Gob-Pressing Complex Glass Geometries via Mold Temperature Control
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Solution Overview
Problem
Gob pressing techniques for forming glass parts are limited by viscosity, density, and cohesion effects, making it difficult to produce complex geometries such as oblong or thin glass articles with large surface areas.
Innovation Solution
The development of new mold structures with controlled local temperatures, precise control of gob volume and flow rate using a platinum auger, and pre-shaping of gobs before pressing, along with a multi-stamp technique, enables the formation of complex glass geometries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional gob pressing is used to form glass parts, then simple geometries can be produced, but complex geometries such as oblong or thin glass articles with large surface areas cannot be produced
Solution Approach 1:
The patent applies preliminary action by pre-heating the mold cavity and surfaces before introducing the molten glass gob. This pre-heating prevents premature cooling and solidification of the glass as it flows into complex geometric regions, enabling successful formation of thin-walled and oblong geometries that would otherwise be impossible to produce by traditional gob pressing
Solution Approach 2:
The patent changes the temperature parameter of the mold from conventional room temperature or moderate heating to high-temperature pre-heating (approaching glass melting temperature). This parameter change reduces the temperature gradient between molten glass and mold, preventing rapid cooling and viscosity increase that would block glass flow into complex geometric features
2Shape
If the gob is pressed into the mold, then the glass spreads outward to form the shape, but the glass cools too quickly to reach and fill thicker portions of the mold
Solution Approach 1:
The mold cavity and surfaces are pre-heated to high temperatures before glass introduction, creating a thermal reservoir that maintains glass temperature during flow. This preliminary thermal preparation prevents the glass from cooling below its working viscosity range, enabling it to reach and fill distant thick portions of complex geometries
Solution Approach 2:
The heated mold acts as a thermal intermediary between the hot molten glass and the cooler external environment. By maintaining the mold at elevated temperature, it mediates heat transfer to prevent excessive cooling of the glass, allowing sufficient time for complete geometric formation
3Area of moving object
If the glass spreads to form thin articles with large surface area, then the desired geometry is achieved, but the glass becomes too viscous and resists spreading
Solution Approach 1:
Pre-heating the mold surfaces creates a favorable thermal environment before glass contact, reducing the temperature differential that would cause rapid cooling. This allows the glass to maintain low viscosity throughout the spreading process, enabling uniform distribution over large surface areas without premature solidification
Solution Approach 2:
By changing the mold temperature parameter to high values, the patent reduces the rate of heat extraction from the molten glass. This parameter change maintains the glass in a low-viscosity state longer, enabling complete and uniform spreading across large surface areas before viscosity increases to resist further flow
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
These techniques allow for the efficient formation of glass parts with complex geometries that were previously difficult or impossible to produce by gob pressing, while minimizing material waste and reducing the need for extensive post-processing.
Implementation Method 1
The mold structure includes gaps purposely built into the mold, beneath surfaces thereof, that limit heat transfer to and from the surfaces
Implementation Method 2
The system includes an auger of platinum that spins to a controlled degree, direction, and rate to move molten glass into a gob
Implementation Method 3
Molten glass within a gob-pressing operation has viscosity and density, as well as complex momentum and cohesion effects
Data Source
AI summary
The present disclosure is directed to methods and techniques for gob-pressing a glass part of challenging geometries, such as large surfaces with thin thickness as well as features positioned far from a centroid of the part.