3D printing enables rapid prototyping but lacks production-ready qualities such as smooth surfaces, temperature resistance and food safety. These attributes however can easily be added by combining 3D printing with casting silicone and urethane plastic for small batch production runs.
As long as you don’t need hundret thounsands of parts, this method should get you up and running without paying a fortune for a silicone injection molding setup.
When selecting mold making materials for 3D printed parts, it is important to be clear about the intended material for mold and cast .
Some points to consider are:
- Silicone such as Dragon Skin can be extremely difficult to stick to surfaces, except silicone itself.
- Urethane plastic such as Smooth Cast 310 is exotherm. This means it gets hot while it’s hardening.
- Some 3D printing filaments are more temperature-sensitive than others.
- Some 3D printing filaments are easier to post-process than others.
Having this in mind, the proper materials can be chosen basing on the desired material of the positive.
For PLA the following works nicely:
| Final Positive | Mold | Seperate | Seal | Release |
|---|---|---|---|---|
| Smooth Cast 310 | Dragon Skin 30 | Monster Clay | XTC-3D | Ease Release 200 |
| Dragon Skin 30 | Smooth Cast 310 | Sculptex oil based clay | XTC-3D | Universal Mold Release |
Please note that urethane plastic is exotherm:
- This requires a non-wax based clay to define the two-part mold. Otherwise the surface in contact with the clay will be full of air bubbles due to the melting wax-based clay.
- Hot glue is not a good choice for the mold as the glue melts again and the mold leaks. Better use glue + Acryl or Wood + Screws (+ glue)
Applying multiple coats of XTC-3D with sanding (400…1500) in between is highly recommended.
Degasing the silicone and urethane before pouring significantly reduces trapped air bubbles and increases the chance of success.