Back-Moulded Insert Edge Bending for Injection Molding
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Solution Overview
Problem
Existing back-injection molding methods require complex and costly post-processing to fold and fasten protruding inserts, as the edge play between the mold and insert can be too large or too small, leading to damage or fold formation in the visible area of the component.
Innovation Solution
The method involves inserting the insert with a protruding edge that encloses an angle greater than zero degrees with the mold or slide, allowing the mold core to bend the edge over during closure, eliminating the need for post-processing by ensuring the edge is flush within the cavity, and using elastic or plastic materials to allow the insert to protrude beyond the matrix.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the edge play is made larger to prevent compression of the insert, then the insert can be inserted more easily without damage, but the plastic overmoulds the insert in the fold area and prevents or damages the subsequent fold over
Solution Approach 1:
The insert edge is pre-positioned to protrude beyond the mold edge before injection, creating a predetermined geometry that enables self-folding during mold closure. This preliminary positioning eliminates the need for post-processing folding operations while avoiding plastic overmolding issues.
Solution Approach 2:
Instead of trying to prevent the insert from protruding or folding it after injection, the invention inverts the approach by designing the mold to intentionally allow protrusion and using the mold closure itself to perform the folding action, transforming a potential defect into a functional feature.
2Manufacturing precision
If the edge play is made tighter to prevent plastic escaping, then the fold over can be achieved, but the insert is compressed during insertion causing folds in the visible area
Solution Approach 1:
The mold design incorporates localized features at the edge region, specifically allowing the insert edge to protrude beyond the mold edge in a controlled manner. This local geometric modification enables the insert to be received without compression while still achieving proper fold-over during closure.
3Manufacturing precision
If post-processing is used to fold and fasten protruding inserts, then the component quality is improved, but the production time and cost increase significantly
Solution Approach 1:
The invention merges the insert insertion, molding, and insert folding operations into a single integrated injection molding process. The insert edge protrudes during injection and is automatically folded over during mold closure, combining multiple operations that would otherwise require separate post-processing steps.
Solution Approach 2:
The mold structure itself performs the folding function during closure, with the cavity geometry guiding the insert edge to fold over automatically. This self-service mechanism eliminates the need for external folding equipment or manual post-processing operations.
4Manufacturing precision
If film clamps are used to fix the insert in the tool, then the insert positioning is improved, but the device complexity and additional components increase
Solution Approach 1:
The invention extracts and eliminates the film clamp component entirely from the tooling system. Instead of using clamps to hold the insert, the design relies on the insert edge geometry and mold closure mechanics to achieve proper positioning and folding, simplifying the overall tool structure.
Data Source
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AI summary
The method involves inserting an insert portion (4) into a die (7) in a splashing behind or foaming behind manner, such that an edge (6) of the insert portion projects over the edge of the die or a die sided slide (1) or a frame. The tool is closed, such that a cavity is formed between the mold core (2) and the die. The cavity is filled with a molding material or a foam. The projecting edge of the mold core is bent in the direction of the die.