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In summary, to achieve optimal physical and surface properties for plastic products, the material should be processed at the highest possible melting temperature without causing the plastic to burn. The plastic should be injected at a moderate, stable speed with the minimum necessary pressure to fill the mold details, then allowed to "relax" during the cooling phase.

Before Injection Molding 

• Clean both halves of the mold with an appropriate cleaning solution.
• Ensure all vent holes are thoroughly cleaned, free of rust inhibitors, dirt, or plastic residue.
• Check and fix any water leaks, ensuring full circulation of cooling water through the mold and machine.
• Clean and polish the sprue bushing; check for rough or uneven spots.
• Check the fit between the nozzle and the sprue bushing.
• Review the recommended mold temperature settings; if unavailable, consult the material manufacturer.
• Set the barrel temperature controller to the desired or recommended level.
• Reduce injection pressure, back pressure, and screw speed (RPM) to the lowest level within the allowable operating range.
• Check and readjust injection pressure, back pressure during purging or immediately after starting the injection cycle.

During Startup 

• Only introduce plastic into the machine after the barrel temperature has stabilized.
• Extrude the molten plastic and check with a handheld thermometer with a probe. Ensure the melt temperature is within the allowable range for each type of plastic; if not, adjust the heater band temperature, screw speed (RPM), or back pressure to achieve the appropriate temperature. Recheck the melt temperature once the machine has stabilized in production mode and maintain this temperature throughout production.
• Observe the state of the molten plastic flow during purging: a smooth surface indicates uniform melting; smoke or bubbles suggest excessive plasticizing temperature; the ability to draw into thin strands is a good sign of quality molten plastic; brittleness indicates low melting temperature; foam or vapor may be a sign of moisture in the material.
• Gently inject into the mold core, mold cavity, and sprue bushing, then start the injection molding cycle.
• Operate components in semi-automatic mode when starting molding.
• Check and adjust injection pressure; start at a medium level.
• Check and adjust injection speed; start at a slow to moderate level, then increase or decrease as needed.
• Adjust holding pressure and time to achieve acceptable product quality.
• Adjust screw rotation speed and back pressure to achieve optimal melt temperature.
• Check if the heating zones are overheating and if the settings are accurate.
• Mold temperature should be checked with a handheld thermometer or surface probe.
• Refer to troubleshooting guides during the injection molding process to resolve issues.
• If the sprue bushing is damaged, do not attempt to inject plastic through this component as it may cause heat loss and degrade the plastic.
• Continuous purging is required if the machine is idle for more than 15 minutes.
• Refer to the cleaning and shutdown procedure to properly maintain the mold after the molding shift.

Plastic pellets are prone to degradation when exposed to high temperatures for extended periods. Therefore, if the injection molding cycle is interrupted, the injection unit should be retracted from the mold and the plastic purged from the barrel regularly using the purging operation. If the interruption is prolonged, the plastic in the cylinder should be completely purged using recycled ABS or acrylic.

At the end of the production shift, do not stop the injection molding machine while plastic remains in the barrel — the plastic must be completely purged from the barrel using a suitable cleaning material.

The injection unit (barrel) of the injection molding machine should never be left in the forward position (against the mold) when the machine is idle. If the plastic overheats in the barrel, both the screw and barrel need to be cleaned. If the situation is not severe, it can be addressed by purging the barrel with acrylic or ABS at a very low temperature — this "cold" plastic will scrub the barrel clean and remove the degraded plastic. If this method is ineffective, the screw should be removed from the barrel and cleaned mechanically.

In the event of a power outage during molding and the plastic cools and solidifies in the barrel, a special restart procedure should be applied when power is restored. Initially, turn on the heater bands at a low temperature, about 93–121 °C (200–250 °F), and maintain this level until the plastic in the barrel has sufficient time to reheat. Then gradually increase the set temperature to slightly below the normal operating temperature. As soon as the machine reaches this temperature, manually operate the screw; as soon as the plastic begins to move, increase the temperature back to the normal operating level. Then purge the remaining plastic from the barrel using one of the recommended thermoplastic cleaning materials. At this point, production material can be reintroduced into the barrel and production resumed.

Do not mix polyethylene or polypropylene with vinyl (synthetic resin containing polyvinyl chloride or related polymers, commonly used for faux leather, coatings, and records), and they should not be used as cleaning materials. Flame-retardant materials should not be used for cleaning as they are prone to degradation.

Care should be taken to minimize the risk of rust and corrosion when storing molds. Molds should be sprayed with a commercially available neutralizing solution to neutralize any residual acid, then dried and sprayed with rust inhibitors, lubricants, or specialized mold cleaning solutions. At the end of each workday or before a weekend break, a commercially available mold protection solution should also be sprayed on the mold core and cavity. This temporary protective layer will easily flake off during the first few molding cycles thereafter.

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