One of my trauma-driven development masterpieces. It has a 13 calibrating screws! (3 for each of two front-face mirror planes, 3 for laser plane, 3 for beamsplitter plane and last one for beamsplitter rotation). So it's very hard and (not so) fun to calibrate this interferometer. And it's very-very sensitive to literally any vibrations around itself. But working!

BOM: 45x d=3mm bearing balls; 18x M3x5x5mm heatset inserts; 1x M3 nut; 13x D=4.5mm L=10mm d=0.4mm spings (or any other compatible); 15x NFE 27-619 washers; 15x D=5.1mm L=9mm d=3.5mm bushings (optional); 16x M3x20 DIN965 Torx (or any other ISO 10642) screws; Silicone grease; 1x M52x0.75 lens filter base (optional); 1x K9 (or any other optical or not so) glass 20x20x20 beamsplitter; 2x 20x20 front-face mirrors; 1x 100mW (may be less powerful) red (or any other color) laser in similar casing as mine.

Build:

1. Print lower_base, lower_bushing, cube_turntable and table_bushing_nut. Insert heatsets, grease bearing ball guides (massive one in cube_turntable and lower_base). Install 30x (full ring side) bearing balls in cube_turntable and place it into lower_base. Then insert with some grease lower_bushing in lower_base and table_bushing_nut in cube_turntable. And insert M3 nut into table_bushing_nut*;
2. Print upper_base and cube_base. Place last 15x bearing balls into cube_turntable with grease and install upper_base. Screw it with x3 M3x20 screws and 3x NFE 27-619 washers. Insert 3x bushings into cube_base then add washers and screws and place springs on screws. Attach and screw it to cube_turntable. This is beamsplitter plane;
3. Screw lower_bushing and table_bushing_nut with M3x20. This is beamsplitter rotation;
4. Print 2x mirror_base and insert heatsets. Install bushings, screws and springs in lower_base as depicted and screw it. This is mirror planes;
5. Print laser_base and do same action as previous. This is laser plane. If you want to attach interferometer to DSLR camera, use 3x mount_part and M52 lens filter base.

Calibrating: Repeatedly calibrate each of planes then cube rotation until you get good circle interferention picture. Good luck with it!

Printing: I used Flashforge AD5M (0.4mm nozzle) with given parameters:

• Layer 0.12mm;
• Infil gyroid 15-20%
• Wall 3-4 lines;
• No supports.

Sources: All files created in Solidworks 2021.