shuliy - Model SL -Plastic granulator equipment

Core preheating is necessary for both insulation extrusion and jacket extrusion. For the insulating layer, especially the thin layer insulation, the existence of the pores cannot be allowed, and the core can completely remove the moisture and oil on the surface by preheating before high temperature. For sheath extrusion, its main function is to dry the core to prevent the possibility of voids in the jacket due to moisture (or moisture surrounding the cushion). Preheating also prevents the internal pressure of the plastic from being quenched during extrusion. In the process of squeezing plastic, preheating can eliminate the disparity temperature difference formed when the cold wire enters the high temperature machine head and contact with the plastic at the die mouth, avoiding the fluctuation of the plastic temperature and causing the fluctuation of the extrusion pressure, thereby stabilizing the extrusion amount and ensuring Extrusion quality. The electric heating core preheating device is used in the extrusion unit, which requires sufficient capacity and ensures rapid heating, so that the core preheating and core drying efficiency are high. The preheating temperature is limited by the speed of the line, and is generally similar to the temperature of the head.

Cooling device

After the formed plastic extrusion layer leaves the machine head, it should be cooled and shaped immediately, otherwise it will be deformed under the action of gravity. The cooling method is usually cooled by water and divided into quenching and slow cooling depending on the water temperature. Quenching is the direct cooling of cold water. Quenching is beneficial to the shaping of plastic extrusion coating. However, for crystalline high polymer, due to rapid cooling, it is easy to residual internal stress in the extrusion layer, resulting in cracks during use. PVC is generally used. The plastic layer is quenched. Slow cooling is to reduce the internal stress of the product. Different temperatures of water are placed in the cooling water tank to gradually cool down the product. The extrusion of PE and PP is carried out by slow cooling, that is, through hot water, warm water and cold water. Three sections of cooling.

Control System

The control system of the plastic granulator includes a heating system, a cooling system and a process parameter measurement system, and is mainly composed of an electric appliance, a meter and an actuator (ie, a control panel and an operation console). Its main function is: control and adjust the drag motor of the main and auxiliary machines, output the speed and power according to the process requirements, and enable the main and auxiliary machines to coordinate work; detect and adjust the temperature, pressure and flow of the plastic in the extruder; Control or automatic control of the entire unit.

The electrical control of the extrusion unit is roughly divided into two parts: transmission control and temperature control, which realizes the control of the extrusion process including temperature, pressure, screw revolution, screw cooling, barrel cooling, product cooling and outer diameter, and traction speed. , neatly arranging the line and ensuring constant tension take-up control from the empty plate to the full plate on the take-up reel.

1. Temperature control of the extruder mainframe

The plastic extrusion of the wire and cable insulation and sheath is based on the deformation characteristics of the thermoplastic, making it in a viscous flow state. In addition to the external heating of the screw and the barrel, it is transferred to the plastic to melt and extrude. It also considers the heat generated by the screw when extruding the plastic. Therefore, the temperature of the main unit should be considered from the whole, considering the heating and opening of the heater. Close, it is necessary to consider the factors of the extrusion heat of the screw to cool, and to have effective cooling facilities. It is required to correctly and reasonably determine the position and installation method of the thermocouple of the measuring component, and accurately reflect the actual temperature of each segment of the host from the reading of the temperature control meter. And the accuracy of the temperature control instrument is required to cooperate with the system, so that the fluctuation stability of the whole host temperature control system reaches the extrusion temperature requirements of various plastics.

2. Pressure control of the extruder

In order to reflect the extrusion of the machine head, it is necessary to check the head pressure during extrusion. Since the domestic extruder does not have a head pressure sensor, it is generally used to measure the thrust of the screw after extrusion, instead of the head pressure measurement, the screw load table (Electrometer or voltmeter) correctly reflects the extrusion pressure. The fluctuation of extrusion pressure is also one of the important factors causing the instability of extrusion quality. The fluctuation of extrusion pressure is closely related to the extrusion temperature, the use of cooling device, and the length of continuous operation time. When an abnormal phenomenon occurs, the rapid elimination that can be eliminated, the reorganization of production must be decisively stopped, not only can avoid the increase of waste, but also prevent accidents. By detecting the pressure gauge reading, it is possible to know the pressure state of the plastic during extrusion, and generally take the back pressure limit value alarm control.