HOW DO CMM PROBES WORK?

How do CMM probes work? Whether you are new to the industry or just having a brush up on knowledge, please use our "Guide to CMM" to help you on everything CMM related.

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How do CMM probes work: Here’s our guide to how do cmm probes work. The probe is the part of the measuring machine that takes the required detail from the object or part. It is mounted on to the CMM and operated either manually or by automated, programmed software on the computer. Once in operation, the probe will move around the object to take detailed, rich data about the dimensions and form of the part.

Measurements are defined by a probe that is attached to the third, moving axis of the machine. Without the probe there would be no way to accurately take the measurements, without the use of a laser or similar. This part of the machine is the main element for producing the output data. However, without the mounting hardware and operating software, the probe would not be able to operate.

What is a stylus?

The tool used to measure, that is mounted to the probe on a CMM is called the stylus. The styli consists of a steel or ceramic shank with a synthetic ball mounted on top. They are available in various sizes to be compatible with the measurements and parts that they are required to coordinate with. The styli can also be designed and produced to specification.

Choosing the right stylus for your project is paramount to obtaining the most accurate results. The correct length, diameter, level of thermal stability and material is vital as an inappropriate measuring tip will not be able to take sufficient data or may even allow for error in the measuring process.

Does it matter which stylus I use?

Changing the stylus on a probe can have a remarkably large impact on the real accuracy of the data. Any variation like this is not acceptable in the tolerance of CMM accuracy so it is important to ensure that you are using the correct stylus. Calibration will only confirm the accuracy of the probe with that particular stylus attached and must be repeated if a change is made.

The elements that make up a reliable and useful stylus tip are the sphericity, or roundness, its thermal stability, the material used and the ability to bend.

Using a tip quality stylus ball that is ‘graded’ to a high level, grade 5 or 10, ensures that the roundness of the sphere has been calculated and checked to ensure its quality.

Using a stylus that is manufactured from an appropriate material, resistant to the temperature fluctuations that it will be operated under, is important for maintaining reliability and consistency. Carbon fibre is a common build material as it has a low coefficient of thermal expansion, meaning that it will not expand and contract easily in the heat.

The material is also important when considering the wear and tear that the stylus will have to sustain during use. If you are measuring hard metals, and the stylus tip will regularly come into brief contact with them to take measurements, the surface may eventually become scratched or damaged after sustained use. Switching to a hard material like zirconia would be a good choice in this instance.

Another factor to consider is the rigidity of the probe and stylus. Attaching a probe and stylus that is correctly manufactured to withstand bend and manipulation, either by the environment or by the material that it will come into contact with, will ensure accurate measuring results through the project.

The probe is the main interface between your measured object or part and the software that you will be using to collate and analyse data. Ensuring the appropriateness of this element is essential to the integrity of the data and accuracy of the measuring process.

Our experts will be able to determine the exact style, size and specification of probe and stylus that you require for the project. Now you know how do cmm probes work speak to the QCT team today to ensure that your set up is the most correct and efficient it can be for the work that you are asking the machine to do. A slight change could improve your results, reporting and ultimately save you money overall.