Optimization of robotic machining through circular path error compensation

• A novel out-of-plane ballbar measurement setup is proposed for circular error analysis. • The method enables path error measurement over variable radii from 35 mm to 50 mm. • A custom small-circle adaptor enhances measurement accuracy in tight-radius regions. • Out-of-plane compensation achieves >40% circularity improvement, and 63% dimensional gain. • Comparable performance to laser tracker systems with lower cost and simpler setup. Robotic machining offers flexibility and cost-efficiency, presenting a viable alternative to conventional machine tools. However, its inherently lower rigidity and repeatability often result in reduced machining accuracy. To improve machining quality, enhancements in robotic machining are typically achieved through parameter optimization, precision calibration, path error compensation, and process refinement. This study proposes an offline path error measurement and compensation strategy based on an out-of-plane ballbar method to address these challenges. An improved small-circle adaptor, combined with a Renishaw telescopic ballbar, was utilized to measure and compensate for circular path errors over a radius range of approximately 35 mm to 50 mm in both machining and non-machining conditions. For validation, a laser tracker was employed as a reference. Experimental results from robotic machining and ballbar measurement at the non-machining condition confirm the effectiveness of the proposed ballbar-based method in circular path error measurement and compensation. Specifically, for out-of-plane angle below 30° (corresponding to circular paths of radius between 43 mm and 50 mm), the new measurement method exhibited performance comparable to that of the laser tracker, as indicated by similar circular deviation ranges, consistent radial error patterns, surface roughness, circularity compensation rate exceeding 40% and a reduction in dimensional variation to less than 0.066 mm.