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 typi ...
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 whi ...
, and
casting, may be similar in shape and function, but those processes are not classified as fabrication.
Processes
*''Cutting'' is done by
sawing,
shearing, or
chiselling (all with
manual and
powered variants); torching with handheld torches (such as
oxy-fuel torches or
plasma torches); 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 firs ...
,
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 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 orde ...
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 br ...
, 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
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, siz ...
and
sheet metal 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, other metals, by forging the metal, using tools to hammer, bend, and cut (cf. tinsmith). Blacksmiths produce objects such ...
ing has always involved fabrication, although that term has not always been used.
*
Welder
In a broad sense, a welder is anyone, amateur or professional, who uses welding equipment, perhaps especially one who uses such equipment fairly often. In a narrower sense, a welder is a tradesperson who specializes in fusing materials together ...
-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, centr ...
s, but the term is now used more broadly.
*
Millwright
A millwright is a craftsperson or skilled tradesperson who installs, dismantles, maintains, repairs, reassembles, and moves machinery in factories, power plants, and construction sites.
The term ''millwright'' (also known as ''industrial mecha ...
s 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
Cutting and burning
A variety of tools are used to cut raw material. The most common cutting method is
shearing.
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 torches 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,
mills,
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
Warp, warped or warping may refer to:
Arts and entertainment Books and comics
* WaRP Graphics, an alternative comics publisher
* ''Warp'' (First Comics), comic book series published by First Comics based on the play ''Warp!''
* Warp (comics), a ...
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
file:Brennschneiden.svg, 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 gas ...
. 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
*
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 br ...
*
Machining
See also
*
Contract manufacturing
*
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
*
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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