How to control the residual stress of injection molded parts during auto parts mould plastic injection?
Publish Time: 2025-04-14
In the process of auto parts mould plastic injection, controlling the residual stress of injection molded parts is a crucial link. Residual stress not only affects the dimensional stability, mechanical properties and appearance quality of injection molded parts, but also may cause warping, cracking and other problems in the process of using parts, which seriously affects the safety and reliability of automobiles. Therefore, taking effective measures to control the residual stress of injection molded parts is of great significance for improving the quality and performance of automobile parts.
The residual stress of injection molded parts mainly comes from the uneven cooling and shrinkage of the plastic melt during the process of filling the mold cavity. When the plastic melt is injected into the mold cavity under high pressure, due to the different cooling rates of various parts of the mold, the plastic melt will shrink unevenly during the cooling process, thereby forming residual stress inside the injection molded part. In addition, process parameters such as injection pressure, holding time, cooling time, etc. during the injection molding process will also affect the residual stress.
In order to control the residual stress of injection molded parts, it is necessary to start with mold design first. The cooling water channel of the mold should be designed reasonably and evenly to ensure that the plastic melt can shrink evenly during the cooling process. At the same time, the design of the mold parting surface should also take into account the flow characteristics of the plastic melt to avoid excessive stress concentration at the parting surface. In addition, the location and number of the mold gates should also be reasonably designed according to the shape and size of the injection molded part to reduce defects such as weld marks and flow marks, thereby reducing residual stress.
In terms of injection molding process, reasonable control of parameters such as injection pressure, holding time and cooling time is the key to reducing residual stress. Excessive injection pressure will cause excessive shear stress in the plastic melt during the filling process, thereby increasing residual stress. Therefore, the appropriate injection pressure should be selected according to the shape and size of the injection molded part. The length of the holding time will also affect the magnitude of the residual stress. Excessive holding time will cause the plastic melt to produce excessive pressure in the mold cavity, thereby increasing residual stress. Insufficient cooling time will cause uneven shrinkage of the plastic melt during the cooling process, which will also increase residual stress. Therefore, the holding time and cooling time should be reasonably adjusted according to the actual situation.
In addition to mold design and injection molding process, material selection is also an important factor in controlling the residual stress of injection molded parts. Different types of plastic materials have different shrinkage rates and mechanical properties, so the appropriate material should be selected according to the use requirements of the injection molded parts. At the same time, by adding an appropriate amount of reinforcing fiber or filler to the plastic, the mechanical properties of the plastic can also be improved and the residual stress can be reduced.
In actual production, the residual stress of the injection molded parts can be further reduced through post-processing processes. For example, annealing can rearrange the plastic molecular chains, thereby releasing the internal residual stress. In addition, vibration aging treatment can also effectively reduce the residual stress of the injection molded parts and improve their dimensional stability and mechanical properties.
In summary, controlling the residual stress in the process of auto parts mould plastic injection requires starting from mold design, injection molding process, material selection and post-processing process. By comprehensively considering these factors and taking corresponding measures, the residual stress of the injection molded parts can be effectively reduced, and their quality and performance can be improved, thereby meeting the high requirements of the automotive industry for parts.
