Regular Maintenance Items and Cycle Standards for Injection Molds
Injection molds are core precision equipment for plastic molding production. The operating condition of molds directly affects product appearance quality, dimensional accuracy, production yield and overall mold service life. During long-term mass production, injection molds are continuously subjected to high temperature, high pressure, impact of high-speed melt and high-frequency opening-closing mechanical vibration, which easily leads to mold surface carbon deposition, wear of moving parts, increased fitting clearance, water channel blockage, seal failure and mechanism jamming. Frequent mold repairs, batch defects and premature mold scrapping occurring in most injection molding enterprises all stem from non-standard maintenance, unclear cycles and inadequate maintenance. Establishing a standardized, graded and periodic mold maintenance system can effectively reduce the probability of mold failure, extend mold service life, stabilize mass production quality and cut downtime maintenance costs. Combined with formal mold maintenance specifications in the injection molding industry, this paper systematically expounds graded regular maintenance items and standard cycle requirements for injection molds.
Daily Maintenance Items
Daily maintenance is the basic preventive maintenance work for each shift, which must be strictly implemented after shutdown and mold change of each shift. Fully clean the mold parting surface, cavity, core and exhaust grooves to remove plastic debris, oil stains, carbon deposits and dust impurities. Prevent hard residues from scratching the mold surface and avoid molding defects such as flash, indentation and short shot in production. Check the mold opening and closing action to ensure smooth and stable operation without jamming, abnormal noise or unilateral friction.
Confirm that guide pillars and guide sleeves slide smoothly without pulling damage or dry jamming. Conduct comprehensive inspection on the ejection system to ensure ejector pins, flat ejectors and ejector blocks reset accurately with reliable ejection stroke limit, and eliminate demolding defects such as whitening, cracking and product deformation. Inspect the connection state of water circuit joints to ensure smooth inflow and outflow without water seepage, dripping or pressure relief faults and keep stable mold temperature. Clean residual cold material and burnt material in main runner, sub-runner and gate to prevent hard waste from scratching the cavity surface. Complete handover records after overall mold cleaning to ensure the mold is ready for standby.
Weekly Maintenance Items
Weekly maintenance focuses on in-depth maintenance of mold moving mechanisms, lubrication systems and fastening structures. Conduct refined cleaning on cavity, core and exhaust grooves to thoroughly remove subtle precipitates, carbon deposits and oxide layers on the mold surface, and avoid molding defects such as gas marks, burning and foggy appearance caused by long-term accumulation of impurities. Apply special mold grease evenly to all friction moving parts including guide pillars, guide sleeves, angle lifters, slide rails and wear strips to ensure smooth sliding of mechanisms and reduce mechanical wear. Fully inspect the overall state of ejector springs and return springs, check hidden troubles such as fatigue deformation, elastic attenuation and fracture of springs, and prevent failures such as incomplete ejection, mold jamming and product deformation caused by spring failure. Recheck the fitting precision of parting surface and sealing position, repair slight wear, collapse and excessive clearance in a timely manner, optimize sealing effect through fine grinding and eliminate batch flash problems. For hot runner molds, focus on checking temperature control circuits and hot nozzle operation status to screen hidden troubles such as temperature deviation, material leakage and glue accumulation. Meanwhile, fully fasten mold fixing screws, clamping blocks and limit structures to solve mold displacement caused by screw loosening due to long-term equipment vibration.
Monthly Maintenance Items
Monthly maintenance belongs to intermediate in-depth maintenance, focusing on comprehensive detection and precision repair of mold accuracy, cooling systems and core-pulling mechanisms. Carry out high-pressure flushing and pressure holding test on the whole mold cooling water channel to clean scale, rust and sludge blockage on the inner wall of water channels, ensure unobstructed water channels and uniform cooling, and improve molding defects such as product shrinkage, warpage and dimensional fluctuation. Fully verify the precision of guiding and positioning systems, detect the fitting clearance of guide pillars and guide sleeves, positioning stops and matching precision of mold locking parts, screen hidden troubles such as partial wear, loosening and dislocation, and ensure accurate alignment of front and rear molds and stable high-pressure mold locking. Disassemble and inspect components of the ejection system, clean oil stains and carbon deposits in ejector pin gaps, correct the flatness of ejector pins, and replace worn, deformed and stuck ejection accessories in time. Carefully check the fitting clearance of slide and angle lifter core-pulling mechanisms and wear loss of wear parts, re-add lubrication and fine-tune fitting precision to solve problems such as stuck core pulling, glue scraping and displacement. Perform slight polishing repair on runner and gate of gating system to eliminate pulling marks, tool marks and burrs and ensure stable melt flow. Count the wear loss of vulnerable parts at the same time and prepare spare parts in advance to avoid sudden production shutdown.
Quarterly Maintenance Items
Quarterly maintenance is precision-repair maintenance for molds, applicable to medium and high volume production molds, focusing on systematic hidden danger investigation and precision compensation repair. Conduct comprehensive grinding and repair on parting surface, sealing position and exhaust grooves, repair mold surface indentation, slight collapse and wear defects, recalibrate standard depth of exhaust grooves, and effectively improve quality problems such as gas trapping, burning, weld lines and batch flash of products. Fully detect the overall parallelism, mold opening and closing precision and insert fitting precision of the mold, re-align and lock loose and offset inserts to restore the original assembly precision of the mold. Thoroughly clean the whole cooling water circuit and replace aging water circuit sealing rings and waterproof rubber rings to eliminate water seepage, leakage and pressure relief faults and ensure accurate and stable mold temperature control. Detect the working state of hot runner heating coils, thermocouples and temperature control circuits, calibrate temperature deviation and replace aging and invalid accessories to ensure uniform and stable melt plasticization. Inspect the overall state of template stress surface and mold locking surface, screen hidden troubles of slight template deformation and indentation, guarantee the stability and safety of high-pressure injection mold locking. Complete trial mold test after maintenance to confirm all product quality indicators reach standards.
Annual Maintenance Items
Annual maintenance is the highest-level overhaul of molds, carrying out complete disassembly and overhaul for molds with continuous annual mass production and high-cycle molding. Completely disassemble the whole mold, clean, detect and repair all mold inserts, moving mechanisms and positioning accessories one by one. Fully renovate the surface of cavity and core, repair mold surface pulling damage, corrosion, wear and pitting defects, and restore the original finish and molding precision of the mold. Replace aging and fatigued accessories in batches, including springs, sealing rings, wear blocks, limit parts, ejector pins and other vulnerable parts to thoroughly eliminate various faults caused by accessory aging. Recalibrate all fitting precision, parallelism, verticality and alignment precision of the mold to restore the factory assembly standard of the mold. Carry out strengthening protection treatment on easy-wear areas and sealing areas of mold steel to improve the wear resistance and corrosion resistance of the mold. Sort out annual mold maintenance ledgers, loss records and maintenance records, update mold technical status, and provide reliable guarantee for subsequent stable mass production.
General Maintenance Specifications and Notes
Daily mold maintenance must strictly follow the five principles of cleaning, lubrication, fastening, correction and protection. Molds with faults and hidden troubles are prohibited to be put on the machine for production. For molds producing glass fiber reinforced materials and corrosive plastics, increase the frequency of cleaning and inspection to reduce mold wear and corrosion speed. All maintenance items must be truthfully recorded in ledgers, traceable with clear responsibilities to realize full life cycle traceability of mold status. Long-term idle molds need thorough mold surface cleaning, anti-rust spraying and sealed storage. Recheck anti-rust status regularly to avoid mold precision damage caused by rust. Standardized graded maintenance can effectively reduce mold failure rate, greatly extend mold service life, stabilize batch product quality, reduce mold repair cost and shutdown loss of enterprises, and serve as an important guarantee for lean production in injection molding workshops.
