Thin Glass Ribbon Border Severing for Edge Quality
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Solution Overview
Problem
Existing methods for producing thin glass ribbons result in uneven cooling and stress-induced warpage due to thicker borders, leading to rough edges and increased risk of breakage during coiling or bending, and fail to produce high-quality edges with minimal secondary border formation.
Innovation Solution
A method involving the severing of borders from a thin glass ribbon at a specific viscosity range (10^7 to 10^11 dPa·s) using a laser to melt and separate the glass, creating fire-polished edges with reduced secondary border thickness, while maintaining a homogeneous temperature profile to minimize stress and warpage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional drawing methods are used to produce thin glass ribbon, then the glass ribbon can be manufactured, but borders with greater thickness form at the lateral edges causing uneven cooling and stress
Solution Approach 1:
The glass ribbon production process is segmented into distinct zones: a drawing zone where the glass ribbon is formed, and a severing zone where borders are removed. This segmentation allows the main body of the glass to be produced continuously while the problematic borders are separately addressed and removed, resolving the thickness uniformity issue without stopping production.
Solution Approach 2:
The border regions with excessive thickness are extracted and removed from the glass ribbon using a severing device. This extraction eliminates the source of uneven cooling and stress, allowing the remaining central portion of the glass ribbon to have uniform thickness and properties.
2Ease of manufacture
If borders are severed in the cold post-processing section on annealed molten glass, then the borders can be separated, but rough edges and microcracks are created leading to uncontrolled breakage
Solution Approach 1:
The border severing operation is performed preliminarily in the hot forming section while the glass is still at elevated temperature and has lower viscosity, before the glass enters the cold post-processing section. This preliminary action allows clean separation without creating microcracks, as the glass is more ductile and can be severed smoothly.
Solution Approach 2:
The severing operation exploits the temperature-dependent viscosity parameter of glass. By performing severing at elevated temperatures where viscosity is lower (10^7 to 10^11 dPa·s), the glass can be cleanly separated. The process then allows the glass to cool to the annealing point where viscosity increases, preventing further breakage.
3Device complexity
If the glass ribbon is cooled uniformly, then the manufacturing process is simple, but the thicker borders cool much more slowly than the useful glass causing compression and stress
Solution Approach 1:
The thicker border regions that cause differential cooling and stress are extracted and removed from the glass ribbon. By removing these borders, the remaining glass ribbon has uniform thickness throughout, eliminating the differential cooling effect and the associated compression and stress.
4Ease of manufacture
If conventional severing methods like scoring or laser scribing are used on cold glass, then the borders can be separated, but broken edges with roughness and microcracks result
Solution Approach 1:
The border severing is performed preliminarily while the glass is still hot and has appropriate viscosity, before the glass cools and becomes brittle. This timing allows the severing to produce smooth edges without microcracks, as the glass can deform plastically during separation rather than fracturing.
Solution Approach 2:
The physical state parameter of the glass (temperature and viscosity) is changed during the severing process. By maintaining the glass at elevated temperature with viscosity in the range of 10^7 to 10^11 dPa·s during severing, the glass exhibits ductile behavior that produces smooth edges. After severing, the glass cools to the annealing point where it becomes solid and maintains the smooth edges.
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
The method produces thin glass ribbons with high mechanical quality, reduced stress, and minimal secondary border formation, enabling more efficient coiling and bending with improved reproducibility and lifespan.
Implementation Method 1
the borders are severed from the thin glass ribbon by means of a severing device (9), in particular by means of a laser (9a)
Implementation Method 2
A method involving the severing of borders from a thin glass ribbon at a specific viscosity range (10^7 to 10^11 dPa·s) using a laser to melt and separate the glass
Implementation Method 3
the thin glass ribbon cools down after having been drawn
Data Source
AI summary
An improved method and an improved apparatus are provided for producing a thin glass ribbon, which provide borders at the edges of the ribbon. The edges formed are of high mechanical quality and a formation of new secondary borders after the severing or at least the thickness of such secondary borders is reduced compared to the original borders. The method includes drawing the thin glass ribbon from a molten glass or from a preform, severing the borders, and cooling the resulting glass ribbon. The severing is effected at a location along the moving direction of the thin glass ribbon and at a time at which during the cooling of the thin glass ribbon the viscosity of the glass is in a range from 107 dPa·s to 1011 dPa·s, so that the edges of the thin glass ribbon newly produced by the severing of the borders are rounded off.