Metal fabrication

Metal fabrication is the technical process of creating metal structures. It involves cutting, bending, and assembling various raw materials. This is a value-added process because it turns simple materials into complex machines or parts. A shop that performs this work is called a fabrication shop, or a "fab shop." These shops usually win contracts by bidding on specific engineering drawings.

The fabrication process begins with cutting the raw material into specific shapes. Workers can use manual tools like saws, shears, or chisels. They can also use handheld torches, such as plasma or oxy-fuel torches. Many modern shops use numerical control (CNC) cutters. These computer-operated machines use lasers, water jets, or mill bits to cut with high precision. Some shops use burn tables, which are CNC torches powered by natural gas. In advanced setups, robots move the cutting head in three dimensions around the metal.

After cutting, the metal undergoes forming to change its shape. Forming converts flat sheet metal into three-dimensional parts. This process applies force without adding or removing any material. To do this, machines use tools called punches and dies. The force must be strong enough to cause permanent deformation. Most metallic materials are ductile, meaning they can bend without cracking or breaking. This allows fabricators to create repeatable shapes for industries like aerospace, automotive, and construction.

Assembling is the stage where individual pieces are joined together. Welding is the primary method used in steel fabrication. To prepare, workers might tack-weld parts in place and check them for accuracy. They may also use a fixture to hold multiple parts in the correct position. Other joining methods include riveting, using threaded fasteners, or using adhesives. Some pieces are joined by further bending, such as creating crimped seams.

Welding introduces significant heat, which can cause metal to warp. This warping is a common challenge in creating weldments, which are products produced by welding. To prevent warping, workers might use staggered welding or a stout fixture. They might even cover the metal in sand while it cools. If the metal does warp, a skilled welder can use an oxyacetylene torch to straighten it. They apply heat in a slow, linear sweep to make the steel contract. Some parts, like engine blocks, may also be annealed in a low-temperature oven to relieve stress.

Fabrication overlaps with several other metalworking specialties. Machine shops focus on machining, which is the removal of material from a metal block. They use lathes, mills, and drills to create solid components like gears, bolts, and screws. While machine shops and fabrication shops have overlapping skills, fab shops focus more on preparation and assembly. Other specialties include blacksmithing, which has always involved fabrication. Historically, boilermakers specialized in making boilers, while millwrights focused on setting up grain and saw mills. Today, ironworkers, also called steel erectors, use prefabricated segments from fab shops to build structures on-site.

Fab shops work with a wide variety of standard materials. These include plate metal, checker plate, and tube stock. They also use structural steel, casting, and expanded metal. To join these pieces, they utilize welding wire, welding rods, or flux. The finished product is often cleaned through grinding or sandblasting. Finally, it may be primed and painted before being inspected and shipped.