Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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GRINDING TOOL
The present invention relates to a grinding
tool with a single layer of abrasive grains
galvanized to the base body.
When manufacturing components of a high
qualit~ standard, for example, such as toothed
wheels and other workpieces with special profiles,
it is becoming more and more important for
achieving high precision and trueness to shape to
perform a further fine machining (finishing) step
after premachining and hardening. The fine
machining or finishing step for hardened
workpieces is commonly a grinding step.
When finishing hardened workpieces by so-
called shape-grinding a grinding tool such as a
grinding wheel is used that in the case of
grinding of toothings is provided with a profile
that corresponds to the profile of the gap between
the teeth to be ground. As a grinding material
(a~rasive material) of the grlnding tool in modern
fine machining steps of hardened materials
diamond, cubic-crystalline boronitride (CBN) or
other hlghly refractory materials are commonly
used.
The profile of the grinding wheel is
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conventionally produced such that the grinding
tool is sub~ected to a planing process in which,
for example, with a diamond planing roller the
grinding tool is profiled. Recent grinding
processes however employ a grinding tool which is
comprised of a base body that has been ground to
conform to the desired profile and which is
provided with a singla layer of abrasive grains.
The fixation of the abrasive grains on the base
body is achieved by a galvanic process whereby
commonly nickel is used as a binding material.
When CBN is used as the abrasive material the
average diameter of an abrasive grain dependlng on
the desired grindlng depth is typically between 20
and 600 ,um.
Usually the surface area of the base body to
which the abrasive grains are to be applied is
essentially entirely planar so that the abrasive
grains applied in a single layer and galvanically
connected thereto have the appearance of the
surface of a fine-grain abrasive paper. However,
it is known from U.S. patent 4,114j322 and German
Offenlegungsschrift 27 58 285 to provide the base
body with a plurality of grooves which, among
other things, serve to improve transport of the
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cooling lubricant necessary for the grinding
process to the respective grinding location.
It is known in the prior art to provide at
least segments of the grinding wheel such that,
when viewed under the microscope, they have a
plurality of abrasive grains ad;acent to one
another and galvanically connected to the base
body in order to thus form a grinding surface.
Accordingly, there are always at least islands or
segments present which provide the conventional
structure of a grinding wheel surface.
When such a grinding tool is used, the
cutting operation is performed with a
geometrically undefined cutting edge, i.e., the
individual abrasive grains remove microcuttings
from the surface of the workpiece. The
microcuttings are caught within a free space in
front of the abrasive grain essentially
corresponding to the space between ad~acent
abrasive grains before the microcuttings are
removed by the cooling lubricant or, in the case
of dry grinding, removed by the centrifugal forces
acting at the surface of the grinding tool.
With the known grinding tools it is thus an
accepted fact that the free space which is
necessary for an efficient cutting process is
statistically distributed, in other words, that it
is randomly formed during the course of the
galvanic fixation process of the abrasive grains
on the base body.
Experiments with galvanically bonded grinding
wheels however have shown that of the plurality of
abrasive grains distributed on the base body only
a few projecting abrasive grains actually
participate in the cutting process and that the
corresponding free space of the abrasive grains is
very important for a high service life of the
tool.
It is therefore an ob~ect of the present
inventlon to provide a shaped grinding tool with
a single layer of abrasive grains connected
galvanically to the base body which in comparison
to known tools exhibits a greater service life and
a more efficient cutting process. This means that
a tool shall be provided with which a great number
of workpieces with a high relative cutting volume
per time unit (number of removed cubic millimeters
of materlal per second of cutting time and per
millimeter of grinding wheel width) may be
manufactured.
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Brief Description of the Drawings
This ob~ect, and other ob~ects and advantages
of the present invention, will appear more clearly
from the following specification in con~unction
with the accompanying drawings, in which:
Fig. 1 i s a p e r s p e c t i v e
representation of a grinding
wheel;
Fig. 2 is an enlarged detail of the
working zone of a grinding
wheel with abrasive grinding
edges of a single file
arrangement;
Fig. 3 is a detailed view
corresponding to the
representation of Fig. 2
with abrasive grinding edges
of a three-file arrangement;
Fig. 4 is a further representation
of the working zone of a
grinding wheel with straight
and radial orientation of
the abrasive grain edges;
Fig. 5 is a representation
corresponding to Fig. 4 with
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an abrasive grinding edge
extending at an acuts angle
relative to the radius
orientation;
Fig. 6 is a further repreaentation
with an arc-shaped extension
of the abrasive grinding
edge: and
Fig. 7 shows a different
arrangement of an abrasive
grinding edge.
Summary of the Invention
The shaped grindlng tool of the present
invention is primarily comprised of a base body
having a working zone for producing the profile of
a work piece, and abrasive grains made of a highly
refractory material and galvanized to the working
zone in a single layer, the abrasive grains
forming grlnding edges spaced at a defined
distance from one another in the circumferential
direction of the grinding tool, the grinding edges
having a width that is less than 4 times a
diameter of an individual one of the abrasive
grains.
Due to the fact that in contrast to the known
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grinding tools segment-type grinding surfaces with
a plurality of ad~acently arranged abrasive grains
are no longer present, but a defined abrasive
grlnding edge made of a single file (row~ or up to
four rows of abrasive grains, it is ensured that
only effectively usable abrasive grains are
present at the surface of the base body. In front
of the abrasive grains, viewed in the
circumferential direction, a large free space is
now provided because no further abrasive grains
are galvanically bonded to the surface so that
thereby an optimal cutting process is possible.
The orientation of the abrasive grain
grinding edges, independent of the fact whether
there is a single file (row) abrasive grinding
edge or an abrasive grinding edge comprised of
four files, i.e., corresponding to four grain
diameters, is preferably straight in the radial
direction over the surface of the base body.
According to a further feature of the invention it
is also provided that the abrasive grinding edges
extent straight, but positioned at an acute angle
relative to a radial dlrection of the shaped
grinding tool.
On the other hand, it may be advantageous
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that the grinding edges are not straight but
curved, for example, corresponding to an arc-
shaped curve.
The distance between the individual abrasive
grain grinding edges in the circumferentlal
direction depends on the type of the workpiece
material to be ground, on the hardness of the
workpiece, and on the circumferential velocity
with which the grinding tool operates. Preferably
the distance between two grinding edges is
approximately 1.0 to 6.0 mm.
The highly refractory material to be used as
the abrasive grains is preferably diamond or CBN.
Descrlption of Preferred Embodiments
The present invention will now be described
in detail with the aid of several specific
embodiments utilizing Figures 1 through 7.
The shaped grinding tool is comprised of a
base body 1 which, at its working zone 2 used for
producing the workpiece profile, already exactly
conforms to the desired profile. The cutting
material, i.e., the abrasive grains are made of
dlamond, C8N or any other highly refractory
material which is galvanically bonded in the form
of abrasive grinding edges to the working zone 2
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of the base body 1. An abrasive grinding edge 3
is comprised of one or a plurality of grain rows,
see Figures 2 and 3. The distance x between two
adjacent grinding edges 3 is preferably 1.0 to 6.0
mm. The width b of a grinding edge 3 is smaller
than 4 times the diameter of the individual
abrasive grains.
The grinding edges 3 are usually radially
oriented (Figs. 2, 3 and 4); however, they may
also be arranged at an acute angle 4 relative to
the extension of the grinding tool radius (Fig.
5). In addition to a straight arrangement of the
grinding edges 3 an arc-shaped (Fig. 6) or an
arrangement on any other line (Fig. 7) is
possible.
By replacing the previous full-surface
coating of the working zone 2 of the base body 1
with grlnding edges 3 spaced at a defined distance
from one another, oriented grinding edges, that
are distributed over the circumference of the
grinding tool such as to conform to the particular
cutting process, and defined corresponding free
space~ are provided. The grlnding edges result in
an lmproved (better defined) cutting process. On
the one hand, the directly arranged free spaces
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prevent hydroplaning effects when using cutting
oils, and, on the other hand, provide for a more
efficient removal of the cuttings.
The present invention is, of course, in no
way restricted to the specific disclosure of the
specification and drawings, but also encompasses
any modifications within the scope of the appended
claims.
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