GB2174323A - Dressing apparatus for grinding machines - Google Patents

Abstract

A cylindrical grinding machine has a cylindrical grinding wheel W which is dressed by a cup-wheel dresser 10 which has a plurality of discrete dressing elements mounted to the dressing face. In one embodiment, the dressing elements include two different types, a pointed diamond tool 18 used for rough dressing and an annular dressing segment 12 for finish dressing. In a second embodiment, the dressing elements are equally spaced and identical, and rough and finish grinding can be effected by rotating the dresser in different modes. <IMAGE>

Description

SPECIFICATION Dresser assemblies for grinding machines The present invention relates to cylindrical grinding machines which effect stock removal from the outer diameter of a cylindrical workpiece rotatively driven about its axis. Stock removal takes place when a rotatively driven grinding wheel is advanced into engagement with the workpiece surface to be ground.

The grinding wheel may be made of silicon grit and the appearance of the abrasive surface will determine its abrasive qualities. An open surface such as would be the case following the dressing of the grinding wheel by a single point diamond dressing tool displaced across the wheel will be very effective to remove stock, but will put a rough finish on the workpiece surface. Where, however, the abrasive surface has not been opened during the dressing operation, as would be the case where dressing is achieved with a conventional cup-wheel dresser which has an annular dressing surface and which rotates continuously during the dressing operation, the wheel will not be as effective as a stock removal tool, but will put a very fine finish on the workpiece surface.

It is accordingly an object of the present invention to provide a dressing tool which can either open the surface of an abrasive wheel to maximize its stock removal capabilities or dress the abrasive wheel without opening the surface so that a very fine surface finish can be achieved.

Other objects and advantages of the present invention will become apparent from the following portion of the specification and from the accompanying drawings which illustrate, in accordance with the mandate of the patent statutes, a presently preferred embodiment incorporating the principles of the invention.

Referring to the drawings: Figure 1 is a side view of a dresser assembly made in accordance with the teachings of the present invention; Figure 2 is a front view of the dresser assembly illustrated in Figure 1; Figure 3 is a side view of the dresser assembly having an alternate embodiment; Figure 4 is a front view of the embodiment of the dresser assembly illustrated in Figure 3; and Figure 5 is an electronic schematic illustrating the control system for the dresser assemblies illustrated in Figures 1, 2 and 3.

The dresser assembly includes a cup-shaped base 10 having an annular surface 11 to which is mounted a segment 12 of a traditional annular dressing element which extends less than 3600 around this surface and may, for example, present diamonds either in cluster or matrix form. While the illustrated dressing segment 12 is continuous, it could be a plurality of spaced segments. Centrally mounted in the circular cutout area between the ends 16 of the dressing segment 12 is a single point diamond dressing tool 18 which is mounted within a bore 19 defined in the cup-shaped base 10. The location of the single point (diamond) dressing tool 18 can be adjusted with an adjustment screw 21 and the adjusted tool can be locked in position by a set screw 22. The dresser assembly will operate to dress the outer periphery 23 of a grinding wheel W.

As shown in Figure 1, the cup-shaped base is mounted on a rotatable shaft 24. The axis of the shaft 24 is parallel to a radius R of the grinding wheel W and is spaced therefrom to locate the lowermost portion of the annular surface 11 tangent to the grinding wheel W at this radius R. The single point dressing tool 18 can accordingly be rotatively displaced in a clockwise direction from a first position adjacent one side of the grinding wheel W (Pos. #1) to a second position (Pos. &num;2) adjacent the other side of the grinding wheel. Rotation is controlled by a Servo Motor (Figure 5) which is coupled to the shaft 24 of the dresser assembly.The dressing segment 12 has an angular extent defined to assure that it will not contact the grinding wheel when the single point dressing tool 18 is rotated clockwise across the grinding wheel from its first position to its second position or counterclockwise from the second position to the first position.

Similarly, the angular extent of the dressing segment 12 is chosen so that rotation of the dresser assembly in the counterclockwise direction to displace the single point dressing tool 18 from the first position to the second position and vice versa will displace the entire surface of this dressing segment 12 past the grinding wheel W.

The electronic schematic illustrated in Figure 5 shows that an Encoder which is driven, directly or indirectly, by the dresser assembly shaft 24, generates position data so that the Dresser Controller will know when the single point dressing tool 18 is at either the first position or the second position. The Dresser Controller will control the Servo Motor Drive to drive the Servo Motor in either the clockwise or counterclockwise direction and can stop the Servo Motor at any selected position.

Assuming that the first operation will be dressing the grinding wheel with the single point dressing tool 18 which is located at the first position, the Dresser Controller will command the Servo Motor Drive to drive the Servo Motor, and hence, the dresser assembly in the clockwise direction at a desired speed. When the Encoder position data indicates thatthe second position has been reached, the Servo Motor Drive can either stop the Servo Motor or command it to drive the dresser assembly in the reverse or countetclockwise direction at a desired speed. In the latter case, the dressing cycle can be performed again or stopped with the single point dressing tool 18 at the first position. The first dressing operation will open the abrasive surface of the grinding wheel to maximize stock removal (rough dressing).

Assuming that the dressing operation ends at the first position, whenever the second dressing operation is desired, the Dresser Controller can command the Servo Motor Drive to rotatively drive the dresser assembly in the counterclockwise direction at a desired speed until the single point dressing tool 18 reaches the second position. The Servo Motor Drive can then either stop the rotation of the dresser assembly or can command the Servo Motor to drive the dresser assembly in the clockwise direction to displace the single point dressing tool 18 back to the first position at a desired speed. This second or finish dressing operation, using the dressing segment 12, will close the abrasive surface of the grinding wheel. Accordingly while the grinding wheel will not be very effective in removing stock from a workpiece, it will put a fine finish on the workpiece.As can be appreciated, a program can be selectively defined for rough and finish dressing since the Dresser Controller is receiving position data and can command the Servo Motor Drive to drive the Servo Motor in either direction at any speed.

The second embodiment of the dresser assembly is illustrated in Figures 3 and 4. In this embodiment, four equally sized and spaced dressing segments 30 are mounted on the annular surface 11 of the dresser assembly. The annular spacing between adjacent segments 30 is chosen so that any one of the dressing segments 30 can be located at the first position (Pos. 1 ) adjacent one side of the grinding wheel W and the next segment in the clockwise direction will be located at the second position (Pos. #2) adjacent the other side of the grinding wheel.

Since the Dresser Controller knows when any one of these segments 30 is located at the first position, the dresser assembly can be stopped with any segment at this position. To perform a rough dressing operation, the dresser assembly can, for example, be rotated 90 at a selected speed in a clockwise direction to draw the dressing segment 30 located at the first position across the grinding wheel W surface at a speed selected to open the grinding wheel surface to rough dress the grinding wheel W.

To then subsequently finish dress this surface, the dresser assembly can, for example, be continuously rotated in either direction at a finish dress speed.

Ideal wear of the dressing segments can be achieved by locating the next successive dressing segment 30 atthe first position at the beginning of the rough dress cycle.

Claims (12)

1. A cylindrical grinding machine comprising a cylindrical grinding wheel mounted for rotation about a predetermined axis, a dresser assembly for dressing the periphery of said cylindrical grinding wheel including: a cup-shaped base member adapted to rotate about a predetermined axis, said cup-shaped base member having an annular surface on which dressing elements can be mounted, annular dressing means mounted on said cupshaped base member annular surface for rotation about said axis, said annular dressing means extending less than 360 around said annular surface, a second dressing tool mounted on said cupshaped base member annular surface at a location centrally located between the ends of said annular dressing means, and means for rotating said cup-shaped base member about said predetermined axis in either a clockwise or counterclockwise direction from a predetermined first position whereat said single point dressing tool is proximate one side of said cylindrical grinding wheel to be dressed to a predetermined second position whereat said single point dressing tool is proximate the other side of said cylindrical grinding wheel to be dressed, means for rotating said dresser assembly between said first and second positions to dress said cylindrical grinding wheel only with said annular dressing means, and means for rotating said dresser assembly between said first and second positions to dress said cylindrical grinding wheel only with said second dressing tool.

2. A cylindrical grinding machine according to claim 1,wherein said annular dressing means is a single continuous segment.

3. A cylindrical grinding machine according to claim 1, wherein said second dressing tool is a single point dressing tool.

4. A cylindrical grinding machine comprising: a cylindrical grinding wheel mounted for rotation about a predetermined axis, a dresser assembly for dressing the periphery of said cylindrical grinding wheel including: a cup-shaped base member adapted to rotate about a predetermined axis, said cup-shaped base member having an annular surface on which dressing elements can be mounted, a plurality of dressing segments mounted on said annular surface in equal spaced relation, said spacing being selected so that adjacent segments can be located on either side of said grinding wheel proximate the surface to be dressed, means for locating one of said plurality of segments at a first position proximate one side of the surface to be dressed at the beginning of a dressing cycle, for rotating the segment located at said first position across the grinding wheel to a second position proximate the other side of the surface to be dressed, for rotating a plurality of said segments past said surface, and for sequentially locating each of said plurality of dressing segments at said first position at the beginning of successive dressing cycles.

5. A cylindrical grinding machine according to claim 4wherein there are four segments.

6. A dresser assembly for use in dressing a cylindrical grinding wheel, comprising cup shaped base member rotatable about an axis and having an annular surface a plurality of dressing elements circumferentially spaced about the said annular surface the base member being rotatable about its axis in use of the assembly so as to draw a selected one of the dressing elements across the grinding wheel to dress the cylindrical surface thereof.

7. An assembly according to claim 6, wherein one dressing element is constituted by a single point dressing tool.

8. An assembly according to claim 7, comprising as a second dressing element an arcuate dressing element whose opposite ends are circumferentially spaced from the single point dressing tool sufficiently to permit the said tool to traverse the grinding wheel without the ends of the arcuate element contacting the wheel.

9. An assembly according to claim 8, wherein the arcuate dressing element is itself composed of a plurality of discrete segments.

10. An assembly according to claim 6, wherein each of the dressing elements comprises a discrete segment, each of which can be drawn across the grinding wheel without the other segments contacting the wheel.

11. An assembly according to claim 10, wherein there is a total of four said segments.

12. A dresser assembly for use in dressing a cylindrical grinding wheel, substantially as herein described with reference to the accompanying drawings.