What are the measurement methods of CNC precision machining accuracy?

Machining accuracy is the degree of conformity between the three geometric parameters of the actual size, shape and position of the surface of the processed parts and the ideal geometric parameters required by the drawings. The ideal geometric parameter is the average size for the size; for the surface geometry, it is absolute circle, cylinder, plane, cone and straight line; for the mutual position between the surfaces, it is absolute parallel , Vertical, coaxial, symmetrical, etc. The deviation between the actual geometric parameters of the part and the ideal geometric parameters is called machining error. Kaicheng Precision is based on the machine tool spindle, rotary thimble, screw and screw, shaft processing, CNC lathe processing, tool holder and arbor, quality assurance!

1. Processing accuracy According to different processing accuracy content and precision requirements, different measurement methods are adopted. Generally speaking, there are the following types of methods:

1. According to whether the measured parameter is measured directly, it can be divided into direct measurement and indirect measurement.

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Direct measurement: Direct measurement of measured parameters to obtain measured dimensions. For example, use calipers and comparators to measure. Indirect measurement: measure the geometric parameters related to the measured size, and obtain the measured size through calculation.

Obviously, direct measurement is more intuitive and indirect measurement is more cumbersome. Generally, when the measured size or direct measurement cannot meet the accuracy requirements, indirect measurement has to be adopted.

2. According to whether the reading value of the measuring instrument directly indicates the value of the measured size, it can be divided into measurement and relative measurement.

Absolute measurement: The reading value directly indicates the size of the measured size, such as a vernier caliper.

Relative measurement: The reading value only represents the deviation of the measured size relative to the standard quantity. If you use a comparator to measure the diameter of the shaft, you must first adjust the zero position of the instrument with a measuring block, and then measure it. The measured value is the difference between the diameter of the side shaft and the size of the measuring block. This is relative measurement. Generally speaking, the relative measurement accuracy is higher, but the measurement is more troublesome.

3. According to whether the measured surface is in contact with the measuring head of the measuring instrument, it is divided into contact measurement and non-contact measurement.

Contact measurement: The measuring head is in contact with the surface being contacted, and there is a precise measuring force. Such as measuring parts with a micrometer.

Non-contact measurement: the measuring head is not in contact with the surface of the measured part. Non-contact measurement can avoid the influence of the measuring force on the measurement result. Such as the use of projection method, light wave interferometry and so on.

4. According to the number of measurement parameters at one time, it is divided into single measurement and comprehensive measurement.

Single measurement; each parameter of the tested part is measured separately.

Comprehensive measurement: Measure the comprehensive index reflecting the relevant parameters of the parts. For example, when measuring the thread with a tool microscope, the actual diameter of the thread, the half-angle error of the tooth profile and the cumulative error of the pitch can be measured separately.