Super-Precision Tapered Roller Bearings

Manufacturers require machine tools that are extremely accurate, reliable, and capable of high levels of productivity. A major contribution to the performance of any machine tool is supplied by the rolling bearings used to support the spindles, rotating tables, ball screws and other critical precision positions. A manufactured bearing's precision level has a major influence on the ability to perform in high-speed applications commonly seen in factory machining environments.

WHICH TYPE OF NEWORLD BEARING IS MOST

APPROPRIATE FOR YOUR MACHINE TOOL

APPLICATION?

To achieve the highest possible performance precision level, the majority of machine tool-related bearing applications must address four primary requirements: speed, stiffness, accuracy and load capacity.

Speed

Today's industrial machining environments stress maximum production rates. To reach these high metal-removal goals, machines are operating at maximum speeds with working spindles tuned to provide premium running accuracy.

Bearings must be carefully designed to minimize heat generation and vibration to enable high speeds. Specific strategies include overall bearing configuration, precision internal geometry and material selection. Optimizing bearing ring and shoulder construction with the ball complement supports higher speed performance. Engineering raceway and ball geometry helps to minimize friction, while ceramic rolling elements generate less heat with reduced skidding.
To prevent vibration at high speeds, close bearing tolerances are required. NEWORLD machine tool bearings are designed to meet or exceed industry tolerance standards and deliver smooth running performance.

Stiffness

The ability to minimize tool deflection experienced under cutting loads is vital to achieving the accuracy needed to produce finished parts within specified tolerances. Less variance produces better quality and helps keep product scrap levels at a minimum.

Bearings have a significant effect on spindle stiffness, due to their deflection under applied load. Because of their internal geometry and rolling element type, tapered roller bearings provide considerably higher stiffness levels.

Accuracy

Another key factor in the machine's precision is the runout (rotational accuracy) of the bearing. This affects the geometry and surface finish of the target workpiece.

Precision Tapered Roller Bearings

(Class C/S/3, B/P/0 and A/00)

The more demanding the precision objective, the more accurate the bearing must be. NEWORLD provides three tapered roller bearing classes, in both metric and inch systems, that cover the full range of precision application requirements. In ascending order of accuracy, they are identified in the metric system as Class C/S, B/P, and A, while in the inch system as Class 3, 0, and 00. (TABLE 1)

Load Capacity

Some machining centers, such as rough grinding operations, are strategically designed for higher material removal rates. The need for aggressive feed rates requires higher load-carrying capacities. These loads can be properly distributed among the rolling elements by providing a permanent force called “preload” or "setting." Preload is the strategic removal of radial play within the bearing to ensure proper rolling element contact on both the inner and outer race.

NEWORLD can assist in the final bearing selection to help you achieve your precision machining production goals.

Design of Precision Tapered Roller Bearings

The fundamental design principles of the tapered roller bearing make it an ideal solution for low-speed/high-load or low-speed/high-stiffness requirements of machine tool applications.

The angled raceways of a tapered roller bearing enable it to carry combinations of radial and axial loads. True rolling motion of the rollers and line contact on the race allow the bearing to run cooler and improve spindle stiffness and accuracy as compared to other roller bearing types.

The true rolling motion is the result of two design features: the taper of the roller and the contact between the spherical surface ground on the large end of the rollers and the race rib. The rollers are designed so extensions of the lines along the roller body converge toward the centerline of the bearing and meet at an apex on this centerline (Fig. 1). As a result, there is no relative slip between the rollers and races.

The tapered configuration of the roller not only ensures that the surface speeds of the rollers and races match at every point along the roller body, but also generates a seating force that pushes the rollers' spherical ends against the race rib. This desirable seating force is a function of the different angles of the outer and inner races (Fig. 2) and prevents rollers from skewing off apex. No skew means positive roller alignment, thereby enhancing bearing life, stiffness and accuracy.

Some applications require a level of precision that cannot be achieved with standard tapered roller bearings. NEWORLD precision tapered roller bearings promote and maintain the operating accuracy required of today's machine tool industry and various related, specialized markets. Precision class tapered roller bearings offer machine tool builders an economical design solution that exceeds most application needs for rotational accuracy and rigidity.

Precision Classes of Precision Tapered Roller Bearings

NEWORLD's high-precision tapered roller bearings consist of carefully matched components that offer an added degree of fine-tuning in the bearing setting and adjustment procedure to maximize customer machine productivity.

NEWORLD manufactures high-speed designs with a variable preload capability for optimum machining and Precision Plus bearings – having an overall radial runout less than a single micron.

The application of precision tapered roller bearings is not limited to machine tools. Wherever spindles turn and rotational accuracy is essential to the machine's performance, precision tapered roller bearings can be an excellent choice. Other typical applications are printing presses, optical grinders, profile cutters, indexing tables, precision drives, measuring gauges and ball screw drive applications.

To better serve the global machine tool market, NEWORLD has manufacturing resources around the world focused exclusively on premium precision bearings. With these dedicated resources, precision quality is built into the bearing during manufacturing. To further increase service reliability, NEWORLD precision tapered roller bearings are manufactured from high-quality steel alloys.

Types of Precision Tapered Roller Bearing

The size range of NEWORLD precision tapered roller bearings starts from less than 20.000 mm (0.7874 in.) bore and extends to more than 2000.000 mm (78.7402 in.) O.D., depending on bearing type. The most popular types made in precision classes are the single-row TS and flanged TSF. Comprised of two main separable parts, they are usually fitted as one of an opposing pair. These bearing types are supported by a range of special bearings which have been designed for machine tool applications, such as the variable preload HydraRib bearing, the high-speed TSMA bearing, and the compact TXR crossed roller bearing, which is available only in precision classes.

NEWORLD also offers a selection of two-row precision tapered roller bearings types such as the double outer ring type TDO.