Stretch-Blow-Molded Container Base Quality Control
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Solution Overview
Problem
Existing methods for quality control of stretch blow molded plastic containers are inadequate as they either rely on complex and non-linear absorption measurements or are expensive due to the need for multiple point measurements of wall thickness, and fail to accurately capture inhomogeneities in the molding process.
Innovation Solution
The method employs directed lighting and electronic camera technology with image processing to measure characteristic material distributions on the container's bottom, determining key parameters like the size and position of unstretched areas, which are more meaningful for quality assessment, and uses these parameters to control the stretch blow molding process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If absorption measurements are used to determine material distribution, then mass or volume of material can be determined, but the measurement includes irrelevant features (turbidity) that falsify results and the method becomes extremely complex with spatially resolving sensors
Solution Approach 1:
The patent extracts only the relevant information (material distribution patterns) from the bottom of the container by using image processing to identify specific features such as the size and shape of the bottom area, rather than attempting to measure all optical properties. This selective extraction eliminates interference from irrelevant features like turbidity while keeping the measurement system simple.
Solution Approach 2:
The patent replaces complex spatially resolving absorption sensors with a simple camera system that captures images of the container bottom. Image processing algorithms then analyze these images to determine material distribution, substituting a mechanically simple optical system for a complex measurement device while maintaining or improving measurement capability.
2Manufacturing precision
If wall thickness measurement is performed at multiple points to assess container quality, then comprehensive quality information is obtained, but the cost becomes relatively expensive
Solution Approach 1:
The patent creates a visual copy (image) of the container bottom that preserves the distribution pattern of the blow molded material. By analyzing this optical copy through image processing, the system obtains comprehensive quality information about material distribution without requiring physical contact measurements at multiple points, thereby reducing cost while maintaining assessment accuracy.
Solution Approach 2:
The patent changes the measurement parameter from physical wall thickness (requiring multiple point measurements) to optical properties of the container bottom (capturable in a single image). This parameter change allows comprehensive quality assessment through a single measurement operation, reducing system cost and complexity.
3Reliability
If conventional quality control methods are used, then basic defects can be detected, but inhomogeneities in the molding process cannot be accurately captured
Solution Approach 1:
The patent applies local quality analysis by examining specific regions of the container bottom (such as the center area and transition zones) to detect local inhomogeneities in material distribution. The image processing identifies localized patterns that indicate molding process variations, providing accurate detection of inhomogeneities that conventional methods miss.
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 simpler, more effective quality control method that offers higher information content compared to conventional methods, allowing for real-time monitoring and regulation of the molding process, ensuring consistent product quality across production tools.
Implementation Method 1
The characteristic material distributions are made visible by detecting the wedge angle between the inner and outer wall using directed light
Implementation Method 2
These inhomogeneities can be highlighted with special lighting according to the invention and can be recorded with electronic camera technology in a spatially resolving manner, especially in visible light
Data Source
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AI summary
The invention provides a method for quality control of a stretch-blow-moulded plastic container by inspecting its base, which method is easy to execute and is not highly susceptible to faults. To this end, the invention proposes determining quality features such as the surface area of an unstretched and/or only slightly stretched region of the base of the plastic container.