What is the typical measurement accuracy (uncertainty) of your CMM systems?

CMM processes can be organized around ISO 10360 or another applicable standard, but the standard name does not guarantee a result for every printed surface or geometry. Probe, fixture, temperature, datum setup, and measurement uncertainty still control the result.

Provide the drawing revision, datum reference frame, critical features, material state, surface condition, temperature, and report format. Confirm the machine verification status and report uncertainty before using the result for acceptance.

CMM System Performance and Uncertainty Specifications

Our coordinate measuring machines deliver exceptional measurement accuracy with typical uncertainty values ranging from 1.8 ± L/300 μm to 3.5 ± L/250 μm, depending on the specific CMM class and measurement volume. This performance level ensures reliable dimensional verification for components manufactured across our entire additive manufacturing portfolio, including those produced through Powder Bed Fusion and post-processed using CNC Machining.

Factors Influencing Measurement Accuracy

Environmental Control and Thermal Stability

We maintain stringent environmental conditions in our metrology laboratory, with a temperature control of 20°C ± 0.5°C and a relative humidity maintained between 40% and 60%. This stability is crucial for maintaining measurement integrity, particularly for large components and materials with higher thermal expansion coefficients, such as Aluminum Alloys. All measurements are automatically compensated for material-specific thermal expansion characteristics.

Probe System Configuration and Calibration

Our CMM systems utilize various probing technologies, including touch-trigger, scanning, and optical probes, each with specific accuracy characteristics. High-density scanning probes achieve form measurement uncertainties of less than 0.5 micrometers for critical features. Regular calibration against ISO 10360-2 standards ensures ongoing accuracy verification, with particular attention to components that require tight tolerances, such as those used in Aerospace and Aviation applications.

Application-Specific Measurement Capabilities

Additive Manufacturing Component Verification

For AM components, we've developed specialized measurement strategies that account for unique surface characteristics. Complex Titanium Alloy medical implants are measured with uncertainties of less than 5 micrometers, while larger Stainless Steel industrial components maintain uncertainties within 15 micrometers across 500mm measurement volumes. The data obtained supports quality validation for components that have undergone various Surface Treatment processes.

Multi-Sensor Metrology Integration

Our advanced CMM systems incorporate vision and laser scanning capabilities for comprehensive measurement of features. This multi-sensor approach is particularly valuable for components with complex geometries produced via Directed Energy Deposition, where we combine tactile measurements for critical features with optical scanning for free-form surfaces. The integration provides complete dimensional characterization while maintaining measurement uncertainties within specified tolerances.

CMM uncertainty depends on the machine, probe, temperature, calibration, stylus configuration, part size, alignment, feature type, operator strategy, and environmental stability. A quoted machine specification is not the same as uncertainty for a particular measured feature. Form error, datum access, probing direction, surface finish, and fixturing can dominate the result on a complex AM part.

Provide the critical dimensions, datums, tolerance, material and temperature condition, feature accessibility, drawing revision, and required reporting rule. Ask for the measurement uncertainty or capability statement relevant to those features and identify how a result near the tolerance limit will be reviewed.

For a critical feature, request the measurement result together with the uncertainty or capability statement, probe configuration, temperature, alignment, and inspection date. If the tolerance is close to the measurement uncertainty, define a review rule before inspection. Do not use a generic machine accuracy value as a pass/fail boundary for every feature.

Also state whether the result is a single-point measurement, a form evaluation, a profile comparison, or a derived GD&T characteristic. The datum reference frame, filtering, outlier treatment, and number of points can change the result. Keep the inspection program and drawing revision with the report.

For production acceptance, link the uncertainty statement to the actual feature and measurement program, not only to the CMM model. If the result is close to a limit, use the agreed decision rule and retain the original points or scan comparison needed for review.

CMM uncertainty must be tied to the machine, probe, feature, fixturing, temperature, alignment, and measurement strategy. Request the applicable ISO 10360 verification, calibration date, probe qualification, material temperature, and feature-level uncertainty or method basis. A machine specification does not prove that every freeform surface, small hole, or difficult datum can be measured with the same uncertainty.

For a critical characteristic, also record the datum reference frame, measurement strategy, environmental condition, and customer decision rule. If a result is close to a limit, retain the original points and uncertainty statement so the quality team can review the decision without rerunning the entire inspection. A CMM machine specification should not be copied into the part report as though it were the measured uncertainty for every feature.