Rotary tables with hydrostatic bearings smooth production

A hydrostatic rotary table in use, Ø 600 mm, 120 rpm. (Courtesy: Hyprostatik Schönfeld)

Included in the product portfolio of Hyprostatik Schönfeld, a global technology leader in the field of hydrostatic systems, are rotary tables. These are used for precision machining on lathes, milling, and grinding machines, and on measuring machines.

Thanks to the hydrostatic mounting of the rotary tables from Hyprostatik Schönfeld, production becomes smoother and more precise, thus improving product quality and saving time and money. In addition, the rotary tables are wear-free, which results in greater availability and hence improved productivity.

Many users are now opting for hydrostatic rotary tables rather than rolling bearings. Unlike designs based on rolling bearings, they are wear-free and therefore particularly low-maintenance. At the same time, the performance characteristics remain constant regardless of the duration of use.

Data illustrates the benefit of hydrostatic rotary tables. For example, the concentricity and axial runout error for a model with a diameter of 1,200 millimeters is only < 0.3 µm. The runout errors for hydrostatic rotary tables are only about 10 percent of those with rolling-bearing-mounted models.

Hydrostatic rotary tables are also reliable when it comes to damping. Their damping is several orders of magnitude higher than that achieved by roller bearing-mounted rotary tables. By this means, machine vibrations are reduced, as are workpiece shape defects. The tool life is extended, and cutting performance at the upper limits noticeably increased.

Hydrostatically mounted rotary tables prove extremely thermally stable at higher speeds. The frictional heat is generated in the oil, which is immediately transported out of the bearing, cooled externally, and then returned to the bearing at a few degrees Celsius below ambient temperature. The result is a virtually cold bearing with minimum heat generation. With rolling-element bearings, by contrast, a lot of heat is generated at high speeds, heat which can only be removed from the bearing with great difficulty. This means that the thermal stability is poor.

The hydrostatic elements from Hyprostatik Schönfeld work with a PM flow controller instead of with capillaries. Consequently, greater axial and radial stiffness, and also high moment stiffness, is achieved. This stiffness is obtained even with small bearing diameters; this enables higher speeds. Over and above this, the PM controller permits the use of low-viscosity oils, resulting in higher speeds or lower pump powers and less friction.

Hydrostatic rotary tables ought to be optimally designed to withstand both static and dynamic stresses. For this purpose, Hyprostatik Schönfeld offers specialized calculation programs for hydrostatic guides and for radial and axial bearings. These programs make it possible to define important parameters such as pocket dimensions, gap widths, and pump pressure in order to achieve the required values for radial, axial and moment stiffness and, additionally, to guarantee a minimum stress reserve of up to 200 percent. Likewise, the technology of the hydrostatic bearings is optimized in order to achieve the best possible vibration damping.

Compared with solutions that use capillaries, the bearings and rotary tables from Hyprostatik Schönfeld can also unreservedly be subjected to stress, even at high speeds, without the stress having to be limited.

The Hyprostatik Schönfeld rotary tables feature:

  • Concentricity / axial runout less than 0.1 to 0.25 µm.
  • No wear, optimum damping.
  • Very stiff vis-a-vis radial, axial and moment loads.
  • Can withstand high radial and axial stresses and also moments.
  • Low heat transfer thanks to oil re-cooling, even at top speeds.
  • Exceptionally high speeds possible.
  • Wide variety of sizes, designs, speeds and load-bearing capacities as desired by the customer.
  • For swiveling axes with clamping.
  • With adapted hydro unit.