Week 9: Molding and Casting

Files
Bunny For Molding stl
Fab Lab Pendant png
Note, Originally I did a bunny 3d print and casted using the bunny. I come to find out later that maching a mold is part of the weekly tasks, and milled out a sperate design that was not cast in the documentation.

Bunny Casting: Story Time
This week's task starts with teaching kids 8-11 how to use tinkercad and 3d printers. This winter I ran an activity on how to design snowmen in tinkercad, and it worked great. I needed to come up with a similar activity recently, but it is springtime and I didn't want to have them make snowmen. I ran the module with designing bunnies instead, and these are my initial bunny design and prints.

Using Smooth-On PMC 121-30 Liquid Rubber Compound, I made a rubber mold of the bunny. The rubber compound comes in two parts that you mix together for ~2 minutes and then pour into the shape. The bunny was double sided taped into the bottom of a paper Panera Bread company disposable soup cup, and the compound poured over the top of it.

A day later I had a rubber mold negative of the bunny, and preliminary tests freezing water showed the bunny making decent ice cubes, but the bunny ears would always break off.

Entropy Resins Super Sap CCR was used. The sap is prepared as per the instructions on the bottle, combining the resin and the hardener, stirring for two minutes, and then it is ready. Roughly two ounces of resin is poured into the rubber mold and allowed to set overnight. The next day, the entropy cast is removed from the mold, ears intact.

Machining a Mold using the Modela
Starting with the Champaign Urbana Community Fab Lab logo, I designed a pendant in Inkscape. The black will be the deepest cuts, and form the outline and the hole in the pendant. The grey is the intermediate cuts, and will form the lowered areas in the pendant. The areas in white will be raised.

The modela was used to mill the form out of machineable wax. Workflow is very similar to setting up a board to mill, however, "wax rough cut" and then "wax finish cut" was used with a 1/8" bit. In the 3d settings, I set the depth of the form to be from -0.1 to -3 mm in 0.2mm increments.


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