Precision inspection knowledge of precision CNC machining

1. For guide rails of different shapes, which planes should be controlled for the straightness error of each surface?

Answer: The common shapes of precision CNC machining center rails are rectangular rails and V-shaped rails. The horizontal surface of the rectangular guide rail controls the straightness error of the guide rail in the vertical plane. The two sides of the rectangular guide rail control the straightness error of the guide rail in the horizontal plane. For the V-shaped guide rail, because the guide rail is composed of two inclined surfaces, the two inclined surfaces not only control the straightness error in the vertical plane, but also control the straightness error in the horizontal plane.

2. What are the commonly used detection methods for guide rail straightness errors?

Answer: According to the introduction of precision CNC processing manufacturers, the commonly used detection methods for guide rail straightness errors include: point-grinding method, flat rule drawing table comparison method, padding method, drawing wire detection method and level detection method, optical straightness (autocollimator) ) Detection method, etc.

3. What is the research point method?

Answer: When using a flat ruler to detect the linearity error of the guide rail, apply a thin layer of red lead oil evenly on the surface of the inspected guide rail, cover the flat ruler on the surface of the inspected guide rail, and perform short-distance reciprocating movement with appropriate pressure. Grind the points, then remove the flat ruler, observe the distribution of the research points on the surface of the inspected guide rail and the density of the sparsest points. The research points are evenly distributed over the entire length of the guide rail, which means that the straightness error of the guide rail has reached the corresponding accuracy requirements of the flat ruler. This method is called research point method.

The flat ruler used in the research point method is a standard flat ruler, and its accuracy level is selected according to the accuracy requirements of the inspected guide rail, generally not lower than level 6. The length is not shorter than the length of the inspected guide rail (in the case of lower accuracy requirements, the length of the flat ruler can be 1/4 shorter than the guide rail).

4. Which types of guide rail straightness error detection is suitable for the research point method?

Answer: When precision CNC processing manufacturers use the scraping method to repair the straightness error of the guide rail, most of them use the dot method. The research point method is often used for the detection of shorter rails, because the flat ruler is easily deformed when it exceeds 2000mm, making it difficult to manufacture, and affecting the measurement accuracy. When scraping a short guide rail, the straightness error of the guide rail is usually guaranteed by the accuracy of the flat ruler. At the same time, there are also certain requirements for the density of the grinding points per unit area. According to the accuracy requirements of the CNC machining center and the guide rail in this CNC machining center The nature and importance of the position are stipulated as not less than 10-20 points per 25mm×25mm (that is, the number of points per square).

When using the point-grinding method to detect the linearity error of the guide rail, the precision CNC processing manufacturer stated that because it cannot measure the error value of the linearity of the guideway, when there is a level meter, the point-grinding method is generally not used for the final detection. However, it should be pointed out that in the absence of measuring instruments (levels, optical straighteners, etc.), the inspection ruler produced by the mutual research method of three rulers can more effectively meet the detection of the straightness error of the short guide rail of the general CNC machining center. Claim.

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