How A Windshield Is Made

A windshield is defined as the window in front of a vehicle such as a car, bus, aircraft, motorcycle or train. Laminated safety glass is often used on most types of vehicles with the exception of the motorbike which uses acrylic plastic made for high impact. The component is made by using a combination of glass and plastic, pressed together using heat and pressure. Read on to learn more about the process of making windshields.

Glass is a flexible material which has been in use for thousands of years. The ancient Egyptians were the first to use the material as far back as 3000 B.C. Although glass is naturally found after volcanic eruptions, modern glass is made from ceramic components. There are many types of glass including float, container, cut, optical, fiberglass and specialty types. Auto glass is commonly made from a type of float or flat glass.

The first windshields were produced during the early 20th century. These were made using tempered safety glass. Tempered glass was admired for its strength and durability. Several decades later, the invention of laminated glass was used as a windshield replacement for tempered glass. Laminated auto glass is more flexible and less likely to shatter, providing better protection for passengers. What makes this type of glass stronger is the Polyvinyl Butyral (PVB) plastic sandwiched between two layers of glass. This holds the shards in place.

To create the windshield, silica, sodium oxide and calcium oxide are mixed together with a bit of water. Recycled glass or cullet may also be mixed into the concoction. Once mixed, the ingredients are poured into a large tank to be melted. The molten liquid goes into a float chamber which contains molten tin. Although both are melted to a molten state, the tin and glass do not mix together. Instead, the molten glass floats on top of the tin. The high temperatures remove any impurities while the molten tin forces the liquid glass to remain flat. As the molten glass passes through the exit, the temperature drops slightly, causing the auto glass to harden.

Several rollers are positioned outside the float chamber to pick up the hardened glass and direct it towards the lehr furnace. Although it is referred to as a furnace, the temperatures are lower compared to float chamber. Once the glass exits the furnace, it is allowed to cool down to room temperature.

Hardened auto glass is marked using a diamond scribe. The tool's edge contains diamond dust, which is used to indicate where the glass will be cut. Another machine cuts the glass along the line. It is measured and cut precisely to create as little waste material as possible. The glass sheet is then placed on a mold and heated until the softened sheet dips and follows the shape of the glass mold.

To further strengthen the windshield, the auto glass is subjected to a tempering phase. The sheet is heated to a temperature of 1565 degrees Fahrenheit or 850 degrees Celsius. It is then subjected to blasts of cold air. A piece of PVB plastic is sandwiched between two pieces of auto glass. The sandwich is heated inside an autoclave. This bonds the components together tightly and removes any trapped air.