According to the angle between the die flow direction and the center line of the screw, the die head of the extruder is divided into an angled die head and a right-angle die head. The shell of the die head is fixed to the body with bolts. The mold inside the die head has a core seat and is fixed to the die head inlet port with a nut. The front of the core seat is equipped with a core. The center of the core and the core seat has a hole for passing the core wire. A pressure equalizing ring is installed at the front of the die head for equalizing pressure. The extrusion molding part consists of a die sleeve seat and a die sleeve. The position of the die sleeve can be adjusted by bolts through the support to adjust the relative position of the die sleeve to the die core, so as to facilitate the adjustment of the uniformity of the thickness of the extruded layer. A heating device and a temperature measuring device are installed on the outside of the die head.

Equipment Introduction

The main machine of the plastic granulator is an extruder, which consists of an extrusion system, a transmission system, and a heating and cooling system. Vigorously develop renewable resources and turn waste into treasure.

1. Extrusion system The extrusion system includes a hopper and a die. The plastic is plasticized into a uniform melt through the extrusion system and is continuously extruded out of the die by the screw under the pressure built up in the process.

Screw: It is the most important component of the extruder. It is directly related to the application range and productivity of the extruder. It is made of high-strength and corrosion-resistant alloy steel.

Barrel: It is a metal cylinder, generally made of alloy steel or composite steel pipe lined with alloy steel that is heat-resistant, high in pressure resistance, strong, wear-resistant and corrosion-resistant. The barrel cooperates with the screw to realize the crushing, softening, melting, plasticizing, exhausting and compacting of the plastic, and continuously and evenly transports the rubber to the molding system. Generally, the length of the barrel is 15 to 30 times its diameter, so that the plastic can be fully heated and fully plasticized.

Hopper: A cut-off device is installed at the bottom of the hopper to adjust and cut off the material flow. A sight hole and a calibrated metering device are installed on the side of the hopper.

Die head and mold: The die head is composed of an alloy steel inner sleeve and a carbon steel outer sleeve, and a molding mold is installed in the die head. The function of the die head is to convert the rotating plastic melt into parallel linear motion, evenly and smoothly introduce it into the mold sleeve, and give the plastic the necessary molding pressure. The plastic is plasticized and compacted in the barrel, and flows into the die head molding mold through the porous filter plate along a certain flow channel through the die neck. The mold core and the mold sleeve are properly matched to form an annular gap with a continuously decreasing cross-section, so that the plastic melt forms a continuous and dense tubular coating around the core line. In order to ensure the reasonable plastic flow channel in the die head and eliminate the dead corners of accumulated plastic, a diverter sleeve is often installed. In order to eliminate pressure fluctuations during plastic extrusion, an equalizing ring is also set. The die head is also equipped with a mold correction and adjustment device to facilitate the adjustment and correction of the concentricity of the mold core and the mold sleeve.

2. Transmission system The function of the transmission system is to drive the screw and provide the torque and speed required by the screw during the extrusion process. It is usually composed of a motor, a reducer and bearings.

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

In 2013, the extruder usually uses electric heating, which is divided into resistance heating and induction heating. The heating plate is installed on the body, neck and head of the machine. The heating device heats the plastic in the cylinder from the outside to raise the temperature to reach the temperature required for the process operation.

The cooling device is set up 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 shear friction of the screw rotation to avoid excessive temperature causing the plastic to decompose, burn or become difficult to shape. Barrel cooling is divided into water cooling and air cooling. Generally, air cooling is more suitable for small and medium-sized extruders, while large ones mostly use water cooling or a combination of the two forms of cooling; screw cooling mainly uses central water cooling, the purpose is to increase the solid material conveying rate, stabilize the glue output, and improve product quality; but the cooling at the hopper is to strengthen the conveying effect of solid materials, prevent the plastic particles from becoming sticky and blocking the material port due to temperature rise, and to ensure the normal operation of the transmission part.

Energy Saving

The energy saving of plastic granulator can be divided into two parts: one is the power part and the other is the heating part.

Energy saving in the power part : Most of them use frequency converters. The energy saving method is to save the surplus energy of the motor. For example, the actual power of the motor is 50Hz, but you only need 30Hz in production. The excess energy is wasted. The frequency converter changes the power output of the motor to achieve energy saving.

Energy saving in heating part : Energy saving in heating part mostly adopts electromagnetic heater, and the energy saving rate is about 30%-70% of the old resistance coil.

1. Compared with resistance heating, electromagnetic heater has an extra insulation layer, which increases the utilization rate of thermal energy.

2. Compared with resistance heating, electromagnetic heater directly heats the material tube, reducing heat transfer and heat energy loss.

3. Compared with resistance heating, the heating speed of electromagnetic heater is more than one-quarter faster, which reduces the heating time.

4. Compared with resistance heating, electromagnetic heaters heat faster, which improves production efficiency and keeps the motor in a saturated state, reducing the energy loss caused by high power and low demand.

The above four points are the reasons why electromagnetic heaters can save energy up to 30%-70% on plastic granulators.

Components

Crusher

There are many types of crushers for plastic products, including shear crushers suitable for crushing various types of plastic products, impact crushers and compression crushers suitable for crushing brittle plastic products, etc. The most widely used shear crusher consists of a base, a crushing chamber, a hopper, a screen plate, a transmission mechanism, a rotating knife and a fixed knife.

The working method of the shearing type plastic crusher is very simple: the shearing tool consists of a rotating blade and a fixed blade, and the rotating blade is driven by an electric motor; the waste plastic to be crushed is sent into the crushing chamber from the feeding hopper, is chopped when passing through the high-speed rotating cutter, and then flows out of the machine through the porous screen plate.

Washing machine

The function of the cleaning machine is to remove the dirt and sand stuck on the plastic by turning and stirring the waste plastic in the sink through a pair of rotating stirring blades and flushing with water; then the plastic fragments are picked out of the water through the lifting device and transported to the dehydration process.

Dehydrator

The dehydrator has a simple structure, similar to that of a household spin dryer, and its working method is also similar. It mainly uses the centrifugal force of high-speed rotation to remove moisture from the crushed plastic in the drum.

Dryer

The plastic that has been crushed, cleaned and dehydrated still has a certain degree of moisture. The function of the dryer is to send it through the feeding port into the wind tube with hot air circulation to evaporate the moisture in the material and dry the plastic to meet the needs of the extrusion granulation process.

Extruder

The extruder is a venting extruder, and its function is to re-mix the crushed, cleaned and dried plastic, heat it into a molten state, and then extrude and pelletize it.

Since the sources of waste plastic products are relatively complex, there are many types of mixed materials, and there are more volatiles, moisture and other components in the materials, so it is more appropriate to use a exhaust extruder.

The exhaust extruder mixes and melts waste plastics. The material shape is relatively special, so a spiral forced feeding device is used; a filter is added before the barrel, and the molten material is extruded through a porous plate and then pelletized. The waste material recycling is to cool and shape the extruded strips in a water tank before pelletizing.

Auxiliary equipment

The auxiliary equipment of the plastic granulation unit mainly includes the wire release device, straightening device, preheating device, cooling device, traction device, meter counter, spark tester, wire take-up device. The auxiliary equipment selected for the extruder unit is different for different purposes. For example, there are also cutters, dryers, printing devices, etc.

Straightening device: The most common type of plastic extrusion waste is eccentricity, and various types of bending of the core are one of the important reasons for insulation eccentricity. In sheath extrusion, scratches on the sheath surface are often caused by the bending of the cable core. Therefore, straightening devices are indispensable in various extrusion units. The main types of straightening devices are: drum type (divided into horizontal and vertical types); pulley type (divided into single pulley and pulley group); winch type, which has multiple functions such as dragging, straightening, and stabilizing tension; pressure wheel type (divided into horizontal and vertical types), etc.

Preheating device

Cable core preheating is necessary for both insulation extrusion and sheath extrusion. For the insulation layer, especially the thin layer insulation, the existence of pores is not allowed. The surface moisture and oil can be completely removed by high temperature preheating of the core before extrusion. For sheath extrusion, its main function is to dry the cable core to prevent the possibility of pores in the sheath due to moisture (or moisture in the wrapping cushion layer). Preheating can also prevent the residual internal pressure of the plastic due to sudden cooling during extrusion. In the process of extruding plastic, preheating can eliminate the large temperature difference formed when the cold wire enters the high-temperature die and contacts the plastic at the die mouth, avoid the fluctuation of the extrusion pressure caused by the fluctuation of the plastic temperature, thereby stabilizing the extrusion volume and ensuring the extrusion quality. Electric heating core preheating devices are used in extrusion units, which are required to have sufficient capacity and ensure rapid heating, so that the core preheating and cable core drying efficiency are high. The preheating temperature is restricted by the pay-off speed, and is generally similar to the die temperature.

Cooling device

The formed plastic extruded layer should be cooled and shaped immediately after leaving the die, otherwise it will deform under the action of gravity. Water cooling is usually used for cooling, and it is divided into rapid cooling and slow cooling according to the water temperature. Rapid cooling is direct cooling with cold water. Rapid cooling is beneficial to the shaping of the plastic extruded layer, but for crystalline polymers, due to sudden cooling, internal stress is easily left inside the extruded layer, resulting in cracking during use. Generally, PVC plastic layer adopts rapid cooling. Slow cooling is to reduce the internal stress of the product. Water of different temperatures is placed in the cooling water tank in sections to gradually cool down the product and shape it. Slow cooling is used for the extrusion of PE and PP, that is, it is cooled in three stages: hot water, warm water, and cold water.

Control system

The control system of the plastic granulator includes a heating system, a cooling system and a process parameter measurement system, which is mainly composed of electrical appliances, instruments and actuators (i.e., control panels and operating tables). Its main functions are: controlling and adjusting the traction motors of the main and auxiliary machines, outputting the speed and power that meet the process requirements, and enabling the main and auxiliary machines to work in coordination; detecting and adjusting the temperature, pressure and flow of the plastic in the extruder; and realizing the control or automatic control of the entire unit.

The electrical control of the extruder unit is roughly divided into two parts: transmission control and temperature control, which realizes the control of the extrusion process including temperature, pressure, screw speed, screw cooling, barrel cooling, product cooling and outer diameter, as well as the pulling speed, neat wire arrangement and constant tension wire taking-up control from empty to full on the take-up reel.

Temperature control

Temperature control of the main machine of the extruder. The plastic extrusion of the insulation and sheath of the wire and cable is carried out in a viscous flow state according to the deformation characteristics of thermoplastics. In addition to the requirement of external heating of the screw and barrel to transfer to the plastic to melt and extrude it, the heat generated by the screw itself when extruding the plastic must also be considered. Therefore, the temperature of the main machine should be considered as a whole, not only considering the on and off of the heater heating, but also considering the factors of the extrusion heat overflow of the screw for cooling, and effective cooling facilities are required. It is also required to correctly and reasonably determine the position and installation method of the measuring element thermocouple, and the actual temperature of each section of the main machine can be accurately reflected from the reading of the temperature control instrument. And it is required that the accuracy of the temperature control instrument is well matched with the system, so that the fluctuation stability of the entire main machine temperature control system meets the requirements of the extrusion temperature of various plastics.

Pressure control

Pressure control of extruder In order to reflect the extrusion situation of the die head, it is necessary to detect the die head pressure during extrusion. Since domestic extruders do not have die head pressure sensors, the measurement of the thrust after screw extrusion is generally used instead of the measurement of die head pressure. The screw load meter (ammeter or voltmeter) can correctly reflect the size of the extrusion pressure. The fluctuation of extrusion pressure is also one of the important factors causing unstable extrusion quality. The fluctuation of extrusion pressure is closely related to factors such as extrusion temperature, the use of cooling device, and the length of continuous operation time. When an abnormal phenomenon occurs, it can be quickly eliminated if it can be eliminated. If production must be reorganized, it should be stopped decisively, which can not only avoid the increase of waste products, but also prevent accidents. By detecting the pressure gauge reading, you can know the pressure state of the plastic during extrusion, and generally take the rear thrust limit value for alarm control.

Screw speed control

The regulation and stability of the screw speed is one of the important process requirements for the main engine transmission. The screw speed directly determines the amount of glue and the extrusion speed. In normal production, we always hope to achieve the highest speed and high production as much as possible. The extruder requires that the speed range available for the screw speed from the start to the required working speed should be large. In addition, the stability of the speed is required to be high, because the fluctuation of the speed will lead to the fluctuation of the extrusion amount and affect the extrusion quality. Therefore, if the traction line speed does not change, it will cause the outer diameter of the cable to change. Similarly, if the line speed of the traction device fluctuates greatly, it will also cause the outer diameter of the cable to change. The screw and traction line speeds can be reflected by the corresponding instruments on the operating table. Close observation should be made during extrusion to ensure high quality and high yield.

Outer diameter control

As mentioned above, in order to ensure the outer diameter of the finished cable, in addition to the requirement to control the dimensional tolerance of the wire core (cable core), the extrusion temperature, screw speed, and traction device linear speed should be controlled and guaranteed, and the measurement and control of the outer diameter comprehensively reflects the accuracy and level of the above control. In the extrusion unit equipment, especially the high-speed extrusion production line, an online outer diameter detector should be used to detect the outer diameter of the cable at any time, and the out-of-tolerance signal should be fed back to adjust the traction or screw speed to correct the outer diameter out-of-tolerance.

Tension control required for winding

In order to ensure the constant tension requirement of wire taking-up at different line speeds and from empty reel to full reel, it is hoped that the wire taking-up and arranging device has a wire storage tension adjustment mechanism, or that the winding of the constant line speed system and the constant tension system can be considered electrically.

Electrical automation control of the whole machine

These are the process control requirements for realizing high-speed extrusion production lines, mainly including: start-up temperature interlock; working pressure protection and interlock; proportional synchronization control of the transmission of the two major components of extrusion and traction; synchronization control of wire collection and traction; online detection and feedback control of outer diameter; and control of single-machine and complete-machine tracking of components according to different needs.

Applications

With special screw design and different configurations, it is suitable for the recycling and color mixing of various plastics such as PP, PE, PS, ABS, PA, PVC, PC, POM, EVA, LCP, PET, PMMA, etc. The reduction box adopts high torque design to achieve noiseless and stable operation. The screw and barrel are specially hardened and have the characteristics of wear resistance, good mixing performance and high output. The design of vacuum exhaust or ordinary exhaust port can discharge moisture and waste gas during the production process, making the discharge more stable and the rubber particles more solid, ensuring the excellent quality of the product.

Plastic granulator is mainly used for processing waste plastic film (industrial packaging film, agricultural mulch film, greenhouse film, beer bags, handbags, etc.), woven bags, agricultural convenience bags, basins, barrels, beverage bottles, furniture, daily necessities, etc. It is suitable for most common waste plastics and is the most widely used and popular plastic recycling processing machinery in the waste plastic recycling industry.

Features

1. All recycled materials can be used for production without drying, drying or sun drying after classification, crushing and cleaning.
2. From raw material crushing, cleaning, feeding to granulation, everything is automated.
3. Make full use of the high-pressure friction uninterrupted heating system to automatically heat the production, avoid continuous heating, and save electricity and energy.
4. Adopt split fully automatic power distribution system to ensure the safe and normal operation of the motor.
5. The screw and barrel are made of imported high-strength high-quality carbon structural steel, which is durable.
6. The machine has a beautiful appearance. It can be painted according to customer requirements.

Production Process

Raw material classification → Raw material crushing and cleaning → Automatic feeding into the main machine for plasticization → Auxiliary machine extrusion → Water or air cooling → Automatic pelletizing → Bagging

Mould

Plastic granulator molds are divided into manual and electric. The granulator needs to change the screen frequently to remove impurities. The extrusion mold is generally 18 holes. When the filter screen is blocked, the extruder pressure is very high. The original manual screen change will be tiring. Electric molds can be used to replace manual labor with electric motors, saving time and effort.

Automatic Stirring

Automatic mixing plastic granulator is a plastic granulating machine suitable for waste film, waste silk, waste woven bags, waste plastic bottles, waste plastic barrels, boards and broken materials.

Troubleshooting

1. The screw operates normally, but no material is discharged

Causes: The hopper feeds discontinuously; the feed port is blocked by foreign matter or “bridges” are formed; a hard metal object falls into the screw groove and blocks the screw groove, preventing normal feeding;

Solution: Increase the feed amount to make the screw feed continuous and stable; stop the machine to remove foreign matter in the material port to eliminate the “bridging” phenomenon; if it is confirmed that metal foreign matter has fallen into the screw groove, stop the machine immediately, disassemble the screw, and remove the metal foreign matter.

2. The host does not rotate or stops instantly

Cause: The power supply of the main motor is not connected; the heating time is insufficient, or one of its heaters is not working, resulting in excessive torque and overload of the motor.

Solution: Check whether the host circuit is connected and turn on the power; check the temperature display of each section, confirm the preheating time, check whether each heater is damaged or has poor contact, and eliminate it.

3. Material leaking from the exhaust hole

Cause: The raw materials are not clean enough and contain impurities; the feed speed is too fast, making the screw extrusion unstable; the plasticizing temperature is not high enough, causing problems with screw extrusion.

Solution: Clean the raw materials before feeding or replace the filter; reduce the feed amount to allow the plasticizing and stable screw to extrude smoothly; increase the plasticizing temperature (the temperature should not be too high to prevent burning the plastic and affecting production quality).

4. The main motor rotates, but the screw does not turn

Cause: The transmission V-belt is loose, worn and slipping; the safety key is loose, falls off or disconnected.

Solution: Adjust the center distance of the V-belt, tighten the belt, or replace a new V-belt; check the safety key, analyze the cause of the breakage, and replace the safety key.

Operating Details

Purpose

The purpose of standardized equipment operation and maintenance is to ensure the normal operation of the equipment and extend its life, reduce maintenance costs and improve production efficiency.

Scope of application

It is only applicable to the operating instructions of production line equipment such as TPR∕EVA∕PVC/masterbatch/halogen-free cable materials/rubber high-filling engineering materials produced by this company.

Special Responsibilities

The equipment operators and maintenance personnel designated by the user unit shall not operate the equipment in violation of regulations and must be skilled in operating the equipment. They shall supervise irrelevant personnel to prevent them from approaching, tampering with, or damaging the equipment.

Assignment Details

1. Turn on the power supply in turn, set the temperature and pay attention to whether the heating is normal.
2. Clean the hopper and other units, inlet and outlet water pipes, check the oil level and lubrication status of each gear oil, engine oil, and high-temperature butter. The gear oil of a new machine should be replaced at least once every six months, and lubricating oil should be added to the moving parts at least once a week.
3. When the temperature is about to reach the set temperature, prepare the materials and start the main motors in sequence.
4. The temperature of the extruder must reach the set temperature, and the feeding device must be turned on to pour the cleaning material or raw material to clean the residue in the screw until the new material is extruded, then stop extruding, and quickly install the filter plate and die head in place. The die head can be closed, and the main screw motor of the granulator is turned on after the die head is closed. The operator should stay away from the die head at this time to prevent the die head from being blocked by hard materials and bursting and injuring people, until the die head extrude the wire material, then close the pelletizing cover and connect the cutting knife holder and lock it.
5. After the above operations are completed, start all fans > vibrating screen > pelletizer > main machine in sequence.
6. When discharging pellets normally, adjust the pelletizer and adjust the particle size by frequency conversion. The screw must keep the pelletizer rotating before discharging. If it is a water-cooled spray pelletizer, the pelletizer cover must be filled with water first, and finally the main machine must be turned on for formal production.
7. Start the extruder and adjust the frequency conversion speed of the main machine and pelletizer from slow to fast according to the particle size requirements. Only by achieving coordination between the two can the cut particles be more uniform and the particle output be maximized.
8. The operation sequence of stopping operation is opposite to that of starting production. First turn off the main machine drive, then turn off the auxiliary machine power in turn, and finally quickly clean the die head to prevent the die head from cooling and clogging (special attention: after each shift of operation, the die head discharge hole and filter plate must be completely cleaned before reinstalling production, otherwise the die head is in danger of explosion due to blockage).

Notes

1. It is strictly forbidden for irrelevant personnel to talk with the equipment operator, and only one person is allowed to operate the button instructions on the electric control panel;
2. Regularly check the insulation effect of wires and circuits, and always pay attention to the warning content on the machine warning sign;
3. Before the power distribution cabinet is powered off, non-professionals are strictly prohibited from opening the cabinet door, and it is strictly prohibited to adjust the cutter before the pelletizer is completely stationary;
4. When the moving parts and hopper are blocked, do not use your hands or iron rods, but only use plastic sticks to handle them carefully;
5. Be careful of burns when touching high-temperature parts. When the kneading machine is working, it is strictly forbidden for workers to put their upper body into the barrel to check or pick materials;
6. If there is a power outage during operation, the motor circuits should be cut off and the materials stored in the machine should be cleaned up in time. Carbonization of the materials will affect the next production.
7. When the machine breaks down, stop the machine immediately and do not take any action on your own. Notify and wait for the mechanic to come and check or provide guidance on the repair by phone;
8. Prevent all factors from causing machine damage and work-related accidents; operate strictly in accordance with standardized operating methods to reduce the occurrence of failures or accidents.