Selection of motorized spindle bearing for engraving machine
Engraving machine spindle bearing
Computer controlled engraving machines are more and more popular. They are widely used to carve working doors and windows, heavy and thick molds for mechanical work, molds for plastic work, and engraving, milling and grinding of mobile phone glass panels. In the past, this kind of engraving machine was mainly imported, but now the domestic engraving machine has made great progress. Therefore, the production of motorized spindle used in carving machine is gradually localized. However, because most of our country's carving machine spindle prototypes are imported from abroad, its original high-speed bearings are also supplied by some foreign bearing manufacturers, such as fag, SKF, NSK, snfa, GMN, etc. In the process of localization, because the spindle production enterprises are not very familiar with the selection of bearings, there are often wrong selection and misuse, which cause unnecessary trouble to the end users. Therefore, it is necessary to analyze the consequences of wrong selection of bearings for machine motorized spindle bearing from the perspective of theory.
2、 Misunderstanding of bearing selection -- super high speed bearing is selected for general high speed bearing
Most bearings in high-speed shafting use angular contact ball bearings. These bearings have the same external dimension (i.e. inner diameter, width) and many internal structures, such as general angular contact ball bearings, high-speed angular contact ball bearings and ultra-high-speed angular contact ball bearings. The big difference is the size of the rolling body (ball). The ball diameter of general angular contact ball bearings is larger, The ball diameter of high-speed angular contact ball bearing is medium, the ball diameter of ultra-high-speed angular contact ball bearing is small, the limit speed increases gradually, and the dynamic load (CR) decreases. In addition, the rolling body data can be divided into two categories: bearing steel ball and ceramic ball, and the cage data can be divided into metal cage and engineering plastic cage. In addition, the contact angle is also divided into 15 degrees, 25 degrees, 30 degrees, 40 degrees, 60 degrees, etc. in order to get different stiffness, the preload of assembled bearing is divided into light, medium and heavy. In a word, the selection of angular contact ball bearing is more messy than other general bearings. Now there are limit speed, dynamic load capacity, contact angle, preload and so on. However, the main mistake of Zui is that the relationship between the limit speed and the dynamic load capacity can't be straightened out. The problem is that the limit speed is more than the dynamic load capacity, which shortens the service life. More appropriately, the general high-speed 70 series should be selected instead of the H70 series.
3、 A theoretical analysis of the disorder of the number of years of life
At present, the rotational speeds of the mechanical and electrical spindles are more than 24000 rpm and 18000 rpm. We take the 24000 RPM spindle as the representative to compare h7004 ~ h7008 and 7004 ~ 7008.
All types of operation under DT matching method, the operating speed can reach 24000 rpm. However, the ball diameter of general high-speed bearing is much larger than that of super high-speed bearing, and the corresponding dynamic load capacity is also much larger. Under the same operation conditions, the service life must be longer.