Performance Evaluation And Optimization Of Injection Molding Screw

Injection molding is one of the most important methods for plastic molding. As key parts of injection device, the structure and operating characteristics of injection screw have important impact on plasticizing process of materials. It will affect the production efficiency of machine and product quality. Comprehensive performance evaluation of injection molding screw will provide beneficial guidance for injection screw design. It is the premise for further optimization of injection molding screw. This subject connected several aspects of performance evaluation standard of injection molding screw basing on the experiment and established evaluation method of some practical value by combining with relevant theoretical knowledge. The main working contents as following:(1)Experiment on different structure of screws. Repeating weight precision of PP and PS processing by different screws at different process conditions has been measured according to existing repeating weight precision measurement standard. Repeating weight precision grade which characterize weight repeatability of screw machining has been established according to experimental results. (2)Measurement methods for viscosity and temperature homogeneity has been designed and used. Melt pressure fluctuation at the nozzle which characterize viscosity homogeneity and axial average temperature difference and radial average temperature difference which characterize temperature homogeneity have been measured when PP and PS processing by different screws at different process conditions. Melt viscosity and temperature homogeneity grade which characterize plasticizing quality by screw has been established according to experimental results.(3)On-line acquisition system for injection molding machine has been developed. Response time of non-return valve has been measured when PP and PS processing by different screw heads and screws at different process conditions. Evaluation grade which characterize metering accuracy and plasticizing quality of screw has been established.(4)Install pressure sensor along the direction of barrel. Linear pressure distribution at metering section during plasticizing process has been measured when PP and PS processing by different screws at different process conditions. Pressure building ability grade which characterize melt transmission capacity of screw has been established after calculating the pressure gradient.(5)Study on three different structure parameters of metering section and two separation-type screws. Analyze the relationship between screw structure and final plasticizing quality. Optimize the structure of screw.