How Are Grinding Wheels Made | CRATEX Abrasives

#1 Grinding Wheel Evolution – From Sandstone to Superabrasives

Grinding operations, and therefore grinding wheels, have had an important place in the manufacturing industry for more than 150 years. The rapid industrialization that took over the world during the mid-19th and beginning of the 20^th century transformed the society from an agrarian into an industrial one and caused the development of large spectrum of industries. The demand for all sorts of tools, including the grinding wheels was on the rise, so people constantly sought room for improvement.

Modern-day industries cannot imagine a world without grinding wheels anymore since they are used by nearly every manufacturing company for wide variety of operations ranging from cleaning to cutting steel and masonry blocks. But, long before superabrasives and CNC machines, there was sandstone. It is probably the earliest abrasive made of quartz mineral grains that were bonded with some natural cement and used to sharpen and polish flint axes.

Then, in the early 1800s, emery was introduced to United States and Europe from India, and so the time of emery grinding abrasives begins. Emery is a natural mineral that contains corundum and iron and was predominantly used to shape and cut metals. However, importation costs and issues and variable quality of the abrasive encouraged people to explore other options and to seek abrasives that are much cheaper and available than the imported material.

By the 1890s the search led to the development of synthetic silicon carbide and synthetic corundum which eventually led to the discovery of superabrasives that we know today as synthetic cubic boron nitride (CBN), synthetic diamond, seeded-gel aluminum oxide and so on.

At the same time the developers worked on improving the boding material in the grinding wheels as well, as the improved grains were not much without an equally powerful bond. The research led to the introduction of the rubber bond in the early 1940s and vitrified bond by the 1870s.

Like we’ve seen in Chapter 1 there are numerous types of abrasives used for making grinding wheels with all sorts of bonds today, and there is no doubt that the innovation won’t stop here.

 

#2 Sugar, Spice & Everything Nice – Grinding Wheel Mixture 

Abrasive grains and the bonding material are the main but not the only components of the grinding wheel.Different additives are added as well, such as iron-oxide for wheels that cut and grind iron to enhance the metal cutting properties, or the mineral cryolite that lubricates the abrasives. Powdered and liquid resins are added to bond all these ingredients together.

Today, a computer program automatically scales and weighs various ingredients, and the process starts by adding powdered resin and additives into the mixer first. After about a minute the abrasives and liquid abrasives are added with care. After another five minutes of turning, the mixture reaches the consistency of a damp beach sand and is called “blend”. Last step in this phase is screening out globs and chunks, so that the mixture has a smooth and even texture.

 

#3 And Then There Was Wheel – The Molding

First, a machine places a reinforcement disc made of fiberglass at the base of the wheel, after which a device called a shuttle spreads the mixture or “blend” into a wheel shaped mold. The diameter and depth of the mold cavity corresponds to the dimensions of the model of the specific grinding wheel. Next, a galvanized steel ring designed to protect the shaft that spins the grinding wheel is placed in the center of the wheel.

Lastly, a pressure force press applying the pressure of up to 5000 pounds per square inch compacts the blend into its final shape and size (by the way, that’s the weight of about 30 cars in case you are wondering).

The mold is then removed from the press and the wheel carefully striped from it. Every single grinding wheel coming off the line is weighed to ensure it meets the design specifications.

 

#4 Today’s Special - Flambe Wheel

After they’re taken of the line, the wheels are placed into an oven with temperature that rises gradually from 70 to 400 degrees Fahrenheit over a period of 24 hours. Of course, the temperature can vary depending on the types of wheels and ovens (e.g. vitrified bonds are fired to temperatures between 1700-2300 degrees Fahrenheit). The firing process cures the resin and bonds all the ingredients together.

When the grinding wheels come out, they’re hard as a rock and are resistant to heat produced by the high-speed grinding and are resistant to cleaning solvents.

 

#5 And Voila! – A Grinding Wheel

After the wheels are taken out of the oven, they are transferred to the finishing area. The last steps concerting the shaping of the wheels are: reaming the arbor holes, making the wheel circumference concentric with the edges, adjusting the shape and thickness of the wheel or creating special contours if necessary and balancing large wheels to reduce vibration during grinding. The extent of the grinding wheel quality inspection will depend on the size and the use of the wheel. Typically, larger wheels (over 6 inches in diameter) are thoroughly inspected and tested as they can be extremely dangerous if they break. As for the other wheels, the manufacturer usually monitors the quality of the material used and the production process.

The last step of the production process is labeling. Labeling is conducted by automated machinery that transfers the wheels from a station to station. The information about the manufacturer is usually labeled on the front of the wheel and the safety warnings on the back. The wheels are then packed, shipped and delivered to your home address!