Types of Chips in Machining
Conventional machining operation always produces some chips. The nature of the chips depend on
- properties of the workpiece material
- cutting environment
The cutting tool has to overcome the resistance of the work material to give it a desired shape. So cutting tool must be more harder, wear resistance than the w/p. The main reason for the chip formation is due to the deformation by shear stress. This stress is applied to metal lying ahead of the cutting edge of the tool . Four main types of chips in machining process are –
- Discontinuous Chips
- Continuous or Ribbon Type Chips
- Continuous Chip Built-up-Edge (BUE)
- Serrated Chips
Main reason of discontinuous chip formation is the deformation due to repeated fracturing. Hard and brittle metals like C.I , bronze and brass are prone to produce discontinuous chips. These are small pieces which are loosely connected to each other.
Continuous or Ribbon Type Chips:
In this type of chip formation the chips are bonded together and form long coils. These are continuous chips which undergo continuous plastic deformation. There isn’t any fracture ahead of the cutting edge of the tool. The inside part of the chip shows steps due to intermittent slip. The outside is smooth.
Continuous Chip Built Up Edge:
These are very similar to the ribbon type chips but it is not as smooth as those. These chips are seen in the workpieces with poor surface finish. These chips protect the cutting edge from wear because of the chips movement. The tool life increases by the action of heat.
These are semi-continuous . They posses a saw tooth profile. The main reason reason for this appearance is the alternating high shear strain followed by a low shear strain. These chips are seen metals like titanium alloys, austenitic stainless steel and nickel based super alloys which are very difficult to machine. When materials are cut at very high speed these chips are likely to be formed.
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