Polyolefin Undercut Features Demolding with High Hardness Adhesive
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Solution Overview
Problem
Molding of undercut features often results in deformation or breakage due to the difficulty in demolding without applying excessive force, as they impede withdrawal from the mold cavity, and existing methods require complex tooling or compromise on the integrity of the polymer.
Innovation Solution
A multilayer structure is created with a first layer of polyolefin having undercut features, a second layer of adhesive with a Shore D hardness greater than 59 for interlocking with the undercut features, and a third layer of substrate, where the adhesive layer is disposed between the first and third layers, allowing for demolding at a rate of at least 150 mm/min and maintaining the elastic nature of the polymer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional molding methods are used for undercut features, then the polymer can be molded, but demolding causes deformation or breakage due to inability to withdraw without excessive force
Solution Approach 1:
The invention divides the mold into multiple separable parts (mold halves with cavity portions) that can be independently moved. This segmentation allows the undercut feature to be released from one mold half while the other remains stationary, enabling demolding without deforming or breaking the feature.
Solution Approach 2:
The invention makes the mold structure dynamic by allowing one mold half to move relative to the other during the demolding process. The movable mold half transitions from a closed position (for molding) to an open position (for demolding), creating the necessary space to withdraw undercut features without damage.
2Ease of operation
If multiple mold parts are used to demold undercut features, then demolding is facilitated, but tooling complexity increases
Solution Approach 1:
The mold is segmented into two main halves with cavity portions, where each half contains some of the undercut features. This segmentation enables selective opening of the mold to access specific features without requiring complete disassembly of the entire mold assembly.
Solution Approach 2:
One mold half is made movable relative to the other, creating a dynamic demolding mechanism. This allows the mold to transition between closed and open states, facilitating easy removal of undercut features while maintaining a relatively simple overall mold structure compared to fully disassemblable molds.
3Ease of operation
If hook shapes are used for undercut features, then demolding is enabled through bending, but the hooks bend or break under lower force compared to other undercut feature shapes
Solution Approach 1:
The mold incorporates a movable half that dynamically opens to create demolding space, allowing undercut features to be withdrawn without bending or breaking. This dynamic approach eliminates the need for the feature itself to deform during demolding, preserving its structural integrity and force resistance.
Solution Approach 2:
By segmenting the mold into separable halves, the invention enables direct withdrawal of undercut features without requiring them to bend like hook shapes. The features maintain their original geometry and strength characteristics while still allowing easy demolding through the segmented mold structure.
Data Source
Figure 1A~3
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AI summary
Articles are provided, having a multilayer structure including (a) a first layer formed from polyolefin and including undercut features formed on and extending from an integral backing; (b) a second layer including an adhesive having a Shore D hardness of greater than 59 when cured; and (c) a third layer including a substrate. The second layer is interlocked with the undercut features, the third layer is adhered to the adhesive, and the second layer is disposed between the first layer and the third layer. A method is also provided including (a) depositing a polyolefin resin into a mold cavity to form a first layer including undercut features; (b) demolding the first layer from the mold cavity at a rate of at least 150 millimeters per minute; (c) applying a curable adhesive to the undercut features to form a second layer attached to the first layer; and (d) attaching a third layer including a substrate to the second layer.