Precision metal parts processing can be divided into measurement and relative measurement according to whether the reading value of the gauge directly represents the value of the measured dimension.
Absolute measurement: the reading value directly indicates the size of the measured size, such as measuring with a vernier caliper.
Relative measurement: the reading represents the deviation between the measured size and the standard quantity. If the diameter of the shaft is measured with a comparator, the zero position of the instrument should be adjusted with a gauge block first. The measured value is the difference between the diameter of the side shaft and the size of the gauge block, that is, the measured value. Generally speaking, the measurement accuracy is higher and the measurement is more troublesome.
Precision hardware parts processing can be divided into contact measurement and non-contact measurement according to whether the measured surface is in contact with the measuring head of the measuring instrument.
Contact measurement: the measuring head is in contact with the contact surface, and there is a precise measuring force. For example, measure parts with micrometer.
Non contact measurement: the measuring head is not in contact with the surface of the measured part, and non-contact measurement can avoid the influence of measuring force on the measurement results. Such as projection method and light wave interference method.
Precision hardware parts processing can be divided into direct measurement and indirect measurement according to whether the measured parameters are measured directly or not.
Direct measurement: directly measure the measured parameters to obtain the measured dimension. For example, measure with caliper and comparator. Measurement: the measured geometric parameters are measured indirectly.
In conclusion, it is obvious that direct measurement is more intuitive and indirect measurement is more cumbersome. Generally, when the measured dimension or direct measurement cannot meet the accuracy requirements, indirect measurement has to be used.
