Coordinate Measuring Machines

Coordinate Measuring Machine 

Coordinate measuring machines (CMM) gather the surface x, y, z coordinates of an object to precisely measure its size and position for testing, dimensional and profile measurement, angularity or orientation, depth mapping, digitizing or imaging, assessment, and reverse engineering. It does this by analyzing the x, y, z coordinates via regression algorithms to construct features. At Century Metal Spinning uses it as an inspection device that allows for the measurement of any part quickly, efficiently, and accurately.

The CMM was first developed in the 1950s in Scotland for use with measuring military products. At that point, the machine measured only two axis. Today’s model, which measures three axis, first went into production in the 1960s. The three main components of the CMM are the machine body, the probe, and the control computer system that the data is sent to. The machine can be operated manually or by a CNC (computer numerical control).

The body of a CMM commonly has a fixed bed and is made up of a bridge like structure. One of the legs of the bridge remains mounted, while the other can move freely about the object being tested. Often, air bearings are used so the moving leg can travel freely and frictionless across the table. The three axis are measured by three different parts and movements of the machine. The bridge, previously described, contributes the information for one of the xy planes. The other xy plane’s data is collected by a carriage that moves between the legs of the bridge. The last set of information for the z axis comes from a vertical quill that is mounted on the carriage and can move up and down through its center.

In older versions of CMMs, the probe was controlled manually. The operator would physically hold the probe against the object being measured and a reading would be generated. The problem with this method was inconsistency of measurement. Each operator used different amounts of pressure and movement, which led to variations in measurements and accuracy. The first solution for this problem was the invention of a motorized probe. The operator no longer had to apply pressure, but could just move the probe with a joystick. The next innovation in CMM technology was the invention of the touch trigger probe, which is the system that Century Metal Spinning’s CMM uses. When the probe touches the surface of the object, it automatically bounces off and records the x, y, z coordinates data. This new system led to the creation of the modern CNC driven CMM machines.

CMM Controler

Some new CMM machines use a probe that drags along the surface of the object and records the data as it moves, creating a much more accurate reading. The newest, rapidly expanding CMM technology uses laser beams or white light to collect thousands of individual points quickly and accurately. Along with the standard x, y, z recording, the data can create a computerized 3D image of the object, which is often used for reverse engineering of a part.

Software for the CMM makes a huge difference in how the overall machine operates. We use the latest PCDMIS software on our machine. The type of software one should look for is one that is simple to operate, gets the job done, and uses the fewest keystrokes or clicks. After usability, the features and operating system with proper support are significant.

While all CMMs measure the same x, y, z information, their characteristics vary depending on what buyer is looking for. Each machine can handle different capacities, lengths, weights, speed, and detail.

To find out more about Century Metal Spinning's quality process. click here!

Spun Spheres in CMM