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Custom Metal Fabricating
Metal Fabricating as an industrial term refers to building metal structures by cutting, bending, and assembling. The
cutting part of metal fabrication is via sawing, shearing, or chiseling (all with manual and powered variants);
torching with handheld torches (such as oxy-fuel torches or plasma torches); and via CNC cutters (using a laser,
torch, or water jet). The bending is via hammering (manual or powered) or via press brakes and similar tools. The
assembling (joining of the pieces) is via welding, binding with adhesives, riveting, threaded fasteners, or even
yet more bending in the form of a crimped seam. Structural steel and sheet metal are the usual starting materials
for metal fabrication, along with the welding wire, flux, and fasteners that will join the cut pieces. As with other
manufacturing processes, both human labor and automation are commonly used. The product resulting from (the process
of) metal fabrication may be called a fabrication. Shops that specialize in this type of metal work are called fab
shops. The end products of other common types of metalworking, such as machining, metal stamping, forging, and
casting, may be similar in shape and function, but those processes are not classified as metal fabrication.
Metal fabrication is the process of turning raw materials into machines for different industrial tasks. Usually these projects are bid on by different metal fabricating companies and are done on-site at the plant or construction site that needs the machines made. Some of the most common projects that are made through metal fabrication are stair handrails, loose parts of machines, building frames and heavy metal equipment necessary for building other things. Metal fabricating is a necessary part of large construction projects.
Metal Fabricating is a value added process that involves the construction of machines and structures from various
raw materials. A fab shop will bid on a job, usually based on the engineering drawings, and if awarded the contract
will build the product.
Metal Fabricating comprises or overlaps with various custom metal working specialties:
- Metal Fabricating shops and machine shops have overlapping capabilities, but metal fabrication shops
generally concentrate on metal preparation and assembly as described above. By comparison, machine shops also
cut metal, but they are more concerned with the machining of parts on machine tools. Firms that encompass both
fab work and machining are also common.
- Blacksmithing has always involved Metal Fabricating, although it was not always called by that name.
- The products produced by welders, which are often referred to as weldments, are an example of Metal
Fabricating.
- Similarly, millwrights originally specialized in setting up grain mills and saw mills, but today they may
be called upon for a broad range of Metal Fabricating work.
- Ironworkers, also known as steel erectors, also engage in Metal Fabricating. Often the Metal Fabricating for
structural work begin as prefabricated segments in a fab shop, then are moved to the site by truck, rail, or
barge, and finally are installed by erectors.
Metal Fabricating shops are employed by contractors, OEMs and VARs. Typical projects include; loose parts,
structural frames for buildings and heavy equipment, and hand railings and stairs for buildings.
Metal fabrication makes custom metal projects quickly and efficiently. Most metal fabricating projects are made on-site at the place where they are needed. The metalworking machines are brought onto the site, and the metal is formed to suit the needs of the engineers in charge of the larger project. The reason that an outsider makes the metal forms is due to the high cost of the equipment necessary to build the metal pieces. It is more cost effective to pay someone else to make the metal than for each construction company to have its own equipment.
Metal Fabricating may employ or contract out steel detailers to prepare shop drawings, if not provided by the
customer, which the fabricating shop will use for manufacturing. Manufacturing engineers will program CNC machines
as needed.
Metal fabricating is very important to the construction world. If there were no people to work with metal fabrication, many of the buildings and machines that we have today would not exist. Additionally if every contractor that built things had to do their own metal fabricating they would have to charge a lot more to build things just to pay for the cost of the materials and labor that it takes to fabricate metal.
Raw materials in Metal Fabricating
Standard raw materials used by metal fabricators are;
plate metal
formed and expanded metal
tube stock, CDSM
square stock
sectional metals (I beams, W beams, C-channel...)
welding wire
hardware
castings
fittings
Cutting and burning in Metal Fabricating
The raw material has to be cut to size. This is done with a variety of tools.
The most common way to cut material is by Shearing (metalworking);
Special band saws designed for cutting metal have hardened blades and a feed mechanism for even cutting. Abrasive cut-off saws, also known as chop saws, are similar to miter saws but with a steel cutting abrasive disk. Cutting torches can cut very large sections of steel with little effort.
Burn tables are CNC cutting torches, usually natural gas powered. Plasma and laser cutting tables, and Water jet cutters, are also common. Plate steel is loaded on a table and the parts are cut out as programmed. The support table is made of a grid of bars that can be replaced. Some very expensive burn tables also include CNC punch capability, with a carousel of different punches and taps. Metal Fabrication of structural steel by plasma and laser cutting introduces robots to move the cutting head in three dimensions around the material to be cut.
Machining in Metal Fabricating
Fabricating shops will generally have a limited machining capability including; metal lathes, mills, magnetic based drills along with other portable metal working tools.
Forming in Metal Fabricating
Hydraulic brake presses with v-dies are the most common method of forming metal. The cut plate is placed in the press and a v-shaped die is pressed a predetermined distance to bend the plate to the desired angle. Wing brakes and hand powered brakes are sometimes used.
Tube bending machines have specially shaped dies and mandrels to bend tubular sections without kinking them.
Rolling machines are used to form plate steel into a round section.
English Wheel or Wheeling Machines are used to form complex double curvature shapes using sheet metal.
Welding in Metal Fabricating
Welding is the main focus of steel fabrication. The formed and machined parts will be assembled and tack welded into place then re-checked for accuracy. A fixture may be used to locate parts for welding if multiple weldments have been ordered.
The welder then completes welding per the engineering drawings, if welding is detailed, or per his own judgment if no welding details are provided.
Special precautions may be needed to prevent warping of the weldment due to heat. These may include re-designing the weldment to use less weld, welding in a staggered fashion, using a stout fixture, covering the weldment in sand during cooling, and straightening operations after welding.
Straightening of warped steel weldments is done with an Oxy-acetylene torch and is somewhat of an art. Heat is selectively applied to the steel in a slow, linear sweep. The steel will have a net contraction, upon cooling, in the direction of the sweep. A highly skilled welder can remove significant warpage using this technique.
Steel weldments are occasionally annealed in a low temperature oven to relieve residual stresses.
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