FR2528745A1 - Three-plane movement controller for machine tool - uses processor to determine displacement and angle data from cartesian coordinates to reference point - Google Patents

Abstract

A carriage (13) slides in vertical slides fixed to a second carriage. This slides on horizontal slides (11) fixed to a vertical face of a block (12). Rotation of a drum (14) in the first carriage is ensured by driving a tangential wheel which engages an endless screw. The screw is driven by a digitally controlled motor. This allows the horizontal shaft of a chuck (15) to turn and to move vertically upwards or downwards. This action defines a surface area with two parallel segments with semi circular ends. The computer program ensures that the processor determines the vertical displacement and the angle required from cartesian data reference to a reference point. The processor determines any corrections to be applied. The arrangement may be used with e.g. tools for boring, e.g. countersinking.

Description

 Method for three-dimensional movement of a tool and machine tool for its implementation.

 The present invention relates to machine tools and more particularly the control of the movements of a tool of a machine tool, in particular a milling machine.

 In a milling machine, it is necessary to move the tool three-dimensionally, generally by means of three carriages sliding respectively on each other in three directions perpendicular to each other.

 the mechanical solutions which have been recommended for the production of a mobile assembly of three combined carriages for obtaining the displacement of the tool in space have numerous imperfections.

 In fact, although the best preloaded recti vines slides provide greater rigidity than smooth slides of the same length, this rigidity is however not sufficient for a set of three stacked carriages to have no deformation.

 Consequently, most milling machines generally comprise, on the one hand, a set of two carriages on which the workpiece or the rotating tool-holder spindle is fixed, and, on the other hand, a third independent carriage equipped with the spindle or part, respectfully.

 This arrangement has other drawbacks since the workpiece carrier trolley is mobile, automatic loading is less easy and the loading-unloading position requires considerable movement, since the mobile workpiece carrier trolley is larger than a simple workpiece carrier .

 the two combined trolleys and the trolley alone must not interfere in their movements, which imposes significant overhangs of the tool-holder spindle to save the essential clearance space.

 Finally, the design of the workpiece clamps must take into account the geometry of the workpiece carrier, which imposes certain constraints.

 The object of the present invention is a machine tool with digital control in which the three-dimensional movements of the tool are ensured by a rigid and compact mobile assembly limiting the overhangs and allowing any desirable design of the workpiece carrier.

 The subject of the invention is a method for three-dimensional movement of a machine tool tool parallel to itself, characterized in that the tool is given three possibilities of controlled movement along a circle of a plane perpendicular to the axis of the tool, as well as parallel to an axis of this plane and to an axis perpendicular to this plane, and in that the movements of the tool are coordinated simultaneously according to these three possibilities to follow a predetermined path.

 In such a method, it is advantageous to limit the movements of the tool during machining inside a rectangular parallelepiped whose height corresponds to a predetermined travel of the tool perpendicular to the plane of the circle, and whose the basic rectangle is inscribed in the space between two parallel halves of the circle separated by a distance corresponding to a predetermined stroke of the tool parallel to the plane of the circle.

 According to such a method, the tool can be brought outside of the machining in an extreme position of a portion of the circle outside the basic rectangle.

 Such a method makes it possible to determine the displacements of the tool according to the Cartesian coordinates of the envisaged course.

 The invention also relates to a machine tool implementing such a method and characterized in that it comprises a tool holder mounted eccentrically on a rotary drum pivoting on a first carriage which slides, parallel to the axis of the drum , on a second sliding carriage, perpendicular to the first carriage, on a bench of the machine tool, and in that drive means ensure the rotation of the drum and the translation of the carriages under the coordination of programmable control means.

 In an advantageous embodiment, the drum drive means rotate it on a portion of the same half-turn for machining and bring it on the other half-turn for tool change and / or change of workpieces.

 Such a machine may include a workpiece holder which is stationary in translation and angularly movable along two axes of rotation perpendicular to each other and to the axis of the tool.

 A machine according to the invention may include digital control means with programming in Cartesian coordinates.

 The value of the tool displacements is thus determined relative to a common point of origin with three perpendicular axes, each displacement being parallel to one of these directions.

 The set of these values defines the Cartesian coordinates of the point to be reached by the displacements.

 The invention will be better understood on reading the detailed description which follows and on examining the appended drawings which represent, by way of nonlimiting example, an embodiment of the invention.

On these drawings
FIG. 1 is a diagram recalling the definition of the coordinates of a point,
FIG. 2 is a diagram showing the adjustment of the center of a cutting blade on an internal lathe tool holder, according to a conventional method,
FIG. 3 is a partial schematic view of the tool holder of a machine tool according to the invention,
Figures 4 to 8 are diagrams of the movements of a tool according to the method of the invention.

 Figure 9 is a schematic perspective view of a milling machine according to the invention.

 The invention is based on the definition of the position of a point in a plane along geometric coordinates which make it possible to use, very advantageously, numerical control and modern computers.

 As shown in Figure 1, we define the position of a point 1 by its distance a to a point of origin 0 and the angle b made by the line segment joining these two points with the reference axis XX ' passing through point 0.

With respect to a point 3 placed on this reference axis at a distance c from point 0, the coordinates will be defined
X and Y of point 1 compared to point 3 by the relations
X = c + a cos.b, and Y = a sin.b.

 This mode of defining the position of a point has been used empirically for a long time in workshops, in particular for adjusting the center of a cutting wheel of form, mounted on an interior tool holder for a lathe.

 As shown in FIG. 2, to bring the center 1 of the mo 1 ette 4 to a height different from the value d of the center 37 of the part to be turned, the eccentric knurling spindle 8 is turned in the holder housing bar 9 until the height difference d is obtained.

Thus, both the profile of the desired shape and the clearance angle of the tool are ensured. Then, by a transverse displacement, the position of the tool tip is adjusted.

This intervention is manual and does not require any calculation on the part of the operator. The latter turns the ring 8 until it has compensated for the difference in level Y between the center of the bar holder 9 and the center of the part to be turned 6. I1 does not know the angle b
In the approach movement of the wheel towards the workpiece, the operator does not take into account the movement of the wheel in the direction x - x 'which is the consequence of the rotation of the ring 8.

 A similar arrangement is found in the embodiment of the invention shown in FIG. 3.

 The horizontal tool-holder spindle 15 rotates in an eccentric cylindrical part 16 of a rotary drum 14 housed in a carriage 13 of cubic shape.

This carriage 13 slides on vertical slides fixed on a carriage 10 sliding on horizontal slides 11 fixed on a bench 12 with vertical face
The slides are of conventional shape and the rotation of the drum is ensured by driving a tangent wheel mounted on the drum in which engages an endless screw driven by a numerically controlled motor. This classic training mode is not shown and is not part of the invention.

 With such a device, when the carriage 10 is held nmcbile the central point 17 of the spindle 15 can be moved vertically by raising or lowering the carriage 13 or along a circumference having the eccentricity e of the spindle 15 on the drum 14 .

 By combining these two movements, it is possible to place the central point 17 of the spindle 15 at any location on a surface delimited (FIG. 4) by two segments of lines 18 and 19 equal to the vertical stroke of the carriage 13 and of a semi-circumference 20-21 of radius e.

 If the device according to the invention is applied to a pointing machine, all of this surface can be used. On the other hand, in a milling machine all the paths are not possible and, for example (FIG. 5), the tool cannot be moved in a straight line by a point 23, being on an upper half-circumference 22, at a point 24 located on a lower half-circumference 25.

 For a milling machine, the usable surface of the contouring is limited, if we do not take into account the problem of speed of movement, to two equal and symmetrical zones (Figures 6 and 7) each defined by two half-circumferences turned in the same direction 21 and 26 or 20 and 27 and the two straight lines 18 and 19.

 In these surfaces, by combination of a semi-circular movement and a linear vertical movement, any curve can be described.

 We thus find the same conditions in which the operator turns the wheel-holder to bring the center of the wheel up to height (Figure 2).

 In the device according to the invention, the programming is done in Cartesian data and the computer determines the value of the vertical displacement and that of the angle, without the operator having to worry about the angular values and the corrections to be made. on vertical displacement.

 there may exist, however, displacement speed problems near the lines 18 and 19 or it may be necessary to provide high displacement speeds along the axis X - X 'for small displacements along the axis Y -Y '.

 Consequently, it is preferable to limit the zone used for machining to a rectangular zone 28 (FIG. 7) chosen away from the lines 18 and 19.

 This arrangement allows an easy change of tools (or part). Indeed, by rotation of the drum 14 and mounting of the carriage 13, the spindle 15 is brought quickly to an end point 29 of the half-circumference 20 away from the working area.

 By supplementing the displacements described in the plane of the circle 2 (FIG. 8) by perpendicular displacements along an axis 7, it is thus possible to move the point 17 of the spindle 15 inside a rectangular parallelepi 33 having for base the rectangle 28 in the plane of circle 2.

 The device according to the invention, the combined carriage of which avoids the movement of the workpiece during machining, makes it possible to produce a workpiece carrier with two perpendicular axes of rotation (FIG. 9).

 The device shown partially in FIG. 3 is found in the diagram in FIG. 9.

 A workpiece table 32 is pivotally fixed about a horizontal axis 36 in the center of a support 31 in the shape of a coated U.

 This support 31 pivots itself around a vertical axis 35 between a lower console 30 and an upper bracket 34 fixed at the end of the bench 12.

 As for the spindle drum, the control of the rotation of the support 31 and of the workpiece table 32 is ensured by a tangent wheel and worm drive driven by a numerically controlled motor.

 -The upper bracket provides preferential housing for the rotation control of the support 31, while the cables and other conduits associated with the workpiece table 32 pass easily through the lower console.

 Due to the vertical design of the bench, the lower console 30 can advantageously have a shape released by a double slope 37 which allows a particularly easy evacuation of the chips.

 The mounting of the indexable workpiece carrier with two pivoting axes is very rigid and the slides can be easily protected, away from the machining station.

 Of course, the invention is in no way limited to the embodiment described and shown, it is capable of numerous variants accessible to man.

of art, depending on the applications envisaged and without departing from the scope of the invention.

Claims (8)

 1. Method for three-dimensional movement of a machine tool tool parallel to itself, characterized in that the tool is given three possibilities of controlled movement along a circle 2 of a plane perpendicular to the axis of the tool, as well as parallel to an axis 5 of this plane and to an axis 7 perpendicular to this plane, and in that the movements of the tool are coordinated simultaneously according to these three possibilities to follow a predetermined path.  2. Method according to claim 1, characterized in that, during machining, the movements of the tool are limited within a rectangular parallelepided 33 whose height 7 corresponds to a predetermined stroke of the tool perpendicularly in the plane of circle 2, and whose base rectangle 28 is inscribed in the space between two parallel halves 21, 26 of circle 2 separated by a distance 5 corresponding to a predetermined stroke 5 of the tool parallel to the plane of the circle 2.  3. Method according to claim 2, characterized in that, apart from the machining, the tool is brought into an extreme position of a portion of the circle 2 outside the basic rectangle 28.  4. Method according to one of claims 1 to 3, characterized in that one determines the displacements of the tool according to the Cartesian coordinates of the envisaged course.  5. Machine tool, with a tool displaceable according to the method of one of claims 1 to 4, characterized in that it comprises a tool holder 16 mounted eccentrically on a rotary drum 14 pivoting on a first carriage 10 which slides, parallel to the axis of the drum 14, on a second sliding carriage 11, perpendicular to the first carriage 10, on a bench 12 of the machine tool, and in that drive means ensure the rotation of the drum 14 and the translation carriages 10, 11 under the coordination of programmable control means.  6. Machine tool according to claim 5, characterized in that the drive means of the drum 14 make it pivot on a portion of the same half-turn for machining and bring it on the other half-turn for tool change and / or workpiece change.  7. Y. machine tool according to one of claims 5 and 6, characterized in that it comprises a workpiece holder 32 stationary in translation and angularly movable along two axes of rotation 35, 36 perpendicular to each other and to the tool axis.  8. Machine tool according to one of claims 5 to 7, characterized in that it comprises digital control means with programming in Cartesian coordinates.