U.S. patent application number 10/427328 was filed with the patent office on 2004-01-08 for method for dressing or profiling of an essentially cylindrical grinding worm.
Invention is credited to Breitschaft, Friedrich, Faulstich, Ingo, Peiffer, Klaus.
Application Number | 20040005843 10/427328 |
Document ID | / |
Family ID | 29225098 |
Filed Date | 2004-01-08 |
United States Patent
Application |
20040005843 |
Kind Code |
A1 |
Breitschaft, Friedrich ; et
al. |
January 8, 2004 |
Method for dressing or profiling of an essentially cylindrical
grinding worm
Abstract
Method for dressing or profiling an essentially cylindrical
grinding worm on a machine suitable for continuous generating
grinding in the diagonal method. The method comprises providing an
essentially cylindrical gear used as a dressing tool with the
dressing tool being provided with an abrasive coating on that
surface which is active in the dressing process and bringing the
dressing tool into contact with the grinding worm and profiling at
least one flank of the grinding worm in a tangential or diagonal
method.
Inventors: |
Breitschaft, Friedrich;
(Grossbottwar/Winzerhausen, DE) ; Faulstich, Ingo;
(Ludwigsburg, DE) ; Peiffer, Klaus; (Ludwigsburg,
DE) |
Correspondence
Address: |
THE GLEASON WORKS
1000 UNIVERSITY AVENUE
P O BOX 22970
ROCHESTER
NY
146922970
|
Family ID: |
29225098 |
Appl. No.: |
10/427328 |
Filed: |
May 1, 2003 |
Current U.S.
Class: |
451/47 ;
125/11.01; 451/56 |
Current CPC
Class: |
B24B 53/075 20130101;
B23F 23/1231 20130101 |
Class at
Publication: |
451/47 ; 451/56;
125/11.01 |
International
Class: |
B24B 001/00; B24B
053/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 8, 2002 |
DE |
10220513.2 |
Claims
What is claimed is:
1. A method for dressing or profiling an essentially cylindrical
grinding worm on a machine suitable for continuous generating
grinding in the diagonal method, said method comprising: providing
an essentially cylindrical gear used as a dressing tool with said
dressing tool being provided with an abrasive coating on that
surface which is active in the dressing process, bringing said
dressing tool into contact with the grinding worm and profiling at
least one flank of the grinding worm in a tangential or diagonal
method.
2. The method of claim 1 wherein the dressing tool is chucked on a
workpiece spindle and that the existing axes of the machine are
used for generating dressing motion between the dressing tool and
the grinding worm.
3. The method of claim 1 wherein the dressing tool is provided with
a helix angle independent of the helix angle of the workpiece to be
ground.
4. The method of claim 1 wherein the dressing tool dresses single
or multi start grinding worms.
5. The method of claim 1 wherein the machine used for the dressing
process is set up as a hobbing machine for hobbing worm wheels
using the tangential method or set up for diagonal milling of
cylindrical gears and wherein the parameters of feed, advance, and
number of revolutions of the grinding worm have to be coordinated
with the dressing.
6. The method of claim 1 wherein the grinding worm is rotated
during the dressing operation at any number of revolutions.
7. The method of claim 1 wherein the grinding worm is rotated
during the dressing operation at the number of revolutions at which
it is rotated during the subsequent grinding operation of the
workpiece.
8. The method of claim 1 wherein both flanks of the grinding worm
are dressed in a single pass.
9. The method of claim 1 wherein the grinding worm is being dressed
or profiled in the tangential method or the diagonal method with a
small axial component and that the dressing tool is displaced
relative to the grinding worm in the direction of the dressing tool
axis after a certain number of dressing or profiling operations and
is rotated corresponding to the enveloping screw of the dressing
tool and further dressing or profiling operations are subsequently
performed.
Description
FIELD OF THE INVENTION
[0001] The invention relates to a method for dressing or profiling
of an essentially cylindrical grinding worm.
BACKGROUND OF THE INVENTION
[0002] Cylindrical grinding worms are used for continuous
generating grinding operations. The economic efficiency of the
process and the precision of the machined gears are significantly
influenced by the dressing or profiling process.
[0003] Today, dressing (profiling) is mostly performed on the
machine. This requires the employment of dressing devices. Those
machines are expensive and they require highly precise slide guides
and movements in the dressing process that are very accurately
synchronized with the movement of the grinding worm. Moreover, the
dressing devices require considerable space and isolation from
contamination, e.g. by minute grinding chips or dressing tool
particles, which may in part become quite costly.
[0004] Another disadvantage of the well-known dressing devices is
that for control-technical reasons, the dressing process must be
performed at a slow revolution of the grinding worm. This problem
increases with an increase in the number of starts of the grinding
worm. These circumstances do not only result in a long dressing
time but deformations and possibly displacements of the grinding
worm, which have a negative effect on the geometry of the ground
gears, occur at working speed. Moreover, dressing with commonly
used dressing devices is not performed at the very spot where the
workpiece is subsequently machined. However, it is desirable for
precision purposes that the dressing process takes place at the
very spot at which the grinding worm will subsequently machine the
workpiece.
[0005] One method is known according to which a diamond coated
dressing gear is used for profiling a grinding worm. With this
method, grinding worm and dressing gear are arranged at crossed
axes. The two objects will rotate according to the ratio of the
tooth number of the dressing gear to the number of starts of the
grinding worm. Feed occurs either radially up to the nominal center
distance followed by a process of cutting free, or both objects are
adjusted to the nominal center distance and a feed motion is
performed in the direction of the workpiece or of the tool
circumference. A first grinding worm flank is profiled during this
process and the direction of the feed motion is subsequently
reversed and the second flank of each grinding worm tooth space is
profiled.
[0006] With this method, the grinding worm receives a globoid like
shape. The process is performed very quickly. However, the
precision of the subsequently ground gears is in most cases
insufficient for mounting the gears into low-noise gear boxes
without finishing the tooth flanks, e.g. by shave-grinding.
However, such an additional operation is highly undesirable.
[0007] One reason for the insufficient precision of the ground
wheels lies in the insufficient precision of the dressing gears.
Roughly simplified, the following holds true: at dressing, the
enveloping geometry of the dressing gear is transferred to the
grinding worm and during the subsequent grinding operation it is
transferred from the grinding worm to the workpiece. There is line
contact on transferring the enveloping geometry of the dressing
gear to the grinding worm. Under ideal conditions, the entire
surface of each flank of the dressing gear takes part in the
profiling of the grinding worm. Each flank modification which the
toothed gears to be ground shall receive must therefore be provided
for in the dressing gear. As a result, each different tooth design
requires a corresponding differently designed dressing gear.
[0008] It is an object of the invention to develop a method that
can be applied at working speed of the grinding worm to be dressed
and wherein the grinding worm is dressed or profiled at the very
spot where machining is subsequently performed. It is desirable
that the method is inexpensive, operates with precision, requires
little dressing time, minimal space, and shows a low risk of
contamination of critical machine components.
SUMMARY OF THE INVENTION
[0009] In the inventive method the dressing tool is essentially in
the form cylindrical toothed gear. It is provided, at least in the
area of its active surface, with a corresponding abrasive coating.
The dressing tool is chucked on the machine instead of the
workpiece, for example. It can, of course, also be chucked on the
workpiece spindle axially displaced relative to the workpiece. It
is furthermore possible to chuck the dressing gear at a different
location relative to the grinding worm. This, however, requires a
more complicated design.
[0010] The cylindrical grinding worm makes it possible to
manufacture essentially cylindrical toothed gears with high
precision in an axial or diagonal method. In this process dressing
gears can be employed which are unmodified in their flank line.
Such dressing gears can be manufactured with more precision than
gears that are modified in their flank line. The flank line
modifications required for the gears to be machined can be created
very precisely with the cylindrical grinding worm by corresponding
machine movements in the axial or diagonal method.
[0011] On dressing of an essentially cylindrical grinding worm in
the tangential method only a small strip of the dressing gear
flank, practically only one line per flank, is active. In contrast
thereto, as has already been mentioned, the entire surface of each
and every flank of the dressing gear is used for dressing of a
globoid-like grinding worm. A line can, of course, be produced with
more precision than a surface. Therefore, it can be taken as a fact
that gears which are ground by an essentially cylindrical grinding
worm are more precise than gears ground by a globoid-like grinding
worm, even if both grinding worms are being shaped by a gear type
dressing tool. Moreover, as has also been mentioned already, for
dressing of a globoid-like grinding worm, a different dressing gear
design is required for each workpiece gear design.
[0012] It follows from the foregoing that dressing of a
globoid-like grinding worm using gear type dressing tools leaves
much to be desired, particularly with respect to the precision and
flexibility that can be accomplished.
[0013] The essentially cylindrical grinding worm can be dressed in
a position that it will occupy on the machine when the workpiece is
subsequently machined. In contrast to the prior art of dressing
cylindrical grinding worms, optimal conditions for a high precision
of the grinding worm and the gear to be subsequently ground are
thereby achieved.
BRIEF DESCRIPTION OF THE DRAWING
[0014] The drawing shows a perspective view of a gear grinding
machine of the prior art for toothed wheels.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0015] The machine of the FIGURE is comprised of a bed 1 on which a
radial slide 2 displaceable in direction X and a tangential slide 3
displaceable in direction Y are arranged.
[0016] An axial slide 4 is displaceable in direction Z. The axial
slide 4 is connected by its linear guides with a swivel slide 5.
The axial slide 4 can be swiveled in direction A with the help of
this swivel slide and can, because the swivel slide 5 is connected
with the tangential slide 3, be displaced in direction Y.
[0017] The workpiece spindle 6 and its drive are housed inside of
the axial slide 4. Workpiece spindle 6 holds a workpiece (not
illustrated).
[0018] The radial slide 2 carries the tool spindle (not
illustrated), the tool 7 embodied as a cylindrical grinding worm,
and the tool drive 8; it further carries the base for receiving a
conventional dressing device. Such a dressing device is comprised,
for example, of one or more diamond-coated dressings discs (not
illustrated) with bearings and drives. Advantageously, the axis of
the dressing disc(s) runs parallel to the rotational axis of the
grinding worm 7.
[0019] The dressing device is displaceable in direction U (parallel
to X) by a U slide 9 and in direction V (parallel to Y) by a V
slide 10. When working with one dressing disc, for example, the
dressing process is performed as follows:
[0020] The dressing disc is adjusted to depth (relative to the
grinding worm 7) in direction U and is set in rotation in order to
create the dressing-cutting speed. It is furthermore displaced in
direction V synchronously to the rotation of the grinding worm such
that the required lead of the grinding worm is created.
[0021] The drawing shows distinctly that the working location and
the dressing location are located opposite of each other, at least,
approximately diametrically relative to the grinding worm diameter.
For precision purposes, however, they should coincide.
[0022] Although the dressing gears recommended herein show
significant advantages over the dressing gears required for
dressing/profiling of globoid-like grinding worms, dressing gears
designed for dressing/profiling of globoid-like grinding worms can
also be employed for dressing/profiling of essentially cylindrical
grinding worms. However, in that event, shifting the dressing gear
or working in the diagonal method are practically impossible if the
gears to be ground require a considerable amount of helix
modification.
[0023] In the inventive method the dressing wheel is, for example,
chucked on the spindle 6 instead of the workpiece. The U slide 9,
the V slide 10, the guides associated therewith, drives and
controls for the slide movements, the dressing wheels, the bearings
thereof, drives and controls become obsolete thereby. The space
required for the dressing gear for the subsequent grinding
operation of the workpiece already exists.
[0024] The inventive method does not require a differently designed
dressing gear for each different workpiece tooth design, either.
Rather, the profiling or dressing of cylindrical grinding worms
requires only a single dressing gear design for practically all
gears having the same basic rack tooth profile. It should be noted,
however, that strictly speaking, each change of a profile
modification will lead to a change in the basic rack tooth profile.
However, calculations show that in many cases a certain range of
workpiece parts can be machined with a basic rack tooth profile
that takes into account a certain profile modification. This
applies in particular to cases in which the profile modification
shows only a profile crowning. The dressing gear does not require
any flank line modification. It can be manufactured more easily and
more precisely than dressing gears required for dressing of
globoid-like worms. The dressing gear can practically have any
helix angle, even, for example, a helix angle of 0.degree.. The
dressing process can be performed at the number of revolutions of
the worm, at which the worm will subsequently machine the
workpieces. It poses no difficulty whatsoever to very precisely
dress or profile even multi start worms at a very high number of
revolutions of the worm. Each and every movement of the tangential
or diagonal method, required for dressing the worms can be
performed via the machine axes which already exist.
[0025] At least the flanks of the grinding worm chucked in the tool
spindle are profiled in the tangential or diagonal methods. In this
dressing process, the machine is used like a hobbing machine for
hobbing worm wheels using the tangential method or as for diagonal
hobbing. In this process, only the technological parameters of
feed, advance, and number of revolutions of the grinding worm 7
have to be coordinated with the actual dressing task to be
performed.
[0026] Because the grinding worm can be rotated during the dressing
process at a high number of revolutions, the dressing time is very
short. In the dressing process described herein, the right and the
left flanks of the grinding worm 7 can be dressed in a single pass
or successively in separate passes. The method described herein
makes it also possible in certain cases to dress the area of the
root of the teeth of the grinding worm 7, the tip area or the
transitional area between the tip area and the flanks, in a single
pass.
[0027] In the dressing process described herein the grinding worms
7 are dressed with high precision and with high economic
efficiency. As a result the workpieces/gears machined by the
grinding worms can also be machined economically and, in
particular, with high precision.
[0028] Because only a small part of the width of the dressing tool
is used in many cases when operating using the tangential method or
the diagonal method with a small axial component of feed motion,
the tool can, e.g., after having become worn out in a certain area
of its width, be shifted and portions of the tool width, that have
not been used yet can be utilized. This measure can significantly
reduce the costs for the dressing tool and thereby increase the
economic efficiency of the dressing process. In the case of a spur
toothed dressing tool the shifting movement consists of merely
displacing the dressing tool in the direction of its axis. In the
case of a helical dressing tool, in addition to the displacement in
the direction of the tool axis, a rotation corresponding to the
helix of the enveloping screw of the dressing tool is required.
[0029] While the invention has been described with reference to
preferred embodiments it is to be understood that the invention is
not limited to the particulars thereof. The present invention is
intended to include modifications which would be apparent to those
skilled in the art to which the subject matter pertains without
deviating from the spirit and scope of the appended claims.
* * * * *