The basic mechanism of the twin screw extrusion process is simply that a screw rotates in the barrel and pushes the plastic forward. The screw structure is a bevel or ramp wrapped around a central layer, the purpose of which is to increase the pressure to overcome the higher resistance. What do I need to pay attention to when using a twin screw extruder? The following is a detailed description.
Here is the content list:
l Structural principles
l Temperature principles
l Speed reduction principle
For the extruder, there are three kinds of resistance to overcome when working: one is friction, which contains the friction of the solid particles (feed) on the barrel wall and the mutual friction between them during the first few turns of the screw (feed area); the second is the adhesion of the melt on the barrel wall, and the third is the resistance of the internal logistics of the melt when it is pushed forward.
According to Newton's theorem, if an object is at rest in a certain direction, then the object is in a state of equilibrium balance of forces in this direction. For the circumferential movement of the screw, it is no axial motion, that is, the axial force on the screw is in equilibrium. So if the screw exerts a large forward thrust on the plastic melt, it also exerts a backward thrust on another object of the same magnitude but in the same direction. The thrust is exerted on the thrust bearing behind the feed opening. Most single screws have right hand threads, and if viewed from the back, they rotate backward, and they spin backward out of the barrel by rotational motion. In some twin screw extruders, however, the two screws rotate backward and cross each other in both barrels, so one must be right handed and one left handed, and in the case of an occluding twin screw, both screws rotate in the same direction and must therefore have the same orientation. However, in either case, there are thrust bearings that withstand backward forces and still comply with Newton's theorem.
Plastics extruded by twin screw extruders are thermoplastics, which melt when heated and solidify again when cooled. Thus, heat is needed during the extrusion process to ensure that the plastic can reach the melting temperature. So where does the heat to melt the plastic come from? First of all, the pound feed preheat and barrel/die heaters may play a role and are very important at startup. In addition, the motor feed energy, the frictional heat generated in the barrel as the motor overcomes the resistance of the viscous melt and turns the screw, is the most important heat source for all plastics, except for small systems, low speed screws, high melt temperature plastics, and extrusion coating applications. In operation, it is important to recognize that the barrel heater is not the primary heat source and that it may play a smaller role in extrusion than we might expect. The post barrel temperature is more important because it affects the rate of solids transport in the dentition or feed. In general, except for a specific purpose (such as varnishing, fluid distribution, or pressure control), the die head and die temperature should be at or near the temperature required for the melt.
In most twin screw extruders, the screw speed is varied by adjusting the motor speed. The drive motor usually turns at a full speed of about 1750 rpm, which is too fast for an extruder screw. If it turns at such a fast speed, too much frictional heat is generated and a uniform, the well mixed melt cannot be prepared because the retention time of the plastic is too short. A typical speed reduction ratio should be between 10:1 and 20:1, with either a gear or pulley set for the first stage, but with a gear and a screw positioned in the center of the last large gear for the second stage. For some slow running machines (eg. twin screws for UPVC), there may be three reduction stages and the maximum speed may be as low as 30 rpm or less (ratio up to 60:1). On the other hand, some very long twin screws for mixing can run at 600 rpm or faster, thus requiring a very low reduction rate and more deep cooling. If the reduction rate is incorrectly matched to the job, too much energy will be wasted. It may be necessary to add a pulley set between the motor and the first deceleration stage where the maximum speed is changed, which either increases the screw speed even beyond the previous limit or reduces the maximum speed. This increases the available energy, reduces the current value, and avoids motor failure, in both cases, the output may increase due to the material and its cooling needs.
If you still have questions, you can consult our company. Nanjing JlEYA is the leading professional manufacturer of twin screw extruders in China.
The drive section of the twin screw extruder consists of 3 parts: motor, clutch, and gearbox.
The reduction and distribution gear unit reduces the motor speed to the screw shaft speed and distributes the input torque to the two output shafts. Clutch is installed between the drive motor and the gearbox drive shaft.
The processing section of the twin screw extruder in SHJ series extruder consists of individual barrel sections which are replaceable. Depending on the process tasks, reserve feed port, liquid injection port or twin screw side feed port is available.
Owing to the modular design of the twin screw extruder screw elements and screw barrels, conveying, plasticizing, homogenizing, pressure build-up and devolatilization zones can be established, depending on the process task.
For product intake and conveying, screw elements are used. The extruder can be fed with powder, pellets, chips, melt, paste, etc.
Plasticizing, mixing and dispersing are done by the twin screw extruder kneading elements. By varying the thickness of the kneading disks and their angle of stagger, their mixing, shearing and dispersing action can be adjusted to the individual requirements.
The screw elements are arranged on screw shafts. The co-rotating and closely intermeshing screw shafts have a sealing profile.
The screw barrels are supported by barrel supports. Axial displacement of the processing section resulting from thermal dilatation is absorbed by these supports.
The discharge section of the twin screw extruder consists of die head and screen changer, which is installed at the end of twin screw extruder discharging direction. There are several types of die heads and screen changers to meet the requirements of different polymers and processing technology.
The single screw extruder is mainly used for extruding soft and hard polyvinyl chloride, polyethylene, and other thermoplastic. It can be a variety of plastic products such as bubble sheets, extruded pipes, press plates, ribbons, etc. process and can also be used for melting granulation. The plastic extruder is characterized by advanced design, high quality, good plasticization, and low energy consumption. It uses an evolutionary drive and is characterized by low noise development, stable operation, great durability, and long service life.
What are the relevant parameters of a single screw extruder?
What are the properties of a single screw extruder?
For which materials can a single screw extruder be used?
The relevant parameters of the insertion extruder are arranged from left to right: the first field is the plastic machine code as S; the second box is the extruder code as J; the third field is the code for the different construction firms of the extruder. The three bars are combined, the plastic extruder is SJ; the ventilated plastic extruder is SJP; the plastic foam extruder is SJF; the extruder with plastic input is SJW; the plastic shoe extruder is SJE; The cascade plastic extruder is SJJ; the double-screw extruder is SJS; the conical double-screw extruder is SJSF; the multi-screw extruder is SJD. The fourth box is for auxiliary machinery with the code name F; in the case of an extruder unit with the code name E. The fifth parameter refers to the snail diameter and the ratio of length to snail diameter. The sixth field refers to the product's pattern sequences, which in the order of letters A, B, C... is arranged and the sample number is not given in the first sample.
(1) The material support of the inlet extruder is mainly based on friction, which limits the conveyance performance of the inlet extruder. The addition of powder, paste, fiberglass, and inorganic fillers is difficult.
(2) If the head pressure of the inlet extruder is high, the counter current increases, which reduces the productivity of the inlet extruder.
(3) Injected exhaust gas extruder material has a low surface regeneration effect in the suction zone, so the suction effect of the inlet extruder is poor.
(4) Injection extruder is used for certain processes, such as polymer dyeing, heat-resistant powder processing, etc. not suitable. The single screw extruder is a high-speed and high-yield extrusion based on a high level.
single screw extruder series, single screw extruders can be used for the processing of PP, PE, PS, ABS, PMMA, PVC, and other thermoplastic tubes, plates, plates, rods, profile materials, and plastic granulation products. For different raw materials and product specifications, the screw assumes different length-diameter ratios and compression ratios, and the flow assumes different structures. Choose the right cylinder, screw, and drive mechanism to meet the processing requirements of high-quality products.
The use of single screw extruders is becoming increasingly widespread. Nanjing JlEYA has been concentrating on single screw extruders for several years. They will make every effort to meet the needs of users.
The structure of the engineering plastic twin screw extruder barrel is basically similar to that of the single-screw extruder screw barrel. From the appearance structure, the twin-screw extruder barrel is also divided into an integral barrel and a segmented barrel. The engineering plastic twin screw extruder is an upgrade of the single screw extruder, which has also greatly improved the efficiency of use.
What are the reasons why people choose engineering plastic twin screw extruder?
What is the workflow of engineering plastic twin screw extruder?
What are the essential devices in the engineering plastic twin screw extruder?
1. Improve labor efficiency
When the equipment is repaired, engineering plastic twin screw extruder only needs to loosen a few bolts, turn the worm gear box handle device to lift the upper part of the barrel to open the entire barrel, and then perform repairs. This not only shortens the maintenance time, but also reduces the labor intensity.
2. High torque and high speed
The development trend of engineering plastic twin screw extruder in the world is towards high torque, high speed, and low energy consumption. The effect of high speed is high productivity. engineering plastic twin screw extruder belongs to this category, and its speed can reach 500 rpm. Therefore, it has unique advantages in processing high-viscosity, heat-sensitive materials.
3. Wide range of applications
engineering plastic twin screw extruder has a wide range of applications and can be applied to the processing of a variety of materials
4. High output, high quality
engineering plastic twin screw extruder has other advantages of ordinary extruder, and can achieve high output, high quality and high efficiency.
The engineering plastic twin screw extruder used for profile extrusion is usually tightly meshed and rotated in different directions, although a few also use co-rotating twin screw extruders, generally operating at a relatively low screw speed, about 10 r/ min. The high-speed meshing co-rotating engineering plastic twin screw extruder is used for compounding, venting or as a continuous chemical reactor. The maximum screw speed of this type of extruder is 300-600r/min. Non-intermeshing extruder is used for mixing, venting and chemical reaction. Its conveying mechanism is quite different from intermeshing extruder, which is closer to the conveying mechanism of single screw extruder, although there are essential differences between the two.
Among the straightening devices used in engineering plastic twin screw extruder, the most common one is eccentric, and various types of bending of the core are one of the important reasons for the insulation eccentricity. In sheath extrusion, scratches on the sheath surface are often caused by the bending of the cable core. Therefore, the straightening device in various engineering plastic twin screw extruder is indispensable. The main types of straightening devices are: drum type (divided into horizontal and vertical); pulley type (divided into single pulley and pulley block); winch type, which has multiple functions such as dragging, straightening, and tension stabilization; Press wheel type (divided into horizontal type and vertical type), etc.
The engineering plastic twin screw extruders are used more and more widely in daily life, but its quality has a great influence on the experience of use. Nanjing JlEYA has focused on the production and development of engineering plastic twin screw extruders for more than several years, and they have always put the needs of customers as their top priority.
With the development of modern industry, the underwater pelletizing machine has become an important production equipment used in all aspects of production.
What is the working principle of the underwater pelletizing machine?
What is the operating procedure of the underwater pelletizing machine?
What are the reasons why people choose underwater pelletizing machine?
The material using the underwater pelletizing machine will pass through the feeding port, and under the action of the rotating screw, it will be rolled into a dough and roll forward along the screw groove. Due to the shear, compression and agitation of the screw, the material will be further mixed and plasticized. , The temperature and pressure gradually increase, showing a state of viscous flow, and passing through the machine head with a certain pressure and temperature, and finally a product of the desired shape is obtained.
(1) Check the rotation direction of the impeller of the underwater pelletizing machine. From the feed inlet, the impeller should turn counterclockwise, otherwise the motor connection should be adjusted.
(2) The starting sequence of the underwater pelletizing machine and the material conveying equipment is as follows:
Discharge belt conveyor→PL vertical impact crusher→feeding belt conveyor
The crusher must be started without load, and the material can only be fed after the crusher is running normally.
(3) The feed size is strictly in accordance with the feed size specified by the various models. It is forbidden to enter the underwater pelletizing machine with the size of the material larger than the specified size, otherwise it will cause the impeller imbalance and excessive wear of the impeller, and even block the impeller flow path and The central feed pipe prevents the crusher from working normally. When a large piece of material is found, it should be removed in time.
(4) When the discharge belt conveyor stops running, the feeding should be stopped immediately, so the discharge belt conveyor should be interlocked with the feeding system to open and stop. Otherwise, the impeller will be crushed and the motor will be burnt.
(5) The feeding of the underwater pelletizing machine should be uniform and continuous.
(6) During the operation of the underwater pelletizing machine, there must be no violent vibration or abnormal noise, otherwise, it should be stopped immediately for inspection, and the machine can only be driven in order after the fault is removed.
(7) The observation door should be sealed tightly during the working process of the underwater pelletizing machine.
The difference between the underwater pelletizing machine and other similar products is that it has a steady stream of water flowing through the mold surface, and it is in direct contact with the mold surface. The size of the pelletizing chamber is just enough to allow the pelletizing knife to rotate freely across the die surface without restricting the temperature of the water flow. The molten polymer has been extruded from the die, and the rotating knife cuts the pellets. And then the pellets are taken out of the pelletizing chamber by the temperature-regulated water and enter the centrifugal dryer. In the dryer of the underwater pelletizing machine, the water will be drained back to the storage tank, cooled and recycled; the pellets pass through the centrifugal dryer to remove the water.
This is how we see the irreplaceable role of underwater pelletizing machine in our daily lives and industrial production. Nanjing JlEYA, the pioneer of underwater pelletizing machine producing company in China, knows that every application is special. You can go and get more information about them
Degradable plastics refer to a class of plastics whose various properties can meet the requirements of use, remain unchanged during the shelf life, and can be degraded into environmentally harmless substances under natural environment conditions after use. Therefore, it is also called environmentally degradable plastic.
There are a variety of new plastics: photodegradable plastics, biodegradable plastics, light/oxidative/biodegradable plastics, carbon dioxide-based biodegradable plastics, thermoplastic starch resin degradable plastics.
There are two main areas for the use of degradable plastics: one is the area where ordinary plastics were originally used. In these areas, the difficulty of collecting used or post-consumer plastic products will cause harm to the environment, such as agricultural mulch and single-use plastic packaging, and the second is areas where plastics are used instead of other materials. The use of degradable plastics in these areas can bring convenience, such as ball tacks for golf courses, and seedling fixing materials for tropical rainforest afforestation.
Specific applications are:
1.Agriculture, forestry and fishery, plastic film, water-retaining materials, seedling pots, seedbeds, rope nets, slow-release materials for pesticides and agricultural fertilizers.
2.Packaging industry, shopping bags, garbage bags, compost bags, disposable lunch boxes, instant noodle bowls, buffer packaging materials.
3.Sporting goods, golf tacks and tees
4.Hygiene products, women's hygiene products, baby diapers, medical mattresses, disposable haircuts.
5.Medical materials, bandages, clips, small sticks for cotton swabs, gloves, drug release materials, and surgical sutures and fracture fixation materials.
Nanjing Jieya also manufactures twin screw compounding extruder for bio-degradable material. We warmly welcome your inquiry.
As common extruder equipment used in the plastic processing industry, single screw extruder is mainly used for extruding soft and hard PVC, polyethylene, and other thermoplastics, which can process many kinds of plastic products, such as blown film, extruded pipe, pressboard, drawn ribbon, etc. It can also be used for melt pelletizing. The plastic extruder has advanced design, high quality, good plasticization, low energy consumption, involute gear transmission, low noise, smooth operation, high load capacity, and long life. To have a long service life of the machine, maintenance measures are indispensable, the following is a detailed description of the single-screw extruder maintenance measures.
Here is the content list:
1. Because the electrical control system of single-screw extruder has high requirements for ambient temperature and dustproof, the electrical system should be separated from the production site, and install ventilation or ventilation fan, it is recommended that the electrical control cabinet in a simple room, keep the room clean, ventilation, so that the indoor temperature is not higher than 40 ℃.
2. Single-screw extruderis not allowed to run empty, so as not to roll the screw and machine simple hair. Host start idling is not allowed to exceed 100r / min; start the host first low speed, after starting the host to check for abnormal noises and then slowly increase the host speed to within the allowable range of the process (can be adjusted to the best state is good). When the new machine is breaking in, the current load should be at 60-70%, and the current in normal use should preferably not exceed 90%. Note: If an abnormal sound occurs when the extruder is running, it should be stopped immediately for inspection or repair.
3. Turn on the oil pump first and turn off the oil pump after shutting down the machine; keep the water pump working during the whole production process and do not stop the pump to avoid the barrel temperature rising and causing the material in the barrel to decompose and carbonize; the asbestos wind cover of the main motor fan needs to be cleaned often to avoid the dust sticking too much to block the wind cover and cause the motor to overheat and trip due to insufficient heat dissipation.
4. Clean up the dust and dirt, tools, and debris on the surface of the unit in time.
1.Regularly check the screws and other fasteners on the surface of the single-screw extruder unit for looseness and timely and proper tightening. The lubricant level of the transmission box should be added or replaced promptly (the dirt at the bottom of the oil tank should be cleaned regularly). For new machines generally, 3 months to replace the oil, after that every six months to a year. The oil filter and oil suction pipe should be cleaned regularly (once a month).
2. Single screw extruder gearbox maintenance and general standard reducer are the same. The main thing is to check the wear and failure of gears and bearings.
3, When reinstallation please note that A, B two screws must be in the original position, can not be replaced! After the installation of the new combination of the screw on the machine, you must first use the hand pan car, such as normal rotation before the low-speed start. Screw or barrel for a long time without use, there should be anti-rust and anti-fouling measures, the screw should be placed hanging. If the threaded block is with fire, the flame should be moved left and right, while burning to clean up, and can not burn too much (blue ringers red), not to mention the thread block into the water.
4. Regularly calibrate the temperature control instrument to check the correctness of its adjustment and the sensitivity of its control.
5. In the barrel with a cooling water tank, must be used distilled water to prevent the formation of scale blocking the cooling water channel in the barrel, resulting in temperature failure. Pay attention to the appropriate amount of water in use to prevent scaling. If the blockage should be changed down the cylinder specific maintenance, no blockage and the water output is small indicates that there is scale, the tank water should be changed to dilute hydrochloric acid swishing cycle, clear scale to normal and then change the distilled water. General water in the tank is used to cool the barrel, and the natural water we pass is used to cool the tank. Regularly check the water quality of the cooling water tank, if there is turbidity, should be replaced promptly.
6.Check whether the solenoid valve is working properly, the coil has not burned out if there is a timely replacement.
7. The temperature does not rise to quite the temperature continues to rise and fall may exist for the following reasons: whether the day electric couples loose fall; heater relay is working properly; solenoid valve is working properly, timely replacement of deformation of the heater, and tighten the screws.
8. Timely clean up the dirt in the vacuum tank, and the material in the exhaust chamber so that the pipeline is smooth. Vacuum pump seals need to be replaced promptly if there is wear and tear regular inspection, the output shaft jumping is bearing damage and shaft fracture must be opened and replaced, such as the gearbox two output shaft bearing position wear is too serious, the box must be replaced to avoid greater loss of failure.
9, To drive the screw rotation of the DC motor to focus on checking the brush wear and contact, the insulation resistance value of the motor whether in the specified value should also be measured frequently. In addition, check the connection line and other components that are rusted, and the use of protective measures.
10. When the single-screw extruder needs to stop using for a long time, should be in the screw, Jane, the head, and other working surfaces coated with anti-rust grease. The small screw should be suspended in the air or placed in a special wooden box, and a wooden block pad flat, so as not to deform the screw or bruise.
11. Single-screw extruder attached to the cooling water pipe wall is prone to scale external corrosion and rust. Maintenance should be carefully checked, too much scale will block the pipeline, can not achieve the cooling effect, rust will be serious leaks, so maintenance must take descaling and anti-corrosion cooling measures.
12. Designate a person responsible for the maintenance of equipment. And each maintenance and repair detailed record is included in the plant equipment management files.
If you still have questions, you can consult our company, we are happy to answer for you. The company insists on the purpose of "quality first, customer first", and warmly welcomes new and old customers to cooperate with us.
Twin-screw extruders have barrels with an extension range of 4 and 6D, allowing for precise process design to meet specific customer requirements. All barrels allow for precise temperature control. Cooling is achieved by cooling water injection and high-performance electric heating rods for direct and fast heating. The auxiliary equipment of the twin-screw extruder consists of a straightening device, a preheating device, and a cooling and heating device. The following is a detailed description of the auxiliary equipment.
Here is the content list:
l Straightening device
l Preheating device
l Cooling device
One of the most common types of plastic extrusion rejects is eccentricity, and bending of the wire core in various patterns is one of the most important causes of insulation eccentricity. In sheath extrusion, scratches on the sheath surface are also often caused by the bending of the cable core. Therefore, a variety of extrusion units in the straightening device is essential. The main types of straightening devices are roller type (divided into horizontal and vertical type); pulley type (divided into single pulley and pulley group); stranded pulley type, which plays a variety of roles such as dragging, straightening, and stabilizing tension; pressure pulley type (divided into horizontal and vertical type), etc.
Cable core preheating is necessary for both insulation extrusion and sheath extrusion. For the insulation layer, especially the thin layer of insulation, the existence of pores should not be allowed, the core can be completely removed from the surface of the water, oil, and dirt through high temperature preheating before extrusion. For the sheath extrusion, the main role is to dry the cable core, to prevent the role of moisture (or moisture around the bedding layer) to make the sheath in the possibility of porosity. Preheating can also prevent the plastic from being extruded due to sudden cooling and residual internal pressure. In the process of extruding plastic, preheating can eliminate the cold line into the high-temperature heat, in contact with the plastic at the mouth of the die to form a disparity in temperature, to avoid fluctuations in plastic temperature and lead to fluctuations in extrusion pressure, to stabilize the amount of extrusion and ensure the quality of extrusion. Extrusion unit is used in the electric heating core preheating device, requires sufficient capacity, and ensures rapid temperature rise, so that the core preheating and cable core drying efficiency. The preheating temperature is restricted by the speed of wire release, generally similar to the temperature of the head.
The formed plastic extrusion layer after leaving the head should be immediately cooled and shaped, otherwise, deformation will occur under the action of gravity. The way of cooling usually uses water cooling, and according to the water temperature is different, divided into rapid cooling and slow cooling. Rapid cooling is the direct cooling of cold water, rapid cooling of plastic extrusion layer sizing is beneficial, but for crystalline polymers, due to sudden heat cooling, easy to internal residual stress in the extrusion layer organization, resulting in the use of the process of cracking, general PVC plastic layer using rapid cooling. Slow cooling is to reduce the internal stress of the product, in the cooling water tank placed in sections of different temperatures of water, so that the product gradually cool down and set, PE, PP extrusion on the use of slow cooling, that is, after hot water, warm water, cold water three cooling.
If you are engaged in a twin-screw extruder-related industry, you can consider our cost-effective products.