What Makes A Good CMM Calibration Artefact?

Posted by Tony Tillett on Jul 18, 2017 12:13:00 PM

What Makes A Good CMM Calibration Artefact.jpg

Making sure that your CMM machine is well calibrated is an important part of keeping your measurement data accurate. There are a number of artefacts that you can use to test the calibration of your CMM machine, and they all do something different.

The kinds of measurements that you perform in your lab are going to determine the optimum artefact for your Monday morning calibration check, and if you want to perform more advanced calibration you may need to invest in more than one artefact. At Status Metrology we have more than 30 years of experience when it comes to CMM based inspections, so let us help you choose a good CMM calibration artefact for your needs. 

Material 

There are a few materials that calibration artefacts are made from. Depending on the kind of probe you are calibrating, the correct type of material will change. The contact force from the measuring probe will create a certain amount of deformation in the artefact, so the stiffness of the material is important to consider vis-a-vis the probe being calibrated.

The contact from a measuring probe will create a Hertzian elastic deformation of both the probe and the artefact, and this must be accounted for when the data is interpreted. If a very stiff material like ceramic or tungsten carbide is used to fabricate the calibration artefact, and an object is later measured that is of a more normal hardness, the errors can be significant. This represents a consideration when choosing the material for your calibration artefact. 

Mounting System 

How you attach the calibration artefact to the CMM machine will be determined by the kind of probe you are using, and the type of calibration to be performed. Some artefacts are made to be mounted directly to the CMM machine itself, while others need to be held in place with a mounting bracket. Bear in mind that in many cases the artefact will react to the body heat that is transferred from the technician’s hand, and once installed on the CMM machine must be given time to disperse the heat.

Form

There are a number of different forms that a CMM calibration artefact can take on, and the probe that you are calibrating your machine with will determine the correct artefact. We can help you to design a calibration process for your business, and source artefacts that will make sure that your in-house calibration is done with the correct tools. Because the range of uses for CMM measuring machines is so broad, there are no general rules for CMM calibration artefact forms.

Lab Conditions

Depending on how fine of a measurement you are making with your CMM machine, the temperature in your lab can make a big difference. Every material will react differently to changes in temperature, and in addition to the temperature, air currents have to be kept in check. If you attempt to calibrate your CMM machine under conditions that aren't strictly controlled, the quality of the artefact and your methodology won't matter much.

Status Metrology

If you want to get the correct CMM machine calibration artefact for your metrology needs, Status Metrology is here to help. We are happy to consult with your metrology department about your CMM machine calibration, and can offer your company training in almost any aspect of CMM machine maintenance. We can also help you analyse your quality control process, to streamline the methodology that is used.

We have a highly experienced team and our lab maintains ISO and UKAS certifications. If you have any questions about what we can do for your company, give us a call on 0115 939 2228, or have a look at our website. More information can be found in our free CMM Maintenance Guide. Click here to download your free copy.

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Topics: CMM Maintenance & Calibration, Tips & Tricks

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