China’s injection molding industry boasts a complete industrial chain and huge production volume, with molds running under high-load, continuous operation in most domestic manufacturing workshops. Long-term cyclic opening and closing, high-pressure material injection, and alternating hot and cold working conditions will gradually cause wear, deformation and component failure. Combined with the actual production characteristics and daily maintenance norms of domestic injection molding enterprises, it is essential to master scientific judgment standards to distinguish routine minor repairs from comprehensive major overhauls. Timely arrangement of major overhauls can avoid mass defective products, unexpected production halts and excessive cost loss, and also extend the overall service life of molds.
Persistent Molding Defects That Cannot Be Fixed by Process AdjustmentThis is the most direct judgment standard in actual production. If common defects such as scorch marks, air holes and silver streaks keep appearing at fixed positions on finished products, and the problems cannot be eliminated after adjusting temperature, pressure, speed and other process parameters, cleaning vent grooves or replacing raw materials, it indicates structural damage inside the mold. Continuous flash and burrs on parting surfaces and inserts that recur after repeated trimming mean the parting surfaces have collapsed or suffered severe wear. In addition, drastic dimensional fluctuations of molded parts, deepening ejector pin marks and fixed scratches on product surfaces all prove that local damage has developed into irreversible faults, which can only be solved by full disassembly and major overhaul.
Abnormal Operation and Worn Moving ComponentsMoving parts are the most vulnerable parts of injection molds in domestic high-frequency production. If abnormal noise, stalling and increased resistance occur during mold opening and closing, and the situation cannot be improved after regular lubrication and cleaning, it usually means guide pins and guide sleeves have excessive gaps, scratches or surface coating peeling. Malfunctions such as bent ejector pins, unbalanced ejection and frequent pin breakage reflect severe wear of the ejection system. For sliding blocks and angle lifters widely used in complex domestic molds, jamming, incomplete reset and position deviation during operation will easily lead to mold scratching and part damage. Once these moving assemblies suffer overall wear, simple part replacement cannot restore normal operation, and a complete overhaul is required.
Loss of Dimensional Accuracy of Cavity and CoreCavities and cores directly decide the appearance and dimensional precision of plastic parts. After long-term use, if measuring tools detect surface pits, corrosion, dents and permanent deformation on key molding surfaces, and critical dimensions of products continuously exceed the tolerance range, the mold has lost its original precision. For multi-cavity molds commonly used in mass production in China, inconsistent dimensions among cavities and misalignment of mold inserts are typical signs of accuracy failure. Repeated local polishing and trimming fail to meet production requirements, so the cavity and core must be disassembled for grinding, correction and reassembly.
Malfunctions of Cooling, Gating and Sealing SystemsWater channels, runner systems and sealing structures are prone to cumulative faults in long-term production. Severe scaling, blockage and water leakage of cooling water lines will cause uneven mold temperature and product warpage. If conventional cleaning cannot restore the water circulation efficiency, or water seeps into the cavity to affect production safety, major maintenance is needed. Severe wear of main runners and gates, as well as material leakage at nozzle contact positions, will affect stable feeding. Aging and damage of sealing rings on oil cylinders and water channels that cannot be solved by single replacement also imply deformation of matching surfaces, requiring overall disassembly and repair.
Deformation of Main Mold Plates and Frequent FailuresDeformation of base plates, cavity plates and fixed plates belongs to serious mold faults. Uneven fitting of parting surfaces and loose positioning pins will cause overall displacement of the mold during production. Meanwhile, if the mold has passed its designed service life, or the frequency of failures and shutdowns rises sharply in a short period, with increasing time and cost spent on minor repairs, it means the overall operating condition of the mold has deteriorated. Under the high-intensity production mode of domestic workshops, such molds are no longer suitable for simple temporary repairs, and comprehensive overhaul and refurbishment must be arranged in a planned way to ensure stable and efficient production.
SummaryIn China’s high-volume and high-frequency injection molding production environment, distinguishing minor faults from irreversible overall damage is the core of judging mold overhaul. Isolated component damage and partial blockage can be handled by daily maintenance, while recurring molding defects, overall wear of moving parts, loss of precision of molding surfaces and deformation of main structures are clear signals for major overhaul. Reasonably arranging overhaul plans in accordance with relevant indicators helps control production risks, reduce comprehensive costs and maximize the service value of injection molds.
