In the process of injection molding, injection adjustment is the key link to determine product quality and production efficiency. Accurate control of injection parameters can not only improve the dimensional accuracy and appearance quality of products, but also reduce material waste and improve equipment utilization. Therefore, it is very important to master the precise adjustment method of injection molding machine for the optimization of injection molding process.
First, the basic principle of glue injection
Injection molding is one of the core steps in injection molding, which refers to the process of injecting molten plastic into the mold cavity under high pressure. This process is driven by screw or plunger, and its adjustment mainly includes three main parameters: injection speed, injection pressure and injection position. These three parameters affect each other and need to be adjusted comprehensively according to product structure, material properties and die design.
Second, the key factors affecting the injection accuracy
1. Characteristics of raw materials
Different kinds of plastics (such as ABS, PP, PC, etc.) have different melt viscosities and fluidity. High viscosity materials need higher injection pressure and appropriate injection speed to ensure the integrity of mold filling.
2. Mold structure design
The gate position, runner size and cooling system of the mold will affect the flow state of melt in the cavity. Complex mold structure may need multi-stage injection control to meet the filling needs of different regions.
3. Structure and thickness of products
Thin-walled products require high injection speed to avoid premature cooling of melt, while thick-walled products pay more attention to the control of pressure holding and cooling time.
Third, the accurate adjustment method of injection parameters
1. Segmented glue injection control
Modern injection molding machines generally support multi-stage injection function, that is, according to different areas of the product, the injection process is divided into multiple stages, and the injection speed and pressure are adjusted respectively. For example, in the initial stage, high speed and low pressure can be used to quickly fill the cavity, and in the later stage, low speed and high pressure can be switched to ensure the compactness of the product.
2. Set a reasonable injection pressure
The setting of injection pressure should be based on ensuring that the melt is fully filled in the mold. Too high pressure may lead to flash and excessive internal stress. If it is too low, it will easily cause defects such as lack of glue and shrinkage. It is suggested to make a preliminary setting according to the recommended value of materials and fine-tune it according to the test results.
3. Optimize the glue injection speed
The injection speed affects the melt flow state and the surface quality of products. Too fast can easily lead to jet flow and air streaks; Too slow may cause obvious cold material and welding line. It should be set reasonably according to the product thickness, mold temperature and other factors.
4. Monitoring and feedback adjustment
It is helpful to realize process stability and consistency by using the process monitoring system of injection molding machine to record the injection curve in real time and make closed-loop adjustment combined with product quality.
Fourth, the adjustment skills in practical application
-In the mold trial stage, the “slow-fast-slow” injection speed curve should be adopted to gradually find the best parameter combination.
-For complex or precise products, time-position switching (V-P switching) technology can be adopted to improve molding accuracy.
-Regularly calibrate the pressure sensor and position encoder of injection molding machine to ensure the adjustment accuracy.
V. Conclusion
The precise adjustment of injection molding machine is a systematic project, which involves the collaborative optimization of materials, molds, equipment and process parameters. Only on the basis of in-depth understanding of the process principle and continuous adjustment and optimization combined with actual production experience can we truly realize high-quality and high-efficiency injection molding production. For injection molding technicians, mastering scientific adjustment methods is an important way to improve the technical level and product quality.