injection molding machine operation


False Injection molding machine operation will cause poor quality, rejected plastic parts, lessen machine life and the damaged screw. The following lists a detailed and comprehensive description of the standard process to avoid misbehavior.
A: Operational requirements

  • Before starting to heat the injection machine, switch on the cooling valve, observe waterway.
  • Switch the injection machine on, and then start the pump motor.
  • For the first use or longtime-unused machines, after pump start, injection machine run without molding cycle, then start the next operation.
  • Turn on the machine to heat the barrel, turn on the power to regulate thermostatic nozzle and temperature control on the door. Set the temperature; observe the ammeter current to verify the electric heating coil.
  • The test should start from manual, semi-manual to automatic, and check and assure the fastening bolts are tight, any abnormal occur should be immediately stopped. After confirmation of clear of troubleshooting, test again.
  • When production downtime and material exchange, the barrel should be cleaned under heated. After cleaning, turn off the heating power .cleaning work is particularly important for the processing decomposable plastic.
    ① When clean, injection seat should return.
    ② When change the plastic material, set the temperature from the requirements of high-melting materials
    ③ wash decomposition with polystyrene agent
  • 7. When the process stopped, firstly set machine to manual, The other operation is on the turned off position “OO”, turn off the barrel heating power and the pump motor, and finally turn off the power, all operation finish.

B: Caution

1. The steps should be taken before run the machine. First check the reliability of the security door. When the machine is running, hands should never be placed into the clamping mechanism. While remove products, always open the security door. Confirm the safety of personnel and tooling free of foreign material in, and then close the security door. In the operation, hands cannot be placed between the nozzle and the mold sprue. When mold need fix, pump motor must be switched off.

2. Due to variety of raw materials, different size and shape of the parts, the clamping force is different. When test mould, set the lowest clamping force, which not only save power, and significantly prolong machine life.

3. The hydraulic system pressure should be adjusted according to each operation separately. Rational pressure could not only save energy, but also prolong the life of the machine. The position of each limit switch should also be adjusted according to the requirements, especially for injection and packing switching point. Otherwise it would invite short filling, on the contrary, lead to excessive internal stress, flash and mold swells.
4. When there is no material in the screw or barrel, screw speed should be slow, preferably at 30 RPM or less. When the barrel is full and melt extrude from the nozzle, screw speed increases to the desired value, So as to avoid high-speed or long residual time to scratch screw or cylinder.
5. It takes about thirty minutes to increase barrel temperature from room temperature to the desired temperature. If residual cold material remains in the barrel, the time should prolong ten minutes and then start to could ensure that residual material is fully molten and avoid damage the screw.
6. Don’t change the safety valve in machine pumps.
7. After machine starts running and the cooling water temperature increases by 5C ° -10C °, and then gradually turns on the cooling water valve. During the operation, adjust the cooling water volume; keep oil temperature below 55C °. When starting cooler, quick valve opening is forbidden, for a large amount of cooling water flows through the cooler, it could lead to poor heat transfer “cold layer”. Even a large amount of water goes into the cooler, good cooling effect is still not achievable.
8. The machine lubrication. According to operational requirements, running in short of oil would badly wear parts, especially mechanical clamping rod and steel sleeve. Also it could invite the seizing of part.
9. As to the connecting screw rod in barrels and screws for plasticizing, for working under high temperature, it needs to be coated with heat-resistant grease (red lead or copper sulfide) to avoid seizing.
10. The clamping platen of the injection machine is with high precision; do not install plastic mold with bad mounting surface and the poor parallelism ,also bad screws is forbidden. All is to avoid damage the platen and clamping unit.
11. Don’t keep mold close over 10 minutes under the clamping pressure to avoid the linkage pin and steel sleeve to be short of the oil, which may make the mold couldn’t open.
12. Keep surface cleaning of moveable blocks.
13. in the end of each process:
① stop hopper feeding by hand, the injection seat retract and repeat pre-plastic feeding and injections, inject the remaining material inside the barrel as far as possible.
② set the “manual” mode, make the closed mold in a free state.
③ turn off the heating power, pump motor, main electric power and cooling water.
④ clean and maintain the plastic injection machine.
14. Electric heating coil may become loose for its expansion, check and assure it tight
15. Thermocouple probe should have good contact with the barrel thermometer hole. Before injection machine operation, the probe should be checked for tight.