Speed and precision come together in two new sizes of Roboshot SiB injection molding machines that offer high-speed injection capabilities as standard. When equipped with an 18-mm screw, the Roboshot SiB-m can inject 18g (.63 oz) of resin at more than 2450 bar (35,550 psi) with a maximum velocity of 330 mm/sec (13 in/sec) and a fill rate of 84 cm3/sec (5.1 in3/sec). Available in 165 and 275 tons of clamping force, the machines' injection units accelerate at a force of .86G thanks to a low-mass, high-power injection motor newly developed by Fanuc-a stalwart in servomotor technology with 22,000 all-electric Roboshot machines produced to date.
Milacron (Cincinnati, OH) is promoting the machines for micromolding, applying all-electric precision to high-pressure injection. By using a combination of a ball screw and an electric motor, the machine is said to change speed and direction with precision, pointing out that hydraulic presses with accumulators can accelerate quickly but lack the same level of control thereafter. Mircrosecond velocity profiling at high speeds creates a wider processing window, which ultimately means less overall scrap.
In terms of mold clearance, the 165-ton press has tiebar spacing of 510 by 510 mm (20 by 20 inches) with a platen size of 750 by 750 mm (29.5 by 29.5 inches). The 275-ton Roboshot has tiebar spacing of 710 by 710 mm (28 by 28 inches) and a platen size of 1030 by 1030 mm (40.6 by 40.6 inches).
Milacron officials say the machines are geared towards markets like medical molding, cosmetics, mobile phones, and connector industries. The SiB line comes with Milacron's artificial intelligence (AI) control, which has been upgraded to include ejector- and mold-protection features. Mold protect has been refined, and now divides tool close into three distinct zones with separate high-force limits for each zone. Ejector protection monitors the load on the eject servomotor, with a high-load alarm that can automatically stop the cycle if setpoints are exceeded. The system is sensitive enough that it can be used to pass or fail parts by determining if overpacking or flash occurred. The metering function determines an ideal recovery cycle and then sets the screw RPM to that figure with a reported repeatability of ±.2 second. Milacron Inc., Cincinnati, OH, USA; http://plastics.milacron.com