Coordinate measuring machines (CMMs) are widely used in industries such as machinery, electronics, instrumentation, and plastics. CMMs are an effective method for measuring and obtaining dimensional data because they can replace multiple surface measurement tools and expensive combination gauges, reducing the time required for complex measurement tasks from hours to minutes—an achievement unattainable with other instruments.
Factors Affecting Coordinate Measuring Machines: Factors Affecting Coaxiality in CMM Measurements. In the national standard, the coaxiality tolerance zone for CMMs is defined as the area within a cylindrical surface with a diameter tolerance of t and coaxial with the CMM’s datum axis. It has three control elements: 1) axis-to-axis; 2) axis-to-common axis; and 3) center-to-center. Factors Affecting Coaxiality in 2.5-Dimensional Measurements: The primary factors affecting coaxiality in 2.5-dimensional measurements are the center position and axis direction of the measured element and the datum element, particularly the axis direction. For example, when measuring two cross-section circles on a datum cylinder, the connecting line is used as the datum axis.
Two cross-sectional circles are also measured on the measured cylinder, a straight line is constructed, and then the coaxiality is calculated. Assuming that the distance between the two load surfaces on the datum is 10 mm, and the distance between the datum load surface and the cross section of the measured cylinder is 100 mm, if the center position of the second cross-sectional circle of the datum has a measurement error of 5um with the center of the cross-sectional circle, then the datum axis is already 50um away when it is extended to the cross section of the measured cylinder (5umx100:10). At this time, even if the measured cylinder is coaxial with the datum, the results of the two-dimensional and 2.5-dimensional measurements will still have an error of 100um (the same degree tolerance value is the diameter, and 50um is the radius).
Post time: Sep-02-2025