How is the mold temperature controlled?
The temperature of the mould directly influences the melt flow, pressure drop and temperature, and the improper control can cause the extrusion products to increase the internal stress, the flow mark is serious, and the thickness is not equal.Different kinds of plastic performance and molding process, mold temperature is not the same.Mold temperature control must meet the following requirements.
Ensure that the temperature of each part of the runner is as consistent as possible.
The heating time should be short.
It has a good temperature control system.
The extruded mold is only heated and not cooled, and the heater is used, mainly the belt heater, tube (rod) type heater and plate (cast aluminum) type heater, heating work.
The rate is 2 ~ 3W/cm2.The belt heater is generally used in the mould with symmetrical shape;The plate heater is mainly used in the shape of the square (moment) mold;Belt type peace plate type heater is installed in the mold on the surface, away from the melt flow channel, and heating time is long, the heat loss is bigger, especially heating film, piece mold width of several heating zone, the temperature difference is bigger.So flat membrane, piece mold usually adopt tube (bar) heater, die bodies on the uniform distribution of an odd number of hole is drilled, the pitch is about 200 ~ 330 mm, tube heater is installed on the hole, and ensure the installation precision.This kind of heating method, heating source and melt runner is relatively close, heating efficiency is high.For the die inside the annular cavity mold, several heating zones are usually set up to control the temperature respectively, where the mouth mold segment is a separate heating zone.