What is curved or bent glass and how is it manufactured? In this guide, we explain how curved glass is made. Not only that, but also the different methods that may be used to make this type of glass, including the advantages and limitations of each of these techniques. To begin with, the definition of curved glass.
What is Curved Glass?
Before we can see how curved glass is made, here’s is what it is: also called bent glass, this is flat glass that’s been carefully made to curve, whether once or severally. The curved nature makes it useful in many different industries where it offers both visual and functional benefits.
For example, bent glass makes the windows of buildings elegant and gives staircase railings a modern look. When used for car windshields, it offers both safety and durability. In the electronics industry, bent glass is used to protect the screens of electronic products, such as mobile phone and televisions
Based on the required features, curved glass can be normal glass that’s been passed through a hot bending process, or it can be glass that bent and strengthened at the same time in a tempering furnace. For more about that, let’s now see how curved glass is made.
How is Curved Glass Made?
Making curved glass is a critical process that requires the use of both expert knowledge and specialized equipment. Below, we explore how curved is made in two different ways: with the help of gravity force (the slump method) and with the use of mechanical force.
Making Curved Glass Using Gravity
This method relies of the natural pull of gravity to bend glass. During the process, normal glass is heated to the required temperature, which is just when it begins to soften. The mass of softened glass then slumps onto a curved mold where it cools and hardens.
The slump method is a less expensive method of making curved glass. It uses only a few and simple steps, plus it doesn’t need many specialized manufacturing tools or equipment to bend the glass—only the mold and heat.
That being said, the method is best used if the bent glass design is less intricate, such as when making single, gentle curves. For multiple curvatures or complex shapes, the forced process is the more preferred technique.
Making Curved Glass Using Force
Unlike the slump method, making curved glass using force requires specialized equipment. This typically includes a heating station to soften the glass and rollers or a press to guide the bending process. The mechanical force can be automatic and driven by an intelligent system, or manual and directed by technicians.
Curved glass production using force, being a controlled process, can produce complex bent glass design options. So it’s used for products that require greater dimensional precision and other specifications such as strengthening. These include curved glass for mobile phone screens and TV’s, car windshields and more.
Because of the higher requirements, this method of making curved glass is more costly. It also needs skilled personnel to use. However, the use of controlled force allows manufacturers to ensure consistency in their products, which is crucial for large production runs.
Curved Glass Manufacturing Process
The curved glass manufacturing process, whether using mechanical force or gravitational pull, is composed of several steps. These include the following: preparing the glass for bending, heating the glass, shaping the heated glass, cooling, finishing, and the quality control stage. Here is how to curve glass using the mentioned steps.
Step 1: Material Preparation
- The raw material that will be used for making curved glass is selected
- This is usually a glass sheet of normal float glass, although that also depends on the required end product
- The flat glass sheet is then edged and cleaned to remove any materials and cut into the desired shapes or sizes.
Step 2: Heating
- Next, the glass is heated, usually at 600 °C and higher
- Heating the glass makes it soft and easier to bend
- Once soft, the glass can now be safely made to bend
- The level of heating depends on many factors, such as glass type and the required strength
- When the glass is needed strong, it requires heating in a tempering before being quickly cooled.
Step 3: Curving
- The curved glass manufacturing process now moves to its main step; bending
- Using gravity or mechanical force, the glass is shaped as desired
- In the gravity or slump method, the glass falls, on account of its own weight, into a curved mold
- Once in the mold, the glass will have taken the desired curvature, and can now be cooled
- For smaller pieces and lower production runs, a simple press may be used
- In a fully industrial process, a machine consisting of a heating furnace and hydraulically-controlled rollers is used
- This machine moves heated glass back and forth between a set of rollers and bends it to the required curvature.
If necessary and as stated earlier, the glass may be heated in a special tempering furnace to strengthen it, or laminated in addition to being curved. This helps produce toughened, curved glass that can be used in a number of industries such as automotive, electronics, or the building industry.
Step 4: Cooling
- The curved glass is now slowly cooled, normally at room temperature, until it hardness
- Note that when making strengthened bent glass, the cooling process is quickened
- This produces a layer of tension on the glass surface, making it tough enough for demanding applications
- The solidified, bent glass is then finished as appropriate, depending on the required features
- Finishing options when making curved glass include polishing, acid etching, and applying a coating to its surface.
Step 5: Quality Control
- The curved glass manufacturing process ends with a series of quality control measures.
- Here, the glass is checked for any defects in its surface and curvature.
- The glass also tested for dimensional accuracy before being shipped for use on different products and other applications.
That’s how curved glass is made. Note that different types of applications require a specific type of this glass. Some, such as display cases, may do with normal glass. Others, such as the bent glass for use in buildings and digital product displays or car windshields, may need a tougher form of the glass. All these are possible based on the specific curved glass manufacturing process.