For over 50 years the German company Leistritz Extrusionstechnik GmbH manufactures twin screw extruders and complete lines for plastics processing, having gained the reputation as one of the leading manufacturers of twin screw extruders with codirectional rotation – due to the company’s continuous inventions in terms of screw speed, geometry and torque, limited only by the maximum load of screw shafts. Leistritz offers customers the extensive company’s experience and know-how in various areas of plastics processing, such as the production of color or additive masterbatches, compounding of various materials (polyolefins, polystyrens, thermoplastics, elastomers, etc.), direct, laboratory and pharmaceutical extrusion.
At Interplastica-2013 the company exhibits equipment of the ZSE MAXX series, designed in complete accordance with the corporate motto “Refreshing extrusion technology” - at the cutting edge of technology. Having the high torque (up to 15.0 Nm/cmі) and increased screw filling volume (the ratio of outer diameter to the inner one = 1.66), the extruders of ZSE MAXX series open the new opportunities, allowing to simultaneously increase productivity, product quality and ensure stable operation. So, if previously processors had to choose between high volume and high torque, in ZSE MAXX both benefits are joined in a single set. ZSE MAXX comprises extruders with screw diameters of 27 to 180 mm. Due to the modular design of barrel and screw system, as well as thought-out drive with various gearboxes and engines (up to 1200 rpm), these extruders can be used in a great variety of applications.
As a recent example, consider the use of this equipment in the Russian company Visa (Samara), a supplier of automotive components. In production the company uses a modern line for manufacturing noise-insulating sheets with integrated compounding system. “At the site of Visa group our extruder ZSE 87 MAXX is installed, equipped with the modern dosing and feeding systems, - tells Klaus Heinrich, Sales Manager of Leistritz Extrusionstechnik GmbH. - Materials are fed to extruder through the three feeding zones. It is necessary to provide extremely high filler content, which exceeds 80 percent, and input it to polymer.” After pre-mixing, polymers and fillers are conveyed via gravimetric devices to the main extruder inlet. Besides, above side feeders two additional gravimetric devices are installed. Calcium carbonate or barium sulfate are transferred to gravimetric devices by the screw feeders.
“Then the side feeders convey fillers to processing zone of twin screw extruder, - continues Mr. Heinrich. – A precise selection of composition is required to comply with process requirements. Of the special value are also the screws filling volume, melt temperature, material residence time and degassing.” Accordingly, the screws geometry, rotation speed, extruder load and temperature profile must be perfectly adapted to the process parameters. ZSE 87 MAXX is rotated by a water-cooled three-phase drive, which provides a very high torque. A soon as extruder also has a large screws filling volume, it ideally suits the task stated. The stage of vacuum degassing at the end of the working area is also playing an important role – just here the volatile components are removed from the melt, thus allowing to obtain extremely homogeneous melt at the exit.
In order to ensure a steady flow of material, the melt channel ‘extruder outlet’ – ‘extrusion die inlet’ must be heated. In the given project a melt pump is not used. “The extruder provides sufficient pressure. So it was a logical decision, thus allowing therewith to reduce costs”, - noted Mr. Heinrich. The heated flat die can be accurately adjusted to desired product characteristics. The formed sheet is cooled on located further calendar and optimized to desired thickness. Then a sheet with a width of about 2 meters is cooled in a special section. “Next, the sheet is conveyed to a notching press, where the parts of different shapes are cut out – the process is similar to cookies preparation. Then the parts are prepared for the next production stage, which is already held in an assembly shop of automaker, - explains Mr. Heinrich. – Only thoroughly considered conformity of all the components of production line can make easier manufacturing of high quality products.”