How to choose a CNC spindle? The spindle is the main force of CNC machining

Spindle bearing system

The bearing system uses balls to maintain the separation between the inner and outer steel raceways. The operating temperature, vibration level and service life of the spindle will depend on the material of the component. Hybrid ceramic bearings are definitely superior to standard steel ball bearings.

Better quality

Ceramic ball bearings are 60% lighter than steel balls. This is important because when the ball bearing rotates, especially at high speeds, the centrifugal force pushes the ball towards the outer ring. This deforms the shape of the ball, and the deformation causes the ball to wear faster. Because ceramic balls are lighter, they are less affected (at the same speed). Therefore, the ceramic ball can increase the rotation speed of the ball bearing by 30% without affecting the bearing life.

Non-contact welding

The ceramic ball does not fuse to the steel raceway, thereby eliminating the condition called contact welding, which is an important cause of bearing failure. Contact welding occurs when pressure causes the overall flow of the metal and thus the metal surface to fit. As the bearings continue to rotate, these microscopic welds crack, producing surface roughness, which in turn leads to heat generation. Finally, the bearing fails.

Work at a lower temperature

Because its sphericity is almost perfect, the ceramic bearings can rotate at a lower temperature, thereby extending the service life.

Reduce vibration level

Tests have shown that the spindle with hybrid ceramic bearings is stronger and has less resonance. Therefore they are less sensitive to vibration, which in turn leads to a longer service life.

Bearing type

Bearings are designed to withstand different types of loads, such as radial or thrust. In high-speed spindles, the most commonly used is angular contact ball bearings. These provide the precision, load-bearing capacity and rotational speed required for cutting metal. Precision balls are suitable between steel rings and are strong enough to withstand axial and radial loads.

Tapered roller or cylindrical roller bearings are another type of bearing. These can withstand greater radial loads. Roller (or cylindrical) bearings are harder than ball bearings and are designed for high-speed applications. Spindle motor manufacturers usually use both ball bearings and rolling bearings in different parts of the spindle, depending on the type of load the bearing must bear.

Lubrication method

Properly lubricating the bearings is essential. Machine tool manufacturers use many systems to maintain proper lubrication of bearings, such as oil mist, oil injection, oil air, and pulse oil air.

If the spindle speed exceeds 18,000 rpm, these systems are needed, but they are more expensive to maintain and replace. In addition, these lubrication systems must be regularly monitored to ensure that the correct amount and mixture (oil mist, oil spray or oil-air) is used.

Sintered bearings are the best choice to reduce maintenance and replacement costs. Lubrication was performed once during the assembly of the spindle, and it was immediately sealed, so you don’t have to worry about lubricating these bearings.