Preventive Maintenance Guide for Injection Molding Machines

Daily maintenance tasks require approximately 15 to 30 minutes at shift start. These include checking hydraulic oil level and temperature (target 40 to 50 degrees Celsius during operation), inspecting safety guards and emergency stops, verifying cooling water flow and temperature at the mold inlet and outlet, cleaning the hopper and feed throat area, and reviewing the previous shift's process parameter logs for anomalies. Weekly tasks requiring 1 to 2 hours include lubricating all greasing points on the toggle mechanism and tie bars, checking hydraulic hose connections for leaks, inspecting the screw tip and check ring for wear by running a decompression test, and verifying all temperature controller readings against independent thermocouple measurements. Monthly tasks requiring 4 to 8 hours include full hydraulic oil analysis for contamination, viscosity, and acidity, inspection of the barrel heater bands and replacement of any showing hot spots, and verification of clamping force using strain gauge measurements.

The plasticizing screw and barrel are subject to progressive wear from abrasive PP additives, thermal fatigue from rapid heating and cooling cycles, and potential corrosion from moisture or contaminated feedstock. HWAMDA SPV5 screw diameters range from 50 to 65 mm with L/D ratios of 23:1 to 25:1, engineered for high-speed thin-wall processing. Key wear indicators that operators should monitor include increasing plasticizing time for a given shot weight, declining plasticizing capacity measured in grams per second, and growing shot-to-shot weight variation that was previously stable. The check ring (non-return valve) at the screw tip is the single most wear-prone component in the plasticizing unit, responsible for preventing backflow during the injection and packing phases. A worn check ring allows melt leakage backward during injection, reducing effective injection speed, shot weight consistency, and peak pressure delivery. The decompression test performed during weekly maintenance quantifies this leakage by monitoring pressure decay after injection hold. Check rings should be inspected every 3 to 6 months and replaced when measured leakage exceeds 5 percent of the target shot volume.

Valve gate hot runner systems in thin-wall molds require regular maintenance to ensure consistent gate quality and balanced filling. Nozzle tip inspection should occur monthly, looking for wear, buildup, or damage that affects gate vestige quality. Valve pin stroke and sealing should be verified monthly by checking gate mark quality on sample parts. Heater cartridge resistance should be measured quarterly; values deviating more than 10 percent from specification indicate impending failure. Thermocouple accuracy should be verified quarterly against a calibrated reference. Full hot runner disassembly and cleaning should be performed annually or every 2 to 3 million shots, whichever comes first. During full service, all valve pins, nozzle seals, O-rings, and heater cartridges are inspected and replaced as needed. Manifold flow channels are cleaned of any PP residue or degradation deposits. HWAMDA recommends maintaining a complete spare parts kit for each hot runner system. HWAMDA provides hot runner maintenance training as part of the turnkey line installation and commissioning program.

A well-planned spare parts inventory prevents extended downtime during maintenance or unplanned failures. For the HWAMDA SPV5 machine, critical spare parts include hydraulic oil filters (minimum 3 sets), screw tip and check ring assembly (1 complete spare), barrel heater bands (2 spare sets), and servo motor encoder (1 spare). For the mold, critical spares include valve pins (2 per hot runner drop), nozzle tips (2 complete assemblies), heater cartridges (4 spares per mold), thermocouples (4 spares), and ejector pins (1 complete set). For the SWITEK IML robot, spare vacuum cups, servo motor belts, and label magazine springs should be stocked. HWAMDA provides a recommended starter spare parts package with each machine delivery, sized for the first 12 months of production. Ongoing spare parts are available from HWAMDA's Ningbo warehouse with typical delivery time of 5 to 10 days for international orders. Remote technical support via WhatsApp and video call is available from HWAMDA's Ningbo engineering team for troubleshooting and parts identification.