Direct-Drive Workhead

Kellenberger Kel-Varia CNC-controlled, universal cylindrical grinding machines feature a robust and rigid direct-drive workhead to provide reliable and accurate grinding of large, heavy parts. A powerful torque drive allows heavy parts to be accelerated quickly and precisely and braked with no backlash during bi-directional movements for increased productivity. A large spectrum of parts and a wide range of geometries can be processed using combinations of cylindrical grinding, OD and ID out-of-round grinding, thread grinding, and jig grinding all in one setup. Advanced C-axis (ultra-high resolution) operations allow precise grinding of grooves and satellite, as well as centering bores.

The direct-drive workhead has a variable spindle speed from 1rpm to 500rpm (with Heidenhain control), with a maximum weight capacity of 750Nm (300kg / 600 lb) with an option of ±60 second micro-correction for easy adjustment of cylindricity.

For between-center work, a heavy-duty Morse taper 4 tailstock with nitride coated sleeve runs in sturdy ball-bush bearings to achieve high rates of in-feed, even with heavy parts. A sleeve retraction of up to 50mm is pneumatically or hydraulically operated. Maximum weight is 250kg/500 lb between centers.

The C-axis option of interpolating the X- and C-axis makes it possible to use the cylindrical grinding machine for non-round shapes, such as polygons, free contours, and eccentric forms. The rotary encoder with a resolution of 0.00001° is installed directly on the workhead spindle. All standard grinding cycles work on cylindrical and non-round grinding as well, including the handwheel release for the X-axis. Powerful motors and a fast control system ensure highly dynamic non-round and thread grinding operations. Jig grinding capability offers a complete part in one setup, eliminating the additional process that might have been done on a second grinding machine.

The swiveling hydrostatic, direct-drive B-axis provides simultaneous interpolation of the X-, Z-, and B-axis with easy, simple programming resulting in a resolution of 0.00002°. This CNC controlled B-axis allows complete grinding of traditional and complex parts in a single setup.

Precision hydrostatic guideways provide frictionless grinding, maintaining accuracy during the machine’s lifetime. The hydrostatic guides for the longitudinal slide movement (Z-axis), wheelslide in-feed (X-axis), and swiveling B-axis provide the basis for the machine’s extreme accuracy. Benefits include shorter spark-out times and zero backlash during bi-directional movement for reduced total grinding time, less wear on CBN or diamond grinding wheels, and improved surface finish. There is no stick-slip effect, and increments as small as 0.1µ can be traveled without a problem.

Hardinge Inc.
Elmira, N.Y.
www.hardinge.com