Extruder can be divided into continuous extruder and discontinuous extruder according to the action type. Plastic extruder is also a kind of plastic machinery. The extruder divides the head into bevel head (included Angle 120o) and right Angle head according to the included Angle between the flow direction of the head and the center line of the screw. The shell of the nose is fixed on the fuselage with bolts. The mould inside the nose has a die core seat and is fixed on the inlet port of the nose with nuts. The front of the die core seat is provided with a die core. The auxiliary machines of the plastic extruder mainly include setting device, straightening device, preheating device, cooling device, traction device, meter counter, spark testing machine and rewinding device. The extruder unit USES different auxiliary equipment, such as cutting device, drying device, printing device, etc.
An extruder usually consists of a main machine (extruder), an auxiliary machine and its control system. Usually these components are collectively referred to as extruder units.
1) the host
The main machine of an extruder consists of three parts: extrusion, transmission, heating and cooling. The extrusion system is mainly composed of screw and barrel, which is the key part of the extruder. The function of the driving system is to drive the screw, to ensure that the screw in the process of work with the required torque and speed; The heating and cooling system is mainly used to ensure the temperature control of the material and extrusion system in the forming process.
The composition of auxiliary extruding equipment depends on the type of products. Generally speaking, the auxiliary machine by the agent through the finalizing device, cooling device, traction device, cutting device and products of the winding or stacking device and other parts.
3) control system
The control system of the extruder is mainly composed of electric appliances, instruments and actuators, whose main functions are as follows:
* control the driving motors of the main and auxiliary engines to meet the speed and power required by the process requirements, and ensure the coordinated operation of the main and auxiliary engines.
* control the temperature, pressure, flow and quality of main and auxiliary machines.
* realize the automatic control of the whole unit.
1) traditional driving methods:
The traditional extruder is driven by dc motor. However, the dc motor needs to be replaced regularly. The resistance of the dc motor to harsh environment is also poor. Sometimes it needs independent and clean cooling air. Typical fault phenomena of dc motor in daily use are brush ignition, armature discoloration, insufficient heat dissipation, violent noise and vibration. Therefore, the daily maintenance cost of dc motor is much higher than that of ac motor, and the cost of dc motor is higher than that of ac motor.
2) ac driven approach
Only a few years ago, ac drivers did not offer the same performance as dc drivers and were expensive. However, with the rapid development of power electronic devices and microprocessor technology in recent years, the proposal of ac control theory and the concrete improvement of actual ac control software, ac drive technology has been more cost-effective than dc drive in many application fields. At present, the AM300 series inverter has better speed control performance and torque response speed than dc drive in extruders. The accuracy of open-loop vector control is better than 0.5%, and the accuracy of closed-loop speed control is better than 0.1%.
Extruder starting torque may reach 200% - 250% of operating torque, 180% AM300 series frequency converter of high starting torque value, so you need to choose a larger inverter, but also can make the equipment working in ac motor rated speed constant power region method resolved, because of the extruder at full speed when the load torque does not need the rated torque of the motor. If the reduction ratio is appropriately selected, and the motor's general working speed is 70Hz, then the load torque is T load, the rated torque of the motor is calculated theoretically: T motor rating = 1.4t load
T = 1.8t motor rated = 252%T load meets the starting torque requirements of the extruder. Otherwise, if the traditional selection method is still followed, the motor shall be selected with the general working speed of 50Hz. In order to meet the requirement of 250% starting torque, the motor and driver with the power of 1.4 times must be selected.
Advantages of AMB300 inverter in extruder application:
AMB300 inverter built-in PID feedback, built - in closed - loop magnetic field oriented magnetic flux vector control function. Through the unique static motor adaptation, the electrical parameters of various motors can be measured. AMB300's built-in motor model and current detection are very special, the current is decoupled into torque current and excitation current, vector control theory is advanced, the system has strong computing power, so it can quickly detect, control and compensate load torque.
Advantages of the system after using inverter:
1) improve efficiency
AMB300 frequency conversion drive system is about 5% higher than the dc drive system with the same power, the efficiency of the ac motor is also higher than the dc motor, AMB300 inverter ensures excellent motor output performance and will not occur overheating. In general, the power consumption of extruders in factories takes up a large proportion of the total energy consumption. AMB300 inverter has a much smaller input harmonic current than dc driver and other general purpose inverters, ensuring that the total input power factor is greater than 0.9, so there is no need to enlarge the capacity of power transformers and cables in factories.
2) improve the protection level
Extruders usually work in harsh, high temperature or corrosive gas environment, ac motor protection level is higher, while dc motor protection level is lower, for harsh environment maintenance cost will be greatly increased.
AMB300 inverter for extruder has the following advantages:
* fast processor provides higher frequency response: AMB300 inverter built-in processor provides high control accuracy, fast response frequency and good dynamic performance. The process requirements of the extruder are mainly to control the pressure of the outlet constant, the equipment at the beginning of the work, speed control, when the demand for pressure, to switch to pressure control. The switching process should be shock-free and require high control accuracy of the converter to receive pressure signals.
* automatic energy-saving control to optimize the motor efficiency: the main drive motor of the extruder mainly drives the screw to rotate after decelerating through the parallel shaft helical gear reducer, and the speed is adjusted by constant torque when the operating speed is changed below the fundamental frequency. AMB300 series inverter with automatic energy saving control function, can automatically adjust the voltage according to the load, so that the motor runs in the efficiency state
* torque limitation and torque compensation: the torque limitation and torque compensation functions make the output torque constant and the torque fluctuation small, meeting the product process requirements
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