How does the control system of a plastic granulator operate?

The control system of a plastic granulator includes a heating system, cooling system, and process parameter measurement system, which mainly consists of electrical appliances, instruments, and actuators, i.e. control panel and operation desk. The electrical control of the extrusion unit is roughly divided into two major parts: transmission control and temperature control, to achieve the extrusion process including temperature, pressure, screw rotation, screw cooling, barrel cooling, product cooling, and outside diameter control, as well as traction speed, neat line up and ensure that the take-up tray on the constant tension take-up control from an empty tray to a full tray.

The following is a list of contents

Temperature control of extruder main machine

Extruder pressure control

Screw speed control

Control of outer diameter

Tension control for winding requirements

Electrical automation control of the whole machine

Temperature control of extruder main machine

Plastic extrusion for wire and cable insulation and sheathing is performed in a viscous flow state based on the deformation characteristics of the thermoplastic. In addition to the external heating of the screw and barrel, which is transmitted to the plastic to melt and extrude, the heat generated by the screw itself when extruding plastic is also taken into consideration, so the temperature of the main machine should be considered as a whole, considering both the heating of the heater on and off, and the overflow of heat from the extrusion of the screw to be cooled, and there should be effective cooling facilities. And require a correct and reasonable determination of the location of the measuring element thermocouple and installation method, which can be read from the temperature control instrument and accurately reflect the actual temperature of each section of the host. As well as the requirement that the accuracy of the temperature control meter and the system with good cooperate, so that the stability of the fluctuations of the entire host temperature control system achieves the requirements of the extrusion temperature of various plastics.

Extruder pressure control

In order to reflect the extrusion of the head, it is necessary to detect the head pressure during extrusion. Generally, the measurement of the thrust after the extrusion of the screw replaces the measurement of the head pressure. The screw load meter (ammeter or voltmeter) can correctly reflect the size of the extrusion pressure. The fluctuation of extrusion pressure is also one of the important factors that cause unstable extrusion quality. The fluctuation of extrusion pressure is closely related to the extrusion temperature, the use of cooling devices, the length of the continuous operation time, and other factors. When an abnormal phenomenon occurs, can exclude quickly, must re-organize the production should be decisive stop, not only can avoid the increase of scrap, more can prevent the occurrence of accidents. Through the detection of the pressure gauge readings, you can know the pressure state of the plastic in the extrusion, generally taken after the thrust limit value alarm control.

Screw speed control

The adjustment and stability of the screw speed are one of the important process requirements of the host drive. Screw speed directly determines the amount of rubber and extrusion speed, normal production always wants to achieve the highest possible speed and achieve high production, the extruder requires screw speed from the start to the required working speed, the available speed range to be large. And high requirements for speed stability, because fluctuations in speed will lead to fluctuations in the amount of extrusion, affecting the quality of extrusion, so there is no change in the traction line speed, it will cause changes in the outside diameter of the cable. Similarly, such as traction device line speed fluctuations will also cause changes in the outer diameter of the cable, the screw and traction line speed can be reflected by the corresponding instrumentation on the operating table, extrusion should be closely observed to ensure high quality and high yield.

Control of outer diameter

As mentioned above in order to ensure the size of the outside diameter of the product cable, in addition to the requirements of the control core (cable core) size tolerance, extrusion temperature, screw speed, traction device line speed, etc. should be controlled to ensure that the measurement and control of the outside diameter is a comprehensive reflection of the above control accuracy and level. In the extrusion unit equipment, especially high-speed extrusion lines should be equipped with an online outside diameter detector, at any time to detect the cable outside diameter, and will exceed the signal feedback to adjust the traction or screw speed, to correct the outside diameter exceeding the difference.

Tension control for winding requirements

In order to ensure the winding of different wire speeds, from empty tray to full tray work of constant tension requirements, hope that the winding device has storage wire tension adjustment mechanism, or in electrical consideration of constant wire-speed system and constant tension system of winding, etc.

Electrical automation control of the whole machine

This is to realize the process control requirements of a high-speed extrusion line, mainly: start-up temperature interlock; working pressure protection and interlock; extrusion, traction of the two major parts of the drive proportional synchronous control; winding and traction of synchronous control; outside diameter online detection and feedback control; according to the various needs of the components of the single machine and the whole machine tracking control.

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