Assignments
- Design and produce something with a digital fabrication process (incorporating computer-aided design and manufacturing) not covered in another assignment, documenting the requirements that your assignment meets, and including everything necessary to reproduce it. Possibilities include (but are not limited to composites, textiles, biotechnology, robotics, folding, and cooking.
Subject¶
As part of my final project I need to make a juice collector. It must be waterproof, slope, and adapted to the size of the vermicomposter.
Design¶
From the 3D model of the vermicomposter, I draw the shape of the tray. The low point is at the bottom left, it’s why there is a hole to route the worm juice into the tank.
From the 3D model of the tray and using the combine function I designed upper and lower molds and I left a gap of 2mm between them to get a 2mm thickness tray.
| Upper mold | Lower mold |
|---|---|
 |
 |
Process¶
Machining the molds¶
From the STL files of the molds I machined it using Vcarve and Shopbot PRS Alpha (to know more about Vcarve and 3D machining look here).
I used a a 6mm end mill for the roughing path. Then I used the same end mill with a small stepover for the finishing path.
I post-processed the molds with chisels and sandpaper.
Casting test¶
Before I started, I did some casting tests to find out what technique to use to remove the cast of the mold. I tested cellophane and paraffin paper. Unfortunately I used an epoxy resin too old that has not hardened. I could not know which technique to privilege… Finally I used both !
I finally used the Task18 Aluminum from Smooth-on to cast:
Casting¶
| Coating the mold with paraffin |  |
|---|---|
| Wrapping the mold with cellophane |  |
| Casting resin (Smooth-on Task18) (1) |  |
| Adding cotton fibers |  |
(1) : During this first casting I realized that I did not mix the product well. I had to redo the casting with the product properly mixed.
| Pressing the mold |  |
|---|---|
| Big bubble !! |  |
| Piercing to add the funnel |  |
| Installing the funnel |  |
| New casting to fill the hole |  |
| After sanding |  |
| The repair is very porous |  |
Result¶
The use of a vacuum pump would have avoided the formation of this big bubble. The attempt to repair was inconclusive. The setting was too fast and the small bubbles did not have time to escape, which made the material very porous. To correct this defect, I will apply a varnish.