Sheet metal

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Sheets of Nirosta stainless steel cover the Chrysler Building Chrysler Building detail.jpg
Sheets of Nirosta stainless steel cover the Chrysler Building
Microscopic close-up of mild steel sheet metal. Mild steel sheet metal close up.jpg
Microscopic close-up of mild steel sheet metal.

Sheet metal is metal formed by an industrial process into thin, flat pieces. Sheet metal is one of the fundamental forms used in metalworking and it can be cut and bent into a variety of shapes. Countless everyday objects are fabricated from sheet metal. Thicknesses can vary significantly; extremely thin sheets are considered foil or leaf, and pieces thicker than 6 mm (0.25 in) are considered plate steel or "structural steel."

Metal element, compound, or alloy that is a good conductor of both electricity and heat

A metal is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. Metals are typically malleable or ductile. A metal may be a chemical element such as iron, or an alloy such as stainless steel.

Metalworking production and processing of shaped workpieces made of metals

Metalworking is the process of working with metals to create individual parts, assemblies, or large-scale structures. The term covers a wide range of work from large ships and bridges to precise engine parts and delicate jewelry. It therefore includes a correspondingly wide range of skills, processes, and tools.

Foil (metal) very thin sheet metal, usually made by hammering or rolling

A foil is a very thin sheet of metal, usually made by hammering or rolling. Foils are most easily made with malleable metals, such as aluminium, copper, tin, and gold. Foils usually bend under their own weight and can be torn easily. The more malleable a metal, the thinner foil can be made with it. For example, aluminium foil is usually about 1/1000 inch (0.03 mm), whereas gold can be made into foil only a few atoms thick, called gold leaf. Extremely thin foil is called metal leaf. Leaf tears very easily and must be picked up with special brushes.

Contents

Sheet metal is available in flat pieces or coiled strips. The coils are formed by running a continuous sheet of metal through a roll slitter.

Roll slitting shearing operation

Roll slitting is a shearing operation that cuts a large roll of material into narrower rolls. There are two types of slitting: log slitting and rewind slitting. In log slitting the roll of material is treated as a whole and one or more slices are taken from it without an unrolling/re-reeling process. In rewind slitting the web is unwound and run through the machine, passing through knives or lasers, before being rewound on one or more shafts to form narrower rolls. The multiple narrower strips of material may be known as mults or pancakes if their diameter is much more than their width. For rewind slitting the machine used is called a slitter rewinder, a slitter or a slitting machine – these names are used interchangeably for the same machines. For particularly narrow and thin products, the pancakes become unstable, and then the rewind may be onto a bobbin-wound reel: the rewind bobbins are much wider than the slit width and the web oscillates across the reel as it is rewound. Apart from the stability benefit it is also then possible to put very long lengths,, onto one bobbin.

In most of the world, sheet metal thickness is consistently specified in millimeters. In the US, the thickness of sheet metal is commonly specified by a traditional, non-linear measure known as its gauge. The larger the gauge number, the thinner the metal. Commonly used steel sheet metal ranges from 30 gauge to about 7 gauge. Gauge differs between ferrous (iron based) metals and nonferrous metals such as aluminum or copper. Copper thickness, for example, is measured in ounces; representing the weight of copper contained in an area of one square foot. Parts manufactured from sheet metal must maintain a uniform thickness for ideal results. [1]

Iron Chemical element with atomic number 26

Iron is a chemical element with symbol Fe and atomic number 26. It is a metal, that belongs to the first transition series and group 8 of the periodic table. It is by mass the most common element on Earth, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust.

There are many different metals that can be made into sheet metal, such as aluminium, brass, copper, steel, tin, nickel and titanium. For decorative uses, some important sheet metals include silver, gold, and platinum (platinum sheet metal is also utilized as a catalyst.)

Aluminium Chemical element with atomic number 13

Aluminium is a chemical element with the symbol Al and atomic number 13. It is a silvery-white, soft, non-magnetic and ductile metal in the boron group. By mass, aluminium makes up about 8% of the Earth's crust; it is the third most abundant element after oxygen and silicon and the most abundant metal in the crust, though it is less common in the mantle below. The chief ore of aluminium is bauxite. Aluminium metal is so chemically reactive that native specimens are rare and limited to extreme reducing environments. Instead, it is found combined in over 270 different minerals.

Brass Alloy of copper and zinc

Brass is an alloy of copper and zinc, in proportions which can be varied to achieve varying mechanical and electrical properties. It is a substitutional alloy: atoms of the two constituents may replace each other within the same crystal structure. Bronze is an alloy also containing copper, but instead of zinc it has tin.

Copper Chemical element with atomic number 29

Copper is a chemical element with the symbol Cu and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish-orange color. Copper is used as a conductor of heat and electricity, as a building material, and as a constituent of various metal alloys, such as sterling silver used in jewelry, cupronickel used to make marine hardware and coins, and constantan used in strain gauges and thermocouples for temperature measurement.

Sheet metal is used in automobile and truck (lorry) bodies, airplane fuselages and wings, medical tables, roofs for buildings (architecture) and many other applications. Sheet metal of iron and other materials with high magnetic permeability, also known as laminated steel cores, has applications in transformers and electric machines. Historically, an important use of sheet metal was in plate armor worn by cavalry, and sheet metal continues to have many decorative uses, including in horse tack. Sheet metal workers are also known as "tin bashers" (or "tin knockers"), a name derived from the hammering of panel seams when installing tin roofs. [2] [3]

Permeability (electromagnetism) measure of the ability of a material to support the formation of a magnetic field within itself

In electromagnetism, permeability is the measure of the ability of a material to support the formation of a magnetic field within itself, otherwise known as distributed inductance in Transmission Line Theory. Hence, it is the degree of magnetization that a material obtains in response to an applied magnetic field. Magnetic permeability is typically represented by the (italicized) Greek letter µ. The term was coined in September 1885 by Oliver Heaviside. The reciprocal of magnetic permeability is magnetic reluctivity.

Transformer electrical device that transfers energy through electromagnetic induction

A transformer is a static electrical device that transfers electrical energy between two or more circuits. A varying current in one coil of the transformer produces a varying magnetic flux, which, in turn, induces a varying electromotive force across a second coil wound around the same core. Electrical energy can be transferred between the two coils, without a metallic connection between the two circuits. Faraday's law of induction discovered in 1831 described the induced voltage effect in any coil due to changing magnetic flux encircled by the coil.

In electrical engineering, electric machine is a general term for machines using electromagnetic forces, such as electric motors, electric generators, and others. They are electromechanical energy converters: an electric motor converts electricity to mechanical power while an electric generator converts mechanical power to electricity. The moving parts in a machine can be rotating or linear. Besides motors and generators, a third category often included is transformers, which although they do not have any moving parts are also energy converters, changing the voltage level of an alternating current.

History

Hand-hammered metal sheets have been used since ancient times for architectural purposes. Water-powered rolling mills replaced the manual process in the late 17th century. The process of flattening metal sheets required large rotating iron cylinders which pressed metal pieces into sheets. The metals suited for this were lead, copper, zinc, iron and later steel. Tin was often used to coat iron and steel sheets to prevent it from rusting. [4] This tin-coated sheet metal was called "tinplate." Sheet metals appeared in the United States in the 1870s, being used for shingle roofing, stamped ornamental ceilings and exterior facades. Sheet metal ceilings were only popularly known as "tin ceilings" later as manufacturers of the period did not use the term. The popularity of both shingles and ceilings encouraged widespread production. With further advances of steel sheet metal production in the 1890s, the promise of being cheap, durable, easy to install, lightweight and fireproof gave the middle-class a significant appetite for sheet metal products. It was not until the 1930s and WWII that metals became scarce and the sheet metal industry began to collapse. [5] However, some American companies, such as the W.F. Norman Corporation, were able to stay in business by making other products until Historic preservation projects aided the revival of ornamental sheet metal.

Tinplate consists of sheets of steel, coated with a thin layer of tin. Before the advent of cheap milled steel the backing metal was iron. While once more widely used, the primary use of tinplate now is the manufacture of tin cans.

Historic preservation preservation of items of historical significance

Historic preservation (US), heritage preservation or heritage conservation (UK), is an endeavour that seeks to preserve, conserve and protect buildings, objects, landscapes or other artifacts of historical significance. This term refers specifically to the preservation of the built environment, and not to preservation of, for example, primeval forests or wilderness.

Materials

Stainless steel

Grade 304 is the most common of the three grades. It offers good corrosion resistance while maintaining formability and weldability. Available finishes are #2B, #3, and #4. Grade 303 is not available in sheet form. [6]

Grade 316 possesses more corrosion resistance and strength at elevated temperatures than 304. It is commonly used for pumps, valves, chemical equipment, and marine applications. Available finishes are #2B, #3, and #4. [6]

Grade 410 is a heat treatable stainless steel, but it has a lower corrosion resistance than the other grades. It is commonly used in cutlery. The only available finish is dull. [6]

Grade 430 is popular grade, low cost alternative to series 300's grades. This is used when high corrosion resistance is not a primary criterion. Common grade for appliance products, often with a brushed finish.

Aluminium

Aluminum is also a popular metal used in sheet metal due to its flexibility, wide range of options, cost effectiveness, and other properties. [7] The four most common aluminium grades available as sheet metal are 1100-H14, 3003-H14, 5052-H32, and 6061-T6. [6] [8]

Grade 1100-H14 is commercially pure aluminium, highly chemical and weather resistant. It is ductile enough for deep drawing and weldable, but has low strength. It is commonly used in chemical processing equipment, light reflectors, and jewelry. [6]

Grade 3003-H14 is stronger than 1100, while maintaining the same formability and low cost. It is corrosion resistant and weldable. It is often used in stampings, spun and drawn parts, mail boxes, cabinets, tanks, and fan blades. [6]

Grade 5052-H32 is much stronger than 3003 while still maintaining good formability. It maintains high corrosion resistance and weldability. Common applications include electronic chassis, tanks, and pressure vessels. [6]

Grade 6061-T6 is a common heat-treated structural aluminium alloy. It is weldable, corrosion resistant, and stronger than 5052, but not as formable. It loses some of its strength when welded. [6] It is used in modern aircraft structures. [9]

Brass

Brass is an alloy of copper, which is widely used as a sheet metal. It has more strength, corrosion resistance and formability when compared to copper while retaining its conductivity.

In sheet hydroforming, variation in incoming sheet coil properties is a common problem for forming process, especially with materials for automotive applications. Even though incoming sheet coil may meet tensile test specifications, high rejection rate is often observed in production due to inconsistent material behavior. Thus there is a strong need for a discriminating method for testing incoming sheet material formability.The hydraulic sheet bulge test emulates biaxial deformation conditions commonly seen in production operations.

For Forming Limit curves (FLCs) of materials Aluminium, Mild steel and Brass.Theoretical analysis is carried out by deriving governing equations for determining of Equivalent stress and Equivalent strain based on the bulging to be spherical andTresca’s yield criterion with the associated flow rule. For experimentation Circular Grid Analysis is used.

Investigation of Forming Limit Curves of Various Sheet Materials Using Hydraulic Bulge Testing With Analytical, Experimental and FEA Techniques. Available from: https://www.researchgate.net/publication/321168677_Investigation_of_Forming_Limit_Curves_of_Various_Sheet_Materials_Using_Hydraulic_Bulge_Testing_With_Analytical_Experimental_and_FEA_Techniques.

Gauge

Use of gauge numbers to designate sheet metal thickness is discouraged by numerous international standards organizations. For example, ASTM states in specification ASTM A480-10a: "The use of gauge number is discouraged as being an archaic term of limited usefulness not having general agreement on meaning." [10]

Manufacturers' Standard Gauge for Sheet Steel is based on an average weight of 41.82 lb (18.96 kg) per square foot per inch thick. [11] Gauge is defined differently for ferrous (iron-based) and non-ferrous metals (e.g. aluminium and brass).

Standard sheet metal gauges [12]
GaugeUS standard [13] [14]
for sheet and plate
iron and steel
decimal inch (mm)
Steel [15]
inch (mm)
Galvanized steel
inch (mm)
Stainless steel
inch (mm)
Aluminium
inch (mm)
Zinc [15]
inch (mm)
00000000.5000 (12.70)..............................
0000000.4688 (11.91)..............................
000000.4375 (11.11)..............................
00000.4063 (10.32)..............................
0000.3750 (9.53)..............................
000.3438 (8.73)..............................
00.3125 (7.94)..............................
10.2813 (7.15)..............................
20.2656 (6.75)..............................
30.2500 (6.35)0.2391 (6.07)..................0.006 (0.15)
40.2344 (5.95)0.2242 (5.69)..................0.008 (0.20)
50.2188 (5.56)0.2092 (5.31)..................0.010 (0.25)
60.2031 (5.16)0.1943 (4.94)............0.162 (4.1)0.012 (0.30)
70.1875 (4.76)0.1793 (4.55)......0.1875 (4.76)0.1443 (3.67)0.014 (0.36)
80.1719 (4.37)0.1644 (4.18)0.1681 (4.27)0.1719 (4.37)0.1285 (3.26)0.016 (0.41)
90.1563 (3.97)0.1495 (3.80)0.1532 (3.89)0.1563 (3.97)0.1144 (2.91)0.018 (0.46)
100.1406 (3.57)0.1345 (3.42)0.1382 (3.51)0.1406 (3.57)0.1019 (2.59)0.020 (0.51)
110.1250 (3.18)0.1196 (3.04)0.1233 (3.13)0.1250 (3.18)0.0907 (2.30)0.024 (0.61)
120.1094 (2.78)0.1046 (2.66)0.1084 (2.75)0.1094 (2.78)0.0808 (2.05)0.028 (0.71)
130.0938 (2.38)0.0897 (2.28)0.0934 (2.37)0.094 (2.4)0.072 (1.8)0.032 (0.81)
140.0781 (1.98)0.0747 (1.90)0.0785 (1.99)0.0781 (1.98)0.0641 (1.63)0.036 (0.91)
150.0703 (1.79)0.0673 (1.71)0.0710 (1.80)0.07 (1.8)0.057 (1.4)0.040 (1.0)
160.0625 (1.59)0.0598 (1.52)0.0635 (1.61)0.0625 (1.59)0.0508 (1.29)0.045 (1.1)
170.0563 (1.43)0.0538 (1.37)0.0575 (1.46)0.056 (1.4)0.045 (1.1)0.050 (1.3)
180.0500 (1.27)0.0478 (1.21)0.0516 (1.31)0.0500 (1.27)0.0403 (1.02)0.055 (1.4)
190.0438 (1.11)0.0418 (1.06)0.0456 (1.16)0.044 (1.1)0.036 (0.91)0.060 (1.5)
200.0375 (0.95)0.0359 (0.91)0.0396 (1.01)0.0375 (0.95)0.0320 (0.81)0.070 (1.8)
210.0344 (0.87)0.0329 (0.84)0.0366 (0.93)0.034 (0.86)0.028 (0.71)0.080 (2.0)
220.0313 (0.80)0.0299 (0.76)0.0336 (0.85)0.031 (0.79)0.025 (0.64)0.090 (2.3)
230.0281 (0.71)0.0269 (0.68)0.0306 (0.78)0.028 (0.71)0.023 (0.58)0.100 (2.5)
240.0250 (0.64)0.0239 (0.61)0.0276 (0.70)0.025 (0.64)0.02 (0.51)0.125 (3.2)
250.0219 (0.56)0.0209 (0.53)0.0247 (0.63)0.022 (0.56)0.018 (0.46)......
260.0188 (0.48)0.0179 (0.45)0.0217 (0.55)0.019 (0.48)0.017 (0.43)......
270.0172 (0.44)0.0164 (0.42)0.0202 (0.51)0.017 (0.43)0.014 (0.36)......
280.0156 (0.40)0.0149 (0.38)0.0187 (0.47)0.016 (0.41)0.0126 (0.32)......
290.0141 (0.36)0.0135 (0.34)0.0172 (0.44)0.014 (0.36)0.0113 (0.29)......
300.0125 (0.32)0.0120 (0.30)0.0157 (0.40)0.013 (0.33)0.0100 (0.25)......
310.0109 (0.28)0.0105 (0.27)0.0142 (0.36)0.011 (0.28)0.0089 (0.23)......
320.0102 (0.26)0.0097 (0.25)........................
330.0094 (0.24)0.0090 (0.23)........................
340.0086 (0.22)0.0082 (0.21)........................
350.0078 (0.20)0.0075 (0.19)........................
360.0070 (0.18)0.0067 (0.17)........................
370.0066 (0.17)0.0064 (0.16)........................
380.0063 (0.16)0.0060 (0.15)........................

Tolerances

During the rolling process the rollers bow slightly, which results in the sheets being thinner on the edges. [6] The tolerances in the table and attachments reflect current manufacturing practices and commercial standards and are not representative of the Manufacturer's Standard Gauge, which has no inherent tolerances.

Steel sheet metal tolerances [6] [16]
GaugeNominal
[in (mm)]
Max
[in (mm)]
Min
[in (mm)]
100.1345 (3.42)0.1405 (3.57)0.1285 (3.26)
110.1196 (3.04)0.1256 (3.19)0.1136 (2.89)
120.1046 (2.66)0.1106 (2.81)0.0986 (2.50)
140.0747 (1.90)0.0797 (2.02)0.0697 (1.77)
160.0598 (1.52)0.0648 (1.65)0.0548 (1.39)
180.0478 (1.21)0.0518 (1.32)0.0438 (1.11)
200.0359 (0.91)0.0389 (0.99)0.0329 (0.84)
220.0299 (0.76)0.0329 (0.84)0.0269 (0.68)
240.0239 (0.61)0.0269 (0.68)0.0209 (0.53)
260.0179 (0.45)0.0199 (0.51)0.0159 (0.40)
280.0149 (0.38)0.0169 (0.43)0.0129 (0.33)
Aluminium sheet metal tolerances [6]
Thickness
[in (mm)]
Sheet width
36 (914.4)
[in (mm)]
48 (1,219)
[in (mm)]
0.018–0.028 (0.46–0.71)0.002 (0.051)0.0025 (0.064)
0.029–0.036 (0.74–0.91)0.002 (0.051)0.0025 (0.064)
0.037–0.045 (0.94–1.14)0.0025 (0.064)0.003 (0.076)
0.046–0.068 (1.2–1.7)0.003 (0.076)0.004 (0.10)
0.069–0.076 (1.8–1.9)0.003 (0.076)0.004 (0.10)
0.077–0.096 (2.0–2.4)0.0035 (0.089)0.004 (0.10)
0.097–0.108 (2.5–2.7)0.004 (0.10)0.005 (0.13)
0.109–0.125 (2.8–3.2)0.0045 (0.11)0.005 (0.13)
0.126–0.140 (3.2–3.6)0.0045 (0.11)0.005 (0.13)
0.141–0.172 (3.6–4.4)0.006 (0.15)0.008 (0.20)
0.173–0.203 (4.4–5.2)0.007 (0.18)0.010 (0.25)
0.204–0.249 (5.2–6.3)0.009 (0.23)0.011 (0.28)
Stainless steel sheet metal tolerances [6]
Thickness
[in (mm)]
Sheet width
36 (914.4)
[in (mm)]
48 (1,219)
[in (mm)]
0.017–0.030 (0.43–0.76)0.0015 (0.038)0.002 (0.051)
0.031–0.041 (0.79–1.04)0.002 (0.051)0.003 (0.076)
0.042–0.059 (1.1–1.5)0.003 (0.076)0.004 (0.10)
0.060–0.073 (1.5–1.9)0.003 (0.076)0.0045 (0.11)
0.074–0.084 (1.9–2.1)0.004 (0.10)0.0055 (0.14)
0.085–0.099 (2.2–2.5)0.004 (0.10)0.006 (0.15)
0.100–0.115 (2.5–2.9)0.005 (0.13)0.007 (0.18)
0.116–0.131 (2.9–3.3)0.005 (0.13)0.0075 (0.19)
0.132–0.146 (3.4–3.7)0.006 (0.15)0.009 (0.23)
0.147–0.187 (3.7–4.7)0.007 (0.18)0.0105 (0.27)

Forming processes

Bending

The equation for estimating the maximum bending force is,

,

where k is a factor taking into account several parameters including friction. T is the ultimate tensile strength of the metal. L and t are the length and thickness of the sheet metal, respectively. The variable W is the open width of a V-die or wiping die.

Curling

The curling process is used to form an edge on a ring. This process is used to remove sharp edges. It also increases the moment of inertia near the curled end. The flare/burr should be turned away from the die. It is used to curl a material of specific thickness. Tool steel is generally used due to the amount of wear done by operation.

Decambering

It is a metal working process of removing camber, the horizontal bend, from a strip shaped material. It may be done to a finite length section or coils. It resembles flattening of leveling process, but on a deformed edge.

Deep drawing

Example of deep drawn part Parts made by deep drawing - 20100630.jpg
Example of deep drawn part

Drawing is a forming process in which the metal is stretched over a form or die. [17] In deep drawing the depth of the part being made is more than half its diameter. Deep drawing is used for making automotive fuel tanks, kitchen sinks, two-piece aluminum cans, etc. Deep drawing is generally done in multiple steps called draw reductions. The greater the depth, the more reductions are required. Deep drawing may also be accomplished with fewer reductions by heating the workpiece, for example in sink manufacture.

In many cases, material is rolled at the mill in both directions to aid in deep drawing. This leads to a more uniform grain structure which limits tearing and is referred to as "draw quality" material.

Expanding

Expanding is a process of cutting or stamping slits in alternating pattern much like the stretcher bond in brickwork and then stretching the sheet open in accordion-like fashion. It is used in applications where air and water flow are desired as well as when light weight is desired at cost of a solid flat surface. A similar process is used in other materials such as paper to create a low cost packing paper with better supportive properties than flat paper alone.

Hemming and seaming

Hemming is a process of folding the edge of sheet metal onto itself to reinforce that edge.

Seaming is a process of folding two sheets of metal together to form a joint.

Hydroforming

Hydroforming is a process that is analogous to deep drawing, in that the part is formed by stretching the blank over a stationary die. The force required is generated by the direct application of extremely high hydrostatic pressure to the workpiece or to a bladder that is in contact with the workpiece, rather than by the movable part of a die in a mechanical or hydraulic press. Unlike deep drawing, hydroforming usually does not involve draw reductions—the piece is formed in a single step.

Incremental sheet forming

Incremental sheet forming or ISF forming process is basically sheet metal working or sheet metal forming process. In this case, sheet is formed into final shape by a series of processes in which small incremental deformation can be done in each series.

Ironing

Ironing is a sheet metal working or sheet metal forming process. It uniformly thins the workpiece in a specific area. This is a very useful process. It is used to produce a uniform wall thickness part with a high height-to-diameter ratio. It is used in making aluminium beverage cans.

Laser cutting

Sheet metal can be cut in various ways, from hand tools called tin snips up to very large powered shears. With the advances in technology, sheet metal cutting has turned to computers for precise cutting. Many sheet metal cutting operations are based on computer numerically controlled (CNC) laser cutting or multi-tool CNC punch press.

CNC laser involves moving a lens assembly carrying a beam of laser light over the surface of the metal. Oxygen, nitrogen or air is fed through the same nozzle from which the laser beam exits. The metal is heated and burnt by the laser beam, cutting the metal sheet. The quality of the edge can be mirror smooth and a precision of around 0.1 mm (0.0039 in) can be obtained. Cutting speeds on thin 1.2 mm (0.047 in) sheet can be as high as 25 m (82 ft) per minute. Most laser cutting systems use a CO2 based laser source with a wavelength of around 10  µm; some more recent systems use a YAG based laser with a wavelength of around 1 µm.

Photochemical machining

Photochemical machining, also known as photo etching, is a tightly controlled corrosion process which is used to produce complex metal parts from sheet metal with very fine detail. The photo etching process involves photo sensitive polymer being applied to a raw metal sheet. Using CAD designed photo-tools as stencils, the metal is exposed to UV light to leave a design pattern, which is developed and etched from the metal sheet.

Perforating

Perforating is a cutting process that punches multiple small holes close together in a flat workpiece. Perforated sheet metal is used to make a wide variety of surface cutting tools, such as the surform.

Press brake forming

Forming metal on a pressbrake Biegeanimation 3D.gif
Forming metal on a pressbrake

This is a form of bending used to produce long, thin sheet metal parts. The machine that bends the metal is called a press brake. The lower part of the press contains a V-shaped groove called the die. The upper part of the press contains a punch that presses the sheet metal down into the v-shaped die, causing it to bend. [18] There are several techniques used, but the most common modern method is "air bending". Here, the die has a sharper angle than the required bend (typically 85 degrees for a 90 degree bend) and the upper tool is precisely controlled in its stroke to push the metal down the required amount to bend it through 90 degrees. Typically, a general purpose machine has an available bending force of around 25 tonnes per metre of length. The opening width of the lower die is typically 8 to 10 times the thickness of the metal to be bent (for example, 5 mm material could be bent in a 40 mm die). The inner radius of the bend formed in the metal is determined not by the radius of the upper tool, but by the lower die width. Typically, the inner radius is equal to 1/6 of the V-width used in the forming process.

The press usually has some sort of back gauge to position depth of the bend along the workpiece. The backgauge can be computer controlled to allow the operator to make a series of bends in a component to a high degree of accuracy. Simple machines control only the backstop, more advanced machines control the position and angle of the stop, its height and the position of the two reference pegs used to locate the material. The machine can also record the exact position and pressure required for each bending operation to allow the operator to achieve a perfect 90 degree bend across a variety of operations on the part.

The picture shown is air bending. Press brake bending is a different machine. But similar.

Punching

Punching is performed by placing the sheet of metal stock between a punch and a die mounted in a press. The punch and die are made of hardened steel and are the same shape. The punch is sized to be a very close fit in the die. The press pushes the punch against and into the die with enough force to cut a hole in the stock. In some cases the punch and die "nest" together to create a depression in the stock. In progressive stamping, a coil of stock is fed into a long die/punch set with many stages. Multiple simple shaped holes may be produced in one stage, but complex holes are created in multiple stages. In the final stage, the part is punched free from the "web".

A typical CNC turret punch has a choice of up to 60 tools in a "turret" that can be rotated to bring any tool to the punching position. A simple shape (e.g. a square, circle, or hexagon) is cut directly from the sheet. A complex shape can be cut out by making many square or rounded cuts around the perimeter. A punch is less flexible than a laser for cutting compound shapes, but faster for repetitive shapes (for example, the grille of an air-conditioning unit). A CNC punch can achieve 600 strokes per minute.

A typical component (such as the side of a computer case) can be cut to high precision from a blank sheet in under 15 seconds by either a press or a laser CNC machine..

Roll forming

A continuous bending operation for producing open profiles or welded tubes with long lengths or in large quantities.

Rolling

Bending sheet metal with rollers Rundwalzen.png
Bending sheet metal with rollers

[19]

Rolling is metal working or metal forming process. In this method, stock is pass through one or more pair of rolls to reduce thickness. It is used to make thickness uniform. It is classified according to its temperature of rolling.

1.Hot rolling: in this temperature is above recrystallisation temperature.

2. Cold rolling: In this temperature is below recrystallisation temperature.

3. Warm rolling: In this temperature is used is in between Hot rolling and cold rolling.

Spinning

Spinning is used to make tubular (axis-symmetric) parts by fixing a piece of sheet stock to a rotating form (mandrel). Rollers or rigid tools press the stock against the form, stretching it until the stock takes the shape of the form. Spinning is used to make rocket motor casings, missile nose cones, satellite dishes and metal kitchen funnels.

Stamping

Stamping includes a variety of operations such as punching, blanking, embossing, bending, flanging, and coining; simple or complex shapes can be formed at high production rates; tooling and equipment costs can be high, but labor costs are low.

Alternatively, the related techniques repoussé and chasing have low tooling and equipment costs, but high labor costs.

Water jet cutting

A water jet cutter, also known as a waterjet, is a tool capable of a controlled erosion into metal or other materials using a jet of water at high velocity and pressure, or a mixture of water and an abrasive substance.

Wheeling

[20]

The process of using an English wheel is called wheeling. It is basically a metal working or metal forming process. An English wheel is used by a craftsperson to form compound curves from a flat sheet of metal of aluminium or steel. It is costly, as highly skilled labour is required. It can produce different panels by the same method. A stamping press is used for high numbers in production.

Fasteners

Fasteners that are commonly used on sheet metal include:

See also

Related Research Articles

Spot welding capacitor discharge

Resistance spot welding (RSW) is a process in which contacting metal surface points are joined by the heat obtained from resistance to electric current. It is a subset of electric resistance welding.

Laser cutting technology that uses a laser to cut materials

Laser cutting is a technology that uses a laser to cut materials, and is typically used for industrial manufacturing applications, but is also starting to be used by schools, small businesses, and hobbyists. Laser cutting works by directing the output of a high-power laser most commonly through optics. The [laser optics] and CNC are used to direct the material or the laser beam generated. A commercial laser for cutting materials involved a motion control system to follow a CNC or G-code of the pattern to be cut onto the material. The focused laser beam is directed at the material, which then either melts, burns, vaporizes away, or is blown away by a jet of gas, leaving an edge with a high-quality surface finish. Industrial laser cutters are used to cut flat-sheet material as well as structural and piping materials.

Brake (sheet metal bending) machine for bending sheet metal

A brake is a metalworking machine that allows the bending of sheet metal. A cornice brake only allows for simple bends and creases, while a box-and-pan brake also allows one to form box and pan shapes. It is also known as a bending machine or bending brake or in Britain as a sheet metal folder or just a folder.


A die is a specialized tool used in manufacturing industries to cut or shape material mostly using a press. Like molds, dies are generally customized to the item they are used to create. Products made with dies range from simple paper clips to complex pieces used in advanced technology.

Metal fabrication

Metal fabrication is the creation of metal 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.

Vacuum forming

Vacuum forming is a simplified version of thermoforming, where a sheet of plastic is heated to a forming temperature, stretched onto a single-surface mold, and forced against the mold by a vacuum. This process can be used to form plastic into permanent objects such as turnpike signs and protective covers. Normally draft angles are present in the design of the mold to ease removal of the formed plastic part from the mold.

Plasma 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 conductive metals may be cut as well. Plasma cutting is often used in fabrication shops, automotive repair and restoration, industrial construction, and salvage and scrapping operations. Due to the high speed and precision cuts combined with low cost, plasma cutting sees widespread use from large-scale industrial CNC applications down to small hobbyist shops.

Galling

Galling is a form of wear caused by adhesion between sliding surfaces. When a material galls, some of it is pulled with the contacting surface, especially if there is a large amount of force compressing the surfaces together. Galling is caused by a combination of friction and adhesion between the surfaces, followed by slipping and tearing of crystal structure beneath the surface. This will generally leave some material stuck or even friction welded to the adjacent surface, whereas the galled material may appear gouged with balled-up or torn lumps of material stuck to its surface.

Hydroforming

Hydroforming is a cost-effective way of shaping ductile metals such as aluminium, brass, low alloy steel, and stainless steel into lightweight, structurally stiff and strong pieces. One of the largest applications of hydroforming is the automotive industry, which makes use of the complex shapes made possible by hydroforming to produce stronger, lighter, and more rigid unibody structures for vehicles. This technique is particularly popular with the high-end sports car industry and is also frequently employed in the shaping of aluminium tubes for bicycle frames.

Punching metal forming process that uses a punch press to force a tool, called a punch, through the workpiece to create a hole via shearing

Punching is a forming process that uses a punch press to force a tool, called a punch, through the workpiece to create a hole via shearing. Punching is applicable to a wide variety of materials that come in sheet form, including sheet metal, paper, vulcanized fibre and some forms of plastic sheet. The punch often passes through the work into a die. A scrap slug from the hole is deposited into the die in the process. Depending on the material being punched this slug may be recycled and reused or discarded.

Rolling (metalworking) metalworking process

In metalworking, rolling is a metal forming process in which metal stock is passed through one or more pairs of rolls to reduce the thickness and to make the thickness uniform. The concept is similar to the rolling of dough. Rolling is classified according to the temperature of the metal rolled. If the temperature of the metal is above its recrystallization temperature, then the process is known as hot rolling. If the temperature of the metal is below its recrystallization temperature, the process is known as cold rolling. In terms of usage, hot rolling processes more tonnage than any other manufacturing process, and cold rolling processes the most tonnage out of all cold working processes. Roll stands holding pairs of rolls are grouped together into rolling mills that can quickly process metal, typically steel, into products such as structural steel, bar stock, and rails. Most steel mills have rolling mill divisions that convert the semi-finished casting products into finished products.

Electrical steel

Electrical steel is an iron alloy tailored to produce specific magnetic properties: small hysteresis area resulting in low power loss per cycle, low core loss, and high permeability.

Bending (metalworking) metalworking term

Bending is a manufacturing process that produces a V-shape, U-shape, or channel shape along a straight axis in ductile materials, most commonly sheet metal. Commonly used equipment include box and pan brakes, brake presses, and other specialized machine presses. Typical products that are made like this are boxes such as electrical enclosures and rectangular ductwork.

Notching

Notching is a metal-cutting process used on sheet-metal or thin bar-stock, sometimes on angle sections or tube. A shearing or punching process is used in a press, so as to cut vertically down and perpendicular to the surface, working from the edge of a work-piece. Sometimes the goal is merely the notch itself, but usually this is a precursor to some other process: such as bending a corner in sheet or joining two tubes at a tee joint, notching one to fit closely to the other.

Photochemical machining

Photochemical machining (PCM), also known as photochemical milling or photo etching, is a chemical milling process used to fabricate sheet metal components using a photoresist and etchants to corrosively machine away selected areas. This process emerged in the 1960s as an offshoot of the printed circuit board industry. Photo etching can produce highly complex parts with very fine detail accurately and economically.

Shearing, also known as die cutting, is a process which cuts stock without the formation of chips or the use of burning or melting. Strictly speaking, if the cutting blades are straight the process is called shearing; if the cutting blades are curved then they are shearing-type operations. The most commonly sheared materials are in the form of sheet metal or plates, however rods can also be sheared. Shearing-type operations include: blanking, piercing, roll slitting, and trimming. It is used in metalworking and also with paper and plastics.

Roll forming

Roll forming, also spelled roll-forming or rollforming, is a type of rolling involving the continuous bending of a long strip of sheet metal into a desired cross-section. The strip passes through sets of rolls mounted on consecutive stands, each set performing only an incremental part of the bend, until the desired cross-section (profile) is obtained. Roll forming is ideal for producing constant-profile parts with long lengths and in large quantities.

Metal spinning

Metal spinning, also known as spin forming or spinning or metal turning most commonly, is a metalworking process by which a disc or tube of metal is rotated at high speed and formed into an axially symmetric part. Spinning can be performed by hand or by a CNC lathe.

Turret punch

A turret punch or turret press is a type of punch press used for metal forming by punching.

References

  1. "Design Guide: Sheet Metal Fabrication" (PDF). xometry.com.
  2. Lodhi, Veerendra Singh; Jain, Prof. A.K. (30 April 2014). "A Review of Experimental Study of Spring Back Effect of Aluminum Sheet Metal". International Journal of Engineering Research and Science & Technology (IJERST). College Jabalpur (M P), India: Academia.edu. 3 (4): 2. doi:10.7763/IJET. ISSN   2277-9655. Archived from the original on 20 February 2017. Retrieved 14 July 2015.
  3. Green, Archie (1993). Wobblies, pile butts, and other heroes : laborlore explorations. Urbana u.a.: Univ. of Illinois Press. p. 20. ISBN   9780252019630. Archived from the original on 14 July 2015. Retrieved 14 July 2015.
  4. Simpson, Pamela H. (1999). Cheap, Quick, & Easy: Imitative Architectural Materials, 1870-1930. Knoxville: University of Tennessee Press. p. 31. ISBN   978-1-62190-157-0.
  5. Staveteig, Kaaren R. "Historic Decorative Metal Ceilings and Walls: Use, Repair, and Replacement" (PDF). PRESERVATIONBRIEFS (49): 1–3. Retrieved March 20, 2019.
  6. 1 2 3 4 5 6 7 8 9 10 11 12 "Sheet metal material". precisionsheetmetal.com. Archived from the original on 2009-06-15.
  7. "Sustainability of Aluminium in Buildings" (PDF). European Aluminium Association. Retrieved 20 June 2013.
  8. "Central Steel & Wire Company Catalog" (2006–2008 ed.): 151.
  9. All Metal Construction Made Easy Archived 2012-02-18 at the Wayback Machine
  10. "ASTM A480/A480M-13b Standard Specification for General Requirements for Flat-Rolled Stainless and Heat-Resisting Steel Plate, Sheet, and Strip". ASTM International. Archived from the original on 2014-02-22.
  11. Oberg, p. 2522.
  12. Rowlett, Ross (26 July 2002). "Sheet Metal Thickness Gauges". University of North Carolina at Chapel Hill. Archived from the original on 19 July 2013. Retrieved 21 June 2013.
  13. Oberg, p. 387.
  14. 15 U.S.C.   § 206 : Standard gauge for sheet and plate iron and steel
  15. 1 2 Oberg, p. 2502.
  16. "ASTM-AISI Thickness Tolerance Ranges" (PDF). CoyoteSteel.com. Archived (PDF) from the original on 5 August 2012. Retrieved 20 June 2013.
  17. Parker, pp. 20, 85
  18. Parker, pp. 29, 83
  19. Parker, p. 115
  20. Parker, p. 89
  21. Parker, p. 70
  22. Parker, pp. 17, 22, 29–30, 117

Bibliography