assignment 12

molding and casting

12nd week

The aim for this week is work with molds.

WAx milling

The fabLab didn´t provided the needed materials. We had to share the remaining space on a piece of wax from a student from the last year.

At the beggining, my intention was to make a mold of one cap for a potentiometer (Knob), and I built it in openScad.

I was thinking wrong about how to reproduce the knob, and I started to build a two-sides model. But I realized that the angles will be in trouble to mill, because milling head goes down vertically, not in angle. Also, as we had a little space for each in the piece, I decided not to do experiments just in case of having problems and ruin the assignment.

I want to do this piece (in vertical in one piece) when the wax arrives (if it´s on time).

But, for practice, I simulated the two processes for mill a mold from a 3d Model. And better idea, a flat surface for the knob, with no teeth or angles.

First, load the STL file to fabModules and generate the heightmap. Note: the model should be faced up to the software be able to generate the heightmap.

It´s needed to do two processes, rought cut and ending:

Rought cut:


So, I decided to try the gray-image method with something smaller, like my logo; following Neil´s instructions to solve the practice altought the lack of material I had for this assignment.

First I made a test on foam. We used a flat 2mm milling head.

And then in the wax:


First I covered the piece with an unmolding spray.

Then, mixing the final mixture, silicon and a 5% of catalyzer.

Then, mixing the final mixture, silicon and a 5% of catalyzer.

Let it dry during the weekend!

The piece has some bubbles, but it setted up properly.

I melted some crayons to check if the mold was ok!

Little crayon logos!!. I dont know why the milling process didn´t ended completely, I dont have the 4 walls for containing the material.

Mixing arabic gum with red crayon leftover.

Fancy golden depilatory wax.

As an extra, we intended to cast with metal. At the university they have the proper space and materials for that. The professor told us to made a mixture of plaster and silica (50% - 50%) to last against the owen heat.

I selected the same 3D model from the 3d printing & scanning assignment.

The first layer looked good:

But I realized that the mixture was deficient, It took 3 days at the lab drying and it was still wet.

It resulted on a very low-res milling. Failed test. We didn´t had time to mixture a new block to test it.

Failed attempt :(

Fabmodules logo file

Half Potentiometer STL test

Piece A STL

Piece B STL

openScad Customizable Knob

Soft Knob STL

Terrain routine 1

Terrain routine 2

Terrain STL


Explained how you made your files for machining


Shown how you made your mould and cast the parts


Been surprised today


Described problems and how you fixed them


Included your design files and ‘hero shot’ photos of the mould and the final object