Tailortech released a great step-by-step video on how he designed, 3D printed molds and metal casted the replacment parts for his CNC. You can learn a lot of you want to do something simillar with lost PLA casting / investment casting.
First video in three part series:
Project Instructables page:
https://www.instructables.com/id/3D-Printed-Lost-PLA-Investment-Casting-Aluminium/
First video in three part series:
Project Instructables page:
https://www.instructables.com/id/3D-Printed-Lost-PLA-Investment-Casting-Aluminium/