Injection molding machine-drive

See design, motion-control, mechanical and electronic effects drive-system control electric motor electric-motor drive extruder drive-energy consumption injection molding machine-drive system. 

The plasticator on an injection-molding machine is a specialized plasticating single-screw extruder. The plasticator has two main differences there is a nonreturn valve on the tip of the screw, and the screw retracts as molten material accumulates between the nonreturn valve and the end of the barrel. Pressure is maintained on the accumulated material by a constant force applied to the shank of the screw via the drive system. This force is typically measured as a pressure applied to the shank and is referred to as the back pressure. During the injection step of the process, the screw is forced forward, the nonreturn valve closes, and the material is injected into the mold. Additional information on the injection-molding process can be obtained elsewhere [Ij. 

In order to select the most economical drive for an Injection molding machine, the duty cycle must be calculated (3). This calculation must be made for each specific application to determine the applicable motor rating. A typical duty cycle Is shown In Figure 3. The motor rating Is defined In terms of 1) Nameplate horsepower and service factor (SF) and 2) Breakdown torque In terms of full load. One first calculates the RMS HP via Equation (1). ... 

Electric Drive. This may replace the hydraulic drive in some injection molding machines. There has been very active discussion of this procedure in recent years. 

IMM with an oil hydrauUc system provides the power to turn the screw to plasticate the plastic, inject the melt into the mold cavity, close the mold clamp, hold clamp tonnage, release the clamp, and eject the molded part. A number of hydraulic components are required to provide this power, including motors, pumps, directional valves, fittings, tubings, and oil reservoirs/tanks. See drive-system control hydraulic fluid influenced by heat, injection molding machine hydromechanical clamp See clamping, hydromechanical. 

Hydraulie drive elements like these are also the driving forces on injection molding machines. Figure 6-2 shows how the movement of a hydrauhc ram moves the toggle lever elamping unit of an injection molding machine. 

In recent years, electric drives (hybrid drives) have increasingly been employed for individual movements in injection molding machines. 

Oil hydraulics has become firmly established as the drive system for the vast majority of injection molding machines and until recently was almost unchallenged as the power source. Put at its simplest, the injection molding machine contains a reservoir of hydraulic oil which is pumped by an electrically-driven pump at high pressure, typically at up to 14 MPa, to actuating cylinders and motors. High and low pressure linear movements are performed by hydraulic cylinders, and rotary movements for screw drive and other purposes are achieved by hydraulic motors. Hybrid machines, in which the screw is driven by electric motor while the linear movements remain hydraulically powered, are not uneommon. 

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