Abstracts Category : Other

Synchronized material deposition rate control with path velocity on fused deposition machines

by Deniz Sera Ertay

Additive manufacturing (AM) technologies are used in three-dimensional (3D) printing of parts by depositing the material layer-by-layer on the computer numerical controlled machine tools. While laser and electron beam guns are used to melt, and deposit the metals, thermoplastic materials are heated and deposited by the extruders. When the material deposition is not synchronized with the tangential velocity of the machine, an excess material is accumulated at sharp curvatures where the machine slows down. This thesis presents a novel algorithm for the synchronized deposition of thermo-plastic materials with the tangential path velocity of the machine under constant temperature. The temperature of the thermoplastic filament needs to be kept at a constant temperature (i.e. 220 Celsius) in a heater chamber. The transfer function of the temperature and current input to the heater is modelled as a first order system whose parameters are time varying as a function of materials extrusion rate. An adaptive pole placement controller is designed to maintain the temperature of the material by manipulating the current supply to the heater as the extrusion rate vary. The tool path is first smoothed by a fifth order B-spline. The tangential path velocity is also smoothed by a third order spline while respecting heaters power limit as well as the jerk, acceleration and velocity limits of two drives which are used in printing the material layer by layer. The extrusion rate is controlled proportionally to the tangential path velocity while keeping the temperature of the deposited thermo-plastic material at the desired temperature by adaptively controlling current supply to the heater. The experimentally proven algorithm leads to more uniform material deposition at sharp curvatures and resulting improved dimensional accuracy of printed parts. The proposed methodology can be extended to laser and electron beam based metal printing applications.