In the injection molding industry, molds are high-value precision production equipment. Maintenance quality directly determines part appearance, production stability, and mold service life. Many factories suffer from non-standard maintenance, arbitrary operations, and poor maintenance awareness. Operators often rely on outdated experience, leading to habitual incorrect maintenance practices. These errors not only fail to protect the mold but also cause rust, scratches, deformation, flash expansion, water leakage, and jamming, increasing repair costs and shortening mold life. This article summarizes the seven most common mold maintenance misconceptions, analyzes their hazards, and provides standardized corrective measures to guide workshop mold maintenance.
Ⅰ. Only Cleaning Visible Surfaces, Ignoring Dead SpotsMost operators only wipe parting lines and cavity surfaces, ignoring hidden areas such as vent grooves, runner corners, ejector pin gaps, and insert clearances. Over time, residual plastic smoke, carbon deposits, and powder accumulate, blocking vents and causing burn marks, short shots, and gas marks. Hardened carbon deposits scratch polished cavity surfaces, resulting in pitting on parts. Hidden impurities also cause poor parting line fit, leading to persistent flash. Dead spot cleaning is the most overlooked basic maintenance item and the most widespread misconception.
Ⅱ. Overusing Mold Release Agents
When encountering sticking or difficult ejection, many operators spray large amounts of release agents directly. Excessive release agents leave oily residues on the cavity surface, causing part fogging, oil spots, and poor adhesion, severely affecting appearance quality. Release agents penetrating the parting line attract iron filings and dust, enlarging mold closing gaps and causing permanent flash. Additionally, release agent chemicals are slightly corrosive, gradually eroding mold polish, reducing gloss and causing black oxidation spots. Correct practice requires optimizing draft angles and polishing to reduce reliance on release agents.
Ⅲ. Directly Clamping Molds During Shutdown Without Rust PreventionDuring daily shutdowns, shifts, or production stops, operators simply close and lock the mold without cleaning moisture or applying rust preventative. Injection molding workshops have high humidity and temperature fluctuations; residual cooling water in the mold causes rapid oxidation and corrosion. Rust spots on the cavity permanently replicate on parts, requiring polishing and reworking later, which sacrifices dimensional accuracy. Many cases of mold rust occur not from long-term storage but from neglecting simple daily shutdown rust prevention, making this a high-risk, easily overlooked misconception.
Ⅳ. Improper Lubrication and Incorrect Grease SelectionSome maintenance personnel use ordinary butter instead of high-temperature mold grease for guide pins, guide bushes, angle pins, and ejector pins. Ordinary butter performs poorly at high temperatures, carbonizing, caking, and attracting iron filings, causing mold opening jams, scratched angle pins, and stuck ejector pins. Excess grease dripping into the cavity also contaminates parts. Improper lubrication accelerates wear of moving components, reducing mold opening and closing precision and causing misalignment and flash.
Ⅴ. Operating with Minor Faults UnaddressedTo meet production targets, many workshops continue running molds with minor flash, ejector pin whitening, blocked vents, leaking water lines, or loose inserts. Minor flash pressed over time collapses the parting line, causing permanent flash; stuck ejector pins forced into operation scratch ejector pin holes; slight water leakage corrodes internal mold structures. Small faults left unaddressed escalate rapidly, leading to exponentially higher repair costs and even mold scrapping, making this the most costly misconception in production.
Ⅵ. Leaving Water Lines Filled with Water After ShutdownMany operators simply turn off the machine after production without draining water from the lines. Scale and impurities in the water attach to pipe walls, narrowing passages and reducing cooling efficiency, leading to increased part warpage and sink marks. Standing water also causes internal rusting of water lines, corroding plugs and seals and leading to severe leakage later. Many cases of mold cooling failure and uneven mold temperature are caused by failure to drain and clean water lines regularly.
Ⅶ. Rough Disassembly and Improper Tool Use
When disassembling molds or removing flash, operators often use screwdrivers, hammers, or blades to scrape the parting line. Hard tools easily scratch parting lines and nick cavity edges, causing permanent damage. Forcing inserts or ejector pins with blows enlarges clearances, leading to flash. Rough handling is a common bad practice in the industry and severely damages precision molds.
ConclusionMost mold maintenance misconceptions stem from habitual incorrect operations and poor maintenance awareness. Neglecting dead spot cleaning, overusing release agents, failing to prevent rust during shutdown, improper lubrication, operating with faults, leaving water lines full, and rough handling are the most common, high-search-volume misconceptions in the injection molding industry. Mold maintenance should prioritize prevention over repair. Standardizing cleaning, rust prevention, lubrication, water management, and disassembly procedures reduces mold wear from human error. Avoiding these misconceptions stabilizes part quality, reduces scrap rates, extends mold life, lowers maintenance costs, and improves overall production efficiency.
