英语翻译Problem:Poor FinishWhen molding Renprene TPVs and our ot

英语翻译
Problem:Poor Finish
When molding Renprene TPVs and our other TPE products,pressures in the
mold work to increase the contact between the shot material and the mold surface.Generally,high injection pressures maintain part properties,improve part appear- ance and reduce molding cycle times.When the melt flow pressures do not allow for the material to pack out evenly against the mold cavity,poor surface finish
can result.
Mold Fill Is Too Slow
The majority of our TPVs are shear dependent.They require fast mold filling via high injection speeds and pressure to increase shear through the system,which reduces their viscosity.If increasing injection pressure and injection speed does not rem-
edy a poor finish,increasing the melt temperature and mold temperature will also improve surface appearance when molding our materials.
Mold Function Is Incorrect
First make sure that venting and gate size are not reducing the melt flow speed.Vents that are too small can lead to trapped air in the mold cavity,which can slow melt flow into the cavity.We do not recommend using mold releases or lubricants.Over time,the lubricants may actually cause the parts to stick in the mold due to build up and vent clogging.Be sure that the mold surface is clean.Avoid thick ribs and bosses that will create sink marks on the opposite side of the part.
Problem:Poor Surface Detail
The leading causes of surface detail problems on parts molded from Santoprene TPVs are improper filling and packing conditions.Pressures in the mold work to increase the contact between the shot material and the mold surface.Generally,high injection pressures maintain part properties,improve part appearance,and reduce molding cycle times.A reduction of pressure in the mold cavity can be caused by the gate freezing off prematurely,poor mold design,or low pack/
hold pressures.Verify that the set up conditions are correct using the Start Up
Procedures.
Mold Filling Improperly
If material is not filling surface details on the part,there may not be enough pres- sure or material to fill the part.First check that the shot size is correct.If the shot size is correct,try increasing the injection speed and back pressure.This will help ensure there is enough pressure in the mold to encourage contact between the melt flow and the mold surface.
Packing Conditions Are Improper
Under-packing of the mold cavity can lead to excessive shrinkage,shrink voids in thicker wall sections,sinks in large surface areas,and poor part appearance.Traditionally,mold fill time takes between 0.5 and 2 seconds,depending on
part volume,runner-gate style and size,cavity locations,and injection pressure.Increasing the second stage pressure and time will also help to maintain pressures in the mold necessary for good surface finish.
Polymer Cooling Rate Is Too High
Increasing mold temperatures will help by reducing the cooling rate of the melt and encouraging filling of surface details.