A Guide To CMM Calibration Artifact

A CMM calibration artifact helps to ensure the precision and accuracy of the measurement data from a CMM. This assures reliable results and benchmarks such as safety, quality, and equipment lifespan.

All CMM calibration artifacts adhere to the ISO 10360 series when performing calibration. Using calibration artifacts allows users to independently check and ascertain the measuring accuracy of the CMM as well as to detect any inconsistencies and correct them accordingly. It thus minimizes uncertainties and errors to an acceptable level.

How to Determine Calibration

A CMM can have errors along 21 different measurement axes. This means that a wide variety of calibration artifacts can be used to correct these errors and to ensure the accuracy of calibration data, which contributes to the fixing of these errors and their integration into the data system.

CMMs have different levels of calibrations which could range from weekly checks to checks once or twice every year. To effectively determine calibration, the error and inconsistencies in measurement data first have to be sieved out to determine which measurement axes are faulty. The corresponding calibration artifact can then be used to calibrate the measurement for that particular measurement axes.

Artifact Types

There are different types of CMM calibration artifacts used during the calibration process. This is due to the different measurements that can be calibrated in a CMM. Some common artifact types include the swift-check gauge, ball plate, ball and cone, end bar, length gauge blocks, and the KOBA step gauge. When choosing an artifact, it is important to choose one that has a similar hardness to the artifact being measured to prevent any probe and material damage.

Certain artifact types will be better suited for certain CMM calibration. Most CMMs require a custom artifact. For example, the KOBA step gauge consists of a one-dimensional test body with planned parallel measuring surfaces. It is best used with small volume CMMs such as multisensory systems and monitors height gauges.

Calibration Process

There are different calibration processes involved which require different methods and calibration artifacts depending on what you wish to measure. The calibration process involves measuring the artifact along with a fixed measurement plan.

This allows for a comparison of the data points against the known dimensions of the artifact and easier cross-checking in the event of any anomalies or inconsistencies in the data set. The result would be a calibration of the CMM that would remove all errors and allow the CMM to perform its function of accurate measurement.

Laser Interferometer

A laser interferometer is only used when a high level of calibration is required. It is also a calibration artifact and utilizes a laser with a beam splitter to make extremely precise measurements using the reflected laser light.

The interference pattern created by the reflected laser light is tracked and so are the CMM’s movements via computer software. Any anomalies or inconsistencies in the data set are likewise corrected. The laser interferometer requires a longer calibration time than other artifacts and should only be handled by an experienced technician.

by George Chitos