ABRASIVE WATERJETS CUT THROUGH TOUGH MATERIALSMachine and Tool Blue Book - March, 1990 |
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Waterjet cutting can reduce the cost of producing parts from difficult-to-machine materials by reducing scrap, eliminating heat-related defects and lowering milling costs. Implementation of new technologies can be frustrating and time consuming. Much of the credit for turning ideas into reality must go to the machine operators, technicians and engineers, whose experience and ingenuity bridge the gap between theory and practice. Five years of experience in abrasive waterjet cutting has given Creative Edge Corp., Fairfield, Iowa, and its employees knowledge not only of metals, but also glass, plastics, composites and ceramics. The company was recently spun off from CGI Industries, Rock Island, IL, a manufacturer of waterjet-cut-ting equipment. Having participated in the development of abrasive waterjet machines and functioned as a job shop, the company has experience in the application of abrasive waterjet technology to a variety of manufacturing problems. The cutting power of the abrasive waterjet comes from combining a garnet abrasive and water, pressurizing it to 55,000 psi and releasing it through a sapphire jewel with a 0.009- to 0.18-inch orifice. The mixture of water and abrasive comes out of the focusing nozzle at 2.5 times the speed of sound. The high-pressure stream pierces and cuts materials up to 10 inches thick, leaving a 0.032- to 0.062-inch kerf. The cutting speed varies from 200 inches per minute down to one inch per minute, depending on the type of material and its thickness. Tolerances as close as 0.010 inch can be maintained in production environments. Edge quality varies with speed and grit size, leaving smooth surface finishes ranging from 125 to 250 rms. Slower cutting speeds result in straighter, smoother edges. |
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| Abrasive waterjet cutting complex nested parts from laminated material. Unlike traditional heat-based methods, waterjet cutting produces a clean, smooth edge with no delamination or heat distortion. | |||||
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Jewel, nozzle and grit size, in combination with feed rate and water pressure, determine cutting speed, edge quality and tolerances. Tom Black, production manager at Creative Edge Corp., explains that "setting up a project requires input from our historical records, since many of the published tables of cutting speeds do not correspond to our experience on the floor. Programming estimates for intricate cuts and feasibility verification on new projects are required from our programmer and chief operators. Also, test cuts may be required on materials supplied by the customer for verification of edge quality and tolerances." The company does waterjet-cutting contract work for companies with products ranging from steel machinery components to titanium hip stem blanks, demonstrating the versatility of the process. For machinery manufacturer the company cuts 3/8-inch stainless steel leavers. The edge finish that the process creates is adequate for the outside of the part without additional finishing or deburring. The center oval hole tolerances are less than 0.10 inch. Therefore, the hole is cut smaller and milled into tolerance, using standard precision milling techniques. When flame cutting was used on the part, extensive finishing was required to remove slag and smooth the heat-tempered edge of the part, which then required deburring. Waterjet cutting reduces the time spent producing the part and reduces the amount of milling to only one operation on annealed steel. |
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