3D Printed Rubber Mold

I took a mold making workshop this past spring and wanted to see how I could combine 3d modeling and mold making techniques.

Step 1: Make a 3d Model.

While modeling, of course, keep in mind the build volume and resolution of your 3d printer.

Step 2: Model the Mold.

I drew a box around the object in Rhino, split both the box and object with two planes, then joined the appropriate pieces into this three part mold. Trim the mold in order to keep it as small as possible...this will save printer material. At the same time, maintain a boxy shape so you can clamp it shut. I made the mold pieces interlocking with small bumps and indentations. If you're printing with ABS or another filament with a warping tendency, these interlocks could fall out of alignment. You can always sand them down if necessary.

Step 3: Print and Prep.

Print your mold...Then set up a work station outside, or in a room with proper ventilation.

You will need the following:



Packing tape

Paint stirrers

Latex gloves

Spray release

Large plastic cups

Poly PT Flex 70 Rubber Kit

Flathead screwdriver

Step 4: Apply Mold Release.

Spray everything a couple times, including around the mouth of the mold.

Step 5: Seal the Mold.

Assemble the mold and cover all crevices with tape to help prevent leaks.

Step 6: Clamp It.

Clamp the mold as tightly as possible.

Step 7: Measure Out Rubber Parts.

Pour equal amounts of part A and part B into separate cups. Take extra care in measuring.

Step 8: Mix Thoroughly.

Mix parts together, then pour mixture into third cup and mix once more. This ensures an even distribution.

Step 9: Pour and Cure.

Position your mold over the bucket to catch drips. Prop it up to make level if necessary. Let the rubber cure for at least one hour.

Step 10: Remove Cast.

This may take some work. Use a screwdriver if needed.

Step 11: Done!

There is always something that could be improved upon. Personally, I think I should have spent more time orienting the grain of the print!

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    8 Discussions


    5 years ago on Introduction

    I thought the instructable was very nicely documented. However, it felt lacking 3D specific details. It seemed more of a useful mold-tutorial (which I want to learn more about generally) than anything else.E.g, Step for making the mold is just "design a mold." It looks like you used a special program to go from your CAD file to the mold.

    One thing I've found that's great for 3D printing molds is that you don't have to make it thinking about the mold so much. You can focus on the object, and then use program like openSCAD and some free scripts to turn that into a custom mold. Sort of like what it seems you did, but without needing an expensive piece of software (I'm not certain how you make the mold, though.)

    4 replies

    I did not use a special program. I drew a box around the object in Rhino and used the simple commands "boolean split" and "join" to make a negative form in the box! I'm sorry this was not clear.

    Cool! I guess Rhino is a relatively affordable cad modeling program. It's not as expensive as inventor or solidworks. But it is still out of the realm for most users, at $800+ if I'm not mistaken

    Do they have any consumer versions maybe?

    You can actually download the mac version of Rhino for free because it is still in development! If you're a student and PC user, then the price is $200. Otherwise, yes, it can start to get pretty expensive!

    sweet! Thanks; I'll definitively keep this good info in mind. I might want to get into a brush based cad program soon. But also want to learn more about other paradigms like openSCAD. :P. Too many neat making things abound


    5 years ago on Introduction

    You can also o acetone vapor deposition on 3d printed abs. This would remove the print lines. In tight spots where the vapor would not reach you can paint acetone on and smooth your print before hand.

    2 replies

    Reply 5 years ago

    I don't think acetone vapor treating is going to help those print lines. Keep in mind intentional edges will also suffer degradation. The solution to this is to print at a much lower layer height. 50 microns would probably do the trick. Since you are making a mold, the time investment in the print is outweighed by the rapid repeatability of the end product.

    These are excellent suggestions. Attempting to minimize the print lines is definitely an option. At the same time, I was excited to see how the lines would look in the final cast..they are a unique detail that gives it some added interest.