The structure principle of plastic granulator is described briefly
The structure principle of plastic granulator is described briefly
The main machine of plastic granulator is extruder system, which consists of extrusion system, transmission system and heating cooling system. 1. Extrusion system: extrusion system, including screw, barrel, hopper, the nose, and mould, plastic plastic into homogeneous melt by extrusion system, and established in the process, under pressure by the screw continuous extrusion head.
(1) screw: it is the main component of extruder. It is directly related to the application range and production efficiency of the extruder. It is made of high strength corrosion-resistant alloy steel.
(2) cylinder: it is a metal seamless tube, which is usually made of composite steel tube of alloy steel or lining alloy steel with high heat resistance, high pressure strength, strong abrasion resistance, corrosion resistance. The cylinder and screw are combined to realize the crushing, softening, melting, plasticization, exhaust and compaction of plastic, and continuously and uniformly conveying the adhesive to the molding system. The length of the general cylinder is 18:1 of its diameter, so that the plastic is fully heated and fully plasticided into principle.
(3) hopper: a truncation device is installed at the bottom of the hopper to adjust and cut off the flow of material, and the side of the hopper is equipped with a visual hole and calibration measuring device.
(4) head and mould: the machine head consists of the inner sleeve of alloy steel and the carbon steel jacket, and the molding mould is installed in the head. The function of the machine head is to transform the plastic melt of the rotary movement into parallel linear motion, evenly and smoothly into the mould sleeve, and to give the plastic the necessary molding pressure. Plastic plasticizing compaction in the barrel, is approved by the flow of porous filter plate along a certain head neck into the head forming die, die core die set appropriate coordination, the formation of cross section and decreases the annular space, make the plastic melt around the conductor to form a continuous solid tubular cladding layer. In order to ensure the reasonable plastic flow path in the head of the machine and eliminate the dead Angle of the deposited plastic, there are often shunt plates (sleeve) to be installed to eliminate the pressure fluctuation of the plastic extrusion, and also have the pressure ring. The machine head is also equipped with mould calibration and adjustment device for adjusting and correcting the concentricity of die core and mould sleeve. The extruder is divided into bevel nose (120 degree) and right Angle (90 degree) head, according to the Angle of the head material flow and the center line of the screw. The nose of the shell is bolted on the fuselage, the mold has a mold core inside the head, with a nut fixed in the nose into the line port, the front of the mold core cities with mold core, mold core and mold core of the center hole, used by conductor; All pressure rings are installed in front of the nose for equilibrium pressure. Extrusion molding package part is composed of die sleeve and die set, the location of the die set can be made of bolt support to adjust, to adjust the die set of the relative position of mold core, easy to adjust the uniformity of extrusion cladding thickness. The outside of the nose is equipped with a heating device and a temperature measuring device.
2. Transmission system: the function of the transmission system is to drive the screw, and the torque and rotational speed required by the screw in the extrusion process are usually made up of electric motors, reducers and bearings.
3. Heating and cooling equipment: heating and cooling are necessary conditions for plastic extrusion process. (1) now the extruding machine usually USES electric heating, which is divided into resistance heating and induction heating, and the heating plate is installed in the body, neck and head of the machine. The heating device is heated by external heating cylinder to meet the temperature required for process operation. (2) the cooling device is designed to ensure that the plastic is at the temperature range of the process requirements. Specifically, to exclude the excess heat generated by the shear friction of the screw rotation, to avoid the temperature too high for the plastic decomposition, coke or finalizing difficulties. Cylinder cooling is divided into two types: water cooling and air cooling. Generally, small and medium sized extruding machines are suitable for air cooling, while large ones are mainly cooled by water cooling or two forms. The main purpose of screw cooling is to increase the solid conveying rate of the material, stabilize the volume of the material, and improve the product quality. However, the cooling at the hopper is designed to strengthen the transport of solid materials to prevent the heating of the plastic particles from sticking to the mouth of the material and to ensure the normal operation of the transmission part.
Ii. Auxiliary equipment:
The auxiliary machine of plastic granulation unit mainly includes the setting device, straightening device, preheating device, cooling device, traction device, meter meter, spark tester, wire receiving device. The purpose of the extruder is different from the auxiliary equipment used for the selection
It's not the same. If there are sever, drier, printer, etc. Straightening device: one of the most common types of plastic extruder is eccentricity, and the bending of various types of wire core is one of the important reasons for insulation eccentricity. In the case of sheath extrusion, the scratches on the sheath surface are often caused by the bending of the cable core. Therefore, the straightening device of all kinds of extruder is indispensable. The main types of straightening devices are: roller type (divided into horizontal and vertical); Sliding wheel (divided into single pulley and pulley block); The twisting wheel is a combination of dragging, straightening and stabilizing tension. Wheel type (divided into horizontal and vertical), etc. Preheating device: the cable core preheating is necessary for insulation extrusion and sheath extrusion.
For insulation layer, especially thin layer insulation, can not allow the existence of stoma, the core of the core before squeezing the bag through high temperature preheat can thoroughly clean the surface water, oil. For sheath extruding, its main function is to dry the cable core and prevent the possibility of air hole in the sheath due to moisture (or the moisture of the blanket). Preheating can also prevent the pressure of the plastic from quenching. In the process of extrusion plastic, preheating can eliminate cold line into the nose by high temperature, in gate in contact with the plastic forming of wide temperature difference, avoid plastic temperature fluctuations caused by extrusion pressure fluctuations, thus stable extrusion quantity, ensure the quality of extrusion. It is required to have sufficient capacity and ensure fast heating, so as to make the core preheating and the cable core drying efficiently. The preheating temperature is restricted by the speed of the line, which is generally similar to the temperature of the nose.
Cooling device:
The moulded plastic extruded layer should be cooled and shaped immediately after leaving the machine, otherwise it will be deformed under the influence of gravity. The cooling method is usually water cooled, and is divided into cold and cold, depending on the water temperature. Quenching is cold water cooling, direct quenching is good for plastic extrusion cladding to finalize the design, but for crystal polymer, because of the sudden heat cooling, easy in extrusion cladding organization internal residual stress, leading to cracks in the course of using, general PVC plastic layer by rapid cooling. Slow cooling is to reduce the internal stress of products, block placed different temperature of the water in the cooling water tank, cooling the products gradually to finalize the design, extrusion of PE, PP, with a slow cooling which three sections of cooling after hot water, warm water, cold water.
Iii. Control system:
The control system of plastic granulator includes heating system, cooling system and process parameter measuring system, mainly composed of electrical apparatus, instrument and actuator (i.e., control screen and operation table). The main function is to control and adjust the motor of the main auxiliary machine, output the speed and power of the process, and can coordinate the work of the main auxiliary machine; Check and adjust the temperature, pressure and flow of plastic in extruder. Achieve control or automatic control of the entire unit. Extrusion unit electrical control is roughly divided into drive control and temperature control of two parts, realize the extrusion process including temperature, pressure, screw revolution, cooling, cooling, machine barrel screw products control, cooling and diameter and drawing speed, neat row line and ensure the line plate from the line in empty plate to a plateful of constant tension control.
1. Temperature control of extruder main machine:
The plastic extrusion of wire and cable insulation and sheath is based on the deformation characteristics of thermoplastic plastic. Except for screw and barrel external heating, to the plastic melt extrusion, but also the screw extrusion plastic itself fever, temperature requirements of the host should consider from overall, therefore, should not only consider the heater heating on and off, and to consider the screw of the factors of cooling the heat, to be effective cooling facilities. The location and installation method of the thermocouple of the measuring element are required to be properly and reasonably determined. The actual temperature of the main part of the host can be accurately reflected from the temperature meter reading. As well as the accuracy of the temperature control instrument and the system, the fluctuation stability of the whole host temperature control system can meet the requirements of the extrusion temperature of all kinds of plastics.
2. Pressure control of extruder:
In order to reflect the extrusion of the nose, need to detect the head pressure of extrusion, because domestic squeeze molding machine head no pressure sensor, is generally after the screw extrusion force of alternative head pressure measurement, screw load table (ammeter or a voltmeter) can correctly reflect the size of the extrusion pressure. The fluctuation of extrusion pressure is also one of the important factors that causes the extrusion quality instability, the fluctuation of extrusion pressure and the use of extrusion temperature, cooling device and continuous running time
Factors such as length are closely related. When abnormal phenomenon occurs, it can be eliminated quickly, and the production should be reorganized with a decisive stop, which not only can avoid the increase of waste, but also prevent the occurrence of accidents. By detecting the pressure gauge reading, you can know the pressure state of the plastic in the extrusion, and generally take the pressure limit alarm control.
3. Control of screw rotation speed:
The adjustment and stability of screw rotation speed is one of the important process requirements of the main drive. The screw rotation speed directly decide the quantity of glue and the speed, the normal production always wanted to achieve the highest rotational speed and achieve high yield as much as possible, the screw rotation speed to squeeze molding machine requirement from starting work to the required speed, speed range that can be used. And demand is high, to the stability of the speed because the rotation speed fluctuations will lead to the fluctuation of impact extrusion quality, so in the case of traction linear speed did not change, can cause the change of the cable diameter. Large fluctuations in the same way as traction device wire speed can cause the change of the cable diameter, screw and traction linear velocity can be reflected on the corresponding instrument, should be closely observed when it is squeezed, ensure good quality and high yield.
4. Control of outside diameter:
As mentioned above in order to guarantee the products size of cable diameter, in addition to the required control line core (core) size tolerance, the extrusion temperature, screw speed and traction device linear velocity should be controlled to ensure, and outer diameter measuring control comprehensively reflect the control precision and level. In crowded molding machine group equipment, high speed extrusion production line, in particular, should be with online diameter detector, at any time to test the cable outer diameter, and the error signal feedback to adjust traction or screw speed, out-of-tolerance correct diameter.
5. Tension control of the rewinding requirement:
In order to ensure that under the different wire speed take-up, from empty to plateful job requires constant tension and hope to receive wiring device have storage line tension adjustment mechanism, or consider constant linear velocity and constant tension on electric system of winding and so on.
6. Electrical automation control of the whole machine:
This is the process control requirement to realize the high speed extrusion line. Work pressure protection and interlock; The ratio of extrusion and traction of two parts is synchronized. Synchronous control of receiving line and traction; External diameter online detection and feedback control; The control of the unit and the whole tracking of the components according to various requirements.
