U.S. patent application number 10/799657 was filed with the patent office on 2004-09-09 for friction stir welding apparatus and method and processing apparatus and method.
Invention is credited to Doi, Masayuki, Hirano, Satoshi, Inagaki, Masahisa, Odakura, Tomio, Okamoto, Kazutaka, Okamura, Hisanori, Tomobe, Masaru.
Application Number | 20040173663 10/799657 |
Document ID | / |
Family ID | 19101124 |
Filed Date | 2004-09-09 |
United States Patent
Application |
20040173663 |
Kind Code |
A1 |
Okamoto, Kazutaka ; et
al. |
September 9, 2004 |
Friction stir welding apparatus and method and processing apparatus
and method
Abstract
The invention provides a friction stir welding apparatus and
method and a processing apparatus and method, which are not easily
affected by deformations of a work being processed. The friction
stir welding apparatus inserts a rotating tool into the work and
moves the rotating tool relative to the work to join members of the
work. The friction stir welding apparatus and method and the
processing apparatus and method of the invention, the latter
cutting or grinding the work with a rotating cutter or grindstone,
comprises controlling a relative distance between the tool, cutter
or grindstone and the work under the joining or processing
operation or an insertion depth so that the load factor or electric
current of a spindle motor for rotating the tool, cutter or
grindstone is within a predetermined range, and a controller
therefor.
Inventors: |
Okamoto, Kazutaka; (Hitachi,
JP) ; Hirano, Satoshi; (Hitachi, JP) ; Doi,
Masayuki; (Hitachinaka, JP) ; Okamura, Hisanori;
(Tokai, JP) ; Inagaki, Masahisa; (Hitachi, JP)
; Odakura, Tomio; (Hitachi, JP) ; Tomobe,
Masaru; (Hitachi, JP) |
Correspondence
Address: |
ANTONELLI, TERRY, STOUT & KRAUS, LLP
1300 NORTH SEVENTEENTH STREET
SUITE 1800
ARLINGTON
VA
22209-9889
US
|
Family ID: |
19101124 |
Appl. No.: |
10/799657 |
Filed: |
March 15, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10799657 |
Mar 15, 2004 |
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10100093 |
Mar 19, 2002 |
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6729526 |
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Current U.S.
Class: |
228/112.1 ;
228/2.1 |
Current CPC
Class: |
B23K 20/123
20130101 |
Class at
Publication: |
228/112.1 ;
228/002.1 |
International
Class: |
B23K 020/12 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 12, 2001 |
JP |
2001-276419 |
Claims
What is claimed is:
1. A friction stir welding apparatus for joining members of a work
by inserting a rotating tool into the work and moving the rotating
tool relative to the work, comprising a controller for controlling
a relative distance in a tool insertion direction between the tool
and the work or an insertion depth of the tool into the work so
that a load factor or electric current of a spindle motor for
rotating the tool is within a predetermined range.
2. A friction stir welding apparatus according to claim 1, further
comprising a laser displacement meter or a contact type
displacement meter for detecting the relative distance in a tool
insertion direction between the tool and the work during the
joining operation or the insertion depth of the tool into the work,
the detected values being reflected on the controller.
3. A friction stir welding apparatus for joining members of a work
by inserting a rotating tool, rotated by a spindle motor, into the
work and moving the rotating tool relative to the work, comprising
a controller for controlling a relative distance in a tool
insertion direction between the tool and the work or an insertion
depth of the tool into the work so that a load factor or electric
current of the spindle motor is within a predetermined range.
4. A friction stir welding apparatus according to claim 3, further
comprising a laser displacement meter or a contact type
displacement meter for detecting the relative distance in a tool
insertion direction between the tool and the work during the
joining operation or the insertion depth of the tool into the work,
the detected values being reflected on the controller.
5. A friction stir welding method of joining members of a work by
inserting a rotating tool into the work and moving the rotating
tool relative to the work, comprising the step of controlling a
relative distance in a tool insertion direction between the tool
and the work during the joining operation or an insertion depth of
the tool into the work so that a load factor or electric current of
a spindle motor for rotating the tool is within a predetermined
range.
6. A friction stir welding method according to claim 5, wherein the
relative distance in a tool insertion direction between the tool
and the work during the joining operation or the insertion depth of
the tool into the work is detected by a laser displacement meter or
a contact type displacement meter, and the detected values are
reflected on the controller.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a novel friction stir
welding apparatus and method and a novel processing apparatus and
method, both of which keep constant a relative distance between a
tool, cutter or grindstone and a work to be welded or processed
during friction stir welding, cutting or grinding.
[0002] The friction stir welding is a method that can join members
of a work of such materials as aluminum and aluminum alloys (simply
referred to as aluminum hereinafter), magnesium and magnesium
alloys (simply referred to as magnesium hereinafter), copper and
copper alloys (simply referred to as copper hereinafter), titanium
and titanium alloys (simply referred to as titanium hereinafter),
and iron or steel (simply referred to as iron hereinafter) in solid
phase at temperatures below their melting points. More
specifically, this is the method of inserting a tool, essentially
harder than the work to be welded, into the work while rotating the
tool, and moving the rotating tool relative to the work to utilize
frictional heat generated between the tool and the work as well as
a resulting plastic flow and join members of the work together.
This method has been known by JP-07-505090A. That is, the method
takes advantage of a plastic flow caused by frictional heat between
the tool and the work and, unlike conventional welding such as arc
welding and electron beam welding, does not melt the work during
the process of welding.
[0003] Further, unlike the conventional friction welding method in
which members to be processed are rotated against each other and
joined together by frictional heat produced by the relative
rotation, the friction stir welding method can continuously join
the members of the work along a joint line longitudinally at a
temperature below the melting point of the material. The joint line
may be not only a straight line but also a curve or a
three-dimensional curve.
[0004] FIG. 2 is a sectional view schematically showing a joining
state in the friction stir welding. A hard tool 10 comprising a
shoulder 11 and a pin 12 is rotated by a spindle motor not shown. A
revolution speed, which depends on the material and shape of the
work to be joined, is set at around 1,000 rpm. The tool 10 is then
inserted into the work a predetermined depth from the surface 13 of
the work and is moved relative to the work in a direction of joint
14. A speed of movement, which also depends on the material of the
work to be joined, is about 500 mm/min. It is noted here that the
tool 10 is tilted at a predetermined angle .theta. to the work
toward the rear side with respect to the direction of movement. In
the friction stir welding, the quality of joint is affected by the
shape of the tool, the revolution speed, the speed of tool
movement, and others. It is current practice that these factors are
optimized based on user's knowhow. The most important one among the
factors to be optimized is a distance or depth by which the tool 10
is inserted into the work.
[0005] FIG. 3 is a sectional view schematically showing a joining
state in the friction stir welding when the distance for which the
tool 10 is inserted into the work is set slightly deeper as
compared with that of FIG. 2. The insertion depth of the tool 10 in
the range between those of FIG. 2 and FIG. 3 results in a
satisfactory joint quality. When the depth of insertion of the tool
10 into the work is set larger than that of FIG. 3, the shoulder 11
on the moving direction 14 side of the tool 10 sinks into the
surface 13 of the work, thereby cutting the work with the side
surface of the tool 10. In this case, the surface 13 of that
portion of the work which has undergone the joining operation is
recessed significantly from the remaining portion, and the material
excessively cut off is discharged outside as burrs. Conversely,
when the depth of insertion of the tool 10 into the work is set
smaller than that of FIG. 2, the shoulder 11 on the side opposite
the moving direction 14 of the tool 10 parts from the surface 13 of
the work, reducing the effect of holding down the material stirred
by the pin 12, with the result that the work is cut by the pin 12.
The material of the work thus cut is discharged outside as
burrs.
[0006] Hence, keeping the tool insertion depth into the work at an
appropriate amount during the joining operation leads to an
improvement of the quality of the joint. The insertion depth of the
tool 10 into the work depends on a variety of factors, for example,
a machining precision of the work, a method of holding the work and
a precision of the joining apparatus itself. Establishing these
factors within a precision of about 0.05 mm is very difficult to
achieve with the current level of technology. Although a desired
machining precision may be realized by investing a sufficient time
and cost, this leads to an increase in the overall manufacturing
cost and is practically difficult to realize.
[0007] To deal with such a problem, JP-11-226768A, for instance,
shows a method of controlling the insertion depth of the tool 10
into the work to be joined, which uses a laser displacement meter.
FIG. 4 is a sectional view showing an example construction of the
joining apparatus. In this apparatus a table 27 is moved in the
direction of X by a drive motor 21. On the table 27, a work 26 to
be joined is securely held by a jig not shown. A machine head 25 is
moved in the direction of Z by a head drive motor 22. The machine
head 25-is supported by a ball thread 29 and a guide not shown. The
machine head 25 has mounted thereon a tool 24 and a spindle motor
23 that drives the tool 24. The distance between the machine head
25 and the surface 30 of the work to be joined is measured by the
laser displacement meter 28 mounted on the machine head 25. The
distance measured is fed back and the head drive motor 22 is
controlled to adjust the position of the machine head 25 so that
the distance between the machine head 25 and the surface 30 of the
work is kept at a predetermined value at all times.
[0008] The position control using such a laser displacement meter
is a common measure also in the conventional arc welding and laser
welding. It is common to perform the distance measurement by the
laser displacement meter at a position offset to and slightly ahead
of the tool. Thus, the distance between the machine head and the
tool at the measuring position of the laser displacement meter may
slightly differ from that measured near the tool. In the case of
the friction stir welding, the work to be joined is acted upon by a
force of about 1000 kgf from the tool. A problem therefore arises,
for example, when a part of the work is slightly floated from the
table. The laser displacement meter beforehand reads this flowing
and controls the machine head to raise it upward according to the
measurement. When the tool passes the floating position, the work
is moved down by the force of the tool, increasing the distance
between the tool and the work to slightly more than an appropriate
distance. Further, it should be noted that the laser displacement
meter is designed to detect the state of the surface (surface
position). The meter thus tends to be subject to influences from,
for instance, a change in radiation factor caused by smear of the
surface of the work or by oxidation of the work due to frictional
heat.
[0009] JP-06-143015A teaches, in a cutting machine that performs
cutting while rotating a cutting tool by a main motor, adjusting a
feed speed of the cutting tool to keep an electric current of the
main motor at a predetermined value. But this reference does not
show any particular relationship of the feed speed with the
friction stir welding.
[0010] JP-11-188517A discloses that, in a cutting machine that
performs cutting by rotating a cutting tool by a main motor, means
is provided for stopping feed means according to an amount of load
detected by the feed means. However, this reference is silent about
any particular relationship of the feed means in the friction stir
welding.
BRIEF SUMMARY OF THE INVENTION
[0011] An object of the present invention is to provide a friction
stir welding apparatus and method and a processing apparatus and
method, both of which are not easily affected by deformations of a
work being processed.
[0012] The present invention features, in an aspect thereof, a
friction stir welding apparatus which joins members of a work by
inserting a rotating tool into the work and moving the rotating
tool relative to the work, comprising a controller for controlling
a relative distance in a tool insertion direction between the tool
and the work during the joining operation or an insertion depth of
the tool into the work so that a load or electric current of a
spindle motor for rotating the tool is within a predetermined
range.
[0013] The invention resides also in a friction stir welding method
which features joining members of a work while controlling a
relative distance in a tool insertion direction between the tool
and the work during the joining operation or an insertion depth of
the tool into the work so that a load or electric current of a
spindle motor for rotating the tool is within a predetermined
range.
[0014] The friction stir welding is a technique which is very
simple in principle and can provide an excellent joint
characteristic. This technique, however, requires controlling the
relative distance between the tool and the work with a precision of
about 0.05 mm at all times. This invention focuses on a heat
balance in the friction stir welding. In the friction stir welding,
a work done by the spindle motor in rotating the tool 10
constitutes a heat source.
[0015] FIG. 5 shows contact areas 31, 32 between the tool 10 and
the work in the states of FIG. 2 and FIG. 3, respectively. As shown
in FIG. 2 and FIG. 3, since the tool 10 is tilted at a
predetermined angle .theta. to the work toward the rear side with
respect to the moving direction, the contact areas 31, 32 depend on
the depth of insertion of the tool 10 into the work. As described
above, the work done by the spindle motor is transformed into
frictional heat generated between the tool 10 and the work. When
the revolution speed of the spindle motor is kept constant, the
frictional heat generated depends on the contact area. The
frictional heat diffuses into the work being processed. This heat
raises the temperature of the work and thereby softens it, with the
result that the work is stirred by the tool 10. When the contact
area is large, the amount of frictional heat produced is large, and
when the contact area is small, the amount of frictional heat is
small. Therefore, to ensure a stable joining operation at all times
requires stabilizing the stirring of the work by the tool 10. That
is, the load or electric current of the spindle motor, which
constitutes the work done by the spindle motor or the heat source,
needs to be stabilized at all times.
[0016] FIG. 6 schematically shows a relationship between a tool
insertion depth and a spindle motor load (=work done by the spindle
motor). In the friction stir welding, the joint quality is
influenced by the tool insertion depth, and an appropriate tool
insertion depth lies in a certain range. If the revolution speed of
the spindle motor is constant, there is an appropriate range of the
spindle load corresponding to an appropriate value of the tool
insertion depth.
[0017] The invention features, in another aspect, in a friction
stir welding apparatus which joins members of a work by inserting a
rotating tool into the work and moving the rotating tool relative
to the work, controlling a relative distance between the tool and
the work during the joining operation so that a load of the tool
rotating spindle motor is within a predetermined range. The
relative distance between the tool and the work may be set by using
the head drive motor 22 of FIG. 4, for example. The load of the
spindle motor may be electrically detected, for example, from the
spindle motor 23 of FIG. 4, and it is preferable to perform the
detection by using an electric current.
[0018] A laser displacement meter or contact type displacement
meter that has conventionally been used may also be used
additionally to detect the relative distance between the tool and
the work or the amount of insertion of the tool into the work
during the joining operation. The load of the spindle motor depends
on a temperature of the members of the work immediately before
being joined together. For a work made of aluminum or copper which
has a good heat conductivity, for example, if the joining speed is
significantly low, the frictional heat generated between the tool
and the work may be diffused, though very rarely, forward in the
direction of tool advancement. When a temperature rise of the work
in front of the tool caused by the diffused heat is more than about
50.degree. C., the strength of the work in front of the tool (for
example, resistance to deformation at that temperature)
deteriorates. Thus, if a work done by the spindle motor is
constant, an excessive work is produced considering preheating due
to the heat diffusion. Therefore, a laser displacement meter may be
used as an auxiliary means. If the work to be processed has a shape
consisting of an arbitrary curved surface, a line normal to an
arbitrary curved surface may be detected by using the laser
displacement meter.
[0019] The invention further features, in another aspect, in a
friction stir welding method of joining members of a work by
inserting a rotating tool into the work and moving the rotating
tool relative to the work, comprising the steps of rotating the
tool at a constant speed while inserting the rotating tool into the
work at a constant insertion speed, when a predetermined load ratio
or factor of a spindle motor relative to a maximum output for
rotation of the tool or a predetermined insertion depth of the tool
into the work is reached, holding the rotating tool where it is for
a predetermined duration, then moving the rotating tool in a
joining direction at a constant joining speed to perform joining,
and at the same time with the tool movement, controlling a relative
distance in a tool insertion direction between the tool and the
work during the joining operation or an insertion depth of the tool
into the work so that a load factor or electric current of the
spindle motor for rotating the tool is within a predetermined
range.
[0020] The invention features, in still another aspect, in a
friction stir welding apparatus which joins members of a work by
inserting a rotating tool, rotated by a spindle motor, into the
work and moving the rotating tool relative to the work, comprising
revolution speed setting means for setting a revolution speed of
the tool, insertion speed setting means for setting a constant
insertion speed at which the tool rotating at a constant revolution
speed is inserted into the work, load factor setting means for
setting a load factor of the spindle motor relative to a maximum
tool rotation output or an insertion depth setting means for
setting an insertion depth into the work, hold time setting means
for setting a hold time during which the tool is held where it is
when the load factor or insertion depth reaches the set value,
joining speed setting means for setting a constant joining speed at
which the tool is moved in a joining direction to join the members
of the work, and a controller for controlling a relative distance
in a tool insertion direction between the tool and the work during
the joining operation or an insertion depth of the tool into the
work so that a load factor or electric current of the spindle motor
for rotating the tool is within a predetermined range.
[0021] The invention features, in still another aspect, in a
processing apparatus or method which cuts or grinds a work by
moving a rotating cutter or grindstone relative to the work,
comprising a controller for controlling a relative distance in a
cutter or grindstone insertion direction between the cutter or
grindstone and the work during the processing operation or an
insertion depth of the cutter or grindstone into the work so that a
load factor or electric current of a spindle motor for rotating the
cutter or grindstone is within a predetermined range.
[0022] Further, the invention can also be applied similarly to a
processing apparatus which cuts or grinds a work by inserting a
rotating cutter or grindstone, rotated by a spindle motor, into a
work by a head drive unit and moving the cutter or grindstone
relative to the work.
[0023] The invention further features, in a further aspect, in a
processing apparatus which cuts or grinds a work by inserting a
rotating cutter or grindstone, rotated by a spindle motor, into a
work by a head drive unit and moving the cutter or grindstone
relative to the work, comprising revolution speed setting means for
setting a revolution speed of the cutter or grindstone, insertion
speed setting means for setting a constant insertion speed at which
the cutter or grindstone rotating at a constant revolution speed is
inserted into the work, load factor setting means for setting a
load factor of the spindle motor relative to a maximum cutter or
grindstone rotation output or an insertion depth setting means for
setting an insertion depth into the work, processing speed setting
means for setting a constant processing speed at which the cutter
or grindstone is moved in a processing direction to process the
work, and a controller for controlling a relative distance in a
cutter or grindstone insertion direction between the cutter or
grindstone and the work during the processing operation or an
insertion depth of the cutter or grindstone into the work so that a
load factor or electric current of the spindle motor for rotating
the cutter or grindstone is within a predetermined range.
[0024] The invention features in a further aspect, in a processing
method which cuts or grinds a work by moving a rotating cutter or
grindstone relative to the work, comprising the step of controlling
a relative distance in a cutter or grindstone insertion direction
between the cutter or grindstone and the work during the processing
operation or an insertion depth of the cutter or grindstone into
the work so that a load of a spindle motor for rotating the cutter
or grindstone is within a predetermined range.
[0025] The invention features, in a further aspect, in a processing
method which cuts or grinds a work by moving a rotating cutter or
grindstone relative to the work, comprising the steps of inserting
the cutter or grindstone rotating at a constant revolution speed
into the work at a constant insertion speed, after a predetermined
load factor of a spindle motor relative to a maximum cutter or
grindstone rotation output or a predetermined insertion depth into
the work is reached, moving the cutter or grindstone in a
processing direction to process the work, and at the same time with
the movement, controlling a relative distance in a cutter or
grindstone insertion direction between the cutter or grindstone and
the work during the processing operation or an insertion depth of
the cutter or grindstone into the work so that a load factor or
electric current of the spindle motor for rotating the cutter or
grindstone is within a predetermined range.
[0026] Other objects, features and advantages of the invention will
become apparent from the following description of the embodiments
of the invention taken in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0027] FIG. 1 is a block diagram showing the concept of a
controller for the friction stir welding apparatus of the
invention.
[0028] FIG. 2 is an enlarged section view showing the detail of a
tool in the friction stir welding.
[0029] FIG. 3 is an enlarged section view showing the detail of a
tool in the friction stir welding.
[0030] FIG. 4 is a sectional view of the friction stir welding
apparatus in which a control on the tool insertion depth is
additionally made by using a laser displacement meter.
[0031] FIG. 5 is a plan view showing contact areas between the tool
and members of the work to be joined in the case of FIG. 2 and FIG.
3.
[0032] FIG. 6 is a diagram showing a basic concept of the
invention, i.e., a relation between the tool insertion depth and
the spindle motor load.
[0033] FIG. 7 is a sectional view of the friction stir welding
apparatus of the invention.
[0034] FIG. 8 is a diagram showing changes over time of a control
command value, a work deformation and a spindle motor load factor
in the friction stir welding apparatus of the invention.
[0035] FIG. 9 is an external view of members joined together by the
friction stir welding of the invention.
DETAILED DESCRIPTION OF THE INVENTION
EMBODIMENT 1
[0036] FIG. 1 is a block diagram of the friction stir welding
apparatus showing the concept of a relative position control on a
tool and a work according to the invention. FIG. 7 is a cross
section of the friction stir welding apparatus with the controller
of FIG. 1. In FIG. 1, an NC controller sets a spindle motor for
rotating the tool and a head drive motor for inserting the tool
into the work to predetermined load factors, and with the input of
a revolution speed of the tool and a joining speed, joining is
performed automatically. A programmable controller (PMC) monitors
the load factor of the spindle motor and performs a feedback
control on the tool insertion depth.
[0037] That is, the NC controller and the PMC controller have
revolution speed setting means for setting a revolution speed of
the tool, insertion speed setting means for setting a constant
speed at which the tool is inserted into the work while the tool is
rotated at a constant speed, load factor setting means for setting
a load factor of the spindle motor relative to the maximum tool
rotation output or an insertion depth setting means for setting an
insertion depth into the work, hold time setting means for setting
a time duration for which the tool is held when the load factor or
insertion depth reaches the preset value, and joining speed setting
means for setting a joining speed at which the tool is moved in the
joining direction to join members of the work. Further, these
controllers control the relative distance in the tool insertion
direction between the tool and the work during the joining
operation or the insertion depth of the tool into the work so that
the load factor or electric current of the spindle motor falls in a
predetermined range.
[0038] FIG. 7 shows an apparatus of a type that is controlled by
the controller of FIG. 1 and moves the table 27 left and right by
the table drive motor 21 to form a linear joint in the X-axis
direction. The work 26 is held on the table 27 by a jig not shown.
The work 26 comprises two members made of aluminum, each measuring
2000 mm long by 150 mm wide by 5 mm thick, and these two members
are placed in contact side by side in a direction perpendicular to
the plane of the sheet. An iron plate 40 2 mm thick is interposed
at the center between the two members of the work to verify the
function of this invention. As a result, the work 26 to be joined
rises about 2 mm at almost the central portion with respect to the
longitudinal direction.
[0039] The tool 24 is made from tool steel and has a shoulder
diameter of 13 mm, a pin diameter of 6 mm and a pin length of 4.0
mm. The spindle motor 23 for rotating the tool 24 has an output of
5 kW. The machine head 25 mounting the tool 24 and the spindle
motor 23 is supported by the ball thread 29 and moved in the Z
direction by a head drive motor 27. These motors are controlled by
the NC controller and the PMC controller not shown.
[0040] FIG. 8 shows changes over time of a spindle motor load ratio
or factor and a distance traveled by the machine head during
operation. First, the tool 24 is rested 5 mm above the surface 30
of the work 26. The spindle motor 23 is operated at 1000 rpm and
the head drive motor 22 is also started to lower the machine head
25 at the rate of 5 mm/min. The lowering of the machine head 25 is
controlled so as to stop the lowering of the tool 24 when the
distance traveled by the machine head 25 reaches 9.6 mm (=5.0+4.6
mm) or the load factor of the spindle motor 23 (percentage of the
current output with respect to the maximum output) is 73%.
[0041] At time (1) of FIG. 8, the spindle motor load factor was 73%
and the machine head 25 was stopped. The position of the machine
head 25 in this state was taken as a reference of a control command
value (=0 mm). The tool 24 was held there for 20 seconds while
rotating at a constant speed. At this time, the spindle motor load
factor slightly decreased but was not reflected on the control.
After the tool was held for 20 seconds, the table drive motor 21
was started to move the work 26 relative to the tool 24 in the
joining direction of X ((2) of FIG. 8). The table moving speed at
this time was 400 mm/min. At the same time when starting the
movement in the X direction, the machine head 25 was controlled
vertically by the head drive motor 22 so that the load factor of
the spindle motor 23 would be 68-71%. When the spindle motor load
factor steps out of the band described above, the machine head 25
has to be moved up or down at the speed of 6 mm/min. An almost
central portion of the work 26 rises up about 2 mm. This concave
configuration of the work 26 is also shown in FIG. 8.
[0042] At time (3) of FIG. 8, the process reaches the apex of the
convex of the work. FIG. 8 clearly shows that the distance traveled
by the machine head (control command value) perfectly follows the
shape (deformation) of the work. The joining conditions and control
parameters described above are input through the NC controller, and
a human interface is required only for input of the parameters into
the NC device.
[0043] FIG. 9 compares an external view of a joint bead obtained by
performing the tool insertion depth control described above and an
external view of a joint bead obtained with no tool insertion depth
control and by keeping the machine head 25 at the same position.
The position of the apex of the convex as shown in FIG. 8 is
indicated by the same reference numeral (3). As shown in FIG. 9,
when the control is performed, the bead quality is stable, and on
the other hand, when the control is not performed, the tool cuts
into the work significantly at around (3), producing a substantial
amount of burrs, as seen in the lower part of FIG. 9.
[0044] As described above, it is clear that performing the control
on the relative distance between the tool and the work or on the
tool insertion depth of the invention can produce an improved joint
quality with no burrs and little depression. The invention can be
implemented basically with a relatively simple apparatus by adding
software to the existing NC controller.
EMBODIMENT 2
[0045] The processing apparatus of this embodiment is used on a
precision processing apparatus such as a surface polisher, in which
the invention is applied in place of the tool of the Embodiment 1,
and performs rotation of a grindstone, its insertion into the work
being polished and its movement in the processing direction in a
way similar to the Embodiment 1. Further, the processing apparatus
has a head drive device with a controller for controlling a
relative distance between the grindstone and the work being
polished or an insertion depth of the grindstone into the work so
that the load factor or electric current of a spindle motor falls
in a preset range, as in the Embodiment 1.
[0046] More specifically, the processing apparatus with the
controller includes revolution speed setting means for setting a
revolution speed of a grindstone, insertion speed setting means for
setting a constant speed at which the grindstone is inserted into
the work while the grindstone is rotated at a constant speed, load
factor setting means for setting a load factor of the spindle motor
relative to the maximum grindstone rotation output or an insertion
depth setting means for setting an insertion depth into the work,
processing speed setting means for setting a processing speed at
which the grindstone is moved in the processing direction to
process the work, and the controller for controlling the relative
distance in the grindstone insertion direction between the
grindstone and the work during operation or the insertion depth of
the grindstone into the work so that the load factor or electric
current of the spindle motor falls in a predetermined range.
[0047] With this construction, it is possible to keep the load
factor or electric current of the spindle motor for the grindstone
within a preset range at all times, thus allowing apparently smooth
polishing. This embodiment is particularly advantageous for
application to a mirror surface polisher with a curved surface.
[0048] According to the invention, the tool insertion depth into
the work, the most important factor in the joint quality management
of the friction stir welding, can be kept constant at all times,
achieving significant advantages of enabling a high precision
control and automation of the joining apparatus.
[0049] It will be further understood by those skilled in the art
that the foregoing description has been made on the embodiments of
the invention and that various changes and modifications may be
made in the invention without departing from the sprit of the
invention and the scope of the appended claims.
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