In the process of Injection Mold Design, shrinkage marks on plastic products are a common problem that needs to be avoided as much as possible. Sinkage marks not only affect the appearance quality of the product, but may also have adverse effects on the performance and dimensional accuracy of the product.
First of all, the reasonable design of the gate position and number is the key. The gate position should be selected in the thick wall of the plastic product or away from the area with high critical size and appearance requirements. This can make the plastic melt more uniform during the filling process and reduce local overheating and insufficient pressure. At the same time, appropriately increasing the number of gates can reduce the flow distance of the plastic melt, increase the filling speed and pressure, and thus reduce the occurrence of shrinkage marks.
Secondly, optimizing the cooling system is crucial. A good cooling system can ensure that the plastic product shrinks evenly during the cooling process and avoid shrinkage marks caused by local overheating. The cooling water channel should be arranged near the thick wall of the plastic product to speed up the cooling speed of these areas. At the same time, ensure that the diameter and spacing of the cooling water channel are reasonable to make the cooling effect uniform and consistent. Advanced technologies such as conformal cooling can also be used to further improve cooling efficiency and uniformity.
Furthermore, the correct selection of injection molding process parameters can also effectively reduce shrinkage marks. Properly increasing the injection pressure and injection speed can make the plastic melt fully fill the cavity, reducing internal voids and areas of insufficient pressure. At the same time, extending the holding time can continuously replenish the melt during the cooling and shrinking process of the plastic, reducing the generation of shrinkage marks. In addition, it is also important to adjust the mold temperature. For crystalline plastics, properly increasing the mold temperature can promote uniform crystallization and reduce shrinkage marks.
In mold design, special structural designs can also be considered to avoid shrinkage marks. For example, setting reinforcing ribs or bosses in areas with thicker wall thickness of plastic products can increase local strength and rigidity and reduce shrinkage. At the same time, hot runner technology can be used to reduce the temperature loss of plastic melt during flow and improve the filling effect.
Finally, choosing the right plastic material is also an important part. Different plastic materials have different shrinkage rates and performance characteristics. Materials with smaller shrinkage rates and better fluidity should be selected according to product requirements. At the same time, it is necessary to ensure the dryness and stable quality of plastic materials to avoid the generation of shrinkage marks due to material problems.
In short, in Injection Mold Design, by reasonably designing the gate position and quantity, optimizing the cooling system, correctly selecting the process parameters, adopting special structural design and selecting suitable materials, it is possible to effectively avoid shrinkage marks on plastic products and improve the quality and performance of products.
