During the earliest times of automobiles, cars were made with an open-air design. Because they did not have windshields, drivers would often wear goggles to protect their eyes from debris and wind. This was really inconvenient. During 1904, the windshield would be invented. The windshield would become an important part in protecting people from the elements of the outdoors, especially as the cars had become faster and more powerful. The early type of windshields was made from a glass that would shatter on impact and because this lead to a lot of injuries, then an alternative option was found.
Manufacturers began to make windshields using tempered glass. Tempering is a heat treatment that makes glass much harder and stronger, so that it can resist shattering. This was the main method until around the 1950s when multilayered laminated glass became popular. Laminated glass is considered to be very strong, being very similar to tempered glass, but it bends slightly on impact which adds more protection from it shattering. Now, Laminated glass windshields are considered to be the top safest auto glass type and it is required by law in most countries including the United States.
What materials are a windshield made from?
The essential parts of windshield glass are cullet, limestone, dolomite, soda ash, and silica sand. However, there are some small amounts of aluminum oxide and potassium oxide which are sometimes added.
Silica which makes up about 60 to 70% of the glass is the main ingredient and it is what makes the glass well, glass. (Quartz is a glass like substance that happens in nature and it is made from silica.) The Soda ash is what reduces the melting point of the glass mixture. Dolomite makes it easier to work with the melted material while limestone helps to improve the durability of the glass.
It is these ingredients when mixed with a small amount of water and is heated at a high temperature which causes chemical fusion which causes these ingredients to fuse into a new item which is glass.
Why Windshields Are Made Using Laminated Glass
The materials that are used to make a windshield will have some important properties. The glass will need to retain the clarity over a long time. It will also need to be made from strong materials that can provide structural support to the roof if there is a roll-over collision. The windshield also needs to be strong enough that it resists damage during a minor collision, so that the owner of the vehicle will not have to replace it after every small fender bender. The most important property is that the windshield needs to be shatter proof, so that glass shards are not sent flying during a major accident.
Laminated glass is a material that covers all of these requirements. To basic vision, a windshield appears to be basic glass, but laminated glass is made from 3 layers. The inner most layer happens to be made from polyvinyl butyral and it’s stuck in between clear tempered glass.
The design is made to serve a certain purpose. Whenever a small object like a rock strikes the windshield it could crack or chip the glass. However, because of that inner polyvinyl butyral layer, the damage is done to the outside layer of the windshield. Imagine just how dangerous it would be to be driving and every piece of debris or rock hit the windshield; it could shatter the glass. Besides being really dangerous, car owners would constantly have to spend money to replace their windshields. The glass may still need to be replaced or repaired from time to time, but laminated glass helps to provide a more durable and safer glass for vehicles.
Manufacturing Process of Windshields
Most windshields are made using the float method. It is called this because the glass just floats inside of a chamber during one of the steps for manufacturing.
During the first step, the water and ingredients are mixed together in a tank where they are placed under high heat and melted. This molten mixture is then sent through a broad and short opening into a second tank, which is the float chamber. This chamber contains a molten tin layer that is thin which is where the mixture floats.
From the second chamber, the molten glass sheet is then transported by using rollers into the lehr, which is another chamber where the glass is gradually cooled or annealed. The raw glass is what is used to make a windshield.
The annealed glass is then cut into the required size using a diamond cutting tool which is called a scribe. Then it is shaped and tempered, but this is not the last step.
Then the glass sheet is placed into a mold or on a mold with the right shape and curvature and then it is heated to the point where it is soft but not melted and that causes it to sag into or on the mold. Then it will be quickly cooled by jets of cold air. This tempering process really hardens and strengthens the glass.
The last step happens when two tempered glass sheets are put on each side of polyvinyl butyral. These layers are heated inside of an autoclave and then pressed between rollers. This makes the polyvinyl butyral transparent and then fuses the glass and the polyvinyl butyral into a single layer of laminated glass. The polyvinyl butyral is what gives the glass the anti-shatter protection if there is a collision and it also holds the glass shards from traveling at high speeds.
Different moldings, sensors and attachments can be added or made into the glass. These can include everything from multi-use antennas to hydrophobic coatings to rain sensors.
The windshield is now ready to be fitted and then bonded into the frame of a car. Special primers, sealants that have polyurethane and adhesives are used for this.
How Windshields Are Sized
The windshield size actually depends on the vehicle design. During the manufacturing process, sheets of tempered glass are cut using a diamond scribe to fit the glass to the specifications of the manufacturer. The polyvinyl butyral layer is also cut to fit the same size. After the pieces are cut and then molded to the right shape, they may be assembled to make one layer. This process is finished in an autoclave, which is a special oven that uses pressure and heat to bond the layers. The windshield will emerge ready to be installed in the right shape and size as stated by the vehicle manufacturer.
Because the size of the windshield is based on the specifications of the design of the vehicle, there are almost as sizes of windshields as there are car models. It is for this reason that it is almost next to impossible to be able to replace a windshield from one car to another. For safety reasons, this is not a good idea. If you need to replace your windshield, then a new one that fits your vehicle will need to be ordered.
Because of the curve of the windshield it has been made for the design requirements, ant is not possible to cut a larger windshield to fit a car. This could cause a windshield to not have the right curve and it will not fit properly. A windshield should only be replaced with the right size of windshield based on the specifications of the manufacturer. This is on area which there isn’t a repair that may be implemented safely.
Because of the design standards, the windshield sizes are increasing even as tiny cars are being made. The aerodynamic designs of the future allow better visibility and help to increase the safety on the roads. It is predicted that the windshield sizes will continue to increase in relation to the size of a vehicle.
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