What Methods Are Used To Cut Sheet Metal
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What methods are used to cut sheet metal? We look at popular sheet metal fabrication techniques and tools and the types of sheet metal cutting operations.
What is sheet metal fabrication?
Sheet metal fabrication is the process of creating functional parts and components from basic sheet metal. Fabricators use many techniques to do this, including bending, stretching and cutting sheet metal.
Common sheet metals used in the process include zinc, copper, aluminium and stainless steel, and they come in various gauges but are usually between 0.015 - 0.635 cm (0.006 - 0.25 inches).
While thinner metals are more malleable and easier to work with, thicker metal is best for components and parts that need to be robust.
If the parts or components you need must be flat or hollow, then sheet metal fabrication offers a brilliantly cost-effective alternative to machining or casting. The sheet metal fabrication process is also much faster, with minimal waste compared to other fabrication techniques.
Given this speed and cost-effectiveness, it's not surprising that sheet metal fabrication is used in an incredibly wide range of industries and consumer markets, including the energy sector and by aerospace and automotive manufacturers.
Popular Sheet Metal Fabrication Techniques and Tools
While the uses of fabricated metal are varied, with fabricated components being used in various industries for various ends, the techniques and tools used to make them are fairly standardised. You'll find these techniques and tools used in metal fabrication workshops worldwide.
Sheet Metal Bending
Fabricators can bend metal into most desired shapes by applying force in the right areas. While the shape of the sheet metal will change, the amount and volume of material are maintained through bending, meaning there is little to no waste.
Despite there being many ways to bend sheet metal, there are a couple of techniques that are more popular than others. These are:
One of the most common ways to bend sheet metal, form bending, involves placing the metal over a form or edge and hammering it into the desired shape.
Press Brake Bending
In this technique, the metal sheet is placed on a gated surface with a flat bar over the top. The gated section is then raised to bend the sheet into the desired shape.
Sheet Metal Cutting Processes
Cutting is another of the most common metal fabrication techniques. It is especially useful if the metal sheets you are using become stretched or disfigured, providing a way to cut the sheet back into the shape you want. Just as with bending, there are various tools used to cut sheet metal, including:
- Shears - From power shears to hand shears to throatless shears, there are many types of shears, or metal cutting blades, used to cut sheet metal. Also known as tin snips, hand shears are an essential tool for any metal fabricator; as the name suggests, they are manually operated. Power shears are either pneumatic or electric and offer an easier way to cut through sheet metal. However, while they are easy to use, they are usually unable to cut complex shapes. Throatless shears are manually operated and allow you to cut heavier metal gauges without bending or deforming the sheet. Choosing the right blade is essential when cutting sheet metal.
- Angle Grinders - A disc, circular saw or wheel spins at high speeds to cut the metal sheet. Of course, they require you to wear safety glasses, face shields and other safety gear when used to cut metal, like any other cutting tool.
- Plasma Cutters - Plasma cutting, not to be confused with laser cutting tools, is incredibly useful when accurately cutting metal is needed, for example, if you are trying to cut complex shapes. Plasma torches work by heating compressed air which ionises the atoms to form a stream of incredibly hot plasma. Given how intense the heat of the ionised gas is, appropriate safety precautions must be taken.
In die cutting, the die is a predetermined shape that you press into the sheet metal to cut out the desired shape. You can think of it almost like a pastry cutter. This is the best cutting technique to avoid wastage and provides the most accurate way to get the shape you want.
Sheet Metal Stretching
As you can probably imagine, stretching is the opposite method to shrinking. Fabricators use various tools to stretch sheet metal into the desired shape. These include:
- Stretcher - Similar to the automated shrinker, the stretcher is operated by hand or foot and grips the metal sheet from two ends. Rather than slowly compressing the sheet, the stretcher naturally pulls the other way and stretches the sheet out.
- Dolly and Hammer - This method looks similar to how you would hammer dents out of a metal sheet. Holding the sheet in the dolly, you hit it with a hammer, and the repeated compression stretches the metal.
- English Wheel - An English wheel is essentially an automated version of the dolly and hammer stretching method. The metal sheet is rolled between a wheel and an anvil to compress and stretch the material accurately. It's also one of the most efficient ways to work out any dents or imperfections in the metal sheet.
Sheet Metal Shrinking
If the sheet metal you use is dented or deformed, it needs to be shrunk. Of course, this isn't always possible, especially if the metal sheet is too damaged or has giant tears in it. The techniques and tools used in metal shrinking include:
- Tucking - This method involved bunching the edges of your metal sheet with a tucking fork. You can then reshape and flatten the sheet with a hammer.
- Shrinker - A shrinker is an automated tool that grasps the metal sheet from two ends with a set of jaws. Operating it either by hand or foot, you can move the jaws together to shrink the metal. It's a more precise method than tucking and leaves no burred edges, but it takes much longer to achieve the desired shape.
- Heat Shrinking - If an area of your metal sheet is overstretched, you can shrink it back by heating the area and allowing it to cool.
Types of sheet metal cutting operations
An important distinction regarding cutting is the difference between sheet and plate metal. While sheet metal usually measures around or less than 6 mm in width (1/4 inch), plate metal is often much thicker.
Therefore, while most cutting methods will work for both sheet and plate metal, many of these operations will be more complicated when the material is much thicker. Here are some of the most common cutting operations used when cutting thin sheet metal:
Blanking is very similar to punching, the only difference being the waste.
While in punching, the slug that is detached from the middle of the sheet metal is thrown away, in blanking, the surrounding metal left after the shape is punched out is the waste.
Therefore, the shape of the punch itself is more crucial for blanking, as it's this shape you want to create.
This form of cutting operation is best when you need to create component blanks for washers or gears or when making curved cuts.
The punching process is fairly straightforward and involves punching a specific, usually small, shape out of sheet metal.
The shape that is punched out and detached from the larger sheet of metal is known as the "slug" and is typically discarded as waste by the vast majority of manufacturers.
There are many varieties of sheet metal punching operations, depending on the shape you need to create.
This is what usually determines the type of punching you require, compared to other factors involved.
Shearing is another similar cutting operation where the metal sheet is cut in straight lines or at angles and is mostly used to cut larger pieces down to smaller ones.
These smaller metal pieces are usually sent further down the line for use in different manufacturing processes. This is where we find the difference between shearing and blanking.
While blanking creates small, detailed pieces of sheet metal, shearing prepares larger pieces with straight cuts that go on for further fabrication or manufacturing.
Shearing is also a simpler process since all you do is place the sheet metal between a surface and upper cutting blades and cut it.
Trimming is another simple cutting operation that is vital for any professional metal fabricator.
As the name suggests, trimming involves removing any excess material from the edges of your sheet metal with precise cuts.
Typically, this is one of the last processes involved when generating a specific component, as it provides a way to refine the pieces you've generated through other methods of cutting and fabricating.
Deburring can be thought of as a more intricate method of trimming. Rather than removing entire sections of excess material, deburring removes any burrs and sharp edges from your sheet metal pieces.
Rather than using large machinery to achieve this, deburring is usually done with small, hand-held tools, possibly similar to metal files, leaving your finished product with smooth edges and splinters. Like trimming, deburring is a final sheet metal fabrication process that a component will undergo.
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