How is tempered glass made? Also, how does tempering differ from strengthening glass using heat? This guide will take you through the tempered glass manufacturing process. This process includes the following steps from, when the glass is loaded on the tempering machine to when it’s tested and inspected for quality:
- Cutting normal glass to the required size and shape
- Inspecting the glass for imperfections
- Cleaning the glass
- The glass tempering stage
- Testing tempered glass
Tempered Glass Definition
Tempered glass means glass that has been made strong and resistant to impact forces and scratching by passing it through the tempering process. This involves using high temperatures to heat the glass and then cooling it fast.
Thermally tempered glass, owing to its extreme hardness and strength, has many different uses. These range from making car windows, as the main element for the windows and doors of residential or commercial high-rise buildings, and other uses.
After its definition, let’s now see how tempered glass is made. This will provide you with an insight into what goes on in the tempering process as well as the type of equipment used.
How is Tempered Glass Made?
The tempered glass-making process requires one, the raw material — in this case float glass — and two, a the use of a tempering machine. Here is what you need to know about these requirements before we can delve into the manufacturing process itself.
Tempered glass Raw Material
Tempered glass is made using ordinary glass, or glass that’s been made using the annealing process. Annealed glass is not strong, in addition to the fact that it breaks into sharp pieces that many cause injuries. This tempered glass raw material will then be cut into the needed design and shape before being passed through the tempering machine.
Tempered Glass Manufacturing Machine
The tempered glass making machine is composed of these major parts; the loading area, heating furnace, and cooling section. The loading area is where workers will place the glass pane, while the furnace is the part that will heat it. After heating, the glass is taken to the cooling chamber where it’s quickly cooled. Read more about the tempered glass manufacturing process below.
Tempered Glass Manufacturing Process
The tempered glass manufacturing process is comprised of these five major steps: the cutting stage where float glass is shaped as required, the inspection and cleaning stage where the glass is cleaned, and, finally, the heating and cooling stages.
Step 1: Cutting Float Glass
Using special cutting equipment, the glass is cut to the desired size and shapes. Custom designs may also be introduced in this step of the tempered glass production process. These include engravings, cutouts, holes, and other design features.
Step 2: Inspection
The cut glass is thoroughly inspected for any imperfections like scratches, cracks, and other defects. These are defects that may have arisen when making the glass or while cutting it. Only faultless material goes into the next part of the process.
Step 3: Cleaning
Once inspected, the glass is cleaned to remove dust and anything else that may contaminate it during the tempering stage. Sharp edges are also smoothed using a mild abrasive. This will prepare the glass for the next step of the tempered glass manufacturing process, which is heating it in a furnace.
Step 4: Heating
The clean and inspected glass is taken to the heating furnace. The glass tempered furnace then heats the glass to above 600°C (typically between 6200°C and 650°C). This will cause the metal to soften and be easy to toughen.
Step 5: Cooling
The heated glass is rapidly cooled in another part of the glass tempering machine. Nozzles blasting cold air jets are aimed at the glass on different points. This quickly cools the glass surface while the inside remains hot.
In the last stages of the process, the toughened glass is then passed through a quality control process that involves testing and inspection.
Heat Strengthened Glass vs. Tempered Glass
The difference between heat-strengthened vs. tempered glass is often confused, with many people thinking them to be the same. But while both types of glass are made strong using heat, their strength levels differ as well. Their manufacturing process steps, too.
1. First, fully tempered glass is a stronger and tougher glass than strengthened glass — about 4× to 5× that of ordinary glass. On the other hand, heat-strengthened glass is only about 2× stronger that float glass.
2. The tempered glass manufacturing process is also slightly different than that of heat strengthened glass. Heat strengthened glass is heated slowly in a controlled process. This results in some level of hardness.
In comparison, the tempered glass making process involves a more rapid cooling of the heated material, and that’s what gives it the higher strength level. As mentioned earlier, quickly cooling the heated glass surface causes it to pull at the inner surface, which results in extreme tension and hardness.
3. In terms of application, tempered glass is used in more demanding situations where the glass is likely to experience larger forces and higher heat levels. These include the construction industry, the tops of tables, basketball backboards, and so on.
Heat-strengthened glass is used where ordinary glass is too weak to make a good choice but where the higher strength and cost of heat-tempered glass is not a viable alternative. These include the screen of smartphones and tablets.
The tempered glass manufacturing process involves heating and quickly cooling float glass. This is done in a controlled way to ensure the tempered glass can offer guaranteed impact strength and safety. Based on the specified application, tempered glass manufacturers can also offer custom services for glass size and design, glass thickness, color, and other features.