Glass Tempering Roller Waves Air Support Furnace
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Solution Overview
Problem
Conventional glass tempering processes in roller-hearth furnaces result in roller waves and end edge sag due to temperature-related deformations, leading to quality defects and increased energy consumption, especially when attempting to achieve higher tempering temperatures for thinner glass sheets.
Innovation Solution
A method involving a roller-hearth furnace followed by an air support furnace, where the transfer temperature is set between 620° C. and 675° C., and the tempering temperature between 650° C. and 720° C., allowing for higher tempering temperatures without significant increases in roller waves, and optimizing energy efficiency by reducing the length of the air support furnace and increasing the roller-hearth furnace length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the tempering temperature is increased to achieve higher tempering degree in thinner glass sheets, then the compressive stress of glass surface is increased, but the roller wave distortion becomes clearly noticeable and unacceptable
Solution Approach 1:
The tempering process is divided into two distinct stages: a pre-heating stage in a roller-hearth furnace followed by a tempering stage in an air support furnace. This segmentation allows the glass to be pre-heated to a transfer temperature (550-650°C) where roller wave development is minimized, then transferred to the air support furnace for final tempering at higher temperatures (600-750°C) without significant roller wave development, thus achieving high compressive stress without unacceptable distortion
Solution Approach 2:
The air support furnace acts as an intermediary stage between pre-heating and final tempering. By introducing this intermediate heating zone with air support ( eliminating roller contact), the process enables temperature transition while maintaining glass flatness, allowing the glass to achieve high tempering temperatures without the roller wave distortion that would occur in a continuous roller-hearth system
2Strength
If the tempering temperature is increased to achieve higher tempering degree, then the compressive stress of glass surface is increased, but the energy consumption is increased
Solution Approach 1:
The heating process is segmented into pre-heating and tempering stages with different temperature ranges and heating rates. The roller-hearth furnace performs pre-heating at lower temperatures (550-650°C) where energy consumption is lower, then the air support furnace completes the tempering at higher temperatures (600-750°C). This segmented approach reduces overall energy consumption compared to continuous high-temperature heating in a single furnace
Solution Approach 2:
The glass sheet undergoes preliminary pre-heating in the roller-hearth furnace to the transfer temperature (550-650°C) before entering the air support furnace. This preliminary action reduces the temperature differential that the air support furnace must overcome, thereby reducing the energy consumption required for the final tempering stage while still achieving the desired high compressive stress
3Weight of moving object
If the glass thickness is reduced to improve lightness and solar radiation penetration, then the efficiency of solar panel and lightness are improved, but the roller wave distortion becomes more evident
Solution Approach 1:
The air support furnace serves as an intermediary heating zone that eliminates roller contact during the critical tempering phase. For thin glass sheets (1.7-2.6 mm), this intermediate stage prevents the roller wave distortion that would normally occur in roller-hearth furnaces, allowing thin glass to be tempered to high degrees without the quality defects that would otherwise limit its use
Solution Approach 2:
The two-stage heating process segments the thermal history of thin glass, with the roller-hearth furnace handling pre-heating where thin glass can be warmed without excessive roller wave development, and the air support furnace handling the final tempering where thin glass is heated without roller contact, thus maintaining flatness while achieving high strength
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
This approach effectively reduces roller waves, enhances energy efficiency, and allows for higher tempering degrees in thinner glass sheets, improving the quality and reducing production costs by minimizing the air support furnace length and maintaining the straightness of the glass throughout the process.
Implementation Method 1
heating the glass sheet in an air support furnace to a tempering temperature, wherein the glass sheet, while resting on an air cushion, is carried on an air support table
Implementation Method 2
heating the glass sheet in the roller-hearth furnace to a transfer temperature
Implementation Method 3
heating the glass sheet in the air support furnace to a tempering temperature
Data Source
AI summary
The invention relates to a method of heating a glass sheet for tempering. It comprises conveying the glass sheet on top of rollers in a roller-hearth furnace, heating the glass sheet in the roller-hearth furnace to a transfer temperature at which the glass sheet is transferred into an air support furnace. The glass sheet, while resting on an air cushion, is carried on an air support table and the glass sheet is heated in the air support furnace to a tempering temperature. The transfer temperature is not lower than 620° C. and not higher than 675° C. and the tempering temperature is not lower than 650° C. and not higher than 720° C.