Proper injection mold maintenance is essential for consistent part quality, minimizing unplanned downtime, and maximizing the return on tooling investment. This technical guide provides a structured maintenance program for plastic injection molds and rubber compression/transfer molds.

Daily Maintenance (Every Shift)

• Visual inspection of parting line surfaces for flash, damage, or contamination
• Check ejector pin operation for smooth travel and complete return
• Verify cooling line flow rates and temperature differentials (ΔT <5°C target)
• Clean cavity surfaces with approved mold cleaner (non-abrasive, non-chlorinated)
• Inspect O-rings and seals on hydraulic/pneumatic circuits for leaks

Weekly Maintenance

• Lubricate guide pins, bushings, and slides with approved mold grease
• Check and torque all bolts, clamps, and interlocks to specification
• Verify hot runner nozzle tips and gate condition (injection molds)
• Inspect venting channels — clean blocked vents causing burns or short shots
• Record shot counter and compare to preventive maintenance schedule

Preventive Maintenance Schedule

Common Problems & Root Causes

• Flash: worn parting line, insufficient clamp tonnage, or mold deflection — check parallelism and tonnage calculation
• Short shots: blocked vents, insufficient injection pressure, or low melt temperature — clean vents first
• Ejector marks: insufficient cooling time, oversized ejector pins, or misaligned ejector plate
• Burn marks: trapped gas from blocked vents or excessive injection speed — always address venting before adjusting speed