Sheet metal shearing uses a number of different machines depending on the job. For large, thin sheet metal with a straight edge for instance, many companies employee a guillotine machine, where a fixed blade lops the metal. For thicker pieces, such as for cutting gears, some companies will employ a plasma or oxy acetylene cutter, using heat and electricity to make the cut.
For welding applications, a beveled cut to sheet metal is usually desired, because it makes a superior welding joint. For this job, many companies are now using a machine with rotary cutting wheels designed to apply an angled cut to the metal.
Cutting machines with rotary cutters have certain advantages:
• The angle of the bevel can be adjusted from 22 degrees to 55 degrees;
• Unlike plasma or oxi acetylene machines, no heat is employed in the cutting process. The cutting area is free from smoke or sparks, and there is less chance of heat damage to the piece to be cut;
• They normally produce less noise than other machine cutting methods;
• The rotary action of the cutting wheel can be used to “feed” the metal along the cut, as the cutting wheel draws the metal towards it;
• The beveled cut is uniform, allowing a better use of automatic welding techniques with a steady flow of welding fill;
• A variety of different welding joints can be accommodated;
• A number of different size cutting wheels can be used, depending on the thickness of the metal and the angle of the cut.
The larger rotary cutting machines can cut sheet metal up to 2 inches in thickness. Some machines are semi-portable and can be used either as a floor standing machine or suspended from the ceiling of the factory. Normally, the cutters can be operated with a single person, operating a computer console.
With rotary cutting shears, the cutting wheels will eventually need to be replaced, depending on the usage of the machine. Most are constructed of high quality carbon steel. But with extended use, even high quality blades need replacement. On the other hand, replacing a cutting wheel is not a major undertaking and there is a minimum of machine down time. This is because the cutting wheels are designed to be removed quickly and easily to change the angle of the cut.
Not every company using a sheet metal shearing machine will need a rotary shear, because their product line may not require beveled cuts. But for those fabricating sheet metal with a welded joint, a rotary cutter can satisfy their needs.