glass working Flashcards
majority of glass is used in
packaging e.g. jars, bottles
glass also used in
construction e.g windows
transport applications
challenges glass presents as a production material
1)high energy consumption (melting raw materials to produce glass)
2)handling and transport (glass fragile)
3)quality control (consistent, free from defects e.g. bubbles, stresses) during manufacturing
4) temp sensitivity (carefully cooled to avoid stresses that leads to breakage/defects–precision)
5) produces waste materials, can be recycled but process must maintain quality, avoid contamination
3 key features of glass shaping
1) precision molding (using molds to shape molten glass in specific forms, ensure accurate and uniform)
2) blowing (molten glass inflated into a bubble, then shaped by blowing air through pipe)
3) pressing (molten glass pressed into molds using plunger, creates precise shapes, smooth surface)
4) drawing (molten glass pulled into thin strans/sheets–glass fibres, window panes)
5) rolling
6) cutting and grinding
7) tempering and annealing
contempory glass production has a x degree of y
x: high
y: automation
Material removal processes can be {1}. Glassworking is principally a set of { 2 } techniques. Glass has a unique set of properties: {3,4,5}. Glass is the most { 6 } material.
1: challenging/difficult
2: hot-shaping
3, 4, 5: chemical, mechanical, aesthetic
6: widely recycled
main component of glass
Silica
Other components of glass
soda ash, limestone, aluminium oxide (potash)
recycled glass ({1}) is typically added up to {2}% of the charge
1: cullet
2: 50
after the batch is mixed, it’s {1} in a furnace {2: x-y °C) to obtain {3} glass for {4}
1: heated
2: 1500-1600
3: molten
4: shaping
the melting cycle takes between x-y hours
24, 48
what type of moulding is ideal for wide mouthed jars and vases
press and blow
what type of moulding is ideal for narrow necked bottles? e.g. {1}
blow and blow
1: beverages, perfumes
for blow and blow moulding, {1} may be required between the steps and additional {2} and gob feeders may be used to increase {3} rates
1: reheating
2: moulds
3: production
what type of moulding process is annealing?
blow and blow
annealing is performed in { 1 } (lehrs), heating and {2} cooling the glass to { 3 }
1: tunnel like furnaces
2: slowly
3: resolve residual stresses
In annealing, glass is heated to a temperature just {1} its melting point. Making it pliable without causing a change in its {2}. At this high temperature, the { 3 } within the glass relax and redistribute themselves more {4}. The key part is the { 5 } phase, this {6} reduction in temperature allows to glass to { 7 }.
1: below
2: shape
3: internal stresses
4: uniformly
5: slow cooling
6: gradual
7: uniformly solidify
slow cooling helps to minimize {1} by { 2 }
1: stresses
2: even solidification
if the glass were quickly cooled, different parts/areas would {1} at different {2}, leading to the formation of new {3}
1: contract
2: rates
3: stresses
during the cooling process, any { 1 } that were present due to {2} cooling or handling during {3} are relaxed. Resulting in a more {4}, { 5 } glass structure
1: residual stresses
2: uneven
3: formation
4: stable
5: stress free
the process of annealing ensures what
the final product is stronger, less likely to crack or shatter due to internal tensions
what does annealing improve
durability and longevity of glass (making it suitable for various applications)
what is a residual stress, is it temporary? What’s the cause of it?
internal stress
remains in a member of the weldments after a joining operation
generated by localized, partial yielding during the thermal cycle of welding and the hindered contraction of these areas during cooling.
in glass production for a continuous furnace, what’s the purpose of the molten tin bath?
allows molten glass to evenly spread forming a flat sheet of uniform thickness, before annealing
Purpose of rolling of flat plate glass
forming rolls enable mechanical shaping of the glass, offering great thickness control and variation across the line
In terms of optical precision, is the float process for producing sheet glass, or the process of rolling of flat plate glass higher?
float process has higher optical precision
what’s meant by a high optical precision?
high ability to produce glass components of very accurate shape and smooth surface
what’s the importance of a high optical precision process?
high level of precision, crucial in sensitive applications were tiny imperfections impact performance
give an example of product requiring a high optical precision process
camera lenses, telescope, microscope, other optical instruments
what is precision glass moulding
high optical precision process, involves heating glass blankets, shaping into ultra-precise moulds
The result of precision glass moulding is optical components with complex {1} and minimal { 2 }, ensuring {3} performance in {4} systems
1: geometries
2: surface defects
3: optimal
4: optical
Glass is inherently {1}, {2} can solve this
1: brittle
2: toughening/tempering
During glass tempering, stresses are { 1 }. Glass is heated above its {2} temperature (approx {3}°C), to push it into the {4} range
1: strategically induced
2: annealing
3: 650
4: plastic
what happens after glass is heated above the annealing temperature and is pushed into plastic range?
surface is quenched, causing it to harden around the plastic interior
when very hot glass surfac e is quenched, it hardens around its {1} interior which cools more {2}
1: plastic
2: gradually
products that involve glass tempering are …
windows for tall building, all glass doors, safety glasses
why do windows, specifically for tall buildings, require glass tempering?
1: safety–tempering is stronger, when glass breaks it shatters into small less harmful pieces (as opposed to large, sharp shards),
2: wind pressure– tall buildings subjected to higher wind pressures, tempered glass more effective at withstanding these forces
3: thermal stress– tall buildings experience greater temp variations between inside and outside, can cause untempered glass to crack due to thermal stresses
true or false:
may building codes and regulations require glass to be tempered when used in high rise buildings
true
(safety reasons)
two disadvantages of tempered glass…
1– cost, additional process
2–alteration limitations00ince tempered, can’t be cut, drilled or altered, these modifications must be done prior to tempering
3–weaker in tension–strong under compression, less so under tension–more susceptible to breakage if exposed to extreme bending stresses
4– distortion, the process can introduce slight optical distortions– bad for applications requiring high visual clarity
why can’t tempered glass be cut or drilled?
unique internal structure created during tempering:
-internal stress–caused from rapid cooling, stresses formed from this make glass stronger, but sensitive to further modifications
-risk of shattering– cutting/drilling disrupts the balance of these internal stresses, causing glass to shatter into many small pieces due to uniform stress distribution, alterations cause stresses to suddenly release
true or false:
Once glass has been tempered, it is set in its final stress induced state, and cannot be altered without breaking
true
describe the difference between rolling and cutting&grinding
rolling-molten glass passed through rollers to produce flat sheet–architectural glass
cutting & grinding– shaping glass post production to achieve desired dimensions and finish (polishing too)
describe tempering and annealing
process to strengthen glass and reduce internal stresses, making more durable and stable
developments and advancements
the three basic types of ceramics are
glass, traditional ceramics, new ceramics
glass is distinguished by its {1} structure, other ceramic materials have a {2} structure
1: non-crystalline (vitreous)
2: crystalline
glass products commercially produced in an unlimited {1} of shapes, at {2} quantities
1: variety
2: high/large
three glass products…
light bulbs, jars
window glass
glass tubing e.g. fluorescent lighting
glass fibres
glass telescope lenses (made individually)
difference between glass and traditional & new ceramics
glass is vitreous–in glassy state, exhibits the smooth, often shiny and translucent properties
the other two are large polycrystalline materials
3 basic steps in glassworking sequence
1) raw material preparation and melting
2) shaping
3) heat treatment/finishing operations (e.g. grinding, polishing, etching) if needed
3 types of melting furnaces
1) pot furnace
2) day tank
3) continuous tank furnace
4) electric furnace
describe process of one of the melting furnaces
describe the spinning process in glassworking
similar to centrifugal casting in metal working
gob of molten glass dropped into a conical spinning mold, causing centrifugal force to spread the glass upward onto mold surface
difference between press&blow and the blow&blow shaping processes
for press&blow, initial forming step involves pressing part, for latter; first step is blowing
describe spinning process in glassworking
glob of molten glass, dropped into conical spinning mold, causing centrifugal force to spread the glass upward onto the mold surface
difference between press and blow, and blow and blow shaping process in glassworkingg
press and blow–initial step pressing the part
describe a way of shaping plate or sheet glass
1) rolling–hot glass squeezed between opposing cylindrical rolls
2) float process–melted glass flows onto a molten tin surface to achieve uniform thickness and smoothness
describe the Danner process
molten glass flows around rotating hollow mandrel, where air is blown while glass is drawn.
Air temperature, its volumetric flow rate, and drawing velocity determine diamter and wall thickness of tubular cross section
during hardening glass tube supported by series of rollers extending beyond mandrel
