What are the main reasons for deformation of injection molding processed products?

Injection molding processing is a widely used manufacturing process in the plastics industry, through which plastic products of various shapes and sizes can be manufactured. However, injection molding processing also encounters some problems, one of the most common of which is product deformation. This deformation usually occurs when there are problems in a number of areas such as product design, mold design, material selection, injection molding machine settings, and process conditions.

Design is a key factor in determining the success or failure of a product. If the design is not reasonable, the product is likely to shrink unevenly after molding, resulting in internal stresses in the product, which in turn causes deformation. For example, a design with an uneven wall thickness will cause the product to shrink inconsistently during the cooling process, leading to deformation. In addition, sharp corners and slits in the product design and other details will also increase the local shear stress, resulting in deformation of the product in these parts.

Mold design is equally important. The precision of the mold directly determines the precision of the product. If the cooling system of the mold is not reasonably designed, it will lead to uneven temperature distribution in the mold cavity, so that the cooling rate of each part of the product is different, which will lead to uneven contraction and cause deformation. In addition, the choice of material for the mold is also important. If the thermal conductivity of the mold material is poor, it will reduce the cooling rate of the product inside the mold and increase the risk of product deformation.

Next, talk about material selection. Different plastic materials have different melting points, viscosities and coefficients of thermal expansion. If the material chosen is not suitable for the design requirements of the product, it may cause deformation of the product. For example, high viscosity materials generate high shear stresses when filling the mold cavity, which may cause the product to deform upon cooling. In addition, the humidity of the material can also affect its shrinkage behavior. If the material contains too much water, it will evaporate during the heating process, leading to air bubbles or holes inside the product, which can further trigger deformation.

The settings of the injection molding machine are also an important factor in product quality. For example, an injection speed that is too fast may prevent gas from being discharged from the mold cavity, forming air pockets, which in turn triggers deformation of the product. At the same time, insufficient holding pressure and time may result in the product failing to fill the mold cavity completely or shrinking during the cooling phase, triggering deformation.

The control of process conditions such as temperature, pressure and time also has a significant impact on product deformation. If the melt temperature is too high, the viscosity of the material will be reduced, causing the product to shrink during the cooling process and triggering deformation. Similarly, if the holding time is too short, the product may shrink during cooling, triggering deformation.