Rotary Fluid Bearings

Many customers are surprised to discover that Professional Instruments Company manufactures liquistatic (hydrostatic) spindles. Some of the very first spindles produced at Professional Instruments Company were oil film bearings. Harold Arneson investigated oil film spindles as early as 1950 in his lifelong quest for higher-accuracy axes of rotation. Today Professional Instruments Company builds liquistatic spindles to serve customers that require extremely high radial and tilt load capacities and accuracies close to levels of our air bearing products. The liquistatic bearings produced are all captured-thrust-style structures. The shafts have long journals separated by a thrust flange near the center of the bearing. The housings are manufactured using Professional Instruments Company’s unique grinding capabilities, allowing the bearings to be bolted together at the thrust flange without compromising the geometric-form requirements. The rotor and stator elements are ground to the same exacting tolerances as our air bearings, resulting in unmatched error-motion performance. The largest of the bearings we are currently producing supports 3,000 pounds of radial load and has less than one millionth of an inch of radial asynchronous error. 

A typical Professional Instruments Company liquistatic spindle has six radial pockets. The pockets are ported to allow for direct pressure measurement. The inlet restrictors can be tuned to allow for custom-tailored performance. In-line oil filtration and oil-capture seals at the shaft ends are included. Brushless-DC motors and glass-disk encoders are built directly to the rotor and stator elements ensuring high performance operation, and extremely low noise. Cooling jackets surround both the motor and the bearing structures to minimize thermal growth. Balance provisions are built into the rotor at both ends of the spindle to allow for dynamic two-plane balancing. Our liquistatic spindles can be equipped with many of the same enhancements we provide for our air bearings. Piloted chucks, rotary unions, and rotor-grounding devices are just a few. Professional Instruments Company is presently building two different liquistatic spindle assemblies. We have proven designs for a variety of sizes, ranging from one to two inch diameter rotors up to rotors seven inches in diameter. Although Professional Instruments Company does not presently manufacture a standard line of liquistatic spindles, our ability to customize a bearing to your application should serve you well.