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What is Phoi?

Chip (chip in English) is a layer of material that needs to be removed from the workpiece with the help of a mechanical cutting tool. Therefore, the chip is the processing residual during the cutting process. Chips will have different shapes depending on many factors such as cutting conditions, workpiece material, cutting tools… The material processing process depends heavily on the chip.


Chip forming process


Quá trình hình thành phoi


Chips are formed during the cutting process. Under the action of cutting force from the cutting tool, the metal layer on the front of the cutting tool will be compressed, until the pressure from the cutting tool exceeds the bonding force between the material elements, this metal layer will be detached from the workpiece surface, releasing stress, breaking and sliding from the workpiece surface in the inclined direction. The cutting tool then continues to move and separates further chip elements from the workpiece.


Chips affect the machining process, the larger the amount of chips (machining residue), the more time it takes to cut; at the same time, chips can also cause problems during machining such as chip jams that can damage the cutting tool, workpiece damage, loss of machining time, or chips hitting the machined surface affecting the smooth finish of the surface. detail surface after machining. In different operations and machining processes, with different cutting tools, the amount of chips as well as the shape of the chip removed will also be different.



Types of chips in cutting

There are three types of chips generated during cutting operations: chip chips, stacked chips and wire chips. Below are the details of each of these chips.


Các dạng phoi trong gia công cắt gọt




If the chips formed are discrete pieces of material of different shapes, which are not interconnected or are very weakly bound together, they are called chips.

Shredded chips can be formed by the following factors:

When the workpiece is a brittle material such as cast iron, copper.

Low cutting speed.

Small cutting angle.

Large feedrate and thick chip.

Large depth of cut.

Large friction force between the cutting tool and the workpiece.

For materials that are brittle metals, shavings provide better surface finish, as well as increase tool life. However, if chips form on ductile metal workpieces, poor surface finish and increased tool wear are also observed.



Wire Chips


Wire shavings are chips with a long, unbroken wire shape, the smoothness of the chip surfaces is relatively similar, and there is no or very little serration. Chips of this type are formed by the continuous plastic deformation of the metal without breaking at the front of the cutting edge.

Wire chips can be formed by the following factors:

The workpiece is a material with high ductility and low hardness.

High cutting speed.

The thickness of the chip is small.

Large cutting angle.

Small cutting depth.

The friction between the cutting tool and the workpiece material is low.


Wire chips provide better surface finish, less heat in machining, longer tool life. However, wire shavings, if not handled well, can easily cause chip entanglement, chip entanglement, and affect the machining process and may damage the cutting tool.



Folding chips

Chips are formed with short segments, the side of the chip surface sliding onto the front of the tool is highly smooth, and the opposite side is rough with a serrated appearance. The material elements in this chip form are relatively stable together.

Chips can be formed by the following factors:

The workpiece material has moderate stiffness, little ductility with medium cutting speed.

Or flexible workpiece material at low cutting speed, large cutting thickness and large cutting angle.

In the machining process, the surface quality when cutting out chips is low.



Shrinkage of chips

After the chip is separated from the workpiece due to compression deformation, it will have a shorter length than the cutting length and according to Poisson's law of mass deformation, the thickness will be thicker. This phenomenon is called chip shrinkage, which can be recognized by observing the external appearance of the chip.


Shrinkage coefficient of chip can be calculated by the formula: K=Lo/L

In there:

Lo is the cutting length on the machined surface (the tool travel on the workpiece) (mm)

L is the actual length of the chip (mm).


Sự co rút của phoi



The chip shrinkage coefficient K is always greater than 1. The larger the K-factor, the more the chip deforms, meaning the material's ability to resist slippage is reduced (corresponding to better machinability, ease of machining. labour). The chip shrinkage coefficient determines the plastic deformation value of the material when cutting, the larger the coefficient K, the higher the plastic deformation.


From the shrinkage coefficient of the chip, it is possible to partly assess the strength of the material in the cutting process (machinability), thereby drawing the necessary conclusions and applying reasonable measures to making the cutting process easier.


Above is some information about chips in cutting processing that Golden-tec Vina brings to you. If you have the need to order mechanical processing tools at Golden-tec Vina, please contact us immediately for a free consultation and quote.



Address: 3rd Floor, 134/2A Alley 84/41, 30/4 Street, Phu Hoa, Thu Dau Mot City, Binh Duong Province, Vietnam (75000)

Hotline: (+84) 976063331 (Mr.Cho)

(+84) 965831631 (Mr. Linh)

Email: (Korean) (Vietnam)

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