(1) Temperature conditions during measurement
The ambient temperature during measurement is specified as 20°C. The temperature of FAG bearings, gauge blocks, standard parts and measuring instruments must all be the same. The above method of putting them on the same metal plate can quickly achieve the necessary temperature balance. Otherwise, it will take several hours or even days to reach such a balance.
In order to obtain the correct measurement results, foreign countries rely on the mechanization of measurement to prevent human hands from touching these objects, or wearing heat-resistant gloves for operation.
(2) Regulations of measurement area
For the measurement of the inner diameter or outer diameter of FAG bearings, it is stipulated in China to measure within the area with the largest chamfering coordinate away from the south end of the ring, while in foreign countries, it is mostly specified as the area leaving the two ends of the ring with twice the chamfering coordinate. Measure within.
(3) Regulations on dimensional standards
When using the comparative measurement method to measure the dimensional tolerance of FAG bearings, the gauge block or standard part is specified as the size benchmark for comparison measurement. The gauge block must meet the requirements of the standard JB/T1078 "gauge block", and the standard part must conform to the manufacturer's supervisor Departmental regulations.
(4) Regulations for measuring instruments
The instrument used in the measurement must be calibrated, and have an accuracy and amplification ratio compatible with the measured FAG bearing.
(5) Allowable measurement error
In principle, the measurement error can be allowed to be less than 10% of the tolerance.
(6) Probe radius and gauge pressure
In order to reduce the measurement error, it is necessary to reduce the pressure-measurement force of the gauge and increase the radius of curvature of the probe within the possible range.
When measuring the inner and outer diameters of FAG bearings, the measuring force used and the radius of curvature of the probe can be selected by reference.
(7) Mandrel used for measurement
When measuring the Kia, Kea and Sd items of bearings, for cylindrical bore bearings, the taper of the taper mandrel used is in principle specified as 1/5000-1/10000. For uranium bearings with tapered bore, the basic taper of the taper mandrel used is specified It is 1/12.
(8) Provisions for measuring load
When measuring Kia, Kea, Sia, Sea and other items, it is necessary to apply the necessary measurement load to make the rolling element and the ring in the normal contact position to obtain a stable measurement value.
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(1) The use of chemical additives to add certain chemical additives to the lubricant of FAG bearings can reduce bearing noise. For example, a low-noise grease containing noise-reducing additives produced by a factory in Tianjin can reduce bearing noise from the original Reduced by 3.9~9.2dB on the basis of, it is suitable for use in miniature or small bearings.
(2) Use vibration absorbing or isolating device. Using vibration absorbing or isolating device to reduce the noise of FAG bearings or isolate bearing noise can get good results, but this often pays a great price in economy, and sometimes makes the mechanism larger and heat dissipation conditions. Deterioration, or easy to rust, should be fully considered when using, and this method should only be used after other measures are taken and the low noise index cannot be achieved. The simplest example is a radial ball bearing that can take the thrust instead of a thrust bearing at high speed. The outer ring can be covered with a plastic jacket that is full of rust-proof lubricating oil. A thrust bearing with a cover or a general thrust bearing is allowed In this case, the inner hole or outer circle is inlaid with the same plastic sleeve, but the control should not rub or interfere with adjacent parts during rotation. This method has a certain muffling effect. Another example is to add an intermediate sleeve between the bearing and the housing hole, which can attenuate the vibration force transmitted from the rotating system to the bearing housing, but this requires proper adjustment, otherwise the opposite effect may occur.
Another example is to use a sound-absorbing and sound insulation cover to completely close or close the bearing system that generates noise as much as possible. The interior of this noise reduction cover is made of glass fiber or polyurethane foam, and the inner surface is a steel plate with a thickness of 0.6-lmm. The surface is evenly distributed with small through holes of φ1.2-1.5mm. The total area of the small holes accounts for about the entire inner surface. 25%-30% of the surface, the outer surface is a steel plate with a thickness of 2mm. Here, glass fiber or foam is used to eliminate higher frequency noise, the inner surface with small holes is used to eliminate lower frequency noise, and the thick steel plate on the outer surface is used to isolate the noise from outside.