Designing a Six Sided Mold

Let's cast a dice!

This seams and easy task, just a square with some spheres engraved on it. Well, it's ture, but creating a mold for it is not that easy, as the small dots needed to be milled vertically, so you need a mold for each side. Let's go step by step.

1. Design your piece

Let's start designing the final piece. This is the result we want to get in the third step of casting, first we will mill a wax mold, then we will cast the silicon mold and then cast the final piece.

In this case, just a dice. In this tutorial we will use Fusion 360, but you can follow it with any other software.

2. Envolve your design in silicone

Here we want to create a mass arround our design to simulate the silicone. As it has to cover all the faces, just make a big cube on top of your model, this will help you make sure you cover the whole object.

3. Cut the silicone mass in pieces

The next step is to cut the silicone mass in pieces, like this you will ensure that all the parts of the mold fit perfectly. To do it, create the planes at 45º (in this case because it's a square) to cut out all the parts.

The image shows only one of the faces as an example.

4. Embbed this part in the wax

Out of the last step we get 6 parts, the negative of each side of our final piece. Now we can substract them from the top surface of our wax brick, with a boolean operation.

5. Create the joins

To make sure that all the pieces of the mold are align, it's important to create some joins. Just draw one square on each side of each dice face, and then decide wich ones had to be positive and wich ones are negatives. Extrude them and you have your joins.

As you can compress silicone, it's ok if you don't let any tolerance between the positive and the negative, just squeez in the silicone.

6. Final touches

To finish the design, we have to make sure that the CNC can mill it without problems. The only thing we have to change are the inner straight corners. In our joins, we have 90º corners that the machine will not be able to mill as the end-mill is round. For this reason it's important to round the corners of the joins.

Finally, let's create some pouring and degassing holes on one of the faces to be able to cast it later. In this case int the face with the number 1.