New Linear Motor Controls Contact Rolls

A new permanent-magnet motor from Siemens AG in Germany greatly simplifies control of contact rolls in high-speed film winding.

A new permanent-magnet motor from Siemens AG in Germany greatly simplifies control of contact rolls in high-speed film winding. The German parent of Bruckner Inc., Greenville, S.C., applied for a patent on this use of the motor. Bruckner’s first Liwind system with this motor was installed last August at Manuli Film SpA in Italy on a 10-meter-wide BOPP line. Siemens’ linear motor is shaped like a plank roughly 1 meter long x 10 cm high x 20 cm wide. It has electrical windings on a rectangular core and a permanent magnet that slides back and forth over the windings. This simple, compact motor replaces a combination of several hydraulic and pneumatic cylinders plus a damping unit to position the contact roll, control contact pressure, and compensate for roll dancing. The Liwind motor and a new super-light contact roll can regulate contact pressure from 10 to 400 N/m with 0.01-N/m resolution.