In aluminum high pressure die casting production, mold lifespan issues often don’t become apparent immediately, but once they do, the losses are continuous and amplified. Premature cracking, severe erosion, and frequent repairs not only directly increase the cost per unit but can also lead to downtime, delivery delays, and even the scrapping of entire batches of products. Many companies neglect mold lifespan planning in the initial stages of a project, ultimately paying a high price during mass production. How to reduce the risk of mold failure at the source and extend the service life of aluminum high-pressure die casting molds is a problem that every die casting company must address. Raidy Mold manufacturers will systematically analyze the core factors affecting die casting mold lifespan from four key aspects: mold design, mold manufacturing, mold materials, and mold service and maintenance.
Die Casting Mold Design
Every detail in the die casting mold design stage directly affects the lifespan of aluminum high-pressure die casting molds. Improper design can lead to early cracking, localized damage, or insufficient overall rigidity, resulting in frequent repairs and downtime. Many companies neglect these factors in the initial stages, ultimately incurring high maintenance costs. To avoid these problems, Raidy Mold manufacturers optimize mold design from the following key aspects to maximize mold lifespan and production stability.
Typically, the following points are recommended during this stage:
①. Choose an appropriate radius (R-angle).
R-angle cracking frequently occurs in the early failure of die casting molds. Experiments have shown that when the R-angle is less than 1mm, the material’s resistance to cracking decreases. Mechanical stress and thermal stress are usually present in die casting molds, and thermal stress is related to temperature changes and the mold’s operating temperature. Therefore, considering the mold’s operating temperature, it is recommended that the R-angle for aluminum die casting be >1.0mm.
②. Mold Strength and Rigidity
The strength and rigidity of the mold must be absolutely guaranteed to prevent deformation during use and reduce the lifespan of the aluminum high pressure die casting mold. Therefore, the mold wall should have sufficient thickness. It is usually recommended to calculate this using two methods:
a. Considering the compressive load on the mold material – the clamping force.
b. Considering the deformation amount δ of the mold material due to the casting pressure.
③. Use of Inserts
For easily damaged or less strong parts, inserts should be used. For long-life molds, it is recommended to use guide bushings for the ejector pin holes.
④. The gate should avoid directly impacting the core.
⑤. Distance between Cavity Surface and Cooling Channels
Sufficient distance should be maintained between the cavity surface and the cooling channels. A shorter distance will increase thermal stress due to drastic temperature changes, while an excessively large distance will reduce the cooling effect. The distance between the horizontal cooling water hole wall and the cavity is generally recommended to be 25mm, and 28mm at the gate; the distance between the vertical cooling water hole wall and the cavity is generally recommended to be 15mm. If water cooling is used, the hole diameter is recommended to be 9-12mm;
If oil cooling is used, the hole diameter is recommended to be 12-15mm; generally, more and finer cooling channels provide better cooling than fewer and larger cooling channels.
To ensure that the mold achieves the expected lifespan in actual production, every design detail affects the actual application. If you want your aluminum high-pressure die-casting mold to be stable in mass production and avoid unnecessary losses due to design problems, please contact us. Our engineering team will combine your product and production conditions to provide a customized mold design solution, making your die-casting molds last longer and production more efficient.
Aluminum High Pressure Mold Manufacturing
In aluminum high-pressure die casting, the quality of mold manufacturing is one of the factors that directly affect lifespan and yield. Processing residual stress, white layer, rough grinding marks, or improper lubrication often lead to early cracking, mold sticking, and rework, increasing costs and delaying delivery. Strict process control is key to ensuring the long-term stable use of the mold. During the die-casting mold manufacturing stage, the following points are recommended:
①. Adopt the recommended mold processing process:
a. CNC rough machining (leaving a machining allowance of 0.5-1.8mm, depending on the size and complexity of the mold);
b. Mold stress relief (optional for simple molds);
c. CNC semi-finishing (leaving a machining allowance of 0.5-1.8mm, depending on the size and complexity of the mold);
d. Mold vacuum heat treatment (one quenching, three tempering);
e. CNC precision machining/EDM machining;
f. Stress relief tempering/oxidation/surface treatment;
②. Avoid residual EDM white layer on the cavity surface. After EDM machining, the material surface forms a melting and re-solidification layer, a re-quenching layer, a re-tempering layer, and a base material from the outside to the inside (see the right figure). The melting and re-solidification layer is not easily corroded by corrosive agents and appears white when observed with a metallographic microscope, usually referred to as the white layer. The white layer and the re-quenching layer increase the surface hardness of the material, while the re-tempering layer reduces the surface hardness. This structure is similar to an eggshell and the egg white underneath, and is particularly prone to cracking under external force, becoming a source of early cracking microcracks.
It is usually recommended that EDM machining be performed in multiple steps, with low current and high frequency parameters used in the final stage to reduce the thickness of the white layer. After completion, re-temper at a temperature 25℃ lower than the original tempering temperature to achieve stress relief. Finally, grind or polish the machined surface with sandpaper or oilstone (a dedicated EDM oilstone is recommended) to completely remove the surface EDM affected layer.
③Avoid rough grinding marks at corners. Rough grinding marks are usually left by the power tools used in mold processing, leaving significant residual stress, which can easily become a source of early cracking, and early cracking is more likely to occur at corners.
④Avoid excessive surface polishing. A particularly bright surface is not conducive to the adhesion of mold release agents. It is usually recommended to polish the die-casting mold surface to 320# sandpaper.
⑤For molds prone to sticking, shallow nitriding or oxidation treatment is recommended. Die sticking refers to the chemical reaction that occurs between the molten metal and the mold cavity surface, leading to adhesion between the casting and the mold. Die sticking is usually related to the temperature and composition of the molten aluminum and the cooling of the mold. Surface shallow nitriding or oxidation (preferably shallow nitriding + oxidation) treatment can separate the direct contact between the die-casting metal and the mold material, reducing the occurrence of die sticking failure.
⑥Pay attention to the clearance and lubrication of sliding components
The position and number of ejector pins directly affect the smooth ejection of the casting from the mold cavity. To prevent die sticking, severe die sticking requires flame baking to clean the casting from the cavity, and manual removal of residue may also be necessary. These methods can damage the strength of the mold material and the protective layer on the mold cavity surface, thereby reducing the mold life. Generally, sliding components such as ejector pins and sliders must be properly lubricated, with appropriate clearances. Generally: ejector pin clearance 0.05mm; slider clearance 0.1-0.2mm.
Furthermore, the quality of sliding components such as cores, sliders, and ejector pins should also be given attention. These components directly affect the continuity of mold production and play an important role in increasing the casting output per unit time.
Raidy mold manufactures and delivers up to 200 sets of high-precision molds annually, suitable for die-casting machines of different tonnages ranging from 850 tons to 4400 tons. Our production workshop is equipped with five-axis and three-axis machining centers, as well as high-precision equipment such as DMG, MAKINO, and CMM coordinate measuring machines, enabling us to undertake various complex projects, including engine cylinder blocks and medical accessory molds with an accuracy of up to 0.01mm. With our experienced production team and strict quality control system, we ensure on-time delivery of qualified molds, providing you with a stronger competitive advantage in the aluminum die-casting field.
Main Materials for High Pressure Die Casting Molds
Strict control of the process during mold manufacturing is only part of extending mold life, while material selection directly determines whether the mold can operate continuously and stably in a high-temperature, high-pressure molten aluminum environment. If the mold material lacks sufficient hot hardness, has poor thermal conductivity, or insufficient wear resistance, even with high processing accuracy, the mold may still crack, deform, or wear prematurely, thus shortening its service life.
Selection of materials for parts in contact with the molten alloy:
① High hot hardness, high high-temperature strength, tempering resistance, and impact toughness at high temperatures;
② Good thermal conductivity and fatigue resistance;
③ Good hardenability and minimal heat treatment deformation;
④ High wear resistance, corrosion resistance, and high-temperature oxidation resistance;
⑤ Good machinability;
⑥ High material purity and excellent metallographic structure.
Die Casting Mold Use and Maintenance
Even a high quality die casting mold can easily fail prematurely if used improperly. During the mold’s service life, various measures should be taken to reduce thermal and mechanical stresses on the mold surface to prevent premature failure; the following measures are recommended:
①. While ensuring the quality of die casting, minimize the temperature of the molten metal. Data shows that increasing the aluminum melt temperature by 20°C will shorten the life of aluminum die-casting molds by 20%.
②. Preheat the mold to a sufficiently high temperature using the correct method:
For example:
a. Heating with a gas flame or electric heater;
b. Reducing the piston speed in the initial stage, using a lower injection speed for the first 5-10 cycles.
c. Mold preheating temperature and working temperature
Mold preheating temperature: 130–180℃
Mold working temperature: 180–250℃
Alloy temperature during die casting: 620–710℃
③. Cool the mold using the correct method:
a. Cool with water, preheating the water to 50°C;
b. Do not reduce the mold temperature by spraying release agent for extended periods;
c. Reduce the amount of release agent sprayed during die-casting downtime to prevent the mold temperature from dropping too low;
d. Do not turn on the cooling water when the mold is hot during die-casting downtime.
④. Avoid using excessively high injection speeds to prevent the mold from experiencing significant mechanical stress and increased erosion risk.
⑤. Maintenance and Repair of Aluminum Die Casting Molds
a. Stress Relief Treatment: During mold use, ensure stress relief treatment is performed after a certain period of use. When fine cracks appear on the mold surface, immediately perform stress relief treatment to prevent the accumulated stress on the mold surface from being released through cracking. In actual product production, it is generally recommended to perform stress relief treatment according to the following schedule: 1,000–2,000 cycles (trial molding stage) → 5,000–10,000 cycles → every 10,000–20,000 cycles thereafter.
b. Using ABP treatment can not only provide stress relief but also strengthen the mold surface, effectively delaying the appearance and expansion of surface cracks (the ABP treatment schedule can refer to the stress relief treatment schedule);
c. After welding and hardening the mold, stress relief tempering should be performed (especially for large or large-area welds).
Extending the service life of aluminum high-pressure die casting molds requires comprehensive consideration from design optimization, precision manufacturing, material selection to daily maintenance. Negligence in any aspect may lead to mold cracking, sticking, deformation, or wear, thus increasing downtime and maintenance costs, and affecting production efficiency and product quality.
Raidy Mold manufacturer has rich industry experience, advanced production equipment, and a strict quality control system, enabling us to provide customers with complete solutions from mold design, manufacturing to material selection and maintenance.Through scientific methods and customized services, we help you maximize the lifespan of your high pressure die casting molds, reduce production risks, and achieve long-term stable aluminum die casting production. If you want to improve mold durability and ensure mass production stability, please contact us. We will provide you with professional and efficient mold life optimization solutions.
