Precisioncareforhigh-speedspindles.doc

Precision care for high-speed spindles High speed spindles are application specific, sophisticated, delicate and expensive. Here is how one manufacturer and supplier ensure high-speed spindles are optimally designed for their applications, and users know how to get the performance they expect while protecting their spindle investments. A 3-mm ballnose cutter re-roughs a 50 Rc H13 toolsteel mold at 15,000 rpm and 120 ipm. The capability of spindles to go fast is dictated by the dynamics of their bearings. The goal of spindle manufacturers is to design with the largest bearings possible, based on spindle speed, to provide maximum stiffness for the application. The faster spindles rotate, the smaller the bearings and spindle shaft must be. That results in decreasing spindle stiffness that imposes limitations on the size, type and length of cutting tools that can be used with the spindle. Also, as speeds increase, available spindle torque decreases. A do-it-all spindleMold and die shops want to maximize all of the features of a spindle: torque, power and speed, especially with medium-and largesized machines. Steven A. Ortner, president of Absolute Machine Tools Inc., Lorain, Ohio (),?a distributor of CNC machine tools, says the desire for incorporating all of those features leads to an integral, or motorized, spindles that incorporate the motor within the unit. Integral spindles use the spindle shaft as the rotor and the spindle housing as the stator for the electrical motor that drives them. We feel integral spindles are a must to produce the fine finishes required in hard milling mold and die work, Ortner says. The majority of large machines his company builds for mold and die applications are equipped with 15,000 rpm HSK-A100 integral spindles manufactured by Weiss Spindle Technology Inc. of Mentor, Ohio (). Integral spindles produce low levels of vibration and have the best thermal stability with little thermal deformation of all spindle types, and are rec