Machine tool

Abstract

A machine tool includes a linear movement axis for moving a main spindle, at least two linear movement axes for moving a table, and a rotation table including at least one rotation axis, the rotation table being placed on the table. A numerical controller performs machining by executing a machining program for tool center point control where the tool orientation is fixed to a certain axis or a certain surface, and by changing the tool orientation by controlling each axis of the machine tool based on set tool use range and tool orientation change waveform pattern.

Claims

1. A machine tool comprising: a linear movement axis for moving a main spindle; at least two linear movement axes for moving a table; a rotation table including at least one rotation movement axis, the rotation table being placed on the table; and a numerical controller for controlling the main spindle, the linear movement axes, and the rotation movement axis according to a machining program in which tool orientation is fixed, and for machining a workpiece fixed to the rotation table, wherein the numerical controller includes a tool shape information storage section for storing tool shape information to be used, a reference machining orientation tool diameter storage section for storing a reference machining orientation tool diameter of a tool to be used in execution of the machining program in which tool orientation is fixed, a tool orientation change waveform storage section for storing a tool orientation change waveform pattern and the number of repetitions for periodically changing a tool orientation of the tool to be used in execution of the machining program, a machining direction vector storage section for storing a machining direction vector instructed by the machining program, a movement axis instruction storage section for reading the machining program and storing movement axis instructions for the linear movement axes and the rotation movement axis, a total machining height calculation section for calculating a total machining height for changing the tool orientation from the machining direction vector and the movement axis instruction, a movement axis instruction value calculation section for calculating, by a tool center point control function, a movement axis instruction value for each of the linear movement axes and the rotation movement axis, which are movement axes, based on the movement axis instruction, a movement axis instruction value addition amount calculation section for calculating an addition amount to each movement axis instruction value for changing the tool orientation, based on the tool shape information, the reference machining orientation tool diameter, the tool orientation change waveform, and the total machining height, a movement axis instruction value adding section for adding the addition amount calculated by the movement axis instruction value addition amount calculation section to each movement axis instruction value calculated by the movement axis instruction value calculation section, and a control section for performing operation according to each movement axis instruction value to which the addition amount is added by the movement axis instruction value adding section.

2. The machine tool according to claim 1, wherein the machining direction vector is an element for determining an axis direction of the tool orientation change waveform in the changing of the tool orientation.

3. The machine tool according to claim 1, wherein the total machining height is an element for determining a range of the tool orientation change waveform in the changing of the tool orientation.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The above-described and other objects and features of the present invention will be made clear from the description of the embodiment given below with reference to the appended drawings. Of these drawings:

(2) FIGS. 1A and 1B are diagrams showing machining of a turbine blade, wherein FIG. 1A shows the shape of a turbine blade, and FIG. 1B is a diagram for describing the machining path in the turbine blade machining;

(3) FIGS. 2A and 2B are diagrams concretely showing the tool orientation with respect to a machined surface, wherein FIG. 2A is side view regarding a tool orientation and a diagram showing the tool orientation (a lead angle) in an enlarged manner, and FIG. 2B is plan view regarding a tool orientation and a diagram showing the tool orientation (a tilt angle) in an enlarged manner;

(4) FIG. 3 is a diagram showing, with respect to the turbine blade machining shown in FIG. 1, machining at a tool orientation that is fixed with respect to the machined surface (a diagram showing the machining path from the front), and a diagram showing a part of the machining path in an enlarged manner;

(5) FIG. 4 is a diagram for describing a method of machining while changing the tool orientation (tool orientations 80°, 45°, 10°);

(6) FIG. 5 is a diagram for describing a change in the cutting speed in machining where the tool orientation is changed with respect to the machined surface in the turbine blade machining shown in FIG. 1;

(7) FIGS. 6A and 6B are diagrams for describing a change in the machining conditions where the cutting speed is constant;

(8) FIG. 7 is a diagram showing a barrel tool;

(9) FIGS. 8A to 8C are diagrams for describing a method of machining that is performed using a barrel tool and while changing the tool orientation;

(10) FIG. 9 is a perspective view of the appearance of an embodiment of a machine tool according to the present invention;

(11) FIG. 10 is an enlarged partial view of FIG. 9;

(12) FIGS. 11A and 11B are diagrams showing examples of results of calculation of a change in the tool orientation with respect to FIGS. 13A to 13D, and FIG. 14;

(13) FIG. 12 is a diagram for describing the calculation results in FIGS. 11A and 11B in detail;

(14) FIG. 13A is a diagram showing an example program format;

(15) FIG. 13B is a diagram showing an example program instruction;

(16) FIG. 13C is a diagram showing the orientation of a barrel tool;

(17) FIG. 13D is a diagram showing barrel tool dimensions;

(18) FIG. 14 is a diagram showing a tool use range and a tool orientation change waveform;

(19) FIG. 15 is a flow chart showing a process of performing machining by controlling the machine tool of the present invention and changing the tool orientation;

(20) FIG. 16 is a diagram for describing a calculation formula for calculating an addition amount for each movement axis instruction; and

(21) FIG. 17 is a block diagram of a numerical controller for controlling the machine tool according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(22) An embodiment of a machine tool according to the present invention will be described with reference to FIG. 9 (perspective view of appearance) and FIG. 10 (enlarged partial view).

(23) A machine tool 20 is configured from a bed 21, a column 24 that is arranged at the back of the bed 21 in a standing manner, a table 22 placed at the center of the bed 21, a rotation table 23 that is placed on the table 22 and that is capable of rotating around two axes, a main spindle head 25 attached at the upper portion of the column 24, and a main spindle 26 that is fixed to the main spindle head 25. A barrel tool 8 is attached to the main spindle 26. The barrel tool 8 is rotated by a motor. The main spindle head 25 is capable of moving in a vertical direction along a linear movement axis (Z-axis).

(24) The table 22 is capable of moving along two linear movement axes (X-axis, Y-axis). Also, the rotation table 23 placed on the table 22 is capable of rotating around two rotation axes (B-axis, C-axis). Each axis of the machine tool is controlled by a numerical controller (not shown), and machining of a workpiece 27 (for example, machining of a turbine blade) is carried out.

(25) In the machining of a turbine blade by the machine tool of the present invention, the barrel tool 8 is used instead of a ball end mill so as to provide a practical machining method. In this case, if machining is performed by using a machining program for tool center point control based on a certain tool orientation, the cut range is wide due to the shape property of the barrel tool 8, and thus there is a problem of accumulation of cutting heat, which is a cause of reduction in the tool life. As shown in FIGS. 11A and 11B, as a method of dissipating the cutting heat, the tool contact position is changed by changing, within a range set in advance, the orientation of the tool that is used in order to dissipate the cutting heat that to be generated. Accumulation of the cutting heat in the barrel tool 8 is thereby prevented. Additionally, FIGS. 11A and 11B are diagrams showing examples of a calculation result of a change in the tool orientation in FIGS. 13A to 13D and FIG. 14. Also, FIG. 12 is a diagram for describing the calculation results in FIGS. 11A and 11B in detail.

(26) To realize the machining described above, the machine tool 20 changes, by a numerical controller 29 (see FIG. 17) for executing the machining program for tool center point control based on a certain tool orientation, the tool orientation of the barrel tool 8 based on set tool use range and tool orientation change waveform pattern, and thus it is possible to increase the life of a tool to be used in the machining of a turbine blade whose main material is a heat-resistance alloy, such as a nickel-based alloy, by simple operation and setting.

(27) FIG. 13A is a diagram showing an example program format.

(28) A program format function ON (101) for starting control of the machine tool according to the present invention is expressed by an M code “M303”, and instructions are given by R, D, B, S, E, V, W, and K as arguments. Each argument is described as follows: R is a barrel radius, D is a tool diameter, B is a reference machining orientation tool diameter, S is a tool use range (start), E is a tool use range (end), V is a machining direction vector, W is a tool orientation change waveform pattern, and K is the number of times of orientation change.

(29) FIG. 13B is a diagram showing an example program instruction.

(30) A machining program (O1000) 9 for performing control of the machine tool according to the present invention includes the program format function ON (101), a machining path program 10, and a program format function OFF (102).

(31) FIG. 13C is a diagram showing the orientation of a barrel tool, and FIG. 13D is a diagram showing barrel tool dimensions.

(32) Tool shape information of the barrel tool 8 includes the barrel radius R, the tool diameter D, the tool use range (start) S, and the tool use range (end) E, as shown in FIG. 13D. The reference machining orientation tool diameter B is a reference tool diameter when the tool orientation is constant. These pieces of information are stored, at the time of execution of the machining program 9, in a storage device provided to the numerical controller for controlling a machine tool. Additionally, the reference sign d1 in FIG. 13D indicates a reference tool diameter when the tool orientation is constant, and the reference sign p1 indicates a machining path program instruction position.

(33) FIG. 14 is a diagram showing a tool use range and a tool orientation change waveform.

(34) In the machining by the machine tool according to the present invention, the barrel tool 8 machines the workpiece 27 while having the tool orientation changed within the range from the tool use range (start) S to the tool use range (end) E. Patterns of change in the orientation of the barrel tool 8 includes two types of a linear orientation change pattern instructed by W=1, and a sine-wave orientation change pattern instructed by W=2. The number of times the barrel tool 8 is to change the orientation between the tool use range (start) S and the tool use range (end) E is instructed by the number of times of orientation change K. In FIG. 14, (a) shows a case where the number of times of orientation change is one (K=1), and (b) shows a case where the number of times of orientation change is two (K=2).

(35) As shown in FIG. 13B, the M303 instruction, which is the “program format function ON (101)” to be instructed before the “machining path program (10)” in the machining program 9, is issued with the arguments of the barrel radius R, the tool diameter D, the reference machining orientation tool diameter B, the tool use range (start) S, the tool use range (end) E, the machining direction vector V, the tool orientation change waveform pattern W, and the number of times of orientation change K, and then after the “machining path program (10)”, an M305 instruction, which is the “program format function OFF (102)”, is issued.

(36) FIG. 15 is a flow chart showing a process of performing machining by controlling the machine tool of the present invention and changing the tool orientation.

(37) The arguments are stored in the numerical controller (step sa02) by the M303 (step sa01), which is the “program format function ON (101)”. The arguments to be stored are the barrel radius R, the tool diameter D, the reference machining orientation tool diameter B, the tool use range (start) S, the tool use range (end) E, the machining direction vector V, the tool orientation change waveform pattern W, and the number of times of orientation change K.

(38) Next, all of the “machining path program (10)” up to the M305, which is the “program format function OFF (102)”, is read (step sa03).

(39) Next, a total machining height H is calculated by Expression (1) below based on the maximum value H.sub.MAX of machining height and the minimum value H.sub.MIN of machining height in the “machining path program (10)” read based on the machining direction vector V (step sa04). Expressions (2), (3), and (4) below are expressions for determining the total machining heights where the machining direction vectors are V=1, 2, and 3. In this case, V=1 corresponds to the X-axis, V=2 to the Y-axis, and V=3 to the Z-axis.
H=H.sub.MAX−H.sub.MIN  (1)

(40) In the case of the machining direction vector V=1,
H=X.sub.MAX−X.sub.MIN  (2).

(41) In the case of the machining direction vector V=2,
H=Y.sub.MAX−Y.sub.MIN  (3).

(42) In the case of the machining direction vector V=3,
H=Z.sub.MAX−Z.sub.MIN  (4).

(43) The accumulated number of times of orientation change is given as Kc, where Kc=k (k=1, 2, 3, . . . , n), and its initial value is one.

(44) Next, argument error check based on the number of times of orientation change K (step sa05), and argument error check based on the tool orientation change waveform pattern W (steps sa07, sa10) are performed. Also, the initial value of the accumulated number of times of orientation change Kc is given as one. In the case where the result of the argument error check indicates an argument error, an error is output (step sa06).

(45) In the case where the tool orientation change waveform pattern W is one (step sa07), a machining operation is started by the “machining path program (10)” (step sa08), and a contact tool outer diameter Dc is calculated from a machining height instruction value Hi (step sa09). The machining height instruction value Hi at this time is determined by a linear movement axis instruction that is read based on the machining direction vector V. A machining position Hp is calculated based on the machining height instruction value Hi between the maximum value H.sub.MAX of machining height and the minimum value H.sub.MIN of machining height on the linear movement axis which has been read. Additionally, as shown in FIG. 14, with respect to the contact tool outer diameter Dc, there are two types of the tool orientation change waveform patterns W, namely, the linear orientation change pattern and the sine-wave orientation change pattern.

(46) In the case of the tool orientation change waveform pattern W=1 (linear orientation change pattern), the contact tool outer diameter Dc is calculated from the machining height instruction value Hi in step sa09.

(47) In the case of the machining direction vector V=1, the machining height instruction value Hi is calculated by Expression (5) below.
H.sub.i=X.sub.i  (5)

(48) In the case of the machining direction vector V=2, the machining height instruction value Hi is calculated by Expression (6) below.
H.sub.i=Y.sub.i  (6)

(49) In the case of the machining direction vector V=3, the machining height instruction value Hi is calculated by Expression (7) below.
H.sub.i=Z.sub.i  (7)

(50) The machining position Hp is calculated by Expression (8) below.
H.sub.p=H.sub.MAX−H.sub.i  (8) (i=MAX, 1, 2, 3 . . . , MIN)

(51) The contact tool outer diameter Dc is calculated by Expression (9) below.

(52) $\begin{array}{cc}{D}_c=S+\left(\left(E-S\right)-.Math.2\left(E-S\right)\left(\frac{H_P}{H}K-\left(K_c-1\right)\right)-\left(E-S\right).Math.\right)& \left(9\right)\end{array}$

(53) In the case of the tool orientation change waveform pattern W=2 (sine-wave orientation change pattern) (step sa10), the contact tool outer diameter Dc is calculated from the machining height instruction value Hi in step sa11.

(54) In the case of the machining direction vector V=1, the machining height instruction value Hi is calculated by Expression (5).

(55) In the case of the machining direction vector V=2, the machining height instruction value Hi is calculated by Expression (6).

(56) In the case of the machining direction vector V=3, the machining height instruction value Hi is calculated by Expression (7).

(57) The machining position Hp is calculated by Expression (8).

(58) The contact tool outer diameter Dc is calculated by Expression (10) below.

(59) $\begin{array}{cc}{D}_c=S+\frac{\left(E-S\right)}{2}\left(1+\sin \left(360\times \left(\frac{H_P}{H}K-\left(K_c-1\right)\right)\right)\right)& \left(10\right)\end{array}$

(60) Each movement axis instruction value is calculated by a tool center point control function (step sa13), and a tilt axis addition value θ.sub.T, a first movement axis addition value V.sub.1, and a second movement axis addition value V.sub.2 are calculated based on the contact tool outer diameter Dc calculated in step sa09 or sa12, by Expressions (11) to (26) below, from the tool position and the tilt angle that change based on the value of the contact tool outer diameter Dc (step sa14). The addition values calculated are added to respective movement axis instruction values (step sa15), and each axis of the machine is operated by each movement axis instruction value to which the addition amount is added (step sa16).

(61) Repetition is determined based on the ratio of the number of times of orientation change K and the accumulated number of times of orientation change Kc, and the ratio of the machining position Hp and the machining height instruction value H, and the tool orientation change waveform pattern is repeated by the set number of times of orientation change K (steps sa17 to sa20).

(62) For example, as shown in FIGS. 11A and 11B, in the case of a machining program with a machining path program where the tool orientation is made constant at a φ7.0 position where a φ8.0 barrel tool is used, if φ6.0 to φ8.0 is given as the tool orientation range, the machining position is calculated by the flow chart shown in FIG. 15 and Expressions (11) to (26) below.

(63) In Expressions (14) to (24) below, the addition values (the addition amounts) that change depending on the contact tool outer diameter Dc are given as a first movement axis tool position addition value V.sub.1A, and a second movement axis tool position addition value V.sub.2A, and the addition values (the addition amounts) according to the angle change calculated from the contact tool outer diameter Dc and the reference machining orientation tool diameter B are given as a first movement axis angular position addition value V.sub.1B, and a second movement axis angular position addition value V.sub.2B.

(64) Additionally, in FIG. 16, the reference sign w1 indicates a workpiece contact point, p1 indicates a machining path program instruction position, and p2 indicates a new machining path program instruction position.

(65) These two types of addition values (V.sub.1A, V.sub.2A, V.sub.1B, V.sub.2B) are determined by Expressions (11) to (24) based on tool information stored by the M303, which is the “program format function ON (101)”, and the first movement axis addition value V.sub.1 and the second movement axis addition value V.sub.2 are calculated by Expressions (25) and (26) using the two types of addition values (addition amounts).

(66) A contact tool outer diameter angle θ.sub.Dc is calculated by Expression (11) below.

(67) $\begin{array}{cc}{\theta }_{D_c}={\cos }^{-1}\left(1-\frac{D-D_c}{2R}\right)& \left(11\right)\end{array}$

(68) A reference machining orientation tool outer diameter angle θ.sub.B is calculated by Expression (12) below.

(69) $\begin{array}{cc}{\theta }_B={\cos }^{-1}\left(1-\frac{D-D}{2R}\right)& \left(12\right)\end{array}$

(70) θ.sub.T is calculated by Expression (13) below.
θ.sub.T=θ.sub.B−θ.sub.D.sub.c  (13)

(71) A total length L is calculated by Expression (14) below.

(72) $\begin{array}{cc}L=\sqrt{R^2-{\left(R-\left(\frac{D-S}{2}\right)\right)}^2}& \left(14\right)\end{array}$

(73) A reference length L.sub.B is calculated by Expression (15) below.

(74) $\begin{array}{cc}{L}_B=L-\sqrt{R^2-{\left(R-\left(\frac{D-B}{2}\right)\right)}^2}& \left(15\right)\end{array}$

(75) A reference radius R.sub.B is calculated by Expression (16) below.

(76) $\begin{array}{cc}{R}_B=\sqrt{L_B^2+{\left(\frac{B}{2}\right)}^2}& \left(16\right)\end{array}$

(77) A reference angle α.sub.B is calculated by Expression (17) below.

(78) $\begin{array}{cc}{\alpha }_B={\tan }^{-1}\left(\frac{2L_B}{B}\right)& \left(17\right)\end{array}$

(79) A changed length L.sub.Dc is calculated by Expression (18) below.

(80) $\begin{array}{cc}{L}_{D_c}=L-\sqrt{R^2-{\left(R-\left(\frac{D-D_c}{2}\right)\right)}^2}& \left(18\right)\end{array}$

(81) A changed radius R.sub.Dc is calculated by Expression (19) below.

(82) 0$\begin{array}{cc}{R}_{D_c}=\sqrt{L_{D_c}^2+{\left(\frac{D_c}{2}\right)}^2}& \left(19\right)\end{array}$

(83) A changed angle α.sub.Dc is calculated by Expression (20) below.

(84) $\begin{array}{cc}{\alpha }_{D_c}={\tan }^{-1}\left(\frac{2L_{D_c}}{D_c}\right)& \left(20\right)\end{array}$

(85) The first movement axis tool position addition value V.sub.1A is calculated by Expression (21) below.
V.sub.1A=R.sub.B×cos(α.sub.B+θ.sub.B)−R.sub.D.sub.c×cos(α.sub.D.sub.c+θ.sub.B)  (21)

(86) The second movement axis tool position addition value V.sub.2A is calculated by Expression (22) below.
V.sub.2A=R.sub.B×sin(α.sub.B+θ.sub.B)−R.sub.D.sub.c×sin(α.sub.D.sub.c+θ.sub.B)  (22)

(87) The first movement axis angular position addition value V.sub.1B is calculated by Expression (23) below.
V.sub.1B=R.sub.D.sub.c×cos(α.sub.D.sub.c+θ.sub.B)−R.sub.D.sub.c×cos(α.sub.D.sub.c+θ.sub.D.sub.c)  (23)

(88) The second movement axis angular position addition value V.sub.2B is calculated by Expression (24) below.
V.sub.2B=R.sub.D.sub.c×sin(α.sub.D.sub.c+θ.sub.B)−R.sub.D.sub.c×sin(α.sub.D.sub.c+θ.sub.D.sub.c)  (24)

(89) V.sub.1 is calculated by Expression (25) below.
V.sub.1=V.sub.1A+V.sub.1B  (25)

(90) V.sub.2 is calculated by Expression (26) below.
V.sub.2=V.sub.2A+V.sub.2B  (26)

(91) In the examples of calculation of a change in the tool orientation shown in FIGS. 11A and 11B, the machine tool 20 (see FIGS. 9 and 10) includes three linear movement axes, X-axis, Y-axis and Z-axis, and two rotation axes, B-axis and C-axis, with the B-axis being a tilt axis that is parallel to the Y-axis direction and the C-axis being a rotation axis that is parallel to the Z-axis direction, where the rotation is in the clockwise direction for both axes.

(92) The numerical controller for controlling the machine tool according to the present invention will be described with reference to FIG. 17.

(93) The machining program 9 is analyzed by an analysis section 30 and is interpolated by an interpolation section 31, and servos 50x, 50y, 50z, 50b, and 50c of respective axes of the machine tool are driven. The interpolation section 31 calculates, by the tool center point control function, the movement axis instruction value of each movement axis (linear movement axes, rotation movement axis) based on a movement axis instruction issued by the machining program 9.

(94) A storage unit 32 includes a tool shape information storage section 33 for storing tool shape information to be used, the tool shape information being acquired by analysis of the machining program 9 by the analysis section 30, a reference machining orientation tool diameter storage section 34 for storing the contact tool diameter of a tool to be used in relation to a machining program in which tool orientation is fixed, a tool orientation change waveform storage section 35 for storing the tool orientation change waveform pattern and the number of repetitions for periodically changing the tool orientation of the tool to be used in execution of the machining program 9, a machining direction vector storage section 36 for storing a machining direction vector instructed by the machining program 9, and a movement axis instruction storage section 37 for reading the machining program 9 and storing movement axis instructions for the linear movement axes and the rotation movement axis.

(95) A total machining height calculation section 38 calculates a total machining height for changing the tool orientation from the machining direction vector stored in the machining direction vector storage section 36 and the movement axis instruction stored in the movement axis instruction storage section 37. A movement axis instruction value addition amount calculation section 39 calculates the addition amount to each movement axis instruction value for changing the tool orientation, based on the tool shape information stored in the tool shape information storage section 33, the contact tool diameter stored in the reference machining orientation tool diameter storage section 34, the tool orientation change waveform stored in the tool orientation change waveform storage section 35, and the total machining height output from the total machining height calculation section 38. A movement axis instruction value addition amount adding section 40 adds the addition amount calculated by the movement axis instruction value addition amount calculation section 39 to each movement axis instruction value calculated by a movement axis instruction value calculation section (the interpolation section 31).

(96) Each movement axis instruction value determined by the movement axis instruction value addition amount adding section 40 drives a driving section (a servomotor) of the machine tool by each axial servo (the X-axis servo 50x, the Y-axis servo 50y, the Z-axis servo 50z, the B-axis servo 50b, the C-axis servo 50c), which is a control section for controlling the operation.

(97) As described above, according to the present invention, it is possible to prevent accumulation of cutting heat and to increase the tool life by causing a numerical controller for controlling a machine tool to perform machining by changing the tool orientation (changing the tool contact position based on a certain waveform), by storing, based on a machining program in which the tool orientation is fixed to a certain axis or a certain surface, a machining program track, the barrel radius R of a barrel tool to be used, the reference tool diameter D, the reference machining orientation tool diameter B, the tool use range, the machining direction vector V, the tool orientation change waveform pattern W, and the number of times of orientation change K, calculating the machining position at the time of changing the tool orientation based on the stored pieces of information, and performing an operation by adding the calculated result to each movement axis instruction.