Dec 25, 2023

How to fasten a cover with the frame, or how to make feet coplanar?

First, in P2PPCB, keyboard cover is lower and frame is upper. In covered style keyboards, a cover keeps feet. See P2PPCB NTCS keyboard.

Second, keyboards have feet, and they should be "coplanar". If not, the keyboard rattles on your desk top because one of the feet is shorter than others. If all feet have the same height (no rattle), they are "coplanar".

Let's get down...

3D-printed parts are always warped. Everything in the real world is always warped mathematically, of course, but the degree of 3D-printed parts' warp is often larger than your desk top. Rubber feet is indispensable to cover the warps (including your desk top's). But large keyboards may require more warp correction.

I found that MJF warps much more than Somos Ledo 6060. This is a big reason why I switched from MJF to Ledo 6060. I think that you don't need additional warp correction as far as your products are in your hand or laboratory, not very big, and you use Ledo 6060.

Out of the laboratory, you will need covers, and may need additional warp correction. This is the story of them.

Pole clamp structure

We see pole clamp structure everywhere. A pole (cylinder) and a clamp which keeps the pole, that's all. By loosing / tightening the clamp screw, you can move the clamp steplessly.

P2PPCB NTCS keyboard adopts the pole clamp structure to fasten the cover with the frame and make the feet coplanar. The video below shows one of the clamps of NTCS keyboard:

Pole clamp structure is good for covering the difference from the design to the real thing, because it has adjustment margin. But, how does it make the feet coplanar? See the figure below:

When you are tightening the screws, keep the parts deformed by hand. If the deformation is a good balance, the feet become coplanar. Usually a frame is stiffer than the cover (NTCS cover is limply when it is not assembled) so just forcing the cover flat is enough. Theoretically the cover doesn't become flat after releasing the hand, but usually enough.

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