Note: Descriptions are shown in the official language in which they were submitted.
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Thiq invention relates to the cleaning of a work-
piece in a workpiece holder.
This application is a division of Canadian Patent
Application, 5erial No. 314,000, filed October 24, 1978.
An automatic machining center is disclosed which is so
completely automated that it can be reliably operated unattended
and unwatched for an entire shift.
Numerically controlled automatic machining centers
have been manufactured in the past which can automatically per-
form a preprogrammed sequence of machining operations. Suchmachining centers have a plurality of tools which are stored in a
tool magazine and æ e automatically inserted into and removed
from the spindle to perform the corresponding machining operations.
A machining center of this type is disclosed in U.S. Patent No.
3,704,510, iqsued to Robert K. Sedgwick et al for a "Machine
Tool with Tool Changer". However, this type of automatic
machining center requires the services of a full time operator -~
for loading and unloading the workpieces, st æ ting and stopping
the machine for each machining cycle, cleaning out chips,
inspecting the tools for excessive wear and breakage, replacing
broken or excessively worn tools, compensating for tool wear, etc.
Automatic workpiece handling apparatus has been manu-
factured in the past, as disclosed in U.S. Patent No. 3,825,245,
issued to John G. Osburn et al, for a "Workpiece Changer
Mechanism for a Machine Tool", and in U.S. Patent No. 3,796,163,
issued to Ronald E. Meyer et al, for a Manufacturing System",
but such apparatus also requires the services of one or more full
time operators.
App æ atus for automatically inspecting tools for
excessive wear and breakage and for automatically replacing
broken or excessively worn tools has been devised in the past -
as disclosed in U.S. Patent 3,817,647, issued to Jerome H.
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Lemelson, for a 'Tool Control Arrangement', and in U.S. Patent
No. 3,963,364, issued to Jerome ~1. Lemelson, for a 'Tool Control
System and ~ethod". However, the machine tools disclosed in the
Lemelson patents also require the attention of an operator. In
spite of the great strides that have been made in automating
machining operations, no prior art machine tool or machining
center is known which is capable of operating unattended and un-
watched for an entire shift or longer.
According to the invention there is provided a method
of cleaning machining chips off a workpiece mounted on a work-
piece holder and on which a machining operation has been com-
- pleted comprising the steps of: (a) applying a stream of liquid
r to said workpiece to wash chips that were formed during the
machining operation off said workpiece, and (b) applying a
stream of gas to said workpiece after the chips have been
removed by the liquid to remove the liquid therefrom.
Suitably the workpiece may be rotated through 360
while the stream of liquid is applied thereto; and through 360
~, while the stream of gas is applied thereto.
The workpiece holder is suitably enclosed on at least
three sides by an enclosure, there being a door in one side of
the enclosure through which the workpiece holder can be moved
into the enclosure. In this case the method also inc,ludes the
preliminary steps of i) opening the door before step (a) to
; admit the workpiece holder into the enclosure; and ii) closingthe door before step (b) to contain the stream of liquid~.
By means of the present invention an automatic
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machining center is provided capable of completely unmanned
operation for an entire shift or longer. The unmanned
~ 30 machining center of this invention includes a workpiece
t ~ support, a spindle adapted to hold a cutting tool and to
~ rotate the tool, means for moving the workpiece support and
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spindle relative to each other to machine a workpiece on the
workpiece support with a tool in the toolholder, a tool magazine
for storing a plurality of tools each of which is mountable
in the spindle, a tool changer for transferring selected
tools from the tool magazine to the spindle and from the
spindle back to the tool magazine, a workpiece magazine
for storing a plurality of workpieces each of which is
mountable on the workpiece support, shuttle means for
transferring selected workpieces from the workpiece magazine
to the workpiece support and for removing finished work-
pieces from the workpiece support, and tool checking means
for checking to verify the presence of an unbroken tool in
the spindle.
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Other objects and advantages of the invention will be
apparent from the detailed description herein.
Figure 1 is a plan view of one preferred embodiment
of the invention,
Fig. 2 is a side elevation view and longitudinal
sectional view taken on the line 2-2 of Fig. l;
Fig. 3 is a fragmentary front elevation view of the
mechanism for opening and closing the coolant enclosure doors
taken on the line 3-3 of Fig. 2;
Fig. 4 is a fragmentary plan view taken on the line
4-4 of Fig. 3;
Fig. 5 is a front elevation view of the housing
containing the calibration bushing and proximity switches;
Fig. 6 is a side elevation view taken on the line
6-6 of Fig. 5;
Fig. 7 is a cross-sectional view taken on the line
7-7 of Fig. 5 and showing a probe tip within the calibration
bushing,
Fig. 8 is a plan view of the housing of Figs. 5 to 7
showing a probe tip contacting the Z calibration surface thereof,
Fig. 9 is a block diagram of the spindle position
feedback system for the embodiment of Figs. 1 to 8;
Fig. 10 is a block diagram of the broken tool detec-
tor for the embodiment of Figs. 1 to 8; and
Fig. 11 is a flow chart of the program for checking
for broken or incorrect tools.
Referring to Figs. 1 and 2, one preferred embodiment
of the invention includes a horizontal machining center 10
which has a first bed portion 12 that supports horizontal ways
14. A workable carriage 16 is slidably mounted on ways 14 for
movement along a horizontal X-axis 18 (Fig. 1). A worktable 20
(Fig. 2) is rotatably mounted on worktable carriage 16 for
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rotation about a vertical B-axis 22. Worktable 20 is adapted
to slidably receive a conventional pallet 24 and to clamp pal-
let 24 thereto in position to machine a workpiece (not shown)
which is clamped to pallet 24 by conventional means (not shown).
Worktable 20 can be indexed to a desired rotary position about
B-axis 22 to present any desired face of the workpiece to the
cutting tool.
Machining center 10 has a second bed 26 which sup-
ports horizontal ways 28. An upright 30 is slidably mounted on
ways 28 for movement along horizontal Z-axis 32 (Fig. 1) which
is perpendicular to both X-axis 18 and B-axis 22. Upright 30
supports vertical ways 34 (Fig. 2). A spindlehead 36 is slid-
,
ably mounted on ways 34 for movement along a vertical ~-axis
38 (Fig.2) which is perpendicular to both X-axis 18 and Z-axis
32. A spindle 40 which is adapted to receive a cutting tool -
42 is rotatably mounted on spindlehead 36 for rotation about
Z-axis 32. Rotation of spindle 40 and movement of the other
machine tool parts along or around their respective axes is
effected by electric motors tnot shown) which are controlled
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I 20 by conventional electrical controls (not shown) mounted in a
machine control unit and power distribution panel 44 (Fig. 1).
A hydraulic unit 46 (Fig. 1) provides hydraulic fluid under
; pressure for the hydraulic components of the system.
~ A conventional tool magazine 48 (Fig. 2) having a
j plurality of tool sockets 49 and a conventional tool changer
~ 50 hav,ing~a pair of tool change arms 51 are mounted on upright
,t ~ 30 for storing ~ plurality of cutting tools and for transfer-
~ ring the tools from tool magazine 48 to spindle 40 and vice
t~ versa. The tools include a special probe (not shown) which is
mounted in a standard toolholder and can be clamped in spindle
, 40 for ~libration purposes as described in later paragraphs.
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A workpiece magazine 52 is mounted on a frame 54 ad-
jacent to bed 12. Workpiece magazine 52 contains a track 56
upon which wheeled carts 58 are movably mounted and can be
moved around track 56 by means of a conventional drive chain
60 (Fig. 2) which is driven by conventional means (not shown).
Each of the carts 58 is adapted to slidably receive a pallet
24 upon which a workpiece (not shown) is clamped. A pallet
loading and unloading station 62 (Fig. 1) is mounted adjacent
to track 56 and a hydraulic ram 64 is mounted in position to
pull pallets 24 from station 62 to an adjacent cart 58 and to
push pallets 24 from cart 58 to station 62. A similar hydrau-
lic ram 66 is mounted in position to push pallets 24 from cart
58 to worktable 20 and to pull pallets 24 from worktable 20 to
cart 58. Hydraulic rams 64 and 66 have extendible piston rods
which terminate in latch members 68 and 70, respectively, which
are shaped to engage a T-shaped recess in pallets 24 for push-
ing and pulling pallets 24. The electrical controls for rams
64 and 66 and for the workpiece magazine drive are housed in
a cabinet 71.
Pallet guideways 72 and 74 are mounted adjacent to
worktable 20 to support pallets 24 when they are being trans-
ferred from a cart 58 to worktable 20 or vice versa. Guideway
72 is supported by frame 54 while guideway 74 is supported
- by bed 12.
An enclosure 76 which is closed on three sides by
transparentrectangular panels 78 and has a pair of sliding
~ doors 80 on one closed side is mounted on bed 12 in position
f; to enclose worktable 20. The fourth side of enclosure 76 which
faces spindle 40 is open to permit machining of the workpiece
on pallet 24 inside of enclosure 76.- The top of enclosure 76
is also open. Referring to Fig. 2, the side panels 78 are
supported by uprights 82 which are attached at their bottom ends
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to bed 12 and are attached at their top end to cross member ~4.
Referring to Fig. 3, a portion of the side of enclo-
sure 76 which faces workpiece magazine 52 is closed by side
panels 78 and the centralportion thereof is closed by two slid-
ing doors 80. Both sliding doors 80 are identical and there-
fore only one door 80 will be described in detail. Each slid-
ing door 80 includes a rectangular frame 86 which is covered by
a transparent rectangular panel 88 and is bolted at its top
edge to a rectangular support plate 90. A pair of rollers 92
are rotatably attached to support plate 90 and roll on a sup- ~ -
port rod 94 which is attached to uprights 82 and spans the
upper edge of the side of enclosure 76 which faces workpiece
magazine 52. Support plate 90 is moved laterally between an
open and a closed position by a pneumatic ram 96 which is
attached at one end to upright 82 by bracket 98 and is attached
' at the other end to support plate 90 by bracket 100. Pneumatic
ram 96 is shown in its fully extended position in Figs. 3 and 4.
This corresponds to the closed position of sliding door 80.
In the fully retracted position of pneumatic ram 96, sliding -
door 80 is moved to the right in Figs. 3 and 4 to form an
opening through which pallets 24 can be moved from workpiece
magazine 52 to worktable 20 or vice versa.
The opening and closing of sliding doors 80 iB elec-
trically indicated by a three position limit switch 102 having
an actuating arm 103 which is spring biased to a central neut-
ral position. When sliding door 80 is fully closed, as shown
in Fig. 3, a lug 104 on one end of support plate 90 moves limit
switch arm 103 to a first actuated position indicating that
door 80 is fully closed. When sliding door 80 is fully opened,
a second lug 106 on the other end of support plate 90 moves
limit switch arm 103 to a second actuated position indicating
that door 80 is fully opened.
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The purpose of enclosure 76 is to permit the work-
piece on pallet 24 to be sprayed with coolant after it has been
machined to wash chips off the workpiece and off pallet 24.
The coolant is sprayed from an upstanding conduit 108 (Fig.2)
which has a plurality of orifices (not shown) spaced along its
length on the side thereof adjacent to pallet 24. Coolant
under pressure is supplied to conduit 108 by a conventional
pump (not shown) and is controlled by a conventional solenoid
valve (not shown). An upright compressed air conduit 110 (Fig.
2) is mounted beside coolant conduit 108 and also has a plura-
lity of orifices (not shown) spaced along its length on the
side thereof adjacent to pallet 24. Compressed air is supplied
to conduit 105 by a conventional air compressor (not shown) and
is controlled by a conventional solenoid valve (not shown).
The purpose of the compressed air is to blow coolant off the
workpiece and off pallet 24 after they have been sprayed with -
coolant to wash away the chips.
When coolant is sprayed through the orifices of cool-
~- ant conduit 108 to wash away the chips from the workpiece and
from the pallet 24 within enclosure 76, worktable 20 is rotated
through 360 to present every side of the work~iece and pallet
24 to the jets of coolant issuing from cooiant conduit 108.
After worktable 20 has rotated through 360, the flow of cool-
ant is switched off and the compressed air is switched on
while worktable 20 continues to rotate through a second 360
to present every side of the workpiece and pallet 24 to the ~ -
air jets issuing from compressed air conduit.
The chips washed away by the coolant fall into a
~ drain trough 112 (Fig. 2) whose lower surface is part of a
chip conveyor belt 114 (Fig. 1) which carries the chips to a --
chip cart 116 beside the machining center 10. The coolant that
was used to wash the chips off the workpiece and off pallet 24
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is collected in a conventional drain (not shown) under chip
conveyor 114 and is returned to a coolant tank 117 (Fig. l) by
conventional means (not shown). The provision of means for
automatically disposing of the chips produced by the machining
operation is an important feature of this invention since there
is no operator to remove the chips and since a build-up of
chips could interfere with the proper functioning of the
machining center.
It should be noted that machining center 10 also con-
tains a conventional coolant system (not shown) for applying
coolant streams to the cutting tool and to the portion of the
workpiece being cut during the machining operation. The pur-
pose of coolant conduit 108 is not to cool the cutting tool
during the machining operation, but rather, to wash away the -
chips after the machining operation is completed.
A small housing 118 (Figs. 2 and 5 to 8) containing
two proximity switches 120 (Fig. 5) and a calibration bushing
122 is rigidly attached to worktable carriage 16 (Fig 2.).
Calibration bushing 122 is recessed in a flat plate 124 (Figs.
5 to 8) which is bolted to housing 118 by bolts 126 (Figs. 5
and 7). Proximity switches 120 are responsive to the presence
of a metallic object within a predetermined distance the~efrom
and produce an output signal whenever a metallic object is
moved within the predetermined distance therefrom.
- Figure 10 shows the electrical circuit used in combi-
nation with proximity switches 120 to check for broken or in-
correct tools and Fig. 11 is a flow chart of the program for
checking for broken or incorrect tools. Referring to Fig. 10,
the output of both proximity switches 120 are connected in
parallel to a counter 128. The_two switches 120 are oriented
at right angles to each other (see Fig. 6) for checking diffe-
rent types of tools. Only one of the switches 120 is used for
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checking any given tool. In the example shown in Fig. 10, the
tool to be checked is a milling cutter 130 which has a plurality
of cutting teeth 132 projecting radially therefrom. In this
particular example, there are ten radially projecting teeth 132
on cutter 130.
The first step of the tool checking program (Fig. 11)
_~s step 134 in which tool 130 is positioned adjacent to the
~` appropriate proximity switch 120 such that a tooth 132 adja-
cent to proximity switch 120 will cause an output signal while
the valley between teeth 132 will not cause an output signal.
, Step 134 is initiated in response to a command programmed on -
the N.C. tape. The commandwhich initiates step 134 includes
the X, Y and Z coordinates that spindle 40 must be moved to
place tool 130 in the correct position relative to the selected
proximity sensor 120. The particular X, Y and Z coordinates
will ~ary for each different tool depending on the dimensions
and configuration of the tool.
~i
In the next program step 136, the tool 130 is either
~; rotated through 360 if it has a plurality of teeth or is ro-
tated to position its single tooth opposite proximity switch
120 and is keylocked in that position.
~ In the next program step 138, the command G38Si is
,r,, received from the ~.C. controls where i = the number of teeth
on the selected tool. Step 138 follows step 136 but occurs be-
fore rotation of tool 130 is completed. The 360 of rotation
; through which cutting tool 130 rotates in this example is timed
, from the trailing edge of a pulse output from counter 128 (Fig.
10) which indicates a valley between two of the teeth 132.
Starting from the first detected valley, the tool is rotated for -
~ 30 360 and the number of pulses occurring during the 360 rotation
r ~ iS counted by counter 128.
In the next program step 140, the number in counter
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128 is compared to the number received in step 138 to see if
the tool under test has the correct number of teeth. If the
measured number of teeth is less than it should be, this im-
plies that one or more of the teeth are broken. If the mea-
sured number of teeth is greater than it should be, this im- -
plies that the wrong tool is in the spindle. In either of
these incorrect instances, step 140 selects the ~0 branch 142
which leads to step 144. If the number in counter 128 is equal
to the number received in step 138, step 140 selects YES branch
146 which returns control to the machining operation. This
comparison is made in comparator circuit 141 (Fig. 10).
If N0 branch l42 is selected, control passes to step
144-in which the tool failure is recorded and the tool selec-
tor circuits 145 (Fig. 10) are activated to seek an alternate
tool in tool magazine 48. For the purpose of replacing a
broken tool, at least two indentical tools are stored in tool
magazine 48 for any tool that is subject to breakage. If a
given tool is liable to break more than once during a shift,
three or more of that tool can be stored in tool magazine 48.
- Step 144 leads to step 148 in which the availability
of an alternate tool is determined. If an alternate tool is
available, YES branch 150 is selected which leads to step 152 -~
in which the defective tool is replaced with an alternate tool
of the same type. The machining operation is then continued.
If an alternate tool is not available, N0 branch 154 is selec-
ted which lea~s to step 156 in which an alarm is activated and
the machining operation is suspended by emergency stop circuits
157 (Fig. 10).
- The use of the previously~noted special probe to
calibrate the ~.C. circuits is illustrated in Figs. 7 and 8.
The probe 158 is moved into contact with the front of plate 124
(see Fig. 8) to calibrate the Z-axis dimension and compensate
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for temperature expansion or contraction along the z-axis. To
calibrate the X and Y axes dimension and compensate for tem-
perature expansion or contraction along the X and Y axes, probe
158 is moved into contact with the interior of calibration
bushing 122, as shown in Fig. 7. Opposite sides of the bushing
are contacted for X-axis calibration and the top and bottom are
contacted for the Y-axis calibration. By periodically moving
probe 158 into contact with the above-noted aalibration sur-
faces and comparing the position of the spindle along the
appropriate axis with the position previously recorded for the
same calibration surface, thermal growth or contraction can
be detected and the ~.C. circuits can be recalibrated to
compensate for the thermal changes.
As an example of this calibration process, a speci-
fic compensation for z-axis temperature growth will be given.
Suppose that the Z-axis displacement of the probe is 87.8976"
when the machine is started, i.e., that the Z-axis displace-
ment is 87.8976l' at the time that the probe makes contact
with the Z-axis calibration surface 124. Suppose that one
hour later the measurement is repeated and the Z-axis displace- --
ment has changed to 87.8971ll, indicating a thermal growth
along the z-axis of 0.0005". The ~.C. controls will then be
programmed to subtract 0.0005" from every Z-axis position
reading to compensate for this thermal growth. Compensation
for the thermal growth or contraction along the X and Y axes
is accomplished in the same manner. All three axes are checkéd
and recalibrated periodically. It is important to recalibrate
the machine, tool automatically during its unmanned operation
to prevent errors from creeping in due to thermal growth or
contraction. Accordingly, the machine program includes the
steps of periodically recalibrating the machine tool at
regul-ar intervals, e.g., once an hour. This is an important
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feature in the unmanned operation because it enables the
machine to automatically compensate for temperature changes
without the need for an operator for relatively long period
of time.
Fig. 9 shows the position feedback and torque feed-
back for spindle 40. Spindle 40 is rotated by a D.C. motor
168 through gears 170. Motor 168 is controlled by a conven-
~ tional motor co~trol circuit i72 which is under the control
`i of computer 167. The armature current IA of motor 168 is
; 10 applied via conductors 176 and 178 to computer 167. A resol-
ver 180 is coupled to gears 170 and produces anangular posi-
tion signal for spindle 40 which is applied to computer 167.
This angular position signal is used to determine when spindle
40 has rotated through 360 when the number of teeth on the
i;~ tool is being checked.
r' Although the illustrative embodiments of the inven-
f~
tion have been described in considerable detail for the pur-
pose of disclosing a practical operative structure by which
the invention may be practiced advantageously, it is to be
,~ 20 understood that the particular apparatus described is intended
to be illustrative only and that the novel characteristics - ,-
of the invention may be incorporated in other structural forms
~ without departing from the spirit and scope of the invention,
,~ as defined in the sub-joined claims.
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