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The correct and reasonable use of the extruder can fully utilize its efficiency,maintain good working condition,and extend the service life of the machine.
The use of screw extruder includes a series of processes such as installation,adjustment,trial operation,operation,maintenance,and repair.Its use has commonalities with general machines,mainly manifested in the driving motor and speed reduction device.However,the working system of the screw extruder,namely the extrusion system,has its own characteristics,and special attention should be paid to its characteristics when using the screw extruder.
The installation,adjustment,and testing of the machine are generally clearly specified in the user manual of the extruder.Here,the operating methods of the extruder are briefly described as follows:
The operator must be familiar with the structural characteristics of the extruder they are operating,especially to correctly grasp the structural characteristics of the screw,the control instrument characteristics of heating and cooling,the characteristics of the machine head,and the assembly situation,in order to correctly grasp the extrusion process conditions and operate the machine correctly.
The operation methods for extruding different plastic products are different,but there are also similarities.Below is a brief introduction to the same operating steps and precautions when extruding various products.
1.Preparation work before
(1)Plastic used for extrusion molding.The raw materials should meet the required drying requirements,and further drying is necessary if necessary.And sieve the raw materials to remove clumps and mechanical impurities.
(2)Check whether the water,electricity,and gas systems in the equipment are normal,ensure that the water and gas circuits are unobstructed and leak free,whether the electrical system is normal,and whether the heating system,temperature control,and various instruments are working reliably;Low speed trial run of the auxiliary machine,observe whether the equipment is running normally;Start the vacuum pump on the molding table and observe if it is working properly;Apply lubricating oil to the lubrication areas of various equipment.If any faults are found,they should be promptly resolved.
(3)Install the machine head and set the sleeve.Choose the appropriate head specifications based on the variety and size of the product.Install the machine head in the following order.
①The machine head should be assembled together and installed as a whole on the extruder.
②Before assembling the machine head,the grease applied during storage should be wiped off,and the surface of the mold cavity should be carefully checked for scratches,scratches,and rust spots.Necessary polishing should be carried out,and then a layer of silicone oil should be applied to the surface of the flow channel.
③Assemble the various plates of the machine head in sequence,apply high-temperature grease to the threads of the bolts,and then tighten the bolts and flange.
④Place the porous plate between the machine head flanges to ensure that it is tightly pressed without overflowing.
⑤Before tightening the fastening bolts of the connecting flange between the machine head and the extruder,the horizontal position of the mouth mold should be adjusted.The square machine head can be adjusted horizontally,while the circular machine head should be leveled with the bottom surface of the mouth mold based on the fixed model adhesive surface.
⑥Tighten the connecting flange bolts,tighten the machine head fastening bolts,install the heating ring and thermocouple,and ensure that the heating ring is tightly attached to the outer surface of the machine head.
⑦Install the set sleeve and adjust it in place,check if the center line of the main engine,set sleeve and traction machine is aligned.After adjustment,tighten the fixing bolts.Connect the water pipes and vacuum pipes of the fixed sleeve.
⑧Turn on the heating power and evenly heat up the machine head and casing.Simultaneously open the inlet valves of the cooling water and exhaust vacuum pump at the bottom of the feeding hopper and the gearbox.When heating up,adjust the temperature of each section to 140℃first.When the temperature rises to 140℃,keep it warm for 30-40 minutes,and then raise the temperature to the normal production temperature.When the temperature rises to the required temperature for normal production,maintain it for about 10 minutes to stabilize the temperature of various parts of the machine before starting production.The length of insulation time varies depending on different models of extruders and types of plastic materials.Keep it warm for a period of time to ensure that the temperature inside and outside the machine is consistent,in order to avoid the instrument indicating that the temperature has reached the required temperature but the actual temperature is too low.If the material is put into the extruder at this time,due to the actual temperature being too low and the melting viscosity of the material being too high,it will cause axial force overload and damage the machine.
⑨Feed the raw materials used for startup into the hopper for future use.
2.Power on
(1)After the constant temperature,the machine can be started up.Before starting up,the machine head and the flange bolts should be tightened again to eliminate the difference in thermal expansion between the bolts and the machine head.The sequence of tightening the machine head bolts is diagonal tightening,and the force should be even.When tightening the flange nut of the machine head,it is required that the tightness is consistent all around,otherwise material may run out.
(2)Turn on the machine,select the"Ready to Start"button,then connect the"Start"button,and slowly rotate the screw speed adjustment knob to start the screw speed slowly.Then gradually increase the speed while adding a small amount of material.When adding materials,close attention should be paid to the changes in the indication of the host ammeter and various indicator heads.The screw torque should not exceed the red mark(usually 65%-75%on the torque table).Before the plastic profile is extruded,no one is allowed to stand in front of the mouth mold to prevent injury accidents caused by bolt breakage or wet foaming of raw materials.After the plastic is extruded from the head mold,it is necessary to slowly cool the extruded material and guide it onto the traction device and shaping mold,and start these devices.Then,based on the indicated values of the control instrument and the requirements for the extruded product.Adjust each part accordingly to ensure that the entire extrusion operation reaches a normal state.And add enough materials as needed,the twin-screw extruder uses a metering feeder to evenly and uniformly feed at a constant speed.
(3)When the discharge of the mouth mold is uniform and the plasticity is good,it can be used for pulling and shaping the sleeve.The determination of the degree of plasticization depends on experience,and can generally be based on the appearance of the extruded material,which includes a glossy surface,no impurities,no foaming,coking,and discoloration.When the extruded material is squeezed by hand to a certain extent without burrs or cracks,and has a certain degree of elasticity,it indicates that the material has good plasticization.If the plasticization is poor,the screw speed,barrel and head temperature can be adjusted appropriately until the requirements are met.
(4)During the extrusion production process,various process parameters should be checked regularly according to the process requirements to ensure they are normal,and a process record form should be filled out.Inspect the quality of profile products according to quality inspection standards,and take timely solutions if any problems are found.
3.Shutdown
(1)Stop feeding,squeeze out the plastic protruding from the machine,and when the screw is exposed,turn off the power supply to the barrel and head,and stop heating.
(2)Turn off the power supply of the extruder and auxiliary equipment,and stop the screw and auxiliary equipment from running.
(3)Remove the machine head by connecting the flange.Clean the various components of the porous plate and the machine head.To prevent damage to the inner surface of the machine head during cleaning,residual materials inside the machine head should be cleaned with steel laws and steel sheets.Then,the plastic adhered to the machine head should be removed with sandpaper,polished,and coated with engine oil or silicone oil for rust prevention.
(4)Cleaning of screws and machine barrels:After removing the machine head,restart the main engine,add shutdown materials(or crushed materials),clean the screws and machine barrels.At this time,use low speed(about SR/min)to reduce wear and tear on the screws.After the shutdown material is completely crushed into powder and squeezed out,compressed air can be used to repeatedly blow out residual particles and powder from the feeding port and exhaust port until there is no residual material in the barrel.Then,reduce the screw speed to zero,stop the extruder,and close the main power and cold water main valve.
(5)The safety items that should be paid attention to during extrusion include the rotation of electricity,heat,machinery,and the loading and unloading of bulky components.The extruder room must be equipped with lifting equipment to install and remove bulky components such as the machine head and screws to ensure safe production.
4.Maintenance and upkeep of the extruder
The screw extrusion system is maintained through two methods:daily maintenance and regular maintenance.
(1)Daily maintenance is a routine work that does not take up equipment operating hours and is usually completed during the start-up period.The key is to clean the machine,lubricate all moving parts,tighten easily loose threaded parts,timely inspect and adjust the motor,control instruments,various working components and pipelines,etc.
(2)Regular maintenance is generally carried out after the extruder has been continuously running for 2500-5000 hours and the machine is shut down.The machine needs to be disassembled for inspection,measurement,and identification of the wear of major components,replaced with parts that have reached the specified wear limit,and repaired with damaged parts.
(3)Empty machine operation is not allowed to prevent screw and machine from rolling burrs.
(4)If there is any abnormal noise during the operation of the extruder,it should be stopped immediately for inspection or repair.
(5)Strictly prevent metal or other debris from falling into the hopper to prevent damage to the screw and barrel.To prevent iron debris from entering the barrel,magnetic components or magnetic racks can be installed at the feeding port of the barrel to prevent debris from falling.The material must be screened in advance.
(6)Pay attention to the cleanliness of the production environment,and do not let garbage and impurities mix into the material to block the filter plate,affecting product output,quality,and increasing machine head resistance.
(7)When the extruder needs to be stopped for a long time,anti rust lubricating grease should be applied to the working surfaces of the screw,machine blade,machine head,etc.Small screws should be suspended in the air or placed in dedicated wooden boxes,and leveled with wooden blocks to prevent deformation or damage to the screws.
(8)Regularly calibrate temperature control instruments,check their correctness of adjustment and sensitivity of control.
(9)The maintenance of the gearbox of the extruder is the same as that of a general standard gearbox.The main task is to inspect the wear and failure of gears,bearings,and other components.The gearbox should use the lubricating oil specified in the machine manual,and add oil according to the specified oil level height.If the oil level is too low,the lubrication will not be reversed,which will reduce the service life of the parts;Excessive oil,high heat generation,high energy consumption,and easy deterioration of oil can also cause lubrication failure and result in damage to parts.The oil leakage part of the gearbox should be replaced with a sealing gasket(ring)in a timely manner to ensure the lubricating oil level.
(10)The inner wall of the cooling water pipe attached to the extruder is prone to scaling,while the outer part is prone to corrosion and rust.Careful inspection should be carried out during maintenance.Excessive scale can clog the pipeline,fail to achieve cooling effect,and severe rust can cause water leakage.Therefore,measures such as descaling and anti-corrosion cooling must be taken during maintenance.
(11)For DC motors that drive screw rotation,it is important to focus on checking the wear and contact of the brushes,and regularly measure whether the insulation resistance value of the motor is above the specified value.In addition,check whether the connecting wires and other components are rusted,and take protective measures.
(12)Designate a dedicated person to be responsible for equipment maintenance and upkeep.And record each maintenance and repair in detail in the factory equipment management file.
The use of screw extruder includes a series of processes such as installation,adjustment,trial operation,operation,maintenance,and repair.Its use has commonalities with general machines,mainly manifested in the driving motor and speed reduction device.However,the working system of the screw extruder,namely the extrusion system,has its own characteristics,and special attention should be paid to its characteristics when using the screw extruder.
The installation,adjustment,and testing of the machine are generally clearly specified in the user manual of the extruder.Here,the operating methods of the extruder are briefly described as follows:
The operator must be familiar with the structural characteristics of the extruder they are operating,especially to correctly grasp the structural characteristics of the screw,the control instrument characteristics of heating and cooling,the characteristics of the machine head,and the assembly situation,in order to correctly grasp the extrusion process conditions and operate the machine correctly.
The operation methods for extruding different plastic products are different,but there are also similarities.Below is a brief introduction to the same operating steps and precautions when extruding various products.
1.Preparation work before
(1)Plastic used for extrusion molding.The raw materials should meet the required drying requirements,and further drying is necessary if necessary.And sieve the raw materials to remove clumps and mechanical impurities.
(2)Check whether the water,electricity,and gas systems in the equipment are normal,ensure that the water and gas circuits are unobstructed and leak free,whether the electrical system is normal,and whether the heating system,temperature control,and various instruments are working reliably;Low speed trial run of the auxiliary machine,observe whether the equipment is running normally;Start the vacuum pump on the molding table and observe if it is working properly;Apply lubricating oil to the lubrication areas of various equipment.If any faults are found,they should be promptly resolved.
(3)Install the machine head and set the sleeve.Choose the appropriate head specifications based on the variety and size of the product.Install the machine head in the following order.
①The machine head should be assembled together and installed as a whole on the extruder.
②Before assembling the machine head,the grease applied during storage should be wiped off,and the surface of the mold cavity should be carefully checked for scratches,scratches,and rust spots.Necessary polishing should be carried out,and then a layer of silicone oil should be applied to the surface of the flow channel.
③Assemble the various plates of the machine head in sequence,apply high-temperature grease to the threads of the bolts,and then tighten the bolts and flange.
④Place the porous plate between the machine head flanges to ensure that it is tightly pressed without overflowing.
⑤Before tightening the fastening bolts of the connecting flange between the machine head and the extruder,the horizontal position of the mouth mold should be adjusted.The square machine head can be adjusted horizontally,while the circular machine head should be leveled with the bottom surface of the mouth mold based on the fixed model adhesive surface.
⑥Tighten the connecting flange bolts,tighten the machine head fastening bolts,install the heating ring and thermocouple,and ensure that the heating ring is tightly attached to the outer surface of the machine head.
⑦Install the set sleeve and adjust it in place,check if the center line of the main engine,set sleeve and traction machine is aligned.After adjustment,tighten the fixing bolts.Connect the water pipes and vacuum pipes of the fixed sleeve.
⑧Turn on the heating power and evenly heat up the machine head and casing.Simultaneously open the inlet valves of the cooling water and exhaust vacuum pump at the bottom of the feeding hopper and the gearbox.When heating up,adjust the temperature of each section to 140℃first.When the temperature rises to 140℃,keep it warm for 30-40 minutes,and then raise the temperature to the normal production temperature.When the temperature rises to the required temperature for normal production,maintain it for about 10 minutes to stabilize the temperature of various parts of the machine before starting production.The length of insulation time varies depending on different models of extruders and types of plastic materials.Keep it warm for a period of time to ensure that the temperature inside and outside the machine is consistent,in order to avoid the instrument indicating that the temperature has reached the required temperature but the actual temperature is too low.If the material is put into the extruder at this time,due to the actual temperature being too low and the melting viscosity of the material being too high,it will cause axial force overload and damage the machine.
⑨Feed the raw materials used for startup into the hopper for future use.
2.Power on
(1)After the constant temperature,the machine can be started up.Before starting up,the machine head and the flange bolts should be tightened again to eliminate the difference in thermal expansion between the bolts and the machine head.The sequence of tightening the machine head bolts is diagonal tightening,and the force should be even.When tightening the flange nut of the machine head,it is required that the tightness is consistent all around,otherwise material may run out.
(2)Turn on the machine,select the"Ready to Start"button,then connect the"Start"button,and slowly rotate the screw speed adjustment knob to start the screw speed slowly.Then gradually increase the speed while adding a small amount of material.When adding materials,close attention should be paid to the changes in the indication of the host ammeter and various indicator heads.The screw torque should not exceed the red mark(usually 65%-75%on the torque table).Before the plastic profile is extruded,no one is allowed to stand in front of the mouth mold to prevent injury accidents caused by bolt breakage or wet foaming of raw materials.After the plastic is extruded from the head mold,it is necessary to slowly cool the extruded material and guide it onto the traction device and shaping mold,and start these devices.Then,based on the indicated values of the control instrument and the requirements for the extruded product.Adjust each part accordingly to ensure that the entire extrusion operation reaches a normal state.And add enough materials as needed,the twin-screw extruder uses a metering feeder to evenly and uniformly feed at a constant speed.
(3)When the discharge of the mouth mold is uniform and the plasticity is good,it can be used for pulling and shaping the sleeve.The determination of the degree of plasticization depends on experience,and can generally be based on the appearance of the extruded material,which includes a glossy surface,no impurities,no foaming,coking,and discoloration.When the extruded material is squeezed by hand to a certain extent without burrs or cracks,and has a certain degree of elasticity,it indicates that the material has good plasticization.If the plasticization is poor,the screw speed,barrel and head temperature can be adjusted appropriately until the requirements are met.
(4)During the extrusion production process,various process parameters should be checked regularly according to the process requirements to ensure they are normal,and a process record form should be filled out.Inspect the quality of profile products according to quality inspection standards,and take timely solutions if any problems are found.
3.Shutdown
(1)Stop feeding,squeeze out the plastic protruding from the machine,and when the screw is exposed,turn off the power supply to the barrel and head,and stop heating.
(2)Turn off the power supply of the extruder and auxiliary equipment,and stop the screw and auxiliary equipment from running.
(3)Remove the machine head by connecting the flange.Clean the various components of the porous plate and the machine head.To prevent damage to the inner surface of the machine head during cleaning,residual materials inside the machine head should be cleaned with steel laws and steel sheets.Then,the plastic adhered to the machine head should be removed with sandpaper,polished,and coated with engine oil or silicone oil for rust prevention.
(4)Cleaning of screws and machine barrels:After removing the machine head,restart the main engine,add shutdown materials(or crushed materials),clean the screws and machine barrels.At this time,use low speed(about SR/min)to reduce wear and tear on the screws.After the shutdown material is completely crushed into powder and squeezed out,compressed air can be used to repeatedly blow out residual particles and powder from the feeding port and exhaust port until there is no residual material in the barrel.Then,reduce the screw speed to zero,stop the extruder,and close the main power and cold water main valve.
(5)The safety items that should be paid attention to during extrusion include the rotation of electricity,heat,machinery,and the loading and unloading of bulky components.The extruder room must be equipped with lifting equipment to install and remove bulky components such as the machine head and screws to ensure safe production.
4.Maintenance and upkeep of the extruder
The screw extrusion system is maintained through two methods:daily maintenance and regular maintenance.
(1)Daily maintenance is a routine work that does not take up equipment operating hours and is usually completed during the start-up period.The key is to clean the machine,lubricate all moving parts,tighten easily loose threaded parts,timely inspect and adjust the motor,control instruments,various working components and pipelines,etc.
(2)Regular maintenance is generally carried out after the extruder has been continuously running for 2500-5000 hours and the machine is shut down.The machine needs to be disassembled for inspection,measurement,and identification of the wear of major components,replaced with parts that have reached the specified wear limit,and repaired with damaged parts.
(3)Empty machine operation is not allowed to prevent screw and machine from rolling burrs.
(4)If there is any abnormal noise during the operation of the extruder,it should be stopped immediately for inspection or repair.
(5)Strictly prevent metal or other debris from falling into the hopper to prevent damage to the screw and barrel.To prevent iron debris from entering the barrel,magnetic components or magnetic racks can be installed at the feeding port of the barrel to prevent debris from falling.The material must be screened in advance.
(6)Pay attention to the cleanliness of the production environment,and do not let garbage and impurities mix into the material to block the filter plate,affecting product output,quality,and increasing machine head resistance.
(7)When the extruder needs to be stopped for a long time,anti rust lubricating grease should be applied to the working surfaces of the screw,machine blade,machine head,etc.Small screws should be suspended in the air or placed in dedicated wooden boxes,and leveled with wooden blocks to prevent deformation or damage to the screws.
(8)Regularly calibrate temperature control instruments,check their correctness of adjustment and sensitivity of control.
(9)The maintenance of the gearbox of the extruder is the same as that of a general standard gearbox.The main task is to inspect the wear and failure of gears,bearings,and other components.The gearbox should use the lubricating oil specified in the machine manual,and add oil according to the specified oil level height.If the oil level is too low,the lubrication will not be reversed,which will reduce the service life of the parts;Excessive oil,high heat generation,high energy consumption,and easy deterioration of oil can also cause lubrication failure and result in damage to parts.The oil leakage part of the gearbox should be replaced with a sealing gasket(ring)in a timely manner to ensure the lubricating oil level.
(10)The inner wall of the cooling water pipe attached to the extruder is prone to scaling,while the outer part is prone to corrosion and rust.Careful inspection should be carried out during maintenance.Excessive scale can clog the pipeline,fail to achieve cooling effect,and severe rust can cause water leakage.Therefore,measures such as descaling and anti-corrosion cooling must be taken during maintenance.
(11)For DC motors that drive screw rotation,it is important to focus on checking the wear and contact of the brushes,and regularly measure whether the insulation resistance value of the motor is above the specified value.In addition,check whether the connecting wires and other components are rusted,and take protective measures.
(12)Designate a dedicated person to be responsible for equipment maintenance and upkeep.And record each maintenance and repair in detail in the factory equipment management file.