AWJ Cutting of Thick Materials
An article written by Hashish* presented interesting results on precision cutting of thick glass, titanium, and steel with abrasive waterjets (AWJ). Here are the highlights.
Pictures of some examples of really thick materials cut with AWJs were shown, including 450 mm (18”) thick aluminum (cut in single passes), 300 mm (12”) thick glass (cut in two passes from top and bottom), and 1 meter (39.4”) thick concrete (cut with penetrating tool).
Jet trial-back, taper, and surface finish were identified as the three main characteristics of AWJ cuts. Results of 14 cutting tests on a 300 mm thick sample of titanium with different abrasive flow rates and cutting speeds were presented. The trial-back curves match the prediction of a universal AWJ kerf equation. The kerf width profiles show some similarity to kerf width profiles predicted with a kerf shape model of pure waterjets. This pure waterjet model with some modifications was applied to AWJs. By tilting the nozzle forward or sideway can minimize the trial back and taper.
An equation to predict proper mixing tube length for achieving a certain mixing efficiency was also presented. The following table (Table 2*) shows predicted mixing tube lengths for a mixing efficiency of 90% (i.e. particle velocity at 90% of its maximum possible velocity). According to this table, longer mixing tubes are required with larger particles and shorter mixing tubes can be used with higher abrasive flow rates.
Examples of AWJ nozzles used for thick material cutting were shown. Mixing tubes for these nozzles were 300 mm (12”) and 450 mm (18”) long (pictures showing multiple sections joined together for each tube). Two abrasive inlets were used to feed abrasive into each nozzle. As an example of work done with these nozzles, a hexagonal honeycomb shape with 2-mm thick struts was cut out of a 300 mm thick glass block. A tilting cutting head was used to correct for trial-back and taper.
* Hashish, M. (2004) Precision cutting of thick materials with AWJ, Proceedings of the 17th International Conference on Water Jetting, Colin Gee (Ed.), Proceedings of the 17th International Conference on Water Jetting -- Advances and Future Needs, Mainz, Germany, 7th - 9th September. p. 33-45.
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