Analysis of friction error in CNC machine tools based on electromechanical characteristics

Abstract

Friction is a kind of inherent and nonlinear disturbance in feed systems, which inevitably deteriorates motion accuracy at velocity reversal. Position error caused by friction is integrally effected by three aspects of feed drives, including command, control, and mechanical subsystems. Unfortunately, the traditional analyses hardly consider all mentioned aspects. Especially, no research has been reported on control characteristic at reverse motion. The purpose of this paper is to reveal the generation mechanism of friction error of a feed drive based on the commercial computer numerical control with three-loop control structure and velocity feedforward and proportional–proportional–integral controllers. Firstly, the generation process of the friction error at velocity reversal is profoundly investigated. Based on it, a simplified control model is conducted to explain transition from presliding to sliding regimes. It is the bond of analyzing friction error from command, control, and mechanical subsystems. Subsequently, the processes of presliding, acceleration, and adjustment stages are analyzed. Moreover, analytical formulas are derived to predict the durations of three stages and describe the shape of friction error. Then, the contour errors of linear and circular motion caused by friction can be predicted online. Experiments are introduced to verify the effectiveness of the proposed methods and formulations.

Precision Machining Technology of Jewelry on CNC Machine Tool Based on Mathematical Modeling

“…The processing process is simpler than that of the small wheel. After adjusting the machining parameters of the machine tool, the two tooth surfaces of the bevel gear can be cut out through a one-time Boolean operation [11]. The solid modeling of the tooth blank and the cutter head and the adjustment of the relative position of the two can refer to the small wheel processing process.…”

A Novel Local Smoothing Method for Five-Axis Machining With Time-Synchronization Feedrate Scheduling

“…R g is the transmission ratio from the motor to the worktable. The tracking error caused by the friction is eliminated with the friction forward compensation strategy [41], [42]. Unless special stated, the main parameters are presented in Table 2.…”

All position-independent and position-dependent geometric error measurement and identification of the precision of a horizontal boring machine tool

“…In order not to interrupt the normal operation of CNC machine tools in the process of signal acquisition, the three-way sampling method is adopted through the three-way interface parallel input signal to achieve the acquisition of position information [44]. The theory relationship between the position feedback signal Pf and the speed feedback signal θv under the influence of geometric error is as follows:…”

“…To verify face line method based on built-in sensor, a Renishaw QC20-W DBB is adopted for conducting the circular trajectory measurement and the results are compared with face line method. The measurement radius is 50 mm, feed speed is 200mm /min, and measurement system is developed by our research team [44,45,[48][49][50].…”