Computed Tomography Fixture Subtraction for Part Inspection
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Solution Overview
Problem
Existing computed tomography (CT) systems face challenges in reducing cycle times for inspecting objects, particularly in high-volume environments, due to the use of fixtures that can cause irregularities and slow down data processing, making accurate measurements difficult and time-consuming.
Innovation Solution
A method and system that involve acquiring images of a fixture and objects using CT, generating electronic models, subtracting the fixture model from the combined model to isolate the objects, comparing dimensions with CAD models, and outputting reports, which allows for rapid and automated inspection of multiple objects simultaneously by reducing the influence of fixture irregularities and enabling the use of more robust materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If foam fixtures are used to hold objects during CT scanning, then the objects can be supported and positioned, but the foam material causes irregularities in the part surface and slows down data processing
Solution Approach 1:
The patent extracts and removes the foam fixture from the final measurement model by performing image subtraction. The fixture is scanned first to create a reference model, then the fixture with parts is scanned, and the two models are subtracted to eliminate the fixture and leave only the parts for measurement, thereby removing the harmful effect of foam irregularities on surface accuracy and processing speed
Solution Approach 2:
The patent introduces a reference model of the fixture as an intermediary element. This reference model serves as a mediator that allows the system to mathematically remove the fixture's influence from the combined scan data, enabling the use of robust fixtures during scanning while maintaining measurement accuracy by subtracting the fixture's contribution in the digital domain
2Quantity of substance
If fixtures are used to hold multiple objects, then multiple objects can be inspected, but the cycle time for scanning remains several minutes which is unacceptable for high-volume environments
Solution Approach 1:
The patent merges multiple objects into a single fixture for simultaneous scanning, allowing batch inspection of multiple parts in one scan cycle. The image subtraction technique enables all parts to be processed together, reducing the cycle time per part while maintaining inspection quality
Solution Approach 2:
The patent performs preliminary scanning of the empty fixture to create a reference model before placing the parts. This preliminary action allows the system to prepare the subtraction template in advance, enabling rapid processing when the actual part inspection is performed, thereby reducing the cycle time for high-volume inspection
3Object-affected harmful factors
If foam fixtures are used to reduce absorption effects, then x-ray absorption is minimized, but the foam material creates surface irregularities that make accurate measurements impossible
Solution Approach 1:
The patent extracts the foam fixture from the measurement data through image subtraction. By creating a reference model of the fixture and subtracting it from the fixture-with-parts model, the system removes the foam's contribution to the data, eliminating surface irregularities and enabling accurate surface measurements of the parts
Solution Approach 2:
The patent creates a digital copy (reference model) of the foam fixture through preliminary scanning. This digital copy is then used to mathematically remove the physical fixture's influence from the measurement data, allowing the use of robust physical fixtures while maintaining measurement accuracy through digital subtraction of the foam's contribution
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 rapid and accurate inspection of multiple objects, reduces cycle times, and allows for the use of more robust materials beyond foam, improving efficiency and accuracy in high-volume environments.
Implementation Method 1
A CT system emits x-rays that pass into and through an object. The measurement of these x-rays allows the generation of 2D x-ray images of the object.
Data Source
AI summary
A system and method of inspecting a plurality of objects using a computed tomography (CT) system is provided. The method includes acquiring an image of a fixture used for holding the plurality of objects with the CT system. A first electronic model of the fixture is generated. The objects are placed in the fixture. An image of the fixture and the objects is acquired with the CT system. A second electronic model of the fixture and the objects is generated. A third electronic model of the objects is defined based at least in part on subtracting the first electronic model from the second electronic model. Dimensions of the objects from the third electronic model are compared with a computer aided design (CAD) model. A report is output based at least in part on the comparison of the objects from the third electronic model with the CAD model.