Thermographic Weld Defect Detection in Plastic Containers
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Solution Overview
Problem
Existing methods for detecting weld defects in plastic containers are not sufficiently reliable and sensitive, as they fail to account for variables such as temperature changes due to cooling, leading to false positives and increased production costs.
Innovation Solution
A method involving thermographic image analysis that rescales images to enhance contrast, identifies the weld area, extracts descriptors, and corrects them for cooling time, ensuring validation intervals are adjusted for accurate defect detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If infrared thermography is used to monitor temperature in the sealing zone, then temperature can be obtained without contact, but the method cannot determine if the weld has been suitably made and does not detect defects in the sealing zone
Solution Approach 1:
The patent applies preliminary action by capturing the thermographic image at a specifically controlled time interval after weld completion, before the weld cools down completely. This timing ensures the temperature difference between defective and non-defective welds is still present and detectable, allowing reliable defect detection while maintaining non-contact temperature measurement
Solution Approach 2:
The patent changes the parameter of time by establishing a specific time interval between weld completion and image capture. This parameter control ensures the weld is still warm enough to show temperature differences indicative of defects, resolving the contradiction between non-contact measurement and reliable defect detection
2Ease of manufacture
If image correction with respect to a standard is applied, then the analysis is simplified, but the method becomes not very sensitive to flaws as it does not contemplate changes in boundary conditions
Solution Approach 1:
The patent applies preliminary action by pre-establishing the boundary conditions (time interval, temperature range) for valid welds. Instead of correcting images to a standard that masks variations, the method proactively captures images within controlled parameters that preserve the temperature differences indicative of defects, maintaining both simplicity and sensitivity
Solution Approach 2:
The patent applies local quality by focusing analysis specifically on the weld area and its temperature characteristics rather than applying uniform correction across the entire image. This localized approach preserves the temperature variations in the sealing zone that indicate defects, while still providing a simplified analysis framework
3Reliability
If strict conditions are applied for container rejection, then defect detection is performed, but false positives increase and production cost increases
Solution Approach 1:
The patent changes the parameter of time by establishing an optimal time interval between weld completion and image capture. This parameter optimization ensures defects are detected with high reliability while avoiding false positives, as the temperature differences are still present but the weld has cooled sufficiently for accurate measurement, thus maintaining production efficiency
Solution Approach 2:
The patent replaces complex mechanical inspection systems with infrared thermography combined with time-based parameter control. This substitution achieves reliable defect detection with simpler, faster measurement that does not require strict mechanical handling conditions, thereby maintaining high production efficiency while detecting defects reliably
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 provides a more reliable detection of weld defects by accounting for cooling time, reducing false positives and improving the sensitivity of defect detection in the sealing zone, thereby enhancing the quality control of plastic containers.
Implementation Method 1
ob 11 is a thermographic camera
Implementation Method 2
the value of which is corrected according to the time elapsed since heat sealing operation completion and which takes into account the cooling of the attachment
Data Source
Figure 1
Figure 2A~2B
Figure 2C~2D
AI summary
The present invention relates to a method for detecting defects in a weld obtained by heat-sealing between two polymeric materials and a system for detecting defects in a weld between said polymeric materials implementing this method. The method uses the thermography technique for taking images of the sealing zone of the container, for subsequently correcting said image, acceptable descriptors or thresholds according to parameters such as room temperature, welding temperature and time elapsed since the end of the sealing operation in order to reliably analyze the occurrence of defects in the sealing zone.