ErgoMechKeyboards @lemmy.world mptsounds @lemmy.world 1 yr. ago

3D printed Ergo kb parts: SLA vs. FDM?

Hi All,

I'm planning to print a plate & case for a handwired 46-key split kb. I have access to both SLA & FDM printers at a fab lab, so wondering which printer tech would be best to print various parts such as keycaps, plate, case etc. Function's more important than looks for me.

I'm allowed to use PLA or TPU for the FDM, and the default resin (ABS-like?) for SLA.

I'm thinking:

Keycaps: SLA (I want really thin keycaps)
Plate: ?? (not sure what's better for a thin & durable plate that allows a bit of flex when typing)
Case: FDM (Due to costs, and easy to embed screws & magnets)
Wrist rest (if any): FDM? Would TPU wrist rest be clean or comfortable?
Gaskets, extra layers (if any): FDM (cuz TPU)

What do you think?

25 comments

Your current plan is solid. Print the plate with fdm, though it can't be too thin. There are a few designs on thingiverse and etc. to get an idea on how thick.
- Hmm what's the rationale to print the plate with FDM? Are SLA plates brittle or inflexible? (if printed with ABS)? I don't have much experience with SLA. And good point, I'll check Thingiverse for the thickness.
  
  It's just more due to the size and it being a mostly flat print makes it ideal for fdm.
  
  The main problem with SLA is the material and size. I don't think SLA can print ABS?
For my board, I printed keycaps, plate and case all with FDM in PLA.
- Dude, what settings did you use to print those? Did you do any post processing? They all look amazing
  
  No post processing on any of this. The case and plate were just with my standard printer settings, nothing special. For the keycaps, I printed them at an 80° angle so the stems would be stronger and used organic supports. 0.1mm layer height and oriented so the layer lines are along the finger travel direction so you don't notice the layer lines in use very much
- Wow, that looks gorgeous!!
- Can you share the files for your case? I'm wanting to make the same (Hillside 40, no?), but can only find files for a 46, and am hoping to avoid the learning curve needed for 3d modeling. Thanks.
  
  This is actually my fork of the Hillside with enough PCB changes that the case won't directly work with the original hillside unfortunately. Here's my repo: https://github.com/wannabecoffeenerd/hillside
You’ll want to coat the SLA parts in paint or some other coating that will block UV as they will turn yellowish and more brittle over time from UV. Also, a lot of the TPUs are pretty hard ~90 shore A, so check the hardness value compared to what you’d prefer.
- Thanks for the input. I'll definitely spray paint the SLA parts. Not sure if spray painted keycaps will feel more "slippery" but I'll test first with some of them.
  
  Good point with the TPU. I'm not sure what's available, but probably Ninjaflex (so 85A?)
  
  You could SLA print a key cap to make a silicone mold then use something like Epoxy to make the final key cap.
  
  I've been printing sculpted palm rest prototypes in ninjaflex, because i had some on hand, but if i were you I'd buy ninjatek's Chinchilla. 75A and tested for skin compatibility.
  
  i think its a reasonable idea, the TPU seals in air so its like a pool inflatable. TPU likes lower layer heights and you can get away with 5% infill but any less and the top surface will have holes in it and loose that pillowy feel. might need to go higher for a smoother surface. I recommend a non-crossing infill (otherwise you get blobs on the nozzle that will ruin your surface feel) and one that alternates directions, rather than stacking lines, so that the infill has more give. i tried gyroid at first, but 3D honeycomb was noticably softer because it alternates.
  
  also, avoid sharp edges and corners in your design and slope the sides, don't have them vertical. this will also increase the softness
  
  I've been printing sculpted palm rest prototypes in ninjaflex, because i had some on hand, but if i were you I'd buy ninjatek's Chinchilla. 75A and tested for skin compatibility.
  
  i think its a reasonable idea, the TPU seals in air so its like a pool inflatable. TPU likes lower layer heights and you can get away with 5% infill but any less and the top surface will have holes in it and lose that pillowy feel. might need to go higher for a smoother surface. I recommend a non-crossing infill (otherwise you get blobs on the nozzle that will ruin your surface feel) and one that alternates directions, rather than stacking lines, so that the infill has more give. i tried gyroid at first, but 3D honeycomb was noticably softer because it alternates.
For wrist rest, you can stick a piece of TU leather to cover the printed surface, so it will look nice, be clean and comfortable. Not sure if TPU is sufficiently soft if you want a soft wrist rest, you would probably need something like silicone.
- Nice idea! Do you mean on top of the switch plate? I'm still brainstorming the design, but it will have a removable layer on top of the plate to hide the switches' legs (I don't like that "naked" feel) & keep some dust from falling inside the kb.
  
  I just did it for the wrist rest, as that is the part your wrist will touch regularly. It is too much work to cut many holes if you want to cover the plate, and I don't think it will be much cleaner comparing with bare printed surface. You still need regular cleaning.
It's just more due to the size and it being a mostly flat print makes it ideal for fdm.

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