Use ruby needle correctly

Coordinate measuring instrument is a new type of precision measuring instrument with high efficiency. Widely used in manufacturing, electronics, automotive, aerospace and other industries. Check the size, shape and interposition of the parts.

The measuring principle of CMM is to place the measured object in the measuring space of CMM, obtain the coordinate position of each point of the measured object, and calculate the measured geometric size, shape and position according to the spatial coordinate value of these points. Measurement is a very important part of CMM, which is the switch of measuring device to detect the measured parts. Depending on the correct use of the measurement, the measurement of the gauge can be repeated.

Repeatability of needle measurement

Results can be obtained if the sampling direction of the probe is perpendicular to the probe body (perpendicular to the rod axis). As far as possible, the sample direction is perpendicular to the probe body. If the probe is sampled parallel to the probe along the load axis, the likelihood of repetition is lower than the likelihood of sampling perpendicular to the axis. If the sampling direction of the probe is not perpendicular or parallel to the body of the probe, the repeatability of the results is better than that of the body of the probe. The sampling direction of the probe is parallel to the rod axis, but should not be repeated from the Angle of the probe body, should be avoided as much as possible.

Avoid load conflicts

If the measuring rod is in contact with a non-contact part during the measurement process, the measuring system is considered to be sampling the contact point and a large error may occur. At this point, increasing the diameter of the measured ball will increase the space of the ball/column, thus reducing the likelihood of rod collisions. The effective working length is the depth that can be reached before the rod contact feature is measured. In general, the larger the ball, the greater the effective working length. The use of larger rod balls can also reduce the impact of detecting component surface roughness. However, the largest sphere available is limited by the smallest hole measured. In addition, the probe is a precision measuring instrument and should be kept clean and carefully maintained in size and shape. There should be no dirt in the ruby contact of the measuring rod. 1m dust will lead to 1m measurement error.

Verification of the measuring needle

When measuring with a contact probe, the coordinate data obtained due to the influence of the probe radius is not the coordinates of the surface that the probe touches, but the coordinates of the center of the heading. When the surface direction of the measurement point matches the direction of the measurement axis, the difference between the probe coordinates and the probe center is the probe radius value. If the probe radius is ignored and the measured data is not compensated, a data compensation error will occur. Therefore, the rod used must be verified and the actual contact point and software recording position along the direction of the measurement point vector must be compensated before the workpiece can be tested.

Therefore, when measuring, the probe is perpendicular to the measurement surface and moves along the normal direction of the measurement surface to minimize the compensation error of the spherical radius.

The following three errors should be eliminated through verification

(1) The error between the theoretical rod radius and the actual rod radius

(2) the error between the theoretical rod length and the actual rod length;

(3) Error of probe rotation Angle.

The above three errors are eliminated by verification, and the correct compensation value is obtained. Therefore, the accuracy of the verification results directly affects the inspection results of the workpiece.