Outflow time of plastics produced by extruder

Extruder Extruders can be divided into continuous extrusion and discontinuous extrusion according to the type of action.

Extruder 1. Composition of plastic extruder:

The main engine of plastic extruder is extruder, which consists of extrusion system, transmission system and heating and cooling system.

1. Extrusion system The extrusion system includes screw, barrel, hopper, die and die head. Plastic is plasticized into a uniform melt by an extrusion system, and is continuously extruded by a screw under the pressure established in the process.

Screw (1): It is the most important part of the extruder, which is directly related to the application scope and productivity of the extruder. It is made of high-strength corrosion-resistant alloy steel.

(2) Machine barrel: it is a metal cylinder, generally made of alloy steel with high heat resistance, high compressive strength, strong wear resistance and corrosion resistance or composite steel pipe lined with alloy steel. The barrel cooperates with the screw to crush, soften, melt, plasticize, exhaust and compact the plastic, and continuously and evenly convey the rubber to the molding system. Generally, the length of a barrel is 15 ~ 30 times of its diameter, and the principle is to fully heat the plasticized plastic.

(3) Hopper: The bottom of the hopper is equipped with a cutting device to adjust and cut off the material flow, and the side of the hopper is equipped with an observation hole and a calibration metering device.

(4) Mold: The mold consists of an alloy steel inner sleeve and a carbon steel outer sleeve, and a molding mold is installed in the mold. The function of the mold is to transform the rotating plastic melt into parallel linear motion, introduce it into the mold sleeve evenly and stably, and give the plastic the necessary molding pressure. Plastic is plasticized and compacted in the barrel, and flows into the die from the neck of the die through the porous filter plate through a certain flow channel. The die sleeve is properly matched to form an annular gap with gradually decreasing cross section, so that the plastic melt can be in the core. In order to ensure the reasonable plastic flow channel in the mold and eliminate the dead angle of plastic accumulation, a shunt sleeve and a pressure equalizing ring are often installed to eliminate the pressure fluctuation during plastic extrusion. The die head is also equipped with a device for correcting and adjusting the die, which is convenient for adjusting and correcting the concentricity of the die core and the die sleeve.

According to the angle between the material flow direction of the die and the center line of the screw, the extruder can divide the die into oblique die (angle 120o) and right-angle die. The shell of the machine head is fixed on the machine body through bolts, and the die in the machine head has a die core seat, which is fixed on the wire inlet of the machine head through nuts. The mold core is installed in front of the mold core seat, and the centers of the mold core and the mold core seat are provided with holes for the core wire to pass through; An equalizing ring is installed in front of the machine head to equalize the pressure; The extrusion molding part consists of a die sleeve seat and a die sleeve, and the position of the die sleeve can be adjusted through bolt support, so that the relative position of the die sleeve and the die core can be adjusted, and the thickness uniformity of the extrusion layer can be adjusted conveniently. A heating device and a temperature measuring device are installed outside the machine head.

2. Transmission system The function of the transmission system is to drive the screw and supply the torque and speed required by the screw in the extrusion process, which is usually composed of a motor, a reducer and a bearing.

3. Heating and cooling device Heating and cooling are necessary conditions for plastic extrusion process.

(1) At present, extruders usually adopt electric heating, which can be divided into resistance heating and induction heating. The heating plate is installed on the fuselage, neck and head. The heating device heats the plastic in the cylinder from the outside to raise the temperature to the temperature required by the process operation.

(2) Set a cooling device to ensure that the plastic is within the temperature range required by the process. Specifically, it is to eliminate the excess heat generated by the rotating shear friction of the screw, and to avoid the decomposition, scorching or difficult setting of plastics caused by too high temperature. Barrel cooling can be divided into water cooling and air cooling. Generally speaking, air cooling is more suitable for small and medium-sized extruders, and water cooling or a combination of the two forms is used for large extruders. Screw cooling mainly adopts central water cooling, aiming at increasing the solid conveying rate of materials, stabilizing the glue output and improving the product quality; However, the cooling at the hopper is to strengthen the conveying function of solid materials, prevent plastic particles from sticking and blocking the material opening due to temperature rise, and ensure the normal operation of the transmission part.

Second, the auxiliary equipment:

Auxiliary machines of plastic extrusion unit mainly include pay-off device, straightening device, preheating device, cooling device, traction device, meter, spark testing machine and take-up device. The use of extrusion unit is different, and the auxiliary equipment selected is also different, such as cutter, dryer, printing device, etc.

Straightening device: eccentricity is the most common kind of plastic extrusion waste, and various types of bending of wire core are one of the important reasons for insulation eccentricity. In the process of sheath extrusion, the scratch on the surface of sheath is often caused by the bending of cable core. Therefore, straightening devices in each extrusion unit are essential. The main types of straightening devices are: drum type (divided into horizontal and vertical); Pulley type (divided into single pulley and pulley block); The twisted wheel has many functions such as dragging, straightening and stabilizing tension. Press wheel (divided into horizontal and vertical), etc.

Preheating device: preheating of cable core is necessary for insulation extrusion and sheath extrusion. For the insulation layer, especially the thin insulation layer, no air holes are allowed, and the water and oil stains on the surface of the wire core can be completely removed by preheating at high temperature before extrusion. For sheath extrusion, its main function is to dry the cable core and prevent the possibility of air holes in the sheath due to moisture (or moisture around the cladding). Preheating can also prevent the residual internal pressure caused by quenching in the extrusion process of plastics. In the process of plastic extrusion, preheating can eliminate the wide temperature difference formed when the cold wire enters the high-temperature die and contacts with the plastic at the die mouth, and avoid the extrusion pressure fluctuation caused by the plastic temperature fluctuation, thus stabilizing the extrusion quantity and ensuring the extrusion quality. The extrusion unit adopts electric heating wire core preheating device, which requires sufficient capacity, fast temperature rise, high wire core preheating and cable core drying efficiency. The preheating temperature is limited by the linear velocity, which is generally similar to the head temperature.

Cooling device: the molded plastic extrusion coating should be cooled immediately after leaving the die, otherwise it will be deformed under the action of gravity. The cooling method is usually water cooling, which is divided into quick cooling and slow cooling according to the different water temperatures. Quenching is the direct cooling of cold water, which is beneficial to the forming of plastic extrusion coating. However, for crystalline polymers, due to sudden thermal cooling, internal stress is easy to remain in the extruded coating, which leads to cracks in the use process. Usually, the PVC plastic layer is quenched. Slow cooling is to reduce the internal stress of the product. Put the moisture at different temperatures into the cooling tank, so that the product can be gradually cooled and shaped. The extrusion of PE and PP adopts slow cooling mode, that is, after three stages of cooling: hot water, warm water and cold water.

Third, the control system:

The control system of plastic extruder includes heating system, cooling system and process parameter measurement system, which is mainly composed of electrical appliances, instruments and actuators (namely control panel and operation console). Its main functions are: to control and adjust the traction motors of the main and auxiliary machines, output the rotating speed and power that meet the technological requirements, and make the main and auxiliary machines work in harmony; Detect and adjust the temperature, pressure and flow of plastic in the extruder; Realize the control or automatic control of the whole unit.

The electrical control of extrusion unit can be roughly divided into two parts: transmission control and temperature control. The extrusion process includes temperature, pressure, screw revolution, screw cooling, barrel cooling, product cooling and outer diameter control, as well as traction speed, orderly arrangement of wires and constant tension take-up control from empty disk to full disk.

1. Temperature control of extruder main engine

The plastic extrusion of wire and cable insulation and sheath is carried out according to the deformation characteristics of thermoplastic, which makes it in a viscous state. In addition to the external heating of the screw and the barrel, it is required to melt and extrude the plastic, and the heat generated when the screw extrudes the plastic should also be considered. Therefore, it is required to consider the temperature of the main engine as a whole, not only to turn on and off the heating of the heater, but also to consider the factors of heat overflow from screw extrusion for cooling, and to provide effective cooling facilities. It is also required to correctly and reasonably determine the position and installation method of the measuring element thermocouple, which can accurately reflect the actual temperature of each section of the main engine from the reading of the temperature control instrument. It is also required that the precision of the temperature control instrument should be well matched with the system, so that the fluctuation stability of the whole host temperature control system can meet the requirements of various plastic extrusion temperatures.

2. Pressure control of extruder

In order to reflect the extrusion situation of the die, it is necessary to detect the die pressure during extrusion. Because there is no die pressure sensor in domestic extruders, the measurement of die pressure is usually replaced by the measurement of screw thrust after extrusion, and the screw load table (ammeter or voltmeter) can correctly reflect the extrusion pressure. The fluctuation of extrusion pressure is also one of the important factors leading to the instability of extrusion quality. The fluctuation of extrusion pressure is closely related to extrusion temperature, the use of cooling device and the length of continuous operation. When abnormal phenomena occur, they can be quickly eliminated. If it is necessary to reorganize production, it should be stopped decisively, which can not only avoid the increase of waste products, but also prevent accidents. The pressure state of plastic in the extrusion process can be known by detecting the reading of pressure gauge, and the back thrust limit value is generally taken for alarm control.

3. Control of screw speed

The adjustment and stability of screw speed is one of the important technical requirements of main engine transmission. The screw speed directly determines the glue output and extrusion speed. Normal production always wants to achieve the highest speed and high yield as much as possible. When the screw speed of the extruder needs to be started to the required working speed, the available speed regulation range is larger. Moreover, the stability of rotation speed is required, because the fluctuation of rotation speed will lead to the fluctuation of extrusion quantity and affect the extrusion quality, so the outer diameter of the cable will change under the condition of constant traction linear speed. Similarly, if the linear speed of the traction device fluctuates greatly, the outer diameter of the cable will also change. The linear speed of screw and traction can be reflected by the corresponding instruments on the operating table, and should be closely observed during extrusion to ensure high quality and high yield.

4. Outside diameter control

As mentioned above, in order to ensure the cable outer diameter size of the product, in addition to controlling the dimensional tolerance of the cable core, the extrusion temperature, screw speed and linear speed of the traction device should also be controlled and ensured. The measurement and control of the outer diameter comprehensively reflect the accuracy and level of the above control. In the equipment of the extrusion unit, especially in the high-speed extrusion production line, an on-line outer diameter detector should be equipped to detect the outer diameter of the cable at any time, feed back the out-of-tolerance signal, adjust the traction or screw speed, and correct the out-of-tolerance of the outer diameter.

5. Tension control required for winding.

In order to ensure the constant tension requirements of winding at different linear speeds, it is hoped that the winding device will have a wire storage tension adjustment mechanism from empty drum to full drum, or the winding of constant linear speed system and constant tension system will be considered electrically.

6. Electrical automation control of the whole machine

This is the process control requirement of realizing high-speed extrusion production line, which mainly includes: starting temperature interlock; Working pressure protection and interlocking; Proportional synchronous control of extrusion and traction drive: synchronous control of take-up and traction; On-line detection and feedback control of outer diameter; According to different needs, the control of single machine and whole machine tracking consists of components.

Four, the classification of extruder:

Plastic extruders are divided into twin-screw extruder and single-screw extruder.

Difference between two extruders:

Single screw machine and twin screw machine: one is a screw and the other is two screws. Both are driven by a single motor. Different screws have different power. The power of 50 cone pairs is about 20kW, and that of 65 cone pairs is about 37KW. Output is related to materials and screws. The output of 50 cone pairs is about 100- 150KG/H, 65.

Extruders can be divided into single screw, twin screw and multi-screw extruder according to the number of screws. At present, single-screw extruder is the most widely used, which is suitable for extrusion processing of general materials. The twin-screw extruder has the advantages of less friction heat generation, uniform shearing of materials, large screw conveying capacity, stable extrusion capacity, long residence time of materials in the barrel and uniform mixing.

SJSZ series conical twin-screw extruder has the characteristics of forced extrusion, high quality, wide adaptability, long service life, low shear rate, difficult decomposition of materials, good mixing plasticization performance, direct powder molding, automatic temperature control, vacuum exhaust and so on. Suitable for the production of pipes, plates, special-shaped materials and other products.

Single screw extruder plays an important role in plasticizing granulation machinery and molding machinery. In recent years, single-screw extruder has made great progress. At present, the large single-screw extruder for granulation produced in Germany has a screw diameter of 700mm and an output of 36 t/h.

The main sign of the development of single screw extruder lies in the development of its key component screw. In recent years, people have done a lot of theoretical and experimental research on screws. So far, there are nearly 100 kinds of screws, including separation type, shear type, barrier type, shunt type and wave type.

From the development of single screw, although the single screw extruder has been perfected in recent years, with the continuous development of polymer materials and plastic products, there will be more distinctive new screws and special single screw extruders. Generally speaking, single-screw extruder is developing towards high speed, high efficiency and specialization.

Twin-screw extruder has good feeding characteristics and is suitable for powder processing. Compared with single-screw extruder, twin-screw extruder has better functions of mixing, exhausting, reaction and self-cleaning, which is characterized by its superiority in processing plastics and mixtures with poor thermal stability. In recent years, foreign twin-screw extruders have made great progress, various forms of twin-screw extruders have been serialized and commercialized, and there are many manufacturers, which are roughly classified as follows:

(1) According to the relative position of the two axes, there are parallel points and conical points;

(2) According to the meshing procedure of two screws, there are meshing type and non-meshing type;

(3) According to the rotation direction of the two screws, there are the same direction and the different direction, and the different direction has the points of inward and outward; □

(4) According to the rotating speed of the screw, there are high speed and low speed;

(5) According to the structure of screw and barrel, it can be divided into integral type and combined type.

On the basis of twin-screw extruder, in order to process the mixture with poor thermal stability more easily, some manufacturers have developed multi-screw extruders such as planetary extruder.

Five, the mechanical principle of extruder:

Add water or an appropriate liquid to the raw material powder and keep stirring. Extrude the stirred material from a porous mold or metal mesh with high extrusion pressure.

Usually, after the material is put into a cylindrical container, it is extruded through a screw. After adopting frequency conversion technology, the pressure can be controlled, so as to select the most suitable linear speed.

Principle of single screw extruder

Generally, a single screw is divided into three sections according to the effective length, and the effective length of the three sections is determined according to the diameter, pitch and depth of the screw, which is generally divided into one third.

The last thread of the material port was originally called the conveying section: the material here is required not to be plasticized, but to be preheated and compacted under pressure. In the past, the old extrusion theory thought that the material here was loose, but later it proved that the material here was actually a solid plug, that is to say, the material here was solid like a plug after being extruded, so it was its function to complete the transportation task.

The second stage is called compression stage. At this time, the volume of the spiral groove gradually decreases from large to small, and the temperature should reach the plasticizing degree of the material. The compression generated here is from the conveying stage 3 to 1, which is called the compression ratio of the screw -3: 1. Some machines have also changed, and plasticized materials have entered the third stage.

The third section is the metering section, where the materials are kept at the plasticizing temperature, and only the molten materials are accurately and quantitatively transported and supplied to the machine head like metering pumps. At this time, the temperature should not be lower than the plasticizing temperature, but generally slightly higher.

Matters needing attention in the use of intransitive verbs extruder;

1, the extruder should rotate forward to avoid reverse rotation.

2, avoid running on an empty stomach, must be hot machine feeding operation, so as to avoid sticking (shaft) phenomenon.

3. It is forbidden for impurities such as iron to enter the inlet and outlet of the extruder, so as to avoid accidents and affect production.

4, safe electricity, grounding wire.

5. When the machine is running, it is forbidden to touch the rotating parts such as inlet, outlet, belt and gear by hand.

6, the machine should be injected with lubricating oil before use, so as to avoid damage to the machine.

[Edit this paragraph] Operating procedure of extruder

All types of products in the plastic extrusion production line have their operating characteristics. Only by knowing their working characteristics in detail can we give full play to the efficiency of the machine. Extruder is one of them. Master the operation points of extruder and use extruder correctly and reasonably. The use of screw extruder includes a series of links such as installation, adjustment, debugging, operation, maintenance and repair of the machine. Its use has the characteristics of ordinary machines, mainly in driving motors and reducers. However, the working system of screw extruder is unique, so special attention should be paid to its characteristics when using screw extruder.

The installation, adjustment and debugging of the machine are usually stipulated in the operating instructions of the extruder. The following briefly introduces the operating points, maintenance and repair of the extruder:

Operators must be familiar with the structural characteristics of the extruder, especially the structural characteristics of the screw, the characteristics of the control instruments for heating and cooling, and the characteristics and assembly of the die, so as to correctly grasp the extrusion process conditions and operate the machine correctly.

When making different plastic products, the working point of extruder is different, but there are also similarities. The following briefly introduces the same operation steps and key points of extruder operation when extruding various products.

1, preparation before driving

(1) Plastic used for extrusion molding. Raw materials shall meet the required drying requirements and be further dried if necessary. The raw materials are sieved to remove agglomerated particles and mechanical impurities.

(2) Check whether the water, electricity and gas systems in the equipment are normal, and ensure that the water and gas paths are unblocked without leakage, whether the electrical system is normal, and whether the heating system, temperature control and various instruments are reliable; Run the auxiliary machine at low speed and idle, and observe whether the equipment operates normally; Start the vacuum pump of the setting table and observe whether it works normally; Lubricate the lubrication parts of all kinds of equipment. If faults are found, eliminate them in time.

(3) Install the head and the sizing sleeve. According to the variety and size of the product, choose the specifications of the machine head. Install the nose in the following order.

Step 2 drive

(1) Start the car after constant temperature. Before starting, tighten the flange bolts of the die and extruder again to eliminate the thermal expansion difference between the bolts and the die. Tighten the cylinder head bolts diagonally and evenly. When tightening the nose hexagon nut with flange, the tightness around it should be consistent, otherwise it will run away.

(2) When starting, select the "Ready to Start" button, then connect the "Start" button, and then slowly turn the screw speed adjustment knob, and the screw speed will start slowly. Then gradually accelerate, while adding a small amount of material. Pay close attention to the indication changes of the host ammeter and various indicator heads when feeding. The screw torque shall not exceed the red mark (generally 65%-75% of the torque meter). Before the plastic profile is extruded, no one is allowed to stand in front of the mold to prevent the bolt from breaking or the raw materials from being wet and blistering, which may cause injury accidents. After the plastic is extruded from the die, it is necessary to slowly cool the extrudate, guide it to the traction device and the shaping die, and start these devices. Then according to the indicated value of the control instrument and the requirements of the extruded product. Adjust all parts accordingly, so that the whole extrusion operation can reach the normal state. Twin-screw extruder adopts metering feeder to feed at a uniform speed.

(3) When the die is evenly discharged and the plastic is excellent, it can be used to draw the sleeve. The degree of plasticization can be judged by experience, generally according to the appearance of the extrudate, that is, the surface is shiny, free from impurities, blistering, scorching and discoloration. The material extruded by hand has no burr and crack to a certain extent, and has certain elasticity, which shows that the material has good plasticizing effect. If the plasticization is poor, the screw speed, barrel and head temperature can be adjusted appropriately until the requirements are met.

(4) In the process of extrusion production, the process parameters should be checked regularly according to the process requirements, and the process record sheet should be filled in. Check the quality of profile products according to quality inspection standards, and take timely solutions when problems are found.

Step 3 stop the car

(1) Stop feeding and extrude the plastic from the extruder. When the screw is exposed, turn off the power supply of the barrel and the head and stop heating.

(2) Turn off the power supply of the extruder and the auxiliary machine, so that the screw and the auxiliary machine stop running.

(3) Open the nose connecting flange and remove the nose. Clean the perforated plate and various parts of the machine head. When cleaning, in order to prevent damage to the inner surface of the machine head, the residual materials in the machine head should be cleaned with steel ruler and steel sheet, and then the plastic adhered to the machine head should be ground off with sandpaper, and then coated with engine oil or silicone oil for rust prevention.

(4) Cleaning the spiral tube: after the nose is removed, restart the main engine, add parking materials (or scraps) and clean the spiral tube. At this time, the screw is selected at low speed (about sr/min) to reduce wear. After the stopped material is ground into powder and completely extruded, the residual granular material and powder can be repeatedly blown out by compressed air from the inlet and outlet until there is no residual material in the barrel, then the screw speed is reduced to zero, the extruder is stopped, and the main power supply and the main cold water valve are closed.

(5) The safety matters that should be paid attention to in the extrusion process of the extruder are: the rotation of electricity, heat and machinery, and the loading and unloading of heavy objects. The extruder workshop must be equipped with lifting equipment, loading and unloading heavy parts such as head and screw to ensure safe production.

Technical Innovation of China Extruder

In recent years, conventional extruders and production lines in China have gradually become popular in the international market with excellent cost performance. At the same time, China has continuously innovated in the field of advanced extrusion technology and developed a variety of new extrusion products. Precision extrusion technology meets the needs of high precision machining.

Precision extrusion molding can avoid subsequent processing means, better meet the needs of product application, and achieve the purpose of reducing material cost and improving product quality. Nowadays, many mature technologies have been introduced to meet the demand of precision direct extrusion of plastic products, and polymer melt gear pump is one of the important means. This technology has been widely used in chemical fiber, film, profile, pipe, plate, cable, compound extrusion, granulation and other production lines.

After years of systematic research on melt gear pumps, beijing university of chemical technology Rubber & Plastic Machinery Research Institute has successfully completed the serial development of plastic melt gear pumps. Now we can design and manufacture 28/28 (center distance/tooth width), 56/56, 70/70, 90/90 and other plastic melt gear pumps. The maximum pressure difference between inlet and outlet can reach 30MPa, which can meet the requirements of different outputs. It has been applied in practice and achieved good results. Beijing university of chemical technology Rubber & Plastic Machinery Research Institute designed and developed 1 15 integrated gear pump extruder through in-depth research on the integrated gear pump extruder.

Gear pump is also of great benefit to the precision molding of rubber industry. In order to meet the domestic demand for rubber melt gear pumps, beijing university of chemical technology also cooperated with Beijing Institute of Aeronautical Engineering and Hangzhou Chaoyang Rubber Co., Ltd. to develop two types of rubber melt gear pump extrusion units, XCP 150/ 100 and XCP 120/90. The unit has ideal working characteristics, which can ensure the linear relationship between extrusion and gear pump speed, realize accurate control of output and improve the dimensional accuracy of products.

Multilayer extrusion technology has matured and developed.

Multi-layer composite technology is to combine materials with medium and high barrier properties with other packaging materials, and combine the high barrier properties of barrier materials with the cheap or special mechanical and thermal properties of other materials to achieve specific functional requirements. * * * The structural design of extruded composite film gradually requires that it can systematically achieve the ideal state of integrating function, technology, cost, environmental protection, safety and secondary processing, so that the possibility of maximizing the number of composite layers becomes one of the technologies pursued by suppliers. The seven-layer composite film extrusion blow molding technology of Guangdong Jin Ming Plastic Equipment Co., Ltd. is a typical development in this field in China.

The key technologies adopted by the seven-layer composite film extrusion blow molding unit include: two short and one long variable pitch screw plasticizing extrusion system, optimization design of vibration-induced plasticizing device by engineering analysis software, plane valve plus molding die and inclined valve plus molding die, double tuyere internal cooling technology and negative pressure cooling technology, multi-component weightless metering and feeding, online film thickness accurate control system, computer centralized automatic control system and CANOPEN technology.

With the increase of layers, the film production technology adapted to special functions is also one of the hot spots in the market development. Recently, Guangdong Shicheng Company designed and manufactured a PP environmentally-friendly wood grain film casting production line with a width of 3 150 mm ... The production capacity of this production line exceeds 800 kg/hour. Screw is designed for high-speed shearing, mixing and high-efficiency plasticization. Customers can directly use highly filled calcium carbonate powder and inorganic pigment toner, saving expensive raw material costs. The whole line can not only produce PP environmentally-friendly wood grain film, but also flexibly switch to other products to broaden the product categories of customers. During the trial production, Shicheng Company not only produced beautiful PP wood grain film, but also produced cast polypropylene, PP stationery film and PP stationery sheet.

Innovative three-screw composite technology

Parallel co-rotating twin-screw extruder is used in compound granulation production line. After nearly 20 years of rapid development, this technology has been quite mature. On the other hand, the traditional meshing disc and reciprocating screw extruder meet the needs of high filling and compounding, and the degree of industrialization is constantly improving.

[Edit this paragraph] Failure analysis of extruder

Extruder is a common plastic mechanical equipment. In the daily operation of extruder, there will be various failures, which will affect the normal production of plastic machinery. Let's analyze the failure of the extruder.

Failure analysis of extruder: the main engine current is unstable.

1, production reason:

(1) uneven feeding.

(2) The main motor bearing is damaged or poorly lubricated.

(3) heater failure, no heating.

(4) The screw adjusting pad is wrong, or the phase is wrong, and the components interfere.

2. Treatment method:

(1) Check the paper feeder and troubleshoot.

(2) Repair the main motor and replace the bearing if necessary.

(3) Check whether the heater works normally, and replace the heater if necessary.

(4) Check the adjusting pad, and pull out the screw to check whether there is interference.

Failure analysis of extruder: the main motor cannot be started.

1, reason:

(1) Error in starting the program.

(2) There is something wrong with the thread of the main motor, and whether the fuse is blown.

(3) Interlocking device related to the main motor.

2. Treatment method:

(1) Check the procedure and restart the vehicle in the correct order.

(2) Check the main motor circuit.

(3) Check whether the lubricating oil pump is started, and check the status of related interlocking devices of the main motor. The oil pump is not turned on and the motor cannot be started.

(4) If the induction power of the frequency converter is not used up, turn off the main power supply and wait for 5 minutes before starting.

(5) Check whether panic button is reset.

Failure analysis of extruder: the die discharge is not smooth or blocked.

1, reason:

(1) The primary heater doesn't work, and the material has poor plasticization.

(2) The operating temperature is set low, or the molecular weight distribution of plastic is wide and unstable.

(3) There may be foreign objects that are not easy to melt.

2. Treatment method:

(1) Check the heater and replace it if necessary.

(2) Verify the set temperature of each section, and negotiate with the technologist to raise the set temperature if necessary.

(3) Clean and check the extrusion system and head.

Failure analysis of extruder: the starting current of main electricity is too high.

1, reason:

(1) insufficient heating time and large torque.

(2) The heater does not work.

2. Treatment method:

(1) Turn the car by hand while driving. If it is not easy, extend the heating time or check whether the heaters in each section work normally.

Failure analysis of extruder: the main motor makes abnormal noise.

1, reason:

(1) The main motor bearing is damaged.

(2) The thyristor in the main motor rectifier circuit is damaged.

2. Treatment method:

(1) Replace the main motor bearing.

(2) Check the silicon controlled rectifier circuit and replace the silicon controlled element when necessary.

Failure analysis of extruder: the bearing temperature of main motor is too high.

1, reason:

(1) The bearing is not lubricated well.

(2) The bearing is badly worn.

2. Reason:

(1) Check and add lubricant. Check the motor bearing and replace it if necessary.

Failure analysis of extruder: unstable head pressure.

1, reason:

(1) The speed of the main motor is uneven.

(2) The speed of the feed motor is uneven, and the feed rate fluctuates.

2. Treatment method:

(1) Check the main motor control system and bearings.

(2) Check the motor and control system of the feeding system.

Failure analysis of extruder: low lubricating oil pressure

1, reason:

(1) The pressure setting of the pressure regulating valve in the lubricating oil system is too low.

(2) Oil pump failure or oil suction pipe blockage.

2. Treatment method:

(1) Check and adjust the pressure regulating valve of lubricating oil system.

(2) Check the oil pump and oil suction pipe.

Failure analysis of extruder: the automatic screen changing device is slow or ineffective.

1, reason:

(1) Low air pressure or oil pressure.

(2) Air leakage (or oil leakage) in the cylinder (or hydraulic station)

2. Treatment method:

(1) Check the power supply system of the network changing device.

(2) Check the sealing condition of the air cylinder or hydraulic cylinder.

Failure analysis of extruder: the safety pin or key is cut off.

1, reason:

(1) Excessive torque in the extrusion system.

(2) The main motor and the input bearing are not connected concentrically.

2. Treatment method:

(1) Check whether metal and other things enter the jammed screw in the extrusion system. At the beginning, check whether the preheating time or calorific value is up to standard.

Meet the requirements.

(2) Adjust the main motor

Failure analysis of extruder: the extrusion volume suddenly decreased.

1, reason:

(1) The feeding system is faulty or there is no material in the hopper.

(2) The extrusion system enters the hard screw to block the passage of materials.

2. Treatment method:

(1) Check the material level of the feeding system or hopper.

(2) Check and clean the extrusion system.