Research Of Injection Unit And Ejection Unit Control Technology Of All-electrical Injection Molding Machine

All-electrical injection molding machine has advantages of energy-saving, highaccuracy, high speed and cleanliness. The control systems abroad of all-electrical injectionmolding machine have had advanced functions, such as current monitoring, on-line visualinspection, mold protection, synchronous temperature rise, quality informationmanage-ment and process optimization, etc. Limited by control system and servotechnology, domestic manufacturers rarely involves in all-electrical injection moldingmachine. Following the deep analysis of process requirements, the software and hardwareframework and the control technology of injection unit and ejection unit are completedbased on the platform of HNC8numerical control system.The similarity and distinguish between all-electrical injection molding machinecontrol system and machine tool NC system are analyzed according to the basic process ofinjection molding. State machine is applied to manage the processing action of each motorfor the differences where the former uses processing parameters and the later G-code todrive the machine. The state-machine is applied to manage the process action of eachmotor, using which the control arithmetic of injection and ejection unit is designed andrealized following building up of the model, state division and tidying of state transfercondition. Ladder program is used to monitor the operation panel and switch signal of themachine, to support the interlocking logical judgment and to send control commandsautomatically.Press packing model of injection unit is built up, and a method is supplied to achievethe following control of setting packing pressure, which combines PI controller andpressure acceleration planning, with a result of getting a rapid response to pressurepacking and resolving the problem of pressure overshoot. A method of direct backingpressure control based on conic is raised after the analysis of metering process and itsinfluencing factors, which resolves the problem that how to control the injection motor’srotation speed to following the setting back pressure and that can be resolved through theadjust of spring force of back pressure valve in the traditional hydraulic injection moldingmachine. Motion model of ejection motor is built up after the analysis of several ejectionmotion mode. Process control arithmetic of ejection motor using the thinking ofhierarchical structure and building block design is achieved. The function of pre-ejection,ejector lever protection and intelligent parameter optimization are also developed.A prototype machine is developed and principle experiments are completed on theplatform of a Chen Hsong injection molding machine. The back pressure can be controlledless than0.8MPa and the repeat accuracy can reach0.24%. The control system hasadvantages of manipulation, control precision, repetition accuracy and plasticizing effect,which satisfy the designing requirements.