Defects and Solutions in Injection Molding of Automotive Interior Parts

Due to the advantages of lightweight, corrosion resistance, and good machinability, plastic products are widely used as automotive interior parts. Injection moulding is an important process for small-batch plastic automotive interiors. There are many factors affecting the quality of automotive interior parts in low-volume injection molding, including mold design, raw material quality, parameter setting, and injection process.

Improve the Surface Roughness of Automotive Interior Parts

In injection molding of automotive interior parts, poor surface quality is a common problem. This issue is mainly related to the quality of raw materials, unreasonable mold structure design, and equipment problems. To address this, we should select high-quality raw materials to ensure standard melting point, fluidity and other parameters.

On this basis, it’s necessary to optimize the mold structure design. Facing unreasonable mold structure design, we can redesign the mold injection system, cooling system, and so on. This can improve the fluidity and cooling effect in injection molding, and reduce the problems of poor material flow, overflow, and sticking to the mold.

In addition, injection molding parameters also need to be optimized. Increase the injection pressure and adjust the injection speed to improve the quality and efficiency of injection molding.

Poor Dimensional Accuracy and Solutions

In the process of low-volume injection molding, poor dimensional accuracy refers to the low dimensional accuracy of the products and the disparity between parts design and dimensions. This may lead to defective products in the actual application, such as poor fit between parts and reduced working performance. The reasons for the poor dimensional accuracy of the products mainly include low precision of molds, inaccurate gate position, unreasonable selection of injection process, unreasonable design of the cooling system, etc.

Given the above problems, three solution measures can be taken to manufacture automotive interior parts. First, the mold should be accurately measured and debugged before injection production. The size, shape and surface roughness of the mold should meet the design requirements of the automotive interior parts. If necessary, the mold can be repaired or replaced to improve the precision of the mold. This step ensures the reliability and consistency of the mold, thus guaranteeing the interior parts of low-volume injection molding meet the quality standards.

Secondly, automotive interior parts have complex shapes and extremely deep contours, and the plastic casting material has flow characteristics. The gate position can be rationally adjusted to ensure even flow and good filling during the mold-filling process. This helps reduce the internal stress of the part, shorten the cooling time and improve the dimensional accuracy. For example, for complicated automotive interior parts, the gate design can be optimized to balance the flow path and prevent the material from flowing unevenly in the mold.

Thirdly, optimize the injection molding process, including adjusting parameters such as mold filling speed, injection pressure, holding time and holding pressure to reduce the dimensional deviation of the product. In addition, it is necessary to ensure the stable operation of the injection molding machine to prevent dimensional errors due to equipment failure. During the production process, keep the mold temperature stable to avoid overheating or undercooling of the mold.

Meanwhile, a suitable melt temperature can improve the liquidity of the plastic and the effect of mold filling. For example, when manufacturing interior trim parts such as instrument panels or door panels, precise control of temperature and pressure parameters can significantly improve the surface finish and structural integrity of the product.

Reduce the Fusion Marks That affect Parts’ Appearance

Fusion mark refers that when the melt is injected into the cavity during the injection molding, the melt will be extruded under the pressure difference due to the pressure difference between the melt and the cavity. It will lead to a depression or bulge on the surface of the plastic parts.

For automotive interior parts, it is often applied to some plastic materials, such as PP, ABS plastic and so on. These plastic materials have different heat-resistant properties and will melt when they encounter high temperatures during processing. Various materials will fuse under high temperatures. The fusion marks will seriously affect the appearance and quality of automotive interior parts.

To address this problem, plastic materials with better heat resistance should be selected when designing and manufacturing automotive interior parts. In addition, the optimization of the injection molding process can also reduce the fusion marks.

For example, parameters such as injection temperature and pressure can be adjusted to reduce the flow rate of the melt and the pressure difference, so as to reduce the fusion welding. In practical production, you can also spray a layer of anti-adhesive on the surface of the mold to reduce the appearance of fusion welding marks.

Avoid Product Warping and Deformation in Injection Molding

Product warping and deformation refers to the deformation of the molded product after cooling and solidification, and its shape changes. Due to the different structures and materials of injection molded products, they are prone to warping and deformation during the molding process.

The warping and deformation of injection molding products will affect the appearance of automotive interior parts, reduce their aesthetics, and seriously affect the performance of automotive interior parts. Therefore, great attention should be paid to the warping and deformation of injection-molded products.

The following are solutions for the warping and deformation problems of the molded products. Above all, choose suitable molds, such as adopting large risers and small inlet ports, etc. to improve the flow stability of the automotive interiors. Next, choose suitable molding process parameters in injection molding, such as reasonable injection speed, holding pressure and time, etc. This helps to reduce internal stresses, thereby improving the dimensional stability of interior components. For example, precise control of injection and holding pressure parameters can significantly reduce warping in the finished automotive dashboards.

Besides, in the process of molding, reduce the temperature of the melt, pressure holding time and mold temperature. Finally, when the automotive interior parts need twice processing, pre-shape the product to facilitate further processing.

Conclusion

In the injection molding process of small batch automotive interiors, improper mold design, unreasonable process parameters, poor quality of raw materials, and production equipment breakdown may lead to quality problems. Automotive manufacturers must attach great importance to these issues and adjust production based on the characteristics and causes of quality problems. This approach effectively improves the quality of low volume injection molding of automotive interiors.