During the metal cutting process, the tool removal of small metal formation from work piece is called chip.The types of chips in metal cutting depends upon the work material and method of machining process obtained.
Types of variable considered for chip formation provided:-
- The material properties of ductility and brittleness.
- Cutting death
- The angle of tool like as rake angle.
- Feed rate of rake.
- Surface finish of work material required.
- Cutting fluid used in machining
- Coefficient of friction obtained in between tools and chip.
The types of chips in metal cutting:-
- Continuous chip
- discontinuous chip
- Continuous chip with built up edge
During the metal cutting of ductile material, a continue ribbon (Chip) is provided due to pressure applied on the tool cutting edge in compression and shearing. This type of chip having long coil formation and same thickness throughout the length. The requirement of this type of chip, give more advantages in the work metal, tool and machine. The most advantages such as good surface finish of work material, the tool life will be improved and require less power consumption. The Chip disposal is not easily and surface finish on work metal affected.
How to get continuous chip formation during the metal cutting process? Follow the below condition,
- Depth of cut in smaller
- Long rake angle
- Sharp cutting edge
- High cutting speed
- Using proper cutting fluid
- Low friction to be maintained in between tool face and chips.
Discontinuous chip (or) segmental chips:
The discontinuous chip provided by using brittle material such a high Carbon Steel, bronze ,Grey cast iron at low speed on cutting without any fluid. when the friction existed between tools and chip. During the machining of cutting, the brittle material lacks its ductility. So it is necessary for plastic chip formation. Also it will be lesser. In this formation named as Discontinuous chip. If continuous chip, the shearing of metal will occur at cutting tool head for continuously without any fracture. In discontinuous chip, Ruptures will occur intermittently. This type of chip having small length. so easily handled and easily disposed off. It also not affect on the surface finish of work material.
The formation of discontinuous chip require follow below condition:
- Depth of cutting is higher
- Cutting speed will be low
- Excess amount of cutting fluid
- Machining the brittle material
- The rake angle will be small
- The cutting of ductile material at low feeding with small of rake angle
Continuous chip with build up edge:
During the metal cutting process the interface pressure and temperature will be high in quickly. Also the high friction presented in between chip and tools. In this reason the material go to welding process itself to the tool face in near of nose. It is known as “build up edge”.
The built up edge formation in continuous chip is a transient and not stable of phenomenon. The accumulate build of chip metal will break away, the part adhering to the chip underside and path to the work piece. That process give to raise the poor surface finish on the machined surface and accelerate wear on tool life. The formation of chip have some advantages like as the rake face protected from the wear due to chip move and action of heat. So it may be increase the tool life.
If want to formation of this continuous with build up, to follow the blow condition:
- Small rake angle
- Low cutting speed obtained
- Large amount of cutting thickness
- Coarse feed
- insufficient cutting fluid