What Is Straightening Sheet Metal?

Posted on Jan 25, 2021

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straightening sheet metal

Straightening sheet metal is a process for making the following machining steps going more smoothly. It uses external forces like heat or pressure to reform the sheet metal, making them into the correct formation.

What Is Straightening Sheet Metal?

Straightening sheet metal is a process for making the following machining steps going more smoothly. It uses external forces like heat or pressure to reform the sheet metal, making them into the correct formation. In common situations, there are two situations that would need to straighten the sheet metal, one is in the beginning machining progression, the other one is while it is required.

As we know, sheet metal originally comes from metal sheet coils. In general, metal sheets would be collected to make a big role for the convenience of transferring or something. Before any machining with it, decoiling the metal sheet and making them as flat as possible would be the first thing to do for the next steps. Sometimes the sheet metal would be deformed such as unevenness, bend, twist, wave, or other deforming situations.

The well-straightened sheet metal would be used as the raw material of stamping, pressing, or cutting machining progresses like milling or drilling. Then, besides the situation above, when should the sheet metal be straightened? The answer would be that while the sheet metal part of something, such as vehicles, etc., needs to be repaired. There are various ways for straightening sheet metal, for example, using machines, with the help of some tools, or even simply using a hammer.


Why Do We Straighten Sheet Metal?

In summary, straightening would be required while the sheet metal is deformed. Below are three situations that might cause deformation on the sheet metal:


● Residual Stress

The most common deformation caused by residual stress would happen during the rolling progress. Rolling is a machining process that uses a couple of rolls to flat or form the sheet metal. In general, it should be done perfectly which would provide fine sheet metal for further use.

It is a general situation with a happy ending. However, sometimes the mistakes on mechanical adjustments, such as inconsistent distance between rolls, would just happen. Once it happens, the inconsistency would seriously influence the horizontal of the sheet metal. For example, if the distance of the two rolls being too narrow, the sheet metal would be extended more which will make parts of it thinner. On the other hand, if the distance of the two rolls is farther, the sheet metal would not receive enough pressure, which makes it thicker. As result, the sheet metal the machine makes would be bumpy and recognized deformed which is not allowed to use on making products.


● Deformation Caused by Steel Machining Progression

Besides pressure, metals could be machined in many other ways, such as heating and cooling, shearing, cutting, welding, etc. In the previous section, we learned that inconsistent pressure would deform the sheet metal. The same concept of it, the machining ways listed above might damage the sheet metal if these ways are applied unevenly. For example, temperature changes like uneven heating or cooling would cause the sheet metal to form unevenly.


● Improper Transportation or Storage

Deforming would occur in any stage, sometimes during production, sometimes during transportation, sometimes even happens in storage places. The most common way to store the well-formed sheet metal or the metal materials is stacking them together which is recognized as the most space-saving way, but in fact, might cause damages on some level due to the pressure.

:: Read more: An Overview of Thin Sheet Metal


How to Straighten Sheet Metal?

The principle of straightening is to use external forces like pressure or heat to correct the deforming sheet metal into the right forms. To explain how the forming progression goes, we can first see the sheet metal as the collection of many parallel fibers. In usual situations, the fibers would be placed parallelly in order and these fibers would strengthen the sheet metal and keep it parallel. Below are two straighten methods that might help to make the sheet metal flat again.

The first one is the manual straightening method using hammers. It is suitable for reforming small workpieces, is the most convenient method which everyone can easily reach with the metal straightening tool and operating progress. Before hammering the sheet metal into the right form, you need to put some oil on it first in order to avoid slipping off and prevent potential damages to the operators. Different hammers would be used to deal with different adjustments:


● Flat-Head Hammer:

A Flat-head hammer is commonly used to strike flat surfaces, deep recesses, or edge corners.


● Stabbing Hammer:

Arc-shaped parts and components can be adjusted by stabbing hammers. Compared with flat-head hammers, the round shape part of the stabbing hammers can help the arc-shaped parts keep their shape.


● Arch Hammer:

Similar to the stabbing hammer, an arch hammer is also usually used to deal with the deformed arch parts on the workpieces.


● Intermediate Hammer:

An intermediate hammer, as its name shows, can prevent the hammer from directly striking the workpieces. An intermediate hammer works as an intermediate part between the workpiece and the hammers. With this special hammer, the workpieces would not be directly struck by the hammer and can be less risky or broken by a high external force.


● Flat Head Plastic Hammer:

A Flathead plastic hammer is commonly used to trim box corners.


● Crane Hammer:

Crane hammer is usually used to eliminate small pits which would make the surface of the workpieces bumpy and ugly. Hammers listed above are the ones which are commonly used. There are still other kinds of hammers that would be used according to various demands of dealing with the surface of workpieces.

The second method is by using machines. When the deforming is too serious that using hammers is no longer the best solution, as an alternative, straightening machines would become a better choice. In general, machinery used on straightening workpieces is usually used to correct larger workpieces that cannot be adjusted easily by hammers. The most common way of straightening the deformed sheet metal is using rolls to flat the sheet metal. It would require one or two workers, depending on the size of the sheet metal, to operate the progress. While straightening the sheet metal, the deformed sheet metal would run through the gap between the gap of rollers, then the rollers would press the whole plate evenly and make their thickness as average as well:


● Flame Straightening:

Flame straightening uses heat to make the sheet metal become its right shape again. This is because metals can be bent without worrying about breaking if the temperature reaches a specific degree. Here are three ways that are mostly used in heating metals: spot heating, linear heating, and triangular heating.

While applying the heating methods, the flame would be used to touch the sheet metal in different ranges and spots. For example, spot heating tends to make circles while heating, and the linear heating would make the flame go forward and back in a line, while the triangular heating would make the heating area a triangle, usually on the edge of the sheet metal.


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