Project:FDM Injection Molds
| ProjectInfoBox 3D Printed Plastic Injection Molds | |
|---|---|
| |
| Status: | first steps |
| Release Date: | spring 2026 |
| Initiator: | Lukas |
| Materials Used: | PHA, PP, PE |
| Tools Used: | FDM 3D printers, "HoliPress" manual injection press |
| Software Used: | OnShape, Tinkercad |
I am experimenting with FDM 3D printed injection molds for PP, PE and perhaps other plastics and will try to keep track of the progress on this page. Yes, seriously: molds made from thermoplastics to be filled with (other) hot thermoplastics without melting! Although hot glue molds can be a fun way of teaching the principle as well, this opens up new DIY recycling opportunities.
Please reach out if you have any questions that are not (yet) covered below or would like to try it yourself.
Mold Material
When I first got into the topic I thought I would finally have to go through the trouble and learn SLA printing with some nasty high-performance resins that cost as much as an entry level printer these days, but luckily I found the recently launched "future things" YouTube channel where FDM printed molds were demonstrated. As a massive bonus, the material used is actually compostable!
The magic ingredient turned out to be PHA (polyhydroxyalkanoate) which is only sold for 3D printing by a handful of filament suppliers. Hopefully this niche market will expand as more people get to know the stuff!
After battling its notoriously weird warping behavior, the material can be printed on any FDM printer and appears to hold what was promised: due to its relatively high heat deflection temperature, it looks just as on the first day after a couple of injections with molten PP (150 °C).
also see Material:PHA
Mold Design
Work in progress
The first test mold was purchased from Sustainable Design Studio as a ready-to-print STL so I could quickly get a proof of principle. But of course, that can only be where the journey begins and custom designs are in order!
Design aids:
- Sustainable Design Studio: How to Design 3D Printed Molds
- tutorial for creating a mold in Autodesk Fusion
- covers basic design strategies FDM and SLA printing
- ActionBox Mold Maker
- automatic mold generator for models that fit into the fixed 69 × 88 × 48 mm template
- decent for first feasability tests of other sizes as well (scale down & generate dummy to analyze demoldability etc)
- seems to have problems with highly asymmetric parts/split lines
- exporting costs $$
- Parametric two-part mold generator for OpenSCAD on Thingiverse
- looks promising, but not maintained for several years
- does NOT work in the Thingiverse customizer, but has to be run in a local OpenSCAD instance to load STL input from your PC
- place the desired STL in the same folder as the SCAD script and change "model filename" to your STL's name without any path (e.g.
sample-input.stl)
not suitable:
- Mold Maker AI
- beta version as of 2026-3 - see if you can spot it...
not every AI deserves the "I"
- beta version as of 2026-3 - see if you can spot it...
- 3D Mold Maker
- generates mold shells that may be suitable for some casting techniques, but not injection molding
Results
yeah, I also wish it was already time for that ;-)
