How Sheet Metal Cutting / Shearing Works in Metal Fabrication

Blog | July 31st, 2020

Metal fabrication utilises three different cutting processes to separate or remove material from a piece of stock metal material. These cutting processes are capable of fabricating metal products out of specific types of cut. Some of these processes even produce an open path that separates a portion of the material, while others generate a closed path that can be cut to remove certain parts of the material.

Working Principles of Sheet Metal Cutting

Metal fabrication processes use a shearing force to generate enough shear stress. When the stress in the sheet metal exceeds the ultimate shear strength, then the said material will ultimately fail and separate at the location of the cut.

For the metal fabrication or cutting process to work, two different tools must be placed between the sheet metal. One of the tools is placed above the sheet metal, while the other tool is situated under the subject material. The above tool delivers a quick downward movement to the sheet metal and meets the lower tool. Between the edges of both tools rests a small clearance that enables the fracture of the sheet metal. Usually, this small clearance has around 2 to 10% of the material thickness, which typically depends on the cutting process, the material, and the sheet thickness.

As the cut progresses, the shearing effect on the material changes and becomes more visible on the edge of the sheet metal. Once the punch or blade touches the surface of the sheet metal, the clearance between the tools then initiates the deformation of the sheet and the rollover on its edge. As the tool goes through the sheet further, the cutting process results in a vertical polished area on the material.

The final blow on the material happens when the shear stress is too great and that the material breaks at an angle. A small burr will consequently form at the edge of the sheet metal.

Types of Sheet Metal Cutting Processes

One type of sheet metal cutting process is shearing. It is a cutting process that generates straight-line cuts or shears in separating sheet metal with the help of a shear machine. This type of cutting process is typically done to cut a sheet parallel to an existing edge. Give its main purpose, companies would use shearing as their go-to metal fabrication method when cutting sheet stocks into small sizes that will be used for other processes.

Another type of sheet metal cutting process is blanking. This cutting process happens when a piece of sheet metal is removed from larger sheet metal through the application of a great shearing force. The part removed from this process is typically the desired part. The whole blanking process requires a blanking press, sheet metal stock, blanking punch, and blanking die. Industries use blanking when cutting parts in 2D shape and simple geometries that can be used for gears, jewellery, and watch.

The third sheet metal cutting process that is maximised by industries today is punching. This metal fabrication process removes a piece of material from the sheet metal through the application of a great shearing force. Punching can be similar to blanking, except that the removed material comes from the holes and cutouts. The holes or slots from the sheet metal is the desired part, and they usually made from geometric shapes. Punching works effectively with a punch press, sheet metal stock, punch, and die.

Understanding the working principles of sheet metal cutting or shearing can help you initiate the said process effectively. For more information about sheet metal fabrication and its processes, just give us a call at McKean’s Sheetmetal Fabricators.

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