Conventional injection molding machines consume energy rapidly and result in significant waste when molding thick plastic products. In order to change this situation, high-speed injection molding machines utilize closed-loop servo systems to save energy and reduce production costs for businesses.
The requirements for high-speed injection molding machines to produce thin products are determined by the precision of the molded products, including dimensional tolerances, positional tolerances, and surface roughness.
Tight injection molding requires various conditions, with the fundamental factors being plastic material, mold, injection molding process, and injection molding equipment. When designing plastic products, it is important to first select plastic materials with high mechanical properties, dimensional stability, resistance to creep, and resistance to environmental stress cracking that are suitable for high-speed injection molding machines.
Subsequently, based on the selected plastic materials, product dimensional accuracy, weight, quality requirements, and the predetermined mold structure, an appropriate high-speed injection molding machine should be chosen. During the processing, particular attention should be given to mold precision, injection mold shrinkage, and variations in environmental temperature and humidity.
In high-speed injection molding machines, molds are crucial for producing tightly molded plastic products that meet quality requirements. The molds used for tight injection molding must meet the requirements for product dimensions, precision, and appearance.
However, even if the molds have consistent precision and dimensions, the actual dimensions of the molded plastic products may differ due to differences in shrinkage. Therefore, effectively controlling the shrinkage rate of plastic products is of great importance in injection molding technology.
Different plastic materials exhibit variations in properties and other molding conditions such as temperature, humidity, continued crystallization, post-molding internal stress, and the performance of the injection molding machine.
The injection molding process involves the transformation of plastic from a solid state (powder or pellets) to a molten state and back to a solid state (finished product). During the transition from pellets to molten state and from molten state to finished product, temperature fields, stress fields, flow fields, and density fields come into play. Under the combined effects of these fields, different types of plastics (thermosetting or thermoplastic, crystalline or amorphous, reinforced or unreinforced, etc.) exhibit different polymer structure forms and rheological properties.
Factors that affect the aforementioned fields will inevitably impact the physical and mechanical properties, dimensions, appearance, precision, and quality of plastic products.
Thus, there is an inherent connection between process factors, polymer properties and structure forms, and plastic products, which is manifested in the characteristics of plastic products. Analyzing these intrinsic connections is crucial for arranging injection molding machines and other processing equipment properly.
High-speed injection molding machines differ from conventional injection molding machines in terms of injection pressure and injection rate; high-speed injection molding typically involves high-pressure or high-speed injection to achieve a smaller molding shrinkage.
Considering all the aforementioned reasons, when designing precision injection molds, it is necessary to consider not only the general design elements of molds but also the following points:
Adopting appropriate mold dimensional tolerances
Preventing errors in molding shrinkage
Preventing injection molding deformation
Preventing demolding deformation
Minimizing manufacturing errors in molds
Preventing errors in mold precision
Maintaining mold precision.
