The bearings of the spindle are the ones that support the spindle to accurately and efficiently perform its machine task. They are usually affected by four vital factors: the design of the bearing, the material it is made of, lubrication, and contamination.
The performance of the machine spindle and the bearings that support it are very critical to attain best results and to fully utilize the machine. It will also help you save on costs for spindle repair services and other services, as well as the risk of machine failure. Here are the important factors that affect the bearing performance of a machine’s spindle:
When you speak of speed, the design of the bearing is what you need to consider. The most common high-speed spindle design used today is the angular contact precision ball bearings. Its speed, precision, and load capacity make the design ideal for metal cutting. It offers various choices for different contact angles, preload, raceway curvature, and ball sizes. These choices affect the speed bearing performance of your spindle.
*Contact angles. Your contact angle options will affect the speed, radial load, and axial load of your machine. For this bearing design, a larger contact angle would mean lower speed and radial load capacity, but higher axial load capacity. A smaller contact angle, on the other hand, would result in higher speed and radial capacity, but lower axial load capacity. So when drilling, for example, you can use a higher contact angle and a lower contact angle when milling.
*Preloading. Different preloading magnitudes also affect the speed of your spindle. Angular contact bearing usually has three choices for preloading magnitude: light, medium, and heavy. Lighter preload bearing gives higher speed, but lesser stiffness while heavier preload bearing means lesser speed, but higher stiffness. Lighter preload bearings are advisable when cutting light loads and heavier preload are best when working with heavier loads.
*Raceway curvature. Different tools and machines are currently being designed to increase speed by optimizing performance between ball bearings and the raceway.
*Ball sizes. The bearing speed of your spindle is also affected by the ball size of the bearing design. Ball bearings that are smaller in diameter would lead to higher speed because of the smaller mass. It also results in a lower operating temperature and greater stiffness. This is because more ball bearings are used as compared to utilizing big ball bearings.
To date, hybrid bearings have become more popular for its advantages. Hybrid bearings are those made of steel rings with ceramic rolling elements. Silicone nitride is the most commonly used ceramic element because it is said to extend the life of the bearing by creating lower temperatures even in higher speed applications. This is ideal for the ball bearings since it is very flexible.
Spindles need lubrication to optimize performance. The lubricating system you need to apply depends on the machine of your choice and its specific lubricating requirements. Lubrication systems include grease, oil-jet, oil-mist, and oil-air, with grease being the most common. Oil-jet is said to offer the fastest speed, while the grease system comes last. Grease is permanent and it requires lesser maintenance than other lubricants. It should not be over-applied as it will result in heating, thus deteriorating the grease and the performance of your spindle. A run-in period is usually advised to allow the grease to be properly and fully distributed within the bearing. For other lubricating systems, maintenance is very important to keep the spindle bearing in good condition.
Contamination can cause your machine to fail. This is the reason why it is important to protect the bearing from being contaminated. One way to do this is through positive air overpressure. Furthermore, when rebuilding spindles, the room should be clean. Original components must also be used when replacements are needed to avoid contamination.
These important factors must be carefully considered to increase the spindle’s speed and to fully utilize the performance of your spindle and its bearings. Proper care and maintenance are also needed to minimize immature machine failure.