Eight major considerations for annual mould overhaul

1. Look for warning signs of rust or dampness at the air vents

　　If you find rust or moisture near the hot runner vents, it means internal condensation or a possible water pipe break. Dampness can cause a fatal short circuit to the heater. The chances of this condensation increase if the machine is not running all year round, but is switched off at night or at weekends.

　　2. Remember to remind the operator not to clean out the hot nozzle at the sprue

　　If the operator happens to see a small piece of stainless steel at the mould spout, it may in fact be a spot spout assembly. Removing this seemingly obstructive piece can often destroy the hot nozzle head. To avoid damaging the hot nozzle, check the nozzle type of the hot runner system before taking action and ensure that all operators are trained and can identify all the different types of nozzles they are dealing with.

　　3. Slip stops

　　This should be done once a week for machines that run all year round. The end of the year is a good time to give these parts a routine lubrication service.

　　4. Interactively calibrate the resistance of the heater

　　You should have measured the resistance of the heater when you first started using it, now is the time to measure it again and compare. If the resistance value fluctuates up or down by 10%, it is time to consider replacing the heater to ensure it does not fail at a critical point in the production process. If the initial resistance value has never been measured, take a measurement now and use the resulting value as reference data when checking the heater in the future.

　　5. Look for signs of wear between the guide pillar and guide bush

　　Look for signs of scratching or scuffing, which is due to a lack of lubrication. If the marks have only just appeared, then you can still extend the life of the guide pillar and guide bush by giving them more lubrication. If the wear is already severe, then it is time to replace the parts with new ones. Otherwise, the cavities and cores may not fit together well, resulting in inconsistent wall thicknesses.

　　6. Check the water flow

　　Connect a hose at the water outlet and let the water stay in the barrel through the hose. If the water is not clear or has a colour, rust may be present, while a poor flow of water means a blockage somewhere. If you find these problems, re-drill all the hoses to ensure that they are clear (or clean them by whatever method you are most comfortable with). Improving your plant's water treatment system will prevent future problems caused by rust and blockages.

　　7. Cleaning the thimble

　　Over the course of a year, ejector needles can become dirty due to gas build-up and film-like impurities. It is recommended to clean the ejector pins every six to twelve months with a mould cleaner. After cleaning, apply a layer of lubricant to the ejector pin to prevent scuffing or breakage.

　　8. Check for fractures in the radius of the nozzle

　　Fractures are caused by loose pieces of hardened plastic left in the hot nozzle of the machine during forward injection from the gripping forces brought about by the injection cartridge assembly. The problem can also be caused by a misalignment of the centre line. Both of these possibilities should be considered when finding a break. If the damage has become too severe to prevent petal leakage (a term formerly used by mould users to refer to plastic leakage between the guide sleeve and the hot nozzle head of the machine), the gate sleeve should be replaced.