Online First-Order Machining Error Compensation for Thin-Walled Parts Considering Time-Varying Cutting Condition

Mirror error compensation is usually used to improve the machining precision of thin-walled parts. However, due to the time-varying cutting condition of thin-walled parts, this zero-order method may result in inadequate error compensation. To cope with this problem, an online first-order error compensation method is proposed for thin-walled parts. With this context, first, the time-varying cutting condition of thin-walled parts is defined with its in-process geometric and physical characteristics. Based on it, a first-order machining error compensation model is constructed. Then, before process starting, the theory geometric and physical characteristics of thin-walled parts are, respectively, obtained with CAM software and structure dynamic modification theory. After process performing, the real geometric characteristic of thin-walled parts is measured, and it is used to calculate the dimension error of thin-walled parts. Next, the error compensated value is evaluated to construct an error compensation surface, which is used to modify the tool center points of next process step. Finally, the machining error is compensated by performing the next process step. Two typical experiments, milling of thin-walled parts with plane- and curved-surface, are used to validate the proposed method, and the experiment results shown that this method can significantly improve the error compensation effect for low-stiffness structure. Compared with the mirror compensation, the final thickness error of thin-walled parts is reduced by 71.4% and 56.2%, respectively, for plane- and curved-surface parts.