Than, V. D.

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263 V.D. Than  National Research Tomsk Polytechnic University Tomsk, Russia Improvement of accuracy in the extrusion process  Introduction A rapid prototyping method makes it possible to produce complicated parts based on computer 3D model. Most of the rapid prototyping methods can assemble models from a variety of widespread and special materials. The modern additive technology for the most of 3D-printers requires ABS-filaments or PLA-filaments, respectively, from ABS (Acrylonitrile butadiene styrene) polymer or PLA (Polylactic acid) polymer, with a diameter 1.75 mm or 2.85 mm, which used as a consumable material in 3D printing technology. Filament obtained from plastic granules, which in case of ABS, are the products of oil and gas industry. Accordingly, the price of granules is much cheaper than the price of the finished product, even taking into account the cost of electricity consumed in the transformation of the granulate in the filament. In this article has been investigated factors affecting the diameter of the plastic filaments, as well as considered the problem of improving the quality of the filament plastic in the extrusion process. Statement of the problem A great deal of research has been conducted at universities and research institutions to expand the applications of FDM technology and to improve the FDM process. Work has also been in progress in some organizations to develop new metallic or ceramic materials for rapid fabrication of functional components by FDM with higher mechanical properties [2, 3]. In operations of the 3D-printer basic parameters affecting the quality of the finished product and fidelity digital models is diameter of the plastic filament. Therefore, to improve the production of plastic filaments, it is necessary to investigate and correct the control loop diameter plastic filament. In order to stabilize the diameter of the plastic filament, we must consider the dependence on other parameters such as the temperature in the heating zone of the screw, the screw speed, the pressure in each zone of the screw and others. Changing any of these parameters leads to a change diameter of filament. The most important parameters that have a permanent effect on the change in the diameter of the plastic filament is heating temperature and screw speed. On the base of this parameters experiment has been finished on the real object. Fig. 1 and 3 show the graphs of the experiment conducted with an extrusion installation indicating the temperature and speed of screw dependence of the diameter.   Fig. 1. Dependence of the diameter  on temperature  Fig. 2. Dependence of the diameter  on the speed of the screw 264 From the graph in fig. 1, it can be concluded that the higher the temperature, the smaller the diameter. Analyzing the resulting graph in fig. 2, we can conclude that as an increase in the drive speed causes increase in the diameter of the filament in the plastic extruder. For a simple model of the extruder, the control parameters, i.e. drive speed and the heating temperature are changed manually. The influence of external factors is not taken into account in the system; therefore, the system is not able to respond to external perturbations in the form of changes in ambient temperature, changes in the composition of raw materials, etc., thereby increasing the range of variation of the filament diameter. The arguments above lead to the need for a system of automatic control of the diameter of a loop, which could provide the necessary accuracy and speed in the production process. Solve tasks can fully developed algorithm of adaptive digital PID control. Fig. 3 shows a functional line diagram of an extruder feedback   Fig. 3. Functional diagram of the extruder line with feedback This diagram shows the connection of the probe diameter and electric installation, temperature sensor, and others. The controller is designed to form the control signal for diameter regulation when a signal comes from the sensor. Conclusion In this paper, conducted a study of factors affecting the diameter of the plastic threads, as well as consider the problem of improving the quality of the plastic thread in the extrusion process. The theoretical rationale for developing a feedback system for extrusion plant, which will improve the quality of the product, reduce the number of rejects, to ensure continuous operation for a long period. References 1. S.H. Masood, W.Q. Song, Development of new metal/polymer materials for rapid tooling using fused deposition modelling, Materials & Design 25, (2004). 2. S. Onagoruwa, S. Bose, A. Bandyopadhaya, Fused Deposition of Ceramics (FDC) and Composites, Pro SFF, Texas, (2001). 3. Fabio Previdi, Sergio Savaresi, Angiolino Panarotto, Design of a feedback control system for real-time control of flow in a single-screw extruder. 4. Qing Zheng, Senior Member and Zhiqiang Gao, An Energy Saving, Factory-Validated Disturbance Decoupling Control Design for Extrusion Processes. Scientific adviser: A.V. Yurchenko, DSc., Professor, TPU, Russia Linguistic adviser: T.S. Mylnikova, senior teacher, TPU, Russia  

Improvement of accuracy in the extrusion process

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