Browsing by Author "Bandari, Yashwanth K."
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Item Open Access Compensation strategies for robotic motion errors for additive manufacturing (AM)(University of Texas, 2016-08-10) Bandari, Yashwanth K.; Charrett, Thomas O. H.; Michel, Florent; Ding, Jialuo; Williams, Stewart W.; Tatum, Ralph P.It is desirable to utilise a robotic approach in additive manufacturing as Computer Numerical Control (CNC) is expensive and it has high maintenance costs. A robotic approach is relatively inexpensive compared to CNC and can provide much more flexibility, enabling a variety of configurations and easier parallel processing. However, robots struggle to achieve high positioning accuracy and are more prone to disturbances from the process forces. This paper attempts to characterise the robot position and velocity errors, which depend on the build strategy deployed, using a laser speckle correlation sensor to measure the robotic motion. An assessment has been done as to whether these errors would cause any problem in additive manufacturing techniques, where the test parts were built using the Wire+Arc Additive Manufacture (WAAM) technique. Finally, different compensation strategies are discussed to counter the robotic errors and a reduction of 3 mm in top surface profile irregularity by varying the wire feed speed (WFS) during the path has been demonstrated.Item Open Access Laser speckle velocimetry for robot manufacturing(SPIE, 2017-06-26) Charrett, Thomas O. H.; Bandari, Yashwanth K.; Michel, Florent; Ding, Jialuo; Williams, Stewart W.; Tatum, Ralph P.A non-contact speckle correlation sensor for the measurement of robotic tool speed is presented for use in robotic manufacturing and is capable of measuring the in-plane relative velocities between a robot end-effector and the workpiece or other surface. The sensor performance was assessed in the laboratory with the sensor accuracies found to be better than 0:01 mm/s over a 70 mm/s velocity range. Finally an example of the sensors application to robotic manufacturing is presented where the sensor was applied to tool speed measurement for path planning in the wire and arc additive manufacturing process using a KUKA KR150 L110/2 industrial robot.Item Open Access Laser speckle velocimetry for robot manufacturing(Cranfield University, 2017-07-04 15:10) Charrett, Tom; Bandari, Yashwanth K.; Michel, Florent; Ding, Jialuo; Williams, Stewart; Tatam, RalphData files associated with SPIE Optical Metrology, Munich 2017 paper: Thomas O. H. Charrett ; Yashwanth K. Bandari ; Florent Michel ; Jialuo Ding ; Stewart W. Williams ; Ralph P. Tatam; Laser speckle velocimetry for robot manufacturing . Proc. SPIE 10329, Optical Measurement Systems for Industrial Inspection X, 103291Z (June 26, 2017); doi:10.1117/12.2269989Item Open Access A non-contact laser speckle sensor for the measurement of robotic tool speed(Elsevier, 2018-04-23) Charrett, Thomas O. H.; Bandari, Yashwanth K.; Michel, Florent; Ding, Jialuo; Williams, Stewart W.; Tatam, Ralph P.A non-contact speckle correlation sensor for the measurement of robotic tool speed is described that is capable of measuring the in-plane relative velocities between a robot end-effector and the workplace or other surface. The sensor performance has been assessed in the laboratory with sensor accuracies of ±0.01 mm/s over a ±70 mm/s velocity range. The effect of misalignment of the sensor on the robot was assessed for variation in both working distance and angular alignment with sensor accuracy maintained to within 0.025 mm/s (<0.04%) over a working distance variation of ±5 mm from the sensor design distance and ±0.4 mm/s (0.6%) for a misalignment of 5°. The sensor precision was found to be limited by the peak fitting accuracy used in the signal processing with peak errors of ±0.34 mm/s. Finally an example of the sensor’s application to robotic manufacturing is presented where the sensor was applied to tool speed measurement for path planning in the wire and arc additive manufacturing process using a KUKA KR150 L110/2 industrial robot.Item Open Access Oxidation of Ti-6Al-4V during wire and arc additive manufacture(2019-04-08) Caballero, Armando; Ding, Jialuo; Bandari, Yashwanth K.; Williams, Stewart W.Owing to the high reactivity of titanium with oxygen at high temperatures, oxidation is often observed during wire and arc additive manufacture (WAAM) of Ti-6Al-4V. As a sign of oxidation, discoloration of titanium components built by WAAM is usually observed, due to the formation of a thin oxide scale on the surface. This generally constitutes a major concern from the end user. Together with the oxide scale, oxidation also produces the formation of a brittle oxygen-enriched layer near the surface (Alpha Case) and it can be detrimental in terms of mechanical properties. Hence, it is of major interest to investigate the influence of surface oxidation on the bulk material property of WAAM of Ti-6Al-4V and understand the oxidation process during WAAM deposition. In this work, oxidation of titanium during WAAM was investigated to determine the mechanisms and main process parameters controlling this phenomenon. To address this, plasma-transferred arc and wire deposition samples were manufactured by changing either deposition parameters or oxygen levels in the fusion atmosphere. Subsequently, samples were characterized by means of visual inspection, optical microscope, scanning electron microscope, and tensile mechanical testing. For any containing level of oxygen in the shielding environment, it was found that if temperatures are high enough and exposure times long, oxidation of titanium is observed. In addition, it was possible to determine that oxidation is more significant in the region of the first deposited layers. The maximum depth of Alpha Case was found to be 200 μm for the samples built with higher current (220 A) and wider oscillation width. Tensile testing revealed that increasing 40 times the oxygen levels in the shielding environment does not affect the tensile strength significantly.