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What aspects should you pay attention to during the inspection of injection molds?
- Sep 19, 2018 -

The repair procedures required for each injection molding location depend on the different mold cycle times. Below are some general guidelines that allow each mold user to ensure efficient operation of mold components such as hot runners, heaters, guide posts, and thimbles to prevent accidents.

1. Check for signs of rust or moisture at the air vents – if you find rust or moisture near the hot runner vents, it means internal condensation or a possible rupture of the water pipes. Humidity can cause a fatal short circuit to the heater. If the machine is not running all year round, but will shut down at night or on weekends, the chances of this condensation will increase.

2. Remember to remind the operator not to “clean up” the hot mouth at the gate – if the operator happens to see a small piece of stainless steel at the nozzle, it may be a point assembly. "Clean up" what seems to be a hindrance often ruins the hot mouth. In order not to damage the hot mouth, please confirm the type of mouth of the hot runner system before taking action, ensuring that all operators are well trained and able to identify all the different types of mouths that they are exposed to.

3. Sliding Stops – This should be done once a week for machines that run all year round.

4. Interactively verify the resistance of the heater – you should have measured the resistance at the beginning of the heater and it is time to measure and compare again. If the resistance value has a 10% up and down float, it is important to consider replacing the heater to ensure that it does not go out at critical times during the production process. If the initial resistance value has never been measured, measure it now and use the value obtained as a reference for future inspection of the heater.

5. Look for signs of wear between the guide post and the guide sleeve – look for signs of scratches or scratches due to lack of lubrication. If the traces just appear, you can extend the life of the guide post and guide bush by adding more lubrication. If the wear and tear is already serious, it is time to replace the new parts. Otherwise, the cavity and the core part may not fit well, resulting in a thin wall of the parts.

6. Check the water flow – connect a hose at the water outlet to allow water to pass through the water pipe to the bucket. If the water that flows out is not clear or has a color, there may be rust, and if the water is not smooth, it means that it is blocked somewhere. If you find these problems, drill all the water pipes again and make sure they are unblocked (or clean up by any method you use most often). Improving the plant's water treatment system will prevent future problems caused by rust and blockage.

7. Cleaning the thimble – After a year, the thimble becomes dirty due to gas accumulation and membranous impurities. It is recommended to clean it with mold cleaner every six to twelve months. After cleaning, apply a layer of lubricant to the thimble to prevent scratching or breakage.

8. Look at the radius of the hot nozzle for breakage – the fracture is caused by the clamping force from the plastic injection cylinder assembly when the loose, hardened plastic fragments remaining in the machine's hot nozzle are injected forward. The cause of the problem may also be that the centerline is not aligned.


Consider these two possibilities when you find a fracture. If the damage is so severe that it does not prevent the appearance of a petal-like leak (a term used by mold users in the past: a plastic leak between the guide sleeve and the hot mouth of the machine), the sprue bushing should be replaced.