When plastic is added into the hopper, the hopper falls onto the screw, and as the screw rotates, it pushes the plastic towards the head, creating a mechanical conveying process. As the plastic advances from the hopper towards the head, the tread depth of the screw gradually decreases. Due to the manifold, screen, and heat resistance, high pressure is created during the plasticization of the plastic, compacting the material and improving its heat transfer. In contrast, the gradually increasing pressure causes the gas between the pellets to escape through the venting holes.
As the pressure rises, the plastic is heated externally, and the plastic itself is compressed, sheared, and stirred, generating a large amount of heat due to internal friction.
The host system of the plastic granulator is mainly the extruder, which consists of an extrusion system, a transmission system, and a heating and cooling system.
The extrusion system includes the screw, hopper, barrel, head, and mold, etc. The plastic is plasticized into a uniform melt when passing through the extrusion system, and the screw continuously extrudes this pressure.
1. Screw: The main component of the extruder, which is related to the range of applications and productivity, is high-strength and extremely corrosion-resistant alloy steel.
2. Barrel: a seamless metal tube of high heat and pressure resistance, strong, wear-resistant, and corrosion-resistant alloy steel. The barrel and the screw work together to crush, soften, melt, plasticize, exhaust and compact the plastic, and deliver the entire product to the forming system in a uniform and continuous manner. The length of the barrel is generally 18 times its diameter, and the plastic can be thoroughly heated and wholly plasticized.
3. Hopper: The bottom of the hopper is equipped with a cut-off device to adjust and cut off the material flow.
4. Head and mold: The head is made of alloy steel and carbon steel, and the director is equipped with a mold for forming.
Problem 1: Unstable primary machine current, uneven feeding, damaged main motor bearings, no heating, and other issues or failure of a section heater.
1.Check the feeder and replace the bearings if necessary.
2.Inspect the main motor and replace the heater if required.
3.Check that each heater is working correctly, pull the screw out, check for interference, and check the adjustment pad.
Problem 2: The main motor will not start.
Maintenance: driving sequence has a wrong, should check whether the fuse is burned ring; main motor thread has a problem;
Restart the machine in the correct driving sequence, check the series, check the primary motor circuit and check the status of the interlocking device associated with the main motor. Check that the lube oil pump starts. If the engine does not turn on, turn off the main power and wait 5 minutes before starting.
Problem 3: Poor or blocked material discharge from the head.
Repair: Possible causes are poor plasticization of the material, a section of the heater not working, or a low operating temperature setting, possibly a foreign object that does not melt easily, etc.
Replace the heater if necessary, in consultation with the craftsman. Verify the set temperature of each section; increase the temperature setting; clean the extrusion system and the head.
Correctly understand the working principle of the plastic pelletizer in order to properly use and maintain a good plastic pelletizer.
Plastic pelletizing machine extrusion shortage may be due to insufficient product injection, which often makes the material in the cavity is not full before the curing; of course, there are a variety of other reasons.
1. Temperature reasons: to improve the temperature of the barrel, nozzle, etc., check the millivoltmeter, thermocouple, and resistance electric heating ring or far-infrared heating device and heating system, improve the temperature, check the temperature control device.
2. Mould reasons:: small plastic granulator runners, small nozzle holes, unreasonable gate position, insufficient number of gates, too small cold material cavities, insufficient exhaust, etc., resulting in the injection cycle anomalies.
3. Equipment reasons: blockage of the hopper, insufficient filling volume, irregular operation of the filling control system, size of the plasticizing capacity of the injection press, equipment caused by the injection cycle anomalies.
4. Reasons for extrusion conditions: injection pressure of the plastic granulator is too low, the injection pressure loss in the extrusion cycle is too large, injection time is too short, full pressure injection time is too short, injection rate is too slow and other operating conditions caused by the injection cycle anomalies.
1. the presence of foreign bodies that do not melt easily.
2. poor plasticization of the material due to a section of the heater not working.
3. The operating temperature setting is low, or the plastic has a wide and unstable molecular weight distribution.
1. Check the heater and replace it if necessary.
2. Check the extrusion system and the machine head.
3. Verify the set temperature of each section of the heater and, if necessary, increase the temperature setting in consultation with the process operator.
Plastic pelletizing machine mainframe does not roll, or instant stop caused by this fault may generally be the main electric power supply is not connected, or heating up the temperature of the time is enough, or one of the heaters does not work, which leads to excessive torque makes the electric idea overload.
1. Check the host circuit, whether there is a power supply, etc.
2. Check the temperature of each section to confirm the warm-up time of the preheat.
3. Check whether each heater is damaged or has poor contact, and one by one to eliminate.