What are the factors that influence the precision of the coordinate measuring machine?

Author：Web　Source：Web　Date：2018-08-02 09:35:08　Sentiment：201

In addition to the measurement accuracy error caused by the failure of the tri-coordinate measuring machine itself, there are many factors that may affect the precision of the measuring machine and cause the measurement error. Operators should understand these factors to avoid affecting the accuracy of parts measurement.

1. Stable temperature in the machine room

As mentioned above, temperature is the biggest factor affecting the precision of measuring machine. The accuracy correction once a year cannot guarantee the accuracy of the measuring machine in the case of temperature change. Especially when the season changes, the temperature of the machine room is different from that of the calibration. It is necessary to use the temperature correction factor to correct the error caused by the difference of grating temperature and measuring block temperature under the condition of stable machine room temperature. This correction can be made according to seasonal or ambient temperature conditions.

2. Correct compensation documents

The compensation file is a compensation file which is generated after measuring the position, straightness and Angle error of the measuring machine with dual-frequency laser interferometer. Measurement software is based on it for error compensation. Some operators often forget to install the compensation file or lose the backup file when installing the measuring machine software, resulting in poor precision of the measuring machine and rechecking the machine precision. So the operator keeps the backup file and knows how to install the compensation file.

3. The purpose of accurate measurement head correction is to correct the diameter of ruby ball of the measuring rod (measuring tip), make measurement point measurement head correction, and obtain the position relation of different measuring heads. All the errors generated in the head correction will be added to the measurement. So in this link to ensure the correct and accurate.

Note the following points:

1) keep the standard ball and measuring rod clean.

2) ensure the fixed fastness of the measuring stand, measuring head, measuring rod and standard ball.

3) input correct rod length and standard ball diameter.

4) judge the accuracy of the correction according to the shape error and the diameter and repeatability of the corrected gemstone ball (the diameter of the corrected gemstone ball will be different if the length of the lengthened bar is different).

5) when different probe positions are to be used, the calibration accuracy shall be checked by measuring the coordinates of standard ball center points after all probe positions have been corrected. The test head file saved after the test head is verified can be used if the test head and the test rod are not moved. However, it is recommended to recalibrate the measuring head when the measurement accuracy is high.

4. Measure changes in mechanical parts

The working measuring machine of the measuring machine changes after a long period of use, especially when the environment is poor and the temperature fluctuation is large. At this point, the measurement machine overhaul and precision check.

5. The shape error of the measured parts and the correct benchmark

Because the principle of the tri-coordinate measuring machine is to pick the point first, then the software will simulate and calculate the error. Therefore, the measuring machine has certain requirements on the shape error of parts. The repeatability of the measurement is significantly reduced when the component under test has obvious burrs or trachoma, so that the operator cannot give an accurate measurement result. In this case, on the one hand, the shape error of the part under test is required to be controlled; on the other hand, the diameter of the gem ball under test bar can be increased appropriately, but the measurement error is obviously larger. It is one of the important parts to adopt the correct measurement method and select the correct measurement datum when measuring coordinate. For example, the projection plane or working plane should be selected when measuring the circle and line, the first and second benchmarks should be correctly selected when establishing the part coordinate system, and the reference axis should be selected when calculating the coaxial degree, etc. This needs to master the measuring principle of the measuring machine and take the correct method steps according to the actual situation.