Machining a workpiece in a turret lathe and an NC lathe therefor

Abstract

A method of Apparatus for machining a workpiece, which is rotatable about a first axis, by a tool pivotable about a second axis parallel to the first axis and drivable about a third axis perpendicular to the second axis. To allow the circumference of the workpiece to be machined off-center without the necessity of moving the first or the second axis transversely to the plane defined by these two axes, the workpiece and the tool are rotated or pivoted about the first or and second axis axes, respectively, at the same time, in the same direction and at the same angular velocity and, simultaneously the second axis is displaced transversely to the first axis at such a velocity that the equation X² =Y² +A² always applies, wherein X is the distance of the second axis from the first axis, Y is the distance of the first axis from the plane defined by the second and third axes and A is the distance of the second axis from the vertical projection of the first axis on this plane.

Description

This is A Assuming a constant feed velocity v_y of the milling tool 56 in the plane of the flat surface 116 to be produced, relative to the workpiece 22, results when the following always applies: ##EQU1## wherein γ equals the angle between the tool axis 160 and the plane defined by the main spindle axis 16 and the turret axis 42 or rather between this plane and the perpendicular to the flat surface 116 to be made, Y_o is the value of Y at which the milling tool touches the workpiece for the first time and t is the time which is equal to zero when Y=Y_σ.

As shown in FIG. 3, rotation of the workpiece 22 along the C-axis, i.e. about the main spindle axis 16, in conjunction with a simultaneous pivoting of the milling tool in the same direction about the turret axis 43 42 leads to a feed motion of the tool relative to the workpiece which corresponds to a feed motion in the direction of the Y-axis (see FIG. 2).

FIG. 4 again shows the bore 118 indicated in FIG. 5, the axis of which is spaced from the main spindle axis. The bore can be drilled in that the workpiece 22 is rotated with the aid of the main spindle 14 about the main spindle axis 16 in the direction of the arrow, the upper carriage 38 is moved simultaneously towards the main spindle axis 16 with the drill bit 58 in operation and the drill bit 58 is pivoted about the turret axis 42 simultaneously and in the same direction as the rotational movement of the workpiece 22 and at the same angular velocity, the rotational or pivoting movement thereby being controlled such that the following always applies: ##EQU2## A Assuming a constant feed velocity v_A of the drill bit 58 relative to the workpiece 22 results when the following always applies: wherein A₀ is the value of A at which the drill bit touches the workpiece for the first time and t is the time which is equal to zero when A=A₀.

This again shows quite clearly that a rotational movement of the workpiece 22 about the main spindle axis 16 (C-axis movement) and a corresponding pivoting movement of the tool about the turret axis 42 achieve the same results as a feed motion along the Y-axis (see FIG. 2).

The second embodiment of the inventive lathe, as illustrated in FIGS. 7 and 8, differs from the first embodiment shown in FIGS. 1 to 6 merely in that the C-axis motor 90 also drives the turret support shaft 40. In the following, therefore, only the differences will be described and the same reference numerals will be used for those parts which correspond to the parts of the embodiment shown in FIGS. 5 and 6.

This second embodiment has a toothed belt pulley 200 attached to an axis 98a of the worm 98. In addition, the axis 98a directly drives an angular position transducer 202, with the aid of which, as well as with the aid of the NC system 154, the main spindle 14 can be rotated and stopped such that its position or rather angle of rotation is controlled. An arm designated as a whole as 204 is mounted on the axis 98a for pivoting movement. It consists of two forked elements 204a and 204b which can be adjusted and fixed relative to one another in the longitudinal direction of a threaded bolt 206 by means of a telescopic guide, which is not illustrated in detail, the threaded bolt 206 and a nut 208. The element 204b is rotatably mounted on a freely movable shaft 210 so that the arm 204 can also pivot about the shaft 210. A pair of toothed belt pulleys 212 and 214 is mounted on this shaft and a first toothed belt 216 runs over the toothed belt pulleys 200 and 212. A second arm 218 is constructed in the same way as the arm 204 and it is therefore unnecessary to describe it in detail. This arm is pivotable not only about the shaft 210 but also about a drive sleeve 220 and serves to receive the tension forces of a toothed belt 222 which runs over the toothed belt pulley 214 and a toothed belt pulley 224 formed by the drive sleeve 220. The drive sleeve 220 is rotatably mounted on a worm shaft 130a rigidly connected to the worm 130 and forms part of a coupling designated as a whole as 230. This coupling has a driver 232 which is displaceable along the worm shaft 130a and is non-rotatably connected to this shaft by, for example, splines which are not illustrated. It also has a circumferential groove 234, in which activating means for the coupling 230 are intended to engage. These activating means are not illustrated. The driver 232 can be non-rotatably connected to either the drive sleeve 220 or a tubular support 236 by means of the illustrated teeth. The tubular support encircles the worm shaft 130a concentrically and is molded onto the upper carriage 38. In the position of the driver 232 shown in FIG. 8, the turret support shaft 40 is disengaged from the C-axis motor 90 and blocked. If the driver 232 is displaced to the left in FIG. 8 the worm 130 is coupled to the C-axis motor 90 and can be driven by it. At the same time, the gear unit shown in FIG. 8 between the worm shaft 98a and the drive sleeve 220 allows the upper carriage 38 to be displaced in the direction of the X and Z-axes without such movements causing any errors at the worm 130 or the turret support shaft 40 with respect to angles of rotation when the toothed belt pulleys 200 and 212 are of the same size and the toothed belt pulleys 213 and 224 are also of the same size.

In the third embodiment shown in FIG. 10, the main motor 24 shown in FIG. 1 is used to drive not only the main spindle 14 but also the turret tools. Two belt pulleys 302 and 304 are mounted on the shaft 300 of the main motor 24, the belt pulley 304 driving a primary shaft 310 of an actuatable gear unit 312 via drive belts 306 and a belt pulley 308. This gear unit allows the main spindle 14 to be driven by the main motor 24 at various gear ratios and it can also be switched to an idling setting. A belt pulley 316 is mounted on an output shaft 314 of the gear unit 312 so that the main spindle 14 may be driven by the main motor 24 via drive belts 318 and a belt pulley 320 mounted on the main spindle.

The auxiliary spindle drive shaft 62 is non-rotatably connected via splines 330 to a drive sleeve 332 which is rotatably mounted in the lower carriage 34 but is not axially displaceable. In this way, it is possible to displace the upper carriage 38 in the direction of the Z-axis with the auxiliary spindle drive shaft 62. A belt pulley 336 is molded onto the drive sleeve 332 and drive belts 338 run over this to a belt pulley 340 which is mounted on an intermediate shaft 342. The latter bears a second belt pulley 344, over which drive belts 346 run to belt pulley 302.

Two belt tension arms 350 and 352 are pivotable about either the drive sleeve 332 and the intermediate shaft 342 or the shaft 300 and the intermediate shaft 342. Their construction corresponds to that of the arms 204 and 218 illustrated in FIGS. 8 and 9 and need not be described in detail. The inventive gear unit between the shaft 300 of the main motor 24 and the auxiliary spindle drive shaft 62 therefore allows the tool turret 44 to be displaced at will along both the Z and X-axes. Such movements do not result in any superimposed rotational movements when the belt pulleys 302 and 344 have the same diameter and the belt pulleys 336 and 340 also have the same diameter.

Claims

1. In an nc lathe, comprising a main spindle mounted for rotation in a spindle stock about a main spindle axis; a main motor for rotatably driving said main spindle about said main spindle axis; a workpiece chuck means mounted on said main spindle; a tool turret arranged adjacent said main spindle; means for rotatably mounting said tool turret; means for rotatably driving said tool turret about a tool turret axis parallel to the main spindle axis; said tool turret comprising a turret body and at least one turret spindle for holding a tool rotatably mounted in said turret body; means for rotatably driving said turret spindle about a turret spindle axis extending radially to the turret axis; a carriage bearing said tool turret for slidable displacement transversely to the main spindle axis, and a carriage drive for slidably displacing said carriage, the improvement comprising nc control means operatively connected to said main motor, the tool turret driving means, and said carriage drive for effecting controlled, stepless, transverse displacement of the carriage and controlled stepless rotation of the main spindle and of the tool turret such that simultaneously

(a) the main spindle is rotated about the main spindle axis in a defined direction of rotation and with a defined angular velocity of dγ/dt;

(b) the turret spindle is rotated about the turret spindle axis;

(c) the turret is rotated about the turret axis in the defined direction of rotation and with said defined angular velocity;

(d) the carriage is displaced transversely to the main

spindle axis at a velocity dx/dt said velocities being the first derivatives of the following equations: ##EQU3## wherein t, γ, X, A, Y_o, and v_y denote the following: t=the time which is equal to zero when a tool carried by said turret spindle touches a workpiece carried by said chuck means for the first time;

γ=the angle between the turret spindle axis and a first plane defined by the main spindle axis and the turret axis;

X=the distance of the turret axis from the main spindle axis;

A=the distance of the turret axis from the normal projection of the main spindle axis onto a second plane defined by the turret axis and the turret spindle axis, which plane pivots about the turret axis;

Y=the distance of the main spindle axis from said second plant, with Y_o being the value of Y when t equals zero;

v_y =the feed velocity dy/dt of the turret spindle axis relative to the main spindle axis in the direction of diminishing values of Y.

2. In an nc lathe, comprising a main spindle mounted for rotation in a spindle stock about a main spindle axis; a main motor for rotatably driving said main spindle about said main spindle axis; a workpiece chuck means mounted on said main spindle; a tool turret arranged adjacent said main spindle; means for rotatably mounting said tool turret; means for rotatably driving said tool turret about a tool turret axis parallel to the main spindle axis; said tool turret comprising a turret body and at least one turret spindle for holding a tool rotatably mounted in said turret body; means for rotatably driving said turret spindle about a turret spindle axis extending radially to the turret axis; a carriage bearing said tool turret for slidable displacement transversely to the main spindle axis, and a carriage drive for slidably displacing said carriage, the improvement comprising nc control means operatively connected to said main motor, the tool turret driving means and said carriage drive for effecting controlled stepless transverse displacement of the carriage and controlled stepless rotation of the main spindle and of the tool turret such that simultaneously

(a) the main spindle is rotated about the main spindle axis in a defined direction of rotation and with a defined angular velocity dγ/dt;

(b) a turret spindle is rotated about the turret spindle axis;

(c) the turret is rotated about the turret axis in the defined direction of rotation and with said defined angular velocity;

(d) the carriage is displaced transversely to the main spindle axis at a velocity dx/dt

said velocities being the first derivatives of the following equations: ##EQU4## wherein t, γ, X, Y, A_o, and v_A denote the following:

t=the time which is equal to zero when a tool carried by the turret spindle touches a workpiece carried by said chuck means for the first time;

γ=the angle between the turret spindle axis and a first plant plane defined by the main spindle axis and the turret axis;

X=the distance of the turret axis from the main spindle axis;

A=the distance of the turret axis from the normal projection of the main spindle axis onto a second plane defined by the turret axis and the turret spindle axis, which plane pivots about the turret axis, with A_o being the value of A when t equals zero;

Y=the distance of the main spindle axis from said second plane;

V_A =the feed velocity dA/dt of the turret body relative to the main spindle in the direction of diminishing values of A.

3. The lathe of claim 1 or 2, 2, 15, 19 or 23 in combination with a C-axis motor controlled by said nc control means, and an angular position transducer connected to the main spindle is provided for controlled drive of the main spindle with respect to its angle of rotation.

4. The lathe of claim 3, wherein an actuatable coupling connects the C-axis motor to the main spindle.

5. The lathe as defined in claim 4, wherein the C-axis motor is the turret indexing motor.

6. The lathe as defined in claim 5, in which an actuatable coupling is provided between the main spindle and the tool turret, and an actuatable blocking device is associated with the tool turret for stopping said tool turret.

7. The lathe of claim 5, in combination with a first gear wheel in drive connection with the main spindle and mounted on an axis which is stationary relative to the main spindle axis, and a second gear wheel in drive connection with the tool turret mounted on an axis which is stationary in relation to the turret axis and parallel to the axis of the first gear wheel; a gear unit arranged between said first and second gear wheels comprising a freely movable intermediate shaft extending parallel to the axes of the first and second gear wheels; third and fourth gear wheels mounted for rotation with the intermediate shaft; a pair of continuous interconnecting means, a first of which engages the first and third gear wheels and a second of which engages the second and fourth gear wheels; a pair of connecting arms extending between said wheel axes and said intermediate shaft; a first arm being pivotable about both the axis of the first gear wheel as well as the intermediate shaft, and a second arm being pivotable about both the intermediate shaft and the axis of the second gear wheel.

8. The lathe has defined in claim 7, in which the first and third gear wheels are of the same size and the second and fourth gear wheels are of the same size.

9. The lathe as defined in claim 7, in which the arms are adjustable with respect to their length.

10. The lathe as defined in claim 5 9, in which the first and third gear wheels are of the same size and the second and fourth gear wheels are of the same size.

11. The lathe as defined in claim 1 or 2, in which the main motor is stationary, and a gear unit connects the said main motor to a turret spindle drive shaft concentric to the turret axis; said gear unit comprising a first gear wheel with a stationary axis, a second gear wheel, the axis of which is stationary in relation to the turret axis and parallel to the axis of the first gear wheel; a freely movable intermediate shaft parallel to the axes of the first and second gear wheels; said gear unit also comprising third and fourth gear wheels nonrotatably connected to the intermediate shaft and a pair of continuous connecting means, a first of which runs over the first and third gear wheels and a second of which runs over the second and fourth gear wheels; and a first arm pivotable about the axis of the first gear wheel and the intermediate shaft for interconnecting said axes axis and said intermediate shaft, and a second arm pivotable about the intermediate shaft and the axis of the second gear wheel for interconnecting said intermediate shaft and the axis of said second gear wheel.

12. The lathe has defined in claim 11 in which the arms are adjustable with respect to their length.

13. The lathe as defined in claim 12, in which the first and third gear wheels are of the same size and the second and fourth gear wheels are of the same size.

14. The lathe as defined in claim 11, in which the first and third gear wheels are of the same size and the second and fourth gear wheels are of the same size.

15. In an nc lathe including a main spindle mounted for rotation in a spindle stock about a main spindle axis; motor means for rotatably driving said main spindle about said main spindle axis; a workpiece chuck means mounted on said main spindle; a tool turret arranged adjacent said main spindle; means for rotatably mounting said tool turret; means for rotatably displacing said tool turret about a tool turret axis parallel to the main spindle axis; said tool turret comprising a turret body and at least one turret spindle for holding a tool rotatably mounted in said turret body; means for rotatably driving said turret spindle about a turret spindle axis disposed in a plane perpendicular to the tool turret axis; slidable carriage means and a carriage drive for effecting relative displacement between said tool turret and said main spindle in a direction transverse to the axes thereof, the improvement comprising: nc control means operatively connected to said motor means, the means for rotatably displacing said tool turret and said carriage drive for effecting controlled, stepless, transverse displacement of the carriage and controlled stepless rotational displacements of simultaneously, during machining by said lathe:

(a) said main spindle is displaced about said main spindle axis in a defined direction of rotation to provide predetermined continuous angular displacement of said main spindle and said chuck means;

(b) said turret spindle is rotated about said turret spindle axis;

(c) said tool turret is displaced about said tool turret axis in said defined direction of rotation and with the same continuous angular displacement as said main spindle and said chuck means, whereby said turret spindle axis is maintained perpendicular to a predetermined plane parallel to said main spindle axis and rotating with said workpiece chuck means during such rotational displacement of said main spindle and said tool turret; and

(d) said relative displacement is effected between said tool turret and said main spindle in a direction transverse to the main spindle axis to effect relative positioning of said turret spindle in a direction parallel to the first spindle axis and thus perpendicular to said predetermined plane in a predetermined manner while performing such machining.

16. The lathe as defined in claim 15, wherein said turret spindle axis intersects and extends radially from said tool turret axis. 17. The lathe as defined in claim 15, wherein said tool turret is mounted on said carriage. 18. The lathe as defined in claim 15, wherein said nc control means includes means for effecting rotational displacement of said main spindle and said tool turret at the same constant angular velocity during machining operation by said

lathe. 19. In an nc lathe including a main spindle mounted for rotation in a spindle stock about a main spindle axis; motor means for rotatably driving said main spindle about said main spindle axis; a workpiece chuck means mounted on said main spindle; a tool turret arranged adjacent said main spindle; means for rotatably mounting said tool turret; means for rotatably displacing said tool turret about a tool turret axis parallel to the main spindle axis; said tool turret comprising a turret body and at least one turret spindle for holding a tool rotatably mounted in said turret body; means for rotatably driving said turret spindle about a turret spindle axis disposed in a plane perpendicular to the tool turret axis; slidable carriage means and a carriage drive for effecting relative displacement between said tool turret and said main spindle in a direction transverse to the axes thereof, the improvement comprising: nc control means operatively connected to said motor means, the means for rotatably displacing said tool turret, and said carriage drive for effecting controlled, stepless, transverse displacement of the carriage and controlled stepless rotational displacements of the main spindle and of the tool turret such that simultaneously, during machining by said lathe:

(a) said main spindle is displaced about said main spindle axis in a defined direction of rotation and with a defined angular velocity;

(b) said turret spindle is rotated about said turret spindle axis;

(c) said tool turret is displaced about said tool turret axis in said defined direction of rotation and with said defined angular velocity whereby said turret spindle axis is maintained perpendicular to a predetermined plane parallel to said main spindle axis and rotating with said workpiece chuck means during such rotational displacement of said main spindle and said tool turret; and

(d) said carriage is displaced in a direction transverse to the main spindle axis at a displacement velocity to effect relative positioning of said turret spindle in a direction parallel to the turret spindle axis and thus perpendicular to said predetermined plane in a predetermined manner

while performing such machining. 20. The lathe as defined in claim 19, wherein said turret spindle axis intersects and extends radially from said tool turret axis. 21. The lathe as defined in claim 20, wherein said tool turret is mounted on said

carriage. 22. The lathe as defined in claim 15 or 19 in which the motor means is stationary, and a gear unit connects said motor means to a turret spindle drive shaft concentric to the turret axis; said gear unit comprising a first gear wheel with a stationary axis, a second gear wheel, the axis of which is stationary in relation to the turret axis and parallel to the axis of the first gear wheel; a freely movable intermediate shaft parallel to the axes of the first and second gear wheels; said gear unit also comprising third and fourth gear wheels nonrotatably connected to the intermediate shaft and a pair of continuous connecting means, a first of which runs over the first and third gear wheels and a second of which runs over the second and fourth gear wheels; and a first arm pivotable about the axis of the first gear wheel and the intermediate shaft for interconnecting said axis and said intermediate shaft, and a second arm pivotable about the intermediate shaft and the axis of the second gear wheel for interconnecting said intermediate shaft

and the axis of said second gear wheel. 23. An nc lathe including a spindle stock;

a main spindle mounted for rotation in said spindle stock about a main spindle axis;

a workpiece chuck means mounted on said main spindle;

driving means for rotatably displacing said main spindle about said main spindle axis;

nc control means operatively connected to said driving means for effecting controlled rotational displacement of said main spindle in a defined direction about said main spindle axis during machining operation of said lathe;

a rotatable tool turret arranged adjacent said main spindle;

means for rotatably displacing said tool turret about a tool turret axis parallel to said main spindle axis;

said tool turret comprising a turret body, at least one turret spindle and means for holding a tool in said spindle for rotation about a turret spindle axis disposed in a plane extending generally normal to said tool turret axis;

a drive for rotating said turret spindle about said turret spindle axis to effect such machining operation;

means for controlling said tool turret displacing means and for thereby effecting controlled rotational displacement of said turret spindle axis in said defined direction about said tool turret axis simultaneously with and with the same rotational displacement as said main spindle during such machining operation whereby said turret spindle axis is maintained perpendicular to a predetermined plane which is parallel to said main spindle axis and rotating with said workpiece chuck means during such machining; and

carriage means and a carriage drive associated with said tool turret and said main spindle and responsive to said nc control means for effecting controlled, stepless, relative displacement between said tool turret and said main spindle in a direction transverse to said main spindle axis to position a tool mounted in said tool holding means of said turret spindle in a direction along said tool spindle axis in a predetermined manner simultaneously with such rotational displacement of said turret spindle axis and main spindle during such machining of a workpiece in said chuck by said tool,

whereby off-center machining may be performed by said lathe without a feed motion of the tool turret relative to said workpiece chuck in a direction generally normal to said direction of relative displacement between said tool turret and said main spindle. 24. A lathe as defined in claim 23, including transducer means for providing an output in accordance with the angular position of said main spindle, and wherein said nc control means is responsive to the output of said transducer for effecting such controlled rotational displacement of said main spindle in said defined direction during such machining of a workpiece by said

machine. 25. A lathe as defined in claim 23, wherein said tool turret is mounted on said carriage means. 26. A lathe as defined in claim 23, 24 or 25 wherein said turret spindle is disposed in said tool turret such that said turret spindle axis intersects and extends radially from said tool turret axis. 27. A lathe as defined in claim 23, wherein said means for rotatably displacing said tool turret and said means for controlling said means for rotatably displacing said tool turret includes an actuable mechanical coupling between said main spindle and said tool turret. 28. A lathe as defined in claim 23, wherein said means for controlling said means for rotatably

displacing said tool turret includes said nc control means. 29. A lathe as defined in claim 23, wherein said means for rotatably displacing said tool turret is a motor, and said means for controlling said tool turret displacing means includes transducer means for providing an output in accordance with the angular position of said tool turret and said nc control means being responsive to the output of said transducer means for effecting such controlled rotational displacement of said turret spindle axis.