The coordinate measuring machine (CMM) is a key part of any CNC machine shop. This device features an electronic probe that is used for measuring the geometry (height, width, and depth) of physical parts by sensing certain points on the surface of the object being measured. This helps one determine if the part in question meets the required specifications.

The primary advantage of this type of machine is that it can be used for measuring items that would otherwise be difficult to measure accurately with other types of measuring tools. A 3D CMM can measure using virtual lines and points, allowing for greater accuracy and more measurement options.

How the device works

The first step with a CMM is to allow the item being measured to adjust to the temperature of the room in which the machine will be used. Typically, you give it at least five hours to adjust to the temperature to prevent any measurement errors caused by thermal expansion.

You can then perform measurements by moving the probe to your desired location on the item manually, or with a computer controlling the probe. The CMM then logs the X, Y, and Z coordinates of that location. As you capture more points with the probe, the software in the machine calculates your chosen dimensions.

The various types of CMMs

There are several common types of CMMs:

  • Bridge CMMs: The bridge-type machine is the most common. It allows movement of the probe along the X, Y, and Z-axis, which are located orthogonally to each other. Every axis has its own sensor for monitoring the location of probes, and when the probes contact the object, the machine collects the data from the sensors and measures the location of the single point on the surface. This process is repeated until it generates an area that describes the surface to be measured with great accuracy.

  • Gantry CMMs: These machines are structured similarly to bridge CMMs, but are designed primarily for large, heavy parts. These machines are frequently floor-mounted for greater safety.

  • Cantilever CMMs: The cantilever machine is used primarily for measuring small parts and master parts due to high accuracy and low uncertainty of measurements. There is open access for the operator of the machine on three sides. The X-axis beam is attached to a side of a structure that houses the Y-axis, so the size of the X-beam is limited.

  • Horizontal arm CMMs: Horizontal arm CMMs feature a lower accuracy than the other types of machines listed above, but are still quite useful for measurements of large surfaces or particularly hard-to-reach features.

Our equipment

At Coastal Machine & Supply, our specific tool is the Keyence Wide Area CMM, which has a 32’ x 16’ measuring range. We make regular use of this tool for work in the aerospace industry.

This equipment provides highly accurate measurements, including easy 3D and GD&T measurements.

For more information about the CMM and its applications and benefits, contact us today.

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