slew bearing design

Slew bearing design:

The slew bearing design, selection, customization, and reference factors and technical standards of slewing bearings for slewing bearings are theoretically obscure and difficult to operate. Even if the algorithm of the kimono specification, the actual working conditions are very different, it may not be reasonable.

The forces on the slewing bearing and the slewing bearing, such as axial load, radial load and overturning moment, are not necessarily indispensable technical factors, such as the force of the main bearing of the shield machine and the main bearing of the TBM.

Beyond thrust (which can reach 8000-12000 tons), because it is almost on the same forward horizontal surface, the overturning moment can be regarded as 0.

Slewing ring bearing design：

1. The operating direction of the equipment is generally horizontal and axial rotation, tilt angle rotation, such as pelletizing machine, vertical direction is radial rotation, such as spiral CT machine, shield machine, TBM, etc.
2. Analysis of equipment working conditions: force distribution, axial, radial, overturning moment, thrust, eccentric load, impact force
3. The rotation speed of the device
4. The relationship between speed and heavy load, emphasizing equivalence or deviation
5. After selecting the structure of the slewing bearing, the economic factor is second
Next, as mentioned in this article, if you choose a four-point contact ball bearing, focus on the conditions of moderate speed and low heavy load, such as excavators, tower cranes, truck cranes, tire cranes and other equipment. Economic considerations are very obvious. If heavy load is considered, it is selected in three-row roller bearings, but the cost is appropriately high, and in terms of reliability and stability, there are more arrangements in terms of bearing material, heat treatment, machining accuracy, and process level.

Slewing ring bearing with external gear:

1. In order to improve the wear resistance of slewing bearings, tooth surface quenching is necessary, but considering the bearing load, you need to be cautious. 42CrMo material generally does not need quenching at all.
2. The rotation performance of the slewing bearing requires high levelness of the installation base surface and the installation base, otherwise, the deviation of the center of gravity will cause uneven force
3. The gear and pinion of the slewing bearing must mesh well
4. The main consideration for choosing 42CRMO instead of 50MN is that 42CrMo has a combination of flexibility and hardness, while 50MN has strong rigidity but fragility.
5. The slewing bearing and slewing bearing are frequently overhauled and the lubrication system is maintained to maintain normal lubricating oil, as a key measure for sealing protection.

Slew bearing tolerance:

First of all, it needs to be clear that whether the standard for slewing bearings is JB/T10471 or JB/T2300 for slewing bearings, in fact, to sum up, most of the applications of slewing bearings belong to the bulky field of heavy industry, and the accuracy of gear meshing Sexual requirements are not high, generally grade 10 teeth.

After the tooth surface is quenched, the accuracy level is lost to level 12. From the application, it does not affect the meshing. Therefore, emphasizing the high precision of the gear is a fuss and fault, and it is of no practical significance. It is just a waste of labor costs. .

Of course, when it comes to the accuracy of the slewing bearing, it is generally obtained through tooth grinding. Several key data of measuring gear are as follows.

Common normal length, common normal deviation, tooth jump, fixed string tooth height and tooth thickness, as for the tooth profile, tooth direction and tooth pitch, you need to use professional instruments to measure.

Regarding gear accuracy measurement, we are currently able to measure items such as common normal dimensional tolerance, common normal variation deviation, fixed chord tooth height and tooth thickness. For other gear accuracy requirements, such as tooth profile, tooth direction, tooth pitch, etc., currently unconditionally measured. In the case of tooth grinding, it is generally within a reasonable range.

Internal gear slewing bearing:

Internal gear bearing and external gear bearing: The gear accuracy ultimately determines the transmission accuracy of the slewing bearing rotation:
why would you say so? It should be known that the rotation accuracy of the slewing bearing includes end face runout, radial runout, and gear runout.However, when the slewing bearing rotates, the final output accuracy is concentrated on the gear accuracy, so the gear accuracy has the following parameters:

1. The number of teeth across the gear and the length of the common normal
2. The tooth jump of the gear, the highest point
3. The verticality of the gear
4. Tooth direction, tooth profile and tooth thickness
5. Quenching hardness of tooth surface
6. The hardness of the tooth surface
7. Gear shaping grade, according to gear hobbing grade 9-10, gear shaping grade 7-8
8. Finally, the roughness of the tooth surface is required. If the gear is shaped, it should be around Ra1.6, the hobbing should be around Ra3.2, and the grinding should be around Ra0.8.
9. The relationship between quenching and tempering hardness of gear and quenching hardness
10. The highest point of the final rotation accuracy of the gear should be the green paint standard.

Slew bearing design and selection:

1. Choose a good structure, this is the most basic working condition
2. Determine the material, because it affects the life and heat treatment process
3. Accuracy standards and key indicators, such as clearance, runout, rotation accuracy
4. The installation method directly determines the operation mode of the cage
5. Sealing protection
6. Lubrication method
7. Gear meshing
8. Anti-corrosion treatment
9. Utilization of ash shield
10. Matching size, stop, step size and positioning size.

The slewing bearing with gear ring has the function of transmitting power and simplifying the main machine mechanism. Among them, the internal gear slewing bearing has a compact structure, low contact stress during transmission, low wear, grease, easy to maintain lubrication for a long time, good dust-proof effect, and the protection requirements for the meshing part are relatively better than the meshing effect of external teeth.

With external gear structure slewing bearing, the method of tooth profile processing and detection is quick and convenient. High manufacturing precision. It is easy to obtain the highest precision of grinding teeth, and can maximize the use of supporting space. And the tooth profile has a large pitch circle diameter. A larger transmission ratio can be obtained.

At the same time, the circumferential force and torque of the pinion can also be reduced, thereby saving efficiency. Of course, in terms of manufacturing costs, most of the internal teeth are shaped gears, which requires long working hours, and most of the external teeth are gear hobbing, and the speed is fast. Therefore, internal gear bearings are generally more expensive than external gears.

Slewing ring bearing manufacturers:

Slew Bearing Design and selection are consider the core parameters of the large slewing bearing slewing ring selection. After fully considering the working conditions, the overall dimensions, installation dimensions, load capacity, speed, lubrication, protection measures, and slew bearing design life of the large bearing can be selected. .

1. First, determine the overall dimensions and installation dimensions of the large bearing. This is the first issue to be considered. How many pots are there, and how many meters there are. This determines the structure of the bearing.
2. Load, which needs to be calculated, including axial load, radial load, overturning moment, and impact load.
3. Rotation speed, the rotation speed of the slewing bearing is not high, more than 15Rpm, you need to consider the segmented cage, the overall cage.
4. Installation methods, such as horizontal installation, vertical installation, inclined installation, and multi-directional movement installation, the cage needs to be fully designed.
5. The lubrication method is convenient, fast and beneficial.
6. Design and utilization of ash guard
7. Accuracy standards.
8. Fully consider the advantages of each structure of the bearing. Four-point ball bearings are flexible and resistant to permanent fatigue. Double-row ball bearings have the above advantages while increasing the load. Crossed roller, anti-permanent deformation, strong rigidity, crossed tapered roller bearing, high precision, three-row roller bearing load is the highest under the same size.

Slewing ring bearing calculation:

Calculation method of static reference load Fa’ and M’
Single-row four-point contact ball
The selection and calculation of single-row four-point contact ball slewing ring are carried out according to the load angle of 45° and 60° respectively.
I, a=45°　, a=60°
Fa’=(1.225•Fa+2.676•Fr)•fs　Fa’=(Fa+5.046•Fr)•fs
M’＝1.225•M•fs　M’＝M•fS
Then find the above two points on the graph, one of which is below the curve.
Single row cross roller type
Fa’=(Fa+2.05•Fr)•fs
M’＝M•fs
Double-row reducing ball
For the calculation of the selection of the double-row reducing ball slewing ring, when Fr ≤ 10% Fa, Fr is ignored. When Fr>10%Fa, the pressure angle change in the raceway must be considered. Please contact us for its calculation.
Fa’=Fa•fs
M’＝M•fs
Three-row roller type
When selecting the three-row roller slewing ring, only the effects of axial raceway load and overturning moment are calculated.
Fa’=Fa•fs
M’＝M•fs