Frequently Asked Questions

Calibration establishes the relationship between a machine's readings and a reference value with stated uncertainty. Verification checks whether the machine still meets a specification, usually ISO 10360-2 or ASME B89.4.1. Most shop-floor "CMM calibration" is verification.

Length measurement error, E0 and E150, at five calibrated lengths measured three times in seven positions: three chosen by the user, four space diagonals. That is 105 measurements, checked against the machine's stated MPE.

Bridge, gantry and cantilever machines are commonly verified in place. Downtime depends on machine size and scope of the visit; turnaround is confirmed at quotation, not estimated in advance.

ISO 1 sets 20 °C as the reference temperature. Steel expands roughly 11.5 µm per metre per °C, so gradient matters as much as the absolute reading. Precision artifacts need hours of thermal soak before testing.

As-found data is recorded before any adjustment. Reporting an out-of-tolerance result before correction preserves the basis for an impact assessment against parts accepted since the last passing calibration.

Certificates are issued under the performing laboratory's ISO/IEC 17025 accreditation. The item, range and uncertainty should be checked against that laboratory's published scope in the accreditation body's public directory.

CMC is the smallest uncertainty a laboratory can claim within its scope. If the reported uncertainty is smaller than the scope CMC allows, that is a finding on audit, not an advantage.

AS9100 carries the same 7.1.5.2 traceability clause as ISO 9001, and measurement traceability is among the most cited findings in aerospace audits. Certificates state traceability, uncertainty and a decision rule to support that review.

The volumetric error compensation map corrects for the 21 kinematic errors across three axes. Whether it can be updated in the field depends on the controller; some OEM maps are locked and require the OEM's software.

Gauge blocks to ISO 3650, step gauges, ball bars, end bars or a laser interferometer supply calibrated test lengths. Probing error is checked on a separate calibrated sphere, not the probe qualification reference sphere.