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MACHINERY | ALTERNATIVE EXTRUDERS


ened process lengths for plastifi- cation, the materials are exposed to shorter residence times in the system and potential material damage is avoided. Keimei says that materials are fed at the feed point via a nine screw-thread spiral groove formed


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Above: Schematic showing the layout of Keimei’s triple-screw extruder, which is said to be particularly effective for reactive processing


by three screw element units – this is said to be equivalent to a 1.5 times increase in material mixing effectiveness compared to a three-start twin screw extruder, which itself provides a doubly improved mixing action. The shallow groove structure and three- point shear configuration of the system is also claimed to achieve earlier onset of shear and consequently plasticising action and smoother degassing. In addition, the “four-state variability” feature of the gearbox means that the phase of three of the screw shafts can be changed to adapt the system to different feeding materials. Inside the barrel, the amount of shear produced


per screw shaft rotation is tripled when compared with a three-start-screw twin screw extruder, the shear force introduced into the processing material is 1.5 times higher, and the mixing effect across the same cross-sectional area is three times that of a three-start-screw twin screw unit. The company says it has achieved good degassing results as the surface area of the material exposed on the screw surface (the gas exchange area) is 1.5 times higher than that of a three-start twin screw extruder. And the “stirring” effect is three times higher in the cross section.


Planetary roll The latest addition to the Entex planetary roller extruder is a degassing reaction module - Ermo. The company says that this offers a significantly increased process chamber volume in comparison


to the conventional cylinder assembly. It has been developed specifically for degassing applications, where free large-scale process surfaces and large flow cross-sections are important. The unit maxim- ises these aspects without significantly changing the size of the extruder, the company says. Entex adds that Ermo is also an advantage when used for the addition of fillers with a particularly low bulk density, where the largest possible free cross sections are needed. A further application area is in reactive extrusion, where extending residence time or enlargement of the reaction surface or volume are required. Like all other components of the modular Entex system, several Ermo units can be used in series or at separate positions in a production line. In addition, there are various other options such as side feeders, injec- tion and degassing openings.


Recycling concepts The Gneuss Processing Unit (GPU) – which com- prises an MRS extruder for devolatilisation and decontamination in combination with a Rotary Filtration System and online viscometer for intelli- gent dynamic viscosity control – is widely used for reprocessing bulky PET waste, such as post-con- sumer bottle flake and industrial waste from fibre and film manufacture without pre-drying. Although originally developed specifically for PET, the MRS extruder component is now also running in polyole- fin and nylon applications, and is being tested on a range of other materials and applications. Gneuss says that the combination of single


screw extruder with a multiple screw section means that the MRS extruder is sturdy and particularly well suited for recycling applications. According to the company, the MRS extruder permits processing of PET without pre-drying by using a simple water ring vacuum system. This is achieved by means of its unique processing section. Based on a conven-


DS aims to cut extruder downtime


Compounders operating Davis- Standard single or twin screw extruders and compounding systems can now cut potential downtime risk using a new continuous monitoring system – Activ-Check. The system offers real-time


predictive maintenance by provid- ing early notification of potential extruder failures via e-mail or text. Continuous monitoring covers key


22 COMPOUNDING WORLD | October 2018


parameters such as extruder reducer, lubrication system, motor characteristics, drive power unit, barrel heating and cooling, accord- ing to the company. The system is said to be easy to


operate. Users simply touch a location to view details or use on-screen set-up for e-mail or text notifications. Vibration sensors on the extruder


reducer provide data regarding the condition of the gears, bearings and lubrication system. The extruder motor is supplied with combination temperature sensors and vibration sensors. The reducer lubrication system (if provided) on the machine installation, includes pressure, flow and temperature sensors to indicate system performance. � www.davis-standard.com


www.davis-standard.com/extrusion_system/process-controls www.compoundingworld.com


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