The Kellenberger Kel-Varia cylindrical grinding machines now incorporate a direct-drive workhead grinding of large, heavy parts.
The CNC-controlled universal grinding series is a product of Hardinge Inc., which emphasized the robust and rigid design of the workhead, making the grinding process both reliable and accurate for critical jobs. Kel-Varia cylindrical grinding machines are designed for grinding large, heavy parts and non-round contours. Three sizes are available, with distance between centers of 600, 1,000 and 1,500 mm and center heights of 175, 225 and 250 mm, respectively.
A powerful torque drive means that production of heavy parts can be accelerated and braked quickly, and precisely, with zero backlash during bidirectional movements for increased productivity.
A wide range of parts and geometries can be processed using combinations of cylindrical grinding, OD and ID out-of-round grinding, thread grinding, and jig grinding — all in one set-up. Advanced C-axis (ultra-high resolution) operation makes it possible to perform precision grinding of grooves, and satellite and centering bores.
The direct-drive workhead has an infinitely variable spindle speed from 1 to 500-rpm (with Heidenhain control), with a maximum weight capacity of 750 Nm / 300 kg (660 lbs), and an optional ±60-second micro-correction for adjusting cylindricity is simple.
For machining between centers, a heavy-duty Morse taper 4 tailstock with nitride-coated sleeve runs in ball-bush bearings to achieve high in-feed rates, even with heavy parts. A sleeve retraction of up to 50 mm is pneumatically or hydraulically operated. Maximum weight is 250 kg / 550 pounds between centers.
The (C-axis) option of interpolating the X and C axes make 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 (Heidenhain GRINDplus) ensure dynamic non-round and thread grinding operations. Jig grinding capability offers a complete part in one setup, an additional process that would have been done on a second grinding machine.
Multiple Wheelhead Configurations
The swiveling hydrostatic, direct-drive B-axis provides simultaneous interpolation of the X, Z and B axes with 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 set-up. A patented, Kel-Set wheel-measuring device (option) determines the wheel-edge (vector) to calculate it’s angular position automatically.
Kellenberger offers more than 28 wheelhead configurations with multiple grinding wheels for external, face, and internal grinding. The universal wheelhead configurations cover various user needs, including external, face and internal grinding. Additionally, it’s possible to select two internal grinding spindles, and optional thread grinding or non-round grinding is available.
Grinding in one setup allows shorter processing times and improves the quality of the workpiece considerably.
A universal wheelhead can be configured with up to four tools. Diagonal wheelheads provide the option of rough and finish grinding in one set-up. The additional use of high-frequency ID grinding spindles will allow universal OD, face, and ID grinding. Tandem-type wheelheads are designed for the possibility of carrying out straight and angular in-feed operations in the same setup. With an additional high-force internal grinding spindle it is possible to process internal grinding work using a tandem-type wheelhead.
Measuring systems can decrease set-up and cycle times. Options include Movomatic or Marposs active and passive longitudinal positioning and in-process gauging, Kel-Touch gap control and Kel-Balance automatic wheel balancing for precision part processing.
Precision hydrostatic guideways provide frictionless grinding, maintaining accuracy during the machine’s lifetime. The hydrostatic guides for the longitudinal slide movement (Z-axis), wheel slide 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. Even the smallest increments of 0.1 micron can be traveled without a problem.
Kellenberger’s hydrostatic guideways,in combination with the direct-drive workhead technology, provide high accuracy in concentricity and radial run-out: Part roundness of <0.2 micron; non-round contour accuracy of <6 micron; internal eccentric bore of <4 micron; straightness (slots) of <2 micron.