5 Basic Sheet Metal Fabrication Techniques

Sheet metal fabrication is the process of forming metal sheets of steel or aluminum into the desired shape(metal structures or products), by cutting, punching, folding, and assembling. The completion of a product usually comprises many steps – from cutting and bending to surface treatment and assembling.

Cutting Metal

Cutting is typically the first step in sheet metal manufacturing. As the name clearly indicates, it consists of cutting the metal sheet. In other words, manufacturers start with a rectangular metal sheet and, based on the customer’s part design, the material is cut to size. There are various methods for cutting sheet metals. Several ways you could cut metal for your project include:

Laser Cutting

Laser cutting metal involves using laser beams to melt metals and alloys, thereby causing smooth, sharp cuts.

The laser cutting process consists of two operations working in synchrony.

The first involves the material absorbing the focused laser beam – the energy that causes the cut. The second involves the cutting nozzle, concentric to the lasers, providing the process gas required for the cutting. The gas protects the processing head from vapors and splashes and helps remove excesses from the kerf.

Laser cutters can cut a wide range of metals, ranging from stainless steel to mild steel and non-ferrous metals. However, more reflective metals such as aluminum may be more challenging to cut. In such cases, fiber lasers are usually the better option. The thickness of the metal can range between 20mm to 40mm, with the maximum thickness depending on the laser’s power.

The laser cutting process is best suited to industrial applications. It is highly flexible, time-efficient, and can give a high degree of precision. However, the process has a high energy and gas consumption, translating to high investment costs and strict safety requirements

There are essentially three methods for laser cutting sheet metal.

Laser Beam Fusion Cutting

The laser beam fusion cutting process uses an inert gas, mostly nitrogen. The low-reaction process gas continuously vaporizes the cutting gap of the material. As the molten material gets removed, inert gas prevents oxidation at the cutting edge without interfering with the process.

This laser cutting method is suitable for cutting flat, thin sheets of aluminum alloys and stainless steel that require high aesthetic appeal and fewer finishing operations.

Laser Beam Sublimation Cutting

As the name suggests, laser beam sublimation cutting evaporates the material. Instead of melting the material like other laser cutting processes, they are immediately changed from solid to gas – sublimation.

Like fusion cutting, laser beam sublimation cutting uses inert gases to blow the material’s vapor out of the kerf. So, there are no oxidants on the cutting edge. It is often used in cutting organic materials like wood, leather, textiles, etc.

Laser Beam Flame Cutting

Laser beam flame cutting uses a combustible gas – oxygen to thrust out the molten material. The laser heats the workpiece creating spontaneous combustion after melting the material. The oxygen gas provides more energy for the cutting process through oxidation – an exothermic reaction.

Flame cutting is ideal for cutting mild steel and fusible materials such as ceramics. This cutting process may cause burns on the cutting surface since the gas is an oxidant. Proper optimization of the process parameters will help prevent the formation of burrs.

Benefits Of Sheet Metal Laser Cutting

High-Precision and Accuracy

Laser cutting is a suitable fit for sheet metal cutting because of its extreme precision. The machines are equipped with the ability to make intricate cuts at extreme precision and accuracy. Industrially, laser cutting is the go-to technique for cutting sheet metal with specific details requiring tight tolerances.

Some cutters can make precise cuts with an accuracy of up to 0.0005 inches. This is why it has remained a mainstay in most manufacturing companies. Since the lasers melt away the metal parts, the cutters produce little or no burring. Instead, it leaves a clean, smooth, and sharp edge.

Automated Process

Laser cutting runs by Computer Numerical Control (CNC) systems. Once the technical operator inputs the programs into the computer, the process runs independently. Therefore, it requires less human interference and overall labor. Also, there’s little or no margin for error with increased cutting efficiency.

Damage Prevention

There’s this misconception that laser cutting metal causes warping. However, that is untrue. The heat from laser cutting only affects minute portions of the material, not affecting tolerance.

Moreover, the laser cutting process is quick; the lasers heat and melt away the portions to be removed. So, the heat does not significantly affect the other parts of the material. In most cases, there is no distortion or warping of your materials.

Compatible With Most Materials

Another critical advantage of this subtractive manufacturing method is its ability to work with an extensive array of materials. It easily cuts through each material, whether it is copper, aluminum, stainless steel, or even titanium. After all, it involves using lasers at very high temperatures to melt the material.

Relatively Low Cost

Indeed, laser cutting machines are expensive. However, compared to other CNC machine, it is more cost-effective. Moreover, it’s a single machine for all – that is, a single laser cutting machine is ideal for all your cutting operations. You do not need any machine modification for different cutting operations.

In addition, it’s durable. The device makes no contact with the materials you are cutting, so there is little, or no friction nor surface wear out. Also, it does not have multiple parts, so there are fewer maintenance and servicing requirements. In general, there’s a reduced operational cost of using a laser cutter compared to other customary manufacturing tools.

High Versatility

Besides the compatibility of laser cutting with most materials, the process is highly versatile. Unlike other devices, you can employ a laser cutter for several cutting functions, from simple to complex cuts and those requiring tight tolerances and intricate designs. This feature makes it an excellent choice for most industries.

Low Energy Consumption

Indeed, laser cutters require power to heat and melt materials effectively during cutting. However, the cutting technique is more energy efficient than other cutting methods.

In addition, unlike other machines, it has fewer moving parts, which means fewer energy requirements. Also, the machine’s high speed means quick cutting, saving time and energy.

Water jet

Water jet cutting is a kind of sheet metal fabrication process cutting nearly any type of material, soft and hard. In this process, pressurizing pumps deliver high-pressure jets of water that can cut various types of materials.

Waterjet cutting machine can deliver water at a speed of three times the speed of the sound that can create a destructive force to cut almost any material. Besides, water jet cutting technology is an excellent solution to cut thermally sensitive or thicker materials.

Types of Waterjet Cutting

There are two types of water jet cutting machines – Pure waterjet cutting and abrasive waterjet cutting machines.

Pure Waterjet Cutting

Pure waterjet cutting uses pure water to complete the operation. This process is ideal for soft and medium-hard materials.

This machine is considered the most environmentally friendly machine as it does not release any toxic gas or dust. In addition, you can use the water further and, in the end, feed into the water cycle.

In a pure waterjet machine, the water jet is comparatively small, which can be less than 0.1 mm. These machines are excellent for precise cutting at the optimum level for materials with small thickness.

Abrasive Waterjet Cutting

Abrasive waterjet cutting machine incorporates abrasive water for a more dynamic cut. You have to add three additional components to convert a pure water jet into an abrasive one.

In addition, you will need an abrasive agent also. The primary task of the pure water nozzle is to form highly compressed water into the jet. Then the jet passes through the water to the abrasive mixing chamber at a speed of 1000m/s.

The abrasive material mixes with the water and exits at high speed to cut the desired material. In most cases, olive sand and garnet sand are used as abrasive materials. If the cutting material is softer, corundum is used as abrasive.

Abrasive water jet cutting machine is 0.2mm larger than a typical water jet machine on average. With an abrasive water jet cutting machine, you can cut steel up to 50 mm and 120 mm of other metals.

What Materials Can a Waterjet Cut?

Waterjet is a versatile cutting process that can cut a wide range of materials using pressurized water and abrasive. You can cut very thick material and fragile material also. As a result, manufacturers are using this technology more and more.

Here are some of the important materials that water jet can cut:

• Metal
• Glass
• Composites
• Tile
• Plastic
• Rubber
• Ceramic
• Stone

Water jets can cut a thickness that much other technology can not. You can cut 12 inches or greater with a water jet!

Shearing

Shearing is a metal fabrication process that’s used to trim and remove unwanted material from sheet metal. It involves the use of a machine or tool, such as a bench shear, to slice through sheet metal with extreme precision. Shearing doesn’t require the use of heat — sheet metal is typically sheared while cold or at room temperature — nor does it produce waste in the form of chips, making it an attractive choice for manufacturers. To learn more about the metal fabrication process shearing and how it’s performed, keep reading.

How Shearing Is Performed

Shearing is performed by slicing through sheet metal with a blade-affixed machine or tool. Sheet metal is first secured between the tool’s or machine’s blades. Most shearing tools and machines have a squaring arm to control the location of the cut. After placing the sheet metal in the proper position with the squaring arm, the top blade drops to slice through the sheet metal. As the top blade comes down, the bottom of the sheet metal is pressed into a lower blade.

There are several types of shearing tools and machines, one of the most common being a bench shear. Also known as a lever shear, a bench shear is a cutting tool that’s mounted to a working surface, such as a workbench. It’s small, lightweight and easy to use, though it requires the use of a stable and secure surface for mounting.

Guillotine machines are also used to perform shearing. Also known as a power shear, it’s a more complex shearing machine that’s powered either mechanically or hydraulically. The powered blade allows guillotine machines to slice through sheet metal faster and more effectively than a bench shear.

Shearing Advantages

• Incredibly fast, with shearing cutting through sheet metal in just seconds
• Creates clean cuts with smooth edges
• Can be performed on sheet metal in a variety of diameter sizes
• Cost-effective for high-volume manufacturing applications
• Doesn’t produce waste in the form of chips
• Can be performed on room-temperature sheet metal, eliminating the need for heating sheet metal
• Numerous types of metals support shearing, including aluminum, steel, stainless steel, bronze, iron and copper

Shearing Disadvantages

• Not ideal for low-volume manufacturing applications
• Exceptionally hard metals like tungsten cannot be sheared
• May cause deformity in sheet metal

Bending Metal

Bending of sheet metal is a common and vital process in manufacturing industry. Sheet metal bending is the plastic deformation of the work over an axis, creating a change in the part’s geometry. Similar to other metal forming processes, bending changes the shape of the work piece, while the volume of material will remain the same. In some cases bending may produce a small change in sheet thickness. For most operations, however, bending will produce essentially no change in the thickness of the sheet metal. In addition to creating a desired geometric form, bending is also used to impart strength and stiffness to sheet metal, to change a part’s moment of inertia, for cosmetic appearance and to eliminate sharp edges.

V-bending

This is the most common sheet bending method as it is used for most bending projects. It employs an instrument known as the punch and v-die to bend sheet metals at desired angles. During the process, the bending punch presses on the sheet metal placed over the V-die.

The angle formed by the sheet metal is dependent on the pressure point of the punch. This makes this method easy and efficient as it can be employed for bending steel plates without altering their position.

Roll Bending

Roll bending is a method used to bend sheet metals into rolls or curved shapes. The process employs a hydraulic press, a press brake, and three sets of rollers to make different bends or a big round bend. It is useful in forming cones, tubes, and hollow shapes as it takes advantage of the distance between its rollers to make bends and curves.

Wipe Bending

Wipe bending is another method used in bending sheets of metal edges. The process depends on the wipe die. For example, the sheet metal must be properly pushed onto the wipe die. The wipe is also responsible for the determination of the sheet metal’s bend inner radius.

Rotary Bending

This bending method has an advantage over wipe bending or V-bending because it does not lead to scratching the material’s surface. It is also ideal because it can bend materials into sharp corners. For example, it is used in bending corners greater than 90.

Shrinking Metal

Some fabrication projects require shrinking metal in order to smooth out dents or create the desired shape. Three sheet metal shrinking methods are:

Heat shrinking

A torch is used to heat the dented section of metal, this overstretches the metal, causing it to shrink once it cools.
Tucking metal – This uses a planishing hammer and tucking fork to tuck the edges of the sheet metal and hammer them into place.

Shrinker machines

As opposed to the two previous hands-on approaches to sheet metal shrinking, shrinker machines can be used to automate the shrinking process. This machine has jaws that grab the sheet metal and force it together, shrinking it into the desired shape.

Finishing Metal

Once you’ve cut, stretched, shrank, and welded your metal, the final basic sheet metal fabrication step is to finish your project. Adding a finish to your metal will enable it to last longer and perform better. Three common finishing techniques are:

Sandblasting

This involves shooting sand and other abrasives against your sheet metal at a high velocity. Sandblasting creates a matte texture on your sheet metal and is often used to prepare metal for coating.

Buff polishing

This finish is created by using a cloth wheel to buff the surface of the metal. If you want your metal project to shine, then buff polishing is likely the technique for you.

Metal plating/coating

Various coats can be applied to your project via chemical baths, which alter the substrate and improve the corrosion resistance and durability (as well as look) of your sheet metal project.

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