The working accuracy of the small machining center is an important index for checking the performance of the machine tool. Through the inspection and analysis of the processed parts, a comprehensive judgment can be made on each performance of the machine. If there is a problem through the inspection of the processed parts, it is very important to determine the shape of the processed parts at this time. Only by clearly determining the shape of the workpiece can the performance of the machine tool be analyzed. The following introduces and analyzes an abnormal phenomenon that occurs when the CNC machining center cuts a circle.
When using a laser interferometer to inspect a circle cut by a vertical CNC machining center, the shape shown in Figure 1 appears on the screen. The vertical CNC machining center performs circular cutting through interpolated interpolation between the X axis and the Y axis. From the movement speed, the process from Y1 to X1 is that the Y axis speed of the machine tool is getting faster and faster. When reaching the X1 point The fastest, while the X axis is getting slower and slower, the X1 point is the machine X axis reverse point. The process is the same from Y2 to X2. But there are two sharp points on the X1 and X2 points. First of all, from the graph, it can be sure that the X axis has a problem in the reverse direction. So how can the X-axis suddenly jump outwards and then quickly pull back when it is reversed? If this is the case, then there is only one possibility that the system has a problem. When the X-axis is reversed, the system gives an outward Beating instructions, but this assumption is impossible. Afterwards, the dial indicator was used for measurement, and the jump table did appear at X1 and X2. After careful and careful analysis, it was finally confirmed that the actual situation at X1 and X2 is shown in Figure 2. When the X axis reaches the X1 and X2 points, the X axis has not moved at all, while the Y axis has been interpolating. Compensation movement, when the Y axis runs the Ya distance, but the X axis suddenly runs the Xa segment distance, after obtaining this actual situation, the phenomenon of the machine tool can be analyzed.
As the X axis runs the Ya distance on the Y axis, the X axis motor also performs interpolation motion at the same time, and the X axis does not move. The root cause of this phenomenon is the inappropriate matching of the motor inertia of the machine tool and the moving inertia of the moving parts of the machine tool. Generally speaking, the inertia of the moving parts should not be greater than 3 times the inertia of the motor. If it exceeds 3 times, it will result in excessive positioning accuracy of the machine tool or excessive loss of the machine tool. Analyzing Figure 2, the sudden movement of the X axis Xa is because the X axis movement is the slowest at this time, and the interpolation compensation value for each movement is very small. Since the X axis loss is too large, then although the motor is moving, it moves The piece does not move. When the motor reaches a certain value, the X axis suddenly jumps, which causes the result in Figure 2. After calculation, this judgment is also proved correct.
Through this practice description, the instrument can detect the abnormal phenomenon of the machine tool, but the graphics displayed in the instrument must be carefully analyzed before the correct conclusion can be drawn.