Built-Up Edge

The method of adhering or welding microchips or powdered particles present during machining to the rake face of the cutting tool is called built-up edge (BUE). During the machining operation, there are always a certain number of microchips or powdered particles that will be produced. Also, during machining, according to the first law of thermodynamics, whatever the energy supplied will be converted into heat energy, and due to this, the rake face of the single-point cutting tool experiences high temperature. When the microchips or powdered particles are moving the rake face of the tool, they will get exposed to a high-temperature environment, and some of the particles may get adhered or welded to the rake face of the tool, called a built-up edge.

The factors which influence the formation of built-up edges are:

1. Speed of the machining: During machining with high speed, the time available for adhering microchips will be less, and the formation of a built-up edge can be neglected.
2. Uncut chip thickness: As the uncut chip thickness increases, the force induced during machining will increase, which will increase the power consumption and heat generation in the machining process. Hence, the chances of adhering to microchips will be increased.
3. Back rake angle: A reduction in the back rake angle will increase the forces in machining and heat generation, and hence, the chances of formation of BUE will increase.
4. Use of cutting fluids: If cutting fluids are used during machining operations, whatever heat is generated during machining will be carried away by the cutting fluid, reducing the heat available for adhering and eliminating the formation of BUE.

Due to the formation of the built-up edge, the following effects will take place:

1. Whatever wear takes place on the rake face, only BUE will wear out; hence, the tool life will be increased.
2. Due to the formation of BUE, the surface finish of the rake of the tool will get damaged, and it will increase the friction at the chip tool interface. Forces and power consumption will also increase during machining operation.