Difference between high-speed and low-speed bearings

Many people may misunderstand it, it’s not that the rotation speed of the bearing itself, but its linear speed. Many low speed bearings can reach tens of thousands of revolutions per minute, on the other hand, for some high-speed bearings, the data of rotations per minute maybe only just a few hundred.

There are also some other differences between the two. Generally, low-speed bearings have a rougher appearance, and the joints between parts are looser. To ensure its accuracy, the precision of high-speed bearing is generally very smooth on the surface, and the distance between the inner ring and outer ring is minimal, the accuracy is much higher. Many high-speed bearings are also super-precision bearings. It normally use special high speed grease.

In terms of material, there is also a slightly difference between high-speed bearing and low-speed bearing. High speed bearings are generally made of very high hardness steel, which can withstand the pressure caused by excessively high speeds. If it’s low, some common materials are used, the requirements for hardness and durability of the material are relatively reduced.

What to do if the high-speed bearing is overloaded and hot?

1) In the case of considerable size, large load, significant vibration, high speed or high operating temperature, the cooperation between the bearing and the shaft should be tighter
2) Use lubricating oil to reduce friction, large load, and high viscosity oil should be used when the working temperature is high; it’s easy to form an oil film, thereby reducing heat generation. High-speed bearings and super precision bearings must use special high-speed bearing grease.

Factors affecting the life of high-speed bearing shafts

The length of the bearing field test life is mainly determined by the design and matching of the bearing’s structural parameters, as well as the product’s manufacturing quality and process level. Still, there are also some “non-bearing” factors that will cause the reduction of bearing field service life and failure. The analysis of failed bearings mainly includes the following:

1) The selection and installation of the angular contact ball bearings used by the spindle maintenance personnel in pairs
2) Repair and disassembly times of electric spindle. Multiple disassembly and assembly of the same set(group) of bearings will inevitably affect the service life of the bearings
3) The old and new of the electric spindle and the structure and manufacturing quality of the electric axle produce by different manufacturers are different
4) The electrical failure of the main shaft itself, such as wet weather, moisture in the electric main shaft housing, and the rotor shaft silicon steel sheet burned
5) The lubricant for oil spray cooling contains impurities
6) Technical quality and sense of responsiility for machine tool operators. For example, in the test, due to operating errors many times, the oil was cut off, the grinding head entered the water, and the bearing was burned
7) Keep the bearings properly, such as severe bearing corrosion and bearing pollution
8) Professional high speed bearing grease must be used for carrying maintenance

TBB Case of High-Speed Bearing

Early in year 2020, TBB received an project asking for extra-high speed bearing from a client of gas turbine engine field, requirements as below:

Inner diameter : 4 ~ 6mm
Driving Speed : 110,000 ~ 130,000 rpm
Temperature : lower than 100℃
Shield Type(no need for grease supplement)

Considering the working condition and application details, we carefully analysis with our technical department, and after some rounds we finally suggested our clients to use hybrid ceramic bearing 706C, detailed technical data as following:

1. Bearing Item: 706C-ZZ/HQ1P4
2. Inner/Outer rings material: ZGCr15
3. Ball material: Si3N4
4. PEEK Cage
5. Tolerance class: P4
6. S1 high temperature tempering treatment
7. Grease: Lubcon Thermoplex LME 552 (-40 to 220℃）
8. Limited Speed: 113,000rpm
9. Load: Cr=1800N, Cor=760N,
10. L10 Life: According to GB/T 6391-2003 standard, L10=10000h

This is a customized item, which needs to open mold. And the first sample 10 pcs was delivered on Sept-2020, the second sample 100pcs was delivered on Mar-2021, till now, 3 pcs blowers developed with TBB bearings have been successfully delivered. It will be re-developed as a way to reduce the power consumption. And durability testing is also in progress, it’s already lasting more than 1400h.

If you have similar demand or application, come to TBB, we could provide technical support and satisfy you.