DIY rapid injection molding

How difficult would it be to DIY rapid injection mold (plastic parts)? My understanding is that rapid injection molding means injecting hot plastic into a mold which was 3D printed. Seems this would be possible with a machine like this:

I’m thinking this would be helpful to do in-house, after functional prototype tests and before short runs with a service like QuickParts or ProtoLabs. I think I’ve only seen one example of this with a Formlabs printer:

Yes it can be done. How difficult? No clue, but let us know if you try!! I assume outsourcing to someone like Fathom who already has this set up would be a good use of outsourcing. If you think you will be doing this sort of development a lot though, then I am sure bringing in a manual machine would be beneficial. I wouldn’t expect it to be as plug n play as a Form 2 though.

1 Like

Hi Captain Bisquick,

it’s surprisingly easy for small parts! We just finished up a collaboration with Galomb Inc and shared our findings in the whitepaper which went out today.

Definitely interested to see how others want to push this forward and try more elaborate things so please share your results on the forums! Happy to talk more about your specific application if you need any help figuring out the best approach.

1 Like

Another option is casting the parts. Smooth On makes some castable materials that act a lot like ABS (Task 21).

This can save you a boatload of cash if you don’t need parts that are extra rigid or fiber reinforced. It’s urethane so it’s reasonably safe to work with also.

1 Like

Wow, great replies! Thanks everyone. Looks like my timing was perfect too, seeing as the white paper was release just days later.

I sent in a ticket to Formlabs and they are checking for me to see if there would be a reaction between Polyurethane resin and the Formlabs resin as I was thinking of using the tough or Flexible resin as a Mold and just pour in the Poly replacing the need for Silicone Molds. (I use Smooth-On 321 and a few others)
If a person can get more then 50 parts from a printed mold this may be a viable alternative.
Main reason I am thinking is I do a lot of thin parts and experience a lot warping whereas a printed mold can have a thicker outer wall thus eliminating the warping. Here is a couple of screen shots of one of the items what I make for the hobby industry.

I’ve molded smooth-on simpact urethane resins (Shore A 60 and 85 IIRC) in printed molds before. You MUST really, really, really release them well prior, polish up the released surfaces with a soft cloth, and re-release/polish before every pour.

I made the mistake of not releasing my first mold for simpact because I’d molded silicone parts a bunch of times in printed molds, and they came right out. With simpact, and no release agent, I had to basically break the mold off with a hammer!

I made a big gasket for my champaign bucket vacuum chamber using a four-section printed mold.

I’ve since added another stick-on seal to the urethane, as busting it out of the mold was not too kind to it, and it had a couple rough spots that leaked a bit…

1 Like

Thanks… Doesn’t look like it’s worth the headache…I’ll spend my efforts towards the injected plastics

It is not difficult to do the injection molding - you can see this under

There you find as well how to design the molds. Have fun with it :slight_smile:

1 Like

Pauline, injecting wax should be easier than plastic. With the much lower melting point, your mold will experience much less stress, should last longer, and not require as much engineering consideration.