Interest in large machine tools continues to grow in the United States and elsewhere in North America, especially because oversized workpieces are prevalent in the wind turbine, airframe, oilfield and rail industries. One machine tool builder active in these industry segments is Zayer, a company headquartered in northern Spain but represented in the North American market by Republic Lagun Machine Tool Co. (Harbor City, California). Although Zayer specializes in large CNC bridge- and gantry-type machines, it also offers traveling-column models.
According to Joseph Bezic, president of Republic Lagun, potential users evaluating a large machine should pay particular attention to the configuration of the worktable. That’s because part handling, rather than machining time, is a major factor in the overall productivity of large part processing. The point is to move large parts as little as possible while getting the most out of the flexibility and capacity of the machine’s worktable, Mr. Bezic says.
For example, the Zayer 30KCU and 60KCU models, available with five-axis machining capability, are traveling column machines with table configurations that can be customized for the user’s application. In fact, Mr. Bezic says, Zayer’s engineers are adept at customizing tables because most installations of these machines in Europe have involved some degree of customization. One of the main advantages of the traveling-column type machine is that it is possible to incorporate a wide variety of worktable features such as built-in rotary tables, floor plates, right-angle plates and other options. Generally, these machines are configured as floor-type models; that is, the table is level with the surrounding floor surface so that parts can be loaded by forklift or overhead crane.
Because pallet shuttles for machines and workpieces of this size are impractical, the ability to divide the worktable into separate machining zones is key to high machine utilization. The builder recommends a table that is sized to enable the establishment of multiple zones. Thus, one zone is always available for machining, while the other zones are occupied with set up and/or tear down procedures. The column of the machine simply moves to whichever zone is ready for production. For safety sake, zone boundaries are protected by laser beams to prevent intrusions in adjacent zones.
Of course, as Mr. Bezic is quick to emphasize, volumetric accuracy is especially important in large-part machining because the machine tool is likely to be active throughout its entire work envelope. For this reason, he says, the KCU series of traveling column machines are equipped with a dual-function guideway system with fluidic axis support. These machines are also equipped with hardened and ground box guideways; cylindrical roller packs for the X, Y and Z axes; rack and dual motor-driven pinions on the X axis; ballscrews with double preloaded nuts for the Y and Z axes; optical linear scales on all three lineal axes and refrigeration for the gearbox, ram and spindle head.
Machines in this series have an X-axis (longitudinal) capacity ranging from 118 inches to 944 inches (3,000 to 24,000 mm), Z-axis (vertical) capacity ranging from 59 to 196 inches (1,500 to 5,000 mm) and Y-axis (cross) capacity ranging from 49 to 63 inches (1,250 to 1,600 mm). A universal spindle head with 360,000 positions is a standard feature, but head changing capability also is available because the company offers an assortment of heads designed for specific applications. Spindle taper is ISO 50 or BigPlus CAT 50.
Mr. Bezic also notes that Zayer has been particularly successful serving the high speed and light rail industries in Europe. The company, he says, has the expertise to guide the manufacturers in America who are anticipating resurgence in intercity and commuter rail lines. This resurgence is in response to energy and environmental concerns. Zayer machines are also well represented among Europe’s wind turbine, ship building, military and aerospace industries.
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