Injection molding machine screw drive

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. 

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. 

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. 

An injection-molding screw is rotated using an electric drive motor coupled with a reducer or gear box or a direct hydraulic drive. Electric drive motors are usually employed with larger hydraulic machines [clamp force > 15,000 kN (1700 tons)]i and in all-electric molding... 

An amorphous polyester-montmorillonite nanocomposite prepared from condensation of 2,2,4,4-tetramethyl-l,3-cyclobutanediol, 1,3-propanediol, and dimethylterephthalate produced unexpected mechanical properties [45]. Cloisite 20A was melt blended with the polymer at 2.5,5, and 10 wt.% with a Haake HBI System 90 drive attached to a Rheomex CTW 100 twin-screw extruder. The r/min of the extruder was 60 and the temperature was 120°C. The test samples were prepared in two different injection molders. The test samples from the polyester-montmorillonite composite at 5% Cloisite 20A content were prepared with a Demag Ergotech 35 at 150°C with a pressure range of 10000 to 11000 psi. The test samples from the polyester-montmorillonite composites with 2.5, 5.0, and 10% Cloisite 20A content were prepared with a mini-jector molding machine at a temperature range of 190-200°C. 

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