Fine Blanking

What is fine blanking?

Fine blanking is a process that is fulfilled with the interaction between the punch and the dies on a press machine, in order to create crack and burr-free edges around the final products, and allow the parts that are cut off to be reused.

Similar to punching or piercing, the applications that manufacture the components of the automotive, aerospace, energy, or electronic industries would also apply fine blanking as a method to pursue the optimal quality of the products.

In the fabrication of metals like carbon steel, stainless steel, or aluminum, etc., which can be presented as either thick or thin like sheets, there are various methods to create holes by removing parts of the materials on the workpieces depending on the requirements of the customers. While with different workpieces that are required to be machined, the methods that are adopted are different as well.

For the thicker workpieces, drilling or boring would be more suitable as these methods create holes by penetrating the workpieces from the surfaces of one end to the middle, or even the other end. In contrast, for the thinner sheet metals, the above methods are not that necessary to be used. Due to the property of the thickness of workpieces, in the fabrication of sheet metals, methods such as punching or blanking would rather be used.

Blanking, one of the methods that are applied for shaping the sheet metals, removes materials from the workpieces by providing the compressive force instead of directly cutting through them. This should also take the yield strength and the tensile strength of the metals being machined into consideration, which would be discussed in the latter paragraphs.

Fine blanking vs. punching

Fine blanking and punching are the two similar counterparts but apply different principles in the machining processes. Both of them are available for the fabrication of sheet metals, since they both provide the compressive force on the workpieces to create holes instead of directly cutting through them.

● Compatible materials
Despite the different terms that they are called, with the same purpose of the fabrication of sheet metals, the materials that are shaped or formed by fine blanking and punching must be similar as well, like the carbon steel, stainless steel, or aluminum, etc.

● Principle
Although these two methods are adopted following the same purpose, the working principles of them are actually opposite. During the interaction between the punch and the dies, there would be parts that fracture after the compressive force of the punch is beyond the tolerance of the metals’ tensile strength. 
When punching is the applied method, these parts would be discarded. Instead, they can be reused when fine blanking is rather applied.

● Tooling
As far as we know, the most obvious difference between fine blanking and punching is the principles of them, and the tooling that these two methods use is basically the same, but with slightly different features.

In addition to the punch, dies, and ejector that both of them would apply during the processes, on the machine of fine blanking, it is additionally equipped with a guide plate with V-ring, which is used to fix the workpieces and keep them flat when the punch and dies work on them.

How does fine blanking work?

To fabricate sheet metals with fine blanking, the machine that would be used consists of a blank punch, a guide plate with V-ring, die plates, and an ejector. Through the interaction between the V-ring force, cutting force, and counter force, the processes can be simply divided into three steps, including positioning, cutting, and conveying.

1. Positioning
When a workpiece is fed between the blank punch and the die plate, the guide plate as well as the punch would move downward in order to clamp on the workpiece, and the V-ring on the two sides of the guide plate also help keep the workpiece in place during the processes.

2. Cutting
As the machine is initiated, the workpiece would be compressed with the V-ring force that is given from above, and the target part would be cut and ejected with the cutting force and the counter force that are given at the bottom of the machine.

3. Transmitting
Since fine blanking usually works on the long strips of sheet metals, these sheets are machined with transverse orientation, which means that the parts that are supposed to be removed on the workpieces are cut and ejected one beside another. 

In other words, as the punch and the die plate interact with each other, the workpieces would be transmitted in transverse direction, and the blanking work is completed with the tooling on the machine cuts on the workpieces repeatedly

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