What are the factors that affect precision injection molding of molds?

Among the relevant factors that affect precision injection molding, the mold is the key to obtaining precision plastic products that meet the quality requirements.

The design of the mold, whether the mold design is reasonable or not, will directly affect the quality of plastic products.

Since the mold cavity size is derived from the required size of the plastic product plus the shrinkage rate of the material used, and the shrinkage rate is often a range of values recommended by the plastic manufacturer or engineering plastics manual, it is not only related to the mold gate form, gate location, and distribution but also related to the crystalline orientation of engineering plastics (anisotropy), the shape and size of the plastic product to the distance and location of the gate.

The main factors affecting the shrinkage of plastics include thermal shrinkage, phase change shrinkage, orientation shrinkage, compression shrinkage, and elastic recovery.

These influencing factors are related to the molding conditions or operating conditions of the precision injection molded products.

Therefore, mold designers must have rich experience in design and injection molding and must consider the relationship between these influencing factors and injection conditions and their apparent factors, such as injection pressure and cavity pressure and filling speed, injection melt temperature and mold temperature, mold structure, and gate form and distribution, as well as gate cross-sectional area, product wall thickness, the content of reinforcing filler in plastic materials, the crystallinity and orientation of plastic materials, etc. The influence of the above factors also depends on the plastic material.

The influence of the above factors also varies depending on the plastic material, or other molding conditions such as temperature, humidity, continued crystallization, and changes in the molding machine after molding.

Since the injection molding process is the transformation of plastic from solid (powder or pellet) to liquid (melt) and then to solid (product).

From the granule to the melt, and then from the melt to the product, the middle has to go through the action of temperature field, flow field, and density field.

Under the joint action of these fields, different plastics (thermosetting or thermoplastic, crystalline or non-crystalline, reinforced or non-reinforced, etc.) have different polymer structural forms and rheological properties.

All these factors will affect the physical and mechanical properties, size, shape, precision, and appearance of plastic products.