Transparent Plastic Sheet Concealing Sprue Marks
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Solution Overview
Problem
Producing large-area, transparent sheet-like plastic parts with perfect optical quality is challenging due to the difficulty in avoiding sprue marks and the inefficiencies of existing injection-moulding processes, particularly for direct injection-moulding which results in visible sprue marks on optical surfaces.
Innovation Solution
A direct injection-moulding process is used to produce transparent sheet-like plastic parts with a sprue mark, which is then covered by a material of lower transparency, such as a plastics material or paint, to minimize visibility of the sprue mark, allowing for the use of direct injection-moulding while maintaining optical quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If direct injection-moulding is used to produce transparent sheet-like plastic parts, then material waste is reduced and production costs are lowered, but sprue marks become visible on the optical surface
Solution Approach 1:
The patent applies local quality by making the covering material's transparency property location-specific: the covering material has lower transparency specifically at the sprue mark location to conceal it, while the rest of the shaped part maintains its original transparency for optimal optical performance. This resolves the contradiction by locally modifying transparency only where needed to hide the sprue mark without affecting overall optical quality.
2Manufacturing precision
If film gate process is used to avoid sprue marks on optical surfaces, then optical quality is improved, but additional working steps and material loss are required
Solution Approach 1:
The patent merges the shaping process and sprue mark concealment into a single direct injection-moulding operation, eliminating the separate sprue extension removal step required in film gate processing. The covering material is integrated into the moulding process itself, combining multiple functions (shaping + concealment) into one step, thereby improving productivity while maintaining optical quality.
3Manufacturing precision
If film gate process is used to supply plastic laterally, then sprue marks are avoided on optical surfaces, but extensive material loss occurs
Solution Approach 1:
The patent extracts the sprue mark concealment function from the main shaping process and implements it through a separate covering material layer applied after direct injection-moulding. This allows the main process to use efficient direct injection (minimizing material waste) while the extracted concealment function handles the sprue mark visibility issue, resolving the contradiction between material efficiency and optical quality.
Data Source
AI summary
A transparent sheet-like shaped plastic part, in particular a plastic pane, on account of the use of a direct injection-molding process during production of the shaped plastic part (1), has at least one sprue mark (4) located on an optical surface (1.2) of the shaped plastic part (1). The sprue mark (4) is covered by a covering material (2) of lower transparency than the shaped plastic part (1).