SLA Printed Molds for Casting Urethane Foam Parts

This is a technique that I used with the FDM printer using ABS filament to directly print molds that would normally be CNC machined. It’s one of the main reasons for purchasing the Form1+.

This is the first test part using molds printed on the Form1+.

My first impressions are that it’s so much easier been able to see what’s going on inside the mold when casting. The only disadvantage is that the transparent surfaces are difficult to finish as surface defects aren’t easily spotted. For the final molds I’m going to print the Cavity mold parts (surfaces we will see) in grey and the Core mold parts in clear. This way I can have the best of both worlds.

Printing the molds with the Form1 is defiantly the way to go. The resolution you can achieve is incredible and once the Form1+ is working to spec. a whole new world of detail will be achievable.

CAD GA of Core mold, cast part & Cavity mold

Core & Cavity ready for action

Mold closed with part cast
Note - I had already removed the flashing

Core mold part removed

Awesome detail and accuracy


Cool, that looks like it worked awesome. Can we see the plane too? It looks like an awesome design.

I didn’t know this was possible.

Awesome work @Steve_Johnstone. Do you think the mold will hold up to multiple castings?

Defenatly ! The new clear resin is so much stronger then FDM printed ABS and I already get plenty of pulls from them.

There was a guy a while back that had even injection molded plastic into Form1 printed molds… exciting times :smile:



This is really interesting, I’m a casting artist and haven’t really considered the casting potential of my Form1 before now, I’ll certainly give this some thought, I hate mould-making the traditional way.


Fantastic! I’m molding silicone and urethane myself with printed molds, and also combo molds using silicone cavities and printed cores. These are exciting times! Great to be able to really prototype stuff in your own lab!

Yeah, I want to see that plane too :smile:


This is awesome, and may help with some of my projects. Any chance at writing a DIY walkthrough? I like the thought of making a mold in several pieces, fusing them together, and being able to cast a large part with the detail the Form1+ provides in the mold.

I have done urethane casting(of hard plastics with molds that I sent out to be SLA printed(on a Polyjet printer), before I purchased a Form 1+. The resolution of the Form 1+ is as good as the Hi-Res Polyjet parts and I’m looking forward to trying the same with the Form 1+. If you sufficiently draft the surfaces and clean up the surfaces, you can cast hard materials as well. I think clear resin might be a good option for this. Polish them to be clear(see threads about polishing clear parts and you should be in good shape.

Thanks all for the kind comments :blush:

@Annino, a while back I did a detailed series of video on 3D Printed ABS for Mold Making, but that was using a FDM printer… Playlist Link

I will be using the Form1+ to print the fuselage mold and each fuselage half will be made up of 4 cores & 4 cavities. I will use the first mold half to make my mistakes and refine things etc. There are still a lot of unknowns.

Then time permitting I will record and document my work flow for the second mold half, but that will be some time away. In the mean time I’ll continue posting my progress, good and bad.

@David_Oliver awesome I would love to see some of your work. I’ve printer some prototype EDF rotors on the Form1+ for this same project and tested them up 65,000 Rpm. It would be great to do a limited production run and casting them in one of the stronger mechanical plastic would be perfect.

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Your parts look great. You’ve done some good finishing on the mold parts. One more note about casting hard plastics: if the mold is not smooth enough, the parts can stick.
it might be a good idea to add ejector pins.

What kind of casting resin are you using? I use Smooth-On(elastomeric and hard plastics).

Can you post some info about your casting setup?
I use a pressure pot/vacuum chamber, which limits part size(it’s made from a paint pot, which was inexpensive, but works for smaller parts)

The mechanical test of the rotor is pretty impressive.

@David_Oliver I’ve only cast with Smooth-On rigid expanding foam, so my setup is very simple. I’ve been looking into GRP Vacuum Infusion for composites so a vacuum pump is on the “to get list”. All I would need then is a De-Gassing Chamber.

There is also a whole bunch of other things I would also like to try like vacuum assisted casting of aluminium.

What release agents are you using for your hard plastic casting?

I’ve used Mann Ease Release 200 and Smooth-On Universal Mold Release.
They are made for use with rubber and silicone molds, but seemed to do the trick for my 3D printed molds. Used those molds mostly for molding elastomer parts(shore A 70-80 fairly stiff).

I’d approach the hard plastic with a little caution. It may be worth the extra step of making elastomer molds, especially for more complex or larger parts.

For anyone in this thread that is interested to see my injection molded results. Please note that it was only an experiment at that time and can be strongly improved - especially as I had the wrong plastic to inject.

Hope it can help you

Awesome! I was just asking about this. Great news!


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