The content and attention points of the positioning accuracy detection of CNC punching machine

The content and attention points of the positioning accuracy detection of CNC punching machine
The detection of the positioning accuracy of the CNC punch is very important, because it shows the accuracy that the various moving parts of the punch can be achieved under the control of the CNC system. Therefore, the CNC lathe can judge the punch through the measured positioning accuracy value. The best workpiece machining accuracy that can be achieved in future automatic operations. It must be emphasized here that the current positioning accuracy inspection is based on rapid and positioning measurement. For some CNC punching machines with poor feed system stiffness, different positioning accuracy values ​​will be obtained when positioning with different feed speeds. In addition, the detection result of positioning accuracy is related to the ambient temperature and the operating state of the coordinate axis. Nowadays, most of the high-speed punch presses pass through a semi-closed loop system, and most of the position detection components are installed on the drive motor. Effective identification measures. Therefore, when measuring the positioning accuracy, it is not surprising that an error of 0.01 to 0.02 mm occurs within a 1m stroke after a few rapid reciprocating times. This is because after the lead screw moves quickly several times, the surface temperature may rise by 0.5 to 1°C, which causes the lead screw to generate thermal elongation. This kind of error caused by thermal elongation, some punches use pre-stretching (pre-tensioning) to reduce the impact.

The main detection contents of positioning accuracy are as follows:
1) Linear motion positioning accuracy (including X, Y, Z, U, V, W axis).
2) Repeated positioning accuracy of linear motion.
3) The linear motion is the same as the return accuracy of the mechanical origin.
4) Measurement of loss of momentum in linear motion.
5) Rotary motion positioning accuracy (turntable A, B, C axis).
6) Repeated positioning accuracy of rotary motion.
7) The return accuracy of the origin of the rotary axis.
8) Measurement of loss of momentum in rotary motion.
Commonly used inspection tools for measuring linear motion include: CNC punch micrometer and block gauge, standard length reticle ruler, optical reading microscope and dual-frequency laser interferometer, etc. Standard length measurement is based on dual-frequency laser interferometer. The rotating motion detection tools of CNC lathes include: 360-tooth accurate indexing standard turntable or angle polyhedron, high-precision circular grating and parallel light tube, etc.
The repeated positioning accuracy of each coordinate axis is the most basic accuracy index reflecting the axis. It reflects the stability of the axis’s movement accuracy. Punches with poor accuracy usually cannot guarantee the stability of production. Nowadays, due to the increasing number of CNC system functions, the machining center can systematically compensate the system error of each coordinate movement accuracy, such as the accumulated pitch error and the backlash error. Only the random error cannot be compensated, and the repeat positioning accuracy is exactly Reflecting the comprehensive random error of the feed drive mechanism, it cannot be corrected by numerical control system compensation. When it is found to be out of tolerance, only the feed drive chain can be fine-tuned and corrected. Therefore, when choosing a punch press, priority should be given to a punch with high repeat positioning accuracy.

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