CA1217056A - Automatic dual compensation grinding wheel conditioner - Google Patents
Automatic dual compensation grinding wheel conditionerInfo
- Publication number
- CA1217056A CA1217056A CA000436709A CA436709A CA1217056A CA 1217056 A CA1217056 A CA 1217056A CA 000436709 A CA000436709 A CA 000436709A CA 436709 A CA436709 A CA 436709A CA 1217056 A CA1217056 A CA 1217056A
- Authority
- CA
- Canada
- Prior art keywords
- wheel
- grinding
- super
- abrasive
- wear
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B24—GRINDING; POLISHING
- B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
- B24B49/00—Measuring or gauging equipment for controlling the feed movement of the grinding tool or work; Arrangements of indicating or measuring equipment, e.g. for indicating the start of the grinding operation
- B24B49/18—Measuring or gauging equipment for controlling the feed movement of the grinding tool or work; Arrangements of indicating or measuring equipment, e.g. for indicating the start of the grinding operation taking regard of the presence of dressing tools
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Grinding-Machine Dressing And Accessory Apparatuses (AREA)
- Finish Polishing, Edge Sharpening, And Grinding By Specific Grinding Devices (AREA)
- Grinding Of Cylindrical And Plane Surfaces (AREA)
- Grinding And Polishing Of Tertiary Curved Surfaces And Surfaces With Complex Shapes (AREA)
- Polishing Bodies And Polishing Tools (AREA)
Abstract
AUTOMATIC DUAL COMPENSATION
GRINDING WHEEL CONDITIONER
Abstract of the Disclosure An improved method to surface condition a super-abrasive grinding wheel by intermittently moving the wheel to a stationary wheel conditioner unit mounted adjacent the grinding wheel with the conditioner unit having a consumable element engaged by the grinding wheel to condition the grinding wheel including a dual compensation method having the steps of grinding a predetermined number of workpieces to establish a first predetermined depth of super-abrasive wheel wear; periodically conditioning the wheel surface by consuming a second predetermined depth from a consumable reconditioning tool surface; and producing a first compensation of a grinding wheel by controlling the position of the super-abrasive wheel with respect to the workpiece to maintain an apparent wheel wear depth within the range of desired workpiece tolerance and producing a second compensation of a grinding wheel conditioner by contacting the wear surface of the super-abrasive wheel with the reconditioning tool surface and advancing it into and away from the tool surface a distance equal to the second predetermined depth each time that the wheel is reconditioned so as to assure that individual grains of the super-abrasive constituent of the wheel will extend beyond the bonding material constituent of the wheel to maintain cutting efficiency of the wheel following the reconditioning step.
GRINDING WHEEL CONDITIONER
Abstract of the Disclosure An improved method to surface condition a super-abrasive grinding wheel by intermittently moving the wheel to a stationary wheel conditioner unit mounted adjacent the grinding wheel with the conditioner unit having a consumable element engaged by the grinding wheel to condition the grinding wheel including a dual compensation method having the steps of grinding a predetermined number of workpieces to establish a first predetermined depth of super-abrasive wheel wear; periodically conditioning the wheel surface by consuming a second predetermined depth from a consumable reconditioning tool surface; and producing a first compensation of a grinding wheel by controlling the position of the super-abrasive wheel with respect to the workpiece to maintain an apparent wheel wear depth within the range of desired workpiece tolerance and producing a second compensation of a grinding wheel conditioner by contacting the wear surface of the super-abrasive wheel with the reconditioning tool surface and advancing it into and away from the tool surface a distance equal to the second predetermined depth each time that the wheel is reconditioned so as to assure that individual grains of the super-abrasive constituent of the wheel will extend beyond the bonding material constituent of the wheel to maintain cutting efficiency of the wheel following the reconditioning step.
Description
12~L7~5~
AUTOMATIC DUAL COMPENSATION
GRINDING WHEEL CONDITIONER
Technical Field This invention relates generally to the grinding machine art and, more specifically, to an improved method to surface condition a cubic boron nitride grinding wheel by intermittently moving the wheel to a stationary wheel conditioner unit mounted adjacent the grinding wheel with the conditioner unit having a consumable element engaged by the grinding wheel to condition the grinding wheel.
~ack~round Art It is well known in the grinding machine art to dress the outside periphery of a consumable abrasive grinding wheeL by several methods or forms; such as, a single point diamond, a multipoint diamond, rotary diamond, or diamond roll. The type of work being performed prescribes the dressing method which will provide optimum performance.
Most automatic grinding machinery is based on the use of a relatively consumable grinding wheel, such as aluminum oxide or silicon carbide, which is periodically conditioned (trued or dressed) by a relatively non-consumable tool, such as a single-point diamond or a fixed cluster of multiple diamond points or a rotating diamond wheel (called a roll or a cutter). Since the relatively consumable wheel generally loses the ability to grind properly before it loses a significant amount of dimensional accuracy, it is generally reconditioned (dressed) before the dimensional accuracy of the workpieces is affected. Since the distance between the surface of a finished workpiece and the cutting surface of the wheel conditioning tool remains fixed, all that is required of the automatic machine is the periodic decrease of the distance between the wheel and the dresser/workpiece combination. This decrement is called "compensation" or "dress compensation". Depending on the construction of V~
machinet either the wheel is compensated, or the work support carries the dresser and the work support is compensated. In either case, the compensation usually takes place just prior to the wheel being passed by the dressing tool, and the dressiny tool removes this amount from the wheel, leaving the relative positions of the critical surfaces of the wheel and the workpiece and the dresser essentially just as they were before compensa-tion took place.
Modern super-abrasives, such as diamond and cubic boron nitride, are more difficult to incorporate in-to a fully automatlc process. The problem is caused by the very property of these abrasives which makes them so attractive:
their extreme resistance to wear. Wheels made of these materials wear extremely slowly and in most cases very evenly. In some applications using cubic boron nitride, the need for reconditioning of the wheel sur,ace is demonstrated by an increase in the roughness of the finished workpiece surace. In those cases the proper remedy is to compensate a small amount, say .0001", and then pass the wheel by a rotating diamond cutter. This still constitutes the use of a somewhat consumable wheel and a relatively non-consumable wheeL conditioning tool as described above. Initial truing of a cubic boron nitride wheel to remove eccentricity after mounting also falls in this category. However, in many applications the need for reconditioning of the wheel surface is demonstrated by a reduction ln the ease with which the wheel cuts, an increase in force and temperatureO
The cause of these effects is the loss of "stick-out" of the individual diamond or cubic boron nitride abrasive grains beyond the material which bonds them together. The remedy is to wear or erode some of the bond material away without siynificantly wearing or pulling out the diamond or cubic boron nitride particles. This is accomplished by having the wheel do some grinding on some relatively soft aluminum oxide or silicon carbide, elther in the form of a stationary stick or a rotating wheel. The latter is either motorized 7CI ~
or equipped with a braking device which limits the rotational speed which the soft wheel can achieve as a result of the driving action of the super-abrasive wheel.
; According to the present invention there is provided a method of conditioning a known super-abrasive grinding i wheel mounted on a known drive spindle by use of a known dressing tool, the method including the steps of providing the super-abrasive wheel with super-abrasive grinding constituents embedded in bonding material so as to extend beyond the bonding material 10 a predetermined extent and fine tuning the wheel by adjusting the position of the wheel in addition to normal feed movements between the wheel and the workpiece during a select number of workpiece grinding steps to compensate for incremental wear of the wheel to maintain apparent wheel wear within the ~ tolerance range of the workpiece being ground~ Such fine : tuning is terminated at a predetermined depth of wheel wear produced by such wheel grinding steps, and thereafter, the wheel is relatively positioned while on its drive spindle I with respect to a consumable reconditioning tool to cause the tool to be consumed by the wheel to a depth an order of '! magnitude greater than the predetermined depth of wheel wear / so as to remove the bonding material so that individual grains '`1 f super-abrasive constituents of the wheel will re-extend ; ~eyond the bonding material consituent of the wheel to re-establish cutting efficiency of the wheel following the select . j .
number of grinding wheel steps.
In a specific embodiment of the present invention there is provided a dual compensation method for conditioning a super-abrasive grinding wheel including the steps of grinding ~' a predetermined number of workpieces to establish a first predetermined depth of super-abrasive wheel wear; periodically conditioning the wheel surface by consuming a second predetermined depth from a consumable reconditioning tool surface; and pro-ducing a first compensation of a grinding wheel by controlling the position of the super-abrasive wheel with respect to the workpiece to maintain an apparent wheel wear depth within mab/~JJ
l7~5~
the range of desired workpiece tolerance and producing a second compensation of a grinding wheel condltioner by contacting the wear surface of the super-abrasive wheel with the re-conditioning tool surface and advancing it into and away from the tool surface a distance equal to the second predetermined depth each time that the wheel is reconditioned.
Also in a specific embodiment of the present invention there is provided an improved dual compensation method for conditioning the wear surface of a super-abrasive grinding wheel comprising the steps of locating a workpiece support and a reconditioner tool support at fixed locations ~ and locating a super-abrasive grinding wheel on a movable ;~ platform; driving the platform by drive means under the control of a programmable controller; programming the controller to 'i move the wheel into engagement with a consumable reconditioning tool surface on the tool support only following a predetermined number of grinding sequences wherein the wheel grinds a pre-determined number of workpieces ~n the fixed workpiece support , 20 so as to produce a corresponding first predetermined depth of wear of the grinding surface on the wheel; programming the controllerto produce a first compensation of the super-abrasive wheel by advancing the wheel with respect to the predetermined number of workpieces in addition to normal grinding wheel feed movement and in accordance with a predetermined schedule to maintain the apparent wear of the wear surface ' of the grinding wheel within desired workpiece tolerance ranges;and further programming the controller to produce a second compensation of the super-abrasive wheels during each re-conditioning step by advancing and retracting the wheel into the surface of the consumable reconditioning tool a pre-determined depth an order of magnitude greater than the first predetermined depth of wear.
-mab. ~1 A
::~2~
Brief Description of the Drawing The drawing shows a perspective view disclosing , a grinding wheel, the workpiece support and consumable re-j conditioning tool suitable for practicing the method of the present invention.
Best Mode of Carrying Out the Invention Referring now to the drawing, the numeral 10 generally designates a one-station electro-mechanical internal grinding machine with one grinding wheel spindle on a cross slide driven by CNC controlled drive motors embodying the ; principles disclosed in U.S. Patent 4,419,612, issued December 6, 1983. As stated in the aforesaid '286 application, any suitable programmable controller may be employed, such as ' a Bryant Series 75 programmable controller available from - the Westinghouse Electric Corporation of Gateway Center, Pittsburgh, Pennsylvania 15222. A suitable feed control is one available on the market from Intel Corporation of Santa Clara, California 95054, and which is sold under the name ~ of "INTEL" (a trademark), 80/05 Single Board Computer. The i,3 drive means may be any suitable servo drive means as, for example, a servo drive of Hyper Loop, Inc., of 7459 W. 79 Street, Bridgeview, Illinois 60455, under the trademark "HYAMP".
`! The "HYAMP" servo drive is a single-phase, four wave, bi-directional SCR controlled servo drive for D.C. motors, and it provides D.C. drive power for precise speed control and regulation over a wide speed :
1 .
A mab/~l~
~17~
- -- 7 ~
range. Another suitable servo-drive, designated as Size 50, is available from General Electric Company, 685 West Rio Road, Charlottsville, Virginia 22906.
The drive motor for each axis is a D.C. servo motor.
Suitable ~.C. servo motors of this type are available from Torque Systems Incorporated, 225 Crescent Street, Waltham, Massachusetts 02154, under~~e ~rademark "S~APPER", and identified as frame sizes 3435 and 5115. A large motor of this type is also available from the ~. R. Porter Co., of 301 Porter Street, Pittsburgh, Pennsylvania 15219.
. ~
Tachometers are part o the D.C. servo motors.
Resolvers, encoders or " INDUCTOSY~" transducers are used in the feedback system and they may be any suitable conventional position feedback devices available on the market. Resolvers of this type are available from the Clifton Precision Company of Clifton Heights, Pennsylvania `
19018. "I~DUCTOSYN" precision linear and rotary position transducers are available from Farrand Controls, a division o~ Farrand Industries, Inc , of 99 Wall Street, Valhalla, New York 10595~ A suitable optical shaft angle encoder, designated by Model No. DRC-3S is available from Dynamics Research Corporation o 60 Concord Street, Wilmington, Maryland 01887.
The grinding machine 10 includes a conventional bed or bridge member 12 on which is operatively mounted a con~entional fixed workhead 13. The workhead 13 may be Oc any suitable conventional structure and it comprises a chucking fixture lS for holding a workpiece~ The chucking fi~ture is adapted to be rotated by a motor and an operatively connected pulley means disclosed in the above-mentioned co-pend ng apolication.
As shown in the drawing, â bore grinding wneel 17 is operatively carried on tne compound slide assembly 19, on the right end of the mzchine 10, which comprises the A
7~5 longitudi~al and cross slides disclosed in the above-noted co-pending application. It will be understood that the control system of the present invention is capable of controlling any combination of motions of a grinding wheel on the compound slide assembly. The grinding wheel 17 is a super-abrasive wheel having particles of diamond or cubic boron nitride defining a super-abrasive constituent of the wheel and a suitable bonding constituent holds the particles so that end segments on each particle stic~ out from the bonding material to define the workpiece cutting surrace on ~he wheel.
A consumable grinding wheel conditioner unit 20 is mounted on the workhead bridge 12 on a base extension member 21 which extends or cantilevers over the center of the machine grinding area. Th~ unit 20 has a base 31 secured by means o~ bolts 23 slidable in T-slots 25 of the base extension member 21. A slide base unit 35 is adjustably fixed for transverse movement on base 31. The unit 35 has a transverse portion 43 extending upwardly to form a side support wall for the dressing unit 45. A consumable reconditioning tool 47 is on unit 45.
In operation, the grinding wheel 17 is rotated to grind the bore or face of a wor~piece or any combination thereof.
The longitudinal slide provides the grinding wheel 17 with a sequence of movements such as rapid forward traverse, slo~
infeed, high speed reciprocation and bac~-off retraction.
The cross slide provides the grinding wheel 17 with positioning movements and compensation movements to compensate for the wearing away of the grinding wheel in tne grinding of each part. The control system of the present invention is disclosed in co-pending aforementioned patent application and need not be discussed in detail herein.
During conditioning, the grinding wheel 17 is carried on the compound slide over to the conditioning unit 20 ~here it is conditioned or dressed by a soft condi~ioning element ~7~3S~
or reconditioning tool 47 made of materials such as aluminum oxide or silicon carbide. Such materials are characterized as being softer than the super-abrasive particles of wheel 17 and of a hardness to abrade away the bonding constituent of wheel 17.
Following extended grinding se~uences made possible by the improved wearability of the super-a~rasive particles of wheel 17 a condition can occur where the exposed ends of the particles no longer "stick out" or extend from the surface of the wheel 17. The remedy is to wear or erode some of the wheel bond material away from the wheel so as to expose super-abrasive particles without signi~icantly wearing or pulling out the super-abrasive particles.
In accordance with the invention, a soft conditioning stick or wheel is used as a reconditioning tool in a dual compensation wheel conditioner method to maintain grinding machine efficiency. The stationary unit of the conditioner is rigidly clamped and formed with relatively stiff plate segments that define a stable accurately positioned platfor~
for the reconditioning tool which has a reduced spring rate.
The reconditioning tool 47 is positioned to provide for a more accurate and stable method of dressing the grinding wheel which not only is simple and more relia~le, but enhances reconditioning of the super-abrasive wheel 17.
One e~ample of the method assumes the following criteria. The wheel 17 is reconditioned after 100 workpieces are ground. The wheel wears .001 inches during that interval. The workpiece tolerance is such that wheel wear should be kept down to .0001 inches or less. The reconditioning tool wear is .025 inches each time the wheel is fully reconditioned (an order of magnitude greater than the wheel sur~ace wear). The workpiece support and the reconditioner tool suppor~ have fixed locations and the wheel is moved by a CNC controller.
q The first of the "dual" compensations is used to keep the apparent wheel wear down to .0001 inches or less. The CNC is therefore programmed to advance the wheel toward the work by .0001 inches after grinding 10 workpieces, or .00001 inches after every workpiece, or any suitable combination in between these two. This advance is in addition to the normal feed movements~
The second of the "dual" compensations is used to assure two things: that the wheel contacts the reconditioning tool properly and advances .,025" into it in the right manner each time, and that the wheel backs away from the reconditioning tool an additional .025" each successive time so as to be in the proper position for being brought into contact with the workpiece. The CNC controller is therefore programmed to advance the wheel toward the reconditioning tool after grinding 100 workpieces, either to the position it h~d when it was last advanced into it or to .025" beyond the position it had when it was last advanced up to it (both being the same), then to advance into the reconditioning tool .025" at a specified rate, then an optional time to dwell, then to retract to the proper position for being brought into contact with the workpiece.
AUTOMATIC DUAL COMPENSATION
GRINDING WHEEL CONDITIONER
Technical Field This invention relates generally to the grinding machine art and, more specifically, to an improved method to surface condition a cubic boron nitride grinding wheel by intermittently moving the wheel to a stationary wheel conditioner unit mounted adjacent the grinding wheel with the conditioner unit having a consumable element engaged by the grinding wheel to condition the grinding wheel.
~ack~round Art It is well known in the grinding machine art to dress the outside periphery of a consumable abrasive grinding wheeL by several methods or forms; such as, a single point diamond, a multipoint diamond, rotary diamond, or diamond roll. The type of work being performed prescribes the dressing method which will provide optimum performance.
Most automatic grinding machinery is based on the use of a relatively consumable grinding wheel, such as aluminum oxide or silicon carbide, which is periodically conditioned (trued or dressed) by a relatively non-consumable tool, such as a single-point diamond or a fixed cluster of multiple diamond points or a rotating diamond wheel (called a roll or a cutter). Since the relatively consumable wheel generally loses the ability to grind properly before it loses a significant amount of dimensional accuracy, it is generally reconditioned (dressed) before the dimensional accuracy of the workpieces is affected. Since the distance between the surface of a finished workpiece and the cutting surface of the wheel conditioning tool remains fixed, all that is required of the automatic machine is the periodic decrease of the distance between the wheel and the dresser/workpiece combination. This decrement is called "compensation" or "dress compensation". Depending on the construction of V~
machinet either the wheel is compensated, or the work support carries the dresser and the work support is compensated. In either case, the compensation usually takes place just prior to the wheel being passed by the dressing tool, and the dressiny tool removes this amount from the wheel, leaving the relative positions of the critical surfaces of the wheel and the workpiece and the dresser essentially just as they were before compensa-tion took place.
Modern super-abrasives, such as diamond and cubic boron nitride, are more difficult to incorporate in-to a fully automatlc process. The problem is caused by the very property of these abrasives which makes them so attractive:
their extreme resistance to wear. Wheels made of these materials wear extremely slowly and in most cases very evenly. In some applications using cubic boron nitride, the need for reconditioning of the wheel sur,ace is demonstrated by an increase in the roughness of the finished workpiece surace. In those cases the proper remedy is to compensate a small amount, say .0001", and then pass the wheel by a rotating diamond cutter. This still constitutes the use of a somewhat consumable wheel and a relatively non-consumable wheeL conditioning tool as described above. Initial truing of a cubic boron nitride wheel to remove eccentricity after mounting also falls in this category. However, in many applications the need for reconditioning of the wheel surface is demonstrated by a reduction ln the ease with which the wheel cuts, an increase in force and temperatureO
The cause of these effects is the loss of "stick-out" of the individual diamond or cubic boron nitride abrasive grains beyond the material which bonds them together. The remedy is to wear or erode some of the bond material away without siynificantly wearing or pulling out the diamond or cubic boron nitride particles. This is accomplished by having the wheel do some grinding on some relatively soft aluminum oxide or silicon carbide, elther in the form of a stationary stick or a rotating wheel. The latter is either motorized 7CI ~
or equipped with a braking device which limits the rotational speed which the soft wheel can achieve as a result of the driving action of the super-abrasive wheel.
; According to the present invention there is provided a method of conditioning a known super-abrasive grinding i wheel mounted on a known drive spindle by use of a known dressing tool, the method including the steps of providing the super-abrasive wheel with super-abrasive grinding constituents embedded in bonding material so as to extend beyond the bonding material 10 a predetermined extent and fine tuning the wheel by adjusting the position of the wheel in addition to normal feed movements between the wheel and the workpiece during a select number of workpiece grinding steps to compensate for incremental wear of the wheel to maintain apparent wheel wear within the ~ tolerance range of the workpiece being ground~ Such fine : tuning is terminated at a predetermined depth of wheel wear produced by such wheel grinding steps, and thereafter, the wheel is relatively positioned while on its drive spindle I with respect to a consumable reconditioning tool to cause the tool to be consumed by the wheel to a depth an order of '! magnitude greater than the predetermined depth of wheel wear / so as to remove the bonding material so that individual grains '`1 f super-abrasive constituents of the wheel will re-extend ; ~eyond the bonding material consituent of the wheel to re-establish cutting efficiency of the wheel following the select . j .
number of grinding wheel steps.
In a specific embodiment of the present invention there is provided a dual compensation method for conditioning a super-abrasive grinding wheel including the steps of grinding ~' a predetermined number of workpieces to establish a first predetermined depth of super-abrasive wheel wear; periodically conditioning the wheel surface by consuming a second predetermined depth from a consumable reconditioning tool surface; and pro-ducing a first compensation of a grinding wheel by controlling the position of the super-abrasive wheel with respect to the workpiece to maintain an apparent wheel wear depth within mab/~JJ
l7~5~
the range of desired workpiece tolerance and producing a second compensation of a grinding wheel condltioner by contacting the wear surface of the super-abrasive wheel with the re-conditioning tool surface and advancing it into and away from the tool surface a distance equal to the second predetermined depth each time that the wheel is reconditioned.
Also in a specific embodiment of the present invention there is provided an improved dual compensation method for conditioning the wear surface of a super-abrasive grinding wheel comprising the steps of locating a workpiece support and a reconditioner tool support at fixed locations ~ and locating a super-abrasive grinding wheel on a movable ;~ platform; driving the platform by drive means under the control of a programmable controller; programming the controller to 'i move the wheel into engagement with a consumable reconditioning tool surface on the tool support only following a predetermined number of grinding sequences wherein the wheel grinds a pre-determined number of workpieces ~n the fixed workpiece support , 20 so as to produce a corresponding first predetermined depth of wear of the grinding surface on the wheel; programming the controllerto produce a first compensation of the super-abrasive wheel by advancing the wheel with respect to the predetermined number of workpieces in addition to normal grinding wheel feed movement and in accordance with a predetermined schedule to maintain the apparent wear of the wear surface ' of the grinding wheel within desired workpiece tolerance ranges;and further programming the controller to produce a second compensation of the super-abrasive wheels during each re-conditioning step by advancing and retracting the wheel into the surface of the consumable reconditioning tool a pre-determined depth an order of magnitude greater than the first predetermined depth of wear.
-mab. ~1 A
::~2~
Brief Description of the Drawing The drawing shows a perspective view disclosing , a grinding wheel, the workpiece support and consumable re-j conditioning tool suitable for practicing the method of the present invention.
Best Mode of Carrying Out the Invention Referring now to the drawing, the numeral 10 generally designates a one-station electro-mechanical internal grinding machine with one grinding wheel spindle on a cross slide driven by CNC controlled drive motors embodying the ; principles disclosed in U.S. Patent 4,419,612, issued December 6, 1983. As stated in the aforesaid '286 application, any suitable programmable controller may be employed, such as ' a Bryant Series 75 programmable controller available from - the Westinghouse Electric Corporation of Gateway Center, Pittsburgh, Pennsylvania 15222. A suitable feed control is one available on the market from Intel Corporation of Santa Clara, California 95054, and which is sold under the name ~ of "INTEL" (a trademark), 80/05 Single Board Computer. The i,3 drive means may be any suitable servo drive means as, for example, a servo drive of Hyper Loop, Inc., of 7459 W. 79 Street, Bridgeview, Illinois 60455, under the trademark "HYAMP".
`! The "HYAMP" servo drive is a single-phase, four wave, bi-directional SCR controlled servo drive for D.C. motors, and it provides D.C. drive power for precise speed control and regulation over a wide speed :
1 .
A mab/~l~
~17~
- -- 7 ~
range. Another suitable servo-drive, designated as Size 50, is available from General Electric Company, 685 West Rio Road, Charlottsville, Virginia 22906.
The drive motor for each axis is a D.C. servo motor.
Suitable ~.C. servo motors of this type are available from Torque Systems Incorporated, 225 Crescent Street, Waltham, Massachusetts 02154, under~~e ~rademark "S~APPER", and identified as frame sizes 3435 and 5115. A large motor of this type is also available from the ~. R. Porter Co., of 301 Porter Street, Pittsburgh, Pennsylvania 15219.
. ~
Tachometers are part o the D.C. servo motors.
Resolvers, encoders or " INDUCTOSY~" transducers are used in the feedback system and they may be any suitable conventional position feedback devices available on the market. Resolvers of this type are available from the Clifton Precision Company of Clifton Heights, Pennsylvania `
19018. "I~DUCTOSYN" precision linear and rotary position transducers are available from Farrand Controls, a division o~ Farrand Industries, Inc , of 99 Wall Street, Valhalla, New York 10595~ A suitable optical shaft angle encoder, designated by Model No. DRC-3S is available from Dynamics Research Corporation o 60 Concord Street, Wilmington, Maryland 01887.
The grinding machine 10 includes a conventional bed or bridge member 12 on which is operatively mounted a con~entional fixed workhead 13. The workhead 13 may be Oc any suitable conventional structure and it comprises a chucking fixture lS for holding a workpiece~ The chucking fi~ture is adapted to be rotated by a motor and an operatively connected pulley means disclosed in the above-mentioned co-pend ng apolication.
As shown in the drawing, â bore grinding wneel 17 is operatively carried on tne compound slide assembly 19, on the right end of the mzchine 10, which comprises the A
7~5 longitudi~al and cross slides disclosed in the above-noted co-pending application. It will be understood that the control system of the present invention is capable of controlling any combination of motions of a grinding wheel on the compound slide assembly. The grinding wheel 17 is a super-abrasive wheel having particles of diamond or cubic boron nitride defining a super-abrasive constituent of the wheel and a suitable bonding constituent holds the particles so that end segments on each particle stic~ out from the bonding material to define the workpiece cutting surrace on ~he wheel.
A consumable grinding wheel conditioner unit 20 is mounted on the workhead bridge 12 on a base extension member 21 which extends or cantilevers over the center of the machine grinding area. Th~ unit 20 has a base 31 secured by means o~ bolts 23 slidable in T-slots 25 of the base extension member 21. A slide base unit 35 is adjustably fixed for transverse movement on base 31. The unit 35 has a transverse portion 43 extending upwardly to form a side support wall for the dressing unit 45. A consumable reconditioning tool 47 is on unit 45.
In operation, the grinding wheel 17 is rotated to grind the bore or face of a wor~piece or any combination thereof.
The longitudinal slide provides the grinding wheel 17 with a sequence of movements such as rapid forward traverse, slo~
infeed, high speed reciprocation and bac~-off retraction.
The cross slide provides the grinding wheel 17 with positioning movements and compensation movements to compensate for the wearing away of the grinding wheel in tne grinding of each part. The control system of the present invention is disclosed in co-pending aforementioned patent application and need not be discussed in detail herein.
During conditioning, the grinding wheel 17 is carried on the compound slide over to the conditioning unit 20 ~here it is conditioned or dressed by a soft condi~ioning element ~7~3S~
or reconditioning tool 47 made of materials such as aluminum oxide or silicon carbide. Such materials are characterized as being softer than the super-abrasive particles of wheel 17 and of a hardness to abrade away the bonding constituent of wheel 17.
Following extended grinding se~uences made possible by the improved wearability of the super-a~rasive particles of wheel 17 a condition can occur where the exposed ends of the particles no longer "stick out" or extend from the surface of the wheel 17. The remedy is to wear or erode some of the wheel bond material away from the wheel so as to expose super-abrasive particles without signi~icantly wearing or pulling out the super-abrasive particles.
In accordance with the invention, a soft conditioning stick or wheel is used as a reconditioning tool in a dual compensation wheel conditioner method to maintain grinding machine efficiency. The stationary unit of the conditioner is rigidly clamped and formed with relatively stiff plate segments that define a stable accurately positioned platfor~
for the reconditioning tool which has a reduced spring rate.
The reconditioning tool 47 is positioned to provide for a more accurate and stable method of dressing the grinding wheel which not only is simple and more relia~le, but enhances reconditioning of the super-abrasive wheel 17.
One e~ample of the method assumes the following criteria. The wheel 17 is reconditioned after 100 workpieces are ground. The wheel wears .001 inches during that interval. The workpiece tolerance is such that wheel wear should be kept down to .0001 inches or less. The reconditioning tool wear is .025 inches each time the wheel is fully reconditioned (an order of magnitude greater than the wheel sur~ace wear). The workpiece support and the reconditioner tool suppor~ have fixed locations and the wheel is moved by a CNC controller.
q The first of the "dual" compensations is used to keep the apparent wheel wear down to .0001 inches or less. The CNC is therefore programmed to advance the wheel toward the work by .0001 inches after grinding 10 workpieces, or .00001 inches after every workpiece, or any suitable combination in between these two. This advance is in addition to the normal feed movements~
The second of the "dual" compensations is used to assure two things: that the wheel contacts the reconditioning tool properly and advances .,025" into it in the right manner each time, and that the wheel backs away from the reconditioning tool an additional .025" each successive time so as to be in the proper position for being brought into contact with the workpiece. The CNC controller is therefore programmed to advance the wheel toward the reconditioning tool after grinding 100 workpieces, either to the position it h~d when it was last advanced into it or to .025" beyond the position it had when it was last advanced up to it (both being the same), then to advance into the reconditioning tool .025" at a specified rate, then an optional time to dwell, then to retract to the proper position for being brought into contact with the workpiece.
Claims (3)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method for conditioning a known super-abrasive grinding wheel mounted on a known drive spindle by use of a known dressing tool characterized by the steps of:
providing the super-abrasive wheel with super-abrasive grinding constituents embedded in bonding material so as to extend beyond the bonding material a predetermined extent; fine tuning the wheel by adjusting the position of the wheel in addition to normal feed movements between the wheel and the workpiece during a select number of workpiece grinding steps to compensate for incremental wear of the wheel to maintain apparent wheel wear within the tolerance range of the workpiece being ground;
terminating such fine tuning at a predetermined depth of wheel wear produced by such wheel grinding steps; and thereafter relatively positioning the wheel while on its drive spindle with respect to a consumable reconditioning tool to cause the tool to be consumed by the wheel to a depth an order of magnitude greater than the predetermined depth of wheel wear so as to remove said bonding material so that individual grains of the super-abrasive constituent of the wheel will re-extend beyond the bonding material constituents of the wheel to re-establish cutting efficiency of the wheel following the select number of grinding wheel steps.
providing the super-abrasive wheel with super-abrasive grinding constituents embedded in bonding material so as to extend beyond the bonding material a predetermined extent; fine tuning the wheel by adjusting the position of the wheel in addition to normal feed movements between the wheel and the workpiece during a select number of workpiece grinding steps to compensate for incremental wear of the wheel to maintain apparent wheel wear within the tolerance range of the workpiece being ground;
terminating such fine tuning at a predetermined depth of wheel wear produced by such wheel grinding steps; and thereafter relatively positioning the wheel while on its drive spindle with respect to a consumable reconditioning tool to cause the tool to be consumed by the wheel to a depth an order of magnitude greater than the predetermined depth of wheel wear so as to remove said bonding material so that individual grains of the super-abrasive constituent of the wheel will re-extend beyond the bonding material constituents of the wheel to re-establish cutting efficiency of the wheel following the select number of grinding wheel steps.
2. In the combination of claim 1, the select number of workpiece grinding steps including grinding a pre-determined number of workpieces to establish a first predetermined depth of super-abrasive wheel wear; and producing the compensation of a grinding wheel conditioner by contacting the wear surface of the super-abrasive wheel with the reconditioning tool surface while the wheel remains on the drive spindle and advancing it into and away from the tool surface a distance equal to a second predetermined depth which is an order of magnitude greater than the first predetermined depth each time that the wheel is reconditioned.
3. In the combination of claim 1, the further steps of providing a movable platform for the spindle, a workpiece support and a reconditioner tool support at fixed locations on a machine base and locating the super-abrasive grinding wheel and drive spindle on the movable platform; driving the platform by drive means under the control of a programmable controller; programming the controller to move the wheel while on the drive spindle into engagement with a consumable reconditioning tool surface on the tool support only following a predetermined number of grinding sequences in which the wheel grinds a pre-determined number of workpieces on the fixed workpiece support so as to produce a corresponding first predetermined depth of wear of the grinding surface on the wheel; programming the controller to produce a first fine tuning compensation of the super-abrasive wheel by advancing the wheel with respect to the predetermined number of workpieces in addition to normal grinding wheel feed movement and in accordance with a predetermined schedule to maintain the apparent wear of the wear surface of the grinding wheel within desired workpiece tolerance ranges;
and further programming the controller to produce compensation of the super-abrasive wheel during each reconditioning step by advancing and retracting the wheel into the surface of the consumable reconditioning tool a second predetermined depth which is an order of magnitude greater than the first predetermined depth of wear so as to re-establish grinding wheel, efficiency following the fine tuning compensation.
mab/
and further programming the controller to produce compensation of the super-abrasive wheel during each reconditioning step by advancing and retracting the wheel into the surface of the consumable reconditioning tool a second predetermined depth which is an order of magnitude greater than the first predetermined depth of wear so as to re-establish grinding wheel, efficiency following the fine tuning compensation.
mab/
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US41810382A | 1982-09-14 | 1982-09-14 | |
| US418,103 | 1982-09-14 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1217056A true CA1217056A (en) | 1987-01-27 |
Family
ID=23656723
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000436709A Expired CA1217056A (en) | 1982-09-14 | 1983-09-14 | Automatic dual compensation grinding wheel conditioner |
Country Status (12)
| Country | Link |
|---|---|
| JP (1) | JPS59134660A (en) |
| AU (1) | AU1876483A (en) |
| BE (1) | BE897754A (en) |
| BR (1) | BR8304961A (en) |
| CA (1) | CA1217056A (en) |
| CH (1) | CH660566A5 (en) |
| DE (1) | DE3332807A1 (en) |
| ES (1) | ES8502631A1 (en) |
| FR (1) | FR2532873A1 (en) |
| GB (1) | GB2127725B (en) |
| IT (1) | IT1209910B (en) |
| SE (1) | SE454493B (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6393553A (en) * | 1986-10-03 | 1988-04-23 | Mitsubishi Metal Corp | Centerless grinder |
| JP2793653B2 (en) * | 1989-09-08 | 1998-09-03 | 株式会社日立製作所 | Small electric motor |
| CN104259992B (en) * | 2014-09-26 | 2017-07-21 | 郑州磨料磨具磨削研究所有限公司 | Ceramic superhard abrasive material grinding tool abrasive material removal device |
| CN114536110B (en) * | 2022-03-03 | 2023-03-24 | 华辰精密装备（昆山）股份有限公司 | A real-time error compensation method for complex contour grinding of non-circular components |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR1255708A (en) * | 1960-04-28 | 1961-03-10 | Haefeli & Co | Method and device for processing chip removal tools |
| US3060647A (en) * | 1961-03-31 | 1962-10-30 | Cincinnati Milling Machine Co | Phase-out device for grinding machine |
| US3590534A (en) * | 1968-11-27 | 1971-07-06 | Litton Industries Inc | Wheel wear compensation |
| JPS578072A (en) * | 1980-06-18 | 1982-01-16 | Toyoda Mach Works Ltd | Detection of use limit of grinding wheel of grinder |
-
1983
- 1983-08-31 GB GB08323301A patent/GB2127725B/en not_active Expired
- 1983-09-06 AU AU18764/83A patent/AU1876483A/en not_active Abandoned
- 1983-09-09 IT IT8348945A patent/IT1209910B/en active
- 1983-09-12 FR FR8314482A patent/FR2532873A1/en not_active Withdrawn
- 1983-09-12 DE DE19833332807 patent/DE3332807A1/en not_active Withdrawn
- 1983-09-13 SE SE8304918A patent/SE454493B/en not_active Application Discontinuation
- 1983-09-13 CH CH4978/83A patent/CH660566A5/en not_active IP Right Cessation
- 1983-09-13 BR BR8304961A patent/BR8304961A/en unknown
- 1983-09-13 ES ES525564A patent/ES8502631A1/en not_active Expired
- 1983-09-14 CA CA000436709A patent/CA1217056A/en not_active Expired
- 1983-09-14 BE BE0/211532A patent/BE897754A/en not_active IP Right Cessation
- 1983-09-14 JP JP58168488A patent/JPS59134660A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| DE3332807A1 (en) | 1984-03-15 |
| SE8304918D0 (en) | 1983-09-13 |
| AU1876483A (en) | 1984-03-22 |
| JPS59134660A (en) | 1984-08-02 |
| FR2532873A1 (en) | 1984-03-16 |
| SE8304918L (en) | 1984-03-15 |
| GB8323301D0 (en) | 1983-10-05 |
| GB2127725B (en) | 1986-07-16 |
| IT1209910B (en) | 1989-08-30 |
| GB2127725A (en) | 1984-04-18 |
| BR8304961A (en) | 1984-04-24 |
| ES525564A0 (en) | 1985-01-16 |
| SE454493B (en) | 1988-05-09 |
| ES8502631A1 (en) | 1985-01-16 |
| CH660566A5 (en) | 1987-05-15 |
| BE897754A (en) | 1984-01-02 |
| IT8348945A0 (en) | 1983-09-09 |
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