Computer Tomography Geometry Determination Without CAD
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Solution Overview
Problem
Existing computer tomography methods face challenges in achieving high precision when measuring workpieces with low radiographic transparency, such as steel parts, due to artifacts and measurement errors caused by scattered radiation, and often require CAD models which are not available for all objects like fuel injectors.
Innovation Solution
A method that selects surface measurement points based on specifiable rules, using directional information of the specified geometry, without requiring a CAD model, by defining the geometry features with basic elements like lines, circles, and cylinders, and combining measurement points from multiple sensors for improved precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If computer tomography is used to measure steel parts with low radiographic transparency, then measurement capability is extended to difficult-to-measure materials, but measurement precision deteriorates due to artifacts and scattered radiation
Solution Approach 1:
The patent introduces an intermediary calibration object with known geometry that mediates between the measurement system and the workpiece. This calibration object enables the determination and correction of systematic measurement errors caused by scattered radiation and beam hardening effects, thereby maintaining high measurement precision when measuring steel parts with low radiographic transparency
Solution Approach 2:
The patent applies parameter changes by systematically varying measurement parameters (such as energy levels, rotation angles, and evaluation criteria) and selecting the optimal combination that minimizes artifacts and scattered radiation effects. This allows the measurement system to adapt to different material densities and maintain precision across various workpiece types
2Adaptability or versatility
If surface measurement points are selected without CAD model guidance, then measurement independence is achieved, but measurement precision deteriorates due to inclusion of irrelevant points
Solution Approach 1:
The patent uses a calibration object with known geometry as an intermediary reference that enables precise point selection without requiring a CAD model of the workpiece. The known geometry serves as a mediator to establish reliable measurement point selection criteria that maintain precision while achieving measurement independence
Solution Approach 2:
The patent replaces the traditional CAD model-based selection system with a data-driven approach that uses statistical evaluation and known geometric references to automatically identify and select relevant measurement points from the raw point cloud data, eliminating the need for workpiece-specific CAD models
3Quantity of substance
If all generated surface points are used for feature determination, then measurement completeness is maintained, but measurement precision deteriorates due to inclusion of points not associated with the feature
Solution Approach 1:
The patent extracts only the relevant measurement points from the complete set of surface points by using distance criteria and geometric evaluation. This extraction process separates points that are actually associated with the feature of interest from those that are not, maintaining measurement completeness for the feature while eliminating irrelevant data that would reduce precision
4Measurement precision
If master part measurement is used to define feature geometry, then measurement accuracy is improved, but measurement time increases
Solution Approach 1:
The patent performs preliminary measurements on a master part to establish reference geometry and measurement point selection criteria. These preliminary results are then reused for subsequent workpiece measurements, allowing the system to achieve high accuracy without repeating the time-consuming master part measurement process for each individual workpiece
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables high-precision geometry determination of workpieces like fuel injectors, even without a CAD model, by selecting relevant surface points and using multiple sensors to correct and enhance measurement accuracy, thereby improving series measurement efficiency.
Implementation Method 1
the workpiece to be measured is permeated by the measurement radiation, wherein an attenuation of the measurement radiation occurs as a function of the penetrated distance and penetrated material
Implementation Method 2
The radiation exiting behind the workpiece is captured by a radiation detector
Data Source
AI summary
A method for determining the geometry of a structure on an object at least by using a computer tomography sensor system comprising at least a radiation source, a mechanical axis of rotation, and a detector, preferably a planar detector, wherein surface measurement points are generated by the computer tomography sensor system, for example in the region of material transitions. In order to select the surface measurement points to be used for the determination of a geometry feature by using any target geometry, in particular without the availability of a CAD model being necessary, according to the invention, in order to determine the geometry features, surface measurement points are used which are associated with the geometry features to be determined on the basis of specifiable rules and the geometry features are determined from the associated surface measurement points.