The principle of a plastic extruder is that solid plastic melts and plasticizes under the conditions of heating and the rotation pressure of the extruder screw, and continuous plastic products with the same cross-sectional shape as the die are produced through a die of a specific shape. The drive of the extruder used to be mostly DC drive or electromagnetic speed control. The former has complicated maintenance and huge costs, which affect the efficiency of equipment use, while the latter has low speed control accuracy and low product grade, which greatly affect the development of the extruder.
Due to the rapid development of AC variable frequency technology in our country in recent years, and frequency conversion speed regulation is incomparable in terms of frequency range, dynamic response, speed control accuracy, low frequency torque, speed difference compensation, communication function, intelligent control, power factor, work efficiency and convenience of use, it is highly favored by extruder manufacturers. In new extruder machinery, especially plastic machinery, high-performance inverters have been adopted, and existing old extruder equipment will also enter a new round of transformation.
The plastic extruder is a production equipment widely used in the plastic processing industry. It is mainly used to process plastic into products of different shapes and sizes by extruding and stretching through a series of extruder heads and molds. The main components of the plastic extruder include the feeding system, plasticizing system, extrusion system, cooling system, cutting system, and control system, etc.
(1)Feeding System
The feeding system of the plastic extruder mainly consists of the feeding drive mechanism, feeding hopper, metering pump, and feeder. Its main function is to deliver the raw plastic material into the plasticizing system for processing.
(2)Plasticizing System
The plasticizing system of the plastic extruder mainly consists of the screw, barrel, heating elements, pressure sensors, and other components. Its main function is to heat, melt, and mix the plastic raw materials, forming a soft plastic melt that provides a uniform and stable supply of material to the subsequent extrusion system.
(3)Extrusion System
The extrusion system of the plastic extruder mainly consists of the extruder head, mold, and frequency converter. Its main function is to uniformly extrude the plastic melt formed by the plasticizing system into the mold, shaping it into the desired shape and size
(4)Cooling System
The cooling system of the plastic extruder mainly consists of the water tank, water circulation pump, water pipelines, and nozzles. Its primary function is to cool the plastic products during the extrusion process, enabling them to solidify quickly and achieve the desired shape and size.
(5)Cutting System
The cutting system of the plastic extruder mainly consists of the cutter and conveyor belt. Its primary function is to cut the extruded plastic products into the required length and transport them to the subsequent unloading and packaging processes.
(6)Control System
The control system of the plastic extruder mainly includes electrical components, computers, PLCs (Programmable Logic Controllers), and control software. Its primary function is to control, monitor, adjust, and optimize various parts of the extrusion production line, ensuring smooth and efficient operation throughout the process.
The structure of the screw extruder is shown in the figure below. After the plastic granules are fed from the hopper, they are heated and plasticized, and then pushed to the outlet of the extruder by the rotation of the screw. The final product shape is determined by the basic die head. The typical screw speed of a common single screw extruder is about 100r/min, while that of a twin-screw extruder for mixing is 200r/min~500r/min. The speed of a low-speed twin-screw extruder used for profile extrusion is usually 10r/min~40r/min.
The FRECON FR500A series inverter 55KW is used for drive on site. The main control part adopts analog input for speed regulation, and the external control button for startup. The FRECON FR500A series inverter has the following unique advantages: open-loop vector control, achieving high precision and high torque, with multiple protection measures. The torque response time is extremely short, and it has an automatic torque boost function at low speed; software and hardware filtering processing effectively improves system reliability. It significantly reduces noise interference and prevents electromagnetic interference with other equipment from causing misoperation.
①The inverter cannot operate if the temperature of the heating device has not reached the set temperature
②An interlock circuit must be formed through an external circuit
③The inverter cannot start before the hydraulic pump starts
④When equipment malfunctions, the inverter must stop operating
