machinery feature | Twin-screw extruders
Entek has developed a new coupling system for faster screw changeovers
designs to reduce downtime during screw changeover, as this is still a “work in progress.” But Effmann says some hardware changes are in the offing, possibly for commercialization later this year. “We are looking at how the screws couple back into the gearbox, for example, and how easy it is to access the couplings. Then there’s the strand die plate: if we can make it less expensive and easier to change, it may make more sense to take it off and put in a new one, rather than clean it on the machine. “It’s lots of little things, that in the end all add up to something substantial and save our customers money. It may be something as basic as how many bolts need to be undone to take off a machine guard. Today it may be eight, but if all it took was two…” Comac also emphasizes ease of assembly and
disassembly. It has just commissioned the biggest co-rotating twin-screw extruder it has ever built. The EBC 135HT/48D was put into operation earlier this year at a key customer in Europe. It is fitted with Comac’s recently-developed barrel modules that enable faster and more convenient maintenance. The modules can be disassembled and reassembled without special tools and with reduced handling of heavy parts. In addition, correct alignment of the modules during reassembly is said to be simple. A set of spare parts for the whole barrel requires a reduced budget, and thermoregulation is very accurate thanks to the use of probes positioned very close to the inner surface in contact with the material being processed. Screws on the EBC 135HT/48D have a nominal
diameter of 135 mm and a centre-to-centre distance of 110 mm. They rotate at up to 350 rpm, with up to 14,650 Nm of torque being applied to each one. Export manager Alberto Lorioli says that the extruder has been integrated into a compounding line for the production of injection moulding granules with an output of 4,000 to 5,000 kg/h, depending on formulation.
36 COMPOUNDING WORLD | March 2014
Quick-change modules Feddem equipment is aimed mainly at compounders working with engineering thermoplastics, or making masterbatches. According to managing director Dieter Gross, the extruders are very flexible in use. The company’s latest development, shown at K 2013, is the FED 43 MTS. With its 43-mm screws, it is said to be ideally suited for the production of small- to mid-sized batches.
As with other MTS models, a wide selection of equipment options and accessories is available, and the screw units and barrels are available in various grades of steel. Adding modular sections on to extend the length of the screw and barrel is relatively straightfor- ward. Gross says that, depending on the machine, it takes one to four hours to elongate the process unit and change side-feeding/side-degassing solutions. Feddem concentrates more on flexibility required by
smaller compounders, rather than the high torque demanded by larger companies who have lines dedicated to particular polymers and even particular compounds. So MTS models currently offer torque density of 13.5 Nm/cm3
at screw speeds below 800 rpm.
But the company may offer models with higher torque in future, depending on market conditions. “We are a young company, and we can’t do everything straight away, but we are growing,” says Gross. Feddem may be a relatively new name in the
extruder market—it was only founded in 2009—but there are some famous names tucked in among its roots. The source of its technology is Siegward Rockst- edt, who began developing some innovative low-shear co-rotating twin-screw extruders well suited to compounding engineering plastics and thermally sensitive materials in the 1980s. His company, Compex, was bought by KraussMaffei and merged with Berstorff in 1999. One of the suppliers to Compex, Decroupet Maschinenbau, took on various employees from
www.compoundingworld.com
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