Moving member movement control apparatus, moving member movement control method and machine tool movement control apparatus

A movement control apparatus for a moving member, includes: a drive unit that moves a moving member by rapid traverse on a first axis and a second axis intersecting the first axis, and overlaps the rapid traverse movements in the two axis directions to thereby allow the moving member to move around the periphery of a given area; a reference arc setting unit that sets a reference arc inscribed in the first and second axes; a timing setting unit that sets an overlap movement start timing for the rapid traverse of the moving member based on the reference arc when switching the moving member from the first axis to the second axis; and a control unit that controls the operation of the drive unit to move the moving member at a timing set by the timing setting unit.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority from a Japanese Patent Application No. 2006-181175 filed on Jun. 30, 2006, and a Japanese Patent Application No. 2006-295557 filed on Oct. 31, 2006, the entire subject matter of which is incorporated herein by reference.

TECHNICAL FIELD

The present invention relates, in a machine tool such as a lathe including more than one tools parallel arranged on a tool post functioning as a moving member, to a moving member movement control apparatus for moving the moving member in an overlapping manner by rapid traverse in two axes directions intersecting each other at right angles, a moving member movement control method, and a machine tool movement control apparatus.

BACKGROUND

Conventionally, in the above-mentioned machine tool such as a lathe, when switching tools used in machining, for example, there is employed such a tool switching method as shown inFIGS. 17A to 17Dand18. That is, in this machine tool, a tool post61, on which there are parallel arranged tools62A,62B and62C respectively composed of cutting tools or the like, can be moved correspondingly to a work W not only along the X axis direction which is the advancing and retreating direction of the tools62A to62C but also along the Y axis direction which is the parallel arranged direction of the tools62A to62C. And, for example, after end of machining of the work W using the tool62A, when switching the tool62A over to the tool62C while skipping the tool62B with its tool nose projecting, firstly, as shown inFIG. 17A, the tool post61is positioned at a first position P1where the nose of the tool62A has a given clearance C with respect to the outer peripheral surface of the work W.

After then, as shown inFIG. 17B, the tool post61is moved in the X axis direction and is positioned at a second position P2where the nose of the tool62B to be skipped has the given clearance C with respect to the outer peripheral surface of the work W. This second position P2is a transit position where, when the tool post61is moved in the Y axis direction, interference between the most projecting tool62B and work W can be avoided. Next, as shown inFIG. 17C, the tool post61is moved in the Y axis direction while skipping the tool62B and is positioned at a third position P3where the nose of the tool62C exists on an X-axis direction extended line passing through the center of the work W. Further, as shown inFIG. 17D, the tool post61is moved forward in the X axis direction and is positioned at a fourth position P4where the nose of the tool62C has the given clearance C with respect to the outer peripheral surface of the work W.

However, in the conventional movement control method, there is found a problem that, since the tool post61, at the second position P2and third position P3, is switched in the moving direction while it is stopped between the X and Y axis directions, the moving time of the tool post61in the tool switching operation is long. That is, as shown inFIGS. 18 and 19, where the moving time between the first position P1and second position P2is expressed as t1, the moving time between the second position P2and third position P3is expressed as t2, and the moving time between the third position P3and fourth position P4is expressed as t3, the moving time t0necessary for the tool replacement is at least t1+t2+t3.

On the other hand, in JP-A-9-262742, there is disclosed a tool movement control method in which, a tool is moved overlappingly in two axes directions in a given time zone to thereby shorten the tool moving time. Also, in JP-A-11-104934, there is disclosed a tool movement control method in which when replacing a tool, while the tool is being moved from the current position to a tool replacement position, there is set an approach position for allowing the tool to pass while avoiding interference with other parts and, at the approach position, the tool is moved overlappingly without stopping the rapid traverse movements in two directions, thereby shortening the tool moving time. Further, in JP-A-2006-24174, there is disclosed a moving member movement control method in which a moving member is moved at a rapid traverse speed by a first axis drive device up to a direction switching point for avoiding interference with other parts, and the moving member is slowly moved at an accelerating or decelerating speed equal to or lower than the maximum accelerating or decelerating speed of the first axis drive device within the moving time of the second axis drive device after the moving member arrives at the direction switching point, thereby shortening the moving time of the moving member.

SUMMARY

However, in these conventional movement control methods, there have been found the following problems.

That is, JP-A-9-262742 discloses a method for moving a tool in the two axes directions at the same time in an overlapping manner but does not disclose a method for moving a tool while setting a moving path capable of preventing the tool from interfering with other parts such as a work. Owing to this, when the method disclosed in JP-A-9-262742 is applied to the tool replacement shown inFIGS. 17A to 17D, there is a fear that, when the tool is selectively moved, the tool can interfere with other parts such as a work.

Also, in the method disclosed in JP-A-11-104934, when the rapid traverse movements in the two directions are actually overlapped with each other, the moving route of the tool is curved in the vicinity of the approach position and the tool is thereby not able to pass through the approach position accurately. In order that the tool can be made to pass through the approach position accurately without interfering with other parts, the rapid traverse movements in the two directions must be stopped once and switched at the approach position, which makes it impossible to shorten the moving time of the tool.

Further, according to the method disclosed in JP-A-2006-24174, the moving member is moved in the two axes directions at the same time. However, since, when the moving member is moved in the outside area of the linear-shaped moving route, it has to make a detour in an expanded manner while drawing an arc-shaped locus, the moving stroke of the moving member increases, which requires a wide moving space.

The present invention is made aiming at solving the above-mentioned problems found in the conventional technologies. Thus, it is an object of the invention is to provide an apparatus for controlling the movement of a moving member, which can move the moving member in a short time along a short moving route capable of preventing the moving member from interfering with other parts, a method for controlling the movement of the moving member, and an apparatus for controlling the movement of a machine tool.

In attaining the above object, according to a first aspect of the invention, there is provided a movement control apparatus for a moving member, including: a drive unit that moves a moving member by rapid traverse on a first axis and a second axis intersecting the first axis, and overlaps the rapid traverse movements in the two axis directions to thereby allow the moving member to move around the periphery of a given area; a reference arc setting unit that sets a reference arc inscribed in the first and second axes; a timing setting unit that sets an overlap movement start timing for the rapid traverse of the moving member based on the reference arc when switching the moving member from the first axis to the second axis; and a control unit that controls the operation of the drive unit to move the moving member at a timing set by the timing setting unit.

According to the present invention, while the moving member is moving along the first axis direction, the moving member is moved in the second axis direction according to a set movement start timing and is rapidly traversed while drawing an approximate arc locus based on the reference arc. Owing to this, the moving member can be moved by rapid traverse in a short time along a moving route capable of preventing the moving member from interfering with other parts. Therefore, when the invention is applied to a machine tool, a moving member such as a tool post provided in the machine tool can be moved and positioned by rapid traverse at a given position in a short time with no interference with a work, thereby being able to enhance the productivity of the machine tool.

By the way, in the present invention, the movement of the moving member includes the movement of the moving member when the moving member moves alone and, in a state where the moving member is fixed, the movement of a second moving member capable of relative movement with respect to the moving member when the second moving member moves alone, or the movements of the these two moving members when they move simultaneously. In short, the movement of the moving member means that the moving member generates a relative movement with respect to other parts. Also, in the invention, the overlap movement means that the moving member is moved in the two directions of the first and second axes simultaneously.

According to a second aspect of the invention according to the first aspect of the invention, the movement control apparatus further includes: a first calculating unit that calculates more than one tangent to the reference arc and the intersections of the respective tangents; and a second calculating unit that calculates a first time and a second time respectively necessary for the moving member to arrive at a first axis direction line parallel to the first axis and at a second axis direction line parallel to the second axis respectively passing through the intersections from the start of the overlap movement, wherein the timing setting unit delays the overlap movement start timing of the moving member in order for the two times to be at least equal to each other when the second time is shorter than the first time.

According to this structure, by setting the overlap movement start timing of the moving member, it can be judged based on the calculation results of the first and second calculating unit whether the moving locus of the moving member passes inside an intersection existing outside the reference arc or not. When the moving locus passes inside the intersection, the moving locus can be corrected to pass outside the intersection by the timing setting unit. When the overlap movement start timing is set in the above-mentioned manner, the overlap movement start timing can be set properly regardless of the rapid traverse speed or the speed of the acceleration or deceleration. Thanks to this, the invention can be flexibly applied even to an apparatus which is different in the rapid traverse speed or in the acceleration or deceleration speed.

According to a third aspect of the invention according to the second aspect of the invention, the more than one tangent are set at regular angle intervals.

Therefore, clearances between the reference arc and the respective intersections can be made equal.

According to a fourth aspect of the invention according to the first aspect of the invention, the timing setting unit includes a table which contains data on overlap movement start timings set based on the relationship between the travel distance of the moving member in the first axis direction and the radius of the reference arc, and the control unit controls the operation of the drive unit according to the data shown in the table.

Thanks to this structure, simply by referring to the table, the overlap movement start timing can be set and thus the setting operation can be carried out quickly.

According to a fifth aspect of the invention according to the fourth aspect of the invention, the table contains data on overlap movement start timings set based on a permissible line and a permissible arc which are continuous with each other and are respectively set by a given amount inwardly of the first axis, second axis and reference arc.

Thanks to this structure, the moving locus of the moving member can be made to approach other parts such as a work without interfering them, thereby being able to shorten the moving time of the moving member. Therefore, when the invention is applied to a machine tool, it can contribute toward enhancing the productively of the machine tool.

According to a sixth aspect of the invention, there is provided a method for controlling a movement of a moving member, including: moving a moving member by rapid traverse on a first axis and a second axis intersecting the first axis, and overlapping the rapid traverse movements of the moving member in the two axes directions to move the moving member around the periphery of a given area; setting a reference arc inscribed in the first and second axes; and setting the overlap movement start timing of the rapid traverse movement of the moving member based on the reference arc when switching the moving member from the first axis to the second axis.

According to the invention, there can be obtained a similar operation to the first aspect of the invention.

According to a seventh aspect of the invention, there is provided a movement control apparatus for a machine tool that includes a tool post with more than one tool parallel arranged thereon, the movement control apparatus including: a drive unit that generates relative movements by rapid traverse between the tool post and a work in the direction of a first axis and in the direction of a second axis intersecting the first axis, and overlaps the rapid traverse relative movements in the two axes directions to thereby move the tool post relatively to the work in the periphery of the work; a reference arc setting unit that sets a reference arc inscribed in the first and second axes; a timing setting unit that sets an overlap movement start timing for the rapid traverse of the tool post based on the reference arc when switching the tool post from the first axis to the second axis; and a control unit that controls the operation of the drive unit to move the tool post at a timing set by the timing setting unit, wherein the switching of the tools is carried out by the control unit. Besides, the movement control apparatus can includes a structure according to any one of the first to fifth aspects of the invention.

Therefore, according to the invention, in the machine tool, there can be obtained a similar operation to the first aspect of the invention.

According to an eighth aspect of the invention according to the seventh aspect of the invention, the movement control apparatus further includes a distance setting unit that sets a spaced distance in the tool parallel arrangement direction between the nose of a tool and the outer peripheral surface of another tool adjoining the tool nose, wherein the reference arc setting unit sets the radius of the reference arc at the value of a distance equal to or less than the spaced distance. According to this structure, it is possible to set a more reasonable arc, which in turn makes it possible to properly prevent interference between a work and a tool such as a cutting tool for machining the side surface of the work.

According to a ninth aspect of the invention according to the seventh aspect of the invention, the movement control apparatus further includes distance setting unit that sets a spaced distance in the tool parallel arrangement direction between the nose of a tool and the outer peripheral surface of another tool adjoining the tool nose, and sets the travel distance of the tool in the tool advancing and retreating direction, wherein the reference arc setting unit compares the spaced distance and travel distance, and the reference arc setting unit sets the radius of the reference arc at the value of the shorter one of the two compared distances. According to this structure, it is possible to set a more reasonable arc, which in turn makes it possible to properly prevent interference between a work W and a tool such as a cutting tool for machining the side surface of the work W.

According to a tenth aspect of the invention according to the seventh aspect of the invention, the movement control apparatus further includes a distance setting unit that sets a spaced distance in the tool parallel arranged direction between a work and the nose of a tool adjoining the work, wherein the reference setting unit sets the radius of the reference arc at the value of a distance equal to or less than the spaced distance. According to this structure, it is possible to properly prevent interference between a work and a front machining tool such as a drill or a reamer.

According to an eleventh aspect of the invention according to the seventh aspect of the invention, the movement control apparatus further includes a distance setting unit that sets a spaced distance in the tool parallel arranged direction between a work and the nose of a tool adjoining the work, and sets the travel distance of the tool in the tool advancing and retreating direction in the tool switching operation, wherein the reference setting unit compares the spaced distance and travel distance, and the reference setting unit sets the radius of the reference arc at the value of the shorter one of the two compared distances. According to this structure, there can be set a more reasonable arc and thus it is possible to properly prevent interference a work and a front machining tool such as a drill or a reamer.

As described above, according to the invention, a moving member can be moved by rapid traverse along a route capable of preventing the moving member from interfering with other parts, thereby being able to enhance the productivity of the machine tool to which the invention is applied.

DETAILED DESCRIPTION

Now, description will be given below of embodiments of the invention.

First Embodiment

Firstly, description will be given below of a first embodiment of the invention with reference toFIGS. 1 to 10B.

As shown inFIG. 1, in a machine tool according to the first embodiment of the invention, a headstock22is disposed on a frame21in such a manner that it can be moved in the Z axis direction and, on the headstock22, there is rotatably supported a main spindle23which extends in the Z axis direction. On the frame21, there is disposed a back attachment24in such a manner it is situated opposed to the headstock22and can be moved in the Z axis direction; and, on the back attachment24, there is rotatably supported a sub spindle25which extends in the Z axis direction. And, on each of the main and sub spindles23and25, there is mounted a collet23a(a collet on the sub spindle25side is not shown) which is capable of holding a work W.

As shown inFIG. 1, between the headstock22and back attachment24, on the machine frame21, there is disposed a tool post26functioning as a moving member in such a manner that it can be moved in the X axis direction and Y axis direction which are respectively perpendicular to the Z axis direction which is the moving direction of the headstock22. On the tool post26, there are disposed tools27composed of more than one cutting tool extending in the X axis direction and capable of cutting the work W on the main spindle23from the outer peripheral side of the work W, while the tools27are arranged parallel to each other and are spaced at given intervals in the Y axis direction. Also, on the tool post26, adjacently to the tools27, there are further disposed tools29to31made of drills, reamers or the like extending in the Z axis direction or in the Y axis direction and capable of machining the work W on the main spindle23from the end face side thereof or machining the work W on the sub spindle25from the end face side thereof, while these tools are arranged parallel to each other and spaced at given intervals in the Y axis direction or in the X axis direction. By the way, not only in the first embodiment but also in the following embodiments, the movements of the headstock22and back attachment24, that is, the movement of the work W and the movement of the tool post26may respectively be the relative movements between (the headstock22and back attachment24) and (the work W); and, specifically, the work W or tool post26may move alone or both of them may move at the same time. In the respective embodiments, description will be given assuming that the work W or tool post26moves alone.

Next, description will be given below of the structures of a control unit35for controlling the operation of a machine tool having the above-mentioned structure and other parts thereof.

As shown inFIG. 2, the control unit35includes a CPU36, a ROM37, a RAM38, an input part39, a display part40, a main spindle rotation control circuit41, a main spindle feed control circuit42, a tool feed control circuit43constituting a drive part, a sub spindle rotation control circuit44and a sub spindle feed control circuit45. In the present embodiment, the above-mentioned CPU36, ROM37and RAM38cooperate together in constituting a reference arc setting unit, a timing setting unit, a first calculating unit, a second calculating unit and a control unit.

The input part39is composed of a keyboard including a numeral key or the like; and, from the input part39, there are manually input various kinds of data and commands relating to the machining operation of the machine tool such as data on the kinds and dimensions of the work W. The display part40is composed of a display device such as a liquid crystal display or the like.

The CPU36outputs operation instructions to the main spindle rotation control circuit41, main spindle feed control circuit42, tool feed control circuit43, sub spindle rotation control circuit44and sub spindle feed control circuit45to thereby operate the main spindle23, headstock22, tool post26, sub spindle25and back attachment24and the like through a main spindle rotation drive device46composed of a driving motor or the like, a main spindle feed drive device47, a tool feed drive device48, a sub spindle rotation drive device49and a sub spindle feed drive device50.

The tool feed drive device48, when carrying out the below-mentioned operation to switch the tools27on the tool post26and tools27,30on the tool post26with respect to the work W, moves the tool post26in the X axis direction or in the Y axis direction to thereby move the tool post26along two axis directions, that is, the advancing and retreating direction of the tools27with respect to the work W and the parallel arranged direction of the tools27. Therefore, the tool feed drive device48constitutes a drive unit for driving the tool post26in such a manner that the tool post26can be moved in the X axis and Y axis directions. Also, when carrying out the switching operation of the other tools29,30, the tool feed drive device48drives the tool post26to move it in the Y axis direction along the parallel arranged direction of the tools29,30, while the headstock22or back attachment24is moved in the Z axis direction which is the axial direction of the work W by the main spindle feed drive device47or sub spindle feed drive device50, whereby the tools29,30are moved relatively along their advancing and retreating direction.

In the ROM37, there are stored various control programs which are used to machine the work W. And, the CPU36controls the progress of the programs stored in the ROM37. In the RAM38, there are temporarily stored machining programs, various kinds of data and the like which are manually inputted therein and are calculated by the operation of the CPU36, and the like. For example, in the Ram38, there are stored various kinds of data on the tool pitches and the like relating to the respective tools27,29to31. That is, when the tools are tools27A to27C composed of cutting tools shown inFIGS. 5A to 5D, various kinds of data on machining such as tool pitches Pt1, Pt2between the respective tools27A to27C, shank widths L1, L2of the tools27A to27C, distances D1, D3between the tools27A to27C, distances D2, D4expressing height differences between the noses of the tools27A to27C, and the positions of the tool noses are manually input or are operated by the CPU36, and are then stored into the given area of the RAM38.

Also, in the other area of the RAM38, there are stored the maximum speed data and acceleration speed (including deceleration speed) data for every feed speeds such as the rapid traverse, cutting feed and other similar feed of the tool post26, headstock22and back attachment24in the respective X, Y and Z axis directions.

Further, the RAM38includes a temporary retention area for temporarily retaining the operation results of the programs shown inFIG. 7which will be discussed later, and a working area for retaining the operation results in such a manner that they can be used to control the operation of the tool post26.

Next, description will be given below of the operation of the above-structured machine tool when the fixed tools27composed of cutting tools for machining the work W are switched. This switching operation is carried out by rapid traverse. And, as will be discussed later, for example, as shown inFIGS. 3,5A to5D and8, there is set a reference arc E1having radiuses D1to D4which forms a given area in each of corner portions C1and C2in such a manner that it is spaced from the work W and turns round the periphery of the work W. With the movement of the tool post26, the noses (leading end portions) of the tools27A to27C, in one corner portion C1, carry out overlap movements (simultaneously in the X axis and Y axis directions) outside the reference arc E1according to an overlap movement start timing K set based on the reference arc E1, next move while drawing an arc-shaped locus (which is hereinafter referred to as an approximate arc or an approximate arc locus) E2shown inFIG. 4, and then move while drawing a linear locus; and further, in the other corner portion C2, these tool noses move outside the reference arc E1while drawing an approximate arc locus E2based on the reference arc E1. By the way, inFIGS. 5A to 5D, what moves along the reference arc E1outside the work W is the nose (leading end portion) of the tool27B; however, in the following description, the movement of the tool nose (leading end portion) is regarded as the movement of the tool post26.

Here, the approximate arc locus E2of the tool post26shown inFIG. 4is the result obtained by overlapping the rapid traverse movements of the tool post26in the X and Y axis directions. That is, the approximate arc movement of the tool post26based on the reference arc E1can be obtained by overlapping the movements of the tool post26in the Y axis direction and in the X axis direction, which are different from each other, at a given timing where the tool post26is moving in the X axis direction or in the Y axis direction. For example, as shown inFIG. 4, when the movement of the tool post26in the X axis direction having started on ahead arrives at a given timing, the movement thereof in the Y axis direction is started, whereby the movements of the tool post26in the X and Y axis directions are overlapped with each other to provide the movement that draws the approximate arc locus E2. The reason why the approximate arc locus E2is formed is as follows: that is, in the movements of the tool post26in the X and Y axis directions, when the tool post26arrives at the top speed instantaneously and the top speed is maintained, inFIG. 4, the approximate arc locus E2is not formed but a slanting linear locus is formed. However, actually, in the two end portions of the speed area, there are formed an acceleration area and a deceleration area, respectively; and, therefore, there is formed the approximate arc locus E2. And, as can be seen clearly fromFIG. 4, the earlier the overlap movement start timing K is, the longer the overlap time is and the larger the radius of curvature of the approximate arc locus E2is. On the other hand, the slower the overlap movement start timing K is, the smaller the radius of curvature of the approximate arc locus E2.

Now, as shown inFIGS. 5A and 5B, when the tools27A to27C (in these figures, each tool is shown in a rectangular shape for simplification of illustration) are arranged parallel to each other, for example, in the Y axis direction and they are moved for switching along the Y axis direction, the tool post26, in order to avoid interference between the most projecting tool27(inFIGS. 5A and 5B, tool27B) and the work W, is retreated in the X axis direction so as to be able to secure a clearance C with the mounting error of the tools27or the like taken into consideration. The positions of the tools27A to27C and tool post26in the X axis direction at the then time are as regarded as their retreat positions, and the retreat positions are regarded as the ends of their moving ranges in the X axis direction. Therefore, the travel distance of the tool post26in the X axis direction is determined according to the quantity of projection of the most projecting tool27B. Also, the travel distance of the tool post26in the Y axis direction is determined by the distance between the tools27to be switched.

InFIGS. 5A and 5B, by moving the tool post26to the left, the tool switching from the left tool27A to the right tool27B or27C is carried out. Here, the spaced distance D1between the nose of the tool used before switched, that is, the nose of the tool27A and the outer peripheral surface of the tool adjoining backwardly in the moving direction, that is, the outer peripheral surface of the tool27B is compared with the retreat distance D2from the retreat movement start position to the retreat position, thereby setting the reference arc E1(the reference arc shown right inFIG. 3) having a radius composed of the shorter one of the two compared distances D1and D2. The spaced distance D1can be calculated by subtracting the shank width L2of the tool27B from the tool pitch Ptl between the tools27A and27B. And, the tool post26moves outside the reference arc E1while drawing the approximate arc locus E2based on the reference arc E1. However, as shown inFIG. 5B, when the radius of the reference arc E1is D1, since the radius D1is shorter than the retreat distance D2, firstly, the tool post26retreats linearly in the X direction by an amount almost equivalent to the difference between the spaced distance D1and retreat distance D2and, after then, the tool post26moves following the reference arc E1.

Next,FIGS. 5C and 5Dshow an operation in which, when a currently used tool27is replaced with another other tool27to be newly used along the Y axis direction, the tool27to be newly used is moved so as to approach the work W from its retreat position.

That is, the tool post26has been moved to the retreat position. And, a spaced distance D3between the outer peripheral surface of a tool adjoining forwardly of the moving direction of the tool to be newly used, that is, the outer peripheral surface of the tool27B and the nose of the tool to be newly used, that is, the nose of the tool27C is compared with an approach distance D4by which the nose of the tool to be newly used is moved so as to approach up to a position where a clearance C can be secured between the nose of the tool and work W, whereby there is set the reference arc E1having a radius composed of the shorter one of the two compared distances D3and D4. In the embodiment shown inFIGS. 5A to 5D, the spaced distance D3is set to be the same as the tool pitch Pt2and, therefore, the value of the tool pitch Pt2stored in the RAM38can be used as it is. The tool post26moves outside the reference arc E1while drawing an approximate arc locus E2based on the reference arc E1. However, when the moving radius is D3, the moving radius is smaller than the approach distance D4. Therefore, firstly, the tool post26approaches the work W while drawing the approximate arc locus E2following the reference arc E1; and, after then, the tool post26approaches the work W linearly in the X axis direction by an amount almost equivalent to the difference between the approach distance D4and spaced distance D3.

Here, description will be given below also of a method for calculating the distances D1to D4when switching front machining tools.

FIG. 6shows an operation to switch tools composed of front machining tools30A to30D such as a drill and a reamer arranged parallel on the tool post26in the machine tool shown inFIG. 1. The tools30A to30D such as a drill and a reamer are structured such that the leading end outer peripheral sides thereof or the whole leading end faces thereof are formed as the tool noses thereof, while the tools30A to30D are used to machine the end face of the work W. InFIG. 6, the tools30, namely, the tools30A to30D are different in the projecting quantities thereof and at least one of the centrally situated tools30B and30C projects further than the tools30A and30D which are situated on the two end sides of the tool post26. The front machining tools such as a drill and a reamer are different from the tools such as the cutting tools27for machining the side surfaces of the work W only in that the spaced distances D1and D3(Y axis direction) are changed to the spaced distances D1and D3between the outer peripheral surface of the work W and the outer peripheral surfaces of the tools30A to30D adjoining the work W.

When the work W is moved from the position of the leftward situated tool30A to the rightward situated tool30D for tool switching, as the spaced distance D1on the tool switch movement start side, there is employed a spaced distance between the outer peripheral surface of the moving direction forward side of the work W, that is, the outer peripheral surface of the work W existing backwardly in the moving direction of the tool post26and the outer peripheral surface of the tool30B. Also, as the spaced distance D3on the tool switch movement end side, there is employed a spaced distance between the outer peripheral surface of the moving direction backward side of the work W, that is, the outer peripheral surface of the work W existing forwardly in the moving direction of the tool post26.

As described above, when switching the tools, the spaced distance D1is compared with the retreat distance D2, and the spaced distance D3is compared with the approach distance D4to find the reference arc E1, whereby the tools30A to30D can be moved by rapid traverse outside the reference arc E1with no interference with the work W.

Next, description will be given below of a procedure for switching the tools27.FIG. 7shows a routine for setting an overlap movement start timing K. This routine shows how the programs stored in the ROM37shown inFIG. 2are executed under the control of the CPU36.

That is, in the input part39shown inFIG. 2, when a given operation for tool switching is executed, in Step S1(the term “Step” is hereinafter omitted) shown inFIG. 7, radiuses D1to D4are calculated and data on theses radiuses D1to D4are stored in the working area of the RAM38. And, according to the above-mentioned comparison between D1and D2or between D3and D4, there are decided the radiuses of the reference arcs E1in the respective corner portions. Each of these reference arcs E1is set such that it is inscribed in a first axis and a second axis which are the moving route of the tool post26. When the setting of the reference arc E1is ended, in order that the approximate arc locus E2of the tool post26can be set outside the reference arc E1according to the reference arc E1, there is carried out a processing for setting the overlap movement start timing K of the tool post26.

That is, in S2, in the respective corner portions C1and C2, the X axis or Y axis on which the tool post26moves earlier is regarded as a first axis, and the X axis or Y axis on which the tool post26moves later is regarded as a second axis; and, the operation start timing of the tool post26in the second axis direction is set for a determined value. For example, inFIG. 3, in the first corner portion C1which exists on the right, the X axis functions as the first axis and the Y axis functions as the second axis. In the second corner portion C2existing on the left, the Y axis functions as the first axis, while the X axis functions as the second axis. The operation start timing on the second axis is set in the ROM37such that, for example, the operation start timing on the second axis coincides with the operation start timing on the first axis or the operation start timing on the second axis is delayed slightly with respect to the operation start timing on the first axis. In short, in this stage, the operation start timing on the second axis may not be earlier than the operation start timing on the first axis. By the way, inFIG. 4, since the X axis functions as the first axis and the Y axis functions as the second axis; and, therefore,FIG. 4shows the example of the corner portion C1shown right inFIG. 3.

In S3, as shown inFIG. 9A, not only there are calculated more than one tangent L1for every given regular interval angle θ with respect to the reference arc E1, but also there are calculated intersection coordinates F functioning as intersections with these tangents L1. In this manner, since the tangents L1are spaced at regular angle intervals, the respective distances between the respective intersection coordinates F and reference arc E1can be made equal to each other. InFIG. 9A, the number of the tangents L1is four including the X axis functioning as the first axis and the Y axis functioning as the second axis and, therefore, their associated intersection coordinates F are set in three positions spaced at regular intervals. The above-mentioned given angle θ is an angle which has been previously set by manual input or the like and, therefore, the number of the tangents L1and the number of intersection coordinates F are to be set previously.

In S4, assuming that the tool post26has moved while drawing an approximate locus E2to be created by the above-mentioned overlap movement start timing K, as shown inFIGS. 9B and 10A, there are calculated a first time t1and a second time t2where the tool post26arrives at a Y axis direction line L3functioning as a second axis direction line and at an X axis direction line L2functioning as a first axis direction line, both the Y and X axis direction lines L3and L2passing through the intersection coordinates F.

Next, in S5, the time t1and time t2are compared with each other. When t1=t2, the approximate arc locus E2is to pass on the intersection coordinates F. When t1<t2, as shown by a solid line inFIG. 9B, the approximate arc locus E2exists outside the reference arc E1and is spaced with respect to the intersection coordinates F outwardly from the reference arc E1. For t1>t2, as shown by a two-dot chained line inFIG. 9B, the approximate arc locus E2is situated nearer to the reference arc E1than the intersection coordinates F. Therefore, when t1≦t2is satisfied, the approximate arc locus E2does not come inside the reference arc E1, whereas, for t1>t2, as shown by a two-dot chained line inFIG. 9C, there is a possibility that the tool post26can move inside the reference arc E1, thereby raising a fear that the tools27A to27C can interfere with the work W. In other words, since the intersection coordinates F and reference arc E1are close to each other, for t1>t2, there is a high possibility that the approximate arc locus E2has come inside the reference arc E1in the vicinity of the intersection coordinates F (the first axis direction extended position of the intersection coordinates F). Further, even when the approximate arc locus E2exists outside the reference arc E1in the vicinity of the intersection coordinates F, there is a fear that the approximate arc locus E2has come inside the reference arc E1between the present intersection coordinates F and next intersection coordinates F. The reason for this is as follows. That is, when the moving locus between the two intersections is near to a linear line, if the moving locus comes inside the intersection coordinates F on one intersection coordinate F, there is a high possibility that the approximate arc locus E2between the two intersection coordinates F respectively existing before and behind such intersection coordinate F has come inside the reference arc E1. By the way, as in the operation according to the present embodiment, the moving locus, normally, provides a linear-shaped locus or an outward expanded arc-shaped locus, but does not provide an inward expanded locus under the condition that a first axis moves earlier than or simultaneously with a second axis, the two axes then move overlappingly and, after then, the first axis stops earlier than or simultaneously with the second axis. Therefore, when the moving locus exists outside on all intersection coordinates F, there is no possibility that the moving locus can come inside the reference arc E1.

Therefore, for t1>t2, in S6, as shown inFIG. 10B, in order to provide t1=t2, the movement start timing in the second axis direction is delayed.

And, data on an overlap movement start timing K expressing t1=t2or t1<t2are stored in the temporary retention area of the RAM38.

When t1=t2or t1<t2is satisfied, the program goes to S7. In S7, it is checked on all intersection coordinates F whether the processings in S3to S6have been ended or not. When ended, the program goes to S8; and, when not ended, the program goes back to S3.

In S8, it is checked on all corner portions C1, C2of a path, for example, shown inFIG. 3whether the processings in S2to S7have been ended or not. When ended, that is, when the setting of the overlap movement start timing K in all corner portions has been ended, the program goes to S9. When not ended, the program goes back to S2, where the processing changes to the processing of the overlap movement start timing K on the next corner portion.

In this manner, the routes along which the tools27A to27C move outside the reference arc E1, in other words, the overlap movement start timings K expressing the approximate arc locus E2that does not interfere with the work W are calculated; and, in S9, the data on the overlap movement start timing K is transferred from the temporary retention area of the RAM38and is stored into the working area of the RAM38.

Therefore, after then, when switching the tools, not only the tool post26can be moved outside the reference arc E1by rapid traverse while drawing the approximate arc locus E2but also interference between the tools27A to27C and the outer peripheral surface of the work W can be prevented. Thanks to this, the switching of the tools27A to27C can be carried out in a short time and the working efficiency of the machine tool can be enhanced.

As shown inFIG. 9D, the more the number of the tangents L1to be set at regular angle intervals is, the nearer to the reference arc E1the intersection coordinates F come; and, therefore, the approximate arc locus E2can be made to approach the reference arc E1further. InFIGS. 9A and 9B, there is shown an example in which, for simplification of explanation, the value of the regular spacing angle θ is set for 30 degrees. However, actually, the angle is set in the range of about 1 to 18 degrees; and, therefore, the intersection coordinates F exist at positions which are quite close to the reference arc E1. Accordingly, in this case, it is possible to shorten the route of the approximate arc locus E2, thereby being able to further shorten the tool switching time.

According to the present embodiment, there can be obtained the following effects.

(1) In the tool switching operation, owing to the overlap movement by rapid traverse in the X axis direction and in the Y axis direction, the tool post26is moved while drawing the approximate arc locus E2based on the reference arc E1. Thanks to this, when compared with the conventional tool switching method shown inFIGS. 17A to 19, as can be obviously seen from a two-dot chained line shown inFIG. 19, the time t<SUB>0</SUB> necessary for the tool switching operation can be shortened. This makes it possible to enhance the productivity of the machine tool.

(2) When moving the tools27A to27C to their respective retreat positions, as the reference arc E1, there is set an arc having a radius equal to or less than the distance D1between the nose of the tool27A used before the tool switching operation and the outer peripheral surface of the tool27B which adjoins the tool27A and exists backwardly of the tool27A in the moving direction. Also, when moving the tools27A to27C to their respective approach positions with respect to the work W, as the reference arc E1, there is set an arc having a radius equal to or less than the distance D3between the nose of the tool27C to be used after the tool switching operation and the outer peripheral surface of the tool27B which adjoins the tool27C and exists forwardly of the tool27C in the moving direction. As described above, the reference arc E1is set such that it has a radius equal to or less than the distance D1or D3between the nose of the tool27A or27C and the outer peripheral surface of the tool27B adjoining the tools27A and27C. Owing to this, the tools27A to27C are allowed move outside the reference arc E1spaced a given distance apart from the work W, whereby, when the tools27A to27C are selectively moved, they are prevented from interfering with the work W. This can be attained not only by paying attention to the fact that the noses of the parallel arranged tools27A to27C and the outer peripheral surfaces of the tools27A to27C respectively adjoining the tool noses are disposed spaced from each other by such distance as to prevent them from touching the work W at the same time, but also by using this position relationship when setting the reference arc E1. That is, since the distances D1, D3and distances D2, D4are compared with each other and the shorter one of the distances is set as the radius of the reference arc E1, in other words, since the radius of the reference arc E1is up to the distance D1or D3, under the condition that the noses of the tools27A to27C and the outer peripheral surfaces of the tools27A to27C respectively adjoining their associated tool noses are prevented from touching the work W at the same time, the interference between the tools and work W can be avoided properly.

(3) Since the overlap movement start timing K of the tool post26may simply be set, the load of the memory or the RAM38can be reduced.

(4) The tool post26, in the corner portions C1and C2, is moved while drawing the approximate arc locus E2within an area defined by the X and Y axes and does not go beyond such area. Owing to this, the moving routes of the tool post26and tools27A to27C can be shortened and thus the moving time thereof can be shortened. The shortened time makes it possible to enhance the productivity of the machine tool.

(5) By setting the overlap movement start timing K of the tool post26, it can be found whether the approximate arc locus E2of the tool post26passes inside the intersection coordinate F situated outside the reference arc E1or not. When the approximate arc locus E2exists inside the intersection coordinate F, the overlap movement start timing K is delayed so that the approximate arc locus E2is allowed to exist outside the intersection. Therefore, regardless of the rapid traverse speed or the speeds of acceleration and deceleration, the overlap movement start timing K can be set properly. Thanks to this, the invention can flexibly applied even to a machine tool which is different in the rapid traverse speed and in the speeds of acceleration and deceleration.

Second Embodiment

Next, description will be given below of a second embodiment according to the invention with reference toFIGS. 1 to 8,FIGS. 11 to 13, mainly of the portions thereof which are different from the above-mentioned first embodiment.

In the second embodiment, as shown inFIGS. 4 and 8, overlap movement start timing K used to form an approximate arc locus E2, which does not interfere with the work W, is not set by calculation but is set based on a program shown inFIG. 11according to tables respectively shown inFIGS. 12 and 13. These tables are data tables on overlap movement start timings K previously calculated from the relationship between the travel distances of the tool post26in the first axis direction and the radiuses of the reference arc E1, and these tables are stored in the given area of the RAM38in such a manner that they correspond to the corner portions C1and C2respectively.FIG. 12is a table used to set the overlap movement start timings K in the first corner portion C1shown inFIGS. 3,5A and5B, whereasFIG. 13is a table used to set the overlap movement start timings K in the second corner portion C2shown inFIGS. 3,5C and5D.

In the tool selective operation, the CPU36, firstly, in S101shown inFIG. 11, calculates the reference arc E1similarly to the first embodiment. Next, in S102, from the data table of the RAM38shown inFIG. 12, there is extracted the overlap movement start timing K according to the relationship between the travel distance of the tool post26in the first axis direction in the first corner portion C1, that is, the travel distance of the tool post26in the X axis direction and the radius of the reference arc E1; and, the thus extracted overlap movement start timing K is then stored into the working area of the RAM38. For example, when the travel distance of the tool post26in the X axis direction is 10 mm and the radius of the reference arc E1is 6 mm, from the data table shown inFIG. 12, there is found the position of the overlap movement start timing K, namely, 4.1 mm. And, in S103, the overlap movement in the Y axis direction is started from a point where the travel distance of the tool post26in the X axis direction is 4.1 mm, and the tool post26is moved outside the reference arc E1in the first corner portion C1while drawing the approximate arc locus E2without interfering with the work W.

Also, in the second corner portion C2, after calculation of the reference arc E1in S101, in S102, from the data table of the RAM38shown inFIG. 13, there is extracted the overlap movement start timing K according to the relationship between the travel distance of the tool post26in the direction of the Y axis functioning as the first axis and the radius of the reference arc E1; and, the thus extracted overlap movement start timing K is then stored into the working area of the RAM38. For example, when the travel distance of the tool post26in the Y axis direction is 40 mm and the radius of the reference arc E1is 6 mm, from the data table shown inFIG. 13, there is found the position of the overlap movement start timing K, namely, 34.1 mm. And, in S103, the overlap movement of the tool post26in the X axis direction in the second corner portion C2is started at a point where the travel distance of the tool post26in the Y axis direction is 34.1 mm, and the tool post26is moved outside the reference arc E1while drawing the approximate arc locus E2.

Therefore, according to the second embodiment of the invention, there can be obtained the following effect.

(6) Since, in setting the overlap movement start timing K, there is extracted from the table the data on the present overlap movement start timing K, the setting of the overlap movement start timing K can be carried out quickly in a short time.

Third Embodiment

Next, description will be given below of a third embodiment of the invention with reference toFIGS. 14A to 16, mainly of the portions thereof which are different from the second embodiment.

In the third embodiment, as shown inFIG. 14A, between the reference arc E1and the outer peripheral surface of the work W, in an area not in contact with the work W, there are virtually set a permissible arc E3and a permissible line E4composed of a straight line, and there are formed tables expressing data on the travel distances of the tool post26and the radiuses of the reference arc E1. The permissible line E4is formed to be continuous with the end portion of the permissible arc E3. That is, the third embodiment permits at least the two end portions of the approximate arc locus E2of the tool post26to be situated between (the permissible arc E3and permissible line E4) and (reference arc E1). The permissible arc E3and permissible line E4are set with a clearance C shown inFIGS. 5A to 5Dtaken into consideration. For example, they are set inside the first axis, second axis and reference arc E1at a position spaced from the reference arc E1by an amount equivalent to 20% or so of the clearance C. And, data on the permissible arc E3and permissible line E4may be previously set in the ROM37or may be manually input into the ROM37from the input part39by a user.

Accordingly, as can be seen clearly fromFIGS. 15 and 16, the data shown in the respective tables can be used to quicken the overlap movement start timing K.

For example, similarly to the above, in the first corner portion C1, when the travel distance of the tool post26in the X direction is 10 mm and the radius of the reference arc E1is 6 mm, from the data table shown inFIG. 15, as the overlap movement start timing K, there can be found 3.8 mm. And, in S103, the Y axis overlap movement of the tool post26is started at a point where the travel distance of the tool post26in the X axis direction is 3.8 mm, and the tool post26is moved outside the reference arc E1while drawing the approximate arc locus E2.

Also, in the second corner portion C2, when the travel distance of the tool post26in the Y axis direction is 40 mm and the radius of the reference arc E1is 6 mm, from the data table shown inFIG. 16, as the overlap movement start timing K, there can be found 29.6 mm. And, in S103, the X axis overlap movement of the tool post26is started at a point where the travel distance of the tool post26in the Y axis direction is 29.6 mm.

Also, in the present embodiment, alternatively, the permissible arc E3may not be set but only the permissible line E4may be employed. In this case, as shown inFIG. 14B, the permissible line E4is extended up to the position of the reference arc E1. Therefore, an area, where the tool post26does not come into contact with the work W, is set based on the reference arc E1and permissible line E4and thus a table is formed according to data on the reference arc E1and permissible line E4.

Thus, according to the third embodiment, there can be obtained the following effect.

(7) Since the tool post26can be moved inside the reference arc E1, the moving route of the tool post26can be shortened, thereby being able to reduce the time necessary for the tool switching operation.

Modifications

By the way, the above-mentioned embodiments can also be enforced while they are modified in the following manner.

In the above embodiments, the invention is embodied in the control of the movement of the tool post26in the tool switching operation of a machine tool. However, the invention can also be embodied in other apparatus, for example, a carrier apparatus such as a carrier robot which holds a work or the like and carries it from one position to the other position.

In the above embodiments, the overlap movement start timing K is set based on the data on the positions of the tool post26on the X and Y axes. However, the overlap movement start timing K can also be set based on data on the time that has passed after start of the movement of the tool post26.

In the above embodiments, the first and second axes are arranged to intersect each other at right angles. However, the invention can also be embodied in a structure in which the two axes intersect each other obliquely.

And, in the above embodiments, the invention is embodied by switching the tools27which are composed of cutting tools. However, the invention can also be embodied by switching other tools such as rotary tools.