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Abstract: An elastic floating support is proposed for grinding of bearing rings, and the structure and principle are analyzed. The comparison test shows that the buffing action of elastic floating support is able to avoid deformation of rings during processing, and the precision of product is effectively improved.
Key words: bearing ring; grinding; elastic floating support; machining precision
1 Floating support for grinding ring
1.1 Ordinary floating support
In the grinding process of the outer circle or inner groove (raceway) of the bearing ring (non penetrating centerless grinding), ordinary floating supports are currently mostly used to bear the radial force suffered by the ring during grinding. The floating support structure is shown in Figure 1, where the support seat is connected to the support head through pins. The floating support structure is simple, but it has the following drawbacks:
(1) When the grinding force is too large or the original roundness error of the ring is large, the ring deformation is very easy to occur during grinding, and the original deformation correction ability of the ring is poor.
1- Support seat; 2- Pin; 3- Support head
Figure 1 Schematic diagram of ordinary floating support structure
(2) Only one support head can be used, and the contact surface with the ring is small, resulting in low processing accuracy of the ring.
1.2 Elastic floating support
To address the shortcomings of the current floating support, an elastic floating support was designed, and its structure is shown in Figure 2. The support structure consists of a support seat, elastic floating block pins, elastic floating blocks, 2 support heads, and 2 support head pins. The support seat is fixed on the grinder fixture, and is connected to the elastic floating block through the elastic floating block pin; The elastic floating block is centered around the pin of the elastic floating block and can adjust a certain rotation angle relative to the support seat. Place the support head into the support head hole on the elastic floating block from top to bottom, and then connect it with the elastic floating block through the support head pin; The support head is centered on the support head pin, and the relative elastic floating block can adjust a certain rotation angle. There is a hard alloy block on the support head, which is welded with copper. The two support heads on the elastic floating block increase the envelope surface with the machined ring; There are two symmetrical notches on the elastic floating block, which are a combination of rectangular and circular arcs. When the grinding force is too large, the notches in the elastic floating block can increase elasticity, play a certain buffering role, and improve the machining accuracy of the workpiece.
1- Support seat; 2- Elastic floating block pin; 3- Elastic floating block; 4- Support
Head; 5- Support head pin
Figure 2 Schematic diagram of elastic floating support structure
2. Principle of Elastic Floating Support
The elastic floating support utilizes the elastic buffering effect of the floating support during the grinding process, reducing the elastic deformation of the ring during the grinding process, and avoiding the grinding deformation of the ring caused by large roundness errors of the ring blank. The force situation during ring grinding is shown in Figure 3, and the radial force (excluding the force caused by ring eccentricity) is
G=F left cos α + F right cos β， ( 1)
F grinding=F left sin α － F right sin β， ( 2)
In the formula, G represents the gravity of the ferrule; Fgrinding=9.81 × CfnZ0.7B0K hard; Cfn is the cutting force coefficient, with a value of 0.17; Z is the grinding amount per unit width; B0 is the width of the grinding wheel; Khard is the correction factor for the hardness of the grinding wheel, taken as 1.0 or 1.1; α,βis the included angle of the support.
Figure 3 Schematic diagram of force on ring grinding
During the grinding process of the ring, assuming that F grinding remains constant, the gravity of the ring remains basically unchanged. The floating support adopted has 2 support heads, reducing the wear of individual supports and improving the service life of the supports; When the roundness error of the ring is large, F grinding increases. At this time, the position where the elastic floating block is installed on the support head produces elastic deformation relative to the elastic notch or arc of the elastic floating block (Figure 4), which plays a role in elastic buffering. The ring will not deform during the grinding process. The supporting surface of the elastic floating support adopts a hard alloy material with the same curvature as the outer diameter of the workpiece, which changes the horizontal support of the workpiece from the original 4 face contact to 8 face contact during processing, effectively increasing the contact area of the collar and eliminating the surface ripple of the workpiece caused by the support; Due to the fact that the elastic floating head can rotate around the shaft to a certain extent, it can ensure good contact between the support and the workpiece at all times, thus obtaining high-quality machining surfaces and facilitating operator adjustment.
Figure 4 Elastic floating support state during ring grinding process
3. Design and Manufacturing of Supports
Except for the elastic floating support block, all other components are the same as the current support. The material of the elastic floating support block is 65Mn and subjected to quenching and tempering treatment. The depth of the elastic notch is determined by the size of the machined ring and the grinding force. For thin series products, large arcs can be used instead of elastic notches (Figure 5).
Figure 5 Large Arc Floating Support Block
4 Comparative tests
Grind the outer diameter surface of N1036 outer ring on a 3MZ2150 cylindrical grinder, and process 5 workpieces each with the same support position angle, eccentricity, and grinding speed. Compare the roundness of the workpieces after using traditional floating support and elastic floating support, and the results are shown in Table 1.
Table 1 Comparison of workpiece roundness after using different floating supports
Workpiece number Elastic floating support Traditional support
From Table 1, it can be seen that under the same conditions, the elastic floating support can effectively improve the roundness of the workpiece, especially for heavy and thin series products.
More about KYOCM Angular Contact Ball Bearing:
Angular contact ball bearings have inner and outer ring raceways that are displaced relative to each other in the direction of the bearing axis. This means that these bearings are designed to accommodate combined loads, i.e. simultaneously acting radial and axial loads.
The axial load carrying capacity of angular contact ball bearings increases as the contact angle increases. The contact angle is defined as the angle between the line joining the points of contact of the ball and the raceways in the radial plane, along which the combined load is transmitted from one raceway to another, and a line perpendicular to the bearing axis.
http://www.kyocm.com/products/Angular-Contact-Ball-Bearing/734.html
2023-04-28