Marking Preform Walls via Laser Opacity Change
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Solution Overview
Problem
Current methods for marking plastic containers, such as labeling and engraving, are costly, prone to information loss during handling, and complicate recycling, while direct ink marking is expensive and may penetrate the container, and engraving weakens the wall.
Innovation Solution
A method that marks the preform before forming by changing the opacity of the thermoplastic material using a laser that emits a beam below the ablation threshold, creating visible carbon particles or inducing a photochemical reaction, ensuring the mark is stretched with the wall during forming without altering its thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If labeling is used to mark containers, then information can be displayed, but manufacturing cost increases and recycling becomes complicated
Solution Approach 1:
The invention extracts the marking function from the labeling process and integrates it directly into the container wall through injection molding. The marking ribs are formed as integral parts of the container during the molding process, eliminating the need for separate label manufacturing, application, and adhesive materials, thereby reducing manufacturing cost while maintaining information display capability
Solution Approach 2:
The marking function is merged with the container structure itself. The marking ribs are combined with the container wall during injection molding, creating a unified structure where the marking is an inherent part of the container rather than a separate component, simplifying both manufacturing and recycling
2Loss of information
If labels are glued onto containers, then information can be displayed, but the label may be torn off during handling
Solution Approach 1:
The marking ribs are merged with the container wall as integral structures formed during injection molding. This eliminates the interface between label and container that causes tearing, ensuring the marking remains permanently attached to the container throughout handling and use
Solution Approach 2:
The marking is created during the container manufacturing process itself, before the container enters service. The marking ribs are formed as part of the injection molding process, ensuring the information is already in place and cannot be lost during subsequent handling operations
3Ease of manufacture
If ink is used for direct marking, then labeling cost is reduced, but the ink may penetrate the container wall and migrate
Solution Approach 1:
Instead of using ink that penetrates and migrates, the invention creates a physical copy of the marking information in the form of surface relief ribs. These ribs replicate the visual information without using migrating substances, eliminating the harmful effect while maintaining the marking function
Solution Approach 2:
The chemical marking method (ink) is replaced with a mechanical marking method (injection molded ribs). The information is conveyed through physical surface features rather than chemical substances, eliminating migration while maintaining visibility and information display
4Ease of manufacture
If laser engraving is used to mark containers, then labeling cost is reduced, but the wall thickness is locally reduced weakening the container
Solution Approach 1:
The marking features are created during the injection molding process before the container is finalized. The marking ribs are formed as integral parts of the molded structure, allowing the wall material to be distributed uniformly without subsequent material removal that would weaken the container
Solution Approach 2:
The subtractive marking method (laser engraving that removes material) is replaced with an additive marking method (injection molding that forms ribs). This substitution eliminates material removal and the associated wall thinning, maintaining container strength while achieving the marking function
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 method allows for cost-effective, durable, and recyclable marked containers without weakening the wall, enabling efficient mass production with precise marking that remains visible and intact throughout the forming process.
Implementation Method 1
the mark is formed by carbon particles that are visible to the naked eye and that are produced by local heating of the material in the thickness of the wall using the laser
Implementation Method 2
the mark is obtained by a photochemical reaction between the thermoplastic material that constitutes the wall of the preform and the laser beam
Implementation Method 3
forming the container by injection of a fluid under pressure into the body of the preform so as to deform by stretching the heated portion of the wall
Data Source
AI summary
A method for producing a marked container (12), includes the following steps: a first step (E1) of heating, beyond a glass transition temperature, at least one shape-changing portion of the thermoplastic material wall (17) of a preform (14); and a second step (E2) of forming the container by injecting a pressurized fluid into the body (16) of the preform (14) such as to change the shape of the heated portion of the wall (17) by stretching it; and a step (E0) for marking the preform (14), during which a mark (39) is provided on the shape-changing portion of the wall (17) such that the mark (39) is stretched at the same time as the wall (17), during step (E2) after forming.