Method and cylindrical grinding machine for centerless cylindrical grinding

Abstract

A method and a cylindrical grinding machine for centerless cylindrical grinding of a workpiece. The workpiece is supported on a first contact surface and a second contact surface arranged at an angle relative to one another. A grinding disk is applied to the workpiece with an application force, whereby the workpiece is in turn pressed against the first and second contact surfaces, which cause braking of the workpiece (which is rotationally driven solely by the grinding disk). The braking reduces the rotational speed of the workpiece such that the grinding disk produces grinding in addition to rotationally driving the workpiece. The rotational speed of the workpiece can be precisely set by means of an additional brake that applies an adjustable braking force to the workpiece.

Claims

1. A centerless cylindrical grinding machine, comprising: a grinding drive unit and a grinding disk that is mounted therein and is driven to rotate by the drive unit, wherein the grinding disk directly applies an application force on a workpiece in a feed direction of the grinding disk, thereby directly and exclusively driving the workpiece to rotate; a support device that is coupled to the workpiece and arranged to obstruct the rotational movement of the workpiece such that the workpiece is driven to rotate and is ground by the grinding disk responsive to the application force, wherein through the grinding drive unit, the grinding disk can be applied in the radial direction thereof against the workpiece having a rotationally symmetrical contour, and the support device comprises at least one first flat contact surface and one second flat contact surface, which are arranged to form a prism with the first and second contact surfaces forming oblique contact surfaces that are both operationally immobile in the circumferential direction of the workpiece, extend at a distance from one another along the workpiece, and encompass the workpiece under sliding contact in such a manner that the workpiece is held at an optimal position for the grinding process and the application force pushes the workpiece against the first and second flat contact surfaces, with one of the first and second flat contact surfaces disposed on an opposite side of the workpiece from the grinding disk in the feed direction; a brake arranged on the support device, the brake having a braking body that acts on the workpiece via an adjustment device with an adjustable braking force, wherein the adjustment device is an actuator controlling the clamping force of the braking body acting on the workpiece; a device for measuring rotational speed configured to constantly monitor the workpiece rotational speed; and an assessment and regulation arrangement configured to constantly maintain an optimal balance between the rotational speed of the grinding disk, the application force applied by the grinding disk, and the braking force applied by the braking body.

2. The cylindrical grinding machine according to claim 1, wherein: the first flat contact surface and the second flat contact surface are arranged so as to be totally operationally immobile.

3. The cylindrical grinding machine according to claim 1, wherein: the first contact surface and the second contact surface are designed so as to be operationally controllably movable.

4. The cylindrical grinding machine according to claim 1, wherein: the first contact surface is located on a support plate that is found beneath the workpiece, and the second contact surface is located on a separate support rail that is arranged opposite the grinding disk.

5. The cylindrical grinding machine according to claim 4, wherein: the braking body forms a further support body having a third contact surface.

6. The cylindrical grinding machine according to claim 5, wherein: the third contact surface faces the first contact surface and acts on the workpiece from above.

7. The cylindrical grinding machine according to claim 1, wherein: the first contact surface and the second contact surface are located on a shared support body, which forms a prism that faces the grinding disk and encompasses the workpiece.

8. The cylindrical grinding machine according to claim 7, wherein: the cross-section of the prism has the form of an angle or a trapezoid.

9. The cylindrical grinding machine according to claim 1, wherein the assessment and regulation arrangement is configured to adjust the braking force applied by the braking body based on the rotational speed of the grinding disk and/or the application force applied by the grinding disk.

10. The cylindrical grinding machine according to claim 1, wherein the assessment and regulation arrangement is configured to adjust the braking force of the braking body while the workpiece is being ground by the grinding disk.

11. The cylindrical grinding machine according to claim 1, wherein the grinding disk presses the workpiece directly toward and against each of the first and second contact surfaces in the grinding process responsive to the application force applied by the grinding disk.

12. The cylindrical grinding machine according to claim 1, wherein the application force presses the workpiece directly toward and against each of the first and second contact surfaces.

13. The cylindrical grinding machine according to claim 1, wherein the second contact surface is arranged between the brake body and the first contact surface.

14. The cylindrical grinding machine according to claim 13, further comprising a spring disposed between the brake body and the actuator.

15. A centerless cylindrical grinding machine, comprising: a grinding drive unit and a grinding disk that is mounted therein and is driven to rotate by the drive unit, wherein the grinding disk directly applies an application force on a workpiece, thereby directly and exclusively driving the workpiece to rotate; a support device that is coupled to the workpiece and arranged to obstruct the rotational movement of the workpiece such that the workpiece is driven to rotate and is ground by the grinding disk responsive to the application force, wherein through the grinding drive unit, the grinding disk can be applied in the radial direction thereof against the workpiece having a rotationally symmetrical contour, and the support device comprises at least one first flat contact surface and one second flat contact surface, which are arranged to form a prism with the first and second contact surfaces forming oblique contact surfaces that are both operationally immobile in the circumferential direction of the workpiece, extend at a distance from one another along the workpiece, and encompass the workpiece under sliding contact in such a manner that the workpiece is held at an optimal position for the grinding process and the application force pushes the workpiece against the first and second flat contact surfaces which are stable and consistent; a brake arranged on the support device, the brake having a braking body that acts on the workpiece via an adjustment device with an adjustable braking force, wherein the adjustment device is an actuator controlling the clamping force of the braking body acting on the workpiece; a device for measuring rotational speed configured to constantly monitor the workpiece rotational speed; and an assessment and regulation arrangement configured to constantly maintain an optimal balance between the rotational speed of the grinding disk, the application force applied by the grinding disk, and the braking force applied by the braking body, wherein the actuator is configured to rotate the braking body relative to the workpiece to adjust the braking force applied to the workpiece.

16. A centerless cylindrical grinding machine, comprising: a grinding drive unit and a grinding disk that is mounted therein and is driven to rotate by the drive unit, wherein the grinding disk directly applies an application force on a workpiece, thereby directly and exclusively driving the workpiece to rotate; a support device that is coupled to the workpiece and arranged to obstruct the rotational movement of the workpiece such that the workpiece is driven to rotate and is ground by the grinding disk responsive to the application force, wherein through the grinding drive unit, the grinding disk can be applied in the radial direction thereof against the workpiece having a rotationally symmetrical contour, and the support device comprises at least one first flat contact surface and one second flat contact surface, which are arranged to form a prism with the first and second contact surfaces forming oblique contact surfaces that are both operationally immobile in the circumferential direction of the workpiece, extend at a distance from one another along the workpiece, and encompass the workpiece under sliding contact in such a manner that the workpiece is held at an optimal position for the grinding process and the application force pushes the workpiece against the first and second flat contact surfaces which are stable and consistent; a brake arranged on the support device, the brake having a braking body that acts on the workpiece via an adjustment device with an adjustable braking force, wherein the adjustment device is an actuator controlling the clamping force of the braking body acting on the workpiece; a device for measuring rotational speed configured to constantly monitor the workpiece rotational speed; and an assessment and regulation arrangement configured to constantly maintain an optimal balance between the rotational speed of the grinding disk, the application force applied by the grinding disk, and the braking force applied by the braking body, wherein the braking body is pivotally attached to the support device.

17. A centerless cylindrical grinding machine, comprising: a grinding drive unit and a grinding disk that is mounted therein and is driven to rotate by the drive unit, wherein the grinding disk directly applies an application force on a workpiece, thereby directly and exclusively driving the workpiece to rotate; a support device that is coupled to the workpiece and arranged to obstruct the rotational movement of the workpiece such that the workpiece is driven to rotate and is ground by the grinding disk responsive to the application force, wherein through the grinding drive unit, the grinding disk can be applied in the radial direction thereof against the workpiece having a rotationally symmetrical contour, and the support device comprises at least one first flat contact surface and one second flat contact surface, which are arranged to form a prism with the first and second contact surfaces forming oblique contact surfaces that are both operationally immobile in the circumferential direction of the workpiece, extend at a distance from one another along the workpiece, and encompass the workpiece under sliding contact in such a manner that the workpiece is held at an optimal position for the grinding process and the application force pushes the workpiece against the first and second flat contact surfaces which are stable and consistent; a brake arranged on the support device, the brake having a braking body that acts on the workpiece via an adjustment device with an adjustable braking force, wherein the adjustment device is an actuator controlling the clamping force of the braking body acting on the workpiece; a device for measuring rotational speed configured to constantly monitor the workpiece rotational speed; and an assessment and regulation arrangement configured to constantly maintain an optimal balance between the rotational speed of the grinding disk, the application force applied by the grinding disk, and the braking force applied by the braking body, wherein the support device includes a base comprising the first flat contact surface and the second flat contact surface, and wherein the brake comprising an upper arm pivotably mounted to the base.

18. A centerless cylindrical grinding machine, comprising: a grinding drive unit and a grinding disk that is mounted therein and is driven to rotate by the drive unit, wherein the grinding disk directly applies an application force on a workpiece, thereby directly and exclusively driving the workpiece to rotate; a support device that is coupled to the workpiece and arranged to obstruct the rotational movement of the workpiece such that the workpiece is driven to rotate and is ground by the grinding disk responsive to the application force, wherein through the grinding drive unit, the grinding disk can be applied in the radial direction thereof against the workpiece having a rotationally symmetrical contour, and the support device comprises at least one first flat contact surface and one second flat contact surface, which are arranged to form a prism with the first and second contact surfaces forming oblique contact surfaces that are both operationally immobile in the circumferential direction of the workpiece, extend at a distance from one another along the workpiece, and encompass the workpiece under sliding contact in such a manner that the workpiece is held at an optimal position for the grinding process and the application force pushes the workpiece against the first and second flat contact surfaces, wherein the support device includes a base comprising a first arm including the first flat contact surface and a second arm including the second flat contact surface, and wherein the first arm is substantially perpendicular to the second arm; a brake arranged on the support device and comprising a braking body including an upper arm pivotably mounted to an end of the first arm of the base, the braking body acts on the workpiece via an adjustment device with an adjustable braking force, wherein the adjustment device is an actuator controlling the clamping force of the braking body acting on the workpiece; a device for measuring rotational speed configured to constantly monitor the workpiece rotational speed; and an assessment and regulation arrangement configured to constantly maintain an optimal balance between the rotational speed of the grinding disk, the application force applied by the grinding disk, and the braking force applied by the braking body.

19. The cylindrical grinding machine according to claim 18, wherein the actuator is coupled to the upper arm.

20. The cylindrical grinding machine according to claim 1, wherein the device for measuring rotational speed is configured to directly monitor the workpiece rotational speed.

21. The cylindrical grinding machine according to claim 1, wherein the brake includes an elongate body having a contact surface that is configured to be urged against the workpiece.

22. The cylindrical grinding machine according to claim 21, wherein the elongate body has a rectangular cross section.

23. The cylindrical grinding machine according to claim 22, wherein the contact surface engages the workpiece at a first position and wherein the grinding disk directly applies the application force on the workpiece at a second position, the first position being substantially orthogonal to the second position.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention shall be made more readily apparent through the following embodiments depicted in the accompanying drawings. The drawings illustrate the following:

(2) FIG. 1 is a schematic diagram of the most important component parts in a cylindrical grinding machine for centerless cylindrical grinding with which the method according to the invention is embodied;

(3) FIG. 1a illustrates an assessment and regulation arrangement;

(4) FIG. 2 illustrates an embodiment of the cylindrical grinding machine according to the invention, in which the first and second contact surfaces are combined into a prism;

(5) FIG. 3 addresses a modified embodiment of the prism of FIG. 2; and

(6) FIG. 4 illustrates an embodiment in which a braking device is integrated into a prism.

DETAILED DESCRIPTION

(7) FIG. 1 depicts a section of a cylindrical grinding machine for centerless cylindrical grinding, in cross-section. The cylindrical workpiece 1 has a longitudinal axis 2 and, during operation, comes into contact with the rotating grinding disk 3, the rotational axis thereof lying outside the surface of the drawing. In the selected cross-section according to FIG. 1, the horizontal connecting line 4 runs parallel to the horizontally positioned longitudinal axis 2 of the workpiece and to the rotational axis (not shown) of the grinding disk 3. This results in the contact point 5, at which the grinding disk 3 and the workpiece 1 come into contact with one another at the periphery thereof. It shall be remembered, however, that in certain grinding processes, the rotational axis of the grinding disk 3 can be inclined at a small angle of about 3° to 5° from the horizontal, e.g., in through-feed grinding of cylindrical workpieces 1, which thereby receive their forward thrust in the longitudinal direction. The material of the grinding disk 3 may be corundum or CBN.

(8) Below the grinding disk 3 is a support plate 6, which is formed as a common support ruler. The upwardly facing flat surface thereof is the first contact surface 7 of the support device configured according to the invention. The first contact surface 7 is, as usual, inclined downward at an angle λ, originating from the side thereof facing the grinding disk 3. To adapt to the respective grinding process needing to be addressed, the first contact surface 7 can be adjusted in height. In addition to the setting “below center” depicted in FIG. 1, possible settings include “center” and “over center.” The center is given by the connecting line 4. It is additionally possible to grind at difference angles of inclination λ. For this purpose, the first contact surface 7 is adjusted or the entire support plate 6 is replaced. In most instances, it suffices to perform the altered setting before the cylindrical grinding machine is put into operation; during the grinding, the setting of the first contact surface 7 thus remains operationally unaltered, and it is totally “operationally immobile.” In other cases, the support plate 6 must be adjusted during grinding; for example, this is the case sometimes during plunge grinding if the first contact surface 7 then must be continuously adapted to the decreasing diameter of the workpiece 1. Then, the first contact surface 7 is configured so as to be “operationally controllably movable.”

(9) A support rail 8 on which the second flat contact surface 9 is located is arranged opposite the grinding disk 3 with a certain angular offset. The angular offset corresponds approximately to the angle A. In FIG. 1, the second flat contact surface 9 forms an angle γ with a shared tangent 10 that is placed in the contact point 5 to the workpiece 1 and the grinding disk 3. Other angular positions are also possible. Moreover, the same applies for the support rail 8 and the second contact surface 9 as for the support plate 6 with the first contact surface 7. Both contact surface 7 and 9 can thus be provided so as to be “operationally immobile” or “operationally controllably movable,” wherein it is possible to adjust both contact surfaces together or an individual one—be it the first contact surface 7 or the second contact surface 9, independently of one another. The contact surfaces 7 and 9 may be composed of polycrystalline diamond (PCD) or hard metal; the upper surfaces of the support plate 7 and the support rail 8 are then coated accordingly.

(10) FIG. 1 further illustrates a schematic representation of a brake 11. Herein, a braking body 12 is acted upon with a braking force P by an actuator (not shown) via an intermediate spring system 13. The braking body 12 is located with a third contact surface 14 against the peripheral surface of the workpiece 1. The braking force P is applied via the intermediate spring system 13 in such a manner that during the grinding operation, the workpiece 1 is braked to the correct extent. The grinding disk 3 must, namely, drive the workpiece 1 to rotate on the one hand, but on the other hand also exert a grinding action, by when the rotational speed of the workpiece 1 is lower than the rotational speed of the grinding disk 3. For this purpose, the rotational speed of the workpiece 1 is constantly monitored, for which purpose many possibilities are available, such as sensors 27 or structure-borne sound sensors. According to the measured rotational speed, an assessment and regulation arrangement continually produces the optimum balance between the grinding disk rotational speed, the application force of the grinding disk 3, and the braking force 3, whereby the optimum rotational speed of the workpiece 1 finally is achieved, as shown in FIG. 1a.

(11) During operation of the cylindrical grinding machine depicted in partial cross-section in FIG. 1, the workpiece 1 abuts against the first contact surface 7 and the second contact surface 9. The rotating grinding disk 3, when applied against the workpiece 1, exerts an application force F in the X-direction onto the workpiece 1. At the shared contact point 5 of the workpiece 1 and the grinding disk 3, the grinding disk 3 acts as a “friction drive” and causes the workpiece 1 to rotate in accompaniment. The direction of movement 15 on the surface of the grinding disk 1 and the direction of movement 16 on the surface of the workpiece 1 run concordantly at the contact point 5. The workpiece 1 is thereby pressed against with a certain pressure force on the first contact surface 7 and the second contact surface 9. The workpiece 1 can then still rotate relatively easily on the contact surfaces 7 and 9, but is decelerated somewhat and therefore has a reduced rotational speed. If, in addition, the brake 11 is operated, then the rotational speed of the workpiece 1 is very significantly reduced. At the shared contact point 5 of the workpiece 1 and the grinding disk 3, a significant slippage results in the entrainment of the workpiece 1 by the grinding disk 3. The workpiece 1 is thus entrained in rotation by the grinding disk 3 only to a reduced extent, the result of which is the grinding action that the grinding disk 3 now exerts on the workpiece 1. The correct ratio between the input power and the grinding action is set and maintained by measuring the workpiece rotational speed and the already-mentioned assessment and regulation arrangement. The brake 11 makes it possible to adjust the braking action on the workpiece 1 much more accurately than if the braking were being performed solely through the first contact surface 7 and the second contact surface 9.

(12) In the embodiment according to FIG. 1, the first contact surface 7 and the second contact surface 9 act together similar to a workpiece holder in the form of a prism, which would be familiar to a person skilled in the art. FIGS. 2 to 4 illustrate further embodiments in which the prism is realized in the conventional sense as a structural unit. In FIGS. 2 to 4, the proportions of the grinding disk 3 and the workpiece 1 are changed significantly in comparison to FIG. 1, so that the depiction becomes clearer and also the drawings can be smaller.

(13) As shown in FIG. 2, a grinding spindle unit 17 is provided, which drives the grinding disk 3 to rotate about the rotational axis 18 thereof. The grinding disk 3 contacts the workpiece 1 at the contact point 5. The workpiece 1 is contained by a prism 19, which is formed as a single piece and with the cross-section of an angle. Located on the two arms of the angle are the first contact surface 7 and the second contact surface 9. When the grinding spindle unit 17 is applied in the feed direction X with the application force F in the direction onto the workpiece 1, the result is the rotational driving of the workpiece 1 at the contact point 5 through entrainment, due to the friction. The workpiece 1 is thereby pressed against the first contact surface 7 and the second contact surface 9 of the prism 19, and can only rotate with considerable deceleration in the prism 19. Thus the already-mentioned slippage between the grinding disk 3 and the workpiece 1 at the contact point 5 comes into effect.

(14) FIG. 3 illustrates another form of a prism 20, which here has a trapezoidal cross-section. The workpiece 1 is present only on those two arms of the trapezoid on which the first contact surface 7 and the second contact surface 9 are located. The other units are the same as in FIG. 2. The embodiment comprising the single-piece prism 19 or 20 is simpler than the separated embodiment of the support plate 6 and support rail 8, and thus brings greater stability and accuracy with less effort.

(15) FIG. 4 presents yet another embodiment. Here, the configuration of a prism 21 is present fundamentally corresponding to FIG. 2. However, an upper arm 22 is mounted onto the base 24 of the prism 21 so as to be pivotable about a pivot axis 23. The upper arm 22 can be pressed against the workpiece 1 with an adjustable and controllable action through an actuator 25, which forms part of the brake. The action of the brake 11 has already been described above. The third contact surface 26 is also formed on the upper arm 22.