Right: Coperion K-Tron’s new K3 vibration feeder provides accuracy and consistency

rotating and not moving in parallel only,” he says. “This means that you have different material speeds over the tray length. The material height along the feeder is not constant. The disadvantage is that the scale indicates that there is not enough output, so it sends a command to provide a higher amplitude. The feeder is always reacting to these changes in material height, but there is always a delay.”

Helfenstein has invented a system

that uses pendulums instead of rubber feet or springs. The pendulums can only move in the direction of vibration, so the tray is always moving with a parallel motion. This, he says, provides a constant material height. “There is virtually no delay between setting a command to change output and the output actually changing, yielding an improvement in output accuracy of 35%.” The advanced control system and feeder

electronics include internal sensors which measure acceleration, displacement, load, current and temperature at rates of up to 25,000 times per second. The controller then adjusts the vibratory drive signal to maintain clean sinusoidal displace- ment for optimal mass flow. “Even with the smallest vibrations we still have a constant amplitude,” Helfenstein says. This is said to make it possible to use the same feeder for feeding quantities any- where from 4 to 2000 kg/h, with the same high level of accuracy (another version soon to be launched can dose up to 8 tonnes/h). The version more appropriate for laboratory

Right: Cross- section of the processing section of the new planetary lab extruder from Entex

work offers a range of around 1-500L, or 500g to 250 kg/h with a standard tray. A special tray makes even lower levels possible. The company claims that the flexibility the new system provides can be a big advan- tage in laboratory applications.

In addition, the feeder is especially gentle on the material, which also manifests itself in the amount of energy the feeder consumes: 25 times less than a screw feeder.

Lab alternatives

It’s not just twin-screw extruders that come in lab versions. Entex showed its L-WE 30 labora- tory planetary extruder at K2019. It has an output of between 0.5 and 10 kg/h. As with larger versions, some of which can process as much as 8 t/h, it has a modular construction that allows for spindles of various designs to be used in the planetary sec- tions. There are three cylinder assemblies (one planetary feeding cylinder and two others) with six standard planetary spindles per cylinder. These rotate around a central spindle. Modularity extends to the plug-and-play heating and cooling units, which fit under the table supporting the processing system and provide highly precise temperature control (see Compounding World October 2019). Buss is preparing a laboratory addition to its

latest Compeo series of kneaders. The company says it will feature a 44mm tempered screw shaft and exhibit all of the main features of its larger siblings. This includes a configurable barrel housing with process lengths ranging from 11-25 L/D and the possibility to combine two, three, four and six flight elements, side feeders, an active de-gassing zone, high temperature electric heating system and much more. The base model is currently planned to feature a 70mm single-screw discharge unit, with the option to upgrade to a 35 mm counter-rotating conical twin screw unit. The design of the new machine should be finalised earlier next year, with first deliveries possibly around mid-2020. “A primary focus of the design is to provide a holistic solution from raw material to finished pellets,” says Design & Development Engineer Dino Kudrass. “We want to supply a compact and well-integrated system with flexible dosing equipment that communicates with the kneader control and allows for fast and comfortable refills. The same goes for the strand or underwater pelletiser system, which should not be merely

20 COMPOUNDING WORLD | December 2019



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