Extrusion International 3-2018

33 Extrusion International 3/2018 In Direct Compounding Injection Moulding (DCIM), the raw material is both prepared for processing and then moulded in a single production step. This is achieved by employing a single-screw compounding ex- truder that continuously feeds material to a standard plasticiz- ing and injection moulding machine. The tip of the extruder is fitted with a switch valve for controlling the material feed to the plasticizing and injection moulding machine. There is no need for a melt reservoir; and the injection process itself is not changed. Directly processing material at a uniform temperature has both technical as well as economic advantages. This includes better material quality thanks to the fact that the material is not put under any significant thermal or mechanical stress (lower shear stress). This process also, for example, makes it possible togently and uniformly integrate longer fibres, which is very important when working with natural fibres. Forgoing the production of a semi-finished product also saves costs and energy. The DCIM technology was jointly developed by KraussMaffei, Motan-Col- ortronic and the compound developer Exipnos. Quadruple Labline dosing system – Precision component dosing The compounding extruder is supplied with material by a Gra- viplus-series gravimetric synchronous dosing and blending sta- tion fromMotan-Colortronic, Germany. The dosing system fea- tures four Lablinedosingmodules. Oneof thesedosingmodules can be automatically filled with material by a METRO conveyor, while the other three are designed to be filled manually. The dosing modules are equipped with dosing screws that are suit- able for materials with a range of different flowproperties (free flowing, average and poorly flowing). One of the dosing units has been retrofitted with a twin dosingmodule. The dosing system is modular and can be quickly and easily adapted to a range of different dosing tasks, which makes it perfect for use in the planned research project. The different modules include modules for dosing granulate, micro granu- late, powder, grinding stock and liquids. The dosing systemalso includes dosingmodules with twin screws andmixers for dosing materials that do not flow easily or not at all. The Graviplus uses the differential weighing method, which is also known as ‘loss-in-weight’ feeding. This is because loss-in- weight feeding is significantly more accurate than batch dosing as demonstrated by dosing tests conducted during a previous project. This aspect is particularly important whenworkingwith materials that are difficult to feed. The fact that the material is fed directly to the compounding extruder also means that it is near impossible for material to separate, which, in addition to the required level of dosing accuracy, was another reason for choosing a continuous gravimetric dosing system. During operation, the control unit compares the actual with the specified nominal throughput rate, which means that devia- tions are instantly identified. Thesedeviations are then compen- sated for using the dosing modules’ feed speed. The material is continuously and synchronously fed into the storage container, where it is mixed to forma homogeneous blend that is then fed into the compounder’s material feed. This process ensures that the material does not separate. Thanks to the fact that thematerial flow is constantlymonitored and controlled on the basis of its weight, bulk density fluctua- tions, particle size differences or changes in flowbehaviour only have a marginal affect on the differential system’s dosing accu- racy. This aspect is also an important factor for the research proj- ect that is going to be conducted in Rosenheim, because dosing and conveying natural fibres is considered a serious challenge. The dosing system is controlled by a Gravinet GP control unit, which is operated using a menu displayed on a 12.1” TFT touch screen. The control unit displays messages and alarms in plain text. “Apart from needing a systemwith a high level of dosing accu- racy and that would allowus to reproduce results, we alsoneed- ed one that is easy to use. With this system, changing the test set-up and the material only takes a few minutes” explained Karlinger. Research aims The technologies now available to us in wood and polymer ma- terials processing allow us to research a wide range of different material and process technologies. This research is primarily aimed at investigating and developing newmaterials and light- weight constructionmethods that will allowus to produce com- ponents fromnatural fibres in amore resource-friendly and cost effective way, and such that they are suitable for a wide range of applications. The researchers are also planning to conduct comparative tests with the DCIM and classical parallel double screw extruders with reference to the IMC injection compound- er, which is also equipped with aMotan-Colortronic continuous gravimetric dosing system. motan-colortronic gmbh Otto-Hahn-Str. 14, 61381 Friedrichsdorf, Germany www.motan-colortronic.de Pic. 3: The dosing system is controlled by a Gravinet GP control unit, which is operated using a menu displayed on a 12.1” TFT touch screen