Advantages of AWJ
In the early 1980s, AWJ machining was considered as an impractical application. Today, state-of-the art abrasive jet technology has grown into a full-scale production process with precise, consistent results. There is a similarity between wire EDM and AWJ machining. Both cut complex contours with a kerf. The diameter of the jet is three times as thick as the wire EDM, but it fits right into the jobs that do not require the same tolerances as wire. AWJ machining can be used to complement wire EDM. AWJ machining costs only onequarter that of wire EDM. It can be used on hot rolled steel successfully. Surface impurities reduce cutting speeds and may cause the wire to break. AWJ is able to ignore many material aberrations that would cause wire EDM to lose flushing.
Some of the non-conductive and reflective materials such as quartz can be especially difficult to cut because they have a tendency to fracture. AWJ cuts various part configurations of these materials without any problem. Creating prototypes are more economical than wire EDM. Both plasma flame and laser cutting leave behind a heavy crust that is extremely hard and these methods do not achieve the accuracy on a 13 mm thick (or thicker) plate that AWJ can. Modern AWJ machines enable the cutting of materials which are dif- ficult for conventional machining such as Inconel alloys, titanium, and composites with a tolerance of ±0.05 mm. They are also widely used for easily cut materials such as mild steel and aluminium. The surface quality of different materials obtained with various speeds is given in Table 2.
It is possible to achieve close to EDM tolerances with AWJ. Because of the cutting process, the surface always looks as though it has been sandblasted so it is not possible to create a mirror finish. AWJ can cut materials ranging from 1.6 to 300 mm in thickness with an accuracy of ±0.13 mm. Holes up to 150 mm deep can be drilled at any angle with tolerances as tight as ±0.03 mm. The minimum hole diameter that can be machined with AWJ is 0.2±0.03 mm (product information of Berkeley Chemical Research Inc., USA, 2001). Traditional cutting techniques are not effective on honeycomb structures as their structure is too fragile. These materials are machined successfully with AWJ. Parts can be nested very close to each other in order to maximise material utilisation. In some cases, pieces can even share the same cutting line. The process does not generate heat as in other processes, so there are no heat-affected zones. This is useful for cutting materials for which heat may change their properties. Unlike machining or grinding, AWJ does not produce any dust or particles that are harmful if inhaled. The process can be easily automated. AWJ equipment is much lighter than equivalent laser cutters, and the cutting head can be mounted on an automated robot. This reduces the problems of accelerating and decelerating the robot head as well as requiring less energy.
AWJ cuts materials with speed not pressure. The cutting power is obtained by means of a transformation of hydrostatic energy (400 MPa) into a jet of a sufficient kinetic energy (nearly 1000 m/s) to disintegrate the material so fixturing is simple and it is easy to hold the workpice in place.