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Description  |
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BACKGROUND OF THE INVENTION
(1) Field of the Invention
This invention relates to a method of determining an operating path of a
tool in relation to a surface of a workpiece, wherein a plurality of
points of contact between a tool and the workpiece surface are determined
and information in the form of digitised co-ordinate axis values relating
to each determined point of contact is stored in a computer memory device,
from which a set of co-ordinate axis values an operating path for the tool
can be derived.
(2) Summary of the Prior Art
In U.S. Pat. No. 4,136,306 is disclosed a sewing machine for digitising a
predetermined pattern and thereafter stitching the predetermined pattern
on a workpiece, in the use of which machine a model pattern is moved under
operator control along co-ordinate x and y axes successively to bring
so-called "stitch points" into an appropriate relationship with an
operating tool, the stitch points thus constituting points of contact
between the tool and the workpiece surface. In operation, in such machine,
furthermore, the operator uses a so-called "joy stick switch" which
generates signals and supplies them to a computer which serves to convert
the signals to drive signals for motors by which the x and y axis movement
is effected. When each stitch point is properly aligned with the tool,
furthermore, the co-ordinate axis values can be digitised and stored in
the computer memory, and from the set of co-ordinate axis values thus
obtained the operating path of the tool in relation to the workpiece
surface can be derived.
Whereas the aforementioned method of digitising a pre-determined pattern
has been found to be satisfactory where a prepared model pattern is
supplied, the method described does not in any way assist in the
determination of the location of the successive points of contact, still
less the spacing between them. The method is therefore limited in its
application in that a prepared model pattern is required for each style of
workpiece to be operated upon. In addition, while said method has proved
satisfactory for use with two-dimensional workpieces, the preparation of a
model pattern for a three-dimensional surface, e.g. a shoe bottom, would
be time-consuming and generally lead to greater difficulties than
envisaged with a two-dimensional surface.
It is thus the object of the present invention to provide a method for
determining each point of contact between a tool and a workpiece surface
and for controlling the spacing between adjacent points, specifically for
use with a method of determining an operating path of a tool in relation
to such surface.
SUMMARY OF THE INVENTION
The present invention provides the improvement consisting in a method for
determining each point of contact between a tool and a workpiece surface
and for controlling the spacing between adjacent points, said method
comprising the steps of (i), starting from a point of contact (constituted
by a last preceding stored point) of the tool and the workpiece surface,
effecting relative movement between the tool and the workpiece surface out
of such contact through a predetermined distance along a first axis, and
thereafter (ii) returning the tool and the workpiece surface into contact
selectively (a) along said first axis, compensating relative movement
taking place automatically along a second axis and/or a third axis such
that the tool describes a great circle of a sphere of which the starting
point of contact forms the center, or (b) along said third axis,
compensating relative movement taking place automatically along said
second axis such that the tool describes a small circle of such sphere,
whereby the tool is maintained, and the next-to-be-stored point of contact
is thus spaced, at the predetermined distance from the starting point of
contact, regardless of the contour of the workpiece surface.
It will thus be seen that, using this method in accordance with the
invention, a series of spaced apart points of contact can be determined
automatically by the machine and further that the method is capable of
operation regardless of whether the workpiece surface is substantially
flat (2-dimensional) or significantly contoured (3-dimensional).
It will of course be appreciated that using this method once the tool and
workpiece surface have been separated by the predetermined distance, it is
desirable to provide some restriction whereby relative movement
therebetween cannot take place where the effect would be to separate the
tool and the workpiece surface by a distance greater than the
predetermined distance.
By using the method in accordance with the invention, the spacing of the
successive points is controlled with a result that, in subsequent
operating cycles of the machine, by also controlling the time taken to
move from one point to the next succeeding point, the feed speed of the
tool in relation to the workpiece surface can be controlled during the
determining of the operating path of the tool. Thus, for example, where a
constant velocity is required it is merely necessary to ensure that the
distance between adjacent points is the same in every case. On the other
hand, if different speeds are required, then this can be achieved by
varying the predetermined distance in the path determining operation. In
order to achieve the desired result, preferably the predetermined distance
is set by the operator for each next-to-be-digitised point.
It will be appreciated that if the tool and/or the workpiece surface is to
any extent compressible the relative position between the tool and surface
when moved to a point to be digitised may vary according to the pressure
applied therebetween. Thus, preferably in carrying out the method in
accordance with the invention, as the tool and the workpiece surface are
urged into contact with one another, a predetermined load is applied
thereto. Furthermore, preferably the predetermined load is constant for
each point.
The method in accordance with the invention has been found to be
especially, but not exclusively, suitable for determining the path of a
roughing tool by which marginal portions of the bottom of a lasted shoe
can be roughed, prior to the attachment by adhesive to such shoe bottom of
a sole unit. Furthermore, in such a case, conveniently the first axis
extends heightwise, the second lengthwise and the third widthwise of the
shoe bottom.
It has also been found convenient to use the tool which is to perform an
operation upon the workpiece surface as the tool to be used for
determining the operating path.
BRIEF DESCRIPTION OF THE DRAWINGS
There now follows a detailed description, to be read with reference to the
accompanying drawings, of one method in accordance with the invention,
this method having been selected for description merely by way of
exemplification of the invention and not by way of limitation thereof.
In the accompanying drawings:
FIG. 1 is a left hand perspective view of a shoe bottom roughing machine in
which the method in accordance with the invention can be used;
FIG. 2 is a diagram indicating the layout of a control panel of such
machine;
FIG. 3 is a flow diagram indicating a "digitise" routine of the method in
accordance with the invention;
FIG. 4 is a flow diagram of a "next point establish" routine of the method
in accordance with the invention; and
FIGS. 5 to 7 are diagrams to assist in explaining certain calculations
carried out in connection with the method in accordance with the
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The method in accordance with the invention now to be described is for use
in a machine which is suitable for use in performing a roughing operation
progressively along marginal portions of shoe bottoms. Such a machine is
described in detail in U.S. Pat. No. 4,391,011 assigned to the present
assignee. For the purpose of the present application appropriate parts of
such machine are illustrated in FIGS. 1 and 2 wherein it can be seen that
the machine comprises a base 10 on which are mounted two upstanding
brackets 12 each supporting a pivot shaft 14, each shaft carrying a
structure 16 on which a shoe support 18 is carried. Each shoe support 18
is arranged to support a shoe S carried thereon, bottom uppermost, with
the toe end thereof facing towards the front of the machine i.e. towards
the operator. Although in the machine here described two shoe supports are
provided, in other similar machines only one such shoe support may be
provided. Towards the rear of the base 10 is also mounted a support column
structure 22 supporting a horizontal web structure 24 by which tool
supporting means generally designated 26 is carried, said means comprising
a bifurcated arm 30 by which two rotary radial roughing brushes 168 are
supported side-by-side. The brushes are caused to rotate in contrary
directions such that each brush effects an inwiping action on the marginal
portion of the bottom of a shoe as it is caused to operate progressively
therealong. For rotating the brushes, an electric motor 300, supported by
a bracket 302 on the base 10, is operatively connected thereto through a
series of belts and pulleys. The arm 30 is supported, for pivotal movement
about a horizontal pivot, in upstanding lugs 32, one arranged at either
side of the arm 30, of a support casting 34, which is itself supported
above and below the web structure 24, for pivotal movement about a
vertical pivot. It will thus be appreciated that, in the operation of the
machine, either one of the shoe supports 18 can pivot about its shaft 14
to move a shoe S supported thereby in a direction extending generally
lengthwise of the bottom of the shoe, while the tool supporting means is
capable of pivotal movement about two axes thus to move the tools 168
supported thereby widthwise and heightwise of the shoe bottom, as the shoe
support is moved as aforesaid.
For the purpose of this specification, movement of the shoe support 18 will
be referred to hereinafter as "x-axis" movement, that of the tool about
the vertical pivot as "y-axis movement" and about the horizontal pivot as
"z-axis movement". For effecting such movements, furthermore, the machine
comprises, for each shoe support 18, a first (x-axis) stepping motor 144
mounted on the base 10 and effective, through a series of pulleys and
belts and through a toothed segment 140 mounted on its associated support
structure 16, to cause x-axis movement of the shoe support 18 to take
place about the shaft 14. Also, the machine comprises a second (y-axis)
stepping motor 84 which is carried by the web structure 24 and is
effective, through a toothed segment 42, to cause y-axis movement of the
support casting 34, and thus of the brushes 168 mounted on the arm 30,
about the vertical pivot on the web structure 24. Again, the machine
comprises a third (z-axis) stepping motor (not shown) which is supported
by the support casting 34 rearwardly of its vertical pivot and acts on a
rearwardly extending portion 102 of the arm 30, thus to cause z-axis
movement of the brushes 168 mounted on said arm 30 about its horizontal
pivot in the support casting 34.
The arm 30 of the tool supporting means 26 also supports, for pivotal
movement thereon about a horizontal pivot defined by pins 154, a cradle
160 (forming part of the tool supporting means) on which the brushes 168
are carried, said horizontal pivot being arranged to pass through the
operating surface of each brush 168 in the region of its area engaging the
shoe bottom when the machine is in use. Pivoting the cradle 160 is this
manner enables the plane of each radial brush to be maintained normal, or
substantially normal, to the shoe bottom portion being operated upon. For
so pivoting the cradle, the machine comprises a fourth stepping motor 232
operatively connected by a rod 204 to said cradle 160.
The machine also comprises computer control means which, in the operation
of the machine, is effective to control the relative positioning of the
shoe bottom and the roughing brushes 168, lengthwise, heightwise and
widthwise of the shoe bottom, as the brushes are caused to operate
progressively along opposite marginal portions of the shoe bottom. This is
achieved by generating and supplying control pulses to each of the
stepping motors, in accordance with a programmed instruction, including
digitised co-ordinate axis values, using three co-ordinate axes, for a
plurality of successive selected points along the marginal portion to be
operated upon of the shoe bottom, such digitised information being stored
in a memory of the computer. In addition, the computer supplies control
pulses to the stepping motor 232 for causing the cradle 160 to pivot as
aforesaid. Furthermore, the computer may have a grading programme which is
effective to vary the operating path of the tools appropriately to the
length of the shoe being operated upon.
For determining the operating path of the tool in relation to the shoe
bottom, the various stepping motors of the machine and also the computer
control means thereof are utilised using a "model" shoe, that is to say a
shoe which has not been specially prepared but which usually will be in
the middle of the expected size range for the style. This shoe is loaded
into one of the shoe supports 18 and relative movement is effected between
the brushes 168 and such shoe under the control of the operator, selected
points of contact between each brush and the shoe bottom being digitised
using the computer control means and stored in the form of digitised
co-ordinate axis values in the computer memory.
For assisting in carrying out the method in accordance with the invention,
furthermore, the machine also comprises operator-controlled means
comprising a manually operable control device (see FIG. 2) having a
control panel including a keyboard generally designated 640, "number"
buttons (from 0 to 9), and a "teach" button 642. In addition, the control
panel has joy stick 646 by which y-axis and z-axis movement of the tool
supporting means 26 can be effected in relation to the shoe bottom, in
opposite directions, under operator control, and which is movable in four
directions, viz. two heightwise (z-axis) directions and two widthwise
(y-axis) directions.
More particularly, and in carrying out the method in accordance with the
invention, the appropriate brush 168 and the leading, heel end, portion of
the shoe bottom are first moved to a start position, constituting an
initial starting point of contact, which is then digitised and stored as
aforesaid. In the machine above described, such digitising and storing is
effected by actuation of the "teach" button 642, which also causes the
tool to be moved, out of contact with the surface of the shoe bottom, by a
predetermined distance (d) from said starting point, along the z-axis,
which extends heightwise of the shoe bottom. This z-axis movement may be
conveniently viewed as moving the tool from the center of a sphere, which
center is defined by the starting point, to the surface of the sphere, the
sphere having a radius equal to the predetermined distance (d).
Thereafter, in carrying out said method, the tool 168 is returned along
the z-axis and/or along the y-axis under operator control so as to bring
the tool once again into contact with the shoe bottom. In response to such
return movement along the z-axis, simultaneously corresponding x-axis and
y-axis movement of the shoe support 18 takes place automatically, will be
referred to hereinafter. Similarly, in response to y-axis movement under
operator control, simultaneously x-axis movement of the shoe support 18
takes place automatically. In both instances the automatically controlled
movement is effective to maintain the predetermined distance (d) between
the tool 168 and the starting point. In this manner, the movement of the
tool in relation to the shoe bottom may be regarded as maintaining the
tool on the surface of the sphere referred to hereinbefore. The tool and
the surface are thus brought into contact once more at a further point,
spaced from the starting point by the predetermined distance (d)
regardless of the contour of said surface, and this further point can then
be digitised and stored in the computer memory. In addition, this further
point constitutes the starting point for the next point of contact to be
determined.
More particularly in carrying out the method in accordance with the
invention, the operator first causes the tool to be lowered, from the
position (at the "top" of the sphere) to which it has been automatically
moved upon the last actuation of the "teach" button 642, along the z-axis
towards the shoe bottom. (Because the tool is initially at the "top" of
the sphere, no y-axis movement is "allowed" at this time.) Simultaneously
the shoe support is moved along the x-axis automatically thus to maintain
the distance between the tool and the starting point on the shoe bottom at
said predetermined distance from one another. Once an appreciable amount
of z-axis movement has taken place, the operator may, again using the joy
stick, cause y-axis movement of the tool to take place. Simultaneously,
x-axis movement of the shoe support will be automatically effected to
maintain the spacing between the tool and the starting point. Thereafter,
as will be explained hereinafter, any further z-axis movement will be
compensated for not only by automatically effected x-axis movement of the
shoe support, but also by automatically effected y-axis movement of the
tool. When a further point of contact between the tool and shoe bottom has
been reached, and further the operator is satisfied that the selected
point will lie on a desired operating path of the tool relative to the
shoe bottom in an operating mode of the machine, he actuates the "teach"
button 642, whereby digitised information concerning the relative position
of the tool and shoe bottom is generated and stored by the memory device
of the computer in the manner well known per se. Operating the "teach"
button, of course, again causes the brush to be raised from the surface of
the shoe bottom through the predetermined distance, in readiness for
determining the next point of contact.
When digitised information for each point has been obtained in the above
manner, the information thus obtained constitutes a set of information
from which can be derived the operating path of the tools 168, in an
operating mode of the machine, relative to the shoe bottom.
The computer control means of the machine is used for calculating and
effecting the compensating x-axis or y-axis movement which takes place in
response to y-axis or z-axis movement under operator control, as will now
be described with reference to FIGS. 3 and 4. As mentioned above, the
appropriate brush 168 is first moved to its start position (step 500) and
waits there until a "teach" signal has been generated by an actuation of
button 642 (step 502). In response to such actuation the co-ordinate axis
values for the start position (constituting an initial starting point of
contact between the tool and the workpiece surface) are digitised and
stored (step 504). Step 506 enquires as to whether a signal has been
generated indicating that the whole of the path determining operating has
been completed. In the event of a `No` answer, the tool 168 is then moved
along the z-axis, such movement taking place automatically as a result of
the actuation of the "teach" button 642. With the tool 168 in its upper
position, the computer then instructs that the "next point establish"
routine be carried out (step 510).
The "next point establish" routine is illustrated in FIG. 4. In carrying
out this routine, firstly the values for x-axis movement, y-axis movement
and z-axis movement, together with a value for the angle a (representing
the angular displacement of the tool in response to y-axis movement) are
initialised (step 512). Next, the position of the joy stick 646 is
monitored as to whether z-axis movement is called for (step 514); it will
of course be appreciated that z-axis movement may have a positive or
negative value, according to which of the two z-axis directions has been
selected. If the answer is in the affirmative, a calculation is made as to
whether such movement is "allowed", bearing in mind to that such movement
could have the effect of spacing the tool and workpiece surface at a
distance greater than the predetermined distance (d) (step 516). If again
the answer is in affirmative, then compensating x-axis movement and y-axis
movement is calculated (step 518), as will be described in greater detail
hereinafter with reference to FIGS. 5 to 7. X-axis, y-axis and z-axis
movement is then effected in accordance with the joy stick control and
with the calculations (step 520), and further the values for x-axis
movement, y-axis movement and z-axis movement are stored (step 522). The
next step in the routine is then to monitor the "teach" button 642 (step
524); if the button has been actuated, then the routine is terminated,
while if no acutation has taken place, then the routine returns to step
514.
If the answer to step 514 is in the negative, then the joy stick 646 is
monitored as to whether y-axis movement is called for (step 526) and
again, if the answer is in the affirmative, then enquiry is made as to
whether such movement is "allowed" (step 528). If the answer is in
affirmative, then the compensating x-axis movement is calculated (step
530), such calculation being described in greater detail hereinafter with
reference to FIGS. 5 to 7. The x-axis and y-axis movement is then effected
(step 532) in accordance with the joy stick control and the calculation.
In addition, the angle a is calculated (step 534), again as described in
detail hereinafter with reference to FIGS. 5 to 7, and the values for
x-axis movement, y-axis movement and the angle a are then stored (step
536). Thereafter step 524 is followed, monitoring the "teach" button as
aforesaid. It will be also be noted that, in the event of a negative
response to anyone of steps 516, 526 and 528, the status of the "teach"
button 642 is monitored (step 524). The routine continues to be followed
until such time as the "teach" button 642 is actutated, whereupon the
"next point establish" routine is terminated and the "digitise" routine of
FIG. 3 is again executed, starting at step 504.
As already mentioned above, initially only z-axis movement can take place
when the tool has been moved to its upper position (step 508). In FIG. 5,
therefore, a diagram indicates movement of the tool from the "top" of the
sphere (point A) along an arc AC (the center of curvature of which is at
B), the arc lying in the plane of x-axis movement (represented by BC).
E.sub.1 represents a first point to which the tool is moved (or the
cumulative movement of the tool) from the point A while point E.sub.2
represents a further position to which the tool is moved along the arc AC
from the point E.sub.1.
It will be appreciated that AB, BC, BE.sub.1 and BE.sub.2 are all equal,
and constitute the predetermined distance d. In addition, AD.sub.1
represent the amount of z-axis movement under operator control necessary
for moving the tool to point E.sub.1, and D.sub.1 E.sub.1 represents the
x-axis movement effected automatically to maintain the tool on the arc AC.
Similarly, D.sub.2 represents a further point to which the tool is moved
from D.sub.1 to bring the tool to the point E.sub.2 from the point
E.sub.1, and E.sub.2 F represents the extra x-axis movement required to
maintain the tool on the arc AC.
The relationship between the z-axis movement AD and the x-axis movement DE
is determined by the equation
##EQU1##
where x=DE and z=AD.
For calculating the further movement represented by E.sub.2 F, the equation
must read
##EQU2##
where x=E.sub.2 F, and z.sub.1 =AD.sub.1 and z.sub.2 =AD.sub.2.
It will thus be appreciated that for calculating the compensating x-axis
movement in response to z-axis movement under operator control, this
latter equation is applicable in all instances.
Turning to the calculation of compensating x-axis movement in response to
y-axis movement, FIG. 6 shows a circle of radius DE, which is effectively
a plan view in a direction of the arrow VI of FIG. 5, sectioned along e.g.
the line D.sub.1 E.sub.1. In FIG. 6 EG represents an arc along which the
tool is to be moved, G.sub.1 representing a first point to which the tool
is moved (or the cumulative movement of the tool) from the point E, and
G.sub.2 represents a further point to which the tool is to be moved from
the point G.sub.1.
It will thus be appreciated that H.sub.1 G.sub.1 represent y-axis movement
under operator control, and H.sub.1 E represents compensating automatic
x-axis movement, while JG.sub.2 represents further y-axis movement under
operator control, and H.sub.1 H.sub.2 represents the further compensating
x-axis movement required to bring the tool from G.sub.1 to G.sub.2. The
angle a.sub.1 represents the angular displacement of the tool from line DE
when moved to point G.sub.1 and the angle a.sub.2 represents the angular
displacement of the tool when positioned at the point G.sub.2. It will be
appreciated that DE is equal to DG.sub.1 and DG.sub.2.
The compensating x-axis movement is thus calculated by the equation
##EQU3##
where r represents the radius of the circle (=DE, DG.sub.1, DG.sub.2) and
y=the y-axis movement under operator control. It will of course be
appreciated that r is a known value, being the x-axis compensating
movement calculated as set out above with reference to FIG. 5.
If further y-axis movement is then effected, the compensating x-axis
movement can be calculated by the equation
##EQU4##
where y.sub.1 represents G, H, and Y.sub.2 G.sub.2 H.sub.2.
It will be thus be appreciated that this latter equation is of general use
in calculating the compensating x-axis movement in response to y-axis
movement.
In general, it is likely that following initial z-axis movement and some
y-axis movement thereafter, further z-axis movement will be required in
order to bring the tool into contact with the workpiece surface. Where
z-axis movement has to take place other than in the plan of the x-axis
movement, not only x-axis compensating movement but also y-axis
compensating movement must be calculated, as will now be described with
reference to FIG. 7. In this Figure, in addition to the arc EG (shown in
FIG. 6), a further arc KL is shown, the point K indicating a position to
which the tool will be moved in response to further z-axis movement under
operator control after the y-axis movement of FIG. 6.
The line KG of FIG. 7 represents an arc corresponding to the arc E.sub.1
E.sub.2 of FIG. 5, and the equation for calculating the distance E.sub.2 F
of FIG. 5 can be utilised for calculating the corresponding radial
component of movement of the tool from the point G to the point K in
response to z-axis movement of the tool from the point G. In this case,
however, because the line DK is angularly displaced by the angle a from
the x-axis (line DL), the radial component of movement GK must be further
divided into x-axis and y-axis movement indicated respectively by the
lines GN and KN. The angle a is of course known in that it can be
calculated from the relationship y/r (HG/DG) of FIG. 6. Consequently,
x-axis movement required in this situation of FIG. 7 can be calculated by
the equation
GN=cos a.multidot.GK
and similarly compensating y-axis movement can be calculated by the
equation
KN=sin a.multidot.GK
where GN represents the x-axis compensating movement, KN the y-axis
compensating movement and GK the radial component of movement indicated in
FIG. 5 by the line E.sub.2 F.
Thus, a general equation for calculating x-axis compensating movement in
response to z-axis movement under operator control would read
##EQU5##
and similarly a general equation for calculation of compensating y-axis
movement in response to z-axis movement under operator control would read
##EQU6##
It will thus be appreciated that in the case of z-axis movement under
operator control, the tool will follow a great circle of the sphere, such
circle being angularly displaced from the x-axis by the angle a, while in
the case of y-axis movement under operator control, the tool will follow a
small circle of such sphere, such small circle lying in a plane which is
normal to the z-axis. (In passing, the radius of the great circle is
always d, while the radius of the small circle is r, representing the
cumulative x-axis movement effected in response to z-axis movement under
operator control.)
The predetermined distance (radius of the great circle) d may be pre-set.
Alternatively, it may be selected, from a pre-set range, by the operator
for each digitising operation. Such setting by the operator is facilitated
especially where an interactive computer control is provided whereby, each
time a negative response is given to step 524 (FIG. 4), the operator is
invited to set the value "d" for the next digitising step. Varying the
setting of the predetermined distance d is of course effective, in the
operating mode of the machine, to vary the speed at which the tool 168 is
caused to operate along the workpiece surface.
It will thus be appreciated that, in using the method in accordance with
the invention, a relatively straightforward and efficient way is provided
of moving a tool from one digitised point to determine the next-to-be
digitised point regardless of the contour of the surface along which the
points are to be determined. The manner in which the points are digitised
is not the subject of the present application; any convenient way which is
in general practice may be used for carrying out the digitising step
itself. Similarly, although the movement along the three axes as described
herein is under the control of stepping motors, any numerically controlled
motor could be used for the purpose; for example d.c. servo motors could
be utilized.
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