Shrinkage is due to volume shrinkage, the wall thickness of the surface material is pulled in, because, on the surface of the finished products appear dent marks.Shrinkage is the most undesirable phenomenon on the surface of finished products, most of which occur at the wall thickness.1. When the mold is designed, it is necessary to consider the removal of unnecessary thickness, generally must be as far as possible to make the wall thickness of the formed product uniform;2. If the molding temperature is too high, shrinkage is likely to occur on the wall thickness, rib or convex side. This is because the place where it is easy to cool is solidified first.3. Generally reduce the molding temperature, mold temperature to reduce the shrinkage of raw materials, but will increase the pressure.
Molding machine injection time is short (GATE is not solidified, the pressure will be over) guarantee low pressure measurement insufficient pressure position conversion too fast injection pressure low injection speed slow cooling time short raw material temperature high reverse valve damage nozzle aperture deformation (pressure loss) or overflow
Mold temperature high mold cooling is not uniform (mold part high) GATE small mold structure design thimble improper raw material material shrinkage rate is large not easy to take off the mold (protruding) when the mold opened the finished product attached to the moving mold to take off the mold, when the jacking, the jacking broken or protruding finished product.If the mold is not good, it will stick to the static mold.1. Poor exhaust discharge of the mold or no exhaust groove (the location of the exhaust groove is not right or the depth is not enough), resulting in unsmooth demoulding;2. If the injection pressure is too high, the deformation will be large and the shrinkage will be uneven.3. Adjust the mold temperature, to prevent demoulding is not effective, make the molding product after cooling shrinkage, in order to demoulding, but, if the shrinkage is too much, it is not easy to demoulding on the moving mold, so, must maintain the best die temperature.Generally, the temperature of the dynamic mold is about 5 ℃ - 10 ℃ higher than that of the static mold, depending on the actual situation.4. If the alignment between the center of the pouring nozzle and the rubber mouth is not correct, the hole deviation or the hole diameter of the pouring nozzle is larger than the hole diameter of the rubber channel will cause unsmooth demission.
Molding machine material temperature high injection pressure high injection time long pressure holding time long cooling time short pressure holding high
Mold mold release Angle is not enough mold temperature is high mold exhaust bad mold cooling uneven nozzle hole diameter is greater than the hole hole hole hole hole hole hole hole hole hole hole migration raw material material fluidity is insufficient raw material shrinkage rate is small
Cold glue shrinkage can see whether the temperature in the film is too low mold opening time cycle is too fast chiller temperature..Lack of material molding plastic film out of incomplete mainly pay attention to whether there is a foreign body in the mold to block the injection machine is to melt the material all the total injection volume is in place whether the film is too fast whether the temperature in the mold is too low.