What is Sheet Metal Fabrication?

Sheet metal fabrication is the process of turning flat sheets of metal into their desired shape by using different mechanical and manufacturing methods.

Sheet metal fabrication commonly uses steel, aluminium, brass, copper and magnesium but theoretically, any metal that can be formed into a sheet can be used.  There are many steps involved in creating these different shapes and the metal sheets undergo a variety of processes before it reaches its final end product.

There are many ways to shape sheet metal but it can be broadly classified into four main categories – cutting, forming, joining and finishing. This may sound relatively simple but there are many methods used for each of these manufacturing processes.

The proper choice of manufacturing method for each category greatly influences the manufacturing efficiency, cost, appearance, durability and precision of the final product.

In its most simple form, sheet metal fabrication starts with the design of the end product or a blueprint. The specifications of the design will determine the required material and thickness of the sheet metal used. The design will also provide information on how to cut, form and finish off the product. This information is used to determine the best method for manufacture.

Sheet metal fabrication methods

There are so many different methods for Sheet Fabrication. Some of the more common fabrication methods are detailed below:

Cutting

There are a variety of methods and processes to cut sheet metal, they can be broadly classified into two main groups – cutting without shear forces and cutting with shear forces.

Cutting without shear

Several processes enable cutting to be accomplished without the use of shear forces.

• Laser cutting is a process where a high-powered laser beam is used to heat and vaporise the material thus producing a cut into the material. Efficient and highly productive, this method allows complex shapes to be cut out of the sheet metal. Laser cutting also enables engraving and other markings to be made on the sheet metal.

• Plasma Cutting works very similarly to laser cutting but is used mainly on thicker sheets of metal and also where surface finishing is not of great importance. The plasma cutter can only be used on electrically-conductive material. Plasma is an electrically charged beam of compressed ionized gas that is shot through the cutter and onto the metal sheet.

• The grounding of the metal sheet completes the circuit and the material heats up substantially and melts away. The resulting cut is quite rough and the edges of the cut have burring and oxidisation.

• Water jet cutting uses a high velocity, high-pressure jet of water that contains other abrasives to make a cut into the sheet metal. Think of this as a concentrated, high-speed version of soil erosion. Water jet cutting provides extremely good surface finishing and produces no burrs. Further, since water is cool, there is no heat distortion.

• However, the process is much slower than laser cutting and does not accord the ability to do engraving or marking. Further, if the material is not properly supported, some distortion due to bending can occur due to the high pressure of the water jet.

Cutting with shear

This process involves applying a force that overcomes the material’s ultimate shear strength. A simple example of cutting with shear is to think of a knife cutting through fruit or vegetable.

• Cutting is the most basic method that uses a blade to cut through the sheet metal

• Shearing uses two blades, one on top of the sheet metal and the other underneath. It is used to perform straight cuts. Think of it as a pair of scissors with the difference being that the bottom blade remains stationary while the top lowers down to provide the cut.

• Blanking uses a die to press into the sheet metal to cut shapes out of it. Punching uses a similar technique but is usually used to create holes in the sheet metal. If we think of circles being cut out of a metal sheet, then blanking will produce a solid circle as the end product whereas punching would create holes on the metal sheet.

•  Machining covers a wide range of cutting processes using drill bits, lathes or saws to cut away material from the sheet metal.

Forming

While cutting removes material from a piece of sheet metal, forming is a process that reshapes the material to different contours. Some of the more common processes involved in forming are:

• Stamping basically presses the sheet metal between two dies to create the desired shape. Sometimes, the sheet metal goes through a progressive set of dies to get the desired shape. Think of it as plasticine being pressed into a mould to obtain the desired shape.

• Bending has various forms and can be done either by machines or by hand. The metal is bent to the desired angle or shape. For rolls or curves, Roll Bending uses a set of rollers to make different bends.

• Roll forming has similar effects to bending and is usually used for creating cross-section profiles. In this process, the entire sheet of metal, usually coiled sheet metal, is passed through a series of rollers that are configured at various distances and angles. This makes incremental bends at various angles to produce the final desired cross-section that are then cut to the desired lengths.

Joining

Often, parts or structures are made out of different components after cutting and bending and need to be joined together. There are different methods of joining.

• Welding and brazing are similar methods that use high temperatures to fuse the joints of metal with a filler. The main difference is that welding uses electricity to form an arc that creates the high temperature whereas brazing uses a torch flame to produce the high temperature required.

• Riveting uses small metal parts called rivets to join sheet metal pieces by embedding them through both sheets. Sometimes screws, bolts and nuts are also used. It is a faster and less expensive process than welding or brazing.

• For smaller structures the use of screws and bolts allows the structure to be self-assembled, especially for home use.

• Adhesives are often used for joining sheet metal. These include high-strength metal adhesives like epoxy, polyurethane and other adhesives that provide good bond qualities.

Finishing

The process of finishing is an all-encompassing term that enhances the physical and aesthetic properties of the product if needed.

• Standard Finishing is where nothing is done post-processing other than cleaning up and smoothening edges. Standard finishing is usually done when the material is already suitable for use in its application environment. Standard finishing is sometimes the preferred choice when the natural look of the material is desired. An example of this would be Stainless Steel.

• Anodizing involves a chemical process that converts the surface layer of the metal into an oxide. These layers are thin when compared to other coating methods, but are still extremely durable and offer protection against corrosion as well as provide wear-resistance. The most commonly anodized material is aluminium.

• Chemical film coatings are best described as sealant coatings and offer corrosion resistance but very little wear resistance. Anodized finishes can be applied over chemical film coatings to enhance its durability.

• Powder Coating is an excellent method to enhance the appearance of a product as it comes in a variety of colours. It uses a thermoplastic or thermoset polymer powder that is applied over the product and then cured under heat to produce a smooth, hardened surface.  

• Electroplating is the process of coating a metal with a thin layer of another metal by electrolysis. This process improves corrosion resistance and can also influence the mechanical properties of the material like electrical conductivity. Electroplating also allows the coating to get to hard-to-reach places and provides a smooth and even coating.

• Painting is probably the simplest form of finishing and is available in a wide variety of colours.

Uses of sheet metal fabrication

Many industries are reliant on sheet metal fabrication and these include aerospace, construction, automotive, and consumer goods to name a few. Common items that you may be aware of that are produced through sheet metal fabrication include automobile bodies, irrigation and drainage equipment, kitchen and restaurant equipment, elevators, doors, guardrails, and so many more.

Even items like screws, caps, cutlery and cooking utensils are often fabricated from sheet metal. The beauty of sheet metal fabrication is that it can be customised to your needs to produce different products and structures.

With so many uses for sheet metal, it is not difficult to understand why there is such a large consumer base for sheet metal products.

Need more information?

There are many more methods and processes involved in Sheet Metal Fabrication. With over 30 years of experience, NS Metal Fabrication Specialist offers a highly personalised approach to the customisation and supply of high-quality metal and steel.

Contact us today to discuss your sheet metal fabrication needs or simply to get further information on how we can work together.