Reshaping a metal workpiece via deformation
In metalworking, forming is the fashioning of metal parts and objects through mechanical deformation; the workpiece is reshaped without adding or removing material, and its mass remains unchanged. Forming operates on the materials science principle of plastic deformation, where the physical shape of a material is permanently deformed.
Characteristics
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Metal forming tends to have more uniform characteristics across its subprocesses than its contemporary processes, cutting and joining.
On the industrial scale, forming is characterized by:
- Very high loads and stresses required, between 50 and
2500 N/mm2
(7-360 ksi
- Large, heavy, and expensive machinery in order to accommodate such high stresses and loads
- Production runs with many parts, to maximize the economy of production and compensate for the expense of the machine tools
Forming processes
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Forming processes tend to be categorised by differences in effective stresses. These categories and descriptions are highly simplified, since the stresses operating at a local level in any given process are very complex and may involve many varieties of stresses operating simultaneously, or it may involve stresses which change over the course of the operation.
Compressive forming involves those processes where the primary means of plastic deformation is uni- or multiaxial compressive loading.
- Rolling, where the material is passed through a pair of rollers
- Extrusion, where the material is pushed through an orifice
- Die forming, where the material is stamped by a press around or onto a die
- Forging, where the material is shaped by localized compressive forces
- Indenting, where a tool is pressed into the workpiece
Tensile forming
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Tensile forming involves those processes where the primary means of plastic deformation is uni- or multiaxial tensile stress.
- Stretching, where a tensile load is applied along the longitudinal axis of the workpiece
- Expanding, where the circumference of a hollow body is increased by tangential loading
- Recessing, where depressions and holes are formed through tensile loading
Combined tensile and compressive forming
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This category of forming processes involves those operations where the primary means of plastic deformation involves both tensile stresses and compressive loads.
Bending
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This category of forming processes involves those operations where the primary means of plastic deformation is a bending load.
Shearing
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This category of forming processes involves those operations where the primary means of plastic deformation is a shearing load.
Notes
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References
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- Lange, Kurt, ed. (1985). Handbook of Metal Forming. McGraw-Hill, Inc. on behalf of the Society of Manufacturing Engineers. ISBN 0872634574.
See also
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To understand how to best design and otherwise work with sheet metal, you have to look at the sheet metal manufacturing process.
In industrial manufacturing, sheet metal is cut and mended into various shapes from thin, flat pieces. A wide selection of finished products require sheet metal -- from military furniture to train exteriors -- so it’s important to understand how us metal fabricators do what we do!
The Sheet Metal Manufacturing Process
1. Sheet Metal Grades and Materials
This section will outline:
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Sheet metal materials
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Sheet metal grades
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Sample grades
Sheet metal materials can include stainless steel or aluminum. These come in various grades, with 304 stainless steel being the most common. Other grades can include 410 and 316 stainless steel (also called marine grade).
With aluminum, the grades look a bit different. Aluminum has grades like 1100-H14 or 3003-H14. Each number will be stronger than the next and may require different types of equipment and machinery to work with them.
2. Sheet Metal Thickness and Types
This section will explore:
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Sheet metal thickness
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Flat pieces of metal
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Coiled strips of metal
Sheet metal thickness is measured in gauge. The higher the gauge number, the thinner the piece of metal. Sheet metal can come in foil, too. It can come in a flat piece or in a coiled strip.
When it’s flat, the sheet metal is run through a roll slitter continuously to achieve this effect. Sheet metal coils can range in gauge from 7-20 gauge, and it’s commonly used with airplanes, in commercial roofing, or in the body of a car that’s being assembled.
(Related: Free sheet metal size charts for aluminum, stainless, galvanized and regular steel)
3. The Forming Process – Bending and Roll Forming
The next section will explore:
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A sheet metal press
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Press brakes
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Metal bending
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Roll forming
In order to work with sheet metal, it has to go through a press. The parts will be formed in the center of two different dies. The first die, the one that’s at the top, is what’s called the punch. Hence, when sheet metal is made, it’s cold.
To form it, it can be bent. When bending is done, a small section of the metal will be bent, and the dies will guide the sheet metal in this process. This is a sample bend.
The machinery works with press brakes -- these can help with guiding longer pieces of metal. By repeatedly bending the metal, it can eventually be transformed into its required shape as rollers help to guide it along and shape it.
For being to take place when the metal is roll formed, the sheet metal section that’s fed into the machinery will work with various rolling stations.
These will use a roller die that’s on top of the sheet metal; another die is on the bottom of the sheet. The rollers can be used at different angles. This will eventually change the shape of the sheet metal. As it passes through the roller die, it will start to bend and transform into your preferred shape.
4. Deep Drawing and Spinning
The next steps will explain:
When a particular shape is required of a section of sheet metal, it has to go through a spinning process. To achieve this, the sheet metal will be turned at high speeds while it is pressed against two stocks. The first is considered a headstock spindle. The other is a tailstock that will support the piece of metal while it’s going through the spinning process. Special tools are required to exert force on the metal. The pressure that’s applied help it achieve its required shape.
If, on the other hand, a deep drawing method is going to be applied, the sheet metal will not be clamped down for spinning. Instead, it will be put into a die in a stage that is referred to as cupping. Force will be applied to the piece of sheet metal by using a pressure pad. This will hold the sheet metal in place for the punch to move into an area and create an impression or blank in the sheet metal cavity.
The sheet metal will be bent and a cupping will form while the pressure pad works simultaneously to ensure there are no wrinkles showing on the unaffected areas of the sheet metal. This is a common process in metal fabrication for industrial enclosures that can help give sheet metal indentations.
Final Thoughts
As you can tell there are various ways to transform sheet metal for basic designs. If you have further questions about what to expect in the sheet metal manufacturing process, it’s best to get them answered before you sign on with a metal fabricator. Some vendors offer free consultations or will at least answer a question or two over the phone.