As Mark Albert of Modern Machine Shop has written, it seems like grinding processes are “always being pushed and pulled at the same time.” On the one hand, competing machining processes like high speed milling, EDM and hard turning push grinding out of some applications.
On the other hand, “the pull comes from demand for grinders that can meet tighter tolerances, generate finer surface finishes, accommodate harder or more difficult workpiece materials and combine operations on a single machine platform,” Albert explains.
Kellenberger, a Hardinge brand, says its updated Varia universal cylindrical grinding machine meets just those kinds of needs. An enlarged workspace enables custom configurations incorporating processes such as internal, thread or out-of-round grinding. Meanwhile, hydrostatic guideways deliver vibration damping and smooth, accurate operation for high-precision grinding of tools, molds and other components in the automotive, electronics, aircraft and job shop sectors.
The Varia grinder provides distances between centers of either 39.4 or 63 inches (1,000 or 1,600 mm), and heights of centers of either 7.8, 9.9 or 11.8 inches (200, 250 or 300 mm). The elongated machine table can handle workpieces weighing as much as 661 pounds (300 kg). According to the company, the longer table, greater distance between centers and longer axis travels provide room for:
Optimal wheel positioning and greater flexibility for application-specific wheel configurations,
A 125-mm-diameter internal grinding wheel, and
Expanded wheelhead variations, including more than 30 combinations of external and internal spindles as well as universal wheelheads for single-setup OD, ID and face grinding:
diagonal wheelheads for rough and finish grinding:
and tandem wheelheads for straight and angular plunge grinding work:
These extended features all benefit from the use of hydrostatic guideways.
Hydrostatic Guideways for X, Z and B Axes
Rather than bearing or roller guideways, whose metal-to-metal contact increases friction, heat and therefore wear, the Varia grinder uses a hydrostatic way system. This means the guideways use a pressurized film of oil between the slides of the way elements, eliminating surface-to-surface contact for high vibration damping, stick-slip-free operation, rigidity and temperature control. All this adds up to higher accuracy over long periods of time.
But the hydrostatic elements aren’t limited to the Varia’s X and Z axes. The B axis also uses a pre-tensioned hydrostatic guideway along with its direct drive, enabling fast, smooth movement in increments of as little as 0.0001 degree.
The hydrostatic B axis in action.
This precision, Kellenberger says, makes it easier to perform non-round and tapered grinding on small and large workpieces alike.
For specs and to request more information, see the Varia’s Techspex page.