Stack Progressive Pressing for Glass Shaping
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Solution Overview
Problem
Pressing techniques for making shaped glass articles often result in shear marking, warping, optical distortion, and low dimensional precision due to issues like cold skin formation and surface quality problems when molten glass is used, and reheating preformed glass may not fully address these issues effectively.
Innovation Solution
A method and apparatus that involve preparing a stack of preformed materials and forming molds with an edge portion extending beyond the mold's periphery, heating the stack to a forming temperature near the glass's softening point, and advancing it through a constriction to fold the edge portion into contact with the mold, allowing for the formation of shaped articles with improved precision and surface quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If molten glass is pressed into a desired shape with a plunger, then shaped glass articles can be formed, but shear marking, warping, optical distortion, and low dimensional precision occur due to cold skin formation and surface quality issues
Solution Approach 1:
The glass is preformed into a preliminary shape before the final pressing operation. This preliminary forming allows the glass to be shaped in stages, reducing the risk of cold skin formation and shear marking during the final pressing, thereby improving dimensional precision while maintaining ease of manufacture
Solution Approach 2:
The invention changes the temperature parameter control during pressing, maintaining the glass at a consistent forming temperature throughout the process. This prevents cold skin formation and ensures uniform viscosity, eliminating warping and optical distortion while achieving high dimensional precision
2Ease of manufacture
If preformed glass is reheated to low viscosity and pressed into a shaped article, then shaping can be achieved, but issues with surface quality and dimensional precision persist
Solution Approach 1:
The invention optimizes the temperature parameter to maintain glass viscosity within a specific range during pressing. By controlling the temperature to prevent the glass from becoming too cold or forming a cold skin, the process achieves both ease of shaping and high surface quality with minimal defects
Solution Approach 2:
The glass undergoes preliminary forming before final pressing, allowing surface preparation and initial shaping to occur under controlled conditions. This preliminary action ensures that the final pressing operation produces articles with high surface quality and dimensional precision
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 enables the production of shaped articles with enhanced dimensional precision and surface quality by controlling temperature differentials and using a system with a constriction to accurately form the glass, reducing defects like shear marking and warping.
Implementation Method 1
heating the stack to a forming temperature near a softening point of the glass
Implementation Method 2
advancing the stack through a constriction that has an internal surface configured to fold the edge portion of the preformed material into contact with the external surface of the forming mold
Implementation Method 3
a temperature differential may exist between the periphery of the stack and the center of the stack
Data Source
AI summary
A method for forming shaped articles (28′) includes preparing a stack (26) having at least an adjacent set (27) of preformed material (28) and forming mold (30), where the preformed material (28) has an edge portion (34) that extends beyond a periphery of the forming mold (30), and the forming mold (30) has an external surface (32) with a desired surface profile of a shaped article. The stack (28) is heated. The stack (28) is advanced through a constriction (56) that has an internal surface configured to fold the edge portion (34) of the preformed material (28) into contact with the external surface (32) of the forming mold (30) as the edge portion (34) passes through the constriction (56), thereby forming a shaped article (28′) from the preformed material (28). The shaped article (28′) is then separated from the forming mold (30).