No abstract

The calculation method of cutter location (CL) points only considers the geometric errors, but cannot consider the requirements of the corner transition algorithm in CNC, which results in the smoothing algorithm in the CNC not playing a maximum role or even failing. To solve this problem, a calculation method of the CL points considering corner transition speed in CNC is proposed. Firstly, the key geometric parameters of the CL points that affect the corner speed are analyzed. Secondly, according to the analysis results, the objective function is established to connect the CL points calculation in CAM and the corner transition speed in CNC. By solving the objective function, the calculation method of the CL points is developed. Finally, the effectiveness of this method is verified by experiment. Comparing with the commonly used iso-chord height method, the proposed method can increase the speed at the corner of the CL points and reduce the acceleration and jerk at the same time. By the proposed method, the tracking accuracy, trajectory accuracy, and machining efficiency can be significantly improved. The proposed method can be integrated into CAM software to generate high quality CL points.

The Dynamic Errors (DEs) of individual axes present Time-dependent Characteristics (TDCs) because the setpoints, as the input of the servo feed system, change in velocity, acceleration and jerk during the feed motion. Deep insight into the TDC contributes to the effective control of DEs. However, up to now, mechanism analysis about the TDCs of DEs are indistinct and inadequate due to a lack of analysis on the TDC of setpoint frequency. So, in this study, the mechanism of the TDC of DE is investigated by extracting the TDC of setpoint frequency. Firstly, the servo dynamics model is established for presenting the DE and its respective components, the Dynamic Error Inside Servo-loop (DEIS) (tracking error) and the Dynamic Error Outside Servo-loop (DEOS) under to and fro motions. Secondly, time–frequency analysis is carried out on the setpoints of the to and fro motions to present a TDC of setpoint frequency which is described as the Time-dependent Setpoint Bandwidth (TDSB) and the Time-dependent Potential Excitation (TDPE). Finally, the correlation between the TDSBs and DEISs and the correlation between the TDPEs and DEOSs are investigated, respectively. On these bases, the mechanism of the TDC of DE is analyzed. The results show that the TDSB, which is related to the acceleration of setpoints, accounts for the TDC of the DEIS; that the TDPE, which is related to the jerk of setpoints, accounts for the TDC of the DEOS in vibration-form; and that the TDC of transient-form DEOS is determined by the change in acceleration of the setpoints.