January 2020

Vector control solves problems in paper cup machines W e don’t usually pay much attention to paper cups, but we rely on them to meet high quality standards day after day. They must keep their contents warm without burning our fingers, and must not leak or spill. And billions of them need to be produced in a cost-effective manner. The German machine-builder, Michael Hörauf Maschinenfabrik, specialises in equipment for producing disposable cups. As well as making machines for the efficient production of paper cups, it also supplies machines to branded companies which use them to produce laminated paper packaging in-house. Hörauf’s BMP 100 machines can produce cups economically at speeds of up to 180 cups per minute. There are two variants: one makes cups for hot and cold beverages such as coffee; the other produces the packaging cups in which instant snacks, popcorn, noodles are sold. Both machines can work using either blanks (paper segments) or rolls as raw materials. The company’s expertise is based on many years of experience of reshaping and joining paper or paper composites. The heart of these machines is a 1m- diameter mechanism, known as the “star”, incorporating a ring of “spikes” on which the paper cups are formed This structure needs to be accelerated and decelerated during each of the 180 cycles every minute. The mechanically demanding drive task is handled by an induction motor. Hörauf was experiencing two issues resulting from regenerative operation of this motor that occurs during braking. First, voltage surges were putting a heavy strain on the drives and leading to failures. Second, converting the regenerative energy into heat during braking, was resulting in braking resistor temperatures rising as high as 80°C. Because of the use of highly flammable paper in the production process, it was not possible to install the braking resistors outside of the control cabinets. The excess heat therefore had to be removed from the control cabinets at a significant cost. In light of these issues, Hörauf’s designers set out to find a drive that would satisfy the cup-making machines’ high mechanical requirements without generating heat. They chose a Yaskawa’s GA700 drive are run it in open-loop vector control mode. The dynamic current vector control operation has minimised the overshoot of the mechanics, as well as limiting the voltage peaks. The spikes were reduced by 30%, resulting in less regenerative energy being produced. The temperature of the braking resistors now remains similar to the ambient levels, thus optimising the cooling performance of the entire machine. n A drive operating in an open-loop vector control mode has helped to a German machine- builder to solve issues in machines that produce up to 180 paper cups every minute. The drive has helped to curb voltage spikes, losses and braking resistor temperatures. 32 n VARIABLE-SPEED DRIVES January 2020 www.drivesncontrols.com Cups are formed on the 1m-diameter“star”at the heart of the machine, which is accelerated and decelerated 180 times per minute. Photo: Michael Hörauf Maschinenfabrik The machines that are used to produce paper cups are extremely complex and result in challenging electrical and mechanical loads Photo: Michael Hörauf Maschinenfabrik