The tolerance of surface profile is 0.5U0, that is, the total tolerance is 0.5, and the single side is 0.5 inward. How to define this inward direction of 0.5?

Surface contour refers to the state that the surface of any shape on the part maintains its ideal shape. Surface profile tolerance refers to the allowable deviation of the actual profile of a non-circular surface from the ideal profile surface. That is, it is given on the pattern to limit the variation range of the actual surface machining error.

Extended data:

The traditional measurement methods of surface profile measurement error include copying device measurement, cross-section profile template measurement, optical tracking profile measuring instrument measurement and coordinate measuring instrument measurement.

The first three measurement methods all need theoretical contour template before measurement. Because it is very difficult to make a theoretical profile template, this measurement method is suitable for the detection of a part in mass production.

When using the three-coordinate measuring device to measure, only the CAD mathematical model of the part (three-dimensional design graphics of the part) is needed, so the measuring method is suitable for any occasion and the measured data is reliable.

At present, there are many kinds of measuring equipment and methods for collecting three-dimensional coordinates of the surface of an object, and their principles are also different. According to whether the measuring probe is in contact with the surface of the part, it can be divided into contact type and non-contact type.

Contact measurement is usually represented by three-coordinate measurement. Coordinate measuring machine has high measurement accuracy and high requirements for environment (such as temperature, humidity, vibration prevention, etc.). ). Because the probe has to measure point by point on the workpiece during measurement, the measurement speed is slow. In addition, it is also required that the material of the tested parts should not be too soft, the size should not be too large and it is not easy to deform.

The typical representative of non-contact measurement method is structured light method. This measurement method can obtain a large number of data (point coordinates) on the surface of an object at one time, with a large measurement range and no requirement on the material of the object to be measured, and is especially suitable for the measurement of large-area and easily deformed covering parts.

Baidu Encyclopedia-Introduction to Surface