[NTLK] [OT] NewtCOM and its case 3D printing design

[Matthias Melcher]

Hi Doug,

I designed the dongle case in FreeCAD. I first made a model of all the circuit boards and connectors. This is later used to subtract or hollow out the outer case. Yes, things are a tiny bit larger, but not much. Som 0.1mm, some even less.

Next I added a box where later the hole would be for inserting the MicroSD, and cylinders for the light pipes, cones for the buttons.

The outer size and shape was done by measuring an original dongle, and recreated in FreeCAD, then shortened it a little bit to match the position of the USB-C plug. When designing the middle PCB, I already took the length of the original dongle into account, but I ended up a millimeter or so short because I changed the serial port plug last second to the shorter version.

Subtracting the inner shape gives me a hollow case that will fit the electronics very tightly. The oversized cube, cylinder, and cones poke out of the case, so when subtracting, they create holes. I was incredibly lucky that I found CPU boards that fit exactly into the old case. Designing a CPU board would have been a lot more dificult than the interface board.

The last step is to split the case into two halves, leaving indexing walls, so they can fit together and not slide when applying gluing. The trick here is to start with a cube that encloses only the lower half of the dongle. Then add walls or pegs or whatever where you want the indexing geometry.

The trick is to take the case into a boolean operation with that cube twice: use the difference to create the lower case half, and the subtract the cube to get the other half. By the nature of boolean ops, top and bottom half will fit perfectly.

Now all you need is a calibrated 3d printer. I happen to have access to a toolchanger, so printing the overhangs and cutouts was super easy (barely an inconvenience...).

The carrying case for the case is done the same way with the raw dongle as a negative. You can either "grow" the inner case to make some extra room. Or create 8 cases, shifted in x, y, xy, and z, xz, yz, and xyz each by the additional space you want, and bool it together as a union.

PM me if I can help you.


> On 12. Dec 2025, at 21:13, Doug <ispinn at gmail.com> wrote:
> 
> Matthias,
> 
> How did you model the NetwCOM for 3D printing? Did you start with someone
> else's 3D model? Did you approximate the different shapes you saw stacked
> on top each other and just kept adding and approximating until it was close
> enough?
> 
> When you made the cases for them, did you use the exterior of the NewtCOM
> then go +0.1mm proud of each surface to define the space it would fit into
> in its case?
> 
> I'm asking because I have two complicated, mating surfaces that need to be
> 3D modeled so they match complimentarily and since you seem to have done
> that already, maybe I can learn something from how you did yours.
> 
> Doug