Mold design

I am very confortable with 3D printing than opperating a CNC machine. To create my mold I had 3D printable geometry in mind. I wiil print it from PLA filament

The Geometry

I stared with a simple sketch in my notebook

Then I moved on to SolidWorks. Both the Mold and Combine features don't work in my SolidWorks packge. So, I designed the mold not the part in SolidWorks.

I sent it off to print, then i found out it was too big for the printer we had So I had the change the dimensions. (The screenshots above are the current dimensions).

I printed at elast 5 times, most of them coming out unven on a few spots of the inside due to minimal support. I was using minimal support to reduce the work in sanding. I also sand the 3D printed molds to increase the smoothness by eliminating the layer visibility that would Latter occur on the wax after casting.

The mold fluid: Bee WAX

The last mold I ended up using was half printed as i ran out of filament, but then realised it actually looks interesting (Like old Greek Vessels). I sanded the inside, mounted the two faces into the bottom. The bottom piece as seen on the design and previous orints above, holds the mold together, and also creates a pointed tip on the cast as seen in the casting and mold peeling videos below.

Post processing: Sanded Vs Unsanded mold surfaces

The left side shows us a very minimally sanded (almost not) mold result. It shows the stripes that are a result for the visible layers of 3D printed PLA molds or materials in general.

On the right side we see a drastic difference in surface finish. I approached a guy at our fablab with a huge experiecne sanding. He taught me this technique of wetting the sand paper before applying it, and it works wonders in the eyes of a beginner in surface finishes in general. I was impressed with the smoothnes that resulted when I did it firts.

I think the surface finish can get even better the more experienced you get.

Before the last shots, it's important to know that a sanding paper that isn't very new or very old is the sweet spot for this kind application: surface finishing (sanding) plastics.