Daily Maintenance Process and Notes for Plastic Molds
Plastic molds belong to high-precision forming equipment. The mold status directly determines the appearance quality, dimensional accuracy of plastic parts and mold service life. During injection production, high-temperature melt, exhaust carbon deposition, raw material corrosion and reciprocating mechanical friction will continuously wear the mold cavity and moving mechanisms. Without standardized daily maintenance, scratches, rust, wear and mold jamming faults are easy to occur, causing shutdown, batch bad products and high mold repair cost. Establishing standardized daily maintenance process and implementing pre-shift, mid-shift, post-shift and long-term shutdown maintenance can stabilize production status, extend mold service life and reduce comprehensive project production cost.
1. Pre-shift mold inspection points
Before each injection production, complete basic mold inspection to eliminate potential risks in advance. First check the mold appearance, confirm no rust, scratches or residual glue on the cavity and parting surface, check the surface status of thimbles, sleeves, sliders and angle lifters to confirm no deformation or jamming. Check cooling water pipe joints to see whether the water pipe is aging, leaking or blocked. Water circuit leakage will cause local mold rust and unstable mold temperature. Check whether exhaust slots are blocked by carbon deposition, and whether guide pillars and guide bushes lack lubricant. Confirm all fastening screws are not loose and positioning pins do not slip out. After inspection, apply high-temperature grease suitable for sliding surfaces of guide pillars, guide bushes and sliders to avoid dry friction during mold opening and closing. Complete empty mold opening and closing test to confirm stable movement without abnormal noise or jamming, and then carry out feeding trial production.
2. Mid-shift inspection and maintenance during production
After the mold enters mass production, maintenance shall not be carried out until faults occur. Timely patrol inspection is required. The patrol inspection focuses on observing mold opening and closing movement, paying attention to abnormal signals such as abnormal noise, vibration and difficult ejection. Stop the machine for troubleshooting immediately once abnormality is found. It is forbidden to continue production with faults. Observe product status regularly. If flash suddenly increases or product scratches appear, it is likely that the parting surface or cavity is worn, stop the machine for inspection in time. During production, plastic decomposition products and release agent residues will continuously accumulate in exhaust slots. Clean carbon deposition in exhaust slots regularly according to raw material types to prevent continuous occurrence of trapped gas defects. For easily corrosive plastics such as PVC and flame retardant materials, increase patrol frequency, clean decomposition residues on cavity surface in time to prevent chemical corrosion on mold surface. Continuously monitor the temperature of cooling water circuit. If the water outlet flow becomes smaller, judge that the water circuit is scaled and blocked, and arrange water circuit dredging during shutdown.
3. Post-shutdown cleaning and maintenance
Maintenance after single production task is the core link of the whole maintenance process. After shutdown, clean residual glue on cavity, parting surface, runner and gate first. Use soft tools such as copper knives and bamboo chips for cleaning. Steel tools are forbidden to scrape the mold surface directly to prevent scratching the polished surface. After cavity cleaning, blow off dust and debris in mold gaps with air gun and dry surface water stains. After cleaning, reapply high-temperature lubricating grease to moving mechanisms such as guide pillars, guide bushes, sliders and angle lifters to ensure smooth mold opening and closing next time. Check the fit clearance of inserts and thimbles and record wear conditions. If the mold will not be on the machine in the short term, spray special anti-rust agent on cavity and parting surface, close the mold, and fill in maintenance records with mold number and mold status. After all maintenance operations are completed, fill in maintenance ledger, record production quantity, mold status and abnormal problems found.
4. Regular deep maintenance operation
In addition to daily basic maintenance, molds need periodic deep maintenance according to production quantity. Generally, after tens of thousands of shots, remove the mold from the injection machine for full disassembly maintenance. After disassembly, inspect cavity surface wear and polishing layer status one by one, repair tiny scratches and collision damage, grind and trim exhaust slots, clean scale and impurities inside water circuit to ensure smooth cooling circulation. Check spring fatigue. Deformed and fatigued ejection springs shall be replaced directly to avoid ejection failure. Detect the wear clearance of guide pillars and guide bushes, and replace the fittings when the clearance exceeds tolerance. Check the aging status of sealing rings and water pipe joints, and replace aging accessories in advance. Reassemble after deep maintenance, repeatedly test empty mold opening and closing, confirm all mechanisms work normally, and make maintenance records again.
5. Maintenance points for long-term mold storage
When molds are stored offline for a long time, improper protection is easy to cause rust and loss of parts. Thoroughly clean all cavities and runners, spray sufficient anti-rust agent, fully lubricate moving parts and close the mold. Protect the outside of the mold, place it on a dry and ventilated mold shelf, carry out moisture-proof treatment on the ground, and keep away from water vapor and corrosive gas. Supporting accessories such as inserts, thimbles and spare springs are uniformly stored in special accessory boxes and stored together with the mold. Recheck every two to three months during storage, supplement anti-rust agent and check for rust return. Handle molds gently during lifting and transportation to avoid collision on cavity and precision sealing positions.
6. General notes for mold maintenance
Maintenance operators need to be familiar with mold structure and select tools and consumables in standard operation. Matching anti-rust agent and lubricating grease shall be selected for different working conditions and shall not be mixed. During production, it is forbidden to knock hard objects directly on the mold cavity surface, and plastic parts cannot be pried forcibly during demolding to prevent mold cavity corner chipping. If the mold has abnormal faults, do not carry out welding and polishing privately. Professional mold personnel are required to evaluate the maintenance scheme. When producing plastic parts of different materials, the focus of maintenance needs adjustment. The cleaning and anti-rust requirements after production of corrosive plastics are much higher than ordinary plastics. All maintenance records are continuously retained to form the full life cycle file of the mold, which is convenient for evaluating mold loss status in the follow-up and planning maintenance in advance.
Summary
Daily maintenance of plastic molds runs through pre-machine, in-production, post-shutdown and long-term storage stages. Basic inspection, real-time patrol inspection, cleaning and lubrication and regular deep maintenance are all indispensable. Standardized maintenance operations can reduce mold faults such as scratches, rust and jamming, reduce shutdown maintenance frequency, stabilize molding quality of plastic parts, and effectively extend mold service life. Complete maintenance ledger can track mold loss status, predict hidden dangers in advance, reduce comprehensive cost brought by mold maintenance and replacement, and ensure continuous and stable injection production.
