xiehe model

Position detection components are divided into direct measurement components and indirect measurement components according to detection methods. When the linear detection element is generally used to measure the linear motion of the machine tool, it is called direct measurement, and the closed-loop control of the position formed is called full-closed-loop control. The measurement accuracy of CNC machining metal parts mainly depends on the accuracy of the measuring element and is not affected by the transmission accuracy of the machine tool.

There is a precise proportional relationship between the linear displacement of the CNC machining table and the rotation angle of the drive motor. Therefore, the method of driving and detecting the rotation angle of the motor or lead screw can be used to indirectly measure the moving distance of the worktable. This method is called indirect measurement. Position closed-loop control is called semi-closed-loop control.

The measurement accuracy of metal parts depends on the accuracy of the detection element and the machine feed drive chain.

The machining accuracy of closed-loop CNC machine tools largely depends on the accuracy of the position detection device. CNC machine tools have very strict requirements on position detection components, and their resolution is usually between 0.001mm and 0.01mm or lower.

Compared with numerical control devices, detection components have a higher probability of failure, and phenomena such as cable damage, component contamination, and collision deformation often occur. If it is suspected that the detection element is faulty, first check whether there is any cable disconnection, fouling, deformation, etc., and the quality of the detection element can also be judged by measuring the output. This requires skilled work on the principle of the detection element and the output signal.

Let me give an example to illustrate, what should I do if the detection device fails and the machine oscillates (during acceleration and deceleration)?

1. The pulse encoder is faulty. At this time check whether the terminal voltage of the feedback line on the speed unit drops to a certain point. If there is a drop, the pulse encoder is faulty and the encoder should be replaced.

2. The cross coupling of the pulse encoder may be damaged, causing the shaft speed to be out of sync with the detection speed. In this case, the coupling should be replaced.