Zone-by-zone inspection of plastic preforms for recyclate quality control
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Solution Overview
Problem
The use of recyclate in plastic preforms often results in inhomogeneous quality, leading to increased rejection rates due to dark inclusions that heat unevenly and cause container bursts during the blow molding process, as existing inspection methods do not account for the specific sections and properties of the preforms effectively.
Innovation Solution
A method and device that inspect plastic preforms section-wise, assigning characteristic values to different areas and considering the properties of the container to be produced, such as geometric shape and wall thickness, to differentiate the severity of contaminants and make informed sorting decisions, thereby reducing unnecessary rejections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If uniform inspection of plastic preforms is performed, then inspection simplicity is maintained, but rejection rate increases due to inability to distinguish critical from non-critical defects
Solution Approach 1:
The plastic preform is divided into multiple inspection zones (first inspection zone and second inspection zone) with different inspection criteria. The first zone includes areas critical for container formation (mouth, shoulder, base) while the second zone includes less critical areas (body, bottom). This segmentation allows differentiated rejection criteria that reduce unnecessary rejections while maintaining inspection effectiveness.
Solution Approach 2:
Different inspection criteria and tolerance levels are applied to different local zones of the preform based on their functional importance. Critical zones require stricter inspection while non-critical zones allow higher defect tolerance, optimizing the balance between quality control and productivity.
2Productivity
If zone-by-zone inspection with differentiated criteria is implemented, then rejection rate decreases, but device complexity increases
Solution Approach 1:
The inspection system is segmented into multiple independent inspection zones that can be evaluated separately. Each zone has its own criteria but the overall system maintains a unified structure, making the complexity manageable through modular design.
Solution Approach 2:
The inspection system dynamically adjusts rejection decisions based on the location and severity of defects. The evaluation criteria are not fixed but adapt based on which zone the defect is located in, allowing the system to optimize rejection rates while managing complexity through rule-based decision logic.
3Device complexity
If all defects are treated equally regardless of location, then inspection process is simple, but container quality deteriorates due to untreated critical defects
Solution Approach 1:
The inspection process is segmented into different zones with different reliability requirements. Critical zones (first inspection zone) require stricter quality control to ensure container integrity, while non-critical zones (second inspection zone) have relaxed requirements, thus maintaining simplicity while improving overall reliability.
Solution Approach 2:
Different quality standards are applied locally to different zones of the preform. The mouth, shoulder, and base areas receive stricter inspection to ensure proper container formation, while body and bottom areas have higher tolerance, optimizing both simplicity and container quality.
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 reduces the number of incorrectly blown containers and lowers rejection rates by accurately assessing and managing contaminant risks based on their location and the container's design, optimizing the use of recyclate materials.
Implementation Method 1
the material may contain darker inclusions, which are heated more intensely in a heating device such as an infrared oven
Implementation Method 2
these are first heated and then expanded into containers such as plastic bottles by applying a flowable medium, for example, compressed air
Data Source
AI summary
Method for evaluating plastic preforms (10), wherein these plastic preforms are intended to be heated by a heating device and subsequently expanded into plastic containers by a forming device through the application of a flowable medium, wherein the plastic preforms (10) extend in a longitudinal direction and have several sections (10a, 10b, 10c) in this longitudinal direction, wherein these several sections have at least a threaded section (10a), a base section (10b) and a bottom section (10c), wherein at least the base section (10b) and the bottom section (10c) are inspected, characterized in that characteristic values for a material quality of the plastic preforms (10) are output, wherein these values are assigned to different sections (10a, 10b,10c) are assigned and/or where at least one property of the container to be manufactured is taken into account when evaluating these characteristic values.