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Is there a path from 3D print to injection mold?

This topic contains 11 replies, has 6 voices, and was last updated by  Stan 1 year ago.

Stan s2019

Is there a path from 3D print to injection mold?

30/06/2019 at 23:46

So I got pulled into the 21st century and picked up a 3D printer. The printer works well but as expected is slow and PLA does not like summer temperatures. I would like to be able to make a limited number of copies of some prints using HDPE or PP with my injection machine. I tried making molds using plaster and also casting resin. The plaster still holds promise (first try was not well thought out). The casting resin appears to be too exothermic and heats/deforms the PLA.

Does anyone have a successful process to create an injection mold? Anyone been able to inject into a constrained silicone mold? Is there a process if you print with ABS? PETG?


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01/07/2019 at 00:57

How about using something like FIMO to create the mould?  It should be malleable enough to form around your 3D printed “pattern” – and then you might be able to split it into two halves, using a sharp blade, and remove the pattern. The halves could then be fired (cooked) in an oven, whilst hopefully holding the detail of their shape.  Fired Fimo is relatively strong, but you would have to see how it behaves during injection.  My guess is that it would be better than silicone or plaster, as long as the heat of injection doesn’t soften it (which might happen).

01/07/2019 at 01:24

I’ll have to look at all the clay options. FIMO with PVC may not be good for a 200C injection temp but some of the others may.

01/07/2019 at 08:14

The OneArmy Alpha site has a nice ‘howto’:

01/07/2019 at 08:23

according to this here, ABS is ok til 230 deg Celsius.

01/07/2019 at 09:01

It was a bit of a disappointment, last night, when I saw that Fimo used PVC.  I had always assumed it used some kind of thermosetting resin.
Looked at it many years ago, for home workshop rapid prototyping & ‘proof of concept’ purposes.  But as you say @s2019 there might be more suitable materials.
There are filled epoxy “putties”, that start to cure after kneeding, and there are 2 pack polyester-based “fillers”, which might work too.

I guess people might have written about these before, in the forums.

01/07/2019 at 09:55

Hi @s2019,
I also want to be able to make moulds from 3d prints, I’m currently working on the idea of lost wax casting of aluminium. Briefly this would involve coating a 3d printed original with a thick layer of melted wax, separating the wax off in 2 halves when cool, casting the wax halves in plaster of paris; when the plaster is hardened, heat it to melt out the wax, then fill the void with molten aluminium.
I’m still only part way through building an aluminium melting furnace but I’ll let you know how it goes.
Edit @frogfall Annoyingly it’s difficult for us to access what people have posted before on the subject without a proper Search function on the forum 🙁

01/07/2019 at 10:25

heya 😀

i managed to do that in a multiple step process !

Print object in PLA.

Make a little wooden box, hollow in the top.

Put 3D printed (PLA) product in wooden box.

Fill the box with a thermoset resin (so heat doesn’t impact the moulding process); i am sorry i can’t recall which resin was used, but it can be found “more or less” easily in specific shops. You also want to make sure the resin you chose is flexible.


Once the resin is dried; take out the PLA product of the resin mould, and put back the mould inside it’s wooden casing.


Tadaaa your compression mould is ready for use (just be careful to reinforce the wooden casing to be sure it handle the pressure applied to the moulding process!)
i posted a couple pictures on our instagram page https://www.instagram.com/preciousplastic_sartrouville/

hope it helps !
cheers !

01/07/2019 at 19:43

@donald, Thanks for the link. Unfortunately they are using a stereo lithography machine and a high temp resin. @pex12 , I will work my way up to ABS though the heat deflection temperature is around 100C. I want to try printing the part and making the mold first because it makes it easier to proof the part design and also the mold usually takes a lot more material.
@timberstar The parts I need in the near term don’t warrant the step to aluminum. I’ve dabbled a bit with aluminum casting (built a small furnace from a trash can) and may bridge the two activities at some point. By the way, I recently saw this https://www.youtube.com/watch?v=ooVUir_V2DM and am wondering if I should switch from my gas furnace.
@imuh , thank you for the description. from your instagram page, it looks like you are using silicone. That is on my list. I wonder though how it will take the higher pressure in an injection mold. Probably have to encase it very well.

I expect this to be an evolving process. Thank you all.

01/07/2019 at 19:51

thanks Stan; i meet our 3d expert in short; evtl. he has some more input on this; I am aware i pointed to printers not exactly available to most of us ..

05/07/2019 at 16:27

Here is a nice overview

05/07/2019 at 18:54

@pex12 thank you for the link. I’ll have to check into the flavor of ABS they mentioned. Right now I have some plaster molds drying to see how they perform. I had a couple of fails due to release issues so I went to the old school Vaseline release. I’ll see how it works. The plaster requires patience since it takes so long to fully dry.

The Cura slicer has a mold function that I have not tried yet but would be useful.

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