Thermoformed Container Rim Slitting via Coined Indentations
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Solution Overview
Problem
The existing methods for thermoforming open-topped plastic containers with slits in the rim are costly and complex, as they require specialized tooling and delicate punch and die sets, leading to issues with slug formation, tooling costs, and difficulty in inserting display inserts.
Innovation Solution
A process that forms elongated indentations in the rim during the thermoforming stage using coining, followed by slitting the thin bottom wall of these indentations with a trim die set, eliminating slug formation and reducing tooling costs, allowing for easy insertion of display inserts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a through slot is molded to the rim during the thermoforming process by a mold feature, then the slit is formed in the container rim, but tooling costs increase since a special tooling feature must be provided for each cavity
Solution Approach 1:
The coining features on the clamping rings pre-form elongated indentations in the rim material during the thermoforming stage, preparing the material structure before the trimming operation. This preliminary action reduces the complexity of the subsequent slitting operation and eliminates the need for complex mold features.
Solution Approach 2:
The clamping rings serve as an intermediary element that performs the coining function. By incorporating coining features on the clamping rings, the system combines clamping and pre-forming functions in a single component, avoiding the need for separate specialized tooling features in each cavity.
2Ease of manufacture
If punching slots into the rim after forming the containers is performed, then the slit is created in the rim, but tooling costs increase and slug formation occurs creating jams and disposal problems
Solution Approach 1:
The coining process pre-thins the rim material by forming elongated indentations before the slitting operation. This preliminary thinning allows the trim die to cut through the material cleanly without generating slugs, eliminating the harmful byproducts associated with traditional punching methods.
Solution Approach 2:
The coining process changes the physical parameters of the rim material by locally thinning it through plastic deformation. This parameter change (thickness reduction) in the indentation areas enables clean cutting without slug formation during the subsequent trimming operation.
3Ease of manufacture
If the thick rim material is cut using thin knife blades in the trimming operation, then the slit is formed, but the knife blades break easily requiring a punch and die set
Solution Approach 1:
The coining features create elongated indentations that pre-thin the rim material before trimming. This preliminary thinning action reduces the material thickness in the slit path from the original thick rim to a thinner section, allowing standard trim die blades to cut through reliably without breaking.
Solution Approach 2:
The coining process creates local quality changes in the rim material by forming indentations with reduced thickness only in the areas where slits are needed. This localized thinning maintains the structural integrity of the thick rim elsewhere while enabling easy cutting only where required.
4Ease of manufacture
If a high tonnage trim press is used to perform punching, then the slit is formed in the thick rim, but press tonnage requirements increase particularly when other steps are done simultaneously
Solution Approach 1:
The coining process performs preliminary material preparation by forming elongated indentations that thin the rim. This pre-thinning reduces the force required for the subsequent slitting operation, allowing standard tonnage trim presses to perform both coining and slitting simultaneously without requiring high tonnage equipment.
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 reduces tooling costs and simplifies the trimming process, enabling easy insertion of display inserts while minimizing press tonnage requirements and avoiding slug-related issues, resulting in a cost-effective and efficient production of thermoformed containers with slitted rims.
Implementation Method 1
A coining process executed during the forming stage forms one or more elongated indentations in the rim
Implementation Method 2
A trim die set is thereafter used to cut a slit through the thin bottom wall of each of the indentations during the trimming phase of the process
Data Source
AI summary
An open-topped container has an outwardly turned rim extending around the open top a thermoformed body of the containers with the rim formed by a clamping ring which has one or more projections each forming an indentation into the rim. Trim tooling subsequently forms a slit through the bottom wall of each indentation able to receive a flat plastic display inserted therein.