工程基础注塑机.doc

工程基础注塑机 ENGINEERING BASICS for INJECTION MOULDING MACHINE. 工程基础注塑机。ENERGY Energy is capacity to do work. Work is done when a force moves its point of application in the direction of force. = force x distance moved. Power is rate of doing work. Power = force x (distance/time). This also called energy. Energy can neither be created nor destroyed but only transformed from one form to others. MACHINE A machine is a device that makes the work easier. This can happen by application smaller force (lever principle) to get bigger force to do the work or Changing line of action of force. Machine can not create energy by it self. Therefore, machine requires a prime mover. In most of the machines prime mover is an Electrical motor - 3 phase squirrel cage Induction motor in case of Injection Moulding Machine. In this machine electrical energy is converted to mechanical energy through hydraulics. PRIM-MOVER Electric motor is coupled to hydraulic pump. Pump has flow rating -say 100 liters per min. or 25 gpm. Pump delivers oil flow in the system. Oil flow meets resistance causing resultant pressure in the system. The hydraulic system includes Relief Valves for pressure limit, Flow control Valves for speed and Directional valves for directing oil to Actuators - Cylinder for linear movement and Hydromotor for rotary movement. For each to and fro movement there must be one cylinder as actuator. Therefore there are cylinders for mould open/ close, injection unit forward / retract, Injection / retract. And Hydro-motor for screw rotation, PUMP Pump delivers oil flow in the system at rated flow rate till the resistance reaches say 150 bar. Thereafter further increase in load pressure decreases the flow rate. Many in the moulding shop floor wrongly believe that pump creates pressure. Pump creates flow rate not pressure. Therefore, hydraulic system pressure is not allowed to go beyond 150 bar by Main Relief Valve in the system. ? ? PRESSURE The melt is pushed by the screw tip through noz