High Speed Machining

ABSTRACT:

      In conventional machining processes when we go for high speed excessive heat is generated during the chip formation process, which increases the temperature of cutting tool and accelerates tool wear. Conventionally cutting fluid is used to cool and lubricate cutting process. However conventional cooling process has inherent health and environmental problems .In addition to this a process should facilitate longer tool life ,higher cutting speed ,better work surface, less built up edge, easier chip breaking and lower production cost.

      Cryogenic machining is one such process in which above mentioned features are present. Cryogenic machining uses liquid nitrogen as a coolant .Liquid Nitrogen has a boiling point of -199 degree centigrade. It has been observed that at cryogenic temperatures tool materials get harder and stronger.

        A micro nozzle is formed between tool face and chip breaker and LN2 is passed through it. The chip breaker helps to lift chip so that the jet reaches the hottest spot i.e. tool chip interface. At this point LN2 absorbs heat and evaporates producing gas cushion causing lubrication effect. This localized cryogenic cooling reduces the tool face temperature, enhances its hardness, so less wear rate .The lubrication effect reduces friction and tool wear.

      This new cryogenic machining eliminates the built up edge (BUE) problem on tools because cold temperature reduces possibility of chips welding to tool. so the   process will allow high speed cutting with out built up edge.

In addition to varies advantages of the cryogenic machining, the paper discloses the comparison of cryogenic machining with conventional process in the aspects of tool life, productivity, and production cost.

INTRODUCTION:

      In conventional machining processes when we go for high speed excessive heat is generated during the chip formation process, which increases the temperature of cutting tool and accelerates tool wear....