The history of metal fabrication techniques, alternatively known as metalworking, dates back to ancient times with the development of civilisation largely being down to the discovery and deformation of metals. To begin with, these metals were used to build tools and weapons long before being used for the advancement of agriculture, transport and art.
Today metal fabrication is found in a wide array of industries such as construction, mining, aerospace, medical and rail, to name a few. Metal fabrication itself has evolved drastically, with a number of techniques being incorporated to make the process more efficient and continuously improve the quality of the end product.
Today, laser cutting is a common practice used in varying industries. How laser cutting works is through the use of an intense beam of infrared light which is generated by a laser. Depending on the kind of laser, the beam is focused on the surface with a focusing lens or fibre-optic cable, for example.
Through the continuous advancements of laser cutting, it can be said these are the most effective and quickest ways to cut sheet metal but there are other methods used within the industry.
Plasma cutting is one of these methods and is a process which cuts through materials such as steel, stainless steel, brass, aluminium and copper with an accelerated jet of hot plasma. There are debates around which is more beneficial laser or plasma cutters, at ADS however, we have recently invested in one of the more modern fiber lasers due to the added benefits we have proven these possess over plasma.
An older method which is not so common today, is water jet cutting. This method dates back to the mid-1800s when it was used in hydraulic mining before narrow jets of water were used as an industrial cutting device sometime in the 1930s.
Through the continuous advancements of laser cutting, it can be said these are the most effective and quickest ways to cut sheet metal.
Shearing works with the edges of two knives, one fixed and the other moving vertically, cutting a piece of metal in a similar fashion to how hand shears work.
Typically, one of the blades will remain stationary while the other is pressed upwards or downwards through the workpiece by slightly piercing the sheet metal which causes a tear on either side of the material known as the slip plane. Through this action, a long cut on a piece of metal is achieved, similar to how hand shears cut through paper.
The shear angle or alternatively, the blade rake, is the angle at which the upper and lower blades are aligned with each other. The distance between the upper and lower blades is known as the blade or knife clearance, knife distance is essential for proper shearing and is modified for different material thicknesses and strengths.
Shearing is a fabrication technique used to cut straight lines on a flat metal stock, with a number of types being deployed such as Alligator shear, Guillotine and Tin Snips to name a few. A broadly similar effect can be achieved through the use of a plasma torch or with a laser to “sheer cut”.
Machining, or metal cutting, is a technique which removes unwanted material from a block or sheet of metal with, principally, either a milling, drilling or turning tool. Machining dates back to the Egyptian era when a “bowstring” was used to drill holes out of stones with metal cutting first being introduced around the mid 19th Century.
Milling is one of the more common methods of machining and is the process of using rotary cutters to remove metal. This is achieved by advancing a cutter into a workpiece in varying directions and can either be done manually or via a CNC machine.
Drilling is a method used to create a round hole of varying sizes within a workpiece by forcing a rotating, multi-point cutting tool through it and is a method commonly used within metalworking, woodworking and construction, among other things. Turning is a material removal process used in machining to create rotational parts.
Milling and Turning are very similar and there is often confusion between the two, but the main difference lies in which part is turning during the process. With Turning, a metal bar is fed into a lathe, rotating at high speed while portions of the metal are removed by a single-point cutting tool. Whereas with Milling, the workpiece is stationary while a multi-point cutting tool rotates around it.
These are three of the more common methods of machining, other methods include shaping, boring, broaching and sawing, among others.
Early developments of welding date back to 1800 when Sir Humphrey Davy produced the first electric arc between two carbon electrodes with a battery. Edmund Davy then discovered acetylene in 1836, a colourless gas with a garlic-like odour which is now immensely popular in welding as it is the only gas which can weld steel due to the heat it can reach (3150 c) among other benefits.
Welding as we know it today was not invented until 1881 beginning with August De Meritens joining lead plates together. Welding has advanced significantly since then, including more efficient techniques being developed for fast, accurate and effective welding and the introduction of robotic welding.
There are a number of welding methods, with MIG and TIG welding being two of the more common types which are guided by a range of weld symbols used by designers to communicate with welders.
MIG welding stands for Metal Inert Gas and is an arc welding process which works when a solid wire electrode is continuously fed through a welding gun into the weld pool, where the two base materials are joined together. TIG welding, an acronym for Tungsten Arc Welding, produces the weld with a non-consumable tungsten electrode.
Other methods of welding include Shielded Metal Arc Welding (stick welding), Submerged Arc Welding (sub-arc welding), and Electroslag Welding, among others.
There are a number of welding methods, with MIG and TIG welding being two of the more common types.
Stamping (also referred to as pressing) is very similar to punching although the workpiece is not cut during this process. The first coins were believed to have been stamped by the Lydians (Turkey today) in the seventeenth century B.C.
It was not until the 1880s that Stamping was further innovated when used for mass-producing bicycles.
Today, stamping involves placing flat sheet metal in either coil or blank form into a stamping press where a tool and die form the metal into the desired shape once pressed.
Common types of stamping include Progressive Die Stamping – where a number of stations are used, each with its own unique function, Fourslide Stamping (or Multi-Slide Stamping) – multiple bends can be achieved at once with fourslide stamping, as the name would suggest a fourslide has four slides which enable four different tools to be used at once and Deep Draw Stamping – where a sheet metal blank is pulled into a die via a punch, with this forming the desired shape.
Punching is a process of using a punch press to force a tool, as is suggested, called a “punch” through a workpiece in order to create a hole. This method is not suitable for metal only as it is used on other materials such as vulcanized fibre (laminated plastic), paper and a wide range of standard plastics.
Punching is one of the more cost-effective methods of producing holes in medium to high production volumes as several different shapes can be cut out of a single press (this method is called blanking).
The sheet metal bending process – also referred to as press braking, flanging, edging, flanging and die-bending – is a process of deforming sheets of metal by putting a bend or fold into it; basically turning a flat piece of metal into a piece which is bent, or which holds a different shape.
Curved structures were frequently constructed from iron which was built up from wrought iron components or cast in liquid form in a curved profile, before steel began being used in a more general sense towards the back end of the 19th century.
The most common types of bending include Air Bending – this method requires far less contact with the metal than others and this method is the most common method used at ADS Laser Cutting, Bump Folding or Step Bending – this method allows for a large bend radius to be formed without deploying specialist tooling and Coining – this is one of the simpler forms of bending where the term “coining” originates from the stamping of coins with a die, as each end product is exactly the same. In sheet metal coining is used when creating consistent, accurate bends.
The most common types of bending include Air Bending – this method requires far less contact with the metal than others and this method is the most common method used at ADS Laser Cutting
Sheet metal rolling has quite an extensive history and took on many advancements before getting to the stage it is at today.
The basic principles were found in the Middle East and South Asia as early as 600 BCE with the earliest rolling mills being Slitting Mills, having been developed in 1590. These were used to form a plate of iron by passing flat bars between rolls, before being passed between grooved rolls (slitters) which produced the rods of iron.
Experiments took place in around 1670 to create tinplate by rolling iron before Major John Hanbury rolled what is called the “Pontypool Plates” in 1697 with a Mill built in Pontypool.
Rolling mills for other materials such as lead in the 17th Century and copper and brass during the 18th Century.
More modern practices of rolling came about in 1783 and were pioneered by Henry Cort of Funtley Iron Mills. Through a patented design by Cort, mills were able to produce 15 times more output per day than with a hammer. Henry Cort is referred to as the “father of modern rolling” due to this innovative rolling method he designed.
There are two primary methods of rolling, these being hot rolling and cold rolling. Hot rolling is a metalworking process in which metal is heated above the recrystallization temperature to plastically deform it in the rolling operation – this makes the metal easier to form and work with when being run through a series of rollers to achieve its finished dimensions.
Vice versa for cold rolling, the temperature of the metal is below the recrystallisation level. Similarly, it is a process where the sheet metal is compressed and squeezed between two rollers, with the amount of strain determining the hardness and other material properties when the process is complete.
Shot blasting is an abrasive blasting process which is used to clean, strengthen or polish metals prior to being powder coated, for example, and is a common method used at ADS Laser Cutting.
Materials which are often used in shot blasting include copper shots, steel grit, and aluminium pellets.
Another popular type of abrasive blasting is sandblasting. The key difference between shot and sandblasting is the type of mechanism used to propel the stream of abrasives. Shotblasting requires a mechanical force such as a rapidly turning turbine which separates the materials while sandblasting is achieved by firing materials down a blasting nozzle onto the surface of the workpiece with compressed air.
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