Metal fabrication is the creation of

metal A metal (from Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. Metals are typicall ...

structures by cutting, bending and assembling processes. It is a value-added process involving the creation of machines, parts, and structures from various raw materials. Typically, a fabrication shop bids on a job, usually based on engineering drawings, and if awarded the contract, builds the product. Large fab shops employ a multitude of value-added processes, including welding, cutting, forming and machining. As with other manufacturing processes, both human labor and

automation Automation describes a wide range of technologies that reduce human intervention in processes, namely by predetermining decision criteria, subprocess relationships, and related actions, as well as embodying those predeterminations in machines ...

are commonly used. A fabricated product may be called a ''fabrication'', and shops specializing in this type of work are called ''fab shops''. The end products of other common types of metalworking, such as machining,

metal stamping Stamping (also known as pressing) is the process of placing flat sheet metal in either blank or coil form into a stamping press where a tool and die surface forms the metal into a net shape. Stamping includes a variety of sheet-metal forming ma ...

, forging, and

casting Casting is a manufacturing process in which a liquid material is usually poured into a mold, which contains a hollow cavity of the desired shape, and then allowed to solidify. The solidified part is also known as a ''casting'', which is ejected ...

, may be similar in shape and function, but those processes are not classified as fabrication.

Processes

*''Cutting'' is done by

saw A saw is a tool consisting of a tough blade, wire, or chain with a hard toothed edge. It is used to cut through material, very often wood, though sometimes metal or stone. The cut is made by placing the toothed edge against the material and mov ...

ing,

shearing Sheep shearing is the process by which the woollen fleece of a sheep is cut off. The person who removes the sheep's wool is called a '' shearer''. Typically each adult sheep is shorn once each year (a sheep may be said to have been "shorn" or ...

, or chiselling (all with manual and powered variants); torching with handheld torches (such as oxy-fuel torches or

plasma torch A plasma torch (also known as a plasma arc, plasma gun, plasma cutter, or plasmatron) is a device for generating a directed flow of plasma. The plasma jet can be used for applications including plasma cutting, plasma arc welding, plasma spra ...

es); and via numerical control (CNC) cutters (using a

laser A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". The fi ...

, mill bits, torch, or

water jet Water jet may refer to: * A jet of water under pressure, like in an ornamental fountain * Pump-jet, a marine propulsion mechanism for jetskis and other types of boats * Water jet cutter, a tool for cutting and the machining of engineering material ...

). *''Bending'' is done by hammering (manual or powered) or via

press brake A press brake is a machine used for bending sheet metal and metal plate, most commonly sheet metal. It forms predetermined bends by clamping the workpiece between a matching top tool and bottom die.Parker, Dana T. ''Building Victory: Aircraft Manuf ...

s, tube benders and similar tools. Modern metal fabricators use press brakes to

coin A coin is a small, flat (usually depending on the country or value), round piece of metal or plastic used primarily as a medium of exchange or legal tender. They are standardized in weight, and produced in large quantities at a mint in order t ...

or air-bend metal sheet into form. CNC-controlled backgauges use hard stops to position cut parts to place bend lines in specific positions. * ''Assembling'' (joining of pieces) is done by

welding Welding is a fabrication process that joins materials, usually metals or thermoplastics, by using high heat to melt the parts together and allowing them to cool, causing fusion. Welding is distinct from lower temperature techniques such as bra ...

, binding with adhesives,

rivet A rivet is a permanent mechanical fastener. Before being installed, a rivet consists of a smooth cylindrical shaft with a head on one end. The end opposite to the head is called the ''tail''. On installation, the rivet is placed in a punched ...

ing, threaded fasteners, or further bending in the form of crimped seams. Structural steel and

sheet metal Sheet metal is metal formed into thin, flat pieces, usually by an industrial process. Sheet metal is one of the fundamental forms used in metalworking, and it can be cut and bent into a variety of shapes. Thicknesses can vary significantly; ex ...

are the usual materials for fabrication; welding wire, flux and/or fasteners are used to join the cut pieces. Fabrication comprises or overlaps with various metalworking specialties: * Fabrication shops and machine shops have overlapping capabilities, but fabrication shops generally concentrate on metal preparation and assembly (as described above). Machine shops cut metal, but focus primarily on the machining of parts on

machine tool A machine tool is a machine for handling or machining metal or other rigid materials, usually by cutting, boring, grinding, shearing, or other forms of deformations. Machine tools employ some sort of tool that does the cutting or shaping. All ...

s. Some firms do both fab work and machining. *

Blacksmith A blacksmith is a metalsmith who creates objects primarily from wrought iron or steel, but sometimes from other metals, by forging the metal, using tools to hammer, bend, and cut (cf. tinsmith). Blacksmiths produce objects such as gates, gr ...

ing has always involved fabrication, although that term has not always been used. * Welder-produced products, often referred to as ''weldments'', are examples of fabrication. *

Boilermaker A boilermaker is a tradesperson who fabricates steel, iron, or copper into boilers and other large containers intended to hold hot gas or liquid, as well as maintains and repairs boilers and boiler systems.Bureau of Labor Statistics, US De ...

s originally specialized in fabricating

boiler A boiler is a closed vessel in which fluid (generally water) is heated. The fluid does not necessarily boil. The heated or vaporized fluid exits the boiler for use in various processes or heating applications, including water heating, centr ...

s, but the term is now used more broadly. * Millwrights originally specialized in setting up grain mills and saw mills, but now perform a wide range of fabrication. *

Ironworker An ironworker is a tradesman who works in the iron-working industry. Ironworkers assemble the structural framework in accordance with engineered drawings and install the metal support pieces for new buildings. They also repair and renovate o ...

s, also known as

steel erector An ironworker is a tradesman who works in the iron-working industry. Ironworkers assemble the structural framework in accordance with engineered drawings and install the metal support pieces for new buildings. They also repair and renovate o ...

s, also engage in fabrication. They often work with prefabricated segments, produced in fab shops, that are delivered to the site.

Raw materials

Standard metal fabrication materials are: *Plate metal *Formed and

expanded metal Expanded metal is a type of sheet metal which has been cut and stretched to form a regular pattern (often diamond-shaped) of metal mesh-like material. It is commonly used for fences and grates, and as metallic lath to support plaster or stucco. D ...

**Tube stock *Welding wire/welding rod *

Casting Casting is a manufacturing process in which a liquid material is usually poured into a mold, which contains a hollow cavity of the desired shape, and then allowed to solidify. The solidified part is also known as a ''casting'', which is ejected ...

Cutting and burning

A variety of tools are used to cut raw material. The most common cutting method is

. Special

band saw A bandsaw (also written band saw) is a power saw with a long, sharp blade consisting of a continuous band of toothed metal stretched between two or more wheels to cut material. They are used principally in woodworking, metalworking, and l ...

s for cutting metal have hardened blades and feed mechanisms for even cutting. Abrasive cut-off saws, also known as chop saws, are similar to miter saws but have a steel-cutting abrasive disks.

Cutting torch Principle of burn cutting Oxy-fuel welding (commonly called oxyacetylene welding, oxy welding, or gas welding in the United States) and oxy-fuel cutting are processes that use fuel gases (or liquid fuels such as gasoline or petrol, diesel, ...

es can cut large sections of steel with little effort. Burn tables are CNC (computer-operated) cutting torches, usually powered by natural gas. Plasma and laser cutting tables, and water jet cutters, are also common. Plate steel is loaded on the table and the parts are cut out as programmed. The support table consists of a grid of bars that can be replaced when worn. Higher-end burn tables may include CNC punch capability using a carousel of punches and taps. In fabrication of structural steel by plasma and laser cutting, robots move the cutting head in three dimensions around the cut material.

Forming

Forming converts flat sheet metal into 3-D parts by applying force without adding or removing material. The force must be great enough to change the metal's initial shape. Forming can be controlled with tools such as punches and dies. Machinery can regulate force magnitude and direction. Machine-based forming can combine forming and welding to produce lengths of fabricated sheeting (e.g. linear grating for water drainage). Most metallic materials, being at least somewhat ductile and capable of considerable permanent deformation without cracking or breaking, lend themselves particularly well to these techniques. Proper design and use of tools with machinery creates a repeatable form that can be used to create products for many industries, including jewelry, aerospace, automotive, construction, civil and architectural.

Machining

Machining is a specialized trade of removing material from a block of metal to make it a desired shape. Fab shops generally have some machining capability, using metal

lathes A lathe () is a machine tool that rotates a workpiece about an axis of rotation to perform various operations such as cutting, sanding, knurling, drilling, deformation, facing, and turning, with tools that are applied to the workpiece to cr ...

mills Mills is the plural form of mill, but may also refer to: As a name * Mills (surname), a common family name of English or Gaelic origin * Mills (given name) *Mills, a fictional British secret agent in a trilogy by writer Manning O'Brine Places Uni ...

, drills, and other portable machining tools. Most solid components, such as gears, bolts, screws and nuts, are machined.

Welding

Welding is the main focus of steel fabrication. Formed and machined parts are assembled and tack-welded in place, then rechecked for accuracy. If multiple weldments have been ordered, a fixture may be used to locate parts for welding. A welder then finishes the work according to engineering drawings (for detailed welding) or by their own experience and judgement (if no details are provided). Special measures may be needed to prevent or correct warping of weldments due to heat. These may include redesigning the piece to require less welding, employing staggered welding, using a stout fixture, covering the weldment in sand as it cools, and post-weld straightening. Straightening of warped steel weldments is done with an oxyacetylene torch. In this highly specialized work, heat is selectively applied to the steel in a slow, linear sweep, causing the steel to contract in the direction of the sweep as it cools. A highly skilled welder can remove significant warpage this way. Steel weldments are occasionally annealed in a low-temperature oven to relieve

residual stress In materials science and solid mechanics, residual stresses are stresses that remain in a solid material after the original cause of the stresses has been removed. Residual stress may be desirable or undesirable. For example, laser peening i ...

es. Such weldments, particularly those for engine blocks, may be line-bored after heat treatment. After the weldment has cooled, seams are usually ground clean, and the assembly can be

sandblasted Sandblasting, sometimes known as abrasive blasting, is the operation of forcibly propelling a stream of abrasive material against a surface under high pressure to smooth a rough surface, roughen a smooth surface, shape a surface or remove su ...

, primed and painted. Any additional manufacturing is then performed, and the finished product is inspected and shipped.

Specialties

Many fabrication shops offer specialty processes, including : *

Powder coating Powder coating is a type of coating that is applied as a free-flowing, dry Powder (substance), powder. Unlike conventional liquid paint which is delivered via an evaporating solvent, powder coating is typically applied electrostatically and then P ...

Powder metallurgy Powder metallurgy (PM) is a term covering a wide range of ways in which materials or components are made from metal powders. PM processes can reduce or eliminate the need for subtractive processes in manufacturing, lowering material losses and ...

Welding Welding is a fabrication process that joins materials, usually metals or thermoplastics, by using high heat to melt the parts together and allowing them to cool, causing fusion. Welding is distinct from lower temperature techniques such as bra ...

* Machining

References

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