Chip Shape and How to Control it?

In the process of CNC machining, a chip is the most common material to be removed. This material has various forms. Although the chip is a waste for processing, its influence on the chip should be paid attention to.

Types of Chips:
Due to the different workpiece materials and cutting conditions, the shapes of chips generated during the cutting process are various. When strip-shaped chips are formed, the cutting process is the most stable, the fluctuation of cutting force is small, and the roughness of the processed surface is small. Cutting force fluctuations during cutting are greatest when granular chips are formed. The type of chip can be transformed with the change of cutting conditions. For example, under the condition of nodular chip formation, if the rake angle is further reduced, or the cutting thickness is increased, granular chips may be obtained. Conversely, increase the rake angle and reduce the cutting thickness to obtain banded chips.

1. Ribbon chips: The most common kind of chips. Its inner surface is smooth and its outer surface is hairy. When processing plastic metal, such chips are often formed under the working conditions of small cutting thickness, high cutting speed, and large tool rake angle.
2. Nodular chips: Also known as crushed chips. It has a jagged outer surface and sometimes cracks on the inner surface. Such chips are often produced when the cutting speed is low, the cutting thickness is large, and the rake angle of the tool is small.
3. Granular chips: Also known as unit chips. In the process of chip formation, if the shear stress on the shear plane exceeds the fracture strength of the material, the chip unit will fall off from the material to be cut to form granular chips.
4. Breaking chips: When cutting brittle metals, due to the small plasticity and low tensile strength of the material, after the tool cuts in, the metal in the cutting layer is under the action of the rake face of the tool without obvious plastic deformation. Under the action of brittle fracture, irregularly shaped chipping chips are formed. When processing brittle materials, the larger the cutting thickness, the easier it is to get such chips.

Chip Control:
Different chip removal situations will be seen in production practice. Some chips are rolled into a spiral shape and break off by themselves when they reach a certain length; some chips are broken into a C-shape or a 6-shape. Some are in the shape of hairpins; some are broken into needles or small pieces, which splash around and affect safety. Some strip-shaped chips are wrapped around the tool and the workpiece, which is easy to cause accidents. Poor chip removal status will affect normal production, so chip control is of great significance, which is especially important when processing on an automated production line.

After the chip undergoes severe deformation in the first and second deformation zones, the hardness increases, the plasticity decreases, and the performance become brittle. During the process of chip discharge, when obstacles such as the flank of the tool, the upper transition surface of the workpiece, or the surface to be processed are encountered, if the strain at a certain part exceeds the fracture strain value of the chip material, the chip will break. The greater the brittleness of the workpiece material, the smaller the fracture strain value, the larger the chip thickness, and the smaller the chip curling radius, the easier it is for the chip to break. The following measures can be taken to control chips.
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Reference: kknews、market-prospects