How to control the temperature of parallel twin screw extruder in extrusion process?

Extruder temperature control in the granulation process is a very important process control, temperature control is good or bad directly affects the quality of the product, is especially important for some for temperature sensitive materials. Temperature control generally includes heating and cooling. How do you adjust the temperature in the extrusion process of parallel twin screw extruder?

What are the ways in which the extruder heats up in the extrusion process?

1. Heater heating (external heat) : at present, the extruder USES the motor heating, which is a cleaner, effective and easily controlled heating method. That is, the electric heater (with resistance wire) is packed in the cylinder, and it is heated through the electric heating, which can be used to heat the material and melt it by the combination of heat conduction, convection and radiation.

The heater mica heaters, now in general ceramic heater, cast aluminum heater, cast copper heater, cast iron heater, etc., the effect of all kinds of heater has some differences, mica heater lower cost, easy processing, use fixed number of year is shorter; Ceramic heater, cast iron heater power is larger, warming faster, can rise to more than 300 ℃ or higher, life is relatively short, longer than mica heaters. Cast aluminum heater, casting copper heater because of high thermal efficiency, good thermal insulation performance, long service life and most commonly used.

2. Shear friction heat (internal heat) in extrusion process

A: in the extrusion process, the form of plastic particles is distorted by intense extrusion pressure.

B: the heat generated between the plastic particles and the friction between the particle and the cylinder and the screw;

In extruder extrusion process, the extruder needs to be cooled in order to accurately control the temperature. First, because extruder temperature in the heating process of inertia, in the process of heating up, no matter what kind of heating mode, stop heating, because the temperature rise of inertia, the temperature will continue to rise, at this moment need to watch the control parameters of temperature control instrument, precision, etc. Secondly, because of the heat of shear friction (internal heat) in the extrusion process, the internal heat generated by the extrusion process increases the processing temperature, which damages the properties of the material and causes the material to become a waste product.

In fact, the production of internal heat is not all bad. As long as the temperature is controlled, the heating temperature can be used to provide the temperature needed for processing, not only reducing or reducing the use of electricity, but also energy saving and environmental protection. Note: the extrusion metering section of the parallel twin screw extruder is not required to be heated in the process of production, and it is necessary to cool down properly.

What are the cooling modes in the extrusion process?

A: air natural cooling: the cooling efficiency is low and the temperature is not easy to control

B: air cooling: through the control of the cooling fan's starting, stopping, or control of the cooling air duct valve opening and closing, wind power to cool the cylinder temperature of the section. The cooling rate is slow, and the machine that produces more heat to internal heat is not applicable.

C: soft water (multi-purpose distilled water) cooling: control the opening and closing of the solenoid valve of the cooling water, so that the soft water can remove the heat through the channel of the machine, so as to achieve the purpose of cooling. When the soft water cools, you need to add water to cool the heat. This method is fast and easy to control. But the cooling inertia is large, and the disadvantage is that the temperature control table, solenoid valve and the design of cooling watercourse are higher.

D: thermal oil cooling: the principle is similar to that of soft water, except that the heat conduction medium is different. The cooling and cooling of soft water cooling is more uniform and soft. But the sealing requirement of the pipeline is high, otherwise the oil spill consequence will be more serious.