Using vacuum to draw your hot wax into your mold?

Hello Forum,

I have a part I need to cast in aluminum or brass. I created a good Smooth-On silicon mold yesterday and it cured over night. I have tried twice to fill the mold using only gravity but I am not getting the entire mold filled. I have been warming the silicone to 100 F so that the jewelry wax does not cool too quickly.

Has anyone here tried placing their wax filled mold in a vacuum chamber and pull a vacuum while the wax
was still liquid? Also, does anyone know of a suitable material to load up your vacuum chamber with to reduce its volume? I have a pretty big vacuum chamber.

Thanks.

John Gaertner

 

Here is an update on my question. I had trouble removing my pattern from my silicone mold because the undercuts on the patter and mold wall
was not flexible enough to pull the pattern out. Result, the wax pattern tore. I made a second pour of wax after cutting the mold sides way back to
make the mold walls thinner and more flexible. I let the wax and heated mold cool over night so the jewelry wax was cold and as strong as it was
going to be and I cut two relief cuts in the mold, so I could pull the mold open more. Result was that I have a serviceable wax pattern. I refilled
the mold again, after warming it in my oven to 120 F with another bunch of wax this AM. I will let this cool all day and try opening up the mold
and see whether I have a good pattern?

 

What shore is your silicone? If you have undercuts, yq gotta be smart or use a low, floppy silicone.

Your molds look pretty thick and that will limit its flexibility. You might even have to do it in sections. That happens sometimes.

 

Hello Jason, This was Smooth-On Mold Max 30A, so the shore value is 30A. I agree I should have made my mold thinner in diameter. I ended up cutting the mold material back and making two keyed slices along two sides. I started heating the mold up much hotter than at first, 150F internal temperature before filling with wax. This gave me more time to burp the mold of trapped air. Jgaertner

 

There ya go! Heating the new silicone helps a lot! I use a hair dryer or just keep pulling waxes and let the heat do the work. My wax is around 200, almost to the point it's about to start smoking. Good job!