Source: http://www.google.com/patents/US5713253?ie=ISO-8859-1
Timestamp: 2014-11-27 22:08:37
Document Index: 359660706

Matched Legal Cases: ['art 24', 'art 252', 'art 252', 'art 252', 'art 252', 'art 252']

Patent US5713253 - Rotational machining method - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsA spindle 51 capable of controlling quantitatively the rotational angle around the center axial line itself is mounted with a turning tool 50; the spindle 51 and a workpiece are allowed to be relatively dislocated by an axial control along at least a plane perpendicular to the rotation axial line of...http://www.google.com/patents/US5713253?utm_source=gb-gplus-sharePatent US5713253 - Rotational machining methodAdvanced Patent SearchPublication numberUS5713253 APublication typeGrantApplication numberUS 08/538,724Publication dateFeb 3, 1998Filing dateOct 3, 1995Priority dateOct 7, 1994Fee statusLapsedAlso published asDE19537292A1Publication number08538724, 538724, US 5713253 A, US 5713253A, US-A-5713253, US5713253 A, US5713253AInventorsTakao Date, Masafumi Araki, Katsuji Gakuhari, Makoto KawanoOriginal AssigneeToshiba Kikai Kabushiki KaishaExport CitationBiBTeX, EndNote, RefManPatent Citations (23), Referenced by (30), Classifications (11), Legal Events (6) External Links: USPTO, USPTO Assignment, EspacenetRotational machining methodUS 5713253 AAbstract A spindle 51 capable of controlling quantitatively the rotational angle around the center axial line itself is mounted with a turning tool 50; the spindle 51 and a workpiece are allowed to be relatively dislocated by an axial control along at least a plane perpendicular to the rotation axial line of the spindle 51 in such a manner that the relative movement locus L of the spindle center Cs to the workpiece conforms to a geometry to be machined and a required front rake angle β is set, thereby allowing a mutual interpolation motion between the spindle and the workpiece to be performed; and the rotational angle of the spindle 51 is synchronously controlled with a required interrelation to the above-mentioned axial control, whereby the direction of the cutting edge of the turning tool 50 to the machined face of the workpiece is kept at a required direction at the full rotational angle position of the spindle 50 with the required front rake angle β, and the direction of the cutting edge of the turning tool 50 to the machined face of the workpiece W is kept at a required direction, and then the workpiece W is machined into a geometry determined by the interpolation locus L due to the above-mentioned mutual interpolation motion.
What is claimed is: 1. A method of machining a work piece by controlling a spindle rotational angle, comprising the steps of:mounting a turning tool with a cutting edge on a main spindle having a main spindle axis, the main spindle being rotatable about the main spindle axis through a rotational angle capable of being controlled quantitatively; imparting relative motion between the main spindle axis and the workpiece in a path of movement by controlled relative displacement between the main spindle axis and the workpiece in at least one plane perpendicular to the main spindle axis so that the path of movement of the main spindle axis relative to the workpiece conforms to a geometric shape to be machined; and keeping the cutting edge of the turning tool in a cutting direction relative to the machined face of the workpiece through the full rotational angle of the main spindle by synchronously controlling the rotational angle of the main spindle and the relative displacement between the main spindle axis and the workpiece; wherein the workpiece is machined into a geometric shape determined by the path of imparted relative motion between the main spindle axis and the workpiece. 2. A method according to claim 1, wherein the path of imparted relative motion between the main spindle axis and the workpiece is defined by a set of stored program parameters.
9. A method according to either of claims 1 or 2, wherein a required front rake angle is set for the path of imparted movement between the main spindle axis and the work piece; and whereinthe direction of a cutting edge of the turning tool relative to the machined face of the workpiece in required direction is kept with the required front rake angle. 10. A method according to claim 9, wherein the turning tool has a single cutting edge contacting the workpiece substantially at a point.
SUMMARY OF THE INVENTION The present invention is made in view of the problems as described above, and it is an object of the invention to provide a novel machining method by which there can be performed efficiently boring of arbitrary inside diameter and machining of the outer periphery of arbitrary outside diameter, as well as, taper machining, spherical surface machining, polygon machining, thread cutting, flange face machining and arbitrary geometry machining by a single turning tool regardless of tool radius, and in addition, by which there can be performed a highly accurate machining regardless of tool radius.
Also, the spindle rotational angle control machining method of the present invention is characterized in detail in that the above-mentioned axial control is performed by simultaneously controlling two axes crossing mutually on at least the same plane, and the respective axial control of the two axes is performed in a manner to draw a locus defined by a functional equation including trigonometric functions having a 90� phase difference mutually.
BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1A and 1B are illustrative views showing a principle of machining by the spindle rotational angle control machining method of a first embodiment in connection with the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to the drawings, embodiments of the present invention will be explained in detail hereinafter. First, with reference to FIGS. 1 though 28, the first embodiment will be explained.
FIGS. 1A and 1B show a principle of the machining by the spindle rotational angle control machining method according to the present invention. FIG. 1A shows an example of inner peripheral face machining in which a turning tool 50 is mounted to a spindle 51 capable of controlling quantitatively the rotational angle around the center axial line itself; the spindle 51 and a workpiece W are relatively dislocated by an axial control, in this case, by X-axis control and Y-axis control along a plane perpendicular to the rotation axial line of the spindle 51 in such a manner that the relative movement locus of the spindle center Cs to the workpiece W conforms to a geometry to be machined, thereby allowing a mutual interpolation motion of true circle between the spindle 51 and the workpiece W to be performed; and the rotational angle of the spindle 51 is synchronously controlled with a required interrelation to X-axis control and Y-axis control, whereby the direction of the cutting edge of the turning tool 150 to the inner peripheral face of the workpiece W is kept at a required direction at the full rotational angle position of the spindle 51, that is, an angle β between the cutting edge and the inner peripheral face is kept at a certain value, and then the workpiece W is machined into a geometry determined by an interpolation locus (spindle center locus) L due to the above-mentioned mutual interpolation motion, that is, into the cross sectional geometry of true circle.
In this case, the coordinate values of X-axis control and Y-axis control are given by trigonometric functional equations having a 90� phase difference mutually with the angle around the workpiece center Cw taken as a medium variable so that the interpolation locus L draws true circle.
Also, in this case, the spindle 51 and a workpiece W are relatively dislocated by X-axis control and Y-axis control along a plane perpendicular to the rotation axial line of the spindle 51, thereby allowing a mutual interpolation motion of true circle between the spindle 51 and the workpiece W to be performed; and the rotational angle of the spindle 51 is synchronously controlled with a required interrelation to X-axis control and Y-axis control, whereby the direction of the cutting edge of the turning tool 50 to the outer peripheral face of the workpiece W is kept at a required direction at the full rotational angle position of the spindle 51, that is, an angle β between the cutting edge and the outer peripheral face is kept at a certain value, and then the workpiece is machined into a geometry determined by the interpolation locus L due to the above-mentioned mutual interpolation motion, that is, into the cross sectional geometry of true circle.
In this case, the control of two axes X and Y is performed in a manner to draw a locus defined by an equation including trigonometric functions having a 90� phase difference mutually.
1! Cylindrical inner/outer face machining
As shown in FIG. 15, when the radius of the cylindrical face is taken as R; the feed rate in Z-axis direction per revolution, p; and the Z-axis coordinate at Z-axis direction feed start position, Z0 ; the coordinate positions (Xt, Yt and Zt) of the cutting edge at respective rotational angle positions are given by the following functional equation:
Xt=R cos &#952;
Yt=R sin &#952;
Zt=Z0 -(p/2 &#960;)&#952;
nx=-cos &#952;
ny=-sin &#952;
Accordingly, the spindle center locus, that is, the spindle center coordinate positions (Xs, Ys, Zs) are expressed by the following equations:
Xs=Xt+nx�Tr=R cos &#952;-Tr cos &#952;=(R-Tr) cos &#952;
Ys=Yt+ny�Tr=R sin &#952;-Tr sin &#952;=(R-Tr) sin &#952;
&#945;=tan-1 (ny/nx)=tan-1 (-sin &#952;/-cos &#952;)=&#952;+&#960;
nx=cos &#952;
ny=sin &#952;
Xs=Xt+nx-Tr=R cos &#952;+Tr cos &#952;=(R+Tr) cos &#952;
Ys=Yt+ny�Tr=R sin &#952;+Tr sin &#952;=(R+Tr) sin &#952;
In the cylindrical outer face machining, a spindle rotational angle α taking the X-axis direction as an original line is expressed by the following equation:
&#945;=tan-1 (ny/nx)=tan-1 (sin &#952;/cos &#952;)=&#952;
Accordingly, as with the cylindrical inner face machining, the axial control of respective axes X, Y and Z is performed, and the spindle rotational angle α is synchronously controlled with the axial control, whereby in this case, also the turning tool 23 faces always the normal with respect to a machined face at the full rotational angle position of the spindle 19, and thus the cylindrical outer face machining of an arbitrary radius R is performed.
The equations Xs=(R+Tr) cosθ and Ys=(R+Tr) sinθ become valid in a case where the spindle center Cs is outside the workpiece W as viewed in the Z-axis direction as shown in FIG. 4, while in a case where the spindle center Cs is inside the workpiece W as viewed in the Z-axis direction, the following equations become valid:
Xs=(R-Tr) cos &#952;, Ys=(R-Tr) sin &#952;
2! Machining of Z-axis rotating material having a diameter change in the Z-axis direction, such as taper machining
As shown in FIG. 16, assuming that in the machining, the turning tool 23 having an R-shaped cutting edge is used,the cutting edge R radius is taken as Cr; the distance from the cutting edge R center to the spindle center, Tr; the axial length in the Z-axis direction from the Z-axis zero point of the spindle 19 to the cutting edge of the tool part 24, Tz; the machining radius of the machined face, a function fr (z) with respect to Z; the feed rate in the Z-axis direction per revolution, p; and the Z-axis coordinate of the feed start position in the Z-axis direction, Z0.
The locus of the cutting edge, that is, the coordinate positions (Xt, Yt, Zt) of the cutting edge in respective rotational angle positions are given by the following functional equations with an angle θ taking the X-axis direction as an original line as a medium variable:
Xt=fr(z) cos &#952;
Yt=fr(z) sin &#952;
Xt=fr(Zt) cos &#952;=fr{Z0 -(p/2 &#960;)&#952;} cos &#952;
Yt=fr(Zt) sin &#952;=fr{Z0 -(p/2 &#960;)&#952;} sin &#952;
tr={dfr(z)/dZ}/{{dfr(z)/dZ}2 +1}1/2 tz=1/{{dfr(z)/dZ}2 +1}1/2 Accordingly, for the outer peripheral face machining, the normal vector facing outward from machined face n=(nr, nz) is expressed by the following equations: ##EQU1##
nx=nr cos &#952;=1/{{dfr(z)/dZ}2 +1}1/2 �cos &#952;
ny=nr sin &#952;=1/{{dfr(z)/dZ}2 +1}1/2 �sin &#952;
nz=-{dfr(z)/dZ}/{{dfr(z)/dZ}2 +1}1/2 The locus (Xr, Yr, Zr) of the cutting edge R center is given by the following equations:
Xr=Xt+nx�Cc
Yr=Yt+ny�Cc
Zr=Zt+nz�Cc
In this case, also, where the spindle center Cs is inside the workpiece W as viewed in the Z-axis direction, the equations Xs=Xr-Tr cosθ and Ys=Yr-Tr sin θ are valid, while where the spindle center Cs is outside the workpiece W as viewed in the Z-axis direction, the equations Xs=Xr+Tr cosθ and Ys=Yr+Tr sinθ are valid.
By the control of the spindle rotational angle α, the turning tool 23 becomes faced to the normal with respect to the machined face, and the cutting edge angle of the turning tool 23 to the workpiece W is kept at a required value at the full rotational angle position of the spindle 19.
For the inner peripheral face machining, the direction of the normal vector facing outward n in the above-mentioned outer peripheral face machining becomes reverse, and thus the spindle rotational angle α is made α=0+π, whereby the turning tool 23 becomes faced to the normal with respect to the machined face.
fr(z)=R0 +a�Z
where R0 is a radius at the machining start position, and a is a radius increasing rate in the Z-axis direction.
fr(z)=(R2 +Z2)1/2 From the above-mentioned explanation, the requirement in all machining including the machining of an arbitrary geometry by using the turning tool 23 having an R-shaped cutting edge can be summarized as follows:
That is, when θ is taken as an parameter, the machining point locus (Xt, Yt, Zt) and the machined face outward normal locus (nx, ny, nz) are expressed as a function of θ.
&#945;=tan-1 (ny/nx)
Xs=Xr-Tr cos &#952;
Ys=Yr-Tr sin &#952;
In this case, also, where the spindle center Cs is inside the workpiece W as viewed in the Z-axis direction, the equations Xs=Xr-Tr cosθ and Ys=Yr-Tr sinθ are valid, while where the spindle center Cs is outside the workpiece W as viewed in the Z-axis direction, the equations Xs=Xr+Tr cosθ and Ys=Yr+Tr sinθ are valid.
3! Flange face machining
As shown in FIG. 17, when the machining radius at machining start is taken as R0, and the radius increasing rate per revolution of tool is taken as δr, the coordinate positions (Xt, Yt, Zt) of the cutting edge of respective rotational angle positions of the cutting edge, that is, the locus is given, with the rotational angle θ as a function, by the following equations:
Xt={R0 +(&#948;r/2 &#960;)} cos &#952;
Yt={R0 +(&#948;r/2 &#960;)} sin &#952;
Now, δr/2 π is expressed in dR hereinafter.
tx=&#948;Xt/&#948;&#952;=dR cos &#952;-(R0 +dR&#952;) sin &#952;
ty=&#948;Yt/&#948;&#952;=dR sin &#952;-(R0 +dR&#952;) cos &#952;
Since the normal vector facing center n=(nx, ny) is obtained by turning the tangent line vector t by 90�, the normal vector facing center is expressed by the following equations:
nx=-ty=-{dR sin &#952;-(R0 +dR&#952;) cos &#952;}
ny=tx=dR cos &#952;-(R0 +dR&#952;) sin &#952;
&#945;=tan-1 (-ny/-nx)
Then, the machining radius R is determined by the raw material bore size and the machining allowance (step 30); and on the basis of the machining radius R, the spindle center coordinate positions (Xs, Ys, Zs) are calculated by the calculating equations Xs=(R-Tr) cosθ, Ys=(R-Tr) sinθ and Zs=Zt-Tz, respectively, to automatically produce a series of machining pass data, that is, the command data of respective axes X, Y and Z (step 40).
Where the one machining of boring and tapping hole machining causes the dimension to reach a machining completion dimension, the machining is completed (step 60, YES), while where the one machining of boring and tapping hole machining causes the dimension not to reach a machining completion dimension (step 60, NO), the machining radius R is again determined by the current machining diameter and the machining allowance (step 70), and the procedure returns to step 40, at which on the basis of the machining radius R, again the spindle center coordinate positions (Xs, Ys, Zs) are calculated by the calculating equations Xs=(R-Tr) cosθ, Ys=(R-Tr) sinθ and Zs=Zt-Tz, respectively, to automatically produce a series of machining pass data, that is, the command data of respective axes X, Y and Z, and then the boring and tapped hole machining at step 50 are again performed.
Then, the machining radius R is determined by the raw material bore size and the machining allowance (step 130); and on the basis of the machining radius R, the spindle center coordinate positions (Xs, Ys, Zs) are calculated by the calculating equations Xs=(R-Tr) cosθ, Ys=(R-Tr) sinθ and Zs=Zt-Tz, respectively, to automatically produce a series of machining pass data, that is, the command data of respective axes X, Y and Z (step 140).
Where the one machining of boring and tapping hole machining causes the dimension not to reach a roughing completion dimension (step 160, NO), with the current machined diameter and machining allowance, the machining radius R is determined (step 170); and on the basis of the machining radius R, again the spindle center coordinate positions (Xs, Ys, Zs)are calculated by the calculating equations Xs=(R-Tr) cosθ, Ys=(R-Tr) sinθ and Zs=Zt-Tz, respectively, to automatically produce a series of machining pass data, that is, the command data of respective axes X, Y and Z, and then the roughing of a bore with a specified depth, and a tapping hole at step 50 is again performed.
Where the machined diameter reaches a roughing completion dimension (step 160, YES), then the current machined diameter is automatically measured (step 180); with the measured value, an error of the tool diameter of the turning tool 23 is detected, and the machining radius R including a correction value for compensating the tool diameter error is determined so that the finished diameter dimension can be obtained despite of the tool diameter error (step 190); and on the basis of the machining radius R, again the spindle center coordinate positions (Xs, Ys, Zs) are calculated by the calculating equations Xs=(R-Tr) cosθ, Ys=(R-Tr) sinθ and Zs=Zt-Tz, respectively, to automatically produce a series of machining pass data, that is, the command data of respective axes X, Y and Z (step 200).
1! Where cutting edge is rotated on a plane perpendicular to axial line A of machined bore:
In this case, the locus of the cutting edge becomes an ellipse having a major axis in the Y-axis direction as viewed on the X and Y coordinate planes, and the coordinate values (Xt, Yt, Zt) of the cutting edge are expressed, with the angle θ having an original line in the X-axis direction taken as a medium variable, by the following equations:
Xt=R cos &#947;�cos &#952;
Zt=-R sin &#947;�cos &#952;
Xt=R cos &#947;�cos &#952;+i(p/2 &#960;)&#952;
Yt=R sin &#952;+j(p/2 &#960;)&#952;=R sin &#952;
Zt=-R sin &#947;�cos &#952;+k(p/2 &#960;)&#952;
2! Where cutting edge is rotated on a plane perpendicular to Z-axis:
In this case, the locus of the cutting edge becomes an ellipse having a major axis in the X-axis direction as viewed on the X and Y coordinate planes, and the coordinate values (Xt, Yt, Zt) of the cutting edge are expressed, with the angle θ having an original line in the X-axis direction taken as a medium variable, by the following equations:
Xt=R/cos &#947;�cos &#952;
Xt=R/cos &#947;�cos &#952;+i(p/2 &#960;)&#952;
Zt=k(p/2 &#960;)&#952;
3! Where cutting edge is rotated on a plane existing at an intermediate position between a plane perpendicular to the axial line of a machined bore and a plane perpendicular to Z-axis:
In this case, the locus of the cutting edge becomes a true circle as viewed on the X and Y coordinate planes, and the coordinate values (Xt, Yt, Zt) of the cutting edge are expressed, with the angle θ having an original line in the X-axis direction taken as a medium variable, by the following equations:
Zt=-R tan (&#947;/2)�cos &#952;
Xt=R cos &#952;+i(p/2 &#960;)&#952;
Zt=-R tan (&#947;/2)�cos &#952;+k(p/2 &#960;)&#952;
Since the inclined angle γ expressed in cos-1k, cosγ can be replaced with k.
Assuming that the X'-Y'-Z coordinate system is rotationally displaced by δ around Z-axis with respect to the X-Y-Z coordinate system, δ becomes tan-1 (J/i), so that a coordinate system conversion can be executed as follows: ##EQU6##
1! Where cutting edge is rotated on a plane perpendicular to the axial line of a machined bore:
In this case, the coordinate values (X't, Y't, Zt) of the cutting edge on the X' and Y' coordinate planes are expressed, with the angle θ having an original line in the X'-axis direction taken as a medium variable, by the following equations:
X't=R cos &#948;�cos &#952;
Y't=R sin &#952;
Zt=-R sin &#952;�cos &#952;
Xt=R cos &#947;�cos &#948;�cos &#948;-R�sin &#952;�sin &#948;
Yt=R cos &#947;�cos &#952;�sin &#948;+R�sin &#952;�cos &#948;
Xt=R cos &#947;�cos &#948;�cos &#948;-R�sin &#952;�sin &#948;+i(p/2 &#960;)&#952;
Yt=R cos &#947;�cos &#952;�sin &#948;+R�sin &#952;�cos &#948;+j(p/2 &#960;)&#952;
X't=R/cos &#947;�cos &#952;
Xt=R/cos &#947;�cos &#952;�cos &#952;-R�sin &#952;�sin &#948;
Yt=R/cos &#947;�cos &#952;�cos &#948;+R�sin &#952;�cos &#948;
Xt=R/cos &#947;�cos &#952;�cos &#948;-R�sin &#952;�sin &#948;+i(p/2 &#960;)&#952;
Yt=R/cos &#947;�cos &#952;�sin &#948;+R�sin &#952;�cos &#948;+j(p/2 &#960;)&#952;
X't=R cos &#947;
Xt=R cos &#952;�cos &#948;-R�sin &#952;�sin &#948;
Yt=R cos &#952;�sin &#948;+R sin &#952;�cos &#948;
The tangent line vector t at the positions (X=a cosθ, Y=b sinθ) becomes as follows:
tX=dX/d&#952;=-a sin &#952;
tY=dY/d&#952;=+b cos &#952;
tX={-a/(a2 sin2 &#952;+b2 cos2 &#952;)1/2 } sin &#952;
tY={b/(a2 sin2 &#952;+b2 cos2 &#952;)1/2 } cos &#952;
nX=tY={b/(a2 sin2 &#952;+b2 cos2 &#952;)1/2 } cos &#952;
nY=-yX={a/(a2 sin2 &#952;+b2 cos2 &#952;)1/2 } cos &#952;
In this case, as shown in FIG. 28, respective coordinate values (Xp1, Yp1, Zp1), (Xp2, Yp2, Zp2) and (Xp3, Yp3, Zp3) of three points P1, P2 and P3 on a machining datum face Ws of the workpiece W are measured by the use of the automatic measuring instrument 49, and an inclination degree X.sub.γ in the X-axis direction and an inclination degree Y.sub.γ in the Y-axis direction of the machining datum face Ws are calculated by the following equations:
X.sub.&#947; =tan {(Zp2 -Zp1)/(Zx2 -Zx1)
X.sub.&#947; =tan {(Zp3 -Zp1)/(Zx3 -Zx1)
provided that the Y-axis coordinate values are made constant during measurement of the inclination degree X.sub.γ in the X-axis direction, while the X-axis coordinate values are made constant during measurement of the inclination degree .sub.δ in the Y-axis direction.
i=-cos Y.sub.&#947; �sin X.sub.&#947;
j=-cos X.sub.&#947; �sin Y.sub.&#947;
K=cos X.sub.&#947; �cos Y.sub.&#947;
With the equations, the inclined angles γ and δ are expressed by the following equations. It is sufficient that the machining is performed as with the above-mentioned inclined machining.
&#947;=tan-1 {k/(i2 +j2)}
&#948;=tan-1 (j/i)
A turning tool 150 is mounted to a spindle 151 capable of controlling quantitatively the rotational angle around the center axial line itself; the spindle 151 and a workpiece W are allowed to be relatively dislocated by an axial control, in this case, by the X-axis control and the Y-axis control along a plane perpendicular to the rotation axial line of the spindle 151 in such a manner that the relative movement locus of the spindle center Cs to the workpiece W conforms to a geometry to be machined, thereby allowing a true circle mutual interpolation motion between the spindle 151 and the workpiece W to be performed; and the rotational angle of the spindle 151 is synchronously controlled with a required interrelation to the X-axis control and the Y-axis control, whereby the direction of the cutting edge of the turning tool 150 to the inner peripheral face of the workpiece W is kept at a required direction at the full rotational angle position of the spindle 151, that is, a front rake angle β is kept constant, and then the workpiece W is machined into a geometry determined by the interpolation locus (spindle center locus) due to the above-mentioned mutual interpolation motion, that is, into the cross sectional geometry of a true circle.
When a tool radius of the turning tool 150 is taken as Tr, a machining radius of the workpiece W as R, and the front rake angle β as 90�, under a precondition of R>Tr, the spindle center Cs is decentralized by R-Tr from a center Cw of the workpiece W, so that the interpolation locus L becomes a true circle having a radius of R-Tr and the same center as the center Cw of the workpiece W.
The front rake angle β=90� referred to here means for convenience that as viewed through an angle θ around the work piece center Cw taking X-axis as an original line, an angle of the contact position of the cutting edge of the turning tool 150 with the workpiece W is equal to an angle of the position at which the spindle center Cs is positioned on the interpolation locus L.
In this case, the coordinate values of the X-axis control and the Y-axis control are given by trigonometric functional equations having a 90� phase difference mutually with the angle around the workpiece center Cw taken as a medium variable so that the interpolation locus L draws a true circle, and the radius of the interpolation locus L is changed according to the machining radius R of the workpiece W where the front rake angle β is made constant. That is, the machining of an inner peripheral face with an arbitrary machining radius R is performed within a limit of R>Tr by the single turning tool 150 according to the radius of the interpolation locus L.
Then, in the machining of an inner peripheral face with an arbitrary machining radius R, with reference to FIGS. 30A and 30B, a method of changing the front rake angle β of a turning tool will be explained. FIG. 30A shows a case where the front rake angle β is increased to an angle more than 90� by Δβ; FIG. 30B shows a case where the front rake angle β is decreased to an angle less than 90� by Δβ.
Where the machining radius R is made constant, and the front rake angle β is increased or decreased to an angle more than or less than 90�, as viewed through an angle θ around the workpiece center Cw taking X-axis as an original line, the angle of a position at which the spindle center Cs is positioned on the interpolation locus L to the angle of the contact position of the cutting edge of the turning tool 150 with the workpiece W is allowed to change to the lead side or lag side by the angle Δθ corresponding to the increased/decreased angle Δβ of the front rake angle β more than or less than 90�.
With the angle change, an effective tool radius of the turning tool 150 is reduced, so that the radius of the interpolation locus L is increased according to the increased/decreased angle Δβ of the front rake angle β more than or less than 90�.
This allows the boring of an arbitrary inside diameter to be performed by the single turning tool 150 regardless of tool radius, and the front rake angle β to be arbitrarily changed without requiring tool exchange and tool mounting angle change.
Also, in this case, the spindle 151 and a workpiece Ware allowed to be relatively dislocated by the X-axis control and the Y-axis control along a plane perpendicular to the rotation axial line of the spindle 151, thereby allowing a true circle mutual interpolation motion between the spindle 151 and the workpiece W to be performed; and the rotational angle of the spindle 151 is synchronously controlled with a required interrelation to the X-axis control and the Y-axis control, whereby the direction of the cutting edge of the turning tool 150 to the outer peripheral face of the work piece W is kept at a required direction at the full rotational angle position of the spindle 151, that is, the front rake angle β is kept constant, and then the workpiece W is machined into a geometry determined by the interpolation locus due to the above-mentioned mutual interpolation motion, that is, into the cross sectional geometry of a true circle.
Also, in this case, the coordinate values of the X-axis control and the Y-axis control are given by trigonometric functional equations having a 90� phase difference mutually with the angle around the workpiece center Cw taken as a medium variable so that the interpolation locus L draws a true circle, and the radius of the interpolation locus L is changed according to the machining radius R of the workpiece W where the front rake angle β is made constant. That is, the machining of an outer peripheral face with an arbitrary machining radius R is performed by the single turning tool 150 according to the radius of the interpolation locus L.
Then, in the machining of an outer peripheral face with an arbitrary machining radius R, with reference to FIGS. 33A and 33B, a method of changing the front rake angle β of a turning tool will be explained. FIG. 33A shows a case where the front rake angle β is increased to an angle more than 90� by Δβ; FIG. 33B shows a case where the front rake angle β is decreased to an angle less than 90� by Δβ.
Where the machining radius R is made constant, and the front rake angle β is increased or decreased to an angle more than or less than 90�, as with the above-mentioned inner peripheral face machining, as viewed through an angle θ around the workpiece center Cw taking X-axis as an original line, the angle of a position at which the spindle center Cs is positioned on the interpolation locus L to the angle of the contact position of the cutting edge of the turning tool 150 with the workpiece W is allowed to change to the lead side or lag side by the angle Δθ corresponding to the increased/decreased angle Δβ of the front rake angle β more than or less than 90�.
With the angle change, an effective tool radius of the turning tool 150 is reduced, so that the radius of the interpolation locus L is decreased (where the spindle center C sis outside the outer peripheral face of the workpiece) or increased (where the spindle center Cs is inside the outer peripheral face of the workpiece) according to the increased/decreased angle Δβ of the front rake angle β more than or less than 90�.
This allows the outer peripheral face machining of an arbitrary outside diameter to be performed by the single turning tool 150 regardless of tool radius, and the front rake angle β to be arbitrarily changed without requiring tool exchange and tool mounting angle change.
When the radius of the cylindrical face is taken as R; the feed rate in Z-axis direction per revolution, p; and the Z-axis coordinate at Z-axis direction feed start position, Z0 ; the coordinate positions (Xt, Yt and Zt) of the cutting edge at respective rotational angle positions are given by the following functional equation:
Xt=Lr cos &#952;
Yt=Lr sin &#952;
Xs={(R2 +Tr2 -2R�Tr cos &#916;&#946;)1/2 } cos &#952;
Ys={(R2 +Tr2 -2R�Tr cos &#916;&#946;)1/2 } sin &#952;
In this case, by the simultaneous control of two axes X-axis and Y-axis on the basis of the spindle center coordinate positions (Xs, Ys), a mutual circular interpolation motion is performed between the turning tool 150 and the workpiece W, and as the circular interpolation locus, the spindle center locus becomes a true circle having a radius Lr of (R2 +Tr2 -2R�Tr cosΔβ)1/2.
In the cylindrical inner face machining, when a changed angle Δβ from the front rake angle β of 90� is 0, the spindle rotational angle α taking the X-axis direction as an original line is expressed by the following equation: ##EQU9##
Then, the spindle rotational angle α is changed by an angle Δθ according to the changed angle Δβ from the front rake angle β of 90�. That is, α becomes θ+π�Δθ.
With the above-mentioned condition satisfied, the axial control of respective axes of X, Y and Z is performed, and the spindle rotational angle α is synchronously controlled with the axial control, whereby the turning tool 150 performs the cylindrical inner face machining of an arbitrary radius R taking the tool radius Tr as a minimum radius with an arbitrary front rake angle β to a machined face at the full rotational angle position of the spindle 151.
This allows the inner peripheral face machining of an arbitrary radius to be performed by the single turning tool 150 regardless of tool radius, and the front rake angle β to be arbitrarily changed without requiring tool exchange and tool mounting angle change.
Xs={(R2 +Tr2 +2R�Tr cos &#916;&#946;)1/2 } cos &#952;
Ys={(R2 +Tr2 +2R�Tr cos &#916;&#946;)1/2 } sin &#952;
In the cylindrical outer face machining, when a changed angle Δβ from the front rake angle β of 90� is 0, the spindle rotational angle a taking the X-axis direction as an original line is expressed by the following equation:
Accordingly, as with the inner peripheral face machining, the axial control of respective axes X, Y and Z is performed, and with the axial control, the axis rotational angle α is synchronously controlled, whereby also in this case, the turning tool 150 performs the cylindrical outer face machining of an arbitrary radius R with an arbitrary front rake angle β to a machined face at the full rotational angle position of the spindle 151.
This allows the outer peripheral face machining of an arbitrary radius to be performed by the single turning tool 150 regardless of tool radius, and the front rake angle β to be arbitrarily changed without requiring tool exchange and tool mounting angle change.
The equations of Xs={(R2 +Tr2 +2R�Tr cosΔβ)1/2 } cosθ and Ys={(R2 +Tr2 +2R�Tr cosΔβ)1/2 } sinθ become valid in a case where the spindle center Cs is outside the workpiece W as viewed in the Z-axis direction as shown in FIG. 31, while in a case where the spindle center Cs is inside the workpiece W as viewed in the Z-axis direction as shown in FIG. 32, the equations of Xs ={(R2 +Tr2 -2R�Tr cosΔβ)1/2 } cosθ and Ys={(R2 +Tr2 -2R Tr2 cosΔβ)1/2 } sinθ become valid.
This allows the thread cutting of internal thread or external thread having an arbitrary thread diameter to be performed by the single turning tool 150 regardless of tool radius, and the front rake angle β to be arbitrarily changed without requiring tool exchange and tool mounting angle change.
For machining of Z-axis rotating material having a diameter change in the Z-axis direction, such as taper machining, when the radius Lr of the interpolation locus L is taken as a function fLr (z) with respect to Z; the feed rate in the Z-axis direction per revolution, p; and the Z-axis coordinate of the feed start position in the Z-axis direction, Z0, it is sufficient to change the radius Lr of the interpolation locus L with a function of fLr{Z0 -(p/2 π)θ}.
It is sufficient that the spindle rotational angle α is the same as with the above-mentioned cylindrical inner/outer face machining. Also, in this case, the machining of Z-axis rotating material having a diameter arbitrarily changing in the Z-axis direction is performed by the single turning tool 150 with an arbitrary front rake angle.
This allows the machining of Z-axis rotating material having a diameter arbitrarily changing in the Z-axis direction to be performed by the single turning tool 150 regardless of tool radius, and the front rake angle β to be arbitrarily changed without requiring tool exchange and tool mounting angle change.
A turning tool 250 has a bar part 252, and the head of the bar part 252 is mounted with four cutting edges of a roughing cutting edge 254, a finishing cutting edge 258 and double chamfering cutting edges 258, 280 radially at a phase angle of 90� mutually with the center axial line of the bar part 252 as a center.
The spindle 266 is mounted with a key 270, and the key 270 engages with a positioning key groove 272 formed in the ATC engaging groove 262 to perform the rotation rocking and positioning in the rotational direction of the turning tool 250. The positioning key groove 272 is formed at a position at which the groove is displaced by 90� with respect to the roughing cutting edge 254.
The above-mentioned key engagement causes the turning tool 250 to be unconditionally positioned and mounted to the spindle 266 in the rotational direction, and where the spindle 266 is positioned at the zero point, the roughing cutting edge 254 is positioned at a position rotationally displaced by 90� from the zero point as shown in FIG. 36.
In the machining by the spindle rotational angle control machining method according to the present invention, the spindle 266 and the workpiece W are allowed to be relatively dislocated by an axial control, in this case, by the X-axis control and the Y-axis control along a plane perpendicular to the rotation axial line of the spindle 266 in such a manner that the relative movement locus of the spindle center Cs to the workpiece W conforms to a geometry to be machined, thereby allowing a true circle mutual interpolation motion between the spindle 266 and the workpiece W to be performed; and the rotational angle of the spindle 266 is synchronously controlled with a required interrelation to the X-axis control and the Y-axis control, whereby the direction of the cutting edge of the turning tool 250 to the inner peripheral face of the workpiece W is kept at a required direction at the full rotational angle position of the spindle 266, in the illustrated example, a front rake angle β (see FIG. 37) between the roughing cutting edge 254 and the inner peripheral face is kept constant, and then the roughing cutting edge 254 roughs the inner peripheral face of the workpiece W into a geometry determined by the interpolation locus (spindle center locus) due to the above-mentioned mutual interpolation motion (see FIG. 37), that is, into the cross sectional geometry of a true circle.
When the rotational angle of the spindle 266 is allowed to move forward 180� by the synchronous control of the X-axis control with the Y-axis control from a state shown In FIG. 37, the finishing cutting edge 256 keeps the angle β constant to the inner peripheral face of the workpiece W, and instead of the roughing cutting edge 254, the finishing cutting edge 256 finishes the inner peripheral face of the workpiece W into a true circle cross-sectional geometry determined by the spindle center locus L due to the above-mentioned mutual interpolation motion.
When the rotational angle of the spindle 266 is allowed to move forward 90� or 270� by the synchronous control of the X-axis control with the Y-axis control from a state shown In FIG. 37, the chamfering cutting edge 258 or 260 keeps the angle β constant to the chamfered face of the workpiece W, and the chamfering cutting edge 258 or 260 performs chamfering of the workpiece W into a true circle cross-sectional geometry determined by the spindle center locus L due to the above-mentioned mutual interpolation motion.
The turning tool 250 may be have the same configuration as for inner peripheral face machining, and the head of the bar part 252 is mounted with four cutting edges of a roughing cutting edge 254, a finishing cutting edge 256 and double chamfering cutting edges 258, 260 radially at a phase angle of 90� mutually with the center axial line of the bar part 252 as a center.
Also, in this case, the spindle 266 and the workpiece W are allowed to be relatively dislocated by the X-axis control and the Y-axis control along a plane perpendicular to the rotation axial line of the spindle 266, thereby allowing a true circle mutual interpolation motion between the spindle 266 and the workpiece W to be performed; and the rotational angle of the spindle 266 is synchronously controlled with a required interrelation to the X-axis control and the Y-axis control, whereby the direction of the cutting edge of the turning tool 250 to the inner peripheral face of the workpiece W is kept at a required direction at the full rotational angle position of the spindle 266, and in the illustrated example, the front rake angle β between the roughing cutting edge 254 and the inner peripheral face is kept constant, and then the roughing cutting edge 254 roughs the outer peripheral face of the workpiece W into a geometry determined by the interpolation locus due to the above-mentioned mutual interpolation motion, that is, into the cross sectional geometry of a true circle.
When the rotational angle of the spindle 266 is allowed to move forward 180� by the synchronous control of the X-axis control with the Y-axis control from a state shown In FIG. 38, the finishing cutting edge 256 keeps the angle β constant to the inner peripheral face of the workpiece W, and instead of the roughing cutting edge 254, the finishing cutting edge 256 finishes the outer peripheral face of the workpiece W into a true circle cross-sectional geometry determined by the spindle center locus L due to the above-mentioned mutual interpolation motion.
When the rotational angle of the spindle 266 is allowed to move forward 90� or 270� by the synchronous control of the X-axis control with the Y-axis control from a state shown In FIG. 38, the chamfering cutting edge 258 or 260 keeps the angle β constant to the chamfered face of the workpiece W, and the chamfering cutting edge 258 or 260 performs chamfering of the workpiece W into a true circle cross-sectional geometry determined by the spindle center locus L due to the above-mentioned mutual interpolation motion.
In the cylindrical inner face machining, the spindle rotational angle α taking the X-axis direction as an original line is expressed by the following equation: ##EQU10##
In the equation, γ is a cutting edge selection angle, and in the illustrated example, the chamfering cutting edge 258 is selected with γ=0 degree; the roughing cutting edge 254, with γ=90 degrees; the chamfering cutting edge 260, with γ=180 degrees; and the finishing cutting edge 256, with γ=270 degrees.
With the above-mentioned condition satisfied, the axial control of respective axes X, Y and Z is performed, and the spindle rotational angle α is synchronously controlled with the axial control, whereby a single cutting edge 254, 256, 258 or 260 selected by setting of the cutting edge selection angle γ becomes faced always to the normal with respect to machined face at the full rotational angle position of the spindle 266, so that a cylindrical inner face machining with an arbitrary radius R is performed by the single cutting edge selected by setting of the cutting edge selection angle γ.
Xs=Xt+nx�Tr=R cos &#952;+Tr cos &#952;=(R+Tr) cos &#952;
In the cylindrical outer face machining, the spindle rotational angle α taking the X-axis direction as an original line is expressed by the following equation: ##EQU11##
Accordingly, as with the cylindrical inner face machining, with the above-mentioned condition satisfied, the axial control of respective axes X, Y and Z is performed, and the spindle rotational angle α is synchronously controlled with the axial control, whereby a single cutting edge 254, 256, 258 or 260 selected by setting of the cutting edge selection angle γ becomes faced always to the normal with respect to machined face at the full rotational angle position of the spindle 266, so that a cylindrical outer face machining with an arbitrary radius R is performed by the single cutting edge selected by setting of the cutting edge selection angle γ.
The equations of Xs=(R+Tr) cos θ and Ys=(R+Tr) sin θ become valid in a case where the spindle center Cs is outside the workpiece W as viewed in the Z-axis direction as shown in FIG. 38, while in a case where the spindle center Cs is inside the workpiece W as viewed in the Z-axis direction, the equations of Xs=(R-Tr) cosθ and Ys=(R-Tr) sinθ become valid.
As shown in FIGS. 42 and 43, when the radius of the cylindrical face is taken as R; the feed rate in Z-axis direction per revolution, p; and the Z-axis coordinate at Z-axis direction feed start position, Z0 ; the coordinate positions (Xt, Yt and Zt) of the cutting edge at respective rotational angle positions are given by the following functional equation:
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