MACHINERY | SCREWS AND BARRELS
Right: Feddem claims its seamless barrel armouring technology prevents ingress of potentially- damaging corrosive gases
“The results from field trials using T-Profile elements on twin-screw extruders are very encouraging” says Dreiblatt. “We are identifying the most challenging applications on twin-screw extruders to validate the portfolio of HPE and to duplicate the successes we have seen on the RE RingExtruder.”
Seamless innovation German extruder manufacturer Feddem has been working hard on technologies to extend the lifespan of armoured extruder barrels and screws. According to Klaus Hojer, Business Development/ Account Manager at the company, there are a number of applications and situations where this is of utmost importance. “These include abrasive and corrosive applications, such as when mixing high ratios of inorganic fillers and reinforcements, as well as when high process temperatures are required,” he says. “In addition, they can be of use for support- ing high quality compounding processes through putting up the least resistance to heat transfer in and out of the process through the barrel walls.” In combination with Feddem’s proprietary FEM
screw elements for gentle mixing, these armoured parts can keep the performance of the compound- ing line within a tight quality range for the longest period possible, which is critically important for Industry 4.0 type installations. Lower rates of wear of barrel and screws clearly means a longer component lifetime but there are also significant financial and output advantages for operators in extending the intervals between barrel and screw maintenance work. “Currently, most compounding extruders employ
wear inserts that are shrink-fitted into the barrel segments. Mainly during the heating phase of the barrel, the shrink-fit may lose its tight connection and the efficiency of heat transfer from the barrel body into the insert suffers considerably,” says Hojer. “After considering alternatives, Feddem decided to stay with applying an armouring layer to the inner surface of the barrels. In its latest format the armouring of the main barrel borings and the opening for top/side feeding or side vacuum join seamlessly. Thus, the inside of the barrel cavity is
56 COMPOUNDING WORLD | August 2019
protected against seepage of corrosive liquids and gases into interface gaps between armouring of the main borings and armouring of the side opening. This prevents long term corrosion of the barrel body’s carbon steel material.” Hojer says that future developments at Feddem will include exploring new options in screw design for further reducing energy consumption in the compounding process and reducing machine wear. In order to increase operating times and to
reduce maintenance costs, Coperion says it focuses significant research and development activities on materials for screw elements and barrels. “This refers to the development of material combinations with increased service life and optimised properties in terms of corrosion and wear resistance. The large variety of screw configu- rations and their behaviour in the process section, as well as material properties in general, are taken into consideration to meet the increasing demands for more corrosion and wear resistant materials,” says Franziska Hagel, Engineer Research and Development, Materials Science at Coperion. “The increasing use of highly abrasive fillers or
recyclate for engineering plastics, which can have big deviations in shape and hardness, in combina- tion with the increasing power of today’s high performance extruders to achieve the most efficient operating window, demand constant further improvements. Development of new compounds or use of different raw materials, for example special chemicals as additives, are an additional challenge for the materials of construc- tion. This is one of the reasons why Coperion has improved the standard wear and corrosion protection material for barrels, especially for liners. The development from material WP 043 to WP 043+ is reflected in optimised mechanical properties, especially in the damage tolerance and corrosion behaviour. The improvements were achieved through changed manufacturing technology that optimised the microstructure,” Hagel says.
In addition to new materials, execution of wear measurements is becoming increasingly important,
www.compoundingworld.com
PHOTO: FEDDEM
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