Among the packaging machinery OEMs that have moved from pneumatics to servo motors for their motion axes is Multivac, a leading maker of thermoformers and tray sealers used in a wide variety of food, pharmaceutical, and other consumer packaged goods applications.
“Servo technology increases controllability and reduces noise emission. These systems also help us to increase the number of production cycles,” says Guido Spix, Chief Technology Officer at Multivac. He adds that his firm’s use of motion control solutions from Kollmorgen reduces energy consumption, increases overall machine effectiveness, and improves safety of packaging processes.
Compared to traditional, mostly pneumatic lifting units, the new lines of Multivac machines utilize a motor-gearbox combination to deep draw the forming web and heat seal the lidding material. These units utilize a knee-lever mechanism to lift the molding tools, some of which weigh several hundred kg. They withstand the high bonding pressure of up to 20 tons, ensuring the two materials seal securely. Being a strategic motion control partner for Multivac, Kollmorgen implemented a compact unit consisting of an AKM servo motor and a cycloidal gear drive for the lifting axis. Kollmorgen calculated and selected the optimal motor size and gear drive type in close cooperation with Multivac’s engineering development teams.
Two important aspects for the drive train selection were the overall unit length and overload capacity. The Model HKS03 six-point lift unit features a servo gear motor with brake having a total length of 307 mm and an acceleration torque of 1400 Newton meter. These results are possible thanks to the high-power density of the AKM servo motors, the ideal overall length of the cycloidal gear drive, and the fact that the unit comes without end bells and clutches. Piston rods convert the rotary to linear lifting motion.
This solution has three significant advantages. First, the energy efficiency of the machine increases because the pneumatic system was replaced as the power source to create the required pressure for the deep draw and sealing operation. Second, the geometry of the piston rods creates an extreme closing force at the end of travel, which improves food safety. Finally, the high sealing force results in a more secure and thus reliable sealing process.