Correct and reasonable use of the extruder can give full play to the efficiency of the machine, maintain a good working state and extend the service life of the machine.
The use of screw extruder includes a series of links such as machine installation, adjustment, test run, operation, maintenance and repair, etc. Its use has the common characteristics of general machines, mainly in the aspects of driving motor and deceleration and transmission device.
However, the working system of the screw extruder is the extrusion system, but it has its own characteristics, and special attention should be paid to its characteristics when using the screw extruder.
The installation, adjustment and test run of the machine are generally specified in the operation manual of the extruder. Here, the operation method, maintenance and maintenance of the extruder are briefly described as follows:
1. Operation method of extruder
Operators must be familiar with the structural characteristics of the extruder they operate, especially to correctly grasp the structural characteristics of the screw, heating and cooling control instrument characteristics, head characteristics and assembly conditions, in order to correctly grasp the extrusion process conditions, correctly operate the machine.
The operation method of extruding different plastic products is different, but there are some similarities.
The following is a brief introduction of the same operation steps and precautions during extrusion of various products.
1. Preparations before driving
(1) plastics used for extrusion molding.
Raw materials should meet the required drying requirements, further drying if necessary.
The raw material is screened to remove agglomeration and mechanical impurities.
(2) Check whether the water, electricity and gas systems in the equipment are normal, to ensure that the water and gas channels are smooth and no leakage, whether the electrical system is normal, and whether the heating system, temperature control and various instruments work reliably;
Low speed test of empty auxiliary engine to observe whether the equipment is running normally;
Start the vacuum pump of the setting table and observe whether it works normally.
Oil and lubricate the smooth parts of various equipment.
If the fault is found, remove it in time.
(3) Mounting head and finalizing sleeve.
According to the product variety, size, choose a good head specifications.
Install the nose in the following order.
① The head should be assembled together and installed on the extruder as a whole.
(2) before assembling the machine head, should wipe off the grease coated when saving, carefully check whether there are bumps, scratches, rust spots on the surface of the cavity, carry out the necessary polishing, and then coat the surface of the flow channel with a layer of silicone oil.
(3) Assemble each plate of the machine head in order, coat the screw thread of the bolts with high temperature grease, and then screw the bolts and flanges.
(4) The porous plate is placed between the flange of the machine head to ensure that the porous plate is pressed without overflow.
Before tightening the fastening bolt connecting the flange of the machine head and the extruder, the horizontal position of the die should be adjusted. The level of the square head can be adjusted horizontally. The circular head is leveled with the bottom surface of the die head based on the rubber bottom surface of the shaping model.
Tighten the connecting flange bolt, tighten the fastening bolt of the machine head, install the heating ring and thermocouple, pay attention to the heating ring and the outer surface of the machine head.
Install the finalizing sleeve and adjust the position, check the host, finalizing the sleeve and the center line of the tractor is aligned.
After adjustment, tighten the retaining bolt.
Connect the water pipes and vacuum tubes of the shaping sleeve.
Open the heating power supply, the head, machine simple uniform heating and heating.
At the same time, open the cooling water at the bottom of the hopper and the gear box and the inlet valve of the exhaust vacuum pump.
When heating and heating, the temperature of each section should be adjusted to 140℃, and then the temperature should be kept for 30-40min when the temperature rises to 140℃, and then the temperature should be raised to the temperature of normal production.
When the temperature rises to the required temperature for normal production, keep it for about 10min so that the temperature of each part of the machine tends to be stable before starting production.
The length of holding time varies according to different types of extruders and plastic materials.
Keep the heat for a period of time to make the internal and external temperature of the machine consistent, so as not to indicate the instrument temperature has reached the required temperature, but the actual temperature is too low, if the material is put into the extruder, because the actual temperature is too low, the material melting viscosity is too large, it will cause axial force overload and damage the machine.
⑨ The raw materials used for driving are fed into the hopper for use.
2, drive
(1) After constant temperature, you can start up. Before starting up, you should tighten the nose and the flange bolts of the extruder once again to eliminate the difference between the thermal expansion of the bolts and the nose. The order of tightening the head bolts is diagonal tightening, and the force should be uniform.
When tightening the flange nut of the machine head, the tightness of all sides should be consistent, otherwise the material should be run away.
(2) to start, select press the "ready to start" button, then connect to the "start" button, and then slowly rotate the screw speed adjusting knob, screw speed slowly start.
Then gradually speed up, while a small amount of feeding.
When feeding, pay close attention to the host ammeter and the indication of various indicator head changes.
The screw torque shall not exceed the red mark (generally 65%-75% of the torque meter).
Before the plastic profile is extruded, no one should stand in front of the die to prevent injury accidents caused by bolt breaking or wet foaming of raw materials.
After the plastic is extruded from the nose die, it is necessary to cool the extruded material slowly and lead the traction device and mold, and start these devices.
Then according to the indicator value of the control instrument and the requirements of extruded products.
Each part will be adjusted accordingly to make the whole extrusion operation to reach the normal state.
And according to the need to add sufficient material, double screw extruder adopts the metering feeder uniform and uniform speed of feeding.
(3) when the mouth die discharge is uniform and good plastic can be drawn to shape the set.
The degree of plasticization should be judged by experience. Generally, it can be judged according to the appearance of the extruded material, that is, the surface is glossy, no impurities, no foaming, coke and discoloration. The extruded material is extruded fine to a certain extent by hand without burr or crack, and has a certain elasticity.
If plasticizing is not good, the screw speed, barrel and head temperature can be adjusted properly until the requirements are met.
(4) In the process of extrusion production, various process parameters should be checked regularly according to the process requirements, and fill in the process record sheet.
Check the quality of profile products according to the quality inspection standard, and take corrective action if any problem is found.
3, parking
(1) Stop feeding, extrude the plastic in the extruder, expose the screw, close the barrel and head power supply, stop heating.
(2) Turn off the power supply of the extruder and auxiliary machines, so that the screw and auxiliary machines stop running.
(3) Open the nose connecting flange and remove the nose.
Clean the perforated plate and various parts of the machine head.
In order to prevent damage to the inside surface of the machine head, the residual material in the machine head should be cleaned up by steel law and steel sheet, and then the plastic adhered to the machine head should be removed with sandpaper, polished and coated with oil or silicone oil for rust prevention.
(4) screw and barrel cleaning, after removing the head, restart the main engine, add stopping material (or crushing material), clean the screw and barrel, at this time the screw is selected at low speed (SR /min or so) to reduce wear.
When the stop material is crushed into powder and completely extruded, the compressed air can be used to blow out the residual granule and powder repeatedly from the feeding port and exhaust port until there is no residual material in the barrel. After that, the screw speed is reduced to zero, the extruder is stopped, and the total power supply and the total cold water valve are closed.
(5) Safety items should be paid attention to during extrusion: electrical, thermal, mechanical rotation and loading and unloading of heavy parts, etc.
Extrusion locomotive room must be equipped with lifting equipment, assembly and disassembly of the head, screw and other heavy parts to ensure safe production.
Two, extruder maintenance and maintenance
The screw extrusion system is maintained in two ways: daily maintenance and regular maintenance.
(1) Daily maintenance is a regular routine work, which does not account for equipment operation hours and is usually completed during the driving period.
The key point is to clean the machine, lubricate the moving parts, tighten the screw threads that are easy to loose, timely check and adjust the motor, control instruments, various working parts and pipelines, etc.
(2) Regular maintenance is generally carried out after continuous operation of the extruder for 2500-5000h. The machine needs to be disassembled to check, measure and identify the wear condition of the main parts, replace the parts that have reached the specified wear limit and repair the damaged parts.
(3) do not allow empty car operation, so as not to screw and machine simple rolling wool.
(4) If abnormal sound occurs during the operation of the extruder, it should be stopped immediately for inspection or repair.
(5) Strictly prevent metal or other sundries from falling into the hopper, so as not to damage the screw and barrel.
In order to prevent iron sundries from entering the barrel, magnetic absorbing parts or magnetic frames can be installed at the feeding opening of the material into the barrel to prevent sundries from falling into the material which must be screened in advance.
(6) pay attention to the production environment clean, do not make garbage impurities mixed with materials blocked filter plate, affect product output, quality and increase the resistance of the head.
(7) When the extruder needs to stop using for a long time, anti-rust grease should be coated on the working surface of the screw, machine blade and machine head.
Small screw should be suspended in the air or placed in a special wooden box, and with wooden blocks to avoid deformation or injury of the screw.
(8) Regularly calibrate the temperature control instrument to check the correctness of its adjustment and the sensitivity of control.
(9) Extruder reducer maintenance is the same as the general standard reducer.
It is mainly to check the wear and failure of gears and bearings.
The reducer should use the lubricating oil specified in the machine manual, and add oil according to the specified oil level height. The oil is too little, the lubrication is not anti, and the service life of the parts is reduced.
Too much oil, high heat, energy consumption, oil deterioration, the same lubrication failure, resulting in damage to parts.
The oil leakage part of the gearbox should be replaced in time to ensure the amount of lubricating oil.
(10) The inner wall of the cooling water pipe attached to the extruder is easy to scale and the external is easy to corrode and rust.
Careful inspection should be done during maintenance. ExcESSIVE scale will block the pipeline, fail to reach the cooling effect, and serious corrosion will leak water. Therefore, scale removal and anticorrosion cooling measures must be taken in maintenance.
(11) to drive the screw rotation of the DC motor to focus on the check of brush wear and contact, the motor insulation resistance value is above the specified value should also be often measured.
In addition, check whether the connecting line and other parts are rusty, and adopt protective measures.
(12) Designate a special person to be responsible for equipment maintenance.
Include detailed records of each maintenance and repair into plant equipment management files.