Strand width uniformly control for silicone extrusion additive manufacturing based on image processing

The strand width during silicone extrusion additive manufacturing (AM) tends to be uneven due to the viscosity change of non-Newtonian fluid silicone, the uncertain friction of the nozzle inner wall, the influence of the ambient interference, and other uncertain factors. To overcome this problem, a method for controlling the uniformity of strand width in silicone extrusion AM based on image processing is proposed. Firstly, the image of the strand is collected frame by frame by a charge coupled devices (CCD) camera, through a series of processes of image acquisition, image processing, and information extraction, the width of the strand is obtained. Then, the theoretical relationship between the strand width of the gradient region and the nozzle movement speed is obtained through experimental research, according to the relationship, PID control, smith PID control, and inverse function control are designed. At the same time, a pretreatment method is designed to optimize G code by speed planning software before printing. Finally, the trend of strand width under controlled and uncontrolled conditions during the silicone AM process is simulated, the control effect of strand width uniformity can be improved by optimizing the controller, and the simulation results show that the strand width uniformity in the silicone AM process with smith PID controller is the most stable. In addition, experiments are designed to verify that the strand width pretreated is more uniform than those without pretreatment. Therefore, the instability of strand width in silicone extrusion AM process can be effectively improved by image processing control and pretreatment.