Automobile parts

New energy vehicles are increasingly playing a more significant role in our lives. For the battery pack components of new energy vehicles, the mold design and the matching of injection molding machines are indeed more challenging than for traditional components. To meet the development trend of "lightweighting, large-scale, and integration" of battery packs, the mold technology needs to undergo the following key upgrades:

• Material Adaptability Innovation

To reduce weight and increase energy density, components such as the upper cover of the battery pack have begun to extensively use resin-based fiber-reinforced composite materials (such as glass fiber and carbon fiber reinforced plastics), instead of traditional metals. This means that the molds need to be made more durable, as the fiber materials have poor fluidity and cause significant wear on the molds. The mold steel must have extremely high wear resistance. Secondly, the molding of composite materials is extremely sensitive to mold temperature. The mold needs to be designed with more complex and efficient heating/cooling systems to ensure that the materials flow and cure fully.

• Large-scale and Integrated Structure

The battery pack shell is often very large in size (such as the upper cover), which requires the molds to develop towards large-scale. High rigidity design: The large-sized molds themselves require stronger supporting structures and guiding components to prevent deformation during high-pressure injection, which affects product accuracy. The molds have excellent exhaust systems: For large thin-walled parts, when filling at high speed, if the air in the cavity cannot be quickly expelled, it is very likely to cause trapped air, burning, and other defects. Therefore, higher requirements are placed on the design of the exhaust slots of the molds.

• Precision and Standardization

The battery pack is related to safety and requires extremely high dimensional accuracy. The country released a special standard GB/T 45677-2025 in 2025, which puts mandatory requirements on the structure, parts, assembly, and performance of such molds. This means that mold design and manufacturing must be more standardized and normalized.

Matching of mold design with the tonnage of injection molding machines

The core indicator of the tonnage of an injection molding machine is the clamping force, which directly determines whether the mold can be "locked" to prevent the production of flash (spurs). The matching method mainly consists of two steps:

The first step is to estimate the clamping force through the projected area and the cavity pressure. The most scientific estimation formula is: Required clamping force (tons) = [Product projected area (cm²) × Cavity pressure (tons/cm²)] × Safety factor. However, this is only an estimated value. When selecting the model, it is recommended to choose an injection molding machine with 80% of the calculated tonnage, leaving sufficient margin. 

Correcting the tonnage is just the beginning. It is also necessary to ensure that the molds can be smoothly installed and operate properly.

o Installation size verification: The width of the mold must be less than the inner spacing of the ram (column) of the injection molding machine. 

        Usually, a safety margin of at least 50mm is required. Otherwise, the mold cannot be installed.

o Thickness and stroke verification: The overall thickness of the mold must be within the maximum/minimum mold thickness range allowed by 

        the injection molding machine. At the same time, the ejection stroke of the injection molding machine must be able to easily remove the finished 

        product.

o Special performance matching (for battery packs):

       （1）High-load injection capability: Due to the high viscosity and poor fluidity of the composite material, it requires a long period of high-pressure 

                   holding to fill fully. The selected machine model must have a large torque motor and a highly rigid injection table to ensure that it can 

                   complete long periods of high-pressure injection and holding. 

        （2）Locking force efficiency: Advanced locking technology can achieve effective locking with smaller machines. Technical data shows that the                     451-ton injection machine with the new locking mechanism has locking performance comparable to the traditional 850-ton machine. This                     means that when selecting a model, one should not only look at the tonnage figure, but also pay attention to the actual locking 

                   rigidity and accuracy of the equipment.