CMM Error Map Validation via Articulating Probe
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Solution Overview
Problem
The process of validating error maps in Coordinate Measuring Machines (CMMs) using calibration artifacts like ball bars is time-consuming and costly due to the need for manual movement and multiple orientations.
Innovation Solution
A calibrated, articulating probe with two axes of rotation is used to contact a single-sphere artifact in various positions, calculating measured lengths and updating the error map by comparing them to nominal values, allowing the probe and stylus to move relative to the Z-ram while the artifact remains stationary, thereby simulating the ball bar measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If manual movement of calibration artifacts (ball bars) is used to validate error maps, then measurement validation can be performed, but the process becomes time-consuming and costly
Solution Approach 1:
The patent uses a calibrated probe with known stylus length to copy the measurement function of a ball bar artifact. Instead of physically moving a ball bar to validate squareness errors, the system uses the calibrated probe to measure the artifact and calculate equivalent ball bar measurements through coordinate transformations, thereby eliminating the need for manual artifact handling while maintaining validation accuracy
Solution Approach 2:
The patent replaces the mechanical ball bar measurement system with an automated probe-based measurement system. The calibrated probe, controlled by the CMM's automated positioning system, substitutes for the manual ball bar measurement process, enabling automated error map validation without physical manipulation of calibration artifacts
2Reliability
If multiple orientations of ball bar are measured to validate squareness error, then comprehensive validation is achieved, but the complexity and time required increase significantly
Solution Approach 1:
The patent makes the calibrated probe multi-functional by enabling it to perform both length measurement and squareness validation functions. Through coordinate transformations and mathematical calculations, the single calibrated probe replaces multiple specialized measurement procedures, allowing comprehensive error map validation including squareness errors to be achieved through one unified measurement process rather than multiple separate orientation measurements
Solution Approach 2:
The patent transforms the validation approach by changing from physical artifact orientation parameters to computational coordinate transformation parameters. Instead of physically rotating the ball bar to different orientations, the system maintains the artifact in one position and uses mathematical transformations of the calibrated probe measurements to evaluate squareness errors, thereby reducing procedural complexity while maintaining validation reliability
Data Source
AI summary
Validating the error map of a CMM using a calibrated probe including a stylus, the probe capable of rotation about at least one axis, includes placing a calibration artifact on a table of the CMM, the table having an upper surface in an XY plane; positioning a Z-ram of the CMM in a first calibration position and a second calibration position with respect to the artifact such that the stylus contacts the artifact; calculating a measured value representing the measured length between the first and second calibration positions; calculating a nominal value based on the length of the stylus of the probe; comparing the nominal value to the measured value; and updating the error map of the CMM if the measured value differs from the nominal value by more than a predetermined value. The probe and/or the stylus moves relative to the Z-ram such that the calibration artifact remains stationary while the Z-ram is positioned in the first calibration position and the second calibration position.