The so-called micro bearing is the small bearing, mainly refers to the metric series, the outside diameter is less than 9mm;Inch series, the outer diameter is less than 9.525mm of all kinds of bearings, of which the inner diameter can be as small as 0.6mm, the general inner diameter of 1mm more.
Common materials of miniature bearings are: carbon steel, bearing steel, stainless steel, plastics, ceramics, etc.
Miniature bearing USES: applicable to all kinds of industrial equipment, small rotary motor of high speed low noise field, such as: office equipment, micro motor, instrument, laser engraving, small clock, soft drive, pressure rotor, dental drill, drive motor, stepping motor, VCR magnetic drum, toy models, computer cooling fan, paper, fax machine, and so on related areas.
The reasons why miniature bearings fail are as follows:
1. Oval indentation caused by the ball vibration between the micro-bearing rings when the micro-bearing is not rotating.This damage is called a low - charge erosion.This damage occurs both in equipment in transit and in equipment that vibrates when not in operation.In addition, the debris generated by the low-load vibration erosion ACTS like abrasive particles and further damages the micro bearing.Different from denudation, the characteristic of low charge vibration erosion is usually the reddish color produced by micro-vibration wear corrosion in lubricant.
Solution: Eliminating vibration sources and maintaining good micro-bearing lubrication can prevent low load vibration erosion.Adding isolation pads to the equipment or isolating the base can reduce the vibration of the environment.In addition, adding a small pre-load on the micro bearing not only helps to keep the ball in close contact with the micro bearing ring, but also helps to prevent low-load vibration erosion during equipment transportation.
2. The causes of the micro-bearing sticking are lack of internal gap, improper lubrication and excessive load.Excessive friction and heat soften the miniature bearing steel before it becomes stuck.Overheated miniature bearings usually change color, usually turning blue-black or yellowish.Friction also forces the retainer, which can damage the support and accelerate the failure of the miniature bearings.
3. Premature fatigue failure of materials is caused by excessive preloading after heavy loading.If these conditions are unavoidable, the life of the miniature bearing should be carefully calculated to develop a maintenance plan.
Another solution is to change the material.Special materials should be used if standard micro bearing materials cannot guarantee sufficient micro bearing life.In addition, if the problem is caused by excessive load, a more robust or other structure of the miniature bearing should be used.
Peristalsis is not as common as premature fatigue.Peristalsis of miniature bearing is caused by the large clearance between shaft and inner ring.Peristalsis is harmful in that it damages not only the miniature bearings but also other parts.
Peristalsis is marked by a scratch, a scratch, or a change in color between the axis and the inner ring.To prevent creep, the miniature bearing cases and shaft fittings should first be visually inspected.
Peristalsis is related to improper installation.If the miniature bearing ring is out of alignment or tilted, the ball will move along a non-circular path.The problem is due to incorrect mounting or tolerances or insufficient verticality at the micro-bearing installation site.If the deflection exceeds 0.25", the miniature bearing will fail prematurely.Inspecting lubricants for contamination is much more difficult than inspecting assembly irregularities or peristalsis.Contamination is characterized by premature wear of miniature bearings.Solid impurities in the lubricant act like abrasive particles.Poor lubrication between the ball and cage may also wear out and weaken the cage.In this case, lubrication is essential for a fully machined form of cage.In contrast, ribbon or coronal retainers allow the lubricant to reach all surfaces more easily.
Rust is a form of moisture pollution and its presence often indicates an improper choice of material.If a material is tested to fit the requirements of the job, the easiest way to prevent rust is to pack the miniature bearings and not open them until they are installed and used.
Methods to avoid miniature bearing failure:
The best way to solve the problem of miniature bearing failure is to avoid failure.This can be achieved by considering key performance characteristics during selection.These features include noise, starting and running torques, rigidity, unrepeatable oscillations, and radial and axial gaps.
Torque requirements are determined by lubricants, retainers, quality of miniature bearing rings (roundness and surface finish of curved parts), and the use of seals or shields.The viscosity of the lubricant must be carefully chosen.
Because inappropriate lubricants can produce excessive torque, this is especially true in small and micro bearings.In addition, different lubricants have different noise characteristics.For example, grease produces more noise than lubricating oil.Accordingly, want to choose lubricant according to different use.
If there is a random eccentricity between the inner ring and the outer ring during the rotation of the micro-bearing, a non-repetitive vibration pendulum (NRR) very similar to the CAM motion will be generated.The size error of the retainer and the eccentricity of the miniature bearing rings and ball bearings can cause NRR.NRR, unlike the repetitive pendulum, has no way to compensate.
In industry, micro-bearings of different types and precision grades are generally selected according to specific applications.For example, when minimum oscillations are required, the non-repetitive oscillations of miniature bearings cannot exceed 0.3 microns.Similarly, machine tool spindles can only allow minimum oscillations to ensure cutting accuracy.Therefore, in the application of machine tools, the micro-bearing with small non-repetitive oscillating pendulum should be used.
In many industrial products, pollution is inevitable, so sealing or shielding devices are often used to protect the miniature bearings from dust or dirt.However, because of the movement of the inner and outer rings of the micro-bearing, the sealing of the micro-bearing cannot reach a perfect degree, so the leakage and pollution of lubricating oil is always an unsolved problem.
Once the micro-bearing is contaminated, the lubricant will deteriorate and the operating noise will become louder.If the miniature bearing overheats, it will get stuck.When the contaminant is between the ball and the micro-bearing ring, it ACTS like the abrasive particles between the metal surface, causing the micro-bearing to wear out.One way to control pollution is to use seals and shields to block out dirt.
