MAKING

Goal: Make a lego base for containing plants that is 8x8 unit dots.

More precisely:

• Perimeter: 8(width) x 8(width) x 2(height)
• Interior: 6(width) x 6(width) x 1(height)

PROCESS OVERVIEW

Design: create a CAD model of desired final product.

Mill: Machine cut a wax block to create a positive of the design.

Mold: Pour material (silicone) into the block to create a negative. This is the mold.

Cast: Pour material into the mold to make the final product.

CAD DESIGN

I started with a true lego model and measured dimensions.

Designing lego models is a great use case for parametric modeling with CAD. I found some great pages on the subject, created by hobbyists, along with helpful diagrams that aided measurement.

I used fusion 360 to create a model of my lego part.

A design goal was to create the lego part with knobs that could fit it to other lego parts. Since an oversized knob would prevent that, I tried to account for possible errors by designing my knobs slightly smaller than the official size (diameter 4.6mm vs 4.8mm).

.stl file

MILLING

I used the ShopBot Desktop to mill into the wax block. The wax block is 3” x 3.5” x 1.5”.

At the time of designing, I knew that creating a lego part of 8 dot units would be cutting it close (pun intended), given that would result in a 64mm lego model, dangerously close to the wax blocks borders.

The rough cut did not break through the wax block’s walls, but the finish cut did.

After milling, I patched the wall with cardboard.

MOLDING

I used oomoo to create silicone molds from both the milled wax block, and the original lego model.

A mistake: I did not mill deeply enough into the wax block, so the walls of the resulting silicone mold were not high enough.

I was glad I had also created a mold from the original legos so that I could use that mold instead of the mold created from the milled wax. But I first still had fun with the failed mold.

CASTING