The coordinate measuring system of the machine. There are two types of coordinate systems within measurement. The first is called the "machine coordinate system" and refers to the X, Y, and Z axes of the machine's movements. When viewed from the front of the machine, the X axis runs left to right, the Y axis runs front to back, and the Z axis runs up and down, vertically perpendicular to the other two.

The second coordinate system is called the “Workpiece Coordinate System”, where the three axes relate to the data and characteristics of the workpiece and are not forced to correspond to those of the machine.

Before the introduction of machine coordinate measuring software, parts were physically aligned parallel to the machine axes so that the machine and part coordinate systems were parallel to each other Dimensional Inspection. This process took a long time and was not very accurate. When the part was round or contoured, rather than square or rectangular, the task of measurement was nearly impossible.

In the coordinate system: What is alignment?

With the CMM software, the coordinate measuring machine measures the reference points of the workpiece (from the impression of the part), establishes the coordinate system of the part, and mathematically relates it to the system of machine coordinates. The process of relating the two coordinate systems is called alignment. As with a street map, this is done automatically by "rotating" the map so that it makes sense from the perspective we have at the time. When we do this we are locating ourselves in our own reference coordinate system.

What is a "Datum"?

A “datum” is a specific location within the part's coordinate system. The “datums” are used as guides for reference primaries, or are used as directions for how to get to specific places. In the coordinate system, letters (A, C, D, E, F, G, etc.) are used to name the “datums”. Usually a “datum” is an element of a workpiece such as a surface or a groove from which the workpiece is measured to determine the distance from one element to another.

What is translation?

Imagine that you need to know how far a specific element of a workpiece is from another element. For example, the distance to the centers of each of two holes, from a central hole. To do this, you must first measure the central hole, translate the origin to the center of this hole, and then measure each of the four surrounding holes. Moving the start point (origin) of the measurement from its current position to another location on the workpiece is called translation. The coordinate measuring machine performs this procedure mathematically when the user requests an alignment routine from the geometric measuring software.