In context
In 2023, industrial robots were increasingly considered for large-part milling due to their low cost and large workspace compared to CNC machines. However, their inherently lower stiffness and trajectory accuracy posed challenges for machining stability, making research into the interplay between robot precision and chatter critical for advancing robotic automation in manufacturing.
What was reported
Researchers from Beihang University and Huazhong University of Science and Technology investigated how robot trajectory tracking errors influence regenerative chatter in milling. They measured trajectory errors using a laser tracker, finding fluctuations up to 0.12 mm in the Z-axis when moving along X, with dominant frequencies around 13 Hz. These errors were modeled as periodic disturbances affecting dynamic chip thickness and introducing multi-delay effects.
A dynamic cutting force model incorporating trajectory errors and process damping was developed. Simulations showed that trajectory errors increase cutting force amplitude and can alter stability. The model predicted that trajectory errors increase the critical axial depth of cut, expanding the stable region, but at the cost of reduced surface quality and dimensional accuracy.
Milling experiments validated the model, confirming that trajectory-induced dynamic chip thickness changes, time delays, and increased process damping can stabilize the process. The model also explained a peculiar phenomenon where chatter occurs and then disappears during robot milling, attributed to the influence of trajectory errors on the regenerative chatter dynamics.
Why it mattered
This work provided a theoretical foundation for predicting and controlling chatter in robotic milling, enabling manufacturers to optimize cutting parameters for higher efficiency while managing stability. It highlighted that trajectory accuracy, often overlooked in favor of stiffness, plays a significant role in robotic machining performance, guiding future development of compensation strategies and process planning for industrial robots.
The proposed theoretical model explains the special phenomenon that the chatter occurs and then disappears in the robot milling experiment.
Source: 《机器人》期刊 (robot.sia.cn) · Published 2023-03-11 · “机器人轨迹跟踪精度对铣削再生颤振的影响”