PVC extruder operation process

In the production process of PVC products, common problems include

• Toughness not up to standard

• Insufficient gloss

• precipitation

• Burnt material

• Insufficient transparency

• Short start-up time

There are many factors affecting the processing of PVC products, which often affects the whole body. When solving production problems, it is not only necessary to optimize the formulation, but also to consider all aspects of the equipment and process conditions.

With more than 30 years of experience in PVC applications, Riehle Chemicals provides customers with comprehensive solutions for turnkey projects. Here we summarize the operation process of PVC extruder for your reference.

01 Mixing process

1. Material:

PVC resin, calcium carbonate, heat stabilizer, Riehle Chemical RCM polyester homopolymer, Riehle Chemical RLWAX lubricant, weathering agent, whitening agent (color powder) and so on.

2.Operation flow:

Claiming - Batching - Hot mixing - Cold mixing - Extruding - Hauling - Sizing - Cooling - Cutting - Inspection - Packing - Storage.

02 Extrusion process

The operator must be familiar with the structural characteristics of the extruder operated, the characteristics of the heating and cooling control instrument, the characteristics of the head and assembly, in order to correctly grasp the extruder process conditions, the correct operation of the machine, the extrusion of different product models and specifications of the operating method is different, the production process, should be in accordance with the requirements of the process to regularly check whether the various process parameters are normal.

※Preparation before starting the machine

1、Die preparation and installation

1.1 According to the production arrangements, find out the production of the product mold, and the related sizing set, rubber ring, clamps, heating pads, heating rings and operating tools (active wrenches, hexagonal wrenches, screwdrivers, sandpaper, pry bars, etc.).

1.2 Check the parts of molds and sizing sets, and polish the parts in contact with materials;

1.3 Install the corresponding molds, sizing sets, rubber rings, clamps, heating pads, heating rings, etc.;

1.4 Adjust the gap between the mouth of the mold, connect the heating plate, heating ring power cord;

2、the extruder host inspection

2.1 Check the extruder's water, gas, oil is smooth, there is no leakage of water, gas, oil and so on;

2.2 Turn on the power supply of the host, open the power switch of each heating unit, and set a relatively low temperature, use a thermometer to check whether the heating unit is normal, whether the temperature control instrument is normal, then close the power switch of the heating unit;

2.3 Check whether the operation of the host vacuum pump is normal, and whether its pipeline is smooth, with or without air leakage, water leakage or blockage;

2.4 Check whether the operation of the feeding device is normal.

2.5 Wait for the above steps are shown normal, open the mold sections of the heating switch, and set the initial process temperature at about 120 degrees;

2.6 After the temperature of each section of the mold reaches the initial setting value, start to set the operation temperature; the following is the reference temperature setting value:

        Cylinder one (feed zone) 185 degrees - 192 degrees

        Barrel two (heating zone) 188 degrees-195 degrees

        Barrel three (plasticizing zone) 175 degrees - 182 degrees

        Cylinder four (feeding zone) 160 degrees-172 degrees

        Combined core 160-172 degrees 

        Mold head 175-185 degrees    

        Mouth mold 188 degrees-205 degrees

2.7 The above temperature values are for reference only, the actual setting should be based on product quality requirements; to be set for each section of the mold temperature have reached the set value, you need to continue to keep warm for 30 minutes, so that the heating unit is heated evenly.

3、Check of extruder auxiliary machine

3.1 Cooling water tank inspection

1) Open the power switch of cooling water tank;

2) Press the forward and backward movement switch of the cooling water tank to check whether the forward and backward movement of the tank is normal;

3) Open the cooling water inlet valve of the cooling water tank cooling water, open the pump operation switch, check whether its water inlet and spray device is clogged, open the water outlet valve of the water tank, check whether its water outlet waterway is normal;

4)Open the vacuum pump of the water tank and check the operation of the vacuum pump;

5) Check whether the level and centerline of the cooling water tank and the centerline of the extruder are in the same straight line;

3.2 Traction machine

1) Start the traction machine and check whether the traction of the traction machine is normal;

2) Press the lower pressure and lift switch of the traction machine to check whether its air circuit is normal;

3) Check whether the track position of the traction machine is adjustable;

3.3 Checking the cutting machine and pipe racks

1) Ordinary saw blade cutting machine

a. Adjust the height of the fixture for cutting and do the cutting action to check whether its action is normal.

b.Adjust the position of the cutting travel switch.

2) Planetary cutting machine

a.Check the cleanliness of the working chamber of the cutting machine, turn on the power switch and air valve switch of the cutting machine;

b.Replace the fixture before and after the cutting machine;

c.Adjust the position of the cutting travel switch to set the length of the product (which should be slightly greater than the actual length);

d. Adjust the position of the cutter so that it has the right amount of feed;

e. Press the “manual” cutting button to start pre-feeding the knife, and from both ends of the cutting machine to see the actual position of the blade into the knife;

f. If the amount of feed is not appropriate, you need to follow the above steps to reset until appropriate;

g. Take a section of about 2 meters with the same diameter as the pipe to be produced, set it up on the clamps at both ends of the cutting machine, repeat the actions e) and f) to observe the cutting action and check the cutting effect, if the cutting effect is not good then you need to re-adjust the amount of knife feed;

3.4 Uniformly check whether the centerline of the extruder main machine, cooling water tank, haul-off machine, cutting machine and pipe-rowing rack is on the same straight line, otherwise it needs to be adjusted to make it on the same straight line;

3.5 Install the traction tube on the auxiliary machine;

3.6 Check the computerized inkjet printer.

※Power on process

1、Reconfirm whether the temperature rise of the extruder is normal or not, wait until the temperature of the mold reaches 150 ℃ or more, re-tighten the fastening screws and bolts of the mold and re-adjust the wall thickness adjusting screws, so as to make the gap between the mouth and the mold more uniform;

2、To be the host temperature to reach the set temperature and insulation after 30min (usually to normal production of the machine, in order to prevent the material in the barrel decomposition can be in the host temperature than the actual production temperature is lower than the actual production temperature of 10 ℃ ~ 20 ℃ when the first slow start), open the main engine oil pump, lubrication, cooling system and water system;

3、After confirming the synchronization of the host, screw, feeding speed knob are in the “zero” position or in the smallest position, start the host motor, and slowly and evenly accelerate to about 5RPM;

4、Start the charging motor of the charging system, and make the charging speed run at a lower speed relative to the screw speed, so that the feeding material is in a “hungry” state;

5、Depending on the size of the host current, and appropriately increase the host and feeding speed, need to pay close attention to the changes in current when increasing the speed, in order to avoid excessive acceleration of the current should be the first to raise the host speed, and then raise the speed of the feeding; just start the host speed of 5 ~ 10 revolutions per minute, feeding speed of 3 ~ 6 revolutions per minute, at the same time, pay close attention to the host current and the changes in various indicator meters: 90 machine starting current can not be more than 60A; 65 machine starting current At the same time, we should pay close attention to the current of the host and the changes of various indicator meters: 90 machine start current can not exceed 60A; 65 machine start current can not exceed 40A; 55 machine start current can not exceed 30A, so as not to cause excessive pressure and damage to the machine. To be material from the mouth of the mold out before you can slowly speed up, moderately increase the flow of electricity.

6、Check whether the material is uniform, use the adjustment to adjust the wall thickness of the material evenly.

7、When the mouth of the die out of uniform material and excellent plasticization can be hauled into the stereotypes set, the degree of plasticization needs to be judged by experience. Generally can be based on the appearance of the extruded material to judge, that is, the surface has a glossy, unadulterated, no foaming, scorched material and discoloration, the hand will pull the extruded material to a certain level of fine burrs, cracks; have a certain degree of elasticity, tensile strength, indicating that the plasticization of the good, if the plasticization of the poor can be appropriate deployment of the party, the barrel, the temperature of the die head, in order to achieve the production requirements.

8、From the exhaust port to observe the plasticization of the material, timely open the vacuum pump water switch and start its motor to vacuum the material in the cylinder.

9、In the mouth of the mold out of the material uniform and good plasticization, in the tube embryo directly above the knife to cut a round hole and the tube embryo into the sizing set, and at the same time a small amount of cooling water to open the cooling water, will be cooled, to be out of the embryo sizing set of the tube embryo, with a hook will be connected to the embryo and the hauling tube.

10、Start the traction machine and quickly adjust the traction speed to the appropriate speed (small diameter pipe does not need to traction, then estimate a traction speed in advance and let it open, and then directly from the tube embryo from the calibrating sleeve manually pulled to the traction machine, and then adjust its speed).

11、Cover the cooling water tank, turn on the water pump and vacuum pump, cool the tube embryo in the water tank and let the vacuum in the water tank maintain at 0.02~0.04Mpa.

12、According to the requirements of the product, adjust the content of the computerized inkjet printer, and other settings and start printing.

13、Start the cutting machine.

14、Gradually speed up the screw and charging speed of the extruder until the production speed reaches the requirement of the production speed, and start normal production.

15、During normal production, the unpacked products on the row of pipe racks shall not exceed the following quantities: a. 5 for D75mm, D110mm and 3 for D160mm, D200mm when single pipe is packed; b. All products shall not be more than 1.5 bundles when wrapped with packing ropes (except for meal time).

16、For safety reasons, during normal production, the operator must operate on the front side of the extruder, and no one is allowed to contact any part of his body with the movable parts of the machine.

17、Measurement and packaging records:

17.1 Use vernier calipers to measure the outer diameter, wall thickness, out-of-roundness and length of the pipe embryo. And adjust the extruder operating conditions so that the size control within the standard range. Line pipe need to use grip spring to test the inner hole to meet the requirements.

17.2 Take samples to compare the pipe color with the sample; weigh the pipe within the standard range; and make a simple physical properties test (line pipe can not be folded; drainpipe foot brittle, etc.);

17.3 According to the actual need to take samples to the quality control to do further physical properties of the test;

17.4 Record the operating conditions, data archives;

17.5 Arrange packaging workers according to packaging specifications and record capacity.

18, do a good job of shift handover and records.

※Checks and precautions during operation

1、Pay attention to the extruder host current change is stable, such as fluctuations in the larger should reduce the amount of material, to be current stability before slowly increase the amount of material, such as the amount of material to reduce the current is still high should be shut down to check.

2、Check the gear box, the host body and other transmission parts have no abnormal sound.

3、Check whether the fasteners are loose and whether there is any abnormal vibration during operation.

4、Check the oil temperature in the gear reducer, the oil temperature generally shall not exceed 60℃.

5、Check the host and auxiliary temperature control, cooling, lubrication, vacuum system operation is normal.

6、Observe the extruder extruded material is stable and uniform, there is no poor plasticization, overheating, discoloration and head pressure instability and other phenomena.

7、Do a good job of extruder temperature, pressure, host speed, feeding speed, host current, vacuum and other process parameters of the record.

8、Do a good job of machine hygiene.

※Shutdown

1、Normal shutdown

1) Turn off the switch of each heating unit of the mainframe hopper first;

2) Close the hopper outlet or adjust the feeding speed to “zero”, and the motor stop button;

3) Shut down and clean the vacuum pump of the host;

4) Gradually reduce the host screw speed, as far as possible to empty the material in the barrel, the host screw speed to “zero” (if necessary, you need to add the cleaner material and wait until the cleaner material out of the mouth of the mold before stopping the screw);

5) Remove the mold in time and clean the material in the mold in time;

6) start the screw again, to be squeezed out of the material in the barrel, the speed will be adjusted to “zero” position, and close the host of the oil pump, lubrication, cooling system and water system and the main power supply;

7) Close the auxiliary parts of the water system, gas system and related motors;

8) stop the printing action of the computer inkjet printer, turn off the power, and use special cleaning agent to clean the print head;

9) Close the auxiliary power supply.

2、abnormal shutdown (power outage and other accidents caused by the shutdown): after the shutdown should be quickly the host screw, feeding speed down to “zero”, and turn off the heating unit switch and other auxiliary systems, to be dealt with after the fault, and then according to the normal start-up order to start, such as a longer period of time downtime will need to remove the mold to clean up and then reload the mold after the Start the machine.

3、Clean up the extruder auxiliary machine and do the sanitary work.

03 Extruder general faults and their elimination methods

※The host current is not stable

1、production reasons:

1)Uneven feeding.

2)Main motor bearing is damaged or poorly lubricated.

3)Failure of a section heater, not heating.

4) Screw adjustment pad is not right, or relative position is not right, screw prong elements interference.

2、treatment method:

1)Check the feeder, troubleshooting.

2)Overhaul the main motor and replace the bearings if necessary.

3)Check whether each heater works normally, and replace the heater if necessary.

4)Check the adjustment pad, pull out the screw to check the screw prong elements for interference.

※The main motor can not start

1、Causes:

1) There is a mistake in the driving program.

2)There is a problem with the main motor thread, whether the fuse wire is burnt ring.

3)The interlocking device related to the main motor works.

2、Processing methods:

1)Check the program and drive again in the correct driving order.

2)Check the main motor circuit.

3)Check whether the lubricating oil pump starts, and check the status of the interlocking device related to the main motor. The motor cannot be turned on if the oil pump does not turn on.

4)The inverter induction power is not discharged, turn off the main power and wait for 5 minutes before starting.

5)Check whether the emergency button is reset.

※The machine head is not discharging material smoothly or is clogged.

1、Produce the cause:

1)The heater is not working in a certain section, and the material is not plasticized well.

2)The operating temperature is set low, or the molecular weight distribution of the plastic is wide and unstable.

3)There may be foreign matter which is not easy to melt.

2、Treatment:

1)Check the heater and replace if necessary.

2)Verify the set temperature of each section, and if necessary, consult with the processor to increase the temperature setting.

3)Clean and check the extrusion system and head.

※The main electric start current is too high

1、Produce cause:

1)Insufficient heating time and high torque.

2)A section of the heater does not work.

2、treatment method:

1)Apply hand disk when driving, if it is not easy, then prolong the heating time or check whether each section heater is working properly.

※The main motor makes an abnormal sound:

1、 generating causes:

1)The main motor bearing is damaged.

2) The main motor silicon controlled rectifier line in a silicon controlled damage.

2、 treatment methods:

1) Replace the main motor bearings.

2) Check the SCR rectifier circuit and replace the SCR components if necessary.

※The main motor bearing temperature rise is too high:

1、Causes:

1)Poor bearing lubrication.

2)Severe bearing wear.

2、Producing cause:

1)Check and add lubricant. Check motor bearings and replace if necessary.

※Unstable head pressure:

1、Producing cause:

1)Uneven speed of main motor.

2)Uneven rotational speed of feed motor, fluctuation in feed quantity.

2、Treatment method:

1)Check the main motor control system and bearings.

2)Check the feeding system motor and control system.

※Lubricating oil pressure is low:

1、the cause:

1)Lubricating oil system regulator pressure setting is too low.

2)Failure of oil pump or clogging of suction pipe.

2、Treatment method:

1)Check and adjust the lubricating oil system pressure regulator.

2)Check the oil pump and oil suction pipe.

※Automatic screen changer is slow or does not work

1、Causes:

1)Low air or oil pressure.

2) Cylinder (or hydraulic station) leakage (or oil leakage).

2、treatment method:

1)Check the power system of the screen changer.

2)Check the sealing of the cylinder or hydraulic cylinder.

※Safety pin or safety device is cut off

1、Causes:

1)Extrusion system torque is too high.

2)The main motor and input bearing coupling is not concentric.

2、Treatment method:

1)Check the extrusion system whether there is metal and other things into the jammed screw. At the beginning of the occurrence, check whether the preheating warming time or warming value meets the requirements.

2)Adjust the main motor

※The extrusion volume suddenly drops:

1、Produce the cause:

1)Feeding system failure or no material in the hopper.

2)Extrusion system into the hard stuck screw, so that the material can not pass.

2、treatment methods:

1)Check the material level of feeding system or hopper.

2)Check and clean the extrusion system.