Analysis of Common Faults and Causes of Screw and Cylinder of Extrusion Blow Molding Machine in Use
|Fault phenomenon||Reasons and troubleshooting|
|There is a scratching sound during operation||1. The center line of the barrel is bent to adjust the center height of the barrel 2. The barrel and the screw are not the same, check the position and position accuracy error of the relevant parts 3, the cylinder inner wall or screw outer diameter cylindricity accuracy is not enough, check and replace 4. Screw distortion, check and replace|
|Local overheating near the connection between the barrel and the gearbox||1. The barrel and the screw are not the same, check the position and position accuracy error of the relevant parts 2. Local deformation of the screw, check and replace.|
|Screw feed is unstable or not feeding||1. The barrel inlet is not well cooled, check the maintenance cooling waterway 2. The screw feed port is blocked by blockage, check and clear the blockage and block. 3. The barrel feeding section is not slotted or worn seriously, check and replace the barrel 3. Screw feed section is damaged, repaired or changed|
|During the operation, the temperature of the screw metering section is too high.||1. The barrel temperature control or cooling fan is bad, check the temperature control and cooling fan|
2. The barrel screw is seriously worn, repaired or changed 3. The head resistance is too large, check and repair 4. Screw structure design is poor, modify the design
|The barrel screw wears too fast and the extrusion volume is reduced.||1. Excessive impurities in raw materials, reducing impurities 2. The barrel screw heat treatment hardness is not enough, check the material or heat treatment process 3. The raw material formula contains a large proportion of filler|
Cause Analysis and Technical Measures for Abnormally Locked Screw of Extrusion Blow Molding Machine
Foreign matter jamming in the extrusion blow molding machine In the hollow blow molding production process, metal objects are often dropped from the feed port due to improper operation of some operators or accidental damage of the feeding and returning crushing system equipment. Most of them are screws or nuts. This kind of metal object is pushed forward with the plastic, and is stuck in the gap between the screw and the barrel. In this case, abnormal mechanical friction sound is often emitted, but due to the large operation sound of the equipment in the production workshop, the operator often It is difficult to find such an abnormal sound in time, causing the screw to further operate until the extruder equipment is completely stuck, and in severe cases, the equipment of the extruder drive system is accidentally damaged.
Although the manufacturer of the extrusion blow molding machine installed a magnetic frame in the extrusion blower feed hopper, the stainless steel diamond block still enters between the extruder screw and the barrel because the stainless steel material is not affected by the magnetic force. And directly caused damage to the screw and barrel.
Therefore, a strong magnetic iron device is installed in the feed hopper or other suitable parts of the extrusion blow molding machine, and the plastic raw material is transported by the negative pressure, so that accidental damage of at least 80% can be reduced. At the same time, materials such as plastic trim materials cut during the operation need to be taken to prevent contamination and ensure the cleanliness of the raw materials.
At present, there is a metal automatic separation device on the market, which can be used to separate metal particles in plastic raw materials, etc., and has a good effect on reducing the metal seizure phenomenon of the screw and the barrel.
Screw and barrel are abnormally locked. In the normal production operation of the extrusion blow molding machine, there may be an impression that the screw and the barrel are locked. The reason is often because the main part of the extruder is screwed or It is the internal connection sleeve and other parts processing and heat treatment that have not met the relevant technical requirements. The gear reducer thrust bearing wear and damage (normally, if the equipment in normal use does not have hardware blockage, it should first be suspected that the thrust bearing of the reduction gearbox is damaged) or There is still room for improvement in the extruder design itself.
In the disassembly and repair, the lock can be locally heated to about 300 degrees, and some special tools are used for disassembly. When disassembling, special attention should be paid to safe operation to prevent the tool from being broken and accidental. After disassembly, the damaged parts of the parts can be properly trimmed and then used. If necessary, the completely damaged parts can be replaced and the gear reduction box can be repaired.
THREE: Screw and barrel replacement time selection
For the extrusion blow molding machine, the university work of the screw barrel determines the output and production efficiency of the blow molding equipment. After a period of use, the screw barrel must be worn, especially with more return materials. When the mineral filler is filled, the wear of the screw barrel is accelerated. When the wear reaches a certain amount, it will affect the working efficiency of the equipment; this is to replace the screw barrel in time. Because the output of the screw barrel will decrease after the wear of the screw barrel, the output will decrease in the unit working time, and the energy consumption will not decrease. Sometimes the energy consumption will increase, the unit consumption of the product energy will rise rapidly, and the production cost will increase. The benefits are reduced.
Since the screw is tightly operated in the barrel, it is difficult to directly observe the wear condition of the screw barrel, but it can be determined whether the screw and the barrel have been worn out by the following changes, and whether it needs to be replaced. .
1 Check whether the temperature at the front end of the feed section of the extrusion blow molding machine is normal, usually in the 1-2 section of the temperature control zone of the extruder. If the temperature control of these sections has started to run out of control, the temperature rises faster and takes cooling. It is also difficult to cool down the measures. Then, it is necessary to replace the screw and the barrel as soon as possible.
2 In the case of normal production, (the raw material formula, process parameters, product specifications, etc. have not changed), the output has decreased by more than 5% due to the decrease in extrusion volume, and it is impossible to stabilize the original shift output by taking other measures. Need to replace the screw and barrel as soon as possible. Because the class output drops by 5%, if it is not replaced as soon as possible, it will soon drop to more than 10%.
Since the material of the screw and barrel of the extrusion blow molding machine is generally 38CrMoAlA, the welding performance of this material is poor, and the repairing method can be used in the repair. The ordinary repair welding method is difficult to guarantee the screw screw edge. The strength of the screw, if the screw is cracked during the operation of the screw, may directly cause damage to the machine head, which may cause damage to more parts.
FOUR：Screw and barrel removal
1 After heating the joint between the screw and the storage cylinder head to a temperature higher than the normal process temperature, the plastic material in the barrel is basically squeezed out, the bolts at the joint are removed, and the heater and wiring are disassembled; The cooling water pipe of the material section, disassemble the automatic feeding device; remove the extruder motor and wiring.
2 Loosen the fastening bolts connected to the feeding section, remove the gearbox coupling and the connecting bolts with the frame of the equipment, and retract the gearbox. The gearbox has a heavier weight. The hydraulic jack can be used to push the gearbox out. After that, it is disengaged from the screw; if the screw and the connecting sleeve are tightly connected, a special screw removal tool can be installed on the other side of the gear box connecting the screw head during the ejection process to push the screw out; After the box connection sleeve is completely disengaged from the screw, the reduction gear box can be lifted off the equipment rack.
3 The drum is smoothly hoisted together with the screw. For the large screw, the lifting of the barrel can be smoothly hoisted by the method of the crane and the workshop. Pay attention to the mutual movement coordination when lifting.
4 Warm up the suspended cylinder and disassemble the relevant connecting parts and screws. At present, most of the general blow molding manufacturers adopt replacement parts repair, and the prepared spare screws and barrels can be prepared for lifting after the relevant connecting parts are installed.
FIVE：Screw and barrel installation
1 The spare screw can be hoisted after being installed together with the barrel. In order to prevent the screw from sliding in the barrel, a small piece of wood can be clamped between them; then it is smoothly hoisted at the position of the original barrel, and the barrel is fixed, and Connected to the stocker head and the feed section.
2 Lift the gearbox back to the equipment rack, align the gearbox sleeve with the screw keyway end and connect it in place. When connecting here, you need to use special screw to remove the installation tool. The connecting sleeve and the screw keyway end need to be applied. Grease for future disassembly; install and tighten the fixing bolts of the frame and the reduction gear box, install the fastening bolts of the feed section and the reduction gear box, install the extrusion motor and the coupling and wire, install the heater and wiring .
3 Install the automatic feeding device, carefully check the various wiring and connecting bolts and then pressurize the test.
4 The gearbox needs to be replaced with grease to take advantage of this opportunity to change the oil, and also to check and maintain the extruder motor.
SIX：Safety precautions in screw and barrel disassembly
Due to the heavy weight of the screw and barrel of some large and medium-sized blow molding machines, it can reach 2-4T, and the blow molding manufacturer’s driving may not meet the lifting weight. In this case, the equipment can be combined with the vehicle and the driving. Lifting of parts. Pay special attention to the smoothness of the equipment components during lifting, and the lifting speed should not be too fast; the objects for lifting need to be reliable and safe. When hoisting, it is necessary to supervise and coordinate the speed of driving and cranes by special personnel to ensure the smooth lifting of equipment components. Lifting items such as wire ropes, lifting rings, etc. cannot be slid with the suspended parts, and the connection must be reliable and safe. Operators and other field personnel cannot stand under the suspended objects and cranes and prevent accidents.
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