air entrapment in poly-resin casts-[small rubber molds]
air entrapment in poly-resin casts-[small rubber molds]
(OP)
einzats
Hi, my problem is a old one that hasn't been effectively solved in an economically sound way. I am casting small resin parts {urathane,epoxy etc.] in small rubber molds. They are designed with efficient vent systems etc. I have used vibration casting, vacuum casting, pressure, rotational and centrifuge. I still get the occational pin-hole. I want to eliminate this problem completely--and efficiently ie. fast and cheap. Any suggestions?
Hi, my problem is a old one that hasn't been effectively solved in an economically sound way. I am casting small resin parts {urathane,epoxy etc.] in small rubber molds. They are designed with efficient vent systems etc. I have used vibration casting, vacuum casting, pressure, rotational and centrifuge. I still get the occational pin-hole. I want to eliminate this problem completely--and efficiently ie. fast and cheap. Any suggestions?






RE: air entrapment in poly-resin casts-[small rubber molds]
Regards
pat
RE: air entrapment in poly-resin casts-[small rubber molds]
RE: air entrapment in poly-resin casts-[small rubber molds]
What do you think? So far I thick your on to something using a gass. Please return your opinion, it is appreciated---thanks--- einzats
RE: air entrapment in poly-resin casts-[small rubber molds]
The syringe methad sounds good, as you get some mixing with no gass present
Regards
pat
RE: air entrapment in poly-resin casts-[small rubber molds]
What do you think?
Thanks, einzats
RE: air entrapment in poly-resin casts-[small rubber molds]
I still se no function from the presence of a gas other than air, unless you have one of the following issues
Moisture from the air creates problems.
Oxygen in the air causes oxidation of the parts.
The air is entrapped in the mould.
Exotherm is boiling a component in your resin, causing outgassing. Some of this gas is then trapped.
If moisture is the problem, simply dry the air
If oxidation is the problem, use nitrogen
If air entrapment is an issue, there are 4 possible solutions
Evacuate the mould
Fill slowly
Fill from the bottom
Use a gas that disolves in your resin. (I don't know anything about this in practice).
If exotherm is the problem, control the initial temp, and heat added or removed dureing the reaction. Also, try a partly reacted resin. This certainly works for acrylic.
If you are moulding powders, use a compression moulding technique rather than a casting technique
Regards
pat
RE: air entrapment in poly-resin casts-[small rubber molds]
Regards
pat
RE: air entrapment in poly-resin casts-[small rubber molds]
Thanks for your input,
einzats