INJECTION MOLDING: Efficient Motors, Drives for Injection Presses at NPE

News in hydraulics, servos, and servo-hydraulics.

Several new products for powering injection molding machines were introduced at NPE2015 by Bosch Rexroth Corp., Bethlehem, Pa.

• COMPACT HYDRAULIC MOTOR: A new hydraulic motor from Rexroth’s Hagglunds Drives division (Columbus, Ohio) is a smaller size in the series, aimed at driving injection screw rotation on presses of 200 to 1000 tons. Before now, the smallest unit offered was for presses of 1000 tons and larger. This radial-piston motor is one-fourth the size of previous units (right photo).

• HYDRAULIC PUMP CONTROL: New DFEn rpm control for variable-speed hydraulic pumps saves energy by looking at the flow demand and sending a control signal to the pump motor. Thus, the pump actually controls the motor speed, rather than vice versa. This system can be retrofitted to presses with conventional fixed-speed pumps and motors. According to Bosch Rexroth, it involves changing a pilot valve and adding a variable-frequency drive (VFD) to the pump motor.

• DIRECT SERVO DRIVE: The newest addition to the company’s Sytronix SVP servomotor drives for hydraulic pumps is the model MS2N, which is directly coupled to the pump—which Bosch Rexroth says is unusual for servomotors. The servo pump can control pressure and speed profiles without need for separate valves.

• DRIVE SYSTEM SIMULATION: Also new is the ability to simulate the entire system of hydraulics, mechanical systems, electronics, and software for  an injection machine. This allows Bosch Rexroth to validate the drive control system and energy efficiency of the system before it is built.

• CONFIGURABLE HYDRAULIC DRIVE: RexPak standardized hydraulic power units with AC motors are now available with the DFEn variable-frequency pump drive, saving energy and reducing noise (left photo). They offer most of the benefit of a servo drive at substantially lower cost—33% lower for a small unit, and savings are much greater on larger ones.

• SELF-CONTAINED SERVO-HYDRAULICS: Company sources at the show were particularly excited about the new 100% self-contained hydraulic axis (SHA), consisting of a servomotor, pump, small pressurized oil reservoir, all valving, and a four-area hydraulic cylinder. The custom-configurable system is available in a range of sizes and with options like a gas accumulator.