Reifenhäuser Extends Family Of Efficient Gearless Extruders

Due to the success of its REI-Compakt gearless extruder, Reifenhäuser, Troisdorf, Germany (U.S. headquarters is Ipswich, ma), has decided to introduce a family of units with 300 to 11,000 N-m in torque. The next REI-Compakt release, a gearless extruder with a 60-mm screw and 5000 N-m of torque, will be shown later this month at NPE in Chicago (stand 2270).

More than 30 REI-Compakt units have been sold since the prototype was introduced at K2001. Dieter Thewes, extrusion center manager, says the biggest selling point of the design (Dec 01 mp, 59; mpi, 70) is energy efficiency; it uses as much as 20% less energy compared to traditional extruders. Although the extruder cost is similar to ac- or dc-motor units with gearboxes, energy cost savings reportedly amount to _10,000 over the life of the machine.

The design also substantially reduces maintenance, says Thewes, since there is no gearbox, no ac bearings to exchange after 17,000 h, or dc brushes to replace after 3000 to 7000 h. By every third brush change, a dc collector normally needs replacing, which requires two days of extruder downtime.

The lack of a gearbox makes the REI-Compakt’s footprint 30% smaller than Reifenhäuser’s standard RT extruder line. The linear motor is reportedly at least 17 dBA quieter than the European Union noise limit of 82 dBA for extruders. Since the motor is water-cooled, there is as well no dust or soot filter to clean. The unit can even be used in cleanrooms. It will not overheat in areas with high humidity and temperature, such as the Far East and southern U.S., according to Hans-Peter Krukenberg, extrusion center sales manager.

Because the linear motor is doughnut-shaped, the extruder screw can be removed from the rear of the machine, through the motor ring opening, as well as from the front. Reifenhäuser worked with linear-motor builder Etel, Mìtiers, Switzerland, during the machine’s development, but has since switched to motors built to specification by industrial equipment giant Siemens. Thewes says existing extruders can be retrofitted with the gearless motor technology.

When the entire family of seven units is available later this year, Reifenhäuser will offer machines with screws from 25 to 100 mm, and speeds from 200 to 280 rpm. A German pipe processor is currently testing the 5000 N-m unit in production. By next month, the unit will be taken out of service and disassembled to see how it withstood production conditions and how it can be improved, Thewes says.

By September, Reifenhäuser expects to install a 3-layer blown film line using two 60-mm gearless extruders and an 80-mm conventional unit for testing at its r&d center. Instead of the traditional star formation, the units will be placed parallel to each other to save space.

“Because the motors operate without oil, the extruders can be placed at any sloping angle — even vertically — to the die to save space,” Thewes notes. Traditional extruders, which can be obliquely angled from platforms, require expensive gear solutions because of the need for special lubrication, he says.

“We think this technology will alleviate the problems many processors have [with gearbox breakdowns],” Thewes adds. “Gearbox suppliers are renowned for not being able to keep up with demand for replacements. A spare gearbox can take up to six months to source, during which time the extruder is out of production.”

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