How Safety Glasses Are Made and Tested?

How Safety Glasses Are Made and Tested?

Safety glasses save thousands of people’s eyes every single year. In the U.S. alone, 2,000 work-related eye injuries happen every day according to The Bureau of Labor Statistics. By wearing a proper pair of safety glasses you can avoid 90% of Work-Related Eye Injuries. 

So how are these safety glasses made and tested? This is what we will learn in this article.

Safety glasses are made by using an injection molding process that injects a polymer material such as polycarbonate into a metal mold to a temperature of 250°C, where it is liquid and injected into the mold under pressure for 30-60 seconds to reproduce the desired shape of the lenses and frames.

Safety Glasses Parts

Safety Glasses Parts

Safety glasses are composed of six parts:

  • The Frame 
  • Top shield 
  • Side shield 
  • Lenses 
  • Bridge
  • Arms

But the most important two parts in any pair of safety glasses are the lenses and the frame because they are the ones that are responsible to protect your eyes from impact by absorbing the shock.

The Process of Making Safety Glasses

Plastic Molding

Safety glasses are made by plastic molding, the optical part of the lens is mirrored to be as transparent as possible without being deformed. The glasses are made by melting the primary material such as polycarbonate.

Injection Molding

The Polycarbonate pellets are fed into an injection molding machine that heats the material to a temperature of 250°C, where it is liquid and injected into the mold under pressure for 30-60 seconds.

The glass hardens rapidly and the glasses are then removed from the mold because the glasses are separated by hand and then are given an initial visual inspection. The glasses are placed on a support and then taken to the laboratory where they’ll be given a surface treatment. 

Surface Treatment 

The glasses are washed to eliminate any impurities and to assure that the coating treatment adheres well to the lens. After the wash, the glasses are rinsed in clearwater, then they are soaked in a chemical solution that will prevent misting and scratching of the lens. 

The glasses then are cooked in an oven heated to 120°C, the soaking and cooking processes vary between 30 minutes and 2 hours each. Each pair of safety glasses is inspected to make sure there are no imperfections or distortions in the lenses. Then the nose piece is glued on and the lenses and the frame or the ear stems are installed.

Packaging 

The final step is the packaging where the safety glasses are placed into their final packaging, then boxed and readied for storage or shipment.

How Safety Glasses Are Tested?

After the process of making safety glasses, they are sent to be subjected to various impact tests to verify that the product meets the required impact protections.

The test used by the manufacturer are:

High Impact: this test involves a 0.25-inch steel ball that is shot at the glasses with a minimum speed of 120 Km/h. The lenses must withstand the test.

High Mass: This test consists of dropping a pointed 500 g weight from a height of about 50 inches at the safety glasses. The lenses and the frame should withstand the test.

Those two tests are the most important for safety glasses to be safe. Other tests are applied by manufacturers such as Dust Test, Liquid Splash Test, penetration test, flying sparks, hot liquids, corrosion resistance, fogging, and UV Protection.

Dust Test: A large quantity of dust is thrown at the safety glasses, for safety glasses to pass this test, they should stop the dust from coming inside your eyes.

Liquid Splash Test: In this test, a paper is on a head form under the safety glasses being tested. Circles are drawn on the paper in place of the wearer’s eyes and the safety glasses are then sprayed with a liquid. The safety glasses should stop the liquid from getting into your eyes.

Penetration test: this test involves a sharp needle weighing 1.56 ounces being dropped onto the lens from 50 inches. The lenses should not be damaged to pass this test.

Flying sparks test: To pass this test, sparks must not burn in or leave any visible marks on the frame or lens.

Hot liquids: in this test a hot liquid is thrown at the safety glasses, they should stop the liquid from coming inside and remain in a good condition.

Corrosion resistance: this test is done by exposing the safety glasses to a corrosive atmosphere. To make sure they are durable and safe from hydration, rusting, or oxidation.

Anti-fogging: Not all safety glasses come with anti-fog lenses, but if they do they will be marked with “N” or you can check the product description.
UV Protection: All Polycarbonate and Trivex safety glasses lenses provide 99.9% UV protection.

Frequently Asked Questions

What Material Should Safety Glasses Be Made of?

The majority of manufacturers use polycarbonate for lenses because of its impact-resistance ability and its lightweight nature. For the safety glasses frame, every manufacturer uses its material for example Zylonite, Propionate, and synthetic polymer.

How Are Safety Glasses Rated or Certified?

Safety glasses that are ANSI Z87.1 Rated and certified in the USA or EN 166 in Europe or AS/NZS in New Zealand mean that those safety glasses have passed all the tests required for eye safety and you can wear them with confidence in your workplace.  

How Are Polycarbonate Safety Glasses Made?

The polycarbonate used in the safety glasses lens is fed into an injection molding machine that heats the material to a temperature of 250°C, where it is liquid and injected into the mold under pressure for 30-60 seconds. After this process, the polycarbonate lenses can be used in safety glasses.

What Is the Code for Safety Glasses?

In the United States, the code is Z87 or Z87+, in Europe the code is EN 166 and in New Zealand, the code is AS/NZS. Those marks help to ensure safe eyewear provides workers with the needed protection from impact.

Are Safety Glasses Plastic?

The majority of Safety glasses are made with polycarbonate, the polycarbonate is a tough, transparent, and lightweight plastic material used in safety eyewear and other sectors. Safety glasses also came with other types of plastic such as Trivex, High-index, and CR-39.

What Plastic Are Safety Glasses Lenses Made From?

Safety glasses lenses can be made of Polycarbonate, Trivex, CR39, or glass; it depends on the manufacturer and the client’s requirement.

Is Trivex a Safety Lens?

Yes, Trivex is a high-impact, lightweight material that offers a crystal clear vision better than polycarbonate. Trivex is new to the market of safety eyewear but he can be a great choice for someone who wants high-quality safety glasses.

Leave a Reply

Your email address will not be published. Required fields are marked *