or to single-point a dual-pitch screw on the lathe for extra street shop cred. 
If I single point it, I’ll actually make both holes the same diameter (an appropriate minor diameter cutting 0.8 and 0.9 mm threads in whatever piece of brass rod I find in my shop probably), and then just cut different non-standard thread pitches, one in each end of the rod.
(Actually, cutting M5x0.8 and M5x0.9 would be possible with the standard cheap harbor freight set. I’d just need to put the follower on the lathe to cut a 5mm rod accurately first. Can’t tell whether they have it in stock at my local harbor freight though from their web site.)
I tried single-pointing 0.6mm and 0.7mm threads on separate sections of a ¼" (6.35mm) brass rod, but my threading insert chattered a bit since its angles weren’t meant for brass, and I didn’t cut a separate threading tool for brass. I also realized that it will probably actually be easier to have the threaded sections be different diameters; it will be easier to assemble. But my lathe follower fingers are too big for very small diameters. So I think Mark Rehorst’s technique of using an M5 screw and turning down part of it and threading M4 is probably the best technique, event when threading only through printed plastic where I can choose any combination of diameter and pitch that I want. So now I find out whether harbor freight has those dies in stock… They don’t; ordered a slightly more expensive similar set from Amazon in order to get it Monday.
(The reason I tried small thread pitches was there was no larger-pitch 0.1mm difference available without swapping out the change gears, which is a long and greasy process compared to moving knobs on the front of the gearbox… I do it when I have to, but I prefer not to if I can help it.)
I printed the parts for the Z optical endstop. I half-threaded the holes; threading most of the way through, but stopping before I had fully tapped. This makes it so it’s easy to thread the screws in straight, but then there’s a section of rolled thread that holds tight, basically working like a lock nut. I threaded the M4 in the flag fully through. Spiral flute taps are wonderful for tapping plastic!
I discovered that the part of the arm against the v-slot, and the part holding the optical end stop, were too thin and warped when tightened. Other than the warping, everything fit together correctly.
In order to move to the next common screw length I added 4mm to the thickness of each feature that was too thin.
I also had to work extra hard to convince solidworks to overlap a few screws to show what the differential screw will look like.
Can’t wait for my small metric die set to arrive so that I can make the hybrid screw and attach this for real!
My flag is too small!
Also, it was a pain to get the flag mount arm aligned properly perpendicularly, so I added alignment features to attach it to the v-slot. I’ll see whether these work better. …Oh, yes, much better, much easier to align!
Made my hybrid screw. Discovered that I need substantially longer holes for the screw to go through, as it just wasn’t straight enough. I’m also going to tap holes in the mill to make sure I’m tapping straight, instead of just quick doing it by hand.
Also discovered that I was adding negative clearance between the arm and the flag, which didn’t help it stay straight. Added a second side while I was at it and fixed clearance. Should print and test this tomorrow!
It printed successfully, even though I forgot to wait a while for the bed to stabilize at 80⁰C before starting the print. It looks like I added the right amount of clearance for the bosses on the fuse/switch module; it fit in easily but with no play. 315g of Snolabs Reicher Blue PETG. I haven’t yet assembled the electronics to test fit; I think I’ll wait on that until I work out some more of the wiring.
This picture looks weird because of the wide angle, but it looks wonderful to me. I used the black reset button from the otherwise failed print for some contrast. I’m holding it in place with a bit of kaptan tape; I thought of taping it in place for the picture, and then realized it will also make it easier to assemble in the end so I think I’ll leave it in place.
Wow, looking great. Very nice shine and the color is looking good. Glad to see things starting to come together.
Once you get all the kinks worked out and final assembly done you will have to get it posted with pictures and files (stl and native) on some of the mainstream sharing sites. It will be useful for others.
Great job.
Color is even better for real, rather than taken with a cell phone camera under warm lighting that makes a pretty aqua blue look a bit more like a yellowish teal. Not that I have anything against teal!
(You can see at the corners that the printer I made this on needs more tuning; I’ve been putting that off while printing PPE and trying to decide how to redesign my hotend mount for the bondtech that I’m waiting to install until I figure out the design I want, since I’ll have to re-do that then anyway.)
I’ll post pictures at least!
If the experiment works well, I would like to find the time to model it as a whole and share it. Right now it’s a mishmash of OpenSCAD, FreeCAD, SolidWorks, and What I Did In My Workshop To Work Around My Mistakes. 
If I do that, I’d like to model what I would have built, rather than things I’ve realized are “warts” either from mistakes or from silly design constraints. For example, I would change the Y stepper mount and belt path for sure.
Speaking of mistakes… I designed kinematic mount blocks that I’ll attach to the bed. Two of them have reference features (chamfered hole and slot) that need to match the locations of holes I drilled in the “frog” that holds up the bed. But I accidentally calculated the locations of those features in a way that would barely work on the 220mm nominal bed width of the original bed that came with my old printer, and not the 224.4mm wide piece of cast aluminum I have as the actual bed I’m using. I actually had them 6.4mm too narrow due to another mistake, but that I could have made work. So back to the shop to machine a few more parts!
…I forgot to lock the head on the mill before profiling, so I got the opportunity to do the profiling twice! But now I have kinematic mount blocks that fit.
Then there was the mistake I made long ago of drilling out what were supposed to be M5 holes with a 4.5mm drill bit instead of a 4.2mm drill bit. I determined that M6 acorn nuts would engage just fine in the chamfers I made in the kinematic mount blocks, but fortunately before I drilled the holes out with a 5mm drill bit to tap M6, I checked whether I had any of an appropriate length of M6 screws handy.
Instead, I wrapped some M5 screws in just one turn of teflon pipe wrap, then used loctite blue 242 in the holes and inserted the screws loosely in the holes. Should be cured by tomorrow evening, and hopefully it will work as “poor man’s helicoil” for this. I’m planning to use more teflon wrap when I install it for real, so it should be nice and tight and not wander. I hope.
It’s been over two weeks since I last summarized a “final” (hah!) punchlist.
Things I can think of so far that I would do differently if I were starting over:
I’m wondering if your light barrier solution wouldn’t be easyer without the moving plastic part, but using the screw directly as the light blocking part?
