Manufacturing

Overview Of Sheet Metal Cutting Operations

In the modern world, there are lots of kinds of examples of sheet metal parts. From the automotive industry to household appliances, sheet metal parts are commonly used. So, sheet metal production techniques are extensively used in various industries. 

Sheet metal shearing machine(Image Source: https://tampasteel.com/benefits-of-metal-shearing/).

Sheet Metal Cutting Processes

Sheet metals are processed in various ways. One of these ways is sheet metal cutting operations. Various kinds of sheet metal parts are produced with sheet metal cutting processes. 

Sheet metal cutting illustration(Image Source: Mikell P. Groover; Fundamentals Of Modern Manufacturing, 4th edition).

In most basic aspects, sheet metal cutting takes place shearing of a sheet metal strip with the use of cutting blades. One of these cutting blades generally makes a reciprocating motion to cut the sheet metal strip. This moving blade is called as ‘punch’. And the stationary blade is called as ‘die’. There is a small clearance between punch and die, at the easy cycle of motion of the punch, the sheet metal strip is cut. 

If we take a closer look at the cutting phase of sheet metal strips in more detail, the shearing action starts with the plastic deformation of the strip. While the punch is moving forward, penetration of the sheet metal strip occurs. After the required motion of the punch, fracture occurs. 

Also, if we take a closer look at the sheared edge of the sheet metal strip, we will see a characteristic edge like in the figure. You can see the rollover, burnish, fractured zone, and burr shapes. 

Types Of Sheet Metal Cutting Operations

Blanking and punching(Image Source: Mikell P. Groover; Fundamentals Of Modern Manufacturing, 4th edition).

All the sheet metal cutting operations may depend on the same principles. But according to the process parameters and produced part shapes, they can be classified into different types of operations. 

Shearing

The first type of sheet metal cutting operation is shearing. This is the most classical type of sheet metal cutting operation in which there is punch and die. 

Blanking

The difference in blanking operation is that all the surrounding of the sheared part is cut from stock. All the edges are cut. In here, the strip is scrap, the produced part is called a blank. 

Cutoff and parting(Image Source: Mikell P. Groover; Fundamentals Of Modern Manufacturing, 4th edition).

Cutoff

The cutoff is a sub-type of the shearing operation in which all the strip is used to produce cutoff parts without any scrap or very little scrap. 

Parting

Parting is also another sub-type of shearing in which parts and scraps are produced in a specific pattern.

Slotting

Slotting is a type of blanking operation in which rectangular slot shapes are produced. 

Perforating

This is also another blanking type in which perforated sheet metal geometries are obtained. In here, small blankings are scraps. 

Slotting, perforating and notching(Image Source: Mikell P. Groover; Fundamentals Of Modern Manufacturing, 4th edition).

Notching

From a side of a metal strip, small pieces are cut in notching operations to obtain desired strip shapes. 

Trimming

The excessive sheet metal sections are cut with trimming operations. In other metal processing operations, trimming operations are used. 

Shaving

Shaving operations are used to obtain more accurate dimensional sizes by using very small clearances. 

Importance Of Clearance In Sheet Metal Cutting Operations

As we stated above, clearances are very important in sheet metal cutting operations. Clearance means the distance between die and punch. In an ordinary sheet metal cutting process, clearance must be designed to obtain desired cut section. 

If the clearance is small, the cutting forces will be higher and double-burnishing may occur. And if the clearance is very high, excessive burrs can occur. 

So, an engineer must design the clearance properly to obtain the desired results. 

Conclusion

Fundamentals of Modern Manufacturing: Materials, Processes, and Systems

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