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long draw surface finish
- Thread starter shoobaka1
- Start date
patprimmer
New member
Polysulphone is a particularly hard plastic, so no undercuts should be left on the surface of the mould.
That means no vapour hone unless you have a good draft angle.
It is most important that the polish be in line of draw, as even microscopic undercuts can cause the part to jamb onto the mould.
It is not the tackiness that causes the sticking, but the material conforming to the surface of the mould, then not deflecting nor yielding as the mould is opened, so it is not the surface energy that is important, it is the physical shape, down to microscopic level, hence draw polishing. Nickle plating, whether by electrical or elecroless methods will not help. PTFE coating just might, but it will not be durable. Some ceramic coatings might help, but are not proven.
Dusting or spraying the surface with a mould release can help. These might be zinc stearate powder or silicone oil spray or similar proprietary products. They might introduce surface blemishes on the moulding if over used
Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
That means no vapour hone unless you have a good draft angle.
It is most important that the polish be in line of draw, as even microscopic undercuts can cause the part to jamb onto the mould.
It is not the tackiness that causes the sticking, but the material conforming to the surface of the mould, then not deflecting nor yielding as the mould is opened, so it is not the surface energy that is important, it is the physical shape, down to microscopic level, hence draw polishing. Nickle plating, whether by electrical or elecroless methods will not help. PTFE coating just might, but it will not be durable. Some ceramic coatings might help, but are not proven.
Dusting or spraying the surface with a mould release can help. These might be zinc stearate powder or silicone oil spray or similar proprietary products. They might introduce surface blemishes on the moulding if over used
Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
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