Master mold material compatible for styrene

[soujoe7]

Hi I'm sorta new here and I couldn't find any info on this so I apologize in advanced if this thread already exists! However I was wondering if anyone has any suggestions on what would be good material to use to make a master mold out of for styrene vacuum forming? I've heard of wood and molding clay but I was curious if there were other ways as well? :confused

 

[BornKilr]

Those will work.
Hydrocal plaster also works very well. A lot of professional vacu-formers use metal bucks. I believe, mostly aluminum. I've used the actual object, in the case of an M1 helmet that worked OK.

 

[laellee]

You can use plaster, ceramics, metal, wood, just about anything that can take the momentary temperature exposure of the heated styrene.

Just to note, if you use regular old modeling clay, your styrene is going to melt into the surface of the material, and it'll be just about impossible to separate it from your mold (it sucks). The easiest way around that is to first vacuum form a thin sheet of styrene over the clay, letting it become a jacket over your original buck. After it cools, trim off your excess, but don't mess with it otherwise. I can't explain the science, but vacuum-formed styrene won't adhere to the styrene outer skin, so that thin jacket ends up working as a mold release. By all means experiment first if you are using a polystyrene variation, but it's worked for me well in the past.

 

[Knowone251]

I have used plaster of Paris, durham's rock hard water putty, MDF and other woods, epoxy hardened cardboard, & bondo backed with fiberglass and expanding foam. I have had one buck made with the bondo warp though, so it's probably not the best option.

 

[soujoe7]

Those will work.
Hydrocal plaster also works very well. A lot of professional vacu-formers use metal bucks. I believe, mostly aluminum. I've used the actual object, in the case of an M1 helmet that worked OK.

I wouldn't know how to make a buck out of metal for what I am working on currently but that is definitely something I am going to keep in mind for future projects! They would probably last alot longer as well. Thank you!

- - - Updated - - -

You can use plaster, ceramics, metal, wood, just about anything that can take the momentary temperature exposure of the heated styrene.

Just to note, if you use regular old modeling clay, your styrene is going to melt into the surface of the material, and it'll be just about impossible to separate it from your mold (it sucks). The easiest way around that is to first vacuum form a thin sheet of styrene over the clay, letting it become a jacket over your original buck. After it cools, trim off your excess, but don't mess with it otherwise. I can't explain the science, but vacuum-formed styrene won't adhere to the styrene outer skin, so that thin jacket ends up working as a mold release. By all means experiment first if you are using a polystyrene variation, but it's worked for me well in the past.

Ah thank you for this warning! I am actually using air-dry clay that was given to me by a friend. From what you state here I can imagine that the styrene will indeed stick to the clay. Thanks for the heads up. Would a thin layer of bondo help prevent that?

- - - Updated - - -

I have used plaster of Paris, durham's rock hard water putty, MDF and other woods, epoxy hardened cardboard, & bondo backed with fiberglass and expanding foam. I have had one buck made with the bondo warp though, so it's probably not the best option.

Would you say Bondo isn't recommended for using with a buck for styrene? Definitely wouldn't want it to warp. What would you suggest was the best plaster/clay you have used? And thank you!

 

[Knowone251]

I think the bondo was too thin, and it was not backed with fiberglass or any kind of reinforcement on that specific buck. I would experiment with some smaller pieces if you are going to use bondo. I have 2 other bucks made with bondo that have been fine. But the best bucks I have used were made from wood, honestly.

 

[soujoe7]

I have been making one small buck out of wood for one part. But I'm not sure if I have the skill to make a armored chestplate buck out of wood. I would love to though. If I had to use a clay based material to make a large sized buck is there a specific kind I should use that could withstand the styrene vacuum forming? Also Thank you guys so much! You have been alot of help with your advice/guidance. I truly appreciate it.