Vacuforming: What Is the Max Size
Hey There Stan Winston School of Character arts! I'm now in the process of constructing a vacuforming machine. Before I start trying to cast random stuff, I just wanted to know how big a casts I can make. I know that the limiting factor on the x-axis (length) and the y-axis (Width) is the length and width of your machine's vacuum table and frame, but I don't really how big casts can be on the z-axis (height). Does anybody know how high a cast I can make with vacuforming?
Thicker plastics will require more heat, so you are limited by how much your heating elements can produce. Thicker plastic will also smooth out and reduce details.
One general rule followed in vacuum forming is you want your heated plastic to slump down (sag) about the height of the buck you are pulling over before you make the pull. So your Z axis needs to be a little more than twice the height your buck.
The width and length of the plastic sheet you are using also factors in, as the plastic can only stretch so far before tearing. For taller pulls you need a larger sheet/machine.
There's no general limit for how tall a buck can be, as it all depends on the shape/detail/volume of the buck and the size and thickness of your plastic.
You could try coating the sculpt in a few layers of spray paint to protect it a bit, and freezing it so it would take longer to heat up to the melting point. That would give the plastic time to cool and stiffen before the clay deforms too much. But even then you may run into problems.
I would test it a few times with a simple test sculpt. But generally you want to form over rigid bucks that will not be damaged by heat.
Making a mold of your sculpt and then casting up a buck in plaster is a common technique. Plaster is great for vacuum forming over as it is nice and rigid.
You can also carve/sculpt your bucks out of rigid foam (like renshape), or MDF wood.