Positional Accuracy of CNC Metal Spinning Machine
Date: Sep,08 2021 View:
Positional Accuracy of CNC Metal Spinning Machine
The positional accuracy of a CNC machine refers to the position accuracy that the measured machine moving parts can achieve under the control of the CNC system. It is an important accuracy different from ordinary machines. Accuracy has an important influence, especially the hole pitch error in pore processing has a decisive influence. A CNC machine can judge its machining accuracy from its achievable positional accuracy, so detecting and compensating the positional accuracy of the CNC machine is a necessary way to ensure the machining quality.
(1) Determination of positional accuracy
Currently, dual-frequency laser interferometers are mostly used to detect, process and analyze machines, use the principle of laser interferometry, and use the laser's real-time wavelength as the measurement benchmark, so the test accuracy is improved and the scope of application is enhanced. The detection method is as follows:
l Install dual-frequency laser interferometer;
l Install an optical measuring device in the coordinate axis direction of the machine to be measured;
l Adjust the laser head so that the measuring axis is collinear or parallel to the moving axis of the machine, that is, the optical path is pre-aligned;
l Enter the measurement parameters after the laser is warmed up;
l Move the machine for measurement according to the prescribed measurement program;
l Data processing and result output.
(2) Compensation of positional accuracy
If the measured positioning error of the CNC machine exceeds the allowable error range, the machine must be compensated for the error. The common method is to calculate the pitch error compensation table and manually enter the CNC system of the machine to eliminate the positioning error. Since the three-axis or four-axis compensation points of the CNC machine may have hundreds or thousands of points, manual compensation takes more time and easily went wrong.
Now connect the computer and the CNC controller of the machine through the RS232 interface, and use the automatic calibration software written in VB to control the synchronization of the laser interferometer and the CNC machine to realize the automatic detection of the positional accuracy of the CNC machine and the automatic pitch error compensation. The compensation method is as follows :
l Back up the existing compensation parameters in the CNC control system;
l The machine CNC program for point-by-point positional accuracy measurement is generated by the computer and transmitted to the CNC system;
l Automatically measure the positioning error of each point;
l A set of new compensation parameters are generated according to the specified compensation point and sent to the CNC system, and the automatic pitch compensation is completed;
l Repeat accuracy verification.
According to the accuracy of each axis of the CNC machine, the automatic pitch error compensation function and the backlash compensation function are used to reasonably select and allocate the compensation points of each axis, so that the CNC machine achieves the best accuracy state, and greatly improves the efficiency of detecting the positional accuracy of the machine.
Positional accuracy is an important indicator of CNC machines. Although users can choose high-precision machines with small errors as much as possible when purchasing, the longer the equipment is put into use, the more the equipment wears, and the positioning error of the machine becomes larger and larger, which is fatal to the processed and produced parts. Using the above methods to accurately measure and compensate the reverse deviation and positional accuracy of each coordinate axis of the machine can well reduce or eliminate the adverse effect of reverse deviation on the accuracy of the machine, improve the positional accuracy of the machine, and make the machine at its best Accuracy status, so as to ensure the processing quality of parts.
