Method of grinding and turning workpiece
The method addresses the inefficiencies of conventional grinding and turning methods by using eccentric positioning and automated setup to enhance flexibility and efficiency in manufacturing operations, particularly for low-volume production.
Patent Information
- Application Number
- JP2025088512
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2019-10-24
- Filing Date
- 2025-05-28
- Publication Date
- 2025-09-05
AI Technical Summary
Conventional methods for grinding and turning bearing rings, such as the centerless shoe approach and hammer-based methods, require time-consuming and skilled setup processes, making them less suitable for low-volume manufacturing operations and lacking flexibility.
A method involving eccentric positioning of the workpiece on a chuck, determining an offset between the chuck's rotational axis and the workpiece axis, and calculating an engagement path for the grinding or turning tool, eliminating the need for manual manipulation and shoe-based holding, thus enabling faster setup and increased flexibility.
The method achieves efficient grinding and turning operations with reduced setup time, suitable for both low and high-volume manufacturing, and maintains consistent contact with the workpiece without the use of shoes, enhancing manufacturing flexibility and efficiency.
Smart Images
Figure 2025130078000001_ABST
Abstract
Description
[Technical Field]
[0001] Cross-reference to related patent applications
[0001] This application is related to U.S. Provisional Patent Application No. 62 / 925,2 filed on October 24, 2019. This is a Patent Cooperation Treaty international patent application claiming priority to Patent Cooperation Treaty International Patent Application No. 85, the entire contents of which are incorporated herein by reference.
[0002]
[0002] This disclosure relates generally to the manufacture of metal workpieces, and more particularly to the manufacture of metal bearing wires. The present invention relates to a method for grinding and turning workpieces and other metal workpieces having an annular portion. [Background technology]
[0003]
[0003] A bearing is a device that supports friction between two parts with relative motion, most often rotational motion, between the parts. A bearing is a mechanical device used to reduce friction. Depending on the type, bearing components can include inner and outer bearing rings. The surface quality and close dimensional accuracy resulting from the manufacturing operations of grinding and finishing bearing rings and other components are key to ensuring bearing life. Grinding is typically performed on the inner and outer diameters of bearing rings, as well as raceways, ribs, chamfers, and grooves as needed. Grinding is also typically performed on other metal workpieces that have annular portions.
[0004]
[0004] A conventional approach to grinding bearing rings is known as the shoe centerless approach. The centerless shoe approach involves holding a bearing ring in an off-center position on a magnetic chuck. The bearing ring is held in place by a shoe. While effective, this approach is not without drawbacks. Grinding effectiveness is highly sensitive to the relationship between the contact angle between the grinding wheel and the workpiece and the contact angle between the shoe and the workpiece. Additionally, grinding wheels tend to wear over time, making it increasingly difficult to maintain good grinding conditions. These relationships require a rigorous and time-consuming setup process performed by highly skilled operators. Due to the cumbersome setup process, the centerless shoe approach is most ideal for high-volume manufacturing operations and less suitable for low-volume manufacturing operations and those requiring increased changeover and flexibility.
[0005] Another known approach to grinding or turning bearing rings is to use a hammer. This involves centering the bearing ring in the magnetic chuck by manually threading the bearing ring or by moving the bearing ring with a computer numerically controlled (CNC) extrusion device. Again, this approach has drawbacks. It also requires a precise and time-consuming set-up process. This approach has been adopted for low-volume manufacturing operations. Summary of the Invention [Means for solving the problem]
[0006]
[0006] The performance of the method for grinding or turning a workpiece may involve several steps. The workpiece has one or more annular portions. One step may include placing the workpiece on the chuck with the chuck's rotational axis eccentrically positioned relative to the workpiece axis in the annular portion. Another step may include determining an offset between the chuck's rotational axis and the workpiece axis based on the eccentric position between the chuck's rotational axis and the workpiece axis. Yet another step may include determining an engagement path of the grinding wheel relative to the workpiece based on a predetermined offset between the chuck's rotational axis and the workpiece axis.
[0007] Another implementation of a method for turning a workpiece may involve several steps. The workpiece has one or more annular portions. One step may include placing the workpiece on the chuck with the chuck's rotation axis positioned eccentrically relative to the axis of the workpiece in at least one annular portion. Another step may include determining an offset between the chuck's rotation axis and the workpiece axis as a result of the off-center position between the chuck's rotation axis and the workpiece axis. And another step may include determining an engagement path of a turning tool relative to the workpiece based on the determined offset between the chuck's rotation axis and the workpiece axis. [Brief explanation of the drawings]
[0008] [Figure 1] 1 is a schematic diagram of an embodiment of a step in a method for grinding a bearing workpiece. [Figure 2]
[0009] 3A-3C are schematic diagrams of the steps of a method for grinding a bearing workpiece. [Figure 3]
[0010] 4 is a schematic diagram of another step of a method for grinding a bearing workpiece. [Figure 4]
[0011] 10 is a schematic diagram of yet another step of a method for grinding a bearing workpiece. [Figure 5]
[0012] 10 is a schematic diagram of yet another step of a method for grinding a bearing workpiece. DETAILED DESCRIPTION OF THE INVENTION
[0009]
[0013] Referring now to the figures, embodiments of methods for grinding and turning bearing workpieces are generally illustrated and described herein. Compared to previous approaches, the methods described herein are more suitable for lower volume manufacturing operations, such as producing 1-1000 parts, but also for higher volume manufacturing operations. The methods for grinding and turning bearing workpieces have a faster set-up process than previous approaches, do not require any degree of manual manipulation of the bearing workpiece, and may completely eliminate the use of shoes to hold the bearing workpiece in place. Thus, increased changeover and increased flexibility of manufacturing operations are achieved. The methods for grinding and turning bearing workpieces are more efficient and effective than previous approaches. The methods can have more, fewer, and / or different steps than those described herein in various embodiments, and depending on the precision bearing workpiece being subjected to the grinding or turning operation, as the case may be.
[0010]
[0014] 1 and 2 illustrate an embodiment of the first step in the method. The first step involves positioning a bearing workpiece 10 on a chuck 12. The bearing workpiece 10 can be an inner bearing ring, an outer bearing ring, or some other metallic annular bearing component. While the chuck 12 is a magnetic chuck in this embodiment, the chuck 12 can also be a different type of chuck, such as a mechanical chuck. One advantage of a magnetic chuck is that, when employed without a shoe, areas of the bearing workpiece 10 are not physically blocked from grinding with a shoe, fixture, or other holding object. Also, in some embodiments, shoes, fixtures, or other holding objects can be used in the methods detailed herein. The bearing workpiece 10 can be initially placed directly into position on the back plate 14 of the chuck 12 via automated or manual techniques, such as robotics, an integrated loader, or manual operation by an operator. At this stage, the bearing workpiece 10 can be in a so-called black state, in which the bearing workpiece 10 has been machined and hardened and its flat surfaces have been ground with a disk. Once in place, the chuck 12 can initially lightly hold the bearing workpiece 10 for the placement step.
[0011]
[0015] Placing the bearing workpiece 10 on the chuck 12 roughly centers the bearing workpiece 10 in the chuck 12. In some embodiments, for example, the axis of rotation 16 of the chuck 12 is eccentrically positioned relative to the axis 18 of the bearing workpiece 10, resulting in an optimal concentricity within approximately 1.0 millimeter (mm) or approximately 50 micrometers (μm). In use, the chuck 12 rotates about its axis of rotation 16, and the axis 18 of the bearing workpiece 10 is its circular central axis. Due to the off-center positioning, the axis 18 moves in an eccentric path as the chuck 12 rotates. In this embodiment, the rough centering is accomplished via a pair of centering vees, namely, first centering vee 20 and second centering vee 22, which come together ( FIG. 2 ) and engage with bearing workpiece 10 to guide bearing workpiece 10 into an approximately centered position relative to chuck 12. The first and second centering vees 20, 22 then move back. In the approximately centered position, the axis of rotation 16 of chuck 12 and the axis 18 of bearing workpiece 10 are slightly offset and offset relative to one another. Other types of procedures for positioning and roughly centering bearing workpiece 10 on chuck 12 are also possible; for example, the positioning and roughly centering can be accomplished via a shoe element centering mechanism and / or a contact member. Regardless of the type of positioning and roughly centering procedure employed, once chuck 12 is tightened, a strong holding force is exerted on bearing workpiece 10. In the case of a magnetic chuck, the magnetic setting should be increased to approximately 100-150 Newtons per square centimeter (N / cm 2 ) but of course other magnitudes of holding force are possible.
[0012]
[0016] 3 and 4 illustrate an embodiment of another step in the method for grinding and turning a bearing workpiece 10. This step involves determining an offset 24 between the axis of rotation 16 of the chuck 12 and the axis 18 of the bearing workpiece 10. The offset 24 is a result of the alignment and rough centering procedure of the previous step. This step of determining the offset 24 can include various techniques in different embodiments. In one embodiment, a probe 26 is employed to take a measurement of the outer diameter 28 of the bearing workpiece 10. Measuring the outer diameter 28 is in preparation for performing a grinding or turning operation on the outer diameter; as another example, the inner diameter may be the subject of measurement for grinding or turning the inner diameter of the bearing workpiece 10. The probe 26 can be a contact-based or non-contact-based measurement device. For example, the probe 26 can be a linear variable differential transformer (LVDT) gage, an eddy current probe, an encoder probe, an inductive sensor, a laser triangulation sensor, or a confocal sensor, to name a few. FIG. 4 schematically illustrates multiple measurements 30 taken by a probe 26 of the outer diameter 28 of an example bearing workpiece 10. The probe 26 in this example was an inductive probe type. The measurements 30 could be taken as the bearing workpiece 10 is driven to rotate via the chuck 12, while the measuring device remains stationary, or alternatively, the measuring device itself could rotate around the bearing workpiece 10; however, the exact measurement technique may depend on the measuring device used. In this embodiment, a controller 32 ( FIG. 3 ), such as a computer numerically controlled (CNC) controller, receives the measurements 30 and generates a polar coordinate system (θ, r) via a polar data table. Calculations can then be performed in the controller 32 to determine the position and orientation of the axis 18 of the bearing workpiece 10. The exact calculation may depend on the expected magnitude of the offset 24. That is, for example, a least-squares fit approach based on the measurements 30 could be utilized to determine the axis 18 of the bearing workpiece, or another similar algorithm could be used.Also, due to the smaller expected magnitude of the offset 24, the average of the measurements 30 can be utilized to determine the vector length of the offset 24 and the minimum / maximum position of the angle of the offset 24. Once the axis 18 of the bearing workpiece 10 is determined, its position is compared to the position of the rotation axis 16 of the chuck 12. The axis of rotation 16 of the chuck 12 may have a known value based on the particular chuck selected for use and the center of its work head.
[0013]
[0017] Another step in the method for grinding and turning a bearing workpiece 10 is shown in FIG. 5. This step involves determining an engagement path 34 for a grinding wheel 36 relative to the bearing workpiece 10. This determination is based on a predetermined offset 24 between the chuck's rotational axis 16 and the bearing workpiece's axis 18. The engagement path 34 is the line of travel along which the grinding wheel 36 moves to engage the bearing workpiece 10 to remove material from the bearing workpiece 10 during the grinding operation. The engagement path 34 guides the grinding wheel 36 to grind into the outer diameter 28 of the bearing workpiece 10 or the inner diameter of the bearing workpiece 10, as well as raceways, ribs, chamfers, and grooves of the bearing workpiece 10, as needed. The offset 24 causes the bearing workpiece 10 to rotate about an eccentric path as the chuck 12 rotates during use. The grinding wheel 36 moves along its determined engagement path 34 to accommodate the eccentric path of the rotating bearing workpiece 10 in order to maintain a point of contact with the bearing workpiece 10. Thus, the point of contact between the grinding wheel 36 and the bearing workpiece 10 is maintained around the entire circumference of the bearing workpiece 10. The engagement path 34 is determined by the controller 32. The movement of the grinding wheel 36 can be via one or more servo motors or some other type of mechanism that operatively interacts with the grinding wheel 36. In this embodiment, the engagement path 34 is a linear path and is simply the back-and-forth path of the grinding wheel 36 toward and away from the bearing workpiece 10. In other words, the grinding wheel 36 simply moves back and forth. The back-and-forth movement is horizontal as shown in FIG. 5, but could be along any linear path disposed normal to the bearing workpiece 10, including non-horizontal paths.
[0014]
[0018] In addition to the offset 24, determining the engagement path 34 is a calculation that can take into account other factors that affect the determination of the engagement path 34 and maintaining the contact point between the grinding wheel 36 and the bearing workpiece 10. In different embodiments, in some instances, depending on the precision chuck 12 employed in the method, the determination of the engagement path 34 can include correction factors for specific geometric errors, such as centerline height error of the grinding wheel spindle, compensation for the diameter of the grinding wheel 36, and / or correction factors based on the inherent imprecision and tolerances of the chuck 12 or larger chuck machine of the rotary shaft 16, among other possible factors. Furthermore, in shoeless embodiments, the chuck 12 may be selected to exhibit sub-micron rotational accuracy to ensure roundness accuracy of the bearing workpiece 10. An isostatic work spindle or grinding wheel spindle may be required in some embodiments. In certain embodiments, a scrubber may also be employed to supplement the cleanliness of the grinding wheel 36.
[0015]
[0019] Also, other embodiments of the method may involve additional and / or different steps. For example, in embodiments, the method may include maintaining a grinding force GF (FIG. 5) below a threshold force to eliminate undesired movement of the bearing workpiece 10 on the backplate 14 during operation and relative to the chuck 12. This grinding force GF is directed perpendicular to the bearing workpiece 10, as shown in FIG. 5. The threshold force may be one that overcomes the holding effort of a magnetic chuck when a magnetic chuck option is used and when no shoe is used to hold the bearing workpiece 10. Furthermore, in embodiments of the method, the method may be repeatedly re-run with finer abrasive grinding wheels on a single chuck 12, rather than having to introduce the bearing workpiece 10 into separate and discrete chucking machine setups at different locations as is conventional.
[0016]
[0020] As described, the method and its various steps may be employed to grind the bearing workpiece 10 or to turn the bearing workpiece 10. For turning operations, instead of grinding wheel 36, a cutting tool may be used to engage and remove material from bearing workpiece 10. Turning may be performed on the outer diameter 28 of bearing workpiece 10 or the inner diameter of bearing workpiece 10, as well as on raceways, ribs, chamfers and grooves of bearing workpiece 10, as needed.
[0017]
[0021] Furthermore, while the grinding and turning methods and various steps thereof have been described with reference to bearing workpieces, the methods have broader applicability and can be performed on non-bearing metal workpieces having annular portions. Furthermore, the methods can be performed on non-annular profile portions on certain bearing workpieces, such as those found in aerospace applications. In this example application, the annular profile portion of the bearing workpiece serves as a reference position for grinding or turning the non-annular profile portion. In the steps described above, the first step is performed as described, i.e., the bearing workpiece is placed on the chuck via its annular profile portion. The next step would involve determining the offset between the rotation axis of the chuck and the axis of the bearing workpiece by taking measurements of the annular profile portion, as described. In a subsequent step, not previously described, the reference position of the annular profile portion relative to the non-annular profile portion would be incorporated into the step of determining the engagement path of the grinding wheel or cutting tool. In an embodiment, the reference position of the annular profile portion relative to the non-annular profile portion may be the axial displacement between the two portions and / or the radial displacement between the two portions, or some other displacement of the grinding wheel or cutting tool prior to moving the wheel / tool on an engagement path to remove material from the bearing workpiece.
[0018]
[0022] Having thus described the method, various modifications and variations will occur to those skilled in the art and are intended to fall within the scope of the appended claims.
Claims
1. 1. A method for grinding a metal workpiece having at least one annular portion, comprising: placing the workpiece on the chuck with an axis of rotation of the chuck positioned eccentrically relative to an axis of the workpiece in the at least one annular portion; determining an offset between the rotation axis of the chuck and the axis of the workpiece as a result of an off-center position between the rotation axis of the chuck and the axis of the workpiece; determining an engagement path of a grinding wheel relative to the workpiece based on the determined offset between the rotational axis of the chuck and the axis of the workpiece.
2. 10. The method of claim 1, wherein the workpiece is a bearing workpiece.
3. 3. The method of claim 2, further comprising engaging the bearing workpiece with the grinding wheel at an outer diameter of the bearing workpiece, an inner diameter of the bearing workpiece, a raceway of the bearing workpiece, a rib of the bearing workpiece, a chamfer of the bearing workpiece, or a groove of the bearing workpiece.
4. 10. The method of claim 1, wherein the step of placing the workpiece on the chuck includes engaging the workpiece with at least one centering V-member.
5. 10. The method of claim 1, wherein the step of placing the workpiece on the chuck does not involve a shoe.
6. The method of claim 1 , wherein the chuck is a magnetic chuck.
7. 2. The method of claim 1, wherein determining the offset between the axis of rotation of the chuck and the axis of the workpiece comprises determining the offset using a polar coordinate system.
8. 10. The method of claim 1, wherein determining the offset between the axis of rotation of the chuck and the axis of the workpiece comprises determining the offset via a contact or non-contact sensor.
9. 2. The method of claim 1, wherein determining the offset between the axis of rotation of the chuck and the axis of the workpiece comprises measuring a diameter of the workpiece.
10. 2. The method of claim 1, wherein determining the offset between the rotational axis of the chuck and the axis of the workpiece comprises determining a bearing workpiece axis.
11. 11. The method of claim 10, wherein determining the axis of the workpiece comprises determining the axis of the workpiece via a least squares fit approach.
12. 2. The method of claim 1, wherein the predetermined distance of the grinding wheel relative to the workpiece is wherein the determined engagement path is simply the reciprocating engagement path of the grinding wheel towards and away from the workpiece.
13. 2. The method of claim 1, wherein the determined engagement path of the grinding wheel relative to the workpiece is a horizontal engagement path of the grinding wheel toward and away from the workpiece.
14. 2. The method of claim 1, wherein the determined engagement path of the grinding wheel with the workpiece is an engagement of a non-annular portion of the workpiece, and the engagement path is determined based on a reference position of the non-annular portion with respect to the at least one annular portion.
15. 10. The method of claim 1, further comprising maintaining a grinding force directed perpendicularly to the workpiece below a threshold force to eliminate undesired movement of the workpiece relative to the chuck.
16. 1. A method of turning a workpiece having at least one annular portion, comprising: placing the workpiece on the chuck with an axis of rotation of the chuck positioned eccentrically relative to an axis of the workpiece in the at least one annular portion; determining an offset between the rotation axis of the chuck and the axis of the workpiece as a result of an off-center position between the rotation axis of the chuck and the axis of the workpiece; determining an engagement path of a turning tool relative to the workpiece based on the determined offset between the rotational axis of the chuck and the axis of the workpiece.