Injection molds are the most critical precision production equipment in an injection molding facility. They directly determine the shape, dimensional accuracy, specification consistency, and surface finish of molded plastic products. Most injection molds on the market are manufactured from steel, with the core structure consisting of two halves: the front mold (fixed half) and the rear mold (moving half). As high-value precision assets, injection molds are characterized by three key attributes: application-specific design, high precision, and susceptibility to wear and damage. In daily production, most cases of mold damage, dimensional deviation, and repair or rework can be traced to inadequate protection, improper operation, or untimely maintenance. Therefore, establishing a standardized system for mold protection, repair, and maintenance is essential to ensuring stable product quality, reducing production costs, and extending mold service life.
1. Key Measures for Comprehensive Injection Mold Protection
Mold protection covers the entire process, from machine setup and production to machine stoppage, standby, storage, and transportation. Its primary purpose is to prevent precision damage caused by human error, equipment-related issues, and environmental factors. The industry’s key requirements for mold protection cover six areas.
Rust prevention is a fundamental part of mold maintenance. Leakage from mold cooling water, condensation in the workshop, exposure to moisture or rain, and sweat residue from operators’ hands can all cause the cavity, parting surfaces, and precision components to oxidize and rust. Minor rust can cause surface defects on products, while severe rust can directly compromise mold accuracy. The mold should therefore be kept dry and clean at all times, and rust-prevention treatment should be applied promptly when the machine is shut down.
Protection against impact is key to preventing severe damage. During production, a broken ejector pin, an ejector pin that has not fully returned, or incorrect movement of a slide or lifter can cause a collision during mold closing, directly damaging the cavity or precision components. Before starting production, all moving mechanisms must be confirmed to have returned fully to their proper positions. Mold closing under abnormal conditions must be strictly prohibited.
Preventing burr-related mold damage requires standardized daily operation. Many scratches and burrs on mold surfaces are not caused by production wear, but by improper cleaning operations afterward. Hard wiping with cloths, high-pressure material flow, rubbing with bare hands, impacts from sprue cutters, and hard scraping with tools can all damage the mold’s mirror-polished surfaces and the accuracy of the parting surfaces. Dedicated tools and proper operating methods must therefore be used for routine cleaning.
Protection of the completeness of mold components and accessories cannot be overlooked. Missing tie bars, washers, locating bolts, limit components, and other auxiliary parts can cause deviations in mold assembly clearances and uneven force distribution. During long-term mass production, this can lead to mold deformation, structural loosening, and positioning failure, gradually causing irreversible damage. The completeness of components and accessories must therefore be checked every time the mold is installed on or removed from the machine.
Protection against cavity compression damage is a key focus of ongoing control. If mold opening and demolding are incomplete, or if residual material, scrap, or product fragments remain in the cavity and are not cleaned out before mold closing, the cavity and core can be directly compressed, resulting in serious failures such as mold collapse, compression damage, and chipped edges. This is one of the major causes of mold scrapping.
Machine parameters for low-pressure protection must be precisely matched. If the pressure setting for the injection molding machine’s low-pressure protection is too high, the machine will be unable to stop and release pressure promptly when foreign objects, sticking, or obstruction occurs during mold closing, causing the low-pressure protection to lose its intended function and ultimately resulting in mold compression damage. The low-pressure parameters must therefore be reasonably matched according to the mold specifications.
According to industry operation and maintenance statistics, the three types of problems—ejector pin return failure, residual material not removed from the cavity, and missing mold components and accessories—account for more than 85% of mold damage. These problems occur frequently, have high repair costs, and can easily result in production downtime and lost production time, making them key risk-control points in injection molding workshop mold management.
2. Intelligent Protection: The Application Value of Mold Protection Systems
Manual inspection has problems such as blind spots, fatigue-related oversights, and judgment errors, and cannot completely avoid the risk of mold compression. To address the shortcomings of traditional manual protection, the industry relies on machine vision technology and has widely adopted mold protection systems (mold monitors/camera-based mold protection systems).
This equipment is compatible with all types of injection molding machines and can automatically perform high-precision inspection during every molding cycle. Before mold closing, it identifies abnormal conditions in real time, including residual material in the cavity, products that have not been ejected, misaligned slides, and ejector pins that have not returned. Once a risk is detected, the system immediately stops the mold-closing operation and triggers audible and visual alarms, forcibly preventing the hazardous operation.
Mold protection systems can prevent mold compression, mold crushing, and mold collision caused by human negligence, comprehensively protecting high-precision, high-value molds, significantly reducing repair costs and downtime losses. They are standard equipment for mold protection in modern injection molding workshops.
3. Standardized Repair Procedures for Injection Molds
Mold repair is a precision operation. Secondary damage must be avoided throughout the entire process, so standardized procedures must be strictly followed.
During disassembly and transportation, the mold must be placed down gently and handled properly. Impacts and dropping are strictly prohibited. The mold must also be protected against water to prevent water from entering the mold structure and causing rust. During the repair and adjustment stage, a small amount of mold release agent can be evenly sprayed onto the preheated mold to optimize molding conditions and assist with production adjustment.
At the end of the repair process, the cavity, core, ejection system, slides, parting surfaces, and other key structures must be thoroughly cleaned. Water must be completely wiped off, and residual material and debris must be removed. Complete rust-prevention maintenance must also be carried out by spraying a dedicated rust preventive for molds and evenly applying grease to key moving components and mating surfaces. This ensures that the mold is in good condition after repair and can be directly reused or stored for a long period.
4. Tiered Injection Mold Maintenance System
During long-term continuous mass production, molds continuously experience mechanical wear, lubricant aging, deposits in cooling channels, material compression damage, and other problems. Routine maintenance is the key means of maintaining mold accuracy and extending mold service life. The industry divides mold maintenance into two main systems: routine maintenance and deep maintenance after mold removal.
Routine preventive mold maintenance focuses on frequent basic maintenance. The workshop should regularly remove rust from and clean the mold exterior, parting surfaces, cavity, and core to keep the precision surfaces of the mold clean and intact. Lubricating oil and grease should be regularly added to moving components such as the ejection mechanism, slides, and lifters to reduce mechanical friction and wear. Tie bars, bolts, springs, and other wear-prone components should be inspected periodically, and aging, deformed, or failed components should be replaced promptly to ensure stable mold operation.
Deep maintenance after mold removal is professional-level maintenance and must be performed by professional mold maintenance personnel after the mold is removed from the machine. Comprehensive inspection, adjustment, repair, and protection should be carried out for key aspects, including cavity accuracy, coordination of ejection movements, fitting clearances of core-pulling structures, cooling-channel flow, and sealing performance. Hidden faults and potential problems should be thoroughly identified to restore the mold to its optimal molding accuracy and operating condition.
END