Week 13 Casting moldy spells

Casting moldy spells

This week we poured different kinds of liquids into hollow objects made from different kinds of materials. Some of those liquids were extremely toxic, some of them were only somewhat toxic.

Making molds

Casting requires a mold, which has a hole or an imprint of the object you are trying to cast. These negatives can be either carved directly or cast from a positive premade object.

There are a couple of methods to carve a mold. The most precise way would be to do it by hand, this way there would be no artifacts from the digital manufacturing methods, like rough angles or rounded corners, unless intented. But this is a digital anufacturing course, doing things by hand is obsolete! Other methods include CNC-machining and 3D printing.

We decided to machine our mold from modeling wax.

The process started by taking a model from Autodesk Fusion, and importing it as an stl-file. It was a model for a positive mold of a key casing for a keyboard. We moved that file to another computer that was connected to the Roland milling machine, and opened them with Modela Player.

Model player

There we did the following steps:

We oriented the model correctly from Model -> Model menu, where we rotated the piece correctly, and set the origin to the bottom left corner (when looking from above).

We selected the proper material from the material drop down menu.

After that we created a tool path for surfacing by pressing the new tool path button, and going through the tool path wizard. For surfacing, we selected the correct milling bit and increased the surfacing depth to 1mm to accomodate the extremely uneven surface of our wax block.

Then we created a tool path for roughing. Again, the same tool as the previous paths. Also reduced the area to only include the internal bits of the mold, so that the milling machine does not rough the outer edge of the mold.

Similar changes were done for the finishing tool paths.

Then we exported the tool path files (three in total) by pressing the Cut button in the bottom right corner, and selecting output to file.

Roland milling machine

We fixed the wax block to the bed by creating a make shift double sided tape by adding tape to both the block and to the bed, and hot gluing the tapes together.

After turning on the machine and opening VPanel (and trying to figure out how to have two VPanels open at the same time because there was another milling machine running at the same time), we changed the milling bit, and set the origin. If you wonder how that can be done, read our previous documentation on the subject

Then we took all the files exported from Modela Player and added them to the VPanel. This was done by pressing Cut and adding all the files using the Add file button. We made sure that the files were in the correct order: surfacing, roughing and finishing.

We also made sure that the Vpanel uses the RML-1 command set, as that is what Modela Player exports as.

Alea iacta est

We cast things from three different materials.

Material	Object	Toxicity
Smooth-Sil™ 936	A negative ring	Basically none
Dragon skin™ 10 Slow	Gleb's weird project	Basically none
Smoothcast 305	A negative ring and a different positive ring	Very
Smooth-Sil™ 940	Negative keycap for keyboard	Not really

Casting was simple. We measured the volume by adding water to the mold and weighted it. Then we mixed the two parts of all the materials as per the instructions printed on the bottles. The problem here was that all molds need to be poured studd according to their volume, but we were measuring all our materials by weight. For water that is fine, as 1ml of water weights 1g, but that does not hold true for other liquids.

We had many molds at out disposal.

And we made many different things.

There was no much difference between milled and 3D printed mold, at least as far as our eyes and finger tips could discern. The silicon was harder to extract from a 3D printed one; there was probably some form of adhesion happening between the materials.

Toxicity report

Smoothcast 305 is toxic. You should not touch it.