How to Get Rid of Shearing Defects?

Posted by Steven Glassner on February 11th, 2019

Shearing is a fabricating process used to cut metal sheets. The Shear blade machine consists of a shear table, blank holders, upper and lower blades. A back gauge is used to make sure that the cutting process is streamlined. When it comes to a perfect cut of the metal you need a high-quality shear blade like Amada shear blades which reduces the effects of variable sheet metal characteristics, internal stress, geometry to reduce the possible defects in the shear blades.
In this case, you need to take care of these natural effects. As they can make your shear blades defected and may reduce the final cutting quality of the product. If you work at the metal forming factory you must know that it is important to maintain your shear blades time-to-time. In this article, we have a list of variables used in this process along the solutions to get rid of possible shearing defects.
Cutting Angle
It is the cutting-edge angle of the blade. With two square edge blades, it requires higher cutting force than the upper blade. It is at an angle of 87°. And the lower blade is always at 90°. These are the ‘four-edge’ blades. Angled blades are called ‘two-edge’ blades.
Shearing Angle
This angle has a great effect on the shearing force. When you shear thin strips, this angle has an important effect on twisting. The shearing angle is less than 3°.
Blade Clearance
It’s the perpendicular distance between the shearing blades. The quality of results depends on plate thickness and material strength. If the cutting clearance is too small, the costs will be higher. If it’s too large, the result will be precise and large plastic deformation.
Clearing Angle
The clearing angle is fixed and set to 1.5°. The Blade ram is not perfectly vertical but is tilted pointing towards the backside to facilitate the piece separation.

The Shearing Defects and Solutions:

In shear blades, this defect twists the plate with its axis. When shear narrow down the strips, it results in twisting. Other responsible shearing conditions are related to metal geometry. For example, high thickness and short length reduce the width, material characteristics like the soft material, uneven stress distribution and cutting parameters like high rake angle, high cutting speed etc.
To get rid of this defect it is recommended to lower the rank angle. This way, it would become useful to add an anti-twist device. Also, this option consists of a series of cylinders that push the plate against the top blade. This force applies when it corresponds to the plate thickness.

Poor Edge Quality
During the shearing process, the material initially deforms in a very small area, with a residual deformation. Then the upper blade penetrates the material where cutting is neat and clear. At the end of the shearing process, the material would give up. Because of that, the material cracks with a rough and irregular surface known as the fractured zone. This is often not perpendicular to the plate but a variable angle. You can improve edge quality by adjusting blade clearance, and keeping blade wear under control.

In this defect, the surface stays flat, and a plate is curved along its plane. The responsible conditions include strip width, thickness, material strength, and previous cold rolling direction. The best way to reduce crooking is to use a smaller shearing angle and performed-cuts along rolling direction. Guillotine shear is another condition where blade ram supports its ends instead of the entire length.
Even during the shearing process the blade will become crooked because of the cutting force and will tend to open in the center. The best solution is to choose a shear with adjustable blade pads to keep it perfectly liner. You can opt for ‘Amada shear blades’ as they come with these specifications.
In such a situation, the metal is no longer flat as this effect results in bowed sheet metal. Generally, it is related to cutting angle and plate strength. The best way to reduce this is by using a smaller shearing angle and hold the sheet metal with back support.
Does your shearing blades have experienced such defects? Amada Replacement Parts help you to avoid such types of defects for a period of time with their high tech functionalities. Although the regular maintenance and above-mentioned steps would help you to eliminate the shearing deficiencies.

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Steven Glassner

About the Author

Steven Glassner
Joined: January 10th, 2018
Articles Posted: 91

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