What determines the precision of small CNC machining?

What determines the precision of small CNC machining?

       What determines the precision of small CNC machining? In the preparation of CNC machining programs, proper use of methods and techniques is of great significance to ensure and improve the machining accuracy of CNC machine tools. So what determines the precision of CNC machining? The machining accuracy of CNC machine tools is determined by the position detection element, which is composed of detection elements (sensors) and signal processing devices, and is an important part of the closed-loop servo system of CNC machine tools. Its function is to detect the actual value of the position and speed of the workbench, and send a feedback signal to the numerical control device or servo device, thus forming a closed-loop control. The detection element generally uses the principle of light or magnetism to complete the detection of position or speed.

      The position detection element is divided into direct measurement element and indirect measurement element according to the detection method. When directly moving the machine tool, a linear detection element is generally used, which is called direct measurement. The formed position closed-loop control is called full-closed-loop control. The measurement accuracy mainly depends on the accuracy of the measuring element pair and is not affected by the machine tool transmission accuracy. . Since the direct movement of the machine tool table has an accurate proportional relationship with the rotation angle of the drive motor, the method of driving the detection motor or the rotation angle pair of the lead screw can be used to indirectly measure the movement distance of the table. This method is called indirect measurement. The formed position closed-loop control is called semi-closed-loop control.

      The measurement accuracy of CNC machining depends on the accuracy of the detection element and the machine tool feed transmission chain. The machining accuracy of the closed-loop CNC machine tool is largely determined by the accuracy of the position detection device. The CNC machine tool has very strict requirements on the position detection element, and its resolution is usually between 00001-0.01mm or less. Compared with the numerical control device, the probability of failure of the detection component is still relatively high, and the phenomenon of cable damage, component contamination, and collision deformation often occurs. If it is suspected that the detection element is faulty, first check whether the cable is broken, stained, deformed, etc., and can also determine the quality of the detection element by measuring its output, which requires mastering the working principle of the detection element and the output signal. .