A twin screw extruder is composed of several parts such as a transmission device, feeding device, barrel, and screw, etc. The role of each part is similar to that of the single screw extruder. So what are the main differences between the twin screw extruder and single screw extruder? The following is the detailed introduction
Here is the content list:
l Cross sectional profile
l The way of material transfer
l The material flow velocity field
The difference from the single screw extruder is that the twin screw extruder has two parallel screws in an "∞" shaped cross section. Twin screw extruders for profile extrusion are usually closely meshed and heterogeneously rotating, although a few also use co rotating twin screw extruders, which generally operate at relatively low screw speeds of about 10 r/min. High speed meshing co rotating twin screw extruders are used for blending, venting, or as continuous chemical reactors, with maximum screw speeds ranging from 300 600 r/min. Non engaging extruders are used for mixing, venting, and chemical reactions, and their conveyors are very different from those of engaging extruders, and are closer to those of single screw extruders, although they are fundamentally different.
In the single screw extruder, the solid conveying section is friction dragging and the melt conveying section is viscous dragging. The frictional properties of solid materials and the viscosity of molten materials determine the conveying behavior. If some materials have poor frictional properties, it is more difficult to transfer the material to the single screw extruder if the feeding problem is not solved. In twin screw extruders, especially meshing twin screw extruders, the material transfer is to some extent a positive displacement transfer, the degree of positive displacement depending on the proximity of the screw prongs of one screw to the relative screw grooves of the other screw. The screw geometry of a closely meshed anisotropic rotary extruder yields a high degree of positive displacement transport characteristics.
The flow velocity distribution of the material in a single screw extruder has been described fairly well, whereas the flow velocity distribution of the material in a twin screw extruder is quite complex and difficult to describe. Many researchers have analyzed the velocity field of the material without considering the material flow in the engagement zone, but the results of these analyses are very different from the actual situation. This is because the mixing characteristics and overall behavior of a twin screw extruder depend mainly on the leakage flow that occurs in the engagement zone, yet the flow in the engagement zone is quite complex. The complex flow spectrum of the material in a twin screw extruder exhibits macroscopic advantages that cannot be matched by a single screw extruder, such as adequate mixing, good heat transfer, high melting capacity, good venting capacity, and good control of the material temperature.
If you want to know more, you can consult our company. Nanjing JlEYA is the leading manufacturer extruder manufacturer specializing in a twin screw extruder, mini twin screw extruder, plastic extruder, and parallel twin screw extruder in China, which is widely used in compounding, modification, polymerization, devolatilization, reaction, recycling, etc. After 17 years of development, now we have a 20,000 square meters workshop with annual sales of over 300+ sets, export over 60 countries.
JIEYA has the most experienced technical core team, with extensive experience in system integration of the development manufacturing, materials processing, application technology, and other fields.
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.
Nanjing Jieya is a professional manufacturer of twin screw compounding extruders since 2004. Our extruders series include SHJ series, HT series, JY series, SJ series, etc. Today we will tell you the differences between SHJ series twin screw extruders and HT series high torque twin screw extruders from three main points below:
1. Torque grade
The torque rating grade of our SHJ series twin screw extruder is T/A3≤8 while HT series is 9≤T/A3≤13.5. Our HT series adopt high torque gear box, which is suitable for customers that pursuit high efficiency machines.
2. Power transmission
SHJ series use clutch for power transmission while HT series use torque protector, for example, R+W brand, Bibby brand, etc.
The output of HT series twin screw extruder is much higher than SHJ series.
So HT series can further improve the performance of extruders.But surely, price is higher than SHJ series.
The main system of the plastic extruder is the extrusion system, which includes screw, barrel, hopper, head, and die. The plastic is plasticized into a uniform melt by the extrusion system and is continuously extruded from the head by the screw under the pressure established in the process. The following are details about the plastic extruder extrusion system introduction.
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Head and mold.
The screw is the most important part of the extruder, which is directly related to the application range and productivity of the extruder and is made of high-strength and corrosion-resistant alloy steel.
The barrel is a metal cylinder, generally made of heat-resistant, high-pressure strength, strong wear-resistant, corrosion-resistant alloy steel or composite steel tube lined with alloy steel. The barrel and the screw cooperate to realize the crushing, softening, melting, plasticizing, exhausting, and compacting of the plastic, and to continuously and evenly deliver the rubber to the molding system. Generally, the length of the barrel is 15-30 times its diameter, so that the plastic is fully heated and fully plasticized as a principle.
The bottom of the hopper is equipped with a cut-off device to adjust and cut off the material flow, and the side of the hopper is equipped with a sight hole and a calibrated measuring device.
The head is composed of alloy steel inner sleeve and carbon steel outer sleeve, the head is equipped with a molding mold, the role of the head is to transform the rotational movement of the plastic melt into a parallel linear motion, evenly and smoothly into the mold sleeve, and give the plastic to the necessary molding pressure. The plastic is plasticized and compacted in the barrel and flows through the neck of the head through a certain flow path through the porous filter plate into the forming mold of the head. The mold core and mold sleeve are properly matched to form an annular gap with decreasing cross-section so that the plastic melt forms a continuous dense tubular cladding layer around the core line. To ensure that the plastic flow channel in the head is reasonable and to eliminate the dead angle of the accumulated plastic, there is often a diversion sleeve placed, and to eliminate the pressure fluctuation of plastic extrusion, there is also a pressure equalization ring set. The head is also equipped with a die correction and adjustment device to facilitate the adjustment and correction of the concentricity of the die core and die sleeve.
The extruder head is divided into an angled head (120o angle) and a right angle head according to the angle between the head material flow direction and the screw centerline. The shell of the head is fixed to the body with bolts, the die inside the head has a die core sitting and is fixed to the head inlet port with a nut, the front of the die core seat is equipped with a die core, the die core and the center of the die core seat has a hole for passing the core line, the front of the head is equipped with an even pressure ring for equalizing the pressure, the extrusion package forming part is composed of die sleeve seat and die sleeve, the position of the die sleeve can be adjusted by bolts through the support to adjust the die sleeve to the die core The position of the die sleeve can be adjusted by bolts through support to adjust the relative position of the die sleeve to the die core, which is convenient to adjust the uniformity of the thickness of the extruded layer.
If you want to buy a plastic extruder or want to know more, you can visit our official website. Our website is https://www.njjyextrusion.com/
Nanjing Team sincerely invite you to attend The 15th China Chongqing Rubber, Plastics Industry Exhibition.
Our booth no.: S2544
Time: May 27-30, 2021
Address: Chongqing International Expo Center
Wish to meet you at there ;)
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.
The main machine of the plastic extruder is the extruder, which is composed of an extrusion system, transmission system, and heating and cooling system. The following is a detailed description of the composition of the plastic extruder.
Here is the content list:
Heating and cooling device
A homogeneous melt is plasticized bypassing the plastic through the extrusion system, which consists of a screw, barrel, hopper, head, and die.
The function of the drive system is to drive the screw, supplying the torque and speed required by the screw during the extrusion process, usually consisting of an electric motor, reducer, and bearings.
The manufacturing cost of the reducer is roughly proportional to its size and weight, provided that the structure is the same. Because the shape and weight of the reducer are large, it means that more materials are consumed in the manufacturing, and the bearings used are also larger, which increases the manufacturing cost.
For a similar screw diameter extruder, the high speed and high potency extruder consume additional energy than the traditional extruder, the motor power is doubled, and also the reducer seat range is raised consequently is critical，however a high screw speed means that an occasional reduction magnitude relation. For the same size reducer, the gear modulus of the low reduction ratio increases compared to the large reduction ratio, and the capacity of the reducer to bear the load also increases. Therefore, the rise in volume and weight of the reducer isn't linearly proportional to the rise in motor power. If the extrusion volume is employed because of the divisor and dividend by the burden of the reducer, the high speed and high potency extruder can have a smaller range and the normal extruder will have a larger number.
In terms of unit output, the small motor power and the small weight of the reducer of the high speed and high-efficiency extruder means that the manufacturing cost per unit output of the high speed and high-efficiency extruder is lower than that of the normal extruder.
Heating and cooling are necessary to enable the plastic extrusion process to proceed.
(1) Extruders usually use electric heating, which is divided into resistance heating and induction heating, with heating sheets installed in each part of the body, neck, and head. The heating device heats the plastic inside the barrel from the outside to warm it up to the temperature required for the process operation.
(2) The cooling device is installed to ensure that the plastic is in the temperature range required for the process. Specifically, it is to exclude the excess heat generated by the shear friction of the rotating screw to avoid the plastic from decomposing, scorching, or shaping difficulties due to the high temperature. Barrel cooling is divided into two kinds of water-cooled and air-cooled, generally small and medium-sized extrusion machine using air-cooled is more appropriate, large is more water-cooled or a combination of two forms of cooling; screw cooling is mainly used in the center of water-cooled, the purpose is to increase the rate of solid material delivery, stabilize the amount of rubber, while improving product quality; but the cooling at the hopper, one is to strengthen the role of solid material delivery, to prevent the plastic grain sticky blockage because of the heating the second is to ensure the normal work of the transmission part.
If you are engaged in the industry related to the extruder, you can consider our cost-effective products. Our company is a leading extruder manufacturer specializing in a twin-screw extruder, micro twin-screw extruder, plastic extruder, and parallel twin-screw extruder in China.