The hydrostatic rotary table is a large machine tool that utilizes hydrostatic bearings, it is used in a wide range of machining for large gears. Hydrostatics provide the rotary table substantially better load capacity than aerostatic bearings. Therefore, hydrostatic tables are commonly used to produce precise components for mills and other large gear applications, typically applied in a grinding system.
In the 1940s, it was proposed to utilize the opposed gap to control the flow to pockets on the opposite side of a bearing, which means the bearings would be self-compensating in this way. The self-compensating method then is refined and highly developed to apply to precision grinding machines.
Hydrostatic Rotary tables nowadays are commonly applied on grinding machines, especially surface grinding. If extreme stiffness and high load capacity are the factors that the operators are considering, the hydrostatic rotary table will be an ideal choice.
A hydrostatic rotary table consists of hydrostatic bearings, hydrostatic guideways, pressure self-compensation technology, and so forth.
The hydrostatic bearings provide a pressure supply in order to maintain clearance between the rotating and stationary elements. Between the moving surfaces, the lubrication is constantly supplied under pressure with the bearings.
Hydrostatic rotary tables are supported by oil film between guideways. The bearing surfaces are always separated by a thin lubricant film at static pressure. There is no friction between two contact surfaces when using a hydrostatic guideway. With the flow controller, a hydrostatic fluid film of the guideway, the hydrostatic rotary table can achieve high stiffness, high stability, great precision, and control without gear wear.
However, the accuracy can still be improved by regulating the oil film thickness of the hydrostatic rotary table. The oil film thickness can be controlled by the pressure control and the speed control via a variable hydraulic motor.
The hydrostatic lead screws are used to translate the rotation from a servo motor into linear motion. Compared to ball screws, lead screws have substantially smoother, cleaner, and quieter motion. The hydrostatic lead screw of the rotary table is self-lubricating, totally wear-free while the hydrostatic nut floats on a thin oil film.
Hydraulic motors are mechanical actuators that are designed to convert hydraulic pressure or fluid energy into mechanical power. A hydraulic pump, on the other hand, converts mechanical power into fluids or hydraulic power. Hydraulic motors can provide the driving force for the rotary table, supporting the motion to move an external load.
The oil filter, the pressure relief valve, and the throttle are also required in hydraulic machinery. Oil filters are designed to remove the contaminants from the hydraulic oil in hydrostatic rotary tables. The dirty oil would pass through the filter when pushed by pressure and return to the central hole, then the oil would re-enter the system. Most pressurized lubrication systems work with pressure relief valves, controlling oil to bypass the filter if the flow restriction is excessive. If the oil is thickened or the filter is clogged, pressure valves will also regulate the oil to bypass.
High Accuracy: During machining and grinding, generally, oscillation motions can lead to lower accuracy or even failures over time. However, a hydrostatic rotary table that utilizes hydrostatic guideways and hydrostatic lead screws creates little wear and little loss of accuracy in oscillation motions. With the arrangements, the machining and grinding run in maximum positioning accuracy.
Almost Frictionless Motion: Hydrostatic bearings provide hydrostatic rotary table significant advantages over tables that use mechanical bearings or other approaches to the rotation. Without mechanical attaching parts to wear or generate friction drag, the bearings of the hydrostatic rotary tables provide almost frictionless, smooth, accurate, and repeatable rotation.
Stiffness and Durability: Remarkable stiffness and durability of hydrostatic rotary tables provide the machine almost unlimited life. Even when it is exposed to harsher environments or an accident happens, often the bearings only need to be repaired but no need for replacement.
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