I used support Material and Thred inserts M3.

Model is printed with 2 holes diameter 3.2mm for “industrial” Thread Inserts. 

I used repair Kit from Toolcraft here:

https://www.conrad.ch/de/p/toolcraft-to-5017518-gewinderoll-satz-30teilig-m3-1672506.html

Procedure: 

→ Print

→ remove Support Material  

→ Drill Thread in very slow speed and Right Angle. Don`t pass trough in once, remove Thread cutter and clean it. Plastic should not melt. If melting you go to fast. 

→ Insert Threat Spring with Insert Tool

What works for Metal also works for Platic.