MACHINERY | TWIN-SCREW EXTRUDERS
Step-by-step tips on element removal
Removing elements from extruder shafts is a necessary task but not always an easy one. Leistritz Extrusion Technology provided some tips on removing stubborn elements in its latest extrusion newsletter. 1. Work on the screws immediately after cleaning off the outer surfaces and, if possible, while they are still hot. If they have cooled, put them back into the hot extruder barrel for 20 minutes or so to heat up again. The separate them and work on each one at a time. 2. Support large screws evenly using blocks as long shafts can deflect and cause assembly issues. 3. Unscrew the tip (wear gloves) then try to slide off the final element. If it will not slide off, heat it with a propane torch This may take some time. Apply heat evenly. 4. Remove the warmed element by sliding it straight toward the shaft end. If it still doesn’t move, an off-the-shelf pneumatic impact hammer fitted with
IMAGE: LEISTRITZ EXTRUSION TECHNOLOGY
Above: Removing elements for cleaning or screw reconfiguration can be simplified using a structured approach
a brass tip may be needed. 5. When using the impact hammer, angle the brass punch against the screw flight and in the direction you want it to move and give it a few hits. Continue the heating and hammering cycles until the element moves. 6. Once the element is off, repeat the above process for the next. As each element is removed, brush-clean and scrape the exposed shaft to make it easier to remove subsequent elements. �
https://extruders.leistritz.com/en
the company has made a “critical breakthrough” in enhancing fatigue strength of working components and in particular those in dynamic movement such as screw shafts, gearbox shafts and screw elements. “We have also advanced metallurgies, material treatment and hard facing solutions to ensure that the most stringent and demanding applications for wear and corrosion can be addressed with maxi- mum life expectancy,” he says. On the business front, Padmanabhan likely
speaks for many when he says the company sees a considerable amount of pent-up demand being released in 2022, giving rise to investments as well as better utilisation. “We see business willing to experiment and try alternatives in the “new normal,” able to question and justify changes speci- fications that were never changed for decades in component drawings. We see that the business leaders are less risk averse and more risk aware since the advent of the pandemic,” he says. Germany’s Coperion has optimised its SK92 die
head for improved throughputs, incorporating a number of “smart” feartures. In a single row configuration, the optimised die produces 100 strands; double row versions produce 160 strands.
20 COMPOUNDING WORLD | March 2022
IMAGE: LEISTRITZ EXTRUSION TECHNOLOGY
Above: An impact gun with a brass tip can help loosen stuck screw elements without risk of damaging elements or shafts
The company says the new die head uses an intelligent heating/cooling concept to ensure highly homogeneous temperature distribution is achieved across its full width. In addition, flow geometry has been optimised to enable uniform output with only minimal pressure loss. Smart features on the SK92 are said to greatly simplify its maintenance and operation. For example, all mounting bolts can now be loosened in a single circular motion while a telescopic rail on the swing arm makes moving it aside a simple task that can be carried out by one technician. It also reduces the time required to gain access to the process area, helping to make screw changes and die head cleaning very fast. After exiting the die head, extruded strands
transfer to an automatic strand conveying system (ASC) where they move to the pelletiser’s feed mechanism via a cooling water chute and then a conveyor belt. Start-up is fully automatic, as is the conveying and rethreading of broken strands, eliminating product loss and without interrupting production. Coperion’s largest automatic strand conveying system, the ASC 700, is said to be appropriate for compounding systems running at
www.compoundingworld.com
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