Introduction
For customers of injection molds, the ideal mold is one that lasts as long as possible. However, every injection mold has a lifespan, and once it reaches that lifespan, it must be scrapped.
So, how long can an injection mold typically be used?
In fact, there is no fixed answer to the lifespan of an injection mold. It is affected by many factors, including the mold material, structural design, machining precision, injection molding process, and maintenance.
Moreover, through scientific selection, collaboration, and maintenance strategies, the lifespan of molds can be doubled or even several times over.
Factors affecting the lifespan of injection molds
1, Mold material and heat treatment
The materials of the core components of a mold (cavity, core, inserts) directly determine its wear resistance, corrosion resistance, and fatigue resistance.
Ordinary consumer products (such as plastic toys and daily necessities) often use P20 pre-hardened steel, with a lifespan of 100,000 to 300,000 cycles, which is suitable for small-batch, low-precision requirements.
Mid-range industrial products (such as appliance housings and automotive interior parts) mostly use 718H pre-hardened steel, which has high hardness and a lifespan of 300,000 to 500,000 cycles, balancing cost-effectiveness and wear resistance.
High-end precision products (such as core automotive components and medical consumables) require S136 stainless steel or H13 hot work die steel.
S136 has strong corrosion resistance and is suitable for injection molding of transparent parts or corrosive materials. H13 has excellent thermal fatigue resistance and is suitable for high-temperature injection molding scenarios. Its service life can generally reach millions of cycles, and after professional heat treatment, its service life can exceed 5 million cycles.
Furthermore, the specialization of the heat treatment process is crucial. If quenching and tempering are insufficient, residual stress will exist inside the mold, leading to cracking and deformation during use, directly shortening its lifespan.
2, Mold structure design
An unreasonable structural design can lead to localized stress concentration, accelerating mold wear or damage.
For example, sharp corners and thin edges are prone to cracking and should be designed with rounded corners; if the clearance between the demolding mechanism (ejector pin, push plate) and the cavity is too large, the product will stick to the mold and forced demolding will scratch the cavity; if the clearance is too small, jamming and wear will occur.
For complex products, using an interlocking structure can avoid scrapping the entire mold and extend the overall life of the mold by replacing worn inserts.
Meanwhile, the design of the cooling system also affects the mold life. Uniform cooling can reduce the thermal stress caused by temperature difference in the mold and prevent cracks from appearing on the surface of the cavity.
3, Injection Molding Process and Raw Materials
The process parameters and material properties during injection molding directly affect the wear rate of the mold.
Regarding temperature, excessively high barrel temperature can cause raw material decomposition, producing corrosive gases that erode the mold cavity; excessively low mold temperature can increase injection pressure, leading to excessive stress on the mold.
In terms of pressure, excessive injection pressure and holding pressure will cause the mold cavity and core to bear excessive load, which will lead to deformation or wear over time.
Regarding raw materials, if the raw materials contain hard fillers such as glass fiber and calcium carbonate, it will aggravate the wear on the cavity surface; if the raw materials are not dried sufficiently and contain moisture, bubbles will be generated during the injection molding process, and the gases from the decomposition of moisture will also corrode the mold.
4, Maintenance and upkeep
Routine maintenance of molds is a key factor affecting their lifespan. Many customers focus only on product quality after using molds, neglecting mold maintenance, which leads to residual raw materials and rust on the mold surface, accelerating wear over time.
How to extend mold life?
1, Initial Selection
As the demand side , during the mold procurement stage, the production batch and quality requirements of the product should be clearly defined, and the mold material and heat treatment standards should be determined together with the mold factory to avoid choosing low-quality materials due to “cheapness”.
Clearly define material requirements. Select appropriate steel based on production volume. If the batch exceeds 1 million cycles, avoid using P20 steel and prioritize S136 or H13. For corrosive materials (such as PVC) or transparent parts, stainless steel must be selected.
Specify heat treatment standards. Clearly define heat treatment process requirements in the mold contract, such as quenching temperature, tempering times, and hardness range, and require the mold manufacturer to provide a heat treatment report. If necessary, a third-party testing agency can be commissioned for verification.
Choose high-quality components. Standard mold components (ejector pins, springs, guide pillars, and guide bushings) should be from well-known brands. Inferior components are prone to breakage and wear, affecting the overall lifespan of the mold.
2, Mid-term cooperation
During the mold design phase, the client should work closely with the mold manufacturer and participate in structural reviews to avoid shortening the mold’s lifespan due to design flaws.
Emphasis is placed on rounded corner transitions and strength design. Mold manufacturers are required to round all sharp corners and thin edges, and to thicken or reinforce areas subjected to high stress.
An interlocking structure is adopted. For complex cavities or easily worn parts, an interlocking structure is required to facilitate the replacement of inserts later and reduce maintenance costs.
Optimize the cooling system. The mold manufacturer is required to design uniform cooling water channels to ensure that the temperature difference between different parts of the mold does not exceed 5°C, thus avoiding cracks caused by thermal stress.
Conduct pre-acceptance testing of the mold. After the mold is manufactured, conduct trial molding and pre-acceptance testing to check whether the mold structure is reasonable, whether there are any stress concentration areas, and promptly propose modifications.
3, Later use
During the mold usage phase, the client should develop standardized injection molding process procedures to avoid mold damage due to improper human operation.
Establish a range of process parameters. Based on the trial molding parameters provided by the mold manufacturer, establish a reasonable range for the injection molding process, clearly defining the upper and lower limits of barrel temperature, mold temperature, injection pressure, and holding pressure, and prohibiting operators from arbitrarily adjusting them.
Properly pre-treat raw materials. For hygroscopic materials (such as PA, PC, and ABS), they must be thoroughly dried to prevent moisture decomposition and the generation of corrosive gases. For raw materials containing hard fillers, lubricants can be added to the raw materials to reduce wear on the mold cavity.
Avoid overloading production. Prohibit ultra-high speed and ultra-high pressure injection molding in order to increase output, as long-term overloading production will lead to mold fatigue damage.
Handle abnormal situations promptly. If abnormalities such as product sticking to the mold or ejector pin jamming occur, stop the machine immediately for inspection. Do not force demolding or operate violently to avoid damaging the mold.
4, Maintenance and upkeep
Mold maintenance is key to extending its lifespan. Customers should establish a full-cycle mold maintenance system, including daily maintenance, periodic maintenance, and storage maintenance.
Routine maintenance. After each production run, clean the residual material from the mold cavity and core surface, and use compressed air to blow clean the water channels and venting grooves; for minor scratches on the mold surface, polish with an oilstone; apply lubricating oil to moving parts such as ejector pins and guide pillars to prevent rust and wear.
Regular maintenance. Depending on the production volume, conduct a comprehensive inspection and maintenance of the mold regularly, generally once every 10,000 to 50,000 production cycles.
The inspection includes checking the wear of ejector pins, springs, guide pins and bushings, the wear and corrosion of the cavity surface, and the unobstructed flow of cooling water. Severely worn parts are replaced, and the cavity surface is polished or nitrided to restore surface hardness and smoothness.
Storage and maintenance. If the mold is not used for a long period of time, it should be stored and maintained. First, clean the residual raw materials and oil stains on the surface of the mold. Then, apply rust-preventive oil to the surface of the cavity and core, apply grease to the moving parts, and finally wrap the mold with plastic wrap or rust-proof paper and store it in a dry and ventilated environment.
Summary
The lifespan of an injection mold is not determined by a single factor, but is a combination of materials, design, process, and maintenance.
For the demand side, early selection and design collaboration lay a solid foundation, standardized use in the middle stage reduces wear and tear, and later maintenance is key to extending lifespan.
By doing the above, the lifespan of the mold can be doubled or even several times over, thereby reducing production costs and improving product quality stability.
