On January 1, 1990, the State Bureau of Technical Supervision officially promulgated the evaluation standard for the position of numerically-controlled machine tools—GB10931—89 "Evaluation Method of Positional Accuracy of Digitally Controlled Machine Tools" (hereinafter referred to as "Evaluation Method"). The nouns, terms, calculation formulas and detection methods are clearly defined. However, there is no hard limit on the instruments used to measure the positional accuracy.
The current instruments for measuring positional accuracy include: laser interferometers, precision line scales and reading microscopes, reference step gauges, and lever dial gauges (or electronic micrometers). The method of measuring the precision step size with a dial gauge is only second to the laser interferometer, but the disadvantage is that it is expensive, and its step size is equivalent, and it is equivalent to the 5.4th of GB10931-89 "Assessment method". The money does not exactly match.
When the company accepted the imported CNC equipment, according to the characteristics of the step gauge, we made a gauge similar to the step gauge. We call it the standard step gauge, and its structure is shown in the figure. The pitch of the quasi-step gauge is set according to actual needs, but it must meet the requirements of GB10931-89. The top holes at both ends are not only needed for the process, but also for fixing the CNC lathe on the top between the headboard and the tailstock. Plane N is for ease of placement on a CNC machine tool table. In the process of making a quasi-pitch, a plurality of aging treatments should be performed, and it is preferable to perform a cold treatment to reduce its residual stress to a minimum to improve its dimensional stability. After being made, the distance from the adjacent side of the same side (accurate to 0.001mm) is measured with a high-resolution measuring instrument such as a tool microscope, and the measured value is engraved on the corresponding position of the quasi-step gauge. If conditions permit, it is best to use a coordinate measuring machine to measure the distance between adjacent side faces.
Using a quasi-step gauge to test the CNC lathe, test! When the position accuracy of the coordinates, the fixture is fixed between the headboard and the tailstock, the lever dial gauge is fixed on the tool holder, and the quasi-step gauge is adjacent. The distance between the end face is input to the numerical control system, and the program is ready for testing. "When testing the position accuracy of the coordinates, place the quasi-step ruler on its tool post with its plane parallel to the feed direction of the tool post. The lever table can be set up on the bed and the test can be started. The measuring tool is used to measure the machining center. When measuring X and Y coordinates, the quasi-step gauge is placed on the workbench with its plane, and the lever dial gauge is placed on the main shaft; when the coordinates are measured, the quasi-step gauge plane is fixed to the plane by means of a square ruler. On the workbench, the lever dial indicator is placed on the spindle, and the rest of the steps are the same as the test CNC lathes, which will not be described here.
Self-made quasi-step distance structure chart
The quasi-step gauge has a simple structure and good craftsmanship and is suitable for self-manufacture in a factory. For CNC lathes, machining centers, CNC milling machines and other numerical control equipment can be used for testing. The distance between the adjacent end face of the gage can be set according to the actual situation of the enterprise. At the same time, the distance between the adjacent end faces is measured and the value cannot be an integer. Paragraph 5.4 of the "Assessment Method" requires that the target position Pj = (J-1)t + r (where j is the target position number; t is the pitch of the target position, which is an integer but not equal to the lead of the drive screw The multiple of r, any decimal decimal). Therefore, the measuring surface spacing of the gage meets the requirements of the "Evaluation Method".
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