Flat Calibration Standard with Periodic Structures for CMM Geometry
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Solution Overview
Problem
Current methods for calibrating coordinate measuring machines require extensive time and multiple measurements on calibration spheres, risking damage to probing elements and involving complex, expensive procedures to achieve accurate geometry and surface roughness measurements, especially in integrated production sequences.
Innovation Solution
A calibration standard with a structured flat surface featuring modulated periodicity in one or two directions, allowing sensors to capture position and direction information through frequency or amplitude modulation, reducing the need for multiple measurements and calibration standards, and enabling accurate alignment and dynamic behavior assessment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional calibration methods using measurement calibration spheres are employed, then measurement accuracy can be achieved, but calibration time increases significantly and probing elements are at risk of damage
Solution Approach 1:
The patent changes the fundamental parameter of the calibration object from a spherical geometry requiring multiple probing contacts to a planar surface with coded periodic structures. This parameter change allows the measurement system to determine position and orientation from a single measurement pass by decoding the spatial frequency information embedded in the periodic pattern, thereby reducing calibration time while maintaining accuracy
Solution Approach 2:
The patent uses optical copying principles where the periodic structure on the calibration standard creates a measurable optical or tactile pattern that encodes position and orientation information. Instead of physically contacting multiple points on a sphere, the system captures an optical image or tactile scan of the periodic pattern and decodes the spatial information mathematically, eliminating the need for extensive physical probing
2Measurement precision
If multiple calibration standards with different roughness depths are used to ascertain linearity, then measurement linearity can be verified, but the measurement sequence becomes complex and expensive
Solution Approach 1:
The patent makes a single calibration standard perform multiple functions by incorporating periodic structures with different spatial frequencies in different directions on the same planar surface. This multi-functional design allows the system to verify linearity, accuracy, and dynamic behavior using one standardized object rather than requiring multiple specialized calibration standards, thereby simplifying the measurement sequence and reducing complexity
Solution Approach 2:
The patent transitions from using multiple one-dimensional calibration standards (different roughness depths) to a two-dimensional planar calibration standard with periodic patterns in both X and Y directions. This dimensional expansion allows simultaneous verification of linearity and accuracy in multiple directions from a single standard, reducing the number of required standards and simplifying the overall calibration process
3Measurement precision
If frequent calibration is performed in integrated production sequences, then measurement accuracy can be maintained, but the time expenditure becomes prohibitive
Solution Approach 1:
The patent prepares the calibration standard with pre-encoded periodic structures that contain all necessary calibration information in a compact format. This preliminary encoding allows the measurement system to rapidly extract calibration data from a single scan without requiring time-consuming multiple measurement sequences, enabling frequent calibration within production sequences without compromising productivity
Solution Approach 2:
The patent replaces traditional mechanical calibration methods involving multiple physical probing contacts and complex measurement sequences with an optical/tactile scanning method that captures calibration information from periodic surface patterns. This substitution dramatically reduces the time required for calibration while maintaining accuracy, allowing calibration to be integrated efficiently into production sequences
Data Source
AI summary
A calibration standard for geometry measurement calibration of a measurement system operating by tactile and/or optical means is provided which includes a flat surface having a structure that is capturable by a measurement system operating by optical and/or tactile means. The structure has a changeable periodicity that is capturable by a sensor in a first direction and/or in a second direction and for a change in the periodicity to code position information and/or direction information. In addition, a method for calibrating a coordinate measuring machine operating by tactile and/or optical means and to a coordinate measuring machine for such a method or having such a calibration standard is provided.