Study On Precision Injection Unit

New injection molding technologies including precision injection molding technology are developing with the requirements of high quality of injection molding parts. Precision injection unit is the key factor affecting internal quality of parts and power consumption for precision injection molding. There is major gap between china and developed countries in precision injection molding, this subject aims to find the causes of gap ,improve precision of injection molding machines at low cost and develop a new precision injection unit by performance experiments of machines and improving measurements.Contrast experiments of repeat precision were carried out with four different types of injection molding machines in shot-to-air, non-fullness and fullness at different process conditions and with different materials. It was to research the affect of machine structure, process conditions and control system on the precision of parts, and find out the differences with existing precision injection molding machine for putting forward some improving measurements and developing a new type of injection unit. The main conclusions are as follows: 1,HTH200x2's repeat precision is the highest by 1.14‰; HTD86-e210 is second by 1.16‰; HTF86x5's repeat precision is the lowest.2,HTD86-e210's precision is higher than other machines in temperature and metering control; Among all hydraulic machines, ALLROUNDER 270S' hydraulic temperature control is the highest in precision, and there are some problems with hydraulic cooling system of HTH200x2 and HTF86x5.3,There are some problems with hydraulic circuits of HTF86x5.4,Magnetostrictive displacement transducer's precision is higher than linear position transducer, but the parts' repeat weight precision is lower due to assembly, environment, resolution of controller, compatibility between magnetostrictive displacement transducer and controller.5,There are not linear relationship between repeat precision and process parameters as backpressure, injection speed, injection pressure and rotation speed, but there is a range of the highest repeat precision.6,Global performance of the new non-return valve is more excellent than old non-return valve, and the repeat precision is improved by 2.3 times; It resolved flow resistant of new non-return valve by improving design to improve repeat precision at low cost.