Routine Anti-Rust Maintenance Procedure for Injection Molds in Workshop
Rust formation on injection molds frequently occurs during intermittent production or long-term storage. Once cavities, parting surfaces, guide pins and inserts develop rust, molded parts will suffer surface scratches and excessive flash, moving components may seize up, and permanent precision loss will occur on molds. Daily anti-rust management cannot be simplified to spraying anti-rust oil when production stops. Three classified maintenance modes are formulated for in-production molds, temporarily-idle molds and warehoused molds, paired with environmental control and periodic inspection. This system eliminates rust risks while preventing grease contamination on plastic products, balancing production cleanliness and mold protection effects.
1. Daily Anti-Rust Maintenance for Molds in Mass Production
Molds running continuous production do not need full coating of anti-rust grease, and the core work lies in moisture isolation and instant dehumidification. Every time production halts for more than two hours, dry compressed air is applied to blow away water vapor and residual moisture inside parting surfaces, cavities and vent slots, and condensed water at cooling water connectors must be wiped dry to prevent rust spots caused by water seeping into steel surfaces during cooling cycles. Neutral release agents are adopted during production to avoid acidic agents corroding mold surfaces and generating pitting rust. Copper shovels and plastic scrapers are used to clear plastic residues instead of hard steel tools, preventing scratches on nitrided layers and polished surfaces which could become rust origins. After each shift, high-temperature anti-rust lubricant is added to moving positions including guide pins, guide sleeves and ejector pins, while only thin dry anti-rust spray is applied on cosmetic cavity surfaces. This method prevents rust caused by friction during mold opening and closing without contaminating plastic parts in subsequent cycles. When night shift production finishes, cooling water valves are closed and residual water inside pipelines is fully drained to stop moisture infiltrating template gaps and inducing rust growth.
2. Anti-Rust Process for Temporarily Idle Molds (Shutdown Period: 1–7 Days)
For molds remaining mounted on injection machines during standby period, simplified anti-rust operations are carried out. Firstly, plastic residues and moisture inside cavities and insert gaps are completely cleaned, and thin dry anti-rust agent is evenly sprayed on parting surfaces and inner cavity walls after full drying, with supplementary spraying applied on seal edges and narrow gaps. The mold is kept in half-clamped state, which avoids adhesion of anti-rust coating caused by fully closed parting surfaces and blocks humid air from entering cavities. The ground around injection molding equipment is kept dry to prevent rust erosion from evaporated ground water, and daily visual inspection is conducted before morning shift to check for water droplets and faint rust stains. Once dampness is detected, the mold shall be dried and re-sprayed with anti-rust agent immediately. Molds cannot stay open for a long time during standby, and desiccants are placed nearby in humid seasons to lower local environmental humidity.
3. Complete Anti-Rust Sealing Steps for Long-Term Warehoused Molds (Shutdown Over 7 Days)
Standard sealing procedures must be followed after molds are dismounted for long-term storage. First, all inserts, lifters and sliders are disassembled, cleaned of glue residues, oil stains and water marks, then dried in low-temperature oven to eliminate hidden moisture inside gaps. Different anti-rust materials are adopted for different mold areas: soft anti-rust grease is coated on polished cavity surfaces, hard-film anti-rust oil is sprayed on parting surfaces and large template planes, anti-rust butter is filled into guide pin sleeves, and dry cotton plugs are stuffed into threaded holes and process holes to block moisture invasion. After assembly, the mold is maintained half-opened and wrapped tightly with waterproof anti-rust plastic film, and large molds are packed into moisture-proof wooden boxes additionally. Molds are placed on moisture-proof pallets instead of directly contacting the ground inside warehouses, where humidity is controlled between 40% and 60% and temperature ranges from 18℃ to 26℃. Maintenance labels are attached after storage, marking anti-rust date and next inspection cycle to facilitate periodic recheck.
4. Supporting Environmental Anti-Rust Control for Workshop
Most mold rust originates from humid workshop environments, making environmental regulation the foundation of daily anti-rust management. Partitioned waterproof structures are installed in injection workshops, and thermal insulation cotton is wrapped around cooling water pipes to stop condensed water dripping onto molds. Standing water on the floor is cleaned every day, and dehumidifiers are turned on for overall dehumidification in rainy seasons with high humidity. Areas for mold storage are forbidden to place wet workpieces and water-based cleaning agents which may raise ambient humidity. Anhydrous alcohol and detergent are used for mold cleaning, and molds must be fully air-dried after cleaning instead of natural air-drying. Wet cleaning zones and mold storage zones are separated physically to prevent moisture diffusion leading to batch rust on molds.
5. Periodic Inspection Standard & Emergency Treatment for Rust Problems
An inspection ledger is established to implement recheck rules: in-production molds receive visual inspection every shift, idle molds are checked daily, and warehoused molds are sampled every two weeks to verify intactness of anti-rust film and mold surface condition. If faint surface rust is discovered during inspection, anhydrous alcohol and dust-free cloth are used to wipe off rust, followed by drying and renewed anti-rust treatment. Molds with extensive rust or deep corrosion pits need disassembly, polishing rust removal and re-nitriding repair, and can be put back into production only after passing precision inspection. Before taking molds out of warehouse for use, anti-rust coating must be thoroughly removed and cavities wiped and dried with alcohol; two trial shots are performed to confirm no residual grease before formal production, preventing oil contamination defects on plastic products. Records of inspection, rust removal and anti-rust operations are archived to build complete mold maintenance files.
Conclusion
Classified anti-rust management covers all working states of injection molds: in-production molds adopt moisture-proof and partial lubrication anti-rust schemes to guarantee production cleanliness, idle molds are protected by half-clamped state and dry anti-rust coating, and long-term stored molds undergo drying, layered anti-rust treatment and sealed warehousing. Combined with workshop humidity control and regular inspection systems, rust formation conditions are blocked from environmental, operational and inspection dimensions. Many molds suffer rust failure because workers apply thick anti-rust oil uniformly regardless of shutdown duration or ignore moisture removal. Implementation of this classified procedure can avoid cosmetic defects caused by anti-rust grease while protecting cavities, sealing surfaces and guiding structures effectively, cutting mold repair cost and extending overall service life of injection molds.
