Research on fault early warning and the diagnosis of machine tools based on energy fault tree analysis

At present, the status of the monitoring of computerized numerical control machine tools is still in the initial stage, and there is no uniform standard for fault early warning and diagnosis of machine tools. A standardized and comprehensive machine tool condition monitoring method based on energy fault tree analysis is proposed. The power, current and temperature inside the numerical control system and the signal of the external vibration sensor are collectively referred to as energy. A new energy fault tree is used to identify the location of the fault. At the same time, the client of computerized numerical control system internal information collection and analysis is developed. The characteristic frequency of each key component is analysed by theoretical mechanics, and an overall monitoring method is proposed to improve the monitoring efficiency. Finally, the reliability of the monitoring method is verified by experiments. The surface roughness of the parts is reduced by approximately 50%, which lays the foundation for the application of the engineering.

Acceleration smoothing algorithm for global motion in high-speed machining

When machining a series of short linear segments, the computer numerical control system interpolates the machining path with the pre-specified spline curve to obtain continuous feed motion. However, to obtain adequate smooth tool-paths to smooth the feed velocity and acceleration, the computer-aided manufacturing system needs to use a higher order spline curve, which will be limited by some technical bottlenecks. In this article, a new real-time interpolation algorithm is proposed from the perspective of kinematics to achieve uninterrupted feed motion throughout the global tool-path. At the same time, the acceleration profile achieves G2 continuous to avoid unnecessary feed frustration and inertial impact, reaching the balance between time-optimal and motion performance. First, the jounce-limited acceleration curve is blended at the corner of the machining path, and the optimal cornering transition velocity is obtained by adding the velocity, acceleration and contour error constraints to the corner transition motion. Then, according to the linear segments with different lengths between the corners, combined with the feed motion around the corner, a look-ahead interpolation algorithm is proposed to calculate the maximum feed rate with the constraint of the linear segment length and kinematic boundary conditions. At last, for the linear segments whose corner contours overlap with each other after interpolation, the smooth transition between the two corners can be realized by mixing the feed motion of the next corner. Compared with non-uniform rational B-spline interpolation algorithm, the proposed algorithm reduces the total machining time by 14% and the computer numerical control system improves the computational efficiency by 11%. It proves that the proposed algorithm has better application value in the manufacturing of complex parts.