Basic knowledge Sheet metal working and metal working - bending, punching & Co.

Editor: Theresa Knell

What is sheet metal working? We provide basic information as well as relevant definitions of terms and briefly introduce manufacturing processes, materials, tools and machines.

Car construction is a textbook example of sheet metal working.
Car construction is a textbook example of sheet metal working.
(Source: Audi)

Sheet metal is not a specific material. Rather, the term is used for metals that have been formed into shape. As a rule, sheet metal has a rectangular shape. It is also characteristic that the thickness of a sheet is considerably below that of its length and width.

In addition to steel, numerous other metals such as copper, aluminum and gold as well as brass alloys can be processed into sheet metal. In order to be processed into sheet metal, however, the materials used should have specific characteristics, i.e. a certain toughness and rigidity, and of course be ductile, i.e. formable. These requirements result in restrictions with regard to the materials that can be used. Thus, it is not possible to process very brittle or extremely stiff materials into sheet metal.

Sheet metal working: Lasertube family from BLM: the LT7 cuts tubes and profiles.
Sheet metal working: Lasertube family from BLM: the LT7 cuts tubes and profiles.
(Source: RAS)

According to this, sheet metal is a semi-finished product that can be produced over a large area, whereby sheets are generally light, thin, stable, elastic and flat. Due to these specifics, they are suitable for all types of cladding and covering. In addition, sheet metal can be deformed in many ways, i.e. it can be welded, bend, punched or cut. A wide variety of shapes can be made from sheet metal, which is why it is used as the starting material for a wide variety of products.

What is sheet metal working?

The term "sheet metal processing" covers a large number of manufacturing processes. Basically, the word sheet metal working refers to the manufacture of products, components and parts made of metal. In addition to welding, cutting and bending, the processes of sheet metal processing also include punching, forming, rolling and joining. Sheet metal forming is usually also included in sheet metal processing, with the following subcategories:

  • Welding
  • Gluing
  • Bending
  • Piercing
  • Drawing
  • Steel construction
  • Layer forming
  • Heating coil
  • Cutting
  • Slitting
  • Bending punching
  • Laser cutting
  • Laser processing

Within the framework of sheet metal processing, both soft and resistant sheets can be produced, whereby the different characteristics are achieved by different alloys. For example, there are numerous elements that can be added to steel in the liquid state during metalworking and that determine the material properties of the sheet metal produced. In addition to silicon, nickel and chromium, these elements also include titanium, copper, niobium and molybdenum.

Car construction is a textbook example of sheet metal working.
Car construction is a textbook example of sheet metal working.
(Source: Audi)

In metalworking, sheets can be made from different types of steel as well as aluminum and other metals - these are again available in different alloys. In order to categorize the different sheets, there are standards subsuming the materials according to their properties. In addition, material numbers were introduced to ensure a clear structuring of the sheets.

A brief history of sheet metal working

Anyone looking for the oldest form of metalworking will inevitably come across forging. In forging, metals are machined by means of force, for example with the aid of a hammer. Nowadays, this form of metalworking is very rarely found in the industrial sector and is rather used in the artistic sector. The first metal sheets were made of soft materials such as silver and gold. In the course of metalworking, the blacksmiths were able to shape these materials into thin sheets, from which jewelery and coins were subsequently made for instance.

A little bit later, the materials iron and copper also found their way into sheet metal processing. Especially in the High and Late Middle Ages iron sheets were used to make knight's armor. At that time, rolling was still unknown in metalworking. Instead, the sheet metal was processed with hammers or hammer blows until the materials had the desired thickness. Of course, sheet metal and silver and gold were valuable materials - solely because of the value of the raw materials. However, iron sheets also became an expensive commodity, because the sheet metal processing was very complex and time-consuming. The raw materials had to be formed into sheet metal by pure manual work and with the aid of simple tools. Sheet metal processing therefore required a high degree of practice and experience.

When large hammers driven by water power were first used, this led to simplifications in metalworking. Although the hammers shortened the sheet metal working time due to their enormous dimensions and weight, the production time could still take several days, depending on the size of the sheet metal. The first metalworking machines were finally developed during the industrial revolution. These were used to roll metal ingots to produce sheet metal. This not only shortened the production time in metalworking enormously, but also improved the quality of the sheets in terms of flatness and thickness. As a result, sheet metal not only became cheaper, but was also used to manufacture a large number of other products.

The two most important trade fairs in Germany are the biennial Blechexpo in Stuttgart and the Euroblech in Hanover.

Meanwhile, sheet metal processing and metal working have also arrived in modern times and offer a multi-faceted selection of materials, material thicknesses and formats. It should also be noted that the respective sheet metal properties can be adapted to the planned location of use by metalworking.

Manufacturing process of sheet metal processing

In the following, the different manufacturing processes of metal processing and sheet metal working are presented.

1. Forming - rolling, bending, forging, drawing etcetera

If one follows DIN 8580, the manufacturing process of forming constitutes a major group in metalworking. With this manufacturing process, the cohesion of the material is maintained. However, in the course of sheet metal processing, the already existing shape of a workpiece is modified by plastic deformation. An example of forming in metal processing is the rolling of steel.

Servo-electric press brake with multi-spindle drive from Coast One: Each of the spindles is driven by its own servo motor. The parallelism between the upper and lower tool is thus set and adjusted in a targeted, precise and fast manner.
Servo-electric press brake with multi-spindle drive from Coast One: Each of the spindles is driven by its own servo motor. The parallelism between the upper and lower tool is thus set and adjusted in a targeted, precise and fast manner.
(Source: Coast One)

In general, plastic deformation occurs in the forming process when the atoms, which are located on the so-called sliding planes, begin to shift as a result of external forces. The modifications of the technological and physical properties of the material occurring during sheet metal processing are subsumed under the term "hardening".

In general, the resistance to deformation of metals at room temperature is higher than at a corresponding forming temperature. Plastic forming of steel, for example, can be achieved at high temperatures with far less work and effort than at room temperature. In addition, high temperatures during sheet metal processing contribute to the immediate recrystallization of the microstructure and do not lead to hardening.

Cold and hot forming

In sheet metal forming, a distinction is made between hot and cold forming. Hot forming is a sheet metal forming process in which greater formability is achieved at high rolling temperatures, whereby the occurring forces are lower than in cold forming. The disadvantages of hot forming, however, are its poorer dimensional tolerances and scored surfaces.

In contrast, much more precise dimensional tolerances can be achieved in the cold forming process within the framework of metal processing. In this method of sheet metal working, the material is not heated, which increases its strength. In contrast to cold forming, the quality of the surfaces is also of high quality. A disadvantage, however, is that no welding suitability is ensured after cold forming. The workpiece can only be welded when it has been soft annealed in the course of sheet metal processing, thus minimizing stress.

As an association for companies in the sheet metal and hybrid structure processing industries and their research institutions, the European Research Association for Sheet Metal Processing initiates and finances industrial research projects for and in cooperation with technology leaders. The EFB provides support, identifies technology trends and starts innovative projects. The focus is on the rapid implementation of results and securing jobs in the interest of members, in particular SMEs.

2. Separation - cutting, punching, etcetera

Within the framework of the separating manufacturing process, which according to DIN 8580 also forms a main group among the manufacturing processes, the shape of a solid body, i.e. workpiece, is changed by locally eliminating, i.e. reducing, the cohesion. In this form of sheet metal processing, the final shape of the workpiece is therefore contained in its original form. Separation is a technique of metalworking, which also includes the dismantling of composite bodies. The main group "Separation" can be subdivided into six subgroups. There are the following subgroups:

  • Splitting
  • Ablation
  • Disassembling
  • Cleaning
  • Machining with geometrically determined cutting edges
  • Machining with geometrically indeterminate cutting edges

Cutting processes in sheet metal working include sawing, milling, filing, drilling, turning, lapping, thermal cutting, broaching and honing. Wedge cutting and shear cutting, on the other hand, are separating processes. During metalworking, the actual cutting process takes place at the point of action, i.e. at the point where the tool or machine acts on the workpiece. With regard to the cutting process in sheet metal working, it should be noted that relative movements, i.e. cutting, feed and infeed movements, are necessary and are carried out by one of the active partners. The power or energy supplied from outside to carry out the separation process is converted into friction, deformation and separation power at the point of action. They are dissipated in the form of heat via the active pair.

3. Joining - welding, soldering, etcetera

Joining, too, is one of the main production groups in sheet metal processing manufacturing technology defined by DIN 8580. Within the framework of this metalworking process, two or more solid bodies are permanently joined together. It is important that the bodies take on a specific geometric shape through sheet metal processing. Partly this is done by using a "formless material", i.e. the shape of the material is not defined. For example, adhesive counts as a formless substance.

Welding processes for industry and trade: EWM has various models in its portfolio that can be used to reduce both energy requirements and welding costs.
Welding processes for industry and trade: EWM has various models in its portfolio that can be used to reduce both energy requirements and welding costs.
(Source: EWM)

Joining also has further process groups that belong to metalworking. These are for example soldering, welding, gluing as well as screwing, joining by shearing and upsetting or riveting. In order to establish a connection between the workpieces, further components such as pins, screws, wedges or rivets are sometimes necessary. In addition, specific tools such as soldering irons, impact wrenches and so on are used in this production technology.

4. Surface treatment

In metalworking, the term "surface technology" covers all technologies that enable the surface properties of workpieces to be changed. It is important in this respect that the primary function of a workpiece in metalworking can be supplemented by surface treatment with additional functions. The principle of functional separation between the surface and the volume of a tool or component is the primary goal of this sheet metal processing manufacturing technique.

The volume of a workpiece has a specific function and certain characteristics such as machinability, strength, weight and so on. If a surface technology process is used in sheet metal processing, the workpiece or tool can be optimized in such a way that it fulfills a specific requirement profile and has a wide range of functions. These may include the following:

  • Barrier function, thermal insulation, diffusion, permeation, corrosion resistance)
  • Mechanical protection (friction, wear)
  • Optical function (decoration, absorption, reflection)
  • Functional integration (functional printing, printing process)
  • Electrical function (electrical insulation, conductivity)

Different methods can be used to carry out a surface treatment in sheet metal processing. The surface treatments in metalworking are therefore allocated to different process classes, which are the following:

  • Surface removal (electropolishing, burnishing)
  • Surface coating (chrome plating, powder coating, painting)
  • Mechanical surface treatment (shot peening, polishing, grinding)
  • Chemical surface treatment (pickling, degreasing, cleaning)

Machines & tools for sheet metal working

In the course of sheet metal processing, different tools and machines can be used, whereby a distinction is made between hand tools and power tools. Hand tools include files, iron saws, drawing pins, blind riveting pliers, pliers, hammers, shell irons, file pistons, ejector pistols and so on. Power tools, on the other hand, include drills, percussion drills, orbital, belt and random orbit grinders, soldering irons, lasers and so on.

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This article was first published by belchnet.