U.S. patent application number 11/364023 was filed with the patent office on 2006-09-21 for machining apparatus and method to machine surfaces in recesses of workpieces.
Invention is credited to Wolfgang Thiel.
Application Number | 20060211337 11/364023 |
Document ID | / |
Family ID | 36602466 |
Filed Date | 2006-09-21 |
United States Patent
Application |
20060211337 |
Kind Code |
A1 |
Thiel; Wolfgang |
September 21, 2006 |
Machining apparatus and method to machine surfaces in recesses of
workpieces
Abstract
In a machining apparatus to machine surfaces in recesses of
workpieces, especially tools with flutes and cutting edges, such as
twist drills, milling heads, reamers, and similar, the machining
apparatus has a circular disk-shaped or frustum-shaped machining
body with a symmetrical and rotational axis which is seated in a
bearing in a rotatable manner and is connected with a machining
drive to generate a rotational movement of the machining body about
its rotational axis. The machining body has magnets acting outward
in relation to the rotational axis to retain magnetic or
magnetizable, abrasive machining powder on a circumferential
surface of the machining body. A workpiece holder positionable
relative to the machining body and moveably driven at least in an
advancing or rotational direction or both is connected at least
indirectly by means of a corresponding positioning medium and
drives to the bearing of the machining body.
Inventors: |
Thiel; Wolfgang; (Emmetten,
CH) |
Correspondence
Address: |
SCHIFF HARDIN LLP;Patent Department
6600 Sears Tower
233 South Wacker Drive
Chicago
IL
60606
US
|
Family ID: |
36602466 |
Appl. No.: |
11/364023 |
Filed: |
February 28, 2006 |
Current U.S.
Class: |
451/11 ;
451/36 |
Current CPC
Class: |
B24B 1/005 20130101;
B24B 3/24 20130101 |
Class at
Publication: |
451/011 ;
451/036 |
International
Class: |
B24B 51/00 20060101
B24B051/00; B24B 1/00 20060101 B24B001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 1, 2005 |
DE |
10 2005 010 286.7 |
Claims
1. A machining apparatus to machine a surface in at least one
recess of a workpiece, comprising: a circular disk-shaped or
frustum-shaped machining body with a symmetrical and rotational
axis which is rotatably seated in a bearing and is connected to a
machining drive to generate a rotational motion of the machining
body about said rotational axis; the machining body having magnets
acting outwardly in relation to the rotational axis to retain
magnetic or magnetizable abrasive machining powder on a
circumferential surface of the machining body; and a workpiece
holder for said workpiece positionable relative to the machining
body and moveably driven in an advancing or rotational direction or
both and which is at least indirectly connected to the bearing of
the machining body by means of corresponding positioning media and
drives.
2. A machining apparatus according to claim 1 wherein the machining
body is constructed as a magnetic head in which the magnets are
formed from a plurality of permanent magnets to retain the
machining powder.
3. A machining apparatus according to claim 1 wherein the workpiece
holder has a feed drive and a rotation drive with which a workpiece
is to be simultaneously advanced and rotated, the feed drive and
the rotation drive being connected to a control unit constructed
such that advancing motion and rotational motion of the workpiece
are coordinated according to a path of said recess of the workpiece
to be machined.
4. A machining apparatus according to claim 3 wherein the workpiece
recess comprises a flute.
5. A machining apparatus according to claim 1 wherein the recess of
the workpiece comprises at least one of a flute or a cutting edge,
and wherein the workpiece comprises a twist drill, a milling head,
or a reamer.
6. A machining apparatus to machine a surface in at least one
recess of a workpiece, comprising: a circular machining body with a
symmetrical rotational axis which is mounted to a rotatable bearing
connected to a machining drive to generate a rotational motion of
the machining body about said rotational axis; the machining body
having a plurality of magnets at a peripheral region to retain
abrasive machining powder at a circumferential surface of the
machining body; and a workpiece holder for said workpiece
positionable relative to the machining body and moveably driven,
and the moveable driving being at least indirectly linked to
movement of the bearing of the machining body for synchronization
thereof.
7. A machining apparatus to machine a surface in at least one
recess of a workpiece, comprising: a circular machining body with a
symmetrical rotational axis which is mounted to a rotatable bearing
connected to a machining drive to generate a rotational motion of
the machining body about said rotational axis; the machining body
having a magnet system acting outwardly in relation to the
rotational axis to retain abrasive machining powder at a
circumferential surface of the machining body; and a workpiece
holder for said workpiece positionable relative to the machining
body and moveably driven, and the moveable driving being at least
indirectly linked to movement of the bearing of the machining body.
Description
BACKGROUND
[0001] The preferred embodiment relates to a machining apparatus
for machining surfaces in recesses of workpieces. In particular,
the machining apparatus serves to machine workpieces with flutes
and cutting edges, such as twist drills, milling heads, reamers and
similar. The machining apparatus has a machining body that is
constructed about a rotational axis in a rotation-symmetric manner.
To generate a rotational movement about its rotational axis, the
machining body is rotatably positioned on the one hand and
connected to a machining drive on the other. The machining body is
constructed as a magnetic head that has a plurality of magnets to
retain a magnetic or magnetizable, abrasive machining powder. In
addition, the preferred embodiment relates to a method for
de-burring and polishing surfaces of groove-shaped recesses of
workpieces, in particular cutting tools with flutes.
[0002] Specifically the de-burring of cutting edges and the
polishing of grooves of such cutting tools are significant since
such grooves serve to transport media such as coolants for
screw-type compressors or the carrying-away of machining chips for
cutting tools. Complete removal of residual burrs subsequent to the
groove's manufacturing process as well as a reduction of the
surface roughness decrease flow resistance or reduce friction. This
results in improved efficiency or an increase in the service life
of the workpieces or tools possessing grooves.
[0003] Known devices to de-burr and polish the flutes of cutting
tools for example are brush machines. However, the machining of
workpieces and tools with brush machines often and necessarily
results in the uncontrolled and undesired rounding off of cutting
edges. This is related to the fact that a part of the abrasive
brush hairs of a brush cluster are pressed against the cutting
edge. Rigid specifications pertaining to a precise geometry of the
cutting edge cannot be fulfilled in the case of machining with a
brush machine. Another disadvantage of such brush machines is that
the brushes wear in such a manner that the brushes must be
regularly replaced in a costly manner.
[0004] As an alternative to brushing, a jet procedure is known for
the de-burring of edges, whereby a high-pressure jet of fluid, such
as water, is generated. An abrasive effect of the jet can be
strengthened by mixing in abrasive materials of a particular
grain-size. Such a jet procedure has the disadvantage that the
expenses of generating the jet and reprocessing the material
required for the jet are high. An additional disadvantage is that
the workpieces must be treated in a sealed container. This prevents
the automatic supply and removal of workpieces. For a laminar
finish, for example the finish of a flute, the jet must be guided
to this surface by means of additional movements of the jet nozzle
or multiple jet nozzles must be provided and oriented precisely
amongst each other. In both cases, the device-related 2expenses are
considerable, especially when tools and workpieces of various
geometries must be machined using one system.
[0005] Another alternative to this known method is a
magnet-abrasive grinding method known from WO02/38334. WO02/38334
describes a machining device with a machining body that is capable
of binding a magnetizable, abrasive grinding powder as machining
powder by means of a plurality of permanent magnets and pole shoes
and to guide it over a surface to be machined. In the device known
from WO02/38334, the magnetizable grinding powder is retained by
the machining body by means of magnetic force, but due to its
coating thickness, it behaves like an elastic tool that acts upon
the surface to be machined. In doing so, the force exerted by the
machining powder on the respective workpiece surface can be
adjusted by means of the distance between the workpiece surface and
the magnets retaining the machining powder. In addition, the
intensity of the cutting exercised on the workpiece by the
machining powder can also be adjusted by the magnitude of the
relative movement between the magnets and the surface to be
machined.
SUMMARY
[0006] It is an object to create a machining apparatus that permits
the machining of recesses, such as grooves of workpieces or tools,
whereby the disadvantages of the prior art should be preferably
avoided.
[0007] A machining apparatus is provided to machine a surface in a
recess of a workpiece. A circular disk-shaped or frustrum-shaped
machining body is provided with a symmetrical and rotational axis
which is rotatably seated in a bearing and is connected to a
machining drive to generate a rotational motion of a machining body
about said rotational axis. The machining body has magnets acting
outwardly in relation to the rotational axis to retain magnetic or
magnetizable abrasive machining powder on a circumferential surface
of the machining body. A workpiece holder is provided for said
workpiece positionable relative to the machining body and moveably
driven in an advancing or rotation direction or both and which is
at least indirectly connected to the bearing of the machining body
by means of corresponding positioning media and drives.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a basic drawing of a rotation-symmetric machining
body with a circumferential frustum-shaped edge along with a view
of a workpiece, in the form of a twist drill, to be machined;
[0009] FIG. 2 depicts a robot-controlled tool whose spiral flute is
polished by a method of the preferred embodiment; and
[0010] FIG. 3 depicts a machining apparatus to polish the spiral
flute of highly magnetic tools.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0011] For the purposes of promoting an understanding of the
principles of the invention, reference will now be made to the
preferred embodiment illustrated in the drawings and specific
language will be used to describe the same. It will nevertheless be
understood that no limitation of the scope of the invention is
thereby intended, such alterations and further modifications in the
illustrated device, and/or method, and such further applications of
the principles of the invention as illustrated therein being
contemplated as would normally occur now or in the future to one
skilled in the art to which the invention relates.
[0012] According to the preferred embodiment a machining apparatus
is provided of a type described in the background, in which a
machining body is constructed as a rotation-symmetric magnetic
head, whose magnets are arranged in such a manner that they retain
the abrasive machining powder on the magnetic body's surface
oriented outward in relation to the rotational axis. The apparatus
according to the preferred embodiment also has a workpiece holder
that can be positioned relative to the machining body and that can
be driven in a moveable manner at least in an advancing or
rotational direction or both, said holder being connected at least
indirectly by means of a corresponding positioning medium and
drives to the bearing of the machining body. The workpiece holder
allows one to machine recesses in a workpiece, such as flutes of a
twist drill, with a single machining body over the entire length of
the respective groove.
[0013] The preferred embodiment is based upon the knowledge that
the machining body known from WO02/38334 is constructed as a
cylinder, in which the magnetic field retaining the machining
powder is generated on one of the faces, whereby this arrangement
is well suited for the machining of flat or convex surfaces, yet
not for surfaces in recesses of workpieces. Such recesses, like
grooves for example, can only be machined to the effective depth of
the magnetic field. This effective depth is limited by the magnetic
field strength which decreases with the square of the distance from
the magnet surface. In practice, this results in a usable effective
depth of 3 mm maximum. However, many workpieces and tools have
recesses, such as grooves for example, that are deeper and that can
therefore not be machined with the device known from WO02/38334.
For the first time, the machining apparatus according to the
preferred embodiment allows the machining of twist drills having
diameters greater than 12 mm, even though their flutes have a depth
that is greater than 3 mm. Thus, the machining apparatus according
to the preferred embodiment removes a limitation previously
considered as system-intrinsic in the field of utilization.
[0014] With this type of machining apparatus and due to the
magnetic attractive forces on the machining powder adhering
externally to the machining body as well as for corresponding
configurations, one can insert the corresponding magnets themselves
into the grooves to be machined of a workpiece. The insertion depth
of the machining body into the groove is selected in such a manner
that the distance between the machining surfaces of the magnetic
head and the surfaces to be machined in the groove is less than or
equal to 3 mm, whereby a sufficiently great field strength is
assured on the surfaces to be machined, which is a prerequisite for
the abrasive work of the grinding powder.
[0015] In order to be able to machine a groove in its entire
length, the respective workpiece is run past the machining body
with the help of the corresponding moveable workpiece holder. The
guiding of the workpiece occurs preferably in such a way that the
local orientation of the helix-like, coiled flute of a twist drill
at the machining location matches the respective effective tangents
of the machining body at least approximately. This allows the
machining of a flute in which the cutting edges are not impaired
and permits a preferably deep insertion of the machining body into
the flute. If a workpiece, such as a twist drill has several
grooves, then these grooves can be machined one at a time
sequentially or multiple machining heads can be provided that
engage simultaneously with various grooves.
[0016] Specifically in relation to the machining of a twist drill's
flutes for example, an advantageous machining apparatus is one in
which the workpiece holder has a feed drive and a rotation drive
with which the workpiece can be simultaneously fed and rotated,
whereby the feed drive and rotation drive are connected to a
control unit designed in such a way that the workpiece feed and
workpiece rotation are inter-coordinated. In reference to the
machining of a twist drill, this means that the twist drill is
arranged by means of the workpiece holder's positioning medium in
such a manner that the tangents of the machining body at the
respective machining point run parallel to the longitudinal axis of
the flute to be machined. The feed drive allows one to move the
workpiece, the twist drill for example, along the workpiece's
longitudinal axis. In the case of twist drills with helix-like,
coiled flutes, this linear advancing motion must be given a
rotational motion of the workpiece that is coordinated with the
advancing motion in such a manner that the resulting overall
movement corresponds to the pitch of the flute.
[0017] The relative motion between the machining body and workpiece
thus results from the rotational movement of the machining body and
the movement of the workpiece specified by the feed drive or
rotation drive or both. The feed drive thereby causes a linear
movement of the workpiece, while the rotation drive causes a
rotational movement of the workpiece. In the case of those grooves
that run parallel to a longitudinal axis of a workpiece, only a
linear feed movement is required. To machine other workpieces that
have a circumferential, enclosed groove on a surface area, whereby
the groove runs in a plane perpendicular to a symmetrical axis of
the workpiece, the workpiece holder must only execute one
rotational movement effected by the rotation drive in order to
machine the groove of the workpiece over the entire circumference
of the workpiece. Examples of such workpieces are crankshafts whose
bearing points are to be polished between the crank cheeks. In this
case, the machining body enters between the crank cheeks until the
machining distance to the bearing surface is 3 mm or less. The
crankshaft then executes a rotational movement about its
longitudinal axis. In doing so, the rotational axis of the
machining body is preferentially oriented parallel to the
rotational axis of the crankshaft.
[0018] As already mentioned, workpieces with a helix-like, coiled
groove, such as twist drills for example, require a synchronized
movement both in the feed direction (linear movement) and in the
rotational direction (rotational movement).
[0019] A circular disk shape has proven itself to be a particularly
advantageous shaping for the machining body, whereby magnets are
arranged on the circumference of the circular disk. In addition,
the design of the magnetic head as a frustum is especially
advantageous for working on relatively small grooves, whereby a
circumferential edge on the cone's base is rounded off and equipped
with magnets.
[0020] FIG. 1 depicts a rotation-symmetrical machining body 14 with
a circumferential frustum-shaped edge 13 of a machining apparatus
otherwise not further depicted. The machining body 14, also called
a magnetic head, has on its edge a plurality of not further
depicted magnets. As can be seen in FIG. 1, the frustum-shaped edge
13 of the machining body 14 is rounded off, so that it
approximately copies the form of flute 12 of the twist drill 11 to
be machined. A magnetic, abrasive grinding powder not depicted in
this figure adheres to the magnets. When the frustum-shaped edge 13
is inserted into flute 12, the remaining space is filled by this
grinding powder. A machining drive to drive the machining body 14
about its rotational axis 15 is not further depicted.
[0021] The workpiece depicted in FIG. 1 is a twist drill 11, whose
flute 12 is to be machined. To do so, the workpiece 11 (the twist
drill) is fastened to a workpiece holder that, on the one hand, is
to be oriented with the help of a positioning medium, not shown in
further detail in this figure, relative to the rotational axis 15
of the machining body 14, and, on the other, is connected to a feed
drive and a rotation drive that enable an advancing movement in the
longitudinal direction of the workpiece and a rotational movement
about a rotational axis of the workpiece.
[0022] As can be seen in FIG. 1, the workpiece 11 is arranged in
such a manner that a tangent abutting the frustum-shaped edge 13
and the rotational axis of the twist drill 11 to be machined form
an angle in such a manner that at the machining location, the edge
runs through flute 12 in a collision-free manner. This angle
corresponds to the so-called pitch of the twist drill and must be
set for each drill-type. The gaps to be set between the edge
inserted into the flute and the surface of the flute should
preferentially be between 1-2 mm.
[0023] To machine the flute 12, the machining body 14 is placed
into a rotational motion about the rotational axis 15. This
rotational motion has the greatest share of the relative motion
between the twist drill 11 and the abrasive machining powder, said
motion being required to machine the flute. The machining powder
(not depicted in FIG. 1) is retained outside on the edge 13 of the
machining body 14 by the magnets of the machining body and pulled
along by its rotation. It thereby performs abrasive work in the
flute with the objective of reducing roughness.
[0024] In order to machine the flute 22 over its entire length, the
workpiece holder not depicted in this figure executes during the
machining process both an advancing motion along the workpiece's
rotational axis as well as a rotational motion around this
rotational axis. This linear advancing motion and the rotational
motion are synchronized with each other in such a manner that the
edge 13 of the machining body 14 along with its tangent always runs
approximately centered in flute 12. This means that the advancing
motion and the rotational motion of the workpiece are synchronized
or coordinated to correspond to the pitch of the flute 12.
[0025] Two particularly advantageous apparatuses with which a tool
having a spiral-shaped flute can be polished are explained
below.
[0026] FIG. 2 depicts the implementation of an industrial robot 27
to guide the tool 25 to be machined along the machining edge of a
magnetic head 23. The objective is to polish the spiral flute of
the cutting tool 25 by means of the magnetic grinding powder
adhering to the circumferential edge 24. The grippers 26 of the
robot 27 extract from a non-depicted stack the cutting tool 25 to
be machined. It may be a milling cutter, a tap, or a drill twist,
for example. This tool is positioned on the circumferential
machining edge 24 of the rotating magnetic head 23 in the manner
already described for FIG. 1. The robot is programmed in such a
manner that it executes an advancing motion in the direction of the
tip of tool 25, which is synchronized according to the pitch of the
tool with a rotational motion of the tool about its rotational
axis. In this manner, the entire length of the flute is polished by
the powder adhering to the machining edge 24 of the rotating
magnetic head 23. The rotating magnetic head 23 is driven by means
of a three-phase AC motor 21 and a coupling 22. A dish 29 catches
removed chips from the machined tools. The depicted embodiment is
especially suited for metal carbide tools. These are only weakly
magnetic and therefore the magnetic attractive forces exercised by
the magnetic head 23 on the tool and thus the robot's grippers are
slight.
[0027] FIG. 3 depicts the implementation of the procedure according
to the preferred embodiment in polishing the spiral flute of a tool
by means of controlled translational and rotational axes.
Especially in the machining of highly magnetic materials, such as
HSS steel, the occurring magnetic forces can be too great for robot
applications, which were described above by means of FIG. 2. In
these cases, it is more advantageous to have the acting forces be
absorbed by correspondingly arranged, controllable axes. The
rotating magnetic head 33 is driven by a three-phase AC motor 31.
This set-up is positioned on a turntable 39, by means of which the
angle between the tangent abutting the circumference of the
magnetic head 33 and the rotational axis of the tool 35 can be
adjusted. The tool 35 to be machined is positioned in a seat and is
driven by a servomotor 32, which is controlled by a programmable
controller. This set-up is situated on two guides offset 90 degrees
to each other, which permit the manual positioning of the tool
using the adjustment wheels 38 and 37 in such a manner that the tip
of the tool's flute is located in engagement with the
circumferential edge of the magnetic head 33. The mentioned manual
guides are connected to a guide 34 oriented parallel to the tool
axis. The guide 34 is driven by a non-depicted servomotor. Finally,
one controls from the programmable controller in such a manner that
its translational motion occurs synchronously with the rotation of
the tool 35. The servomotor 35 responsible for the tool rotation
and the servomotor responsible for the advancing motion of the tool
both receive the control pulses from the same programmable
controller, whereby a common start time and synchronization of the
motions are assured.
[0028] While the invention has been illustrated and described in
detail in the drawings in the above description, the same is to be
considered as illustrative and not restrictive in character, it
being understood that only the preferred embodiment has been shown
and described and that all changes and modifications that come
within the scope of the invention are desired to be protected.
* * * * *