1.Plastic Machinery principle
Extrusion of the basic mechanism is simple – a screw in the cylinder rotation and put the plastic to move forward. The screw is actually a ramp or slope, is wound on the center layer. Its purpose is to increase the pressure in order to overcome the large resistance. One extruder, there are three kinds of resistance to be overcome: the solid particles (feed) of the friction and the screw on the wall of the cylinder to rotate the front laps (feed zone) the mutual friction between them; melt melt is pushed forward when the internal logistics in the adhesion of the cylinder wall; resistance.
Newton had explained that if an object is not a given direction, the force on the object balanced in this direction. Screw, not axial movement, although in around the circumference, it may be horizontal rapid rotation. Accordingly, the axial force on the screw is balanced, but if it is a large forward thrust is applied to the plastic melt it also is applied to an object of a same rearward thrust. Here, it exerts a thrust acting on the feed port behind the bearings – thrust bearings.
The majority of single screw is a right-hand thread, like woodworking and machine screw and bolt. From behind, they are reverse rotation, because they want to try to backward spin the cylinder. In a twin screw extruder, two screws in the two cylinder reverse rotated and cross each other, so one must be the right direction, the other must be the left direction. In other occlusal twin screw, two screws rotate in the same direction and therefore must have the same orientation. However, in either case have absorbed back thrust bearings, Newton’s principle still applies.
2. Thermal principle
The extruded plastic is a thermal plastic – they melt when heated and solidified again when cooled. The heat of the molten plastic come from? Feed preheating and barrel / mold heater may play a role very important in the startup However, the motor input energy – motor to overcome the frictional heat the viscous melt the resistance generated when the rotation of the screw cylinder body – all except plastic is the most important heat source system, low-speed screw, high melt temperature plastic extrusion coating applications.
For all other operations, it is important to recognize that the main heat source the cylinder heater is not operating in, thus extrusion role may be smaller than we expected (see Principle 11). After the cylinder temperature is likely to remain important because it affects the engagement or the feed solids conveying speed. The die and mold temperatures should typically be the desired temperature of the melt or close to this temperature, unless they are used for a specific purpose such as glazing, the fluid distribution or pressure control.
3. Deceleration principle
In most extruder screw speed changes are achieved by adjusting the motor speed. Motors are usually about 1750rpm at full speed rotation, but this is too fast for an extruder screw. If such a fast rotation, will generate too much heat of friction and plastic residence time is too short and not the preparation of a homogeneous, well-stirred melt. Typical reduction ratio between 10:1 to 20:1. The first stage can also be gear pulley block, but the second stage gear and the screw is positioned in the last of a large gear center.
Slow running machine (such as for UPVC double screw), there may be three deceleration phase and the maximum speed may be as low as 30rpm or less (ratio of 60:1). The other extreme, for stirring long twin-screw at 600rpm or faster speed run, and therefore requires a very low rate of deceleration, as well as a lot of deep cooling.
Sometimes deceleration rate mission match – there will be too much energy can not be used – and there are likely to increase in the first deceleration phase between the motor and change the maximum speed a pulley block. Either the screw speed was increased to more than the previous limit or allow the system to reduce the maximum speed to a greater percentage of the maximum speed run. This will increase the availability of energy, to reduce the amperage and avoid motor problems. In both cases, according to the material and its cooling needs, the output may increase.
4. Play coolant feed.
Extrusion is the energy of the motor – sometimes the heater – and deliver them to the cold plastic, and convert it from a solid to a melt. Input feed ratio to the feed zone in the barrel and the screw surface temperature is low. However, the feed zone of the cylinder surface is almost always in the plastic above the melting range. It cooled particles into contact with the feed, but the heat transfer of heat by the heat front rearwardly, and can control the heating maintained. Even end heat by viscous friction to maintain and does not require the cylinder heat input, may need to open the rear heater. The most important exception is a slot into the barrel, almost exclusively of HDPE.
The root surface of the screw is also feed cooling by the plastic feed particles (and the air between the particles) from the cylindrical wall of the adiabatic. If the screw is suddenly stopped, the feed is stopped, and because the heat is moved rearwardly from the front end of the hotter surface of the screw in the feed zone, becomes hotter. This may cause the adhesion of the particles in the roots or bypass.
5 in the feed region, adhered to the cylinder slid on the screw
In order to make a single-screw smooth cylinder of the extruder feed zone of the solid particle transport reaches its maximum, the particles should be glued to the barrel and slide screw. If the particles stick to the screw root, nothing can pull them down; channel volume and the amount of the entrance of the solid is reduced. In the roots adhered bad Another reason is that plastic may here thermal refining and produce gels and similar pollution particles, or with changes in the output speed of the intermittent adhesion, and interrupt.
Most plastics, it is natural to slide in the roots, because their access is cold, but friction is not the roots was heated to as hot and the tube wall. Some materials are more likely than others materials adhesion: highly plasticized PVC, amorphous PET and some end use, the desired adhesion properties of the polyolefin class of polymer.
For the cylinder, the plastic is necessary to adhere to so that it is scraped off and the screw threads to move forward. Between the particles and the cylinder should have a high coefficient of friction, and the coefficient of friction, in turn, is also affected by the strong influence of the rear barrel temperature. If the particles do not adhere to, they are simply place rotate without forward movement – which is why a smooth feed bad reasons.
Surface friction is not the only factor affecting feed. Many particles are never in contact with the cylinder or screw root, there must be a chain of friction and mechanical and viscosity inside the particles.
With grooved drum body is a special case. The groove in the feed zone, the remainder of the feed zone with the cylinder portion is thermally insulated and the depth of water cooled. Threaded the particles are pushed into the groove and a high pressure is formed within a relatively short distance. This increases the lower the screw speed of the same output nip grant, thereby reducing the front end of the frictional heat generated, and a lower melt temperature. This may mean cooling constraints blown film production line faster production. The slot is particularly suitable for HDPE, which is in addition to fluorinated plastics slip ordinary plastic.
6.pvc banner flex machine most expensive
In some cases, the material costs can account for 80% of the cost of production – more than all other factors and – particularly important in addition to a small number of quality and packaging products, such as medical catheter. This principle naturally leads to two conclusions: the processors should be reused as much as possible of scrap and waste products instead of raw materials and to adhere as strictly as possible tolerance so as not to deviate from the target thickness and product problems.
Energy costs are relatively unimportant
Despite the attractiveness of a factory and the real problem and rising energy costs at the same level, the energy required to run a single extruder is still a small part of the total production cost. Always the case because of the very high cost of materials, the extruder is an effective system, the introduction of too much energy, the plastic will soon become very hot, so that can not be properly processed.
Screw the pressure at the end of a very important
This pressure reflects the the screw the downstream all objects resistance: filter pollution tie broken board, duct adapter, the fixed agitator (if any) as well as the mold itself. It is not only dependent on the geometry of these components is also dependent on the temperature in the system, which in turn affects the viscosity of the resin and by the speed. It does not rely on the screw design, except when it affects the temperature, viscosity and throughput. For security reasons, the measurement temperature is very important – if it is too high, the die and mold may explode and cause injury to personnel or machinery in the vicinity.
The pressure is advantageous for mixing a single screw system, particularly in the final zone (metering zone). However, the high pressure means that the motor output more energy – and thus a higher melt temperature – which can be specified pressure limit. In a twin screw, two screws mutually engaging to be a more efficient stirrer, so when used for this purpose does not require pressure.
Use in the manufacture of hollow parts, such as the stent tube core positioning spider mold manufacturing, must be in the high pressure inside the mold to help separate logistics regroup. Otherwise, along the welding line of products may be weak and the problems that may occur during use.
Output = last thread displacement + / – pressure logistics and leak
The last displacement of the threaded called positive flow, only dependent on the screw geometry, screw speed and the melt density. It is adjusted by the pressure stream, in fact, include reduce the output effect of the amount of resistance (expressed by the maximum pressure) and to increase the output amount of the feed to any excessive occlusion effect. Threaded on the leak may be in any one direction of the two directions.
Calculated for each rpm (rpm) of the output is also useful, because this means that any fall of the screw pump in a time-out capability. Another related calculations are used per horsepower or kilowatt output. This means that the efficiency and to be able to estimate the production capacity of a given motor and drive.
10. Shear rate play a major role in the viscosity
1pvc pipe machine has a shear drop characteristics, meaning low viscosity plastic moving faster and faster. Some of the plastic of the effect that was particularly evident. For example, some PVCs thrust doubling flow rate will increase by 10 times or more. Instead, LLDPE shear drop is not too much, reasoning doubling its flow rate only increased by 3-4 times. Reducing the shear effect of reducing the mean extrusion under the conditions of high viscosity, which in turn means more motor power. This may explain why LLDPE run a higher temperature than LDPE. Flow to the shear rate expressed in the screw channel is approximately 100s-1, the in most mold mouth is between 100 and 100s-1, 100s-1 is in the thread and the cylinder wall gap and a number of small die gap is greater than . Melt coefficient is a common method of measurement of the viscosity but it is upside down (such as flow / thrust instead of thrust / flow). Unfortunately, the measurement is the shear rate at 10s-1 or more hours in the melt flow rate quickly extruder may not be a true measured value.
11. Motor cylinder opposition, cylinder and motor opposition
Why the control effect of the cylinder is not always desired, especially in the measurement zone? If the heating of the cylinder, the viscosity of the material layer of the cylinder wall at the smaller, less motor energy needed for the operation of the smoother cylinder body. The decline in motor current (amperage). Conversely, if the cylinder cooling, the tubular wall at the melt viscosity is increased, the motor must be harder to rotate, the amperage increased, to remove some of the heat when the cylinder is returned by the motor. Typically, the regulator of the cylinder does have an effect on the melt, which is what we expect, but anywhere in the effect of regional variables are not. It is best to measure the melt temperature to truly understand what is happening.
Principle 11 does not apply to die and die, because there is no screw rotation. This is why the external temperature variation where more effective. However, these changes are uneven and thus from the inside to the outside, unless a fixed stirrer, stir, melt temperature changes and agitation are an effective tool.
Extrusion of the basic mechanism is simple – a screw in the cylinder rotation and put the plastic to move forward. The screw is actually a ramp or slope, is wound on the center layer. Its purpose is to increase the pressure in order to overcome the large resistance. One extruder, there are three kinds of resistance to be overcome: the solid particles (feed) of the friction and the screw on the wall of the cylinder to rotate the front laps (feed zone) the mutual friction between them; melt melt is pushed forward when the internal logistics in the adhesion of the cylinder wall; resistance.
Newton had explained that if an object is not a given direction, the force on the object balanced in this direction. Screw, not axial movement, although in around the circumference, it may be horizontal rapid rotation. Accordingly, the axial force on the screw is balanced, but if it is a large forward thrust is applied to the plastic melt it also is applied to an object of a same rearward thrust. Here, it exerts a thrust acting on the feed port behind the bearings – thrust bearings.
The majority of single screw is a right-hand thread, like woodworking and machine screw and bolt. From behind, they are reverse rotation, because they want to try to backward spin the cylinder. In a twin screw extruder, two screws in the two cylinder reverse rotated and cross each other, so one must be the right direction, the other must be the left direction. In other occlusal twin screw, two screws rotate in the same direction and therefore must have the same orientation. However, in either case have absorbed back thrust bearings, Newton’s principle still applies.
2. Thermal principle
The extruded plastic is a thermal plastic – they melt when heated and solidified again when cooled. The heat of the molten plastic come from? Feed preheating and barrel / mold heater may play a role very important in the startup However, the motor input energy – motor to overcome the frictional heat the viscous melt the resistance generated when the rotation of the screw cylinder body – all except plastic is the most important heat source system, low-speed screw, high melt temperature plastic extrusion coating applications.
For all other operations, it is important to recognize that the main heat source the cylinder heater is not operating in, thus extrusion role may be smaller than we expected (see Principle 11). After the cylinder temperature is likely to remain important because it affects the engagement or the feed solids conveying speed. The die and mold temperatures should typically be the desired temperature of the melt or close to this temperature, unless they are used for a specific purpose such as glazing, the fluid distribution or pressure control.
3. Deceleration principle
In most extruder screw speed changes are achieved by adjusting the motor speed. Motors are usually about 1750rpm at full speed rotation, but this is too fast for an extruder screw. If such a fast rotation, will generate too much heat of friction and plastic residence time is too short and not the preparation of a homogeneous, well-stirred melt. Typical reduction ratio between 10:1 to 20:1. The first stage can also be gear pulley block, but the second stage gear and the screw is positioned in the last of a large gear center.
Slow running machine (such as for UPVC double screw), there may be three deceleration phase and the maximum speed may be as low as 30rpm or less (ratio of 60:1). The other extreme, for stirring long twin-screw at 600rpm or faster speed run, and therefore requires a very low rate of deceleration, as well as a lot of deep cooling.
Sometimes deceleration rate mission match – there will be too much energy can not be used – and there are likely to increase in the first deceleration phase between the motor and change the maximum speed a pulley block. Either the screw speed was increased to more than the previous limit or allow the system to reduce the maximum speed to a greater percentage of the maximum speed run. This will increase the availability of energy, to reduce the amperage and avoid motor problems. In both cases, according to the material and its cooling needs, the output may increase.
4. Play coolant feed.
Extrusion is the energy of the motor – sometimes the heater – and deliver them to the cold plastic, and convert it from a solid to a melt. Input feed ratio to the feed zone in the barrel and the screw surface temperature is low. However, the feed zone of the cylinder surface is almost always in the plastic above the melting range. It cooled particles into contact with the feed, but the heat transfer of heat by the heat front rearwardly, and can control the heating maintained. Even end heat by viscous friction to maintain and does not require the cylinder heat input, may need to open the rear heater. The most important exception is a slot into the barrel, almost exclusively of HDPE.
The root surface of the screw is also feed cooling by the plastic feed particles (and the air between the particles) from the cylindrical wall of the adiabatic. If the screw is suddenly stopped, the feed is stopped, and because the heat is moved rearwardly from the front end of the hotter surface of the screw in the feed zone, becomes hotter. This may cause the adhesion of the particles in the roots or bypass.
5 in the feed region, adhered to the cylinder slid on the screw
In order to make a single-screw smooth cylinder of the extruder feed zone of the solid particle transport reaches its maximum, the particles should be glued to the barrel and slide screw. If the particles stick to the screw root, nothing can pull them down; channel volume and the amount of the entrance of the solid is reduced. In the roots adhered bad Another reason is that plastic may here thermal refining and produce gels and similar pollution particles, or with changes in the output speed of the intermittent adhesion, and interrupt.
Most plastics, it is natural to slide in the roots, because their access is cold, but friction is not the roots was heated to as hot and the tube wall. Some materials are more likely than others materials adhesion: highly plasticized PVC, amorphous PET and some end use, the desired adhesion properties of the polyolefin class of polymer.
For the cylinder, the plastic is necessary to adhere to so that it is scraped off and the screw threads to move forward. Between the particles and the cylinder should have a high coefficient of friction, and the coefficient of friction, in turn, is also affected by the strong influence of the rear barrel temperature. If the particles do not adhere to, they are simply place rotate without forward movement – which is why a smooth feed bad reasons.
Surface friction is not the only factor affecting feed. Many particles are never in contact with the cylinder or screw root, there must be a chain of friction and mechanical and viscosity inside the particles.
With grooved drum body is a special case. The groove in the feed zone, the remainder of the feed zone with the cylinder portion is thermally insulated and the depth of water cooled. Threaded the particles are pushed into the groove and a high pressure is formed within a relatively short distance. This increases the lower the screw speed of the same output nip grant, thereby reducing the front end of the frictional heat generated, and a lower melt temperature. This may mean cooling constraints blown film production line faster production. The slot is particularly suitable for HDPE, which is in addition to fluorinated plastics slip ordinary plastic.
6.pvc banner flex machine most expensive
In some cases, the material costs can account for 80% of the cost of production – more than all other factors and – particularly important in addition to a small number of quality and packaging products, such as medical catheter. This principle naturally leads to two conclusions: the processors should be reused as much as possible of scrap and waste products instead of raw materials and to adhere as strictly as possible tolerance so as not to deviate from the target thickness and product problems.
Energy costs are relatively unimportant
Despite the attractiveness of a factory and the real problem and rising energy costs at the same level, the energy required to run a single extruder is still a small part of the total production cost. Always the case because of the very high cost of materials, the extruder is an effective system, the introduction of too much energy, the plastic will soon become very hot, so that can not be properly processed.
Screw the pressure at the end of a very important
This pressure reflects the the screw the downstream all objects resistance: filter pollution tie broken board, duct adapter, the fixed agitator (if any) as well as the mold itself. It is not only dependent on the geometry of these components is also dependent on the temperature in the system, which in turn affects the viscosity of the resin and by the speed. It does not rely on the screw design, except when it affects the temperature, viscosity and throughput. For security reasons, the measurement temperature is very important – if it is too high, the die and mold may explode and cause injury to personnel or machinery in the vicinity.
The pressure is advantageous for mixing a single screw system, particularly in the final zone (metering zone). However, the high pressure means that the motor output more energy – and thus a higher melt temperature – which can be specified pressure limit. In a twin screw, two screws mutually engaging to be a more efficient stirrer, so when used for this purpose does not require pressure.
Use in the manufacture of hollow parts, such as the stent tube core positioning spider mold manufacturing, must be in the high pressure inside the mold to help separate logistics regroup. Otherwise, along the welding line of products may be weak and the problems that may occur during use.
Output = last thread displacement + / – pressure logistics and leak
The last displacement of the threaded called positive flow, only dependent on the screw geometry, screw speed and the melt density. It is adjusted by the pressure stream, in fact, include reduce the output effect of the amount of resistance (expressed by the maximum pressure) and to increase the output amount of the feed to any excessive occlusion effect. Threaded on the leak may be in any one direction of the two directions.
Calculated for each rpm (rpm) of the output is also useful, because this means that any fall of the screw pump in a time-out capability. Another related calculations are used per horsepower or kilowatt output. This means that the efficiency and to be able to estimate the production capacity of a given motor and drive.
10. Shear rate play a major role in the viscosity
1pvc pipe machine has a shear drop characteristics, meaning low viscosity plastic moving faster and faster. Some of the plastic of the effect that was particularly evident. For example, some PVCs thrust doubling flow rate will increase by 10 times or more. Instead, LLDPE shear drop is not too much, reasoning doubling its flow rate only increased by 3-4 times. Reducing the shear effect of reducing the mean extrusion under the conditions of high viscosity, which in turn means more motor power. This may explain why LLDPE run a higher temperature than LDPE. Flow to the shear rate expressed in the screw channel is approximately 100s-1, the in most mold mouth is between 100 and 100s-1, 100s-1 is in the thread and the cylinder wall gap and a number of small die gap is greater than . Melt coefficient is a common method of measurement of the viscosity but it is upside down (such as flow / thrust instead of thrust / flow). Unfortunately, the measurement is the shear rate at 10s-1 or more hours in the melt flow rate quickly extruder may not be a true measured value.
11. Motor cylinder opposition, cylinder and motor opposition
Why the control effect of the cylinder is not always desired, especially in the measurement zone? If the heating of the cylinder, the viscosity of the material layer of the cylinder wall at the smaller, less motor energy needed for the operation of the smoother cylinder body. The decline in motor current (amperage). Conversely, if the cylinder cooling, the tubular wall at the melt viscosity is increased, the motor must be harder to rotate, the amperage increased, to remove some of the heat when the cylinder is returned by the motor. Typically, the regulator of the cylinder does have an effect on the melt, which is what we expect, but anywhere in the effect of regional variables are not. It is best to measure the melt temperature to truly understand what is happening.
Principle 11 does not apply to die and die, because there is no screw rotation. This is why the external temperature variation where more effective. However, these changes are uneven and thus from the inside to the outside, unless a fixed stirrer, stir, melt temperature changes and agitation are an effective tool.
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