Week8 Molding and Casting

design a 3D mold, machine it, and cast parts from it


Back to BeeFab Project

After the 5th week's issues, trying to 3d print honey comb for the BeeFab Project I choose to afford the same subject with the molding and casting technique.

From Wax to Wax

Process and materials

After comparing different molding and casting materials I choose to make a previews positive mold milled in wax, make a oomoo25 silicon rubber negative mold from it,and then try to cast with bees wax.

Simplifying the design around the tool

I simplified the design into a flat pattern to bent in a second face. To optimize material, milling time and make it adaptable to different shapes. I scaled the pattern, to obtain a maximum cell's deep of 3 mm, according with the ending part of the smallest tool I will use. Than I add 2 traversal pipe having a central funnel one to fill and one to leave the air comes out.


Positive Mill

To create the positive mold in wax I used the Roland SRM-20 Monofab. Due to internet connection issues in Green Fab Lab, I could not use on line fab modules, and the version downloaded don't have SRM-20 driver. I used the Roland V-cam software.

The rough...

Not at the first time

The first milling failed due to a wrong collet. The 1/8 flat 4fl milling bit was not well centered and spindling gave an error of more than one millimeter that made disappear the 2 mm sides walls.

...and the finishing

in 2 times

I divided the finishing milling procedure in 2 steps in order to take the milling bit into a safe distance from the frame's walls limiting the mold, that are the only vertical element dipper than 3 mm. In the same time I saved time passing from 4 hours estimated for the all internal surface to 2 steps of 60 min.

Negative pouring

mixing an mixing again

Th omoo25 has a pot life of 15 min and need to cure first 75 min in 23°C. By instruction vacuum is not necessary but we choose to built one just to be sure.

Actually mixing the 2 component for 5 min I create a lot of bobble that becomes even more pouring the rubber fluid as accurate as possible having just 15 min. The vacuum we built at last didn't look doing his job.

I left the mold curing in a incubator to be sure to have a temperature higher than 20°C. The Green Fab Lab is in the mountain...but was not enought...

Casting test

Before making a new rubber mold choose to make some casting test with commercial wax.
The silicon appear more flexible than expected and probably is bending in the middle loosing the 1mm plane surface designed between the 2 faces.

the best results

dowload file:rhino files