Gear Production

MAR 2015

Gear Production

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18—GEAR Production Supplement F E A T U R E waterjet machining is a "cold cutting" process that keeps workpieces from experiencing the mechanical and thermal stresses that often occur with conventional techniques, thereby eliminating any secondary stress-relieving processes. In addition to new gear production, abrasive waterjet machines can be used in gear repair operations to avoid the cost of producing a completely new gear. This repair capability is especially benefcial when it comes to giant industrial gears. With an abrasive waterjet machine, shops can cut away old or damaged gear teeth and cut special ftting joints that allow the new replacement teeth—also made on the same waterjet machine—to simply "click" into place with minimal or no welding. When not in gear manufacturing or repair mode, shops don't have to worry about an abrasive waterjet machine sitting idle. Unlike conventional machining techniques, the high level of versatility that comes with an abrasive waterjet machine makes it possible to cut an automotive part out of steel, then easily transition to processing titanium for an aerospace component, for example. Equipment Hardware When it comes to selecting the right abrasive waterjet machine for gearmaking operations, it is important to note that such equipment ranges from very high-power machines with large nozzles for sizeable kerf widths to lower-power machines with miniature nozzles for cutting intricate part geometries. A typical waterjet cutting nozzle cuts a kerf width of approximately 0.030 inch (0.75 mm). When cutting thick materials, however, a 0.042- inch (1-mm) or 0.048-inch (1.2-mm) nozzle might be used to generate a wider kerf. For tiny, complex work, there are some nozzles that produce much smaller kerfs. The type of pump used with an abrasive waterjet machine determines the level of effciency shops can achieve in gear production. A direct-drive pump, which uses a crankshaft to move the plungers that pressurize the water, is much more effcient than an intensifer pump, which relies on power-consuming hydraulics. Through this increased effciency, direct- drive pumps such as those used on Omax machines deliver more horsepower at the cutting nozzle than intensifer designs at any pump power rating, regardless of pressure. As with all cutting processes, material removal rates are a function of the power put into the cutting surface. Overall, direct-drive pumps create a more Complex nonstandard gear geometries are simple to cut with an abrasive waterjet. Gear repair is often more cost effective with abrasive waterjet, such as with this 4-inch-thick wind turbine gear that is over 5 ft. in diameter.

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