U.S. patent application number 16/795917 was filed with the patent office on 2020-08-20 for method for dressing a grinding tool.
The applicant listed for this patent is Klingelnberg AG. Invention is credited to Martin Schweizer.
Application Number | 20200262028 16/795917 |
Document ID | 20200262028 / US20200262028 |
Family ID | 1000004701432 |
Filed Date | 2020-08-20 |
Patent Application | download [pdf] |
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United States Patent
Application |
20200262028 |
Kind Code |
A1 |
Schweizer; Martin |
August 20, 2020 |
METHOD FOR DRESSING A GRINDING TOOL
Abstract
Method for dressing a grinding tool by means of a machine tool
including dressing the grinding tool with a form dressing roller
and generating a tool profile on the grinding tool by a contact
between the rotating grinding tool and the rotating form dressing
roller along a dressing path, and generating relative movement
therebetween along the dressing path automatically with the aid of
two or more NC axes, wherein during the relative movement along the
dressing path and during the contact between the form dressing
roller and the grinding tool, each of the NC axes has an axial
velocity with an absolute value greater than zero, and none of
these NC axes carries out a directional reversal or comes to a
standstill.
Inventors: |
Schweizer; Martin; (Rastatt,
DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Klingelnberg AG |
Zurich |
|
CH |
|
|
Family ID: |
1000004701432 |
Appl. No.: |
16/795917 |
Filed: |
February 20, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B24B 53/062 20130101;
B24B 53/085 20130101 |
International
Class: |
B24B 53/085 20060101
B24B053/085; B24B 53/06 20060101 B24B053/06 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 20, 2019 |
EP |
19158274.1 |
Claims
1. A method comprising: mounting a dressable grinding tool in a
machine tool; mounting a form dressing roller in the machine tool;
rotating the grinding tool, rotating the dressing roller; and
dressing the grinding tool with the form dressing roller, and
generating a tool profile on the grinding tool by relative movement
and contact between the rotating grinding tool and the rotating
form dressing roller along a dressing path, wherein the method
includes generating said relative movement along the dressing path
automatically using at least two NC axes of the machine tool; and
wherein, during the relative movement along the dressing path and
during the contact between the form dressing roller and the
grinding tool, each of the at least two NC axes defines an axial
velocity with an absolute value greater than zero, and none of the
at least two NC axes reverses direction or comes to a
standstill.
2. The method according to claim 1, wherein the dressable grinding
tool defines a dressable grinding wheel.
3. The method according to claim 2, wherein the grinding wheel
defines a wheel profile defining a wheel profile cross section
defining at least one local minimum and/or at least one local
maximum, wherein the local minimum and/or local maximum are dressed
in a continuous pass.
4. The method according to claim 1, wherein the grinding tool
defines a dressable grinding worm.
5. The method according to claim 4, wherein the grinding tool
defines a grinding worm defining a worm profile defining a worm
profile cross section defining a plurality of local minima and/or
local maxima, and wherein the dressing step includes dressing at
least one local minimum and/or one local maximum in a continuous
pass.
6. The method according to claim 1, wherein the grinding tool
defines a profile defining a profile cross section defining at
least one local minima and/or local maxima, and the step of
generating relative movement includes generating two-dimensional
axial movement using two of the at least two NC axes of the machine
tool, and using a third of said at least two NC axes to define the
dressing path as a three-dimensional dressing path.
7. The method according to claim 3, wherein the grinding tool
defines a profile defining a profile cross section defining at
least one local minima and/or local maxima, and the step of
generating relative movement includes generating a two-dimensional
axial movement using two of the at least two NC axes of the machine
tool, and using a third of said at least two NC axes to define the
dressing path as a three-dimensional dressing path.
8. The method according to claim 1, wherein one of the NC axes
defines a linear axis.
9. The method according to claim 1, wherein one of the at least two
NC axes defines a pivot axis or rotational axis.
10. The method according to claim 8, wherein one of the at least
two NC axes defines a pivot axis or rotational axis.
11. The method according to claim 1, wherein at least one of the at
least two NC axes define linear axes, wherein the axial velocity of
each of the linear axes defines an absolute value of at least 1
.mu.m/s.
12. The method according to claim 11, wherein the absolute velocity
is at least 10 .mu.m/s.
13. The method according to claim 1, wherein at least one of the at
least two NC axes defines a rotational axis or a pivot axis,
wherein each of the at least one of the at least two NC axes
defining a rotational axis or pivot axis defines a rotational
velocity or pivot velocity defining an absolute value of least
1*10.sup.-6.degree./s.
14. The method according to claim 13, wherein the absolute value of
said rotational velocity or pivot velocity is at least
10*10.sup.-6.degree./s.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit under 35 U.S.C. .sctn.
119(e) to European patent application no. EP19158274.1 filed Feb.
20, 2019, which is hereby expressly incorporated by reference as
part of the present disclosure.
FIELD OF THE INVENTION
[0002] The present disclosure generally relates to methods for
dressing a grinding tool by means of a machine tool.
BACKGROUND
[0003] Dressing methods are used to sharpen and form grinding tools
for the fine machining or hard fine machining of workpieces, such
as gear wheels or the like.
[0004] To achieve a high precision with the least possible
deviations from the required target geometry during the grinding of
the workpiece to be machined using the dressed grinding tool, the
dressing of the grinding tool preceding the grinding machining also
has to take place with high accuracy. It is thus apparent that
inadequate dimensional accuracy of the grinding tool geometry
generated in the dressing procedure can be reflected directly in
manufacturing deviations of the workpiece to be ground using the
grinding tool.
[0005] During the dressing of the grinding tool, a relative
movement takes place between the rotating grinding tool to be
dressed and the rotating form dressing roller with the aid of NC
axes of a machine tool. The dressing path, which describes the
forming contact between the dressing roller and the grinding tool,
is therefore traveled along with the aid of the NC axes. Errors in
the axial movements of these NC axes therefore have a
disadvantageous effect on the profile accuracy of the generated
grinding tool profile, so that the machining accuracy of the
workpiece to be machined using the grinding tool dressed in this
manner is also negatively affected.
[0006] A frequently occurring deviation of the actual position from
the target position in the axial movements of the NC axes arises if
one or more of the participating NC axes has to be moved out of a
standstill or with a directional reversal during the forming
contact between the form dressing roller and the grinding wheel. In
both cases, the affected NC axis has to be accelerated from a state
of static friction into a state of sliding friction, so that a
discontinuity in the time curve of the acting forces or a jerk
arises (stick-slip effect).
[0007] One example of a known path error of a machine tool during
the dressing procedure, which results from a directional reversal
of an NC axis, is shown in FIG. 1. The NC axis in a Y direction (Y
position) is implemented by a linear axis. The Y position shown in
FIG. 1 therefore represents the movement route of this linear axis
in millimeters. An NC axis in a Z direction (Z position) is
implemented by a further linear axis. The Z position shown in FIG.
1 therefore represents the movement route of this further linear
axis in millimeters.
[0008] The curve having the reference sign 1 represents the
predetermined target route which is to be implemented to travel
along a dressing path as the relative movement between a dressing
roller and a grinding tool to be dressed by means of the linear
axes in the Y direction and Z direction. The curve having the
reference sign 2 describes the actual route which is actually
implemented by the NC axes in the Y direction and Z direction.
[0009] The target route 1 has a local minimum 3, so that the linear
axis of the Y direction has to carry out a direction change to
travel along the target route 1. During the direction change, the
linear axis of the Y direction comes to a short-term standstill and
enters a state of static friction, so that proceeding from the
local minimum 3, a growing deviation of the actual route 2 from the
target route 1 can be seen, wherein the linear axis of the Y
direction remains at a value of approximately 287.962 mm, while the
linear axis of the Z direction continuously moves further. In this
manner, a target-actual deviation of the Y position of
approximately 0.004 mm results, the absolute value of which is
illustrated by the double arrow 4.
[0010] It is self-evident that the disadvantageous effect of a
directional reversal and/or a standstill of an NC axis, which is
described with FIG. 1 for two linear axes, also exists for a
standstill or a directional reversal of a pivot axis or rotational
axis, which generates the travel along a dressing path in
cooperation with one or more linear and/or pivot axes.
SUMMARY
[0011] Against this background, the present disclosure is based on
the technical problem of specifying a method for dressing a
grinding tool of the type mentioned at the outset, which in at
least some embodiments does not have the above-described
disadvantages or at least has them to a lesser extent and/or
enables enhanced accuracy in the dressing of a grinding tool.
[0012] A method for dressing a grinding tool by means of a machine
tool, has in at least some embodiments the following method
steps:
[0013] providing a dressable grinding tool;
[0014] dressing the grinding tool by means of a form dressing
roller,
[0015] wherein the tool profile to be generated on the grinding
tool is formed by a contact between the rotating grinding tool and
the rotating form dressing roller along a dressing path,
[0016] wherein a travel along the dressing path takes place
automatically with the aid of two or more NC axes of the machine
tool, which generate a relative movement between the rotating
grinding tool and the rotating form dressing roller;
[0017] wherein during the travel along the dressing path and while
the form dressing roller is in forming contact with the grinding
tool, it is provided,
[0018] that each of the NC axes generating the relative movement
between the rotating grinding tool and the rotating form dressing
roller has an axial velocity, the absolute value of which is
greater than zero, wherein none of these NC axes carries out a
directional reversal or comes to a standstill.
[0019] Because none of the NC axes used for traveling along the
dressing path comes to a standstill or carries out a directional
reversal, a static friction state can be avoided for the respective
NC axes and the deviations accompanying this. In at least some
embodiments, the NC axes are exclusively moved in a state of
sliding friction during the travel along the dressing path.
[0020] When reference is made in the present case to the NC axes
which generate the travel along the dressing path and/or the
relative movement between the rotating grinding tool and the
rotating form dressing roller, in this case these are not the
spindle drives which set the form dressing roller and the grinding
tool into rotation about the respective tool or workpiece spindle
axis thereof, respectively, but rather the NC axes which effectuate
a displacement of a contact point or contact region in the forming
contact between the grinding tool and the form dressing roller, for
example, linear or pivot axes.
[0021] The NC axes mentioned can be linear axes arranged in
accordance with Cartesian coordinates.
[0022] The NC axes can alternatively or additionally comprise
linear axes which are oriented inclined and/or skewed in relation
to one another.
[0023] The NC axes can comprise rotational and/or pivot axes.
[0024] The term "form dressing roller" means in the present case
that the profile of the grinding tool to be dressed is generated
kinematically, i.e., by a relative movement of the form dressing
roller in relation to the grinding wheel, wherein in some
embodiments there is not a linear contact but rather a point
contact between the form dressing roller and the grinding tool. In
contrast to a profile dressing roller, which specifies the profile
of the grinding wheel in the linear contact solely by way of its
profile shape, the form dressing roller mentioned here therefore
does not comprise the profile of the grinding wheel as the negative
form inherent to the dressing tool.
[0025] In at least some embodiments, one of the NC axes generating
the relative movement between the rotating grinding tool and the
rotating form dressing roller is a linear axis.
[0026] Alternatively or additionally, in at least some embodiments,
one of the NC axes generating the relative movement between the
rotating grinding tool and the rotating form dressing roller is a
pivot axis or rotational axis.
[0027] The abbreviation "NC" stands in a known manner for "numeric
control" and is to be understood in the scope of this text such
that the relevant NC axis is movable with the aid of a machine
controller and, in at least some embodiments, in the scope of a
fully automatic program sequence.
[0028] When reference is made in the present case to an NC axis, in
this case this is thus a unit for adjusting a relative position of
the tool, the dressing roller here, in relation to the workpiece,
the grinding tool here, or vice versa. Such an NC axis typically
has a drive which can move a movable element over a predetermined
angle and/or length range. For this purpose, the movable element is
movably and/or rotatably mounted along a guide. The mounting or
guiding of the relevant movable element can be embodied as
hydrodynamic, hydrostatic, aerostatic, or rolling. A sliding
carriage translationally movable along a slide rail can be
mentioned as an example of a linear guide.
[0029] When reference is made in the present case to an NC axis
which is a linear axis, this is thus, for example, a linear axis or
linear unit having spindle drive, ballscrew drive, toothed belt
drive, direct drive, or the like in this case.
[0030] When reference is made in the present case to an NC axis
which is a rotational axis or pivot axis, this is thus, for
example, in this case a rotational axis or pivot axis having
electromotive, hydraulic, or pneumatic rotational drive, for
example, rotational drives according to the steep thread principle
or the toothed rack pinion principle.
[0031] Thus, for example, a spindle which bears the rotating
dressing roller can be displaceable and/or pivotable by means of
two or more linear axes and/or pivot axes in a workspace of the
machine tool to execute a relative movement in relation to the
grinding tool to be dressed. Furthermore, a spindle which bears the
rotating grinding tool can alternatively or additionally be
displaceable and/or pivotable by means of two or more linear axes
and/or pivot axes in a workspace of the machine tool in order to
execute a relative movement in relation to the dressing tool.
[0032] According to at least some embodiments of the method, the
dressable grinding tool is a dressable grinding wheel. The accuracy
in the dressing of the grinding wheel can accordingly be improved
with the aid of the method.
[0033] According to at least some embodiments of the method, the
grinding wheel has a grinding profile, the grinding profile cross
section of which comprises at least one local minimum and/or at
least one local maximum, wherein the local minimum and/or local
maximum are dressed in a continuous pass. The shape or profile of
the wheel profile cross section can be defined by a curve. This
curve may have a local minimum and/or a local maximum.
[0034] When reference is made in the present case to a "continuous
pass" this thus means that the dressing roller dresses the local
minimum and/or local maximum of the grinding profile cross section
of the grinding tool to be dressed without setting down or lifting
off the dressing roller from the grinding tool in the continuous
forming contact. The wheel profile cross section is therefore not
dressed in a segmented manner, for example, in a rising region up
to a maximum and a falling region which is dressed proceeding from
the maximum in a second pass or a second infeed. Rather, in the
present case the relevant local minimum and/or local maximum of the
grinding profile cross section of the grinding tool to be dressed
is passed over or dressed in a continuous contact between the
dressing roller and the grinding tool.
[0035] When reference is made here to a cross section or profile
cross section of a grinding tool, this is thus a plane of section
which comprises the axis of rotation of the spindle of the grinding
tool rotating around this axis of rotation.
[0036] During the dressing of profile cross sections having local
maximum and/or local minimum, the problem outlined in FIG. 1 can
exist, that one of the participating NC axes images the local
minimum and/or local maximum of the profile cross section by a
directional reversal. Such a profile cross section is intentionally
generated without standstill or directional reversal of one of the
NC axes, in order to keep the deviations from the target geometry
of the wheel profile cross section to be generated small.
[0037] A directional reversal of one of the NC axes, which
generates the relative movement between the rotating grinding tool
and the rotating form dressing roller, can be avoided in that
additional NC axes are used, the movements of which are
superimposed to generate a dressing path.
[0038] If, for example, a wheel profile cross section of a grinding
wheel having a local minimum or a depression is to be dressed, this
can be achieved according to the prior art by a two-dimensional
dressing path, which identically traces the profile cross section
in the plane of section. In this case, the dressing path contains
the local minimum of the profile cross section. If this dressing
path is now traveled along using, for example, two linear axes
arranged perpendicularly in relation to one another, one of these
axes has to image the minimum of the dressing path by way of a
directional reversal (cf. FIG. 1).
[0039] This can be prevented according to the present disclosure,
for example, in that the dressing path of the grinding profile
cross section, which is dressable two-dimensionally per se, is
embodied three-dimensionally, so that in addition a movement
transversely in relation to the above-described plane of section
takes place during the dressing. The dressing path accordingly not
only extends two-dimensionally in the radial and axial directions
of the grinding wheel, but rather moreover also extends
peripherally on the circumference around an angle range measured
around the axis of rotation of the grinding wheel. The wheel
profile discussed here having local minimum can thus be traveled
along, for example, with the aid of three linear axes along a
dressing path without local minimum, so that none of the three
linear axes passes through a directional reversal or comes to a
standstill.
[0040] In at least some embodiments, a profile of the grinding
tool, the profile cross section of which comprises one or more
local minima and/or local maxima, is dressable by a two-dimensional
axial movement by means of two NC axes of a machine tool, wherein
in addition a further third axis is used to carry out the dressing
along a three-dimensional dressing path.
[0041] It is obvious that the above statements on the wheel profile
cross section having local minimum and the participating linear
axes are to be understood as examples and case constellations
(configurations) having grinding tool profile cross sections having
one or more local minima and/or one or more local maxima may
similarly be specified and NC linear axes and/or NC pivot axes
and/or NC rotational axes may be used in this case to enable a
dressing of the profile of the grinding tool in a superimposed
movement, wherein each of the NC axes generating the relative
movement between the rotating grinding tool and the rotating form
dressing roller has an axial velocity, the absolute value of which
is greater than zero, wherein none of these NC axes carries out a
directional reversal or comes to a standstill.
[0042] According to at least some embodiments, the grinding tool is
a dressable grinding worm. The accuracy in the dressing of the
grinding worm can accordingly be improved with the aid of the
methods presented herein.
[0043] The grinding worm has in at least some embodiments a
grinding worm profile, the worm profile cross section of which
comprises a plurality of local minima and/or local maxima, wherein
at least one local minimum and/or one local maximum are dressed in
a continuous pass.
[0044] The statements made above relating to the grinding wheel on
the significance of the continuous pass apply similarly here. Thus,
minima and maxima of the relevant worm profile cross section are
dressed, for example, without segmenting in the region of the
minima or maxima, respectively.
[0045] In at least some embodiments, one or more of the NC axes are
linear axes, wherein each of the linear axes generating the
relative movement between the rotating grinding tool in the
rotating form dressing roller has an axial velocity, the absolute
value of which is greater than or equal to 1 .mu.m/s, for example,
greater than or equal to 10 .mu.m/s. The respective linear axis is
thus prevented from coming into a state of static friction during
the travel along the dressing path and/or while the dressing roller
is in forming contact with the grinding tool. It is self-evident
that the relevant linear axis is exclusively moved in one
direction--i.e., without directional reversal--during the dressing
and/or the travel along the dressing path in forming contact.
[0046] In at least some embodiments, one or more of the NC axes are
rotational axes or pivot axes, wherein each of the rotational axes
or pivot axes generating the relative movement between the rotating
grinding tool and the rotating form dressing roller has a
rotational velocity or pivot velocity, the absolute value of which
is greater than or equal to 1*10-6.degree./s, for example, greater
than or equal to 10*10-6.degree./s.
[0047] At least some embodiments can be implemented, for example,
with the aid of three linear axes, which are arranged in accordance
with a Cartesian coordinate system.
[0048] At least some embodiments can be implemented with the aid of
linear axes which are arranged inclined and/or skewed, i.e., for
example, are not arranged perpendicular to one another.
[0049] Alternatively or additionally, pivot and/or rotational axes
can be used to implement the teaching presented herein.
[0050] The relative arrangement of the respective NC axes or to
what extent a relevant NC axis effectuates a rotational and/or
translational relative movement is not decisive in each case here,
but rather that the condition required according to the present
disclosure is met, that during the travel down the dressing path
and while the form dressing roller is in forming contact with the
grinding tool, it is provided that each of the NC axes generating
the relative movement between the rotating grinding tool and the
rotating form dressing tool has an axial velocity, the absolute
value of which is greater than zero, wherein none of these NC axes
carries out a directional reversal or comes to a standstill.
[0051] This summary is not exhaustive of the scope of the present
aspects and embodiments. Thus, while certain aspects and
embodiments have been presented and/or outlined in this summary, it
should be understood that the present aspects and embodiments are
not limited to the aspects and embodiments in this summary. Indeed,
other aspects and embodiments, which may be similar to and/or
different from, the aspects and embodiments presented in this
summary, will be apparent from the description, illustrations,
and/or claims, which follow.
[0052] It should also be understood that any aspects and
embodiments that are described in this summary and do not appear in
the claims that follow are preserved for later presentation in this
application or in one or more continuation patent applications.
BRIEF DESCRIPTION OF THE DRAWINGS
[0053] FIG. 1 schematically shows the fundamental problem of the
present disclosure on the basis of two linear axes (prior art);
[0054] FIG. 2A schematically shows a grinding tool profile cross
section of a grinding tool;
[0055] FIG. 2B schematically shows a side view of the grinding tool
from FIG. 2A;
[0056] FIG. 2C schematically shows the grinding tool profile cross
section from FIG. 2A having a dressing roller;
[0057] FIG. 2D schematically shows a side view of the grinding tool
from FIG. 2C having the dressing roller in two positions;
[0058] FIG. 2E schematically shows a further side view of the
grinding tool from FIG. 2C having the dressing roller in two
positions;
[0059] FIG. 3 schematically shows a three-dimensional illustration
of two dressing path profiles along a surface of the grinding
tool.
DETAILED DESCRIPTION
[0060] Terms are used in conjunction with the present description
which are also used in relevant publications and patents. However,
it is to be noted that the use of these terms is merely to serve
for better comprehension. The inventive concepts and the scope of
protection of the claims are not to be restricted in the
interpretation by the specific selection of the terms. The
invention may be readily transferred to other term systems and/or
technical fields. The terms are to be applied accordingly in other
technical fields.
[0061] FIG. 1 has already been discussed at the outset to disclose
a fundamental problem. In summary, a deviation 4 of the actual
route 2 from the target route 1 can be avoided by avoiding a
directional reversal of an NC axis--according to FIG. 1 the Y axis.
An implementation of the solution according to at least some
embodiments means that the relevant grinding tool is dressed in
such a manner that the target route does not have a local minimum
for any of the participating NC axes in the Y direction and Z
direction, although the profile cross section of the grinding wheel
to be dressed has such a local minimum. A solution to this problem
is disclosed by way of example on the basis of FIGS. 2A-2E and FIG.
3.
[0062] FIG. 2A shows a grinding tool profile cross section 10 of a
dressable grinding tool 12. The grinding tool profile cross section
10 shown here can be a portion of a part of a profile cross section
of a grinding worm, the profile cross section of which extends in
the positive and negative Z direction over a multiple of the
portions shown in FIG. 2A. The grinding tool profile cross section
10 shown here can be a portion of a profile cross section of a
grinding wheel, which also extends further in the positive and
negative Z direction beyond the portion shown in FIG. 2A. The
grinding tool profile cross section 10 shown here can be the
profile cross section of a grinding wheel.
[0063] The coordinate axis (Z axis) identified with "Z" represents,
on the one hand, a coordinate of the Cartesian coordinate system X,
Y, Z shown in FIG. 2A. On the other hand, "Z" represents an NC
linear axis of a machine tool 14, which enables a linear and/or
translational movement of the grinding tool 12 along the coordinate
direction "Z". This applies similarly to the axes X and Y, so that
the Cartesian coordinate system X, Y, Z is not to be understood
solely as a virtual reference system, but rather is spanned by
three NC linear axes X, Y, Z oriented perpendicularly to one
another.
[0064] The grinding tool profile cross section has a local minimum
16, which is illustrated in the side view according to FIG. 2B by
the dashed circular line.
[0065] If this grinding profile 10 is now to be dressed using a
form dressing roller 18 according to FIG. 2C, the form dressing
roller 18 is typically moved two-dimensionally, i.e., exclusively
within the Y-Z plane spanned by the Y axis and Z axis, specifically
from a first contact point 20, toward a second contact point 22
located in the minimum 16, up to the contact point 24. The dressing
path thus resulting, which is indicated by the hollow arrows,
therefore identically images the profile cross section of the
grinding tool 12 in the Y-Z plane. The linear axis Y passes through
the described, disadvantageous directional reversal. The dressing
path represented by the hollow arrows and contact points 20, 22, 24
is therefore not according to disclosed methods.
[0066] It is self-evident that the described dressing path
represents a continuous pass along the profile of the grinding tool
12 and the contact points 20, 22, 24 are solely used as support
points to illustrate the course of the continuous dressing path.
The relative movement could alternatively extend proceeding from
the contact point 24 via the contact point 22 toward the contact
point 20.
[0067] A three-dimensional dressing path 26 is now used to dress
the grinding tool 12.
[0068] For this purpose, a movement in the X direction is
additionally superimposed on the movement in the Y direction and Z
direction. In this case, a dressing path 26, which is represented
by the solid arrows and the contact points 28, 30, 32, does not
comprise a local minimum. The dressing path can therefore be
traveled along continuously without directional reversal and
standstill of one of the linear axes X, Y, Z, wherein nonetheless
the local minimum of the profile cross section 10 is dressed in a
continuous pass.
[0069] In other words, the form dressing roller 18 is additionally
moved along a profile of the grinding wheel R(Z) in the
circumferential direction of the grinding tool, as indicated by the
angle .alpha..
[0070] A method for dressing the grinding tool 12 by means of the
machine tool 14 is therefore carried out, having the following
method steps.
[0071] Providing the dressable grinding tool 12; dressing the
grinding tool 12 by means of the form dressing roller 18, wherein
the tool profile 10 to be generated on the grinding tool 12 is
formed by a contact between the rotating grinding tool 12 and the
rotating form dressing roller 18 along a dressing path 26, wherein
a travel along the dressing path 26 takes place automatically with
the aid of three NC axes X, Y, Z of the machine tool 14, which
generate a relative movement between the rotating grinding tool 12
and the rotating form dressing roller 18; and wherein it is
provided during the travel along the dressing path 26 and while the
form dressing roller 18 is in forming contact with the grinding
tool 12 that each of the NC axes X, Y, Z generating the relative
movement between the rotating grinding tool 12 and the rotating
form dressing roller 18 has an axial velocity, the absolute value
of which is greater than zero, wherein none of these NC axes X, Y,
Z carries out a directional reversal or comes to a standstill.
[0072] FIG. 2E illustrates three positions of the form dressing
roller 18, which the dressing path 26 assumes in the continuous
forming contact with the grinding tool in an overview
illustration.
[0073] A comparison of a two-dimensional dressing path and the
three-dimensional dressing path according to disclosed methods is
shown in FIG. 3. The form dressing roller is not shown in FIG. 3 to
improve the comprehensibility.
[0074] The hollow circles and arrows again represent a
two-dimensional dressing path along the shaded surface of the
grinding tool 12 to be dressed and the solid circles and arrows
represent the dressing path for carrying out methods disclosed
herein. R(z) is the radius of the grinding tool.
[0075] To illustrate the required movement routes of the linear
axes X, Y, Z for the two-dimensional and the three-dimensional
dressing path, the dressing paths have been projected on the Y-Z
plane and the X-Z plane. It is apparent that the Y axis for the
two-dimensional dressing path has to carry out a directional
reversal to approach point 24 from the point 22. Furthermore, it is
recognizable that no movement of the X axis is required for the
two-dimensional dressing path. The profile of the grinding tool 12
is therefore dressable in a two-dimensional movement.
[0076] According to at least some embodiments, the dressing path 26
is selected according to the filled circles 28, 30, 32, wherein the
dressing path 26 does not comprise a local minimum in its
projection on the Y-Z plane and the X-Z plane. Each of the
participating linear axes X, Y, Z is therefore exclusively moved in
one direction, so that the dressing path 26 is traveled along
without standstill or directional change of one of the NC axes X,
Y, Z generating the relative movement between the form dressing
roller and the grinding tool.
[0077] Therefore, the following condition can be established to
determine a dressing path according "DY/DZ<=0 and
DX/DZ>=0":
[0078] as long as DR/DZ<=0: X=0, Y(Z)=R(Z), Z=Z(T), and
YMIN=Min(Y(Z));
[0079] if DR/DZ>0: X(Z)=SQRT(R.sup.2(Z)-YMIN.sup.2), Y(Z)=YMIN,
Z=Z(T), wherein T corresponds to the processing time, so that Z
functions as a guide axis for the synchronization of the
participating NC axes.
[0080] The arrangement of three linear axes X, Y, Z corresponding
to a Cartesian coordinate system is to be understood solely as an
example and is used to illustrate the fundamental principle of the
invention.
[0081] According to at least some embodiments, the method can be
implemented with the aid of linear axes which are arranged inclined
and/or skewed in relation to one another, i.e., for example, are
not arranged perpendicularly to one another. Alternatively or
additionally, pivot and/or rotational axes can be used.
[0082] In this case, the relative arrangement of the respective NC
axis or to what extent the relevant NC axis effectuates a
rotational and/or translational relative movement is not decisive,
but rather that the condition required is met that during the
travel along the dressing path and while the form dressing roller
is in forming contact with the grinding tool, it is provided that
each of the NC axes generating the relative movement between the
rotating grinding tool and the rotating form dressing roller has an
axial velocity, the absolute value of which is greater than zero,
wherein none of these NC axes carries out a directional reversal or
comes to a standstill.
[0083] While the above describes certain embodiments, those skilled
in the art should understand that the foregoing description is not
intended to limit the spirit or scope of the present disclosure. It
should also be understood that the embodiments of the present
disclosure described herein are merely exemplary and that a person
skilled in the art may make any variations and modification without
departing from the spirit and scope of the disclosure. All such
variations and modifications, including those discussed above, are
intended to be included within the scope of the disclosure.
* * * * *