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Summary of commonly used flatness measurement methods

2021-09-15

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Flatness measurement method Flatness error refers to the variation of the actual surface to be measured relative to its ideal surface. The position of the ideal plane should meet the Z minimum condition, and the flatness error belongs to the shape error in the shape and position error. The common methods for measuring the flatness error are as follows: Liquid level method: The liquid level method uses the liquid level as the measurement datum. The liquid level is composed of the liquid level in the "connecting tank", and then the sensor is used to measure. This method is mainly used to measure the flatness error of large planes.

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Laser flatness measuring instrument: The laser flatness measuring instrument is used to measure the flatness error of large planes. Flat crystal intervention method: use the working surface of optical flat crystal to represent the ideal plane, and directly determine the flatness of the measured surface by the bending level of the interference fringe. difference. It is mainly used to measure small planes, such as the working surface of the gauge and the flatness error of the measuring surface of the micrometer probe.

Beam plane method: The beam plane method is to use the quasi-value telescope and the aiming target mirror to measure, and select the beam plane composed of three points far apart from Z on the actual surface as the measurement reference plane of the flatness error. Measuring method by meter: The method of measuring by meter is to place the part to be tested and the micrometer on the standard plate.

Take the standard flat plate as the measurement datum, and use the micrometer to measure point by point or along several straight lines along the actual surface. The measuring method is divided into three-point method and diagonal method according to the evaluation datum: the three-point method is to use the ideal plane determined by the three points far apart Z on the measured actual surface as the evaluation datum. The three points that are Z far apart on the actual surface are adjusted to the standard plate, etc.