New Calibration Service on Sphericity of Sphere to Support CMM and AACMM Verification

The Standards and Calibration Laboratory (SCL) has recently launched a new calibration service for assessing the sphericity of reference spheres. This service provides SI-traceable reference values essential for verifying coordinate measuring machines (CMM) and articulated arm coordinate measuring machines (AACMM).

Aligned with the ISO 10360 series recommendations, sphericity is determined using three orthogonal roundness measurements. By applying an error separation technique, SCL achieves expanded measurement uncertainties as low as 30 to 60 nm for each roundness value.

(Left) Set-up for Sphere’s sphericity measurement (Right) A customized designed fixture for three orthogonal roundness measurement

To support this, SCL developed an innovative method for capturing the three orthogonal roundness profiles. A custom-designed fixture allows measurements to be performed without repositioning the sphere, significantly reducing alignment time and ensuring the orthogonality of the three measured great circles. This design concept was published in the paper “An Effective Approach in Measuring Sphericity by Three Orthogonal Roundness” and presented at a technical conference in September 2025.