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How To Judge The Accuracy Of Measuring The Error Of The Lathe
Jul 30, 2018

1, location precision detection of linear motion

The positioning accuracy of linear motion is usually carried out under the condition of no load on lathe and workbench. According to the national standards and ISO standards, the inspection of NC lathes should be based on laser measurement. In the absence of laser interferometer, for the general user can also use a standard scale, coupled with optical reading microscope for comparative measurement. However, the accuracy of the measuring instrument must be 1~2 grade higher than the accuracy of the measurement.

In order to reflect all the errors in multiple positioning, the ISO standard stipulates that each positioning point calculates the average value and the scatter difference band of the scatter -3 scatter zone according to the measured data of five times.

2, precision detection of repetitive positioning in linear motion

The instruments used for testing are the same as those used to detect positioning accuracy. The general detection method is to measure at any three positions near the point and both ends of each coordinate stroke. Each position is located fast moving, repeating 7 times under the same condition, measuring the stop position value and finding the maximum reading difference. The positive and negative symbols are attached to 1/2 of the maximum difference of the three positions. As the repeatable positioning accuracy of the coordinate, it is the most basic index to reflect the stability of the axis motion accuracy.

3, the precision detection of the origin of the linear motion

The precision of origin return is essentially the repetitive positioning accuracy of a special point on the coordinate axis, so its detection method is exactly the same as the repetitive positioning accuracy.

4, reverse error detection of linear motion

The reverse error of the linear motion is also called the loss of momentum, which includes the reverse dead zone of the driving parts (such as servo motor, servo motor and stepping motor, etc.) on the feed transmission chain of the coordinate axis, and the comprehensive reflection of the error of the reverse clearance and elastic deformation of the mechanical movement transmission pairs. The larger the error, the lower the positioning accuracy and the repeatability of positioning accuracy.

The method of detecting the reverse error is to move a distance forward or backward in the direction of the measured coordinate axis and stop the position as a reference, and then give a certain moving instruction value in the same direction, make it move a distance, then move the same distance in the opposite direction, and measure the stop position and the reference position. Poor. In the three positions of the middle point near the stroke and the two ends, the average value of each position is calculated. The maximum value of the average value is the reverse error value.

5, the accuracy test of the original reversion of the rotary table

The measurement method is to restore the origin from seven arbitrary positions and determine the stop position. The maximum difference read out is used as the precision of the origin.

The precision of each coordinate axis is the most basic precision index of the axis, which reflects the stability of the axis motion precision, and it can not be conceived that the lathe with poor precision can be used in production steadily. At present, because of the more and more functions of the CNC system, the system error, such as the pitch accumulation error and the backlash error, can be compensated for each system, such as the pitch error and the backlash error. Only the random error can not be compensated, and the repeatable positioning accuracy is a reflection of the comprehensive random error of the feed drive mechanism, and it can not be used. The compensation of CNC system is corrected. When it is found to be out of order, the feed transmission chain must be precisely adjusted. Therefore, if the lathe is allowed to be chosen, the lathe with high repetition positioning accuracy should be selected.

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