Mechanical designs for 3D printing

Many of you have access to a 3D printer. Here I collect some designs I made in FreeCAD to solve different needs in optics and electronics development. The designs are taking the strengths and weaknesses of 3D printing into account to get the best result. There is .stl file for direct use in your slicer and also the original FreeCAD project so it can be modified for particular fit and needs.

Lens Holder

In optical setups we use lens mounts for positioning lenses in the optical path. Hopefully you have good quality metal lens mounts for your critical optical paths where stability is critical. There are situations where you run out of mounts while experimenting or you just need to place a filter. In those case it can be handy to 3D print your own lens holder. 

With the 3D printed lens holder it is easy to accommodate odd lens diameters. Below are .stl model ready to use for various lens diameters. In the FreeCAD project the lens diameter is a spreadsheet parameter. Just open the FreeCAD project and open the Model spreadsheet and change the value of d and the model recalculates for that lens diameter. The lens holder mounts on a 12.7mm post. It uses a standard M4 hex nut for mounting on the post. An M3 screw and nut is used to clamp the lens or filter securely in the conical grove.  

Dual post holder

The dual post holder is a case for the electronic- optics boarder land. I needed some optics setup at my electronics workbench, just a bare fiber launch to a photodetector. A small breadboard would work, but just the bobble post holder alone was good enough.

The holes for the posts are non circular, so the post contacts in two lines and the fixing screw. The M4 thread for the fixing screws is modeled but it is good to cut up the threads with a thread tap.

The two posts are spaced by 25 mm. Such setup is particularly useful for placing optics in front of a post mounted photodetector. For filters, like ND attenuators and spectral filters there is not need for focusing so a fixed position is fine. A short focal length lens can also be used to collect light on a detector, with this simple portable setup.

Probe Holder

The oscilloscope probe holder is another example where you can 3D print something useful to free up your hands. This design is inspired by commercial probe holders, that are shockingly expensive.

The 3D printable probe holder body has M6 threaded holes. Use M6 screw around 80mm long in these holes as legs. One of the holes extends all the way to hole where the oscilloscope probe fits. Feed a piece of nylon (~25mm) into that hole so the M6 screw press on the probe. For the nylon piece the thickest edge trimmer string works well. The two M6 screws serves as a weight, to keep the probe in place and supporting legs and one of them as the fixing screw for the probe.

Mounting Bracket

Way back when, I found that the most minimalist way to mounting a small PCB on top of an optics post was with an angle hex part holder. They can be hard to get by and the angle can deviate quite a bit from 90 deg, so I made my own.

It is a very simple piece, just an L shape with two threaded holes. If the two M4 treads print well then it is a lot of functionality in a 3D print job.

Download

Below is a table with download links to the .stl models and .FCStd source FreeCAD project. They are free to download, use and modify, if shared please acknowledge this original source. The FreeCAD version used for these models is Version: 1.1.3.44987 Flatpak installation under Ubuntu 24.