Low noise sealed bearing grease

Foreign low-noise sealed bearing greases are roughly divided into three categories: general low-noise motor bearing grease, low-temperature high-speed bearing grease, high-temperature long-life low-noise bearing grease.

    1. General low noise motor bearing grease

    In the bearing industry, this grease is used in the largest amount, accounting for about 70% of the total grease. Because this type of grease uses a soft, easy-to-filter lithium soap as a thickening agent, using mineral oil as a base oil, it is easy to meet the requirements of low and medium-end bearings to reduce the vibration value. Another advantage is that it has good pumpability, whether it is mechanical fatliquoring or manual grease application. Moreover, the grease is inexpensive and can greatly reduce bearing costs. However, due to the use of mineral base oils, these greases have been compromised in terms of physical and chemical properties other than rust and rust resistance. If the bearing life can only reach 200 hours, the starting and running torque will be difficult to test at -20 °C. The grease is generally used at a temperature of -20 to 120 ° C. When used at a high temperature of 150 ° C or higher, the base oil evaporates too quickly and the loss is severe, which greatly shortens the service life of the bearing.

    2. Low temperature high speed bearing grease

    At present, the use of precision bearing equipment is becoming more and more refined, and the grease used in bearings must have the following properties:

    (1) It has the same operating life as the bearing, prolongs the maintenance cycle, shortens downtime and improves labor productivity.
    (2) Under the high speed of dn>5×105, it is necessary to ensure that the motor temperature rises low and does not lick oil, thus reducing power consumption and protecting the motor.
    (3) The impurity content is controlled under certain standards to minimize the pollution of equipment noise to the environment.
    (4) Guarantee the flexibility of starting and running the bearing under ultra-low temperature working conditions to ensure the minimum output power.

    Foreign grease companies use high-purity chemical synthetic oils and some special additives to develop and produce low-temperature high-speed bearing greases in high-purity environments and equipment. The disadvantage of this kind of grease is that when it is used over 150 °C, its life decreases sharply with the increase of temperature, and the load and impact resistance are weak. It should be avoided on medium and large bearings to prevent the boundary lubrication. sintering.

    3. High temperature long life low noise bearing grease

    Greases used in high temperature and high speed environments should have the following characteristics:
    (1) It does not lose at high temperature, that is, maintains a certain consistency at a temperature of about 180 ° C, and does not soften.
    (2) Less grease leakage. When the grease is subjected to high-frequency repeated shearing and large centrifugal force in the bearing, the lubrication can be recirculated to the raceway in time.
    (3) These greases must have a certain high temperature service life and have good oxidation resistance at high temperatures, thus prolonging the life of bearings and related equipment.
    (4) It has a certain mute effect. Because the fiber of high-temperature grease is generally hard, the mute performance in the bearing noise test is far less than that of lithium-based grease.

    High-temperature long-life grease is generally divided into two types, one is a lithium complex grease, which has good high temperature performance, but due to the addition of low molecular acid in the thickener crystal, the hardness of the fiber increases greatly. The bearing exhibits poor vibration performance. However, by controlling the degree of polymerization, a product having a uniform molecular weight distribution is obtained, and such a product is dispersed in a base oil by a special method to prepare another grease having excellent noise performance and high temperature performance. The grease has an average dropping point of more than 250 ° C and a use temperature of about 200 ° C. The thickener crystals do not contain metal ions, the fiber hardness is small, and the noise performance is good. At the same time, due to the thermal coupling effect between its basic chemical components, high temperature grease is reduced. This high-temperature, high-speed, low-noise grease does not contain any metal ions that can cause catalysis and oxidation, and a thickener rich in nitrogen and oxygen atoms is also an antioxidant, so the bearing life and sound quality are better. Table 1 shows the grease for sealed bearings produced by major foreign companies.

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The difference between vibrating bearings and ordinary bearings

1 appearance characteristics

    Special bearings for vibration:

    A. The diameter of the rolling element is increased, and the length of the rolling element is increased.
    B. The cage guides the rollers from the outer ring ribs to reduce the force on the rollers.
    C. Use the inner ring rib to guide the roller to improve the roller operation.
    D. The cylindrical roller bearing cage adopts a monolithic structure and the strength is greatly improved.
    E. The outer diameter of the self-aligning bearing is designed with oil groove and oil hole, and the lubrication effect is good.

    Ordinary bearing:

    A. The roller body diameter and the rolling element length are both small.
    B. The cage has a roller or inner ring guide.
    C. Cylindrical roller bearing cage adopts rivet structure, which is easy to loosen and cover.
    D. The outer diameter of the self-aligning bearing has no oil groove oil hole, and the lubrication effect is poor.

    2. Selection of materials

    Special bearings for vibration:

    A. The inner and outer rings and rolling elements are vacuum degassed bearing steel, which has good fatigue resistance.
    B. The cage is made of aluminum-iron-manganese bronze material with high strength, good elasticity and better wear resistance.

    Ordinary bearing:

    A. The inner and outer rings and the rolling elements are made of ordinary bearing steel.
    B. The cage is made of zinc brass with low strength and poor elasticity.

    3. Heat treatment method

    Special bearings for vibration:

    A. The inner and outer rings are made of shell-mamming quenching or martensitic quenching + high temperature tempering, with uniform hardness and small internal stress; good toughness, impact resistance and vibration.
    B. When working within 150C temperature, the stability is good.

    Ordinary bearing:

    The inner and outer rings adopt ordinary quenching method, which has poor toughness, poor impact resistance and vibration performance, and poor thermal stability.

    4. Tolerance and manufacturing process

    Special bearings for vibration:

    A. It is manufactured strictly according to the P6 precision standard, especially the tolerance of inner and outer diameter is very small.
    B. The size of the rolling elements is different from each other ≤ 0.002
    C. The outer diameter of the cylindrical roller has a convexity to avoid stress concentration.
    D. The rolling surface is super-finely processed and has a high finish.

    Ordinary bearing:

    A. Ordinary PO-level precision tolerance (partial P6 standard) manufacturing.
    B. Rolling body grouping ≤ 0.005.
    C. Cylindrical roller without convexity practice.
    D. Part of the raceway is only polished, and the finish is low.

    5. Internal clearance

    Special bearings for vibration:

    The clearance is produced according to the requirements of the vibration machine, and the range is controlled within a small range with good consistency.

    Ordinary bearing:

    The play is generally produced according to the standard group or the C3 group, the play is small, or the range is large, and the dispersion is large.

    6. Use effect

    Special bearings for vibration:

    Low noise, low temperature rise, good stability, long service life and no early fatigue.

    Ordinary bearing:

    High noise, high temperature, poor stability, short service life and early fatigue.

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Tips for selecting grease for bearings

Abstract: The CAD/CAM system has played an important role in many aspects. This paper combines the development practice of the tooling management system of Wafangdian Bearing Co., Ltd., and focuses on the overall structure of the system and the entry, retrieval, modification and printing of the tooling schedule. The implementation of functions such as output, version management, and electronic signature hope to provide a reference for comrades who are doing similar development work.

Key words: tooling, CAD, PowerBuilder

  0 Preface

Wafangdian Bearing Co., Ltd. is the largest bearing manufacturer in China. {TodayHot} has nine series of bearing production capacity of more than 5,000 varieties. The technical documents of its products are very complicated, and it is very close to review, copy, use, save and update. inconvenient. In the increasingly fierce market competition, in order to strengthen the standardization of management and improve work efficiency, the use of computer management has become an inevitable choice. Dalian University of Technology and Wafangdian Bearing Co., Ltd. worked closely together to successfully develop the bearing CAD/CAPP system and achieved the expected results. This article will discuss in detail the composition, function and characteristics of the tooling management system.

1. The overall design of the bearing tooling management system

1.1 Functional requirements of the system

The function of the system is shown in Figure 1. It consists of three modules: tooling schedule management, password management, and tooling name table management.

2. Main functions and features of bearing tooling management system {HotTag}

In the development process, according to the actual situation of the tile axis, the human-machine interface adopts the format of the paper tooling list used in the actual use, and adopts the color configuration of “white paper black”, which makes the likes to eliminate the strangeness to the computer. Feeling and discomfort, enhance the friendliness of the interface, and in order to facilitate the likes and management, the four parts of the schedule use a consistent interface format.

2.1 data entry function

Since the tile axis has more than 5,000 bearing types, the amount of data to be entered is large. In order to ensure the fast, accurate and standardized input data, a drop-down sub-data window and a drop-down list box technique are adopted in the data window of the input interface. The specific instructions are as follows:

Drop-down sub-data window technology: Since the name items of each fixture's fixture or gage are basically similar, select the drop-down sub-data window attribute in the data window name item, increase the dynamic pull-down sub-data window function, and create the corresponding table to store The newly-created name, the new name can be entered once, the application will automatically remember and update the data content in the drop-down sub-data window. When you use it, you can enter the name by simply clicking the corresponding name item with the mouse. The data entry efficiency is obvious. Improve and make the names of different expressions in the actual use unified into a consistent name, which achieves the standardization of data entry and creates favorable conditions for computer processing data. The "a, b, f" symbols, which are often found in the main dimensions, also use the drop-down sub-data window technique to achieve the purpose of simplifying the entry.

Drop-down list box technology: For the "remarks" one of the two options - "base map original" and "new design" use a drop-down list box, just use the mouse to click the corresponding item.

Due to the use of the drop-down sub-data window, the data table has been added, and the addition and deletion management module for this table has been added accordingly, which has increased the development workload.

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Calculation of bearing lubricant quantity and design of oil supply mode

4.1 Calculation of bearing lubricant quantity
The amount of oil required to lubricate a rolling bearing depends to a large extent on the type of bearing, the design of the fuel supply system, and the type of lubricant. It is difficult to give a simple and straightforward formula that is suitable for any situation and has wide applicability. Bearings with automatic oil transfer (such as angular contact ball bearings) require more oil than bearings that do not have automatic oil transfer (such as double row cylindrical roller bearings). Especially when the value of the velocity coefficient (n.dm) is large, the difference is more obvious (Fig. 3). Through a large number of experiments, the rough calculation formula of the fuel supply quantity Q is as follows:
Figure 4 oil supply method
Q=WdB
Where Q - oil supply, mm3 / h
W——coefficient, 0.01mm/h
D——bearing inner diameter, mm
B——bearing width, mm
However, the actual oil supply should be expanded by 4 to 20 times based on this value. In order to obtain the best lubrication effect, it is necessary to experiment to correct the amount of oil supply.
4.2 Oil supply design
For high-speed rotating bearings, in order to reliably feed the lubricating oil into the bearing, the design of the oil supply method (such as nozzle form, installation position, etc.) should be taken very seriously. The way the bearings are lubricated depends entirely on the type and configuration of the bearings (Figure 4a). For single row bearings, the best way to lubricate is to enter the inside of the bearing from one side. The nozzle hole should be flush with the inner ring and should not point to the cage. Especially when the bearing's own suction and discharge direction is not easy to determine (such as angular contact ball bearings), the lubricant must enter the bearing inside in the above direction. If conditions permit, the lubricant preferably passes through a special nozzle before entering the bearing. The length of the nozzle depends on the size of the bearing and the diameter is 0.5 to 1.0 mm. It is also allowed to send the oil to the outer ring of the bearing (Fig. 4b). In this case, pay attention to see if the lubricant enters the pressure zone formed between the steel ball and the outer ring. For double row bearings, the lubricant must be sprayed into the bearing from the side of the outer ring raceway to adequately lubricate the bearings.
When the outer diameter of the bearing is between 150 and 280 mm, an additional nozzle is required.
In addition, in order to prevent the formation of oil sludge deposits at the bottom of the bearing, it is necessary to install a drain pipe whose length is greater than 5 mm.
In order to meet the requirements of the lubrication system of the high-speed spindle of modern machine tools, further detailed and accurate research on the parameters of the oil-gas centralized lubrication system is required. This is because: the type of lubricant, lubrication method, amount of lubrication, bearing type, bearing configuration and other factors have a decisive effect on the increase of bearing speed.

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