注塑模具venting(參考版)
2024-08-12 16:51本頁面
【正文】 Registered trademark of DuPont Efficient Venting Page 2 What’s a vent? ? gap ? big enough to let the air out ? small enough to keep the plastic in ? some polymers are viscous, they can have deeper vents ? nylons have very low viscosity, they must have shallower vents ? this makes it more difficult to effectively vent tools designed for moulding nylon, especially when using the very fast injection fill times that are needed for nylons with high levels of glass fibre reinforcement ? HTN53G50 has 50% by weight glass fibre reinforcement Efficient Venting Page 3 Why vent injection moulds? ? cavity (and any cold runner) is full of air at 1 bar ? most diesel engines work by pressing air to about 22 bar ? cavity pressures in phone moulding can go up to 3000 bar ? fast fill speed gives best surface finish (resinrich surface) ? fast fill speed gives stronger weld lines ? fast fill speed gives more equal pressure transfer through cavity ? can’t sell parts with burn marks or poor surface finish ? moulder doesn’t want to ruin the tool by burning away steel Efficient Venting Page 4 What blocks vents? ? carbonised polymer from diesel effect ? flash ? additives/pigments/volatiles in the material ? degraded material (molecular weight reduced during moulding) ? incorrect machine startup procedures ? incorrect hot runner start up procedures ? low viscosity material, especially wet nylon Efficient Venting Page 5 What venting methods are there? ? apply a vacuum to the cavity before injection fill ? make the tool (or parts of it) from porous metal ? recognise that venting is a priority at the tool design stage ? then put the maximum venting into the tool Efficient Venting Page 6 Vacuum venting: ? most efficient method, no air left to press and burn ? needs very careful too
環(huán)評公示相關推薦
鄂ICP備17016276號-1