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Sheet metal fabrication is an umbrella term for a group of processes that use sheet metal to build machines and structures. It can be a complex process involving many different professionals. Businesses that specialize in sheet metal fabrication are commonly referred to as fabrication shops, or fab shops for short.
Metal has been hand-hammered into sheets and used for architectural purposes since ancient times. Water-powered rolling mills replaced hammering in the late 17th century. This method of flattening metal used large rotating iron cylinders to press metal pieces into sheets. The metals used were lead, copper, iron, zinc, and later steel. Tin was frequently used to coat iron and steel sheets to prevent rusting. This tin-coated sheet metal was called "tinplate."
Although we've already covered types of metal fabrication on a broader level, this article will focus on the materials, processes, and tools related to sheet metal fabrication.
Sheet metal can come in a wide variety of types, and fabrication can adapt the metal to whatever purposes you may need. Types of common metals used in sheet metal fabrication include:
There are a multitude of types of steels for all sorts of purposes, such as stainless steel, carbon steel, and galvanized steel. Lower-carbon content steel may be found in railings or fences, while medium carbon content steel is used for cars and appliances. The highest carbon content sheet metal is frequently found in steel wires. Stainless steel is used for cookware, medical instruments, and many other products.
Aluminum is more lightweight while also sharing some of steel's strength. It's good for lower temperatures, which partially accounts for its use in aerospace and refrigeration. Aluminum sheet metal is also used for automotive parts, electrical devices, and cooking vessels.
Magnesium is a structural metal with a very low density, excellent for when stiffness is needed. It has been used as a structural metal in the transportation industry since World War II and is used for automotive parts.
Brass has useful acoustic properties, but is also used often for fittings and components. It is lightweight and corrosion-resistant metal and has a high tensile strength.
Bronze sheet metal has a low melting point and is stronger than copper, with applications in coins, cookware, and turbines.
Copper is ductile, malleable, and electrically conductive, as well as corrosion-resistant. Copper metal sheet is often used for conductors, electrical parts, ornaments, and jewelry.
There are three main types of sheet metal fabrication processes: forming, cutting, and joining. We'll outline each one.
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, which is explained in more detail here, 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. V-bending is the most common sheet bending method as it is used for most bending projects. It uses an instrument known as the punch and v-die to bend sheet metal at the desired angles.
Roll bending is used to bend sheet metals into rolls or curves. It uses a hydraulic press, a press brake, and three sets of rollers to make different bends or a big round the bend.
Stretching, as is implied in the name, pulls sheet 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.
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 sheet metal.
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 sheet 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 to cut the sheet.
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 sheet metal. Laser cutting is very quick, with machines moving 20-70 inches per minute. The process is able to create highly detailed, small cuts and tight
tolerances, making it a good choice if intricate cuts are needed.
Machining uses a tool like a drill bit or lathe blade to cut off pieces of sheet metal. This can include processes like milling and spinning.
Joining encompasses the sheet metal fabrication 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 sheet metal. It uses a torch that produces a high intensity flame.
Riveting relies on small metal parts to join sheet metal pieces by embedding them through both sheets. It is a faster and less expensive process than welding.
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 sheet metal has been fabricated there are finishing processes that can be performed to enhance its properties, including sandblasting, deburring, annealing, and coating.
Sheet metal fabrication relies on a special set of tools across its processes to force the metal into the desired shape. Across multiple categories, however, CNC (Computer Numerically Controlled) machines have become a popular tool. CNC machines are computers that are programmed to perform specific tasks and achieve the exact specifications required to manufacture many products. They have gained enormous popularity for their precision and reduction of labor costs. Their use has contributed to the increasing need for CAD files, which can be loaded into the computer to perform turning, bending, or welding.
For the cutting processes, sheet metal fabrication uses band, miter, and chop saws, as well as cutting torches. Band saws have specially hardened blades and a feed to ensure even cutting. Chop and miter saws are also used, which have an abrasive disk specifically made for cutting sheet metal (chop saws move up and down, while miter saws can cut at an angle). Cutting torches (which use flame and a stream of oxygen) are also used in sheet metal fabrication. They can cut large pieces of sheet metal without much effort.
Sheet metal fabrication also involves the use of hydraulic breaks and rolling machines, as well as oxy-acetylene torches, in its forming processes. With breaks, sheet metal fabrication is simplified as they help create bends at predetermined angles.
Rolling machines are also used in sheet metal fabrication to form sheet metal into rolls, creating a more finished product in a shape like a roll of paper towels. Straightening warped steel during sheet metal fabrication is accomplished with an Oxy-acetylene torch. With straightening, heat is applied to the metal in a slow, linear fashion.
Joining sheet metal often involves welding. After the sheet metal parts are formed, they are assembled and tack welded into place. Various welding techniques can be used in sheet metal fabrication to avoid warping or other visual defects. These include using a stout fixture, welding in a staggered manner, covering the metal with sand during the cooling process, and special straightening processes. Other joining technology includes rivet guns and brazing equipment.
Sheet metal fabrication is a very flexible process, so it can be used in most industries to create everything from components to automotive bodies. Some industries that rely on it include the aerospace, construction, automotive, HVAC, consumer goods, robotics, agricultural, electronics, and energy sectors, but that is far from an exhaustive list. That's because the need for industrial products from metal is everywhere, from housings to gears to containers.
Sheet metal fabrication is used when prototyping most electronic enclosures and component parts. It is an inexpensive process so that prototypes can be viewed and examined at a lower price, and any adjustments can be performed quickly and efficiently.
Sheet metal can be fabricated to produce small sheet metal parts like brackets or cable connectors. Steel, aluminum, stainless steel, and copper alloys are sturdy enough to hold larger metal or plastic pieces together without breaking. If metals with corrosion resistance such as stainless steel sheet metal or plated/coated components are used, they will not be vulnerable to water or corrosion damage.
Sheet metal can be used as a roofing material to make flashing for roofs and rain gutters. Inside buildings, ductwork and furnaces can be made from sheet metal. Sheet is also used in surgical and dental instruments, MRI scanners, surgical implants, and pins and plates to fix broken bones.
Metal is a strong and lasting material used in every industry. A product made from sheet metal is generally easier or faster, and therefore less expensive, to make than a product made from casting or additive manufacturing.
