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Metal fabrication is the creation of
metal A metal (from ancient Greek, Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electrical resistivity and conductivity, e ...
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 drawing An engineering drawing is a type of technical drawing that is used to convey information about an object. A common use is to specify the geometry necessary for the construction of a component and is called a detail drawing. Usually, a number o ...
s, 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,
forging Forging is a manufacturing process involving the shaping of metal using localized compressive forces. The blows are delivered with a hammer (often a power hammer) or a die. Forging is often classified according to the temperature at which ...
, 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 ejecte ...
, may be similar in shape and function, but those processes are not classified as fabrication.


Processes

*''Cutting'' is done by sawing,
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" o ...
, or chiselling (all with
manual Manual may refer to: Instructions * User guide * Owner's manual An owner's manual (also called an instruction manual or a user guide) is an instructional book or booklet that is supplied with almost all technologically advanced consumer ...
and powered variants); torching with handheld torches (such as oxy-fuel torches or plasma torches); and via
numerical control Numerical control (also computer numerical control, and commonly called CNC) is the automated control of machining tools (such as drills, lathes, mills, grinders, routers and 3D printers) by means of a computer. A CNC machine processes ...
(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 ...
, mill bits, torch, or water jet). *''Bending'' is done by hammering (manual or powered) or via press brakes, 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 ...
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 b ...
, binding with
adhesive Adhesive, also known as glue, cement, mucilage, or paste, is any non-metallic substance applied to one or both surfaces of two separate items that binds them together and resists their separation. The use of adhesives offers certain advant ...
s,
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 Thread may refer to: Objects * Thread (yarn), a kind of thin yarn used for sewing ** Thread (unit of measurement), a cotton yarn measure * Screw thread, a helical ridge on a cylindrical fastener Arts and entertainment * ''Thread'' (film), 2016 ...
, or further bending in the form of crimped seams.
Structural steel Structural steel is a category of steel used for making construction materials in a variety of shapes. Many structural steel shapes take the form of an elongated beam having a profile of a specific cross section. Structural steel shapes, si ...
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. Al ...
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. * Boilermakers 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, central ...
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. * Ironworkers, also known as steel erectors, 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. ...
**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 ejecte ...


Cutting and burning

A variety of tools are used to cut raw material. The most common cutting method is
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" o ...
. Special band saws 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 Laser cutting is a technology that uses a laser to vaporize materials, resulting in a cut edge. While typically used for industrial manufacturing applications, it is now used by schools, small businesses, architecture, and hobbyists. Laser cut ...
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 Plasma cutting is a process that cuts through electrically conductive materials by means of an accelerated jet of hot plasma. Typical materials cut with a plasma torch include steel, stainless steel, aluminum, brass and copper, although other ...
, 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, mills,
drill A drill is a tool used for making round holes or driving fasteners. It is fitted with a bit, either a drill or driver chuck. Hand-operated types are dramatically decreasing in popularity and cordless battery-powered ones proliferating due to ...
s, 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 stresses. 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, 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 : *
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 ejecte ...
* Powder coating * Powder metallurgy *
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 b ...
* Machining


See also

*
Contract manufacturing A contract manufacturer (CM) is a manufacturer that contracts with a firm for components or products (in which case it is a turnkey supplier). It is a form of outsourcing. A contract manufacturer performing packaging operations is called copacker o ...
*
Electrical discharge machining Electrical discharge machining (EDM), also known as spark machining, spark eroding, die sinking, wire burning or wire erosion, is a metal fabrication process whereby a desired shape is obtained by using electrical discharges (sparks). Material i ...
* Form, fit and function *
Interchangeable parts Interchangeable parts are parts (components) that are identical for practical purposes. They are made to specifications that ensure that they are so nearly identical that they will fit into any assembly of the same type. One such part can freely r ...
*
Manufacturing engineering Manufacturing engineering or production engineering is a branch of professional engineering that shares many common concepts and ideas with other fields of engineering such as mechanical, chemical, electrical, and industrial engineering. Manufa ...


References

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