vac/press?

[jharvey1309]

Ok I have to ask this question as I want to build a pressure/vacuum pot. When is pressure used in the making of PR blanks and when is vacuum used? If I was making a coffee bean cast would I use pressure or vacuum? I guess I don't know what each of them are supposed to do. Any insight would be helpful

Jonathan

 

[sbell111]

Different people use different methods. I would only use pressure when casting something like beans.

I basically only use vacuum when stabilizing a blank. The vacuum helps evacuate much of the air from the inside of the blank. I then switch to pressure to force as much goop into the blank as I can.

 

[jharvey1309]

Different people use different methods. I would only use pressure when casting something like beans.

I basically only use vacuum when stabilizing a blank. The vacuum helps evacuate much of the air from the inside of the blank. I then switch to pressure to force as much goop into the blank as I can.

I have a question in regards to adding pressure then. How does adding pressure into the tank (essentially more air) remove air bubbles from the poured molds?

 

[sbell111]

Basically, air changes size depending on pressure. You can see this affect by blowing up a balloon and then sticking it in the freezer. It will shrink. You bring it out of the cold and let it warm and it will increase in size.

Therefore, If I'm stabilizing something, I first put it under vacuum to get as much air as possible inside the blank to expand in size and bubble out.

Increasing pressure reduces the size of air bubbles. The plan is to increase the pressure enough that any remaining air bubbles are reduced to the point at which they are unnoticible. If the pressure change causes any bubbles to float out, that's good too.

 

[jharvey1309]

Thanks I appreciate your help.