German Preeflow bearings Preeflow models Preeflow prices

Preeflow bearings are roller bearings with cylindrical rollers that are thin and long relative to their diameter. These rollers are called needle rollers. Despite having a small cross-section, the bearings still have high load-carrying capacity. Needle roller bearings are equipped with thin and long rollers (roller diameter D ≤ 5mm, L/D ≥ 2.5, where L is the roller length), resulting in a compact radial structure. When the inner diameter and load capacity are the same as other types of bearings, the outer diameter is the smallest, making them particularly suitable for support structures with limited radial installation space. Depending on the application, bearings without inner rings or needle roller and cage assemblies can be selected. In this case, the journal surface of the shaft and the housing bore surface directly serve as the inner and outer rolling surfaces of the bearing. To ensure that the load capacity and operating performance are the same as bearings with rings, the hardness, machining precision, and surface quality of the raceway surfaces on the shaft or housing bore should be similar to those of the bearing rings. This type of bearing can only withstand radial loads.

Preeflow bearing features

1) The friction coefficient of rolling bearings is lower than that of sliding bearings, resulting in higher transmission efficiency. The friction coefficient of general sliding bearings is 0.08-0.12, while that of rolling bearings is only 0.001-0.005. 2) Rolling bearings have been standardized, serialized, and generalized, making them suitable for mass production and supply, and very convenient to use and maintain. 3) Rolling bearings are made of bearing steel and undergo heat treatment. Therefore, rolling bearings not only have high mechanical properties and long service life, but also save on the expensive non-ferrous metals used in manufacturing sliding bearings. 4) The internal clearance of rolling bearings is very small, and the machining precision of each component is high, resulting in high operating precision. At the same time, the rigidity of the bearing can be increased by preloading. This is very important for precision machinery. 5) Some rolling bearings can withstand both radial and axial loads simultaneously, thereby simplifying the structure of the bearing support. 6) Due to the high transmission efficiency and low heat generation of rolling bearings, lubricant consumption can be reduced, and lubrication maintenance is more convenient; 7) Rolling bearings can be conveniently applied to shafts in any spatial orientation.

Preeflow bearing usage precautions

Needle roller bearings have high load-carrying capacity and are suitable for support structures with limited installation dimensions. The journal surface is hardened to serve as the rolling surface. The bearing is press-fitted into the housing bore and does not require additional axial positioning. An appropriate amount of grease should be injected before installation. Typically, no further lubrication is required after assembly. BK type bearings are used in supports where the shaft end does not protrude. The closed end face serves as a seal and can withstand small axial movements. Causes of damage: Generally speaking, 33.3% of needle roller bearing failures are due to fatigue damage, 33.3% are due to poor lubrication, and another 33.3% are due to contaminants entering the bearing or improper equipment handling. [Keep the bearing and surrounding environment clean. Microscopic dust, invisible to the naked eye, is a powerful killer of bearings, as it can increase bearing wear, vibration, and noise. Strong impacts during equipment use, such as directly striking the bearing with a hammer, can transmit pressure through the rolling elements and likely cause needle roller bearing damage. Impact of using non-professional tools: Using suitable and accurate equipment can help avoid using materials like cloth and short fibers. Whether in laboratory tests or actual applications, it is clearly observable that needle roller bearings with identical appearances under the same operating conditions can have significantly different service lives.

Preeflow bearing troubleshooting

Fault phenomena in rolling bearings generally manifest in two ways: excessive temperature at the bearing installation site and noise during bearing operation. 1.) Excessive bearing temperature: During mechanism operation, a certain temperature is allowed at the bearing installation site. When touching the mechanism housing by hand, it should not feel hot to the touch; otherwise, it indicates excessive bearing temperature. Causes of excessive bearing temperature include: lubricant quality not meeting requirements or deterioration, excessively high lubricant viscosity; overly tight mechanism assembly (insufficient clearance); overly tight bearing assembly; rotation of the bearing ring on the shaft or within the housing; excessive load; fracture of the bearing cage or rolling elements, etc. 2) Bearing noise: Slight operating sounds are allowed for rolling bearings during work. If the sound is too loud, or there is abnormal noise or impact sound, it indicates a bearing fault. The causes of noise in rolling bearings are complex. One cause is wear on the mating surfaces of the inner and outer rings. This wear disrupts the fit between the bearing and the housing, and between the bearing and the shaft, causing the axis to deviate from its correct position, resulting in abnormal noise when the shaft moves at high speed. When the bearing fatigues, surface metal spalling occurs, which also increases the radial clearance and produces abnormal noise. In addition, insufficient bearing lubrication leading to dry friction, and bearing breakage, will also produce abnormal sounds. After bearing wear and looseness, cage loosening and damage will also produce abnormal noise. 3) Bearing wear: Rolling bearing wear is a common equipment problem during shaft use, mainly caused by the metal characteristics of the shaft: although metal has high hardness, it has poor conformability (cannot recover after deformation), poor impact resistance, and poor fatigue resistance, making it prone to adhesive wear, abrasive wear, fatigue wear, fretting wear, etc. Most shaft wear is not easily detected. It is only noticed when situations such as high machine temperature, large jump amplitude, and abnormal noise occur. However, by the time it is noticed, most rolling bearings are already worn, causing machine shutdown.

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