6585883 waterjet cutting seminar

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Introduction Wat erjet Cutting (WJC) is a non-traditional method in which a high velocity jet is used to machine a material. Often it is assisted by abrasives and & is know n as Abrasi ve. Wate rjet Cutting (AWJC). The process offers a wide range of advantages. It is omni-directi onal and ena bles fully aut oma ted 3-D cutting and has unlimited creat ive potential. The resulting kerf width is small and hen ce improved yield . Forces involved are minimum and non-crushed edges even on very soft materials. Work hardening is eliminat ed and heat affec ted zone (HAZ) is absent. Environme nt pollution is minimised since airbo rne dust and fume s are absent. No deburring is require d on the processed part. It is a v ersatile pro cess an d can cu t a varie ty of materials. However , initi al cost of equ ipme nt is high . In additi on excess wav ines s/st riat ions on side wall surface may limit the depth of cutting in practice.. STRUCTURE AND MODE OF OPERATION Fi gu re 1 sh ows a schema ti c di ag ram of AWJC. Wat er is pressurised to abo ut 400 MPa. A high ve locity jet of 900 m/sec is obt ained when the pressurised water passes through a  nozzle, usually of sapphire, of diameter 0.6 mm. Abr asi ves delivere d fro m a fee d sys tem is precis ely controlled for its flow . The se particles are entrained by the Waterjet stream and energy is transferred from water to the abr asiv e parti cles . The res ultin g A WJ is direc ted on to th e targe t. Alte rnat ely abrasive suspens ion jets are used, in which premixing of abrasives with water is done to achieve their susp ension (fluidise d). These abras ive suspension jet s are found to be economical. The distance between the target and the tip of the nozzle, Known as stand- off distance , is found to be critical in machining op erations. Max imum material removal takes place at optimum stand-off distance. A catcher tank traps the unspent energy of the jet and the eroded particles. Large catcher tanks are used, or compact tube like catchers that move with nozzle are used for Omni-directional cutting. Typ ical kerf width ma y rang e between 0.1. and 0.75. mm. Tolerances achievable are around 0.025 mm. The side wall of the cut surface is found to have two distinct zones, a smooth upper zone and a wavy bottom zone. Control of operating conditions during cutting ( jet pressure, abrasive flow rate and jet traverse rate) can be used to modulate the striations on the cut surface. However , motion control and vibrations due to rack/pinion that may be used in the system could lead to striations and

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8/8/2019 6585883 Waterjet Cutting Seminar

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