Straight Line Cup vs Peripheral Wheel Edgers

We speak to many customers looking to purchase their first glass edger or might be in the market to upgrade their glass edger. It’s our job to help customer’s determine what machine will work best for their desired edge fabrication.

There are two types of straight line edgers on the market: one being a cup wheel edger and the other being a peripheral wheel edger.

Cup Wheel Edgers

Cup Wheel Edgers such as the SM4C & SM5C uses cup wheels to grind and polish glass. As the glass goes through the machine it hits the top of the wheel as it goes through the machine.

When the glass goes through the edger it will grind and polish by the face of the wheel and produce a flat grind. 

Cup wheel edgers use separate cup wheels to produce the flat with seamed edges on the glass, and are not designed to produce a pencil type profile. Some larger machines using minimum of 9 wheels can be used for mitering the edge as well as flat polishing. Depending on the thickness of glass used and quality of edge produced they can range from 4 wheels to 14 wheels set up on grinding spindles . These machines are commonly referred to as spindle machines when referencing how many wheel positions are used. The smaller machines with 4 and 5 wheel are typically used in smaller glass shops that do not have the space, electrical  power, budget or production to support a large machine, but still want to be able to produce a quality flat with seamed edge for their customers.
On 4 and 5 spindle machines, only one cup diamond wheel is used to grind the flat bottom of the glass. On larger machines 2, 3 and even 4 cup diamond wheels are used to produce the flat bottom of the glass, each one having progressive smaller grit sizes in the wheels, starting from course to fine. The design allows for more material to be removed from the bottom of the glass, which is needed when grinding thicker glass that tends to have more of an uneven edge. These larger machines can be set to remove more than 1/8″ from the bottom of the glass in one pass. In comparison, 4 and 5 spindle machines, having only one grinding wheel, are limited to around 1/32″ – 1/16″ of stock removal from the bottom of the glass with a single pass as they typically use a medium grit wheel.
The front and rear seamed edges are produced using separate wheels set at 45 degrees to the bottom of the glass. On 4 and 5 spindle machines, these arris wheels as they are typically referred to, can be made from a very fine diamond set into a resin compound to form the cup wheel which will give a satin finish on the seam. As an alternative, man-made stone type wheels are also used to produce the front and rear seam. These stone wheels tend to give a slightly brighter appearance to the seam, but the trade off is they wear faster. You are limited to the size of the seam using either of these types of wheels, but they will satisfy most needs on glass up to 1/2″ in thickness. On larger machines, 2 and in some cases 3 wheels are used to produce each of the front and rear seams. On a 2-wheel seam set up, a metal bond diamond wheel is used to grind the seam and a polishing wheel is used to bring it to a  bright polish. On a 3-wheel seam, a felt wheel using cerium oxide is used for extra bright seams.
Polishing the flat edge on a large machine  is done using a progression of different grit polishing wheels, each one having a different grit to clean up the grit marks left from the diamond grinding process and the polish wheel in the position before it. These wheels are manufactured using a rubber base compound and mixed with different grits of abrasive material. The last polishing wheels are impregnated with cerium oxide and some machines use a felt wheel and a separate cerium oxide mixture for the final polish. Smaller machines cut out some of these steps and can achieve a suitable polished edge. The larger machines are designed to run heavy glass and production all day long, so they can run faster, spreading out the process with different wheels. The smaller machines are quite capable of producing an acceptable quality edge. A 4-spindle machine only has one polishing wheel, so the finish is more of a semi bright polish. However, using a cerium oxide impregnated wheel on the last position on a 5 spindle machines turns the polish much brighter.

Front View of Wheel Compartment

Pos.1 Diamond wheel
Pos.2 Resin wheel front arris
Pos.3 Resin wheel rear arris
Pos.4 Polishing wheel
Pos.5 Polishing wheel

 

Cup wheel edgers allow you to change the thickness of the glass much easier than peripheral wheel edgers. Cup wheel edgers will only be able to do a Flat Polish edge profile, they will not be able to do a Pencil Polish.

The Sm5C cup wheel edger will produce a bright polish because it has a 5th Polish wheel with impregnated cerium that gives the glass a nice finish.

Peripheral Wheel Glass Edger

Peripheral Wheel Edgers such as the SM3C & SM4C uses peripheral wheels to grind and polish glass. As the glass goes through the machine it hits the top surface of the wheel. The groove in the diamond wheel is what grinds the glass to give it the pencil polish (rounded shape) or flat with seamed edge.Periphery wheels have the profile of the shape cut into the outer edge of the diamond wheel. 

 

Front view of wheel compartment on VE2plus2  2spindle periphery wheel edger.

Pos.1 Diamond wheel
Pos.2 Polishing wheel 

The SM3C & Sm4C periphery wheel edger will produce a bright polish.
Periphery wheel edgers can produce pencil edge or flat with seam profiles on the glass by using different profiled diamond and polishing wheels.
When using a flat with seam profile on a periphery wheel the quality of the edge will deteriorate as the diamond wheel wears. This can be rectified by having the wheel re dressed which will puta new flat/seam profile back into the wheel. This re dress is a service requiring you to remove the diamond wheel and sending it to an outside service department, which normally can take several weeks before you get it back so a back up wheel is recommended to have on hand. Depending on the depth of the diamond used on the wheel you should get one or two redresses out of a diamond wheel. New polish wheels come with no profile and will need to have glass run over them a few times to cut the profile into the wheel, or you can use a special very course diamond hand tool to get the profile started. Polish wheels are much softer than the diamond cutting wheel and will need more adjustments made to them as the wheel wears. It takes time and there is a learning curve to change periphery wheels for different glass thicknesses and profiles as the height of each wheel needs to be set also the centering of the wheels on the glass. It is not very efficient to be making these changes for short runs because of the set up time. An easier alternative if you plan on making a lot of glass thickness changes would be to invest in a flat polisher using cup wheels. All though you are restricted to producing a flat seamed edge only ( no pencil ) you do not have to change wheels or re set the height between thickness changes also you can very easily increase or decrease the size of the seams to suite your taste.
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