Extruder wear reduced with housing liners from KraussMaffei
KraussMaffei Berstorff, based in Hannover, Germany, offers housing liners made of a new material for its ZE BluePower twin-screw extruder series.
KraussMaffei has found that higher demands on plastics products in terms of performance, environmental compatibility and price have a decisive influence on the compounds they are made from. More and more of these compounds are fibre-reinforced, contain special additives like flame retardants, or come with high shares of fillers and reclaimed material to reduce costs. This in turn has effects on the processing machinery, so that wear protection is an issue of ever increasing importance for compounding companies.
Andreas Madle, Process Engineer in Plastics Development, said: “We have addressed this problem and examined a large variety of metal materials available on the market. This is how we have found the perfect complement to our portfolio of materials.”
The new 72HA material – an iron-based powder-metallurgical alloy with high shares of carbon and chrome – is manufactured using the HIP method. The chemical composition of this material ensures excellent wear protection against abrasion and corrosion and facilitates mechanical processing.
Madle added: “This is why the new material offers optimum wear protection when it comes to applications with abrasive and corrosive stress, plus an extremely attractive price compared to the high-performance materials used so far.”
The liners made of 72HA material are through-hardened. "We have already manufactured the first liners made of 72HA for an extruder of the ZE BluePower series and tested them in practical use – with excellent results,” Madle said.
The company has introduced oval liners to provide optimised arrangement of the cooling and cartridge heater bores, which fit the ZE BluePower series using a large free volume at high torques. The slim liner shape enables an optimised arrangement of the cooling and cartridge heater bore for highly efficient temperature control of the housing elements. In addition, the special geometry of the oval liners prevents liner deformation in the intermeshing zone.
This improves the heat transfer from the external housing to the liner. A special contact collar ensures correct axial positioning of the liner inside the housing. For this reason, no leakage occurs at the housing connections of KraussMaffei Berstorff liner housings, which could be caused by different thermal expansion of liner and housing when the liners are not axially secured.
Andreas Madle said: “With the new metallic material, the complex geometry of the completely through-hardened liners can be produced without any problem. We are convinced that this is a unique and uncompromising alternative when it comes to wear protection.”