Polyurethane Foam casting molds

[jbowen205]

I am looking to do some casting of polyurethane foam and need molds to do so. I am trying to figure out what material would be the best to print the molds out of. I need something that provides a relatively high quality print as the foam will be a mirror image. It also must stand up to multiple uses and be strong enough for me to clamp together while the foam expands inside. Any ideas or help is highly appreciated.

[GIFT3D]

Hey jbowen,

It may be difficult to get a material that can be used as the mold as most filaments gave a rather low melting point about 200 degrees Celsius. Depending on the material being molded will determine what material you’ll need. There are metal filaments or other certain filaments which require higher temperatures. Unfortunately of you have a material with too high a melting point then it will just melt the mold so won’t work. You may be able to use 3D prints to make the mold, but 3D printing may not work.

Good luck with the mold. I hope you find a solution

[jbowen205]

I’m molding polyurethane foam which will give off very minimal heat as it cures so that shouldn’t be a problem. Thank you for the information hopefully won’t have to resort to metal filaments as my end plan is to take the foam and use it in lost foam casting of aluminum and bronze sculptures.

[baoutch]

I’Il use ABS, because you can finish it with acetone vapor, so it will have a perfect finish for your casting.

[clarion]

jb, you might want to try petg.

also, depending on the size of your molds, i might be able to help you if you need bigger mold sizes, up to 50 x 40 x 42 inches.

[Enza3D]

I’d suggest using a 3d printed model to cast a mold with silicone (specifically TinSil or PlatSil), instead of trying to use a 3d printed part as the mold itself; there’s a decent amount of examples on this out there, so if you google “cold casting 3d printing” you should see some good videos and tutorials (here’s a few Safe, Simple & Affordable: Cold Casting Turns 3D Prints into Metal - 3DPrint.com | The Voice of 3D Printing / Additive Manufacturing There are two ways to create custom objects out of metal with a 3D printer.). Essentially, you use a 3D print to make a mold, then use that mold to cast the actual resin or metal.

For high quality prints, I’d suggest finding someone who can print the past using an SLA printer and print in as small a layer height as possible. It’d still be advisable to sand the part to at least 800 grit (ideally 1000 or higher) to make sure the layer lines won’t show in the final molded parts.

[free_Joules]

How about casting aluminum molds or using nylon to print them?

[Enza3D]

You can cast aluminum molds using PLA printed parts fairly easily; It’s called “Lost PLA Casting” and is the similar to lost wax casting (Lost PLA Casting from 3D Prints). You could also use MoldLay instead of PLA to achieve the same effect; MoldLay was developed by Kai Parthy to mimic lost wax casting but it is pricier than just using PLA. The issue here is that the molds aren’t reusable.

If by printing nylon you mean making the mold itself out of nylon, I don’t think that will work very well. Nylon, while being a great heat resistant plastic, still has a much lower melting point than aluminum and 3D printed nylon does not have the same material properties as molded or machined nylon. If you want a more permanent (but still affordable) mold for casting, it would have be out of a high temperature epoxy (most are around 1300 degF, but some go as high as 3000 degF). This process would look something like this http://www.instructables.com/id/Home-Plastic-Injection-Molding-with-an-Epoxy-Mold/step7/A-nice-copy-of-the-original-item/.

[free_Joules]

3d printed Nylon is a possible foam mold. Is that right?

[Enza3D]

It is possible, although I really think making a mold with a specially tailored silicone will give you better results and durability. The issue with using a 3D print as the actual mold lies in mechanics of 3d printing itself; a hollow mold printed with a standard FDM printer is going to be difficult to clean up and require significant amount of support material, maybe even dissolvable support material, to physically print the object. My biggest concern here is you print a mold, only to have surface imperfections you can’t reach and you end up having to either re-print or spend a significant amount of time trying to clean it up. It’s definitely doable (he casts pewter in a PLA mold 3D Printed PLA Mold for Pewter Casting is Surprisingly Effective - 3DPrint.com | The Voice of 3D Printing / Additive Manufacturing) but it comes down to a matter of quality, and I really can’t imagine a 3D printed mold outlasting a silicone one.

Now if you just print a model of what you want the final cast to look like then make a mold from that, you’ll not only know exactly what your end product will look like, but you’ll have a much easier time cleaning any surface imperfections before casting. The process of making a silicone mold from a 3D print is very easy, and I think will cost less in time and money than trying to print a mold in nylon. This also allows you to print with technology that has much nicer surface finishes, like SLA.

[Derrick911]

Mr. Bowen,

This summer I am doing research on the viability of Polycarbonate printed molds in injection molding and am getting some neat results. My molds endure a lot of compression and i inject molten ABS into them so heat is no issue either. If you are yet to find a solution to your problem please contact me and we can discuss more.