The maintenance of injection molds is a crucial link to ensure production stability, product quality and mold lifespan. A scientific and standardized maintenance process can significantly reduce downtime and production costs.

The following is a detailed maintenance process for injection molds, which is generally divided into three main stages: daily maintenance during production, regular maintenance after shutdown, and long-term storage maintenance.

I. Daily Maintenance during Production
This is the preventive maintenance that operators and teams need to carry out within each production cycle.

Mold cleaning

Cleaning per mold/shift: Use an air gun, copper brush or cork sheet to clean the flash, oil stains and residual plastic at the parting surface, exhaust grooves, sliders and ejector pins, etc. Steel tools must not be used to avoid scratching the surface of the mold.

Gate sleeve cleaning: Inspect and remove the cold material inside the gate sleeve to prevent blockage or poor contact of the injection nozzle during the next injection.

Lubrication

Regular lubrication: According to the maintenance manual, apply appropriate special high-temperature grease or lubricating oil to the moving parts of the mold such as the ejector pins, sliders, inclined guide pins, guide pins and guide sleeves at regular intervals.

Note: Lubrication should be moderate. Excessive lubrication may attract dust or contaminate the product.

Function check

Moving parts: Observe whether the slider, inclined top, ejector pin, etc. move smoothly and stably, and whether there is any abnormal noise or jamming.

Cooling system: Check if there is any leakage at the joints of the mold’s cooling water channels. Touch the mold surface to feel if the temperature is uniform. If there is any abnormality, it may indicate that the water channels are blocked.

Exhaust system: Observe whether there are any burnt marks on the product and determine if the exhaust is unobstructed.

Ii. Regular maintenance after shutdown
When a production order is completed (usually recommended after 50,000 to 100,000 mold cycles, depending on the complexity and material of the mold) or when a decline in product quality is observed, the mold needs to be removed from the injection molding machine and sent to the mold repair workshop for deep maintenance.

The core process is as follows:

Step 1: Mold warehousing and evaluation
Record the mold number, production batch, the last produced product and the existing problems.

Conduct a preliminary inspection of the mold’s appearance and key dimensions.

Step 2: Mold cleaning and disassembly
Thorough cleaning

Use professional mold cleaning agents (such as solvent-based or water-based cleaning agents), in combination with ultrasonic cleaning machines or manual brushing, to remove all oil stains, plastic residues and rust.

For stubborn plastic and carbon deposits, you can use a special cleaning solution for plastic molds for soaking or wiping.

Disassemble with caution

According to the mold drawing or disassembly sequence, disassemble the detachable components one by one, such as sliders, inclined tops, ejector pins, guide pins, inserts, etc.

For complex molds, it is recommended to take photos or make marks to ensure that there are no errors during reinstallation.

Step 3: Inspection, repair and replacement
This is the core part of maintenance and needs to be completed by professional mold technicians.

Cavity/core surface:

Inspection: Use a magnifying glass to check the formed surface for rust, wear, scratches or fine cracks.

Treatment: For minor scratches, use oilstones of different grit sizes for grinding and polishing to restore the mirror surface. For rust and severe damage, electroplating repair or replacement of inserts is required.

Moving parts

Ejector pin system: Check whether all ejector pins and reset rods are bent or worn, and whether the ejector pin heads are damaged. Those that are severely worn must be replaced.

Slider and inclined top mechanism: Check the wear of the slider pressure plate and wear-resistant plate, inspect whether the inclined top rod is bent, and clean its guide groove.

Guide pins and guide sleeves: Check for any scratches or wear to ensure guiding accuracy. Those with excessive clearance must be replaced.

Cooling system

Water flow test: Connect pressurized water and check whether all waterways are unobstructed and if there is any leakage.

Descaling treatment: If the water flow decreases, it indicates that there might be scale inside. A mold waterway cleaning machine (through chemical agents or physical pulses) should be used to remove scale until the water flow becomes smooth again.

Exhaust system

Inspect and clean all exhaust channels. If the exhaust channels become shallower due to wear (usually with a depth of 0.02-0.04mm), they need to be reprocessed and deepened.

Replacement of vulnerable parts

Preventive replacement of parts that have reached the end of their service life or pose potential risks, such as springs, sealing rings, ejector pins, wear-resistant plates, etc. This is the key to avoiding unexpected shutdowns in production.

Step 4: Rust prevention and reinstallation
Rust prevention treatment

Evenly spray a layer of high-quality anti-rust agent on all processed surfaces (especially cavities, parting surfaces, guide pins, etc.).

Reassemble

Reassemble all the parts that have been cleaned, repaired or replaced in sequence.

During the assembly process, ensure that all screws reach the specified torque and that the moving parts slide smoothly.

Step 5: Mold testing and archiving
On-machine mold testing

Install the maintained mold onto the injection molding machine and conduct trial mold production.

Check the dimensions and appearance quality of the first batch of products and confirm that the mold functions have returned to normal.

Update file

Record in detail the date, content, replaced parts, mold test results and other information of this maintenance, update the “lifetime file” of the mold, and provide a basis for the next maintenance.