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Flat Plate Glass

Ceramic Engineer from the University of Missouri-Rolla. I have worked in manufacturing since graduating from college. The process I work on has a long history and finally found its niche in the market in the late 80's. I make glass.

In the mid 50's, the world used the plate glass technique for the manufacture of flat glass. This process was very complicated as it had many additional steps to reach the final product. The plate glass process consisted of melting, drawing (Forming), annealing (Relieving stress) cutting and finally a polishing process. The polishing process was as large or larger than melting, drawing and cutting processes. With the incredible demand for automobile glass as well as archetectural glass, it was obvious that there was room for improvement.

The float process draw processes were developed to make flat glass faster and cheaper than a plate glass tank. The float process consisted of a melting, forming (Float), annealing and cutting process. The break through with the float process was in forming the glass. The glass was actually floated on top of a molten tin bath. The result was a pristine top surface (Glass was flat and had no contact with other material) and the bottom was acceptable for use by the customers criteria. This process eliminated the very costly and in many cases quality riddled polishing process of the plate glass process. The major benefit of the process was the speed that glass could be made. One float process would easily out produce several plate glass processes.

The other process was called the fusion process (The process I work on now). This process consisted of melting, forming (Which included annealing) and cutting. The truly unique portion of this process was forming. It consisted of glass being poured at a constant rate over a specially designed refractory trough. The result was an exceptionally flat surface. This flat surface was not only superior to the float process, but was of much higher quality due to the fact it had not touched any other materials during the forming process. In addition, the glass could be made much thinner. To picture it, you have to imagine glass flowing over both sides of a container. At the bottom of the container, both sides of the glass then meet and "Fuse". This is why it is called a fusion process. The surfaces that had touched materials were now locked into the center of the sheet and posed no threat to the quality of the glass. The major problem with the process was speed. This process was faster than a plate glass process, but not as fast as the float.

Unfortunately, the customers did not appreciate the higher quality and of course were more moved by the volume discounts that the float process realized. The company I work for got out of the automotive supply business, but realized that they had a very special process which could deliver a far superior product with regards to flatness. The problem was finding a use. Over the next couple of decades the process was used for several products, but none of them ever were very successful.

In the 80's, the laptop computer started to become popular. This was one of the latest attempts by the company to find a use for this process. The glass used for the display monitor on a laptop is actually a LCD sandwhich. The top and back substrates that contain the LCD's are actually glass. This glass must be very flat and free of scratches and any other defects that would affect the transmittance of light. At this time, 1.1mm glass was used for the laptop applications. This was a excellent fit for the fusion glass making process. After nearly 30 years, this process had found the proper application.

Currently, the fusion process is used not only for the monitors on laptops, but is in flat screen LCD desktop monitors and flat screen LCD TV. The thickness continues to decrease on the glass used and is now a fairly normal .7mm. If you are viewing this post with a flat screen LCD desktop monitor or a laptop computer, there is about a 70% chance that the company I work for made it.

Now that you know that your screen is glass, dont worry, it won't break easily!

This what your looking for Nighthawk?

Vincenzo.

Glass Plate Flat

Now, I admit I know very little about glass or ceramics. I am also weak in general chemistry.

Is there an environmental concern about the molten tin bath used for the float process? Does it produce fumes that are harmful to the operators and technicians?

What kind of temperatures do you use for these processes? For example, what is the temperature of the tin bath, what is the temperature of the molten glass, and what is the temperature of the annealing process?

How do you make the glass strong enough to put up with the kinds of abuse it takes on laptop monitors? 0.7mm is very, VERY thin. Are there special additives in that make the glass strong?

Rather off topic, but...

This is exactly what I am looking for. Great post. Please remember to start a new topic whenever you add a completely new subject to the board. For example, I would love to know how automotive safety glass is made. That would be a different topic, as would a topic on glass blowing or casting.

Flat Plate Glass UFO & Writing Art Education Sciences

Actually the molten tin is contained in a nitrogen atmosphere. This minimizes any oxidation and keeps it in the metallic state. About 2-5% hydrogen is added to pick up any stray oxygen that enters the tin bath. The glass at this part of the process is usually about 1300C and leaves at temperatures of 1000C. It is then annealed.

The biggest place for environmental concern is the actual melter of the glass. This is where the raw materials (sand, limestone, boric acid, arsenic/antimony, soda ash and several other materials) are actually transformed to a glass state. During the melting process, there are a great many volitals which must be captured. The use of natural gas or liquid propane ensure a fairly clean burning source.

The way that we clean the exhaust is to take the air flow from the melter and cool it down rapidly. The melter runs at peak temperatures of approximately 1600C. The gasses are rapidly cooled with adding outside are to a temperature of about 500C. At that point, atomized water is sprayed into the stream of air to take the temperature down to about 80C. At this temperature, all the harmful elements have left the gaseous state and returned to particulate. We then use a filter to screen the particulate out. The particulate actually can be re-entered into the glass (since it contains many things that we need in the glass anyway). This avoids landfilling cost of hazardous waste and lowers our cost for raw materials.

The annealing process occurs mostly around the 650 to 450C range for float and plate glass. Annealing in the fusion process occurs more around the 900 to 450C, as stress is also attempted to be controlled and the speeds through this part of the process are much faster.

There is actually nothing done to the glass other than the annealing that gives the laptop monitor strength. The double layer of glass that sandwhiches the LCD does add a good bit of strength. A screen has approximately 200psi of strength, so a direct impact has to be fairly strong or very pointed to break it. You are much more likely to scratch a monitor than break it with a impact.

It is a VERY hot process!

I will get you something on automobile safety glass soon.

Vincenzo

Glass Plate Flat

Artificial intelligence accelerates discovery of metallic glass. Combining artificial intelligence with experimentation sped up the discovery of metallic glass by 200 times. The new material's glassy nature makes it stronger, lighter and more corrosion-resistant than today's best steel. Source 8r.