How to 3D print a custom mold

How to 3D print a custom mold

Time for this project to take shape.
  • by Ash (154)
  • Time to complete: 2 hours

3D printing your own custom mold is a great way to bring a new level of creativity to your project. From the computer to fruition, this is one of the most versatile things you can accomplish with a 3D printer. Custom molds are great for a variety of projects. On the crafty side, you can make things like pendants, bracelets, and stamps. But don't rule out the industrial side of this project. Silicone molds are great for duplicating things like machine parts, tools, and grips.

This guide has everything you need to get started. As with most of our guides, you're only limited by your imagination—and that's just the way we like it.

1

Create or find a design for the mold

Using 3D software of your choosing, design the model you want to create a mold for. You can also find a 3D model to use online. I'll be using Blender to create a mold for the howchoo logo letter h.

2

Create a mold from the design

I'll be covering two distinct mold types and how to create them for your model. There are two part molds that can be easily assemble/disassembled. The other kind we'll cover are known as flexible molds. These molds can be reused for casting purposes.

Two-part mold

Two part molds can make your model in two halves separately, or be combined to create the model all at once. I've created a two part block that can be scaled for your project and used for both methods. You can download the two-part mold from Thingiverse.

Using a 3D modeling program of your choice, overlap the custom model with the two part mold block and cut a hole with it. I'll be using Blender to accomplish this. If you'd like to follow along with me, use a boolean difference modifier to cut the object from the mold. You can learn more about cutting objects with the boolean modifier here.

If you’d like the model to set as one piece, you will need to cut a hole in the block for silicone to pour in through. The two halves can be held together with rubber bands or tape. I created spherical notches to keep the mold perfectly aligned.

Flexible mold

Flexible molds are really neat because of their versatility. We're essentially creating a mold for another mold. The final product will be a flexible piece of silicone rubber than be used for future casting. This is ideal for things like jewelry, cosplay, and other crafting needs.

To create a flexible mold, start with a block and position a smaller block to overlap with it. This block will form the edges of our flexible mold. Using a boolean difference modifier, cut a cavity from the starting block. Place the desired design inside the cavity. Consider the angle you use when placing the design, as this will affect the final mold.

3
Print the mold

Once you've created your mold design, it's time to print it. Export your creation to an stl file and slice it with your favorite slicer. I'll be using Cura to print these molds with PLA at 240° with a layer height of .2mm.

4

Cast with silicone rubber

When the molds are ready, it's time for casting. I'll be using Oomoo 30 for this project, but I encourage you to experiment with other materials. Pour the silicone into the mold. Go slow and be careful to fill all of the gaps.

5

Complete final touches

Be sure to give your mold plenty of time to cure. Carefully pull the silicone rubber from the 3D printed mold. You may need to finish up with a few final touches. Cut away any excess silicone and clean up rough edges with an X-acto knife. Congratulations!

If you enjoyed this project, check out our guide on how to 3D print custom stamps.