During long-term production, key areas of injection molds, including cavities, cores, gates, slides, inserts, and parting surfaces, are prone to scratches, galling, wear, corner collapse, and erosion. Improper repair can reduce mold life and product quality. This article introduces practical, field-applicable repair methods for different levels of mold steel wear.

Wear Classification and Mold Steel Identification

Minor wear includes surface galling, fine scratches, and reduced gloss without obvious dimensional loss. Moderate wear shows local corner collapse, small-area defects, and increased fitting clearance, causing flash, dimension deviation, and sticking. Severe wear involves large-area damage, cavity collapse, corner breakage, and functional failure. Identify mold steel type, as pre-hardened steels are weldable while quenched steels require preheating to prevent cracking.

Repair for Minor Wear

Polish with oilstones and sandpapers from coarse to fine, then polish with diamond paste to restore surface finish. For improved performance, apply surface strengthening treatments such as nitriding, PVD coating, or chrome plating to enhance wear resistance and reduce sticking. This method is low-cost, fast, and does not change dimensions.

Repair for Moderate Wear

For local corner collapse, small chipping, and flash on parting surfaces, welding repair is the most common solution. Use laser welding, cold welding, or argon arc welding with welding wires matching the base material. Preheat quenched steels before welding and cool slowly afterward to avoid cracking. After welding, machine, grind, and polish to restore dimensions and surface quality.

Repair for Severe Wear

For large-area wear, repeated welding deformation, or serious corner breakage, insert replacement is the most stable solution. Machine the worn area into a regular shape, manufacture a new insert with matched or better material, and assemble it tightly. After fitting and polishing, the mold can resume stable long-term production.

Repair for Matching Surface Wear

For slides, wedges, guide blocks, and ejector pins, focus on re-grinding and clearance adjustment. Restore flatness and perpendicularicity, add gaskets if clearance is excessive, and apply nitriding for better wear resistance. Proper fitting ensures smooth movement and stable dimensions.

Post-Repair Protection

After any repair, apply surface strengthening such as DLC coating, nitriding, or polishing to extend service life. Regular cleaning, proper lubrication, and rust prevention during production can further reduce wear and maintenance frequency.