EP0771249B1 - Grinding method and apparatus - Google Patents
Grinding method and apparatus Download PDFInfo
- Publication number
- EP0771249B1 EP0771249B1 EP95918090A EP95918090A EP0771249B1 EP 0771249 B1 EP0771249 B1 EP 0771249B1 EP 95918090 A EP95918090 A EP 95918090A EP 95918090 A EP95918090 A EP 95918090A EP 0771249 B1 EP0771249 B1 EP 0771249B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- workpiece
- speed
- grinding
- rotational speed
- wheel
- 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 - Lifetime
Links
- 238000000034 method Methods 0.000 title claims description 20
- 238000004513 sizing Methods 0.000 claims description 8
- 238000010586 diagram Methods 0.000 description 2
- 244000145845 chattering Species 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 229910003460 diamond Inorganic materials 0.000 description 1
- 239000010432 diamond Substances 0.000 description 1
Images
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
- B24B41/00—Component parts such as frames, beds, carriages, headstocks
- B24B41/007—Weight compensation; Temperature compensation; Vibration damping
-
- 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
- B24B1/00—Processes of grinding or polishing; Use of auxiliary equipment in connection with such processes
-
- 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
- B24B49/02—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 according to the instantaneous size and required size of the workpiece acted upon, the measuring or gauging being continuous or intermittent
Definitions
- This invention relates to a method of grinding a cylindrical workpiece surface.
- chatter-marks can be reduced by absolute truing of the grinding wheel, but this is time consuming and expensive, especially when the grinding surface is a super-abrasive such as diamond or CBN.
- GB-A-2268895 there is described and claimed a method of grinding a cylindrical workpiece surface in which the speed of rotation of the grinding wheel and/or the speed of rotation of the workpiece is changed one or more times during the final stage of grinding, the period of such rotational speed variation including at least part of the final dwell period in which sizing occurs, thereby to reduce chatter-marks on the workpiece.
- a method of grinding a cylindrical workpiece surface in which the speed of rotation of the grinding wheel and/or the speed of rotation of the workpiece is changed one or more times during the final stage of grinding in response to corresponding changes in a target value, the period of such rotational speed variation including at least part of the final dwell period in which sizing occurs, thereby to reduce chatter-marks on the workpiece, characterised by performing the steps of: measuring the speed of rotation of the wheel and/or of the workpiece during said final stage of grinding at each such desired change of speed, calculating a theoretical ratio of the rotational speed of the wheel to that of the workpiece for any given target value, and controlling the speeds of the wheel and/or workpiece in such a manner that if the fractional component of the theoretical ratio is 0.5 or less the fractional component of the actual ratio of the speed of the wheel to that of the workpiece for that target value is 0.25, and if the fractional component of the theoretical ratio is above 0.5, the fractional component of the actual ratio for that target value is
- the method may be applied to internal as well as external grinding.
- the speed variation effected is not dependent on vibration sensing of the grinding wheel or the workpiece.
- the rotational speed change is preferably practised by a rotational speed change which includes a change in the rotational speed of the workpiece.
- any change made will usually be decelerative.
- the rotational speed of the grinding wheel is kept constant.
- the rotational speed change may be initiated either after a predetermined number of rotations of the workpiece, where the number of turns per grinding cycle is controlled, and/or at a predetermined feed distance before the feed position for final sizing, as indicated in more detail below.
- the speed change effected may therefore be linear, reduce or increase at a rate relative to the above variables, or be of another controlled forms such as sinusoidal.
- the speed change is normally initiated during the slow approach to size feed, extending into the final dwell period in which sizing occurs.
- Figure 1 is a typical feed diagram for the grinding wheel in a grinding process for grinding a cylindrical workpiece.
- the grinding wheel feed includes a fine feed period 10 immediately prior to a stationary final dwell period 12 (size dwell) in which sizing occurs.
- At least one change in the rotational speed of the workpiece is initiated in the fine feed period, and this speed change is extended into at least part of the final dwell period 12.
- Means are provided for measuring the speed of the grinding wheel immediately prior to a change of speed of the workpiece, and the value of wheel speed is fed into a microprocessor associated with a servo controller for altering the speed of the workpiece.
- the target speed of the workpiece is also fed into the processor, which then calculates the ratio of the speed of the wheel to that of the workpiece. If the fractional part of the ratio (ie the mantissa) is 0.5 or less, the workpiece speed which was demanded by the operator of the grinding machine is adjusted slightly so that the mantissa becomes 0.25; alternatively if the calculated mantissa is above 0.5 it is adjusted to 0.75. In this manner any tendancy for chatter marks to form on the workpiece is significantly improved, in that the harmonics of the speed ratios of wheel/workpiece up the third harmonics are eliminated.
- the means 22 is preferably constituted by a servo-controller, which automatically initiates a change in the workspeed at the aforesaid time and for the aforesaid period, for example dependently on the feed position, the number of turns of the workpiece in the grinding cycle, and/or component size.
- the change effected is preferably not sudden, but is a relatively slow change which may be linear, sinusoidal or of any other desired form.
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Constituent Portions Of Griding Lathes, Driving, Sensing And Control (AREA)
- Grinding Of Cylindrical And Plane Surfaces (AREA)
Description
This invention relates to a method of grinding a cylindrical
workpiece surface.
It is well known that, when a cylindrical workpiece is being
ground, the grinding process produces vibrations which generate
lobes on the workpiece surface. This phenomenon is commonly
known as chattering, and the resulting distortions on the
workpiece are known as chatter-marks.
To some extent chatter-marks can be reduced by absolute truing
of the grinding wheel, but this is time consuming and
expensive, especially when the grinding surface is a
super-abrasive such as diamond or CBN.
It is an object of the present invention to provide a method
of reducing the tendency for generation of chatter-marks during
grinding.
In GB-A-2268895 there is described and claimed a method of
grinding a cylindrical workpiece surface in which the speed of
rotation of the grinding wheel and/or the speed of rotation of
the workpiece is changed one or more times during the final
stage of grinding, the period of such rotational speed
variation including at least part of the final dwell period in
which sizing occurs, thereby to reduce chatter-marks on the
workpiece.
According to the present invention there is provided a method
of grinding a cylindrical workpiece surface in which the speed
of rotation of the grinding wheel and/or the speed of rotation
of the workpiece is changed one or more times during the final
stage of grinding in response to corresponding changes in a
target value, the period of such rotational speed variation
including at least part of the final dwell period in which
sizing occurs, thereby to reduce chatter-marks on the
workpiece, characterised by performing the steps of: measuring
the speed of rotation of the wheel and/or of the workpiece
during said final stage of grinding at each such desired change
of speed, calculating a theoretical ratio of the rotational
speed of the wheel to that of the workpiece for any given
target value, and controlling the speeds of the wheel and/or
workpiece in such a manner that if the fractional component of
the theoretical ratio is 0.5 or less the fractional component
of the actual ratio of the speed of the wheel to that of the
workpiece for that target value is 0.25, and if the fractional
component of the theoretical ratio is above 0.5, the fractional
component of the actual ratio for that target value is 0.75.
In this way it is ensured that the ratio of the or each changed
speeds is not a whole integer or in the ratios of the second
or third harmonics, and thereby any chatter marks in the
workpiece are further reduced.
The method may be applied to internal as well as external
grinding.
Moreover, it is to be noted that the speed variation effected
is not dependent on vibration sensing of the grinding wheel or
the workpiece.
The rotational speed change is preferably practised by a
rotational speed change which includes a change in the
rotational speed of the workpiece.
If the speed variation includes change in the rotational speed
of the grinding wheel, any change made will usually be
decelerative. Preferably, however, the rotational speed of the
grinding wheel is kept constant.
The rotational speed change may be initiated either after a
predetermined number of rotations of the workpiece, where the
number of turns per grinding cycle is controlled, and/or at a
predetermined feed distance before the feed position for final
sizing, as indicated in more detail below.
Thus, the possibilities for workspeed variation are limitless
if its rotational speed is servo-controlled relative to time,
grinding wheel feed position, component size and/or number of
component turns.
The speed change effected may therefore be linear, reduce or
increase at a rate relative to the above variables, or be of
another controlled forms such as sinusoidal.
However, the speed change is normally initiated during the slow
approach to size feed, extending into the final dwell period
in which sizing occurs.
The practical implementation of the method of the
invention is exemplified with reference to the accompanying
drawings, in which:-
Figure 1 is a typical feed diagram for the grinding wheel in
a grinding process for grinding a cylindrical workpiece.
The grinding wheel feed includes a fine feed period 10
immediately prior to a stationary final dwell period 12 (size
dwell) in which sizing occurs.
In accordance with the invention, at least one change in the
rotational speed of the workpiece is initiated in the fine feed
period, and this speed change is extended into at least part
of the final dwell period 12.
Means are provided for measuring the speed of the grinding
wheel immediately prior to a change of speed of the workpiece,
and the value of wheel speed is fed into a microprocessor
associated with a servo controller for altering the speed of
the workpiece. The target speed of the workpiece is also fed
into the processor, which then calculates the ratio of the
speed of the wheel to that of the workpiece. If the fractional
part of the ratio (ie the mantissa) is 0.5 or less, the
workpiece speed which was demanded by the operator of the
grinding machine is adjusted slightly so that the mantissa
becomes 0.25; alternatively if the calculated mantissa is above
0.5 it is adjusted to 0.75. In this manner any tendancy for
chatter marks to form on the workpiece is significantly
improved, in that the harmonics of the speed ratios of
wheel/workpiece up the third harmonics are eliminated.
In the simplified grinding machine shown in Figure 2, wherein
the grinding wheel is referenced 14, the wheel feed indicated
at 16, the workpiece at 18 and the workpiece support at 20, a
means 22 is incorporated for changing the rotational speed of
the workpiece 18, as aforesaid.
The means 22 is preferably constituted by a servo-controller,
which automatically initiates a change in the workspeed at the
aforesaid time and for the aforesaid period, for example
dependently on the feed position, the number of turns of the
workpiece in the grinding cycle, and/or component size.
The change effected is preferably not sudden, but is a
relatively slow change which may be linear, sinusoidal or of
any other desired form.
Claims (10)
- A method of grinding a cylindrical workpiece surface in which the speed of rotation of the grinding wheel (14) and/or the speed of rotation of the workpiece (18) is changed one or more times during the final stage of grinding in response to corresponding changes in a target value, the period of such rotational speed variation including at least part of the final dwell period (12) in which sizing occurs, thereby to reduce chatter-marks on the workpiece, characterised by performing the steps of: measuring the speed of rotation of the wheel (14) and/or of the workpiece (18) during said final stage of grinding at each such desired change of speed, calculating a theoretical ratio of the rotational speed of the wheel to that of the workpiece for any given target value, and controlling the speeds of the wheel and/or workpiece in such a manner that if the fractional component of the theoretical ratio is 0.5 or less the fractional component of the actual ratio of the speed of the wheel to that of the workpiece for that target value is 0.25, and if the fractional component of the theoretical ratio is above 0.5, the fractional component of the actual ratio for that target value is 0.75.
- A method according to claim 1 in which the rotational speed variation is practised by a rotational speed change which includes a change in the rotational speed of the workpiece.
- A method according to claim 1 or claim 2 in which the speed variation includes a change in the rotational speed of the grinding wheel, such speed change being decelerative.
- A method according to claim 1 in which the workpiece speed is adjusted, while that of the grinding wheel is maintained constant.
- A method according to any one preceding claim in which the rotational speed variation is initiated either after a predetermined number of rotations of the workpiece, where the number of turns per grinding cycle is controlled, and/or at a predetermined feed distance before the feed position for final sizing.
- A method according to any one preceding claim in which the rotational speed of the workpiece is servo-controlled relative to the variables of time, grinding wheel feed position, workpiece size and/or number of workpiece rotations.
- A method according to any one preceding claim in which the speed change effected is linear, or reduces or increases at a rate relative to said variables, or is of another controlled form such as sinusoidal.
- A method according to any one preceding claim in which the speed change is initiated during the slow approach to size feed, extending into the final dwell period in which sizing occurs.
- A method according to any of the preceding claims in which the target value corresponds to a target rotational speed of the workpiece, which target speed is demanded by an operator of apparatus on which the method is performed.
- A method according to any one preceding claim in which internal and/or external grinding is performed on the cylindrical workpiece.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9414880A GB2291608B (en) | 1994-07-23 | 1994-07-23 | Grinding method and apparatus |
| GB9414880 | 1994-07-23 | ||
| PCT/GB1995/001069 WO1996003255A1 (en) | 1994-07-23 | 1995-05-11 | Grinding method and apparatus |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| EP0771249A1 EP0771249A1 (en) | 1997-05-07 |
| EP0771249B1 true EP0771249B1 (en) | 1999-11-24 |
Family
ID=10758781
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP95918090A Expired - Lifetime EP0771249B1 (en) | 1994-07-23 | 1995-05-11 | Grinding method and apparatus |
Country Status (6)
| Country | Link |
|---|---|
| EP (1) | EP0771249B1 (en) |
| AU (1) | AU2415295A (en) |
| DE (1) | DE69513527T2 (en) |
| ES (1) | ES2139206T3 (en) |
| GB (1) | GB2291608B (en) |
| WO (1) | WO1996003255A1 (en) |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CH595187A5 (en) * | 1975-12-20 | 1978-02-15 | Studer Ag Fritz | |
| US4604834A (en) * | 1985-10-03 | 1986-08-12 | General Electric Company | Method and apparatus for optimizing grinding |
| GB2268895B (en) * | 1992-07-18 | 1995-06-28 | Litton Uk Ltd | Grinding method and apparatus |
-
1994
- 1994-07-23 GB GB9414880A patent/GB2291608B/en not_active Expired - Fee Related
-
1995
- 1995-05-11 DE DE69513527T patent/DE69513527T2/en not_active Expired - Fee Related
- 1995-05-11 EP EP95918090A patent/EP0771249B1/en not_active Expired - Lifetime
- 1995-05-11 WO PCT/GB1995/001069 patent/WO1996003255A1/en not_active Ceased
- 1995-05-11 ES ES95918090T patent/ES2139206T3/en not_active Expired - Lifetime
- 1995-05-11 AU AU24152/95A patent/AU2415295A/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| DE69513527D1 (en) | 1999-12-30 |
| DE69513527T2 (en) | 2000-03-16 |
| WO1996003255A1 (en) | 1996-02-08 |
| GB2291608B (en) | 1996-11-06 |
| AU2415295A (en) | 1996-02-22 |
| EP0771249A1 (en) | 1997-05-07 |
| ES2139206T3 (en) | 2000-02-01 |
| GB2291608A (en) | 1996-01-31 |
| GB9414880D0 (en) | 1994-09-14 |
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