Sheet Metal Fabrication Processes

There are three main types of sheet metal fabrication: forming, cutting, and joining. 

Forming

Forming includes processes like stamping, bending, stretching, and roll forming. While cutting subtracts material from a piece of sheet metal, forming simply reshapes it to the desired contours.

• Stamping, uses single or progressive dies to press the metal into the desired form. The technique uses two dies with a sheet of metal pressed between them.
• Bending can be done either by press brakes or by hand.
• Stretching, as is implied in the name, pulls metal apart via stretcher, hammer and dolly, or English wheel.
• Roll forming has similar effects to bending. However in this process the entire sheet of metal passes through a pair of rolls to form the material into the right shape so it can be bent all along its length into a coil.

Cutting

There are two different types of cutting: with shear and without shear. Shear cutting includes processes such as shearing, cutting, and blanking. These types of cuts are more commonly used for nonindustrial end products, since they are less precise than processes without shear.

• Basic cutting uses a single blade to cut through the material.
• Blanking is a more powerful version of the same process a hole punch uses to cut out holes in paper. A machine punches shaped pieces out of a sheet of metal, and the leftover sheet is discarded.
• Shearing involves the same type of action as scissors, using upper and lower blades that make cuts in straight lines. However, with shearing, one blade remains stationary while the other lowers down.

Non-shear cutting, which is more accurate, is used specifically for industrial products like airplane wings. These processes include laser beam, plasma, and waterjet cutting services, as well as machining.

• Laser cutting uses a focused beam of light for cutting through or engraving the material.
• Plasma uses heated compressed gases like nitrogen and hydrogen, which exit the nozzle as such high speed they become ionized and conduct electricity.
• Waterjet cutting shoots high speed, concentrated streams of water filled with abrasives to erode a cut into the material.
• Machining uses a tool like a drill bit or lathe blade to cut off pieces of material. This can include processes like milling and spinning.

Joining

Joining encompasses the processes of welding, brazing, riveting, and adhesive use.

• Welding comes in several forms, including MIG, TIG, and stick. It acts by fusing the metal sheets together through melting them, while adding a filler.
• Brazing is a similar process, but it acts by melting a filler without melting the sheets.
• Riveting relies on small metal parts to join sheets of material by embedding them through both sheets.
• Adhesives hold together metal sheets either alone, as in the case of structural adhesives, or in conjunction with another joining method, as with machinery adhesives.

Once the metal has been fabricated there are finishing processes that can be performed to enhance its properties, including sandblasting, deburring, annealing, and coating.