Down-draw Glass Cooling Temperature Control
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Solution Overview
Problem
Existing glass-plate manufacturing methods using the down-draw process struggle to achieve uniform thickness while reducing warpage and residual stresses in sheet glass.
Innovation Solution
A method involving a multi-step temperature control process during the cooling phase, where the temperature of the sheet glass is controlled to maintain uniformity in the central region and adjust the temperature gradient between the central and edge sections, inhibiting contraction and applying tensile stress to maintain flatness and reduce warpage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the temperature gradient between the central section and end sections of the sheet glass is controlled to reduce residual stresses, then the strain in the sheet glass is reduced, but the thickness uniformity cannot be achieved
Solution Approach 1:
The temperature control process is divided into three distinct stages (first, second, and third temperature control steps) with different temperature distribution patterns. This segmentation allows the process to first control thickness uniformity and then reduce residual stresses sequentially, resolving the contradiction between these two requirements
Solution Approach 2:
The first temperature control step performs preliminary thickness equalization by maintaining higher temperature at end sections before the glass reaches the strain point. This preliminary action ensures thickness uniformity is established before the glass structure becomes rigid, preventing later warpage while reducing residual stresses
2Manufacturing precision
If the temperature of end sections is kept lower than central region to increase viscosity and inhibit contraction, then thickness uniformity is improved, but temperature gradient control becomes more complex
Solution Approach 1:
The temperature control system dynamically adjusts the temperature distribution pattern through three distinct phases as the glass descends. The system transitions from a temperature profile that equalizes thickness to one that minimizes gradients at the strain point, allowing adaptive control that achieves thickness uniformity without requiring permanently complex equipment
Solution Approach 2:
The invention changes the temperature parameters (distribution and gradient) at different stages of the cooling process. By varying the temperature profile from the first to third control step, the system achieves thickness uniformity through controlled viscosity changes without requiring complex permanent temperature control mechanisms
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 effectively achieves uniform thickness and minimizes warpage and residual stresses in the sheet glass, ensuring high-quality glass plates with reduced strain and thickness deviation.
Implementation Method 1
In the cooling step, the sheet glass is cooled while drawing the sheet glass downward with rollers
Implementation Method 2
the temperature of the sheet glass falls below a temperature region near the strain point of glass
Implementation Method 3
a temperature gradient between each end section and the central section in the width direction of the sheet glass is minimized in the aforementioned temperature region near the glass strain point
Data Source
AI summary
A glass-plate manufacturing method employing a down-draw process includes: a forming step of forming a sheet glass by making a molten glass flow downward along opposite side surfaces of a forming member and merge at a lower section of the forming member; and a cooling step of cooling the sheet glass while drawing the sheet glass downward with rollers. In the cooling step, an above-glass-strain-point temperature control step is performed which is a step of performing a temperature control in the width direction of the sheet glass in a temperature region ranging from the lower section of the forming member to where the temperature of the sheet glass falls below a temperature region near the glass strain point, and includes: first, second and third temperature control steps as defined herein.