Stuttgart, Germany-based extrusion machinery producer Coperion GmbH has introduced a new Megacompounder ZSK Mc18 twin-screw extruder, with a high torque of 18 newton-meters per cubic centimeter (18 Nm/cm3). The torque is 30 percent higher than the firm's previous highest level on the established Megacompounder ZSK Mc Plus machines.
Thomas Kehl, the Coperion board member responsible for engineering thermoplastics and special applications in compounding and extrusion equipment, claimed at K 2010 in Dusseldorf that the Mc18 is now No. 1 in torque.
Kehl also said at the K show that the Mc18 will replace both the established Mc Plus and ZSK machines which will leave the company with two ZSK series: Mc18 and Megavolume.
A new shaft has been designed by Coperion using aerospace-proved materials to ensure that Mc18 screws can withstand the high torque. While the materials have established use in aerospace applications, Kehl said that, under a joint venture agreement exclusively to Coperion, they are available for use in machine screws.
Aside from the torque value, Kehl said there are a number of other advantages with the new machine. The Mc18 enables higher filling between screw flights and less wear on the product through lower compounding temperature, even at high throughput. And by moving from plate to cartridge heating, heat is brought closer and more precisely to the product, Kehl said.
Coperion presented data comparing throughput of ZSK 45 Mc18 and Mc Plus extruders in compounding 30 percent glass-fiber-reinforced nylon 6 at K 2010. At a screw speed of 600 rpm, the Mc18 achieved 600 kilograms per hour, the Mc Plus 400h. At 1,100 rpm, the Mc18 had throughput of 1,000 kg/h, compared with about 700 kg/h for the Mc Plus.
There are interesting commercial aspects too. The Mc18 has lower operating cost, with lower maintenance needs, easier access for cleaning and 13 percent lower energy, all making important contributions to lower total cost of ownership, Kehl said. The result is a machine that is more affordable per kilogram than before, Kehl said.
According to Coperion, energy consumption has also been cut through better heat transfer due to use of shrink-fit oval barrel liners, improved barrel insulation and with the cooling system now providing more uniform temperature distribution.
In specific energy consumption, Coperion has been shifting the level down from the Mc through Mc Plus to the new Mc18. While compounding glass-fiber-reinforced nylon, a typically high-energy-input process, at screw speed of 1,000 rpm, the Mc takes 0.21 kilowatt-hours per kilogram, Mc Plus just over 0.20 kwh/kg and the Mc18 about 0.19 kwh/kg.
Similarly, at 600 rpm, specific energy consumption for the Mc is just above 0.19 kwh/kg, dropping to around 0.18 kwh/kg with the Mc Plus and to around 0.17 kwh/kg for the new Mc18 version.
At K, Coperion showed a ZSK Mc18 machine with an 18-millimeter screw diameter, revealing that the Mc18 is available in eight screw sizes, from 32-119mm.
Screw configuration is adapted according to the application to ensure optimum melt uniformity, the company said.
The maintained 1.55 ratio between outer and inner screw diameters is said by Coperion to represent the very optimum in terms of transmissible torque and free volume. It also enables scale-up and modernization of the existing ZSK Megacompounder Plus to the new ZSK Mc18, the firm said.
Coperion has been progressively increasing the torque of its ZSK compounding extruders. The level was in the below 2-3 Nm/ cm3 level in the 1950s with respectively the ZSK and ZSK Variable models, rising to around 8.5 Nm/cm3 in 1965 with the ZSK Supercompounder, to just under 12 Nm/cm3 with the ZSK Megacompounder in 1995 and to around 13.9 Nm/cm3 in 2005 with the ZSK Megacompounder Plus.
At K, Coperion said Siemens and two other suppliers provide the Mc18 gearbox.
A torque level of 15 Nm/cm3 had been claimed as a record by Coperion competitor Leistritz AG of Nurnberg, Germany, with its Maxx series of co-rotating twin-screw extruders. Coperion's new Mc18 range has therefore advanced beyond the torque level of the present Leistritz Maxx machines.
Meanwhile, Bangalore, India-based extrusion machinery maker Steer Engineering Pvt. Ltd. has come close to the Maxx value, with a specific torque of 14.5 Nm/cm3 given for its Omega 30H extruder, on display at K.