Author Topic: Mechanical design questions  (Read 1145 times)

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Offline pca006132

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  • Posts: 5
Mechanical design questions
« on: Tue, 04 October 2022, 09:32:26 »
Hi, I am new to custom keyboards and just started making my own ergonomic keyboard design (a mix of Moonlander and Redox), I just finished the first generation prototype and is now thinking about a second iteration, and have some questions about keyboard design:

1. Is it better to add weights to a 3D printed keyboard? The keyboard feels a bit light now and will wobble a bit. Not sure about the tradeoff for keyboard weight, e.g. typical weight and how will this affect the sound of the keyboard.
2. What is the recommended material for 3D printing the keyboard? It seems that material will affect the sound of the keyboard, wondering if there is some sort of guide to choosing the material.
3. What is the best way to fix tilt legs in a certain angle? I just use a screw and tighten it until the leg can withstand certain torque without moving, but this seems not very elegant and requires a screwdriver.
4. Is there any guide for 3D print postprocessing that can make the keyboard look a bit more polished? The current prototype looks a bit rough and cheap...

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To add a bit of context to the questions, here are some pictures of my current design:
291998-0292000-1292002-2

The parts are either connected using screws or plastic rods that I custom designed with a little lock to lock it in-place. The next design will try to hide the screws/rods and improve on the appearance of the keyboard. The keyboard design will be open sourced after I finished the design revamp and tested the design. This uses WeAct blackpill for a mechanically stronger USB-C connector (through-hole!), instead of the fragile little teensy.

Offline cest73

  • Posts: 171
  • Location: serbia
Re: Mechanical design questions
« Reply #1 on: Mon, 10 October 2022, 15:36:59 »
2. ABS - it has overall the best properties among the viable options - so totally need an heated (65 degrees C) enclosure...

4. People reportedly acetone smooth the prints and then sand blast it to get the texture on top

Offline vvp

  • Posts: 873
Re: Mechanical design questions
« Reply #2 on: Tue, 11 October 2022, 06:56:33 »
I use acetone smoothing on ABS regularly. ABS dissolves in acetone nicely. There are 3 common ways to do it:
* acetone vapour chamber - too complicated
* "paint" with acetone - works OK but it is time consuming
* submerge part in acetone for about a second, pull out shake excess acetone away, let it dry on a glass - the most easy but you need a lot of acetone

I do not do any sanding. I do not think it is really needed. See some results of acetone paining here: http://deskthority.net/viewtopic.php?p=357496&sid=f7368bf4fa0926f33da8697da484c82a#p357496

PETG has similar properties to ABS but it shrinks a bit less. It is easier to print. There is a solvent for it as well but it is much less common and significantly more dangerous for your health.

Offline Leslieann

  • * Elevated Elder
  • Posts: 4330
Re: Mechanical design questions
« Reply #3 on: Tue, 11 October 2022, 13:22:21 »
Hi, I am new to custom keyboards and just started making my own ergonomic keyboard design (a mix of Moonlander and Redox), I just finished the first generation prototype and is now thinking about a second iteration, and have some questions about keyboard design:

1. Is it better to add weights to a 3D printed keyboard? The keyboard feels a bit light now and will wobble a bit. Not sure about the tradeoff for keyboard weight, e.g. typical weight and how will this affect the sound of the keyboard.
2. What is the recommended material for 3D printing the keyboard? It seems that material will affect the sound of the keyboard, wondering if there is some sort of guide to choosing the material.
3. What is the best way to fix tilt legs in a certain angle? I just use a screw and tighten it until the leg can withstand certain torque without moving, but this seems not very elegant and requires a screwdriver.
4. Is there any guide for 3D print postprocessing that can make the keyboard look a bit more polished? The current prototype looks a bit rough and cheap...

1.& 2. PLA has a tinny sound and rough feel, ABS sounds and feels good but hard to print larger than 6 inches. PETG is hard to glue but sounds as good or better than ABS and almost as easy to print as PLA (I did my PF65 without a heated bed). Nylon is too flimsy and prone to delamination, adding carbon fiber would help, but it's still difficult to print large parts due to shrinkage.

With 3 perimeters and 40% infill, it's strong, feels good and sounds really good, not the same as an aluminum board but still more pleasant than a common keyboard. My PF65 is about as stiff as a traditional steel plate keyboard. It's shockingly good, but it isn't built like a normal keyboard, which is something you need to consider when building entirely with plastic (normal designs are meant for a metal plate). As for adding weight, feet matter more than weight, better feet can make up for low weight but bad feet cannot be made up for with weight.

Wobble is either your desk or the print is warped, either due to the printing process or being bolted together. Probably all 3 and being too light and too stiff can make the problem worse. Unfortunately if you use a flexible print bed, there's almost no way to avoid some warpage. I use a THICK glass bed, lilly pads, glue stick and hot glue, and some creative stress relief internal cuts in order to force my parts to be flat. See the link at the bottom to explain some of this.

3. Bolt on legs, you have a printer, make different legs. It'll be more secure than anything that moves and odds are you never change once set anyhow.
4. There's tons of guides for post processing and nothing special is required for keyboards.


If you're concerned about connector stress, switch to a magnetic USB cable, it removes all stress from the connector. Personally, I like daughter boards and magnetic cables.

Check out my printed keyboard thread, it has lots of tips.
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