PROCESSING | SMALL BATCH COMPOUNDING
Two-piece screw tips make for easy and quick removal of screws from the extruder barrel for cleaning. The tip cover is removed (image on the left) to reveal the stud for attachment of a screw pulling fixture while the tip bolt remains engaged to keep the elements tensioned
Source: CPM Extrusion
compounding – to get the machine up and running as quickly as possible,” he says. Dreiblatt adds that providing operating staff with the right tools can dramatically improve changeo- ver time, but points out that while it sounds obvious it is certainly not always the case. “Consider two scenarios. At one compounder, the operator is instructed to clean the machine. They are given a broken screwdriver and bent spatula. As a result, it takes a long time to perform the requested tasks and the operator doesn’t feel great about the quality of work. This is because the company did not want to spend money on a few tools. “At the second compounder, the operator is given an assortment of special wire brushes that are perfectly sized to clean die holes, etc. The procedures specify to use each brush once, then dispose of them. In the end, the cleaning is finished quickly and the operator feels great about the qual- ity of work. Spending money on such things actually ends up costing less in the long run.”
Configuration gains Klaus Hojer, Business Development and Project Manager at Feddem, says its compounding
Figure 1: Yield comparisons for compounding extruders equipped with kneading block and kneading block-free screws Source: Feddem
18 COMPOUNDING WORLD | April 2020
extruders are normally equipped with kneading block-free screws that employ its proprietary FME mixing elements. “Some of Feddem’s customers produce 80% of their engineering plastic compound recipes on one screw configuration, saving a considerable amount of production time by minimising the frequency of exchanges of processing screws,” he says. The benefit of this arrangement is shown graphically in Figure 1. The wide-range performance of screw geom- etries using FME mixing elements allows produc- tion of the same high product quality on different Feddem extruder sizes, Hojer says. “In production setups with different sizes of Feddem extruders a production job can be matched to the best suited extruder. The ratio of ‘duration of the production run’ to ‘unavoidable start-up/shut-down losses in raw materials’ is optimised and idle times of the extrusion lines through screw exchanges are avoided. The quality of the produced compound is the same.” Feddem’s compounding extruders are also available with modular extensions of the process- ing section. The company says conversion from a shorter to a longer length can be executed through the use of one or more extension kits, each 10 L/D long, within a few hours. This means the processing length of the extruder can rapidly be adapted to the requirements of the process. Another machine feature that is claimed to contribute to faster product changeovers is Feddem’s FSK die head. This features a curved die plate that is claimed to relax the melt flow to the die holes across the width of the plate and equalise differences in flow speed between holes. “Some customers report that it takes only 50% of the time during production start-up to reach stable strand performance compared to start-ups with conven- tional straight die hole arrangements,” Hojer says. Feddem says the FSK die heads can be customised to fit extruders of other brands.
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www.compoundingworld.com
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