Much of the most precise metalworking machinery uses fluid film journal bearings. High-speed grinders are prominent in this category of machinery. Fluid film bearings are a popular choice for such machinery, as they require a heavy-duty bearing due to their long lifespan and high load-carrying capacity. Additionally, fluid bearings are beneficial in mitigating the vibrations such large machinery often produces. This type of vibration can ultimately cause tremendous damage in machinery, including broken shafts, failed generators, and shut-down compressors.
Over an extended period of time, large amounts of vibration can cause equipment to fail prematurely, and result in expensive repairs.
The most accurate grinders use lobed or tilting pad journal bearings to precisely locate the shaft in the center of the bearing and bearing housing. These designs are selected for their ability to spread the load over multiple pressure points. In a conventional cylindrical journal bearing, the load is supported by one oil wedge and reaches equilibrium at a location concentric to the center of the bearing bore. However, multi-lobe and tilting pad bearings have multiple oil wedges that share the load and increase the oil film thickness on each of the pressure points.
The higher oil flow and lighter loads allow Wheeler bearing designers to reduce the radial clearance of multi-lobe and tilting pad bearings. This reduced clearance again results in closer centerline positioning of the shaft.
These hybrid bearing designs adjust to varying loads with less centerline displacement. Loads change as the tools engage the workpiece. The damping characteristics of all fluid film bearings smoothly move to a new equilibrium position base on the altered load and speed. With hybrid designs, the increased load is spread across multiple points, and the resulting shift in position is typically less than 0.0002 inches. Machine tools using precision ball bearings experience some deflection in this scenario and, more importantly, reduced bearing life. In high-speed machinery, this condition often leads machine designers to select fluid film bearings. The result is far greater accuracy and increased longevity of equipment.
Engineers at Wheeler can design and optimize journal and thrust bearing configurations that produce lower operating temperatures, less horsepower losses, or higher load-carrying capacity.