Teoria in preparazione alle domande a crocette

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ACCESSO RAPIDO: →Waterjet →ASMF →MJP →Advanced Machining →Laser →AM processes →EDM WATERJET • Waterjet is not as fast as laser cutting on thin metals, but it becomes competitive at high thickness (20-30 mm and more) • Drilling different materials: o Composite materials suffer delamination in the first stages (sometimes we pre-drill mechanically); o Glass requires low pressures (e.g. 70Mpa) to reduce thrust force. After it can be increased; o Metals drilling time increase with thickness. When the drilling time is too long, a diameter increase is expected due to the water reflection in the blind-hole condition; • A typical defect you expect in hole drilling is to have a round edge at the entrance • Direct pumps (no intensifier) have a pumping factor of 10 (instead of 20). They are less reliable, as seals are subjected to higher velocities. When stopping cutting operation, the water flow rate has to be deviated, which is not fast and reliable due to component wear. • Main features of PWJ: o 200-300 Mpa o 0.08 mm < d0 < 0.2 mm o 700 m/s jet velocity • Orifice inserts: o Sapphire – working life 100h => $ o Diamond – working life 300h => $$$ (if total price comparable, better for lower downtime) • Main abrasive requirements: o High hardness o Homogeneous dimensions o Low higroscopity • • Greater air flow rate in AWJ reduces the venturi effect and so the speed of the abrasive particles flowing to the mixing chamber. For this reason, we should NOT exceed with increasing the hose diameter. • the air sucked enlarge the diameter of the jet and reduce the quality of the process • 2 reasons to reduce the actual vabr o Finite tube length o Frictional losses • Regarding AWJ material interaction o Brittle materials are better removed when abrasive particles impact the surface at high…