System for working a workpiece comprising a machine tool and corresponding working method

Abstract

The invention relates to a system and a method for working a workpiece (P1) using a machine tool (M1) comprising a drive shaft (400) provided with a tool holder (600) to which a tool (900) can be coupled, a drive motor (2) for rotating at least one portion of the drive shaft (400), which portion is fitted with the tool holder (600); a feed motor (3) for axially moving the drive shaft (400). A device measures a distance representative of the distance between the workpiece (P1) and the frame (100) of the machine tool. A control unit (8) is configured to execute work operations on the workpiece by controlling the drive motor and / or the feed motor; to determine a change in the axial distance between the frame of the machine tool and the workpiece resulting from relative axial movement between the workpiece and the frame. The second motor is controlled so as to axially move the drive shaft in order to compensate for the relative axial movement between the workpiece and the frame.

Description

Description Title of the invention: Workpiece working system comprising a machine tool, and corresponding working method

[0001] FIELD OF THE INVENTION

[0002] The present invention relates generally to workpiece working systems comprising a machine tool.

[0003] PREVIOUS ART

[0004] We know about the state of the art of machine tools, for example for carrying out milling, routing, drilling, threading or nut tightening operations.

[0005] From document US5649451 A, a drilling system is known which includes a clamp for holding a workpiece, and a drilling machine which is configured to apply simultaneous linear and rotary motion to the drilling tool of the machine.

[0006] The machine comprises a first motor and a second motor. The first motor comprises a rotor coupled to a ball screw engaged with a helical ring on the drive shaft so as to convert the rotational motion of the rotor into a linear motion which is imparted to the drive shaft.

[0007] The second motor includes a rotor coupled to a ball spline that engages a spline on the drive shaft so as to transmit the rotary motion of the rotor to the drive shaft directly, while allowing the drive shaft to move linearly along its axis.

[0008] However, it is noted that during work, the part can move, even in the maintained state of the part, without this movement being intended by the operator. The part being worked can thus move back, for example due to the support of the tool on the part, which harms the quality of the work carried out on the part. In in particular the dimensions obtained for the area of ​​the part thus worked may not correspond to the desired dimensions.

[0009] GB2593501 A describes a robot that carries a machine tool including a drilling tool. The drilling tool includes a spindle drill.

[0010] US2012020756A describes a drilling / milling unit adapted to be supported by an industrial robot. The unit comprises a spindle rotatable about an axis. An electric servomotor axially drives a hollow shaft through a belt. An electric servomotor drives the spindle through an associated belt.

[0011] The aim of the present invention is to propose a new machine tool and a corresponding working method making it possible to overcome all or part of the problems set out above.

[0012] SUMMARY OF THE INVENTION

[0013] To this end, the invention relates to a system for working a part, the system comprising a machine tool which comprises: - a chassis; - a drive shaft having a longitudinal axis, said drive shaft being provided with a tool holder to which a tool, such as a drilling spindle, is capable of being coupled; - a first motor, called a rotation drive motor, which is a rotary motor configured to rotate at least a portion of said drive shaft provided with the tool holder; - a second motor, called a feed motor, said feed motor being configured to axially move said drive shaft, and preferably being a linear motor; characterized in that the system also comprises a distance measuring device configured to measure a distance representative of the distance between the part and the frame of the machine tool; - a control unit configured for: - performing work operations on the part by controlling the rotational drive motor to drive the tool holder in rotation, and / or by controlling the feed motor to axially move the tool holder; - determine using the distance measuring device a change in axial distance between the machine tool frame and the workpiece resulting from a relative axial displacement between the workpiece and the machine frame; - depending on the determined change in distance between the machine tool and the workpiece, controlling the second motor so as to axially move said drive shaft to compensate for said relative axial displacement between the workpiece and the frame of the machine, and in that the rotational drive motor and the feed motor are configured so that the axial displacement of said at least one part of the drive shaft which is provided with the tool holder is controllable independently of the rotation of said at least one part of the drive shaft which is provided with the tool holder.

[0014] The fact that the axial displacement of said at least one part of the drive shaft which is provided with the tool holder, is controllable independently of the rotation of said at least one part of the drive shaft which is provided with the tool holder, means that the rotation of said at least one part of the drive shaft has no effect on the axial displacement of the drive shaft and vice versa, which makes it possible to precisely and reliably move said drive shaft forward or backward in order to bring it to a new axial reference position according to the displacement of the workpiece which must be compensated.

[0015] The possibility of controlling the axial displacement of the drive shaft to which the tool holder is fixed, during operation of the machine tool, makes it possible to correct the position of the tool coupled to the tool holder and thus to maintain the relative position of the tool holder and therefore of the tool in relation to the workpiece, even in the event of relative axial displacement between the workpiece and the frame of the machine tool.

[0016] The relative axial displacement between the tool and the workpiece can be due to a displacement of the workpiece as a whole (for example a recoil of the workpiece) or to a deformation of the workpiece during the work it undergoes.

[0017] Taking into account the relative position variation between the machine tool and the workpiece helps ensure a workpiece working process that is accurate and reliable.

[0018] Relative axial movement compensation between the machine tool and the workpiece allows, in particular, effective chip fragmentation resulting from the tool working the workpiece. It should be noted that uncompensated relative axial movement could impair this chip fragmentation, or even prevent it. Relative axial movement compensation also ensures a countersink depth that meets the requirements.

[0019] In the prior art document GB2593501 A, the mobility of the drill is simply used to perform a reciprocating movement for drilling, but GB2593501 A does not provide for adjusting the axial position of the drill relative to the machine tool frame, to obtain a new reference position of the drill relative to the machine tool frame, in order to compensate for a measured bias between the machine tool frame and the workpiece. In GB2593501 A it is the robot arm itself that is moved to compensate for a bias between the workpiece and the drilling machine tool carried by the robot arm.

[0020] GB2593501 A does not provide for adjusting the axial position of the drill bit relative to the machine tool frame to compensate for the measured bias, with, relative to the frame, an axial displacement of the shaft carrying the drill bit, which would be controlled independently of the rotation of said shaft carrying the drill bit.

[0021] In GB2593501 A, moving the robot arm itself, which carries the machine tool, to try to correct a skew during drilling poses problems of accuracy and reliability because moving the entire robot arm - which is heavy - is less precise than moving the drill bit relative to the frame using the feed motor.

[0022] Furthermore, since this movement of the robot arm is the result of movements of several axes of the robot, the movement of the machine tool cannot be properly collinear with the drilling axis being carried out on the part and the quality of the tool's work is therefore impacted.

[0023] The design of the system according to the invention makes it possible to correct in real time the position of the working tool, such as a drill, while maintaining the drilling direction in the case of a drilling tool, and this in a simple and reliable manner.

[0024] In document US2012020756A, a rotation motor rotates a spindle, and the translational movement of the spindle is generated by a speed difference between the rotation motor and another motor. There is therefore not a complete decoupling between the two rotational and feed movements. For example, a slight change in the rotational speed of the rotation motor results in a slight translational movement of the spindle. In addition, in document US2012020756A, the feed movement also depends on a helical nut, a mechanical part which can have play, thus leading to axial positioning errors of the spindle, particularly during correction movements.

[0025] The design of the system according to the invention makes it possible to correct, by the movement of a single motor, namely the feed motor, the position of the tool coupled to the tool holder carried by the drive shaft, and thus to maintain the relative position of the tool holder and therefore of the tool with respect to the workpiece, even in the event of relative axial displacement between the workpiece and the frame of the machine tool, and this in a precise and reliable manner and in real time.

[0026] The system may also include one or more of the following features taken in any technically admissible combination.

[0027] According to one embodiment of the invention, the distance measuring device is carried by a movable part of a support device, called a sheet metal pressing nose, said movable part of the sheet metal pressing nose being mounted movable relative to a part which is fixed relative to the chassis, the movable part being configured to be returned to bear against the part, the distance measuring device being arranged to measure the distance between the movable part and the fixed part of the sheet metal pressing nose.

[0028] According to one embodiment of the invention, the drive shaft comprises a first section and a second section connected to each other by a connecting device, one of the sections being engaged with the feed motor, the other section being engaged with the rotation drive motor.

[0029] According to one embodiment of the invention, the drive shaft comprises a first section and a second section connected to each other by a connecting device configured to make the first section and the second section integral in axial displacement with each other, while maintaining freedom of rotation of the first section relative to the second section.

[0030] According to one embodiment of the invention, the first section to which the tool holder is fixed can be driven in rotation by the rotation drive motor, and the second section can be driven in axial movement by the feed motor.

[0031] According to one embodiment of the invention, the feed motor is a linear motor having a primary part mounted fixedly relative to the frame of the machine tool, and a secondary part, mounted mobile in a direction parallel to the axis of the drive shaft, which is fixed to a section of the drive shaft, or formed in a single piece with said section of the drive shaft.

[0032] According to one embodiment of the invention, the system comprises a support system, such as a poly-articulated robot, which carries the machine tool to enable the machine tool to be positioned at the desired position and orientation relative to the workpiece, the machine tool being mounted articulated to the support system.

[0033] According to one embodiment, the support system comprises a main base (or frame) and an arm, the machine tool being mounted articulated on the arm, said arm comprising one or more sections which can be articulated together, said arm preferably itself being mounted articulated on the base.

[0034] According to one embodiment of the invention, the control unit is configured to allow the drive shaft to be moved in order to move the tool axially in a variable speed movement to fragment the chip resulting from the work of the tool on the workpiece.

[0035] The invention also relates to a method of working a workpiece using a working system according to any one of the preceding embodiments, the machine tool of said working system comprising a tool holder equipped with a working tool, the method comprising the following steps: - positioning of the machine tool relative to the part with a view to working the part using said tool; the distance between the part and the frame of the machine tool being equal to a value, called the initial value, the drive shaft having an axial reference position relative to the frame of the machine tool; - performing work operations on the part by controlling the rotational drive motor to drive the tool in rotation, and / or by controlling the feed motor to axially move the tool; the axial movement of the tool being controlled as a function of said axial reference position of the drive shaft; - during the working of the part, determination of a change in the distance between the part and the machine frame, so that the distance between the part and the machine tool frame is equal to a new value; - compensation of the movement of the part by axial displacement of the drive shaft of the tool holder by a distance, called the compensation distance, corresponding to the difference between the new value and the initial value so as to define a new axial reference position of the drive shaft, - continuation of the workpiece working operations according to the new reference position of the shaft.

[0036] According to a particular aspect, for the compensation of the displacement of the part, the axial displacement of the drive shaft is carried out by keeping the frame of the machine tool which carries the motors, immobile in the terrestrial reference frame. It is therefore the drive shaft which moves, preferably along and inside the frame of the machine tool, and not the frame which would be moved in the terrestrial reference frame.

[0037] According to one embodiment of the invention, the rotary drive motor comprises a stator mounted fixedly relative to the frame of the machine, and a rotor which is in direct engagement with said drive shaft.

[0038] Preferably the stator comprises a winding system and the rotor comprises a magnet system so that the electrical supply to the winding system generates a magnetic field which interacts with the magnet system. The rotary motor thus generates a radial electromotive force (torque electromagnetic) which rotates at least the part of the drive shaft with which the rotor is engaged. The electromotive force generated by the rotary motor is radial while the electromotive force generated by the feed motor is axial.

[0039] Advantageously, the secondary of the advance motor is in direct contact with said drive shaft.

[0040] Preferably, the primary of the feed motor comprises a winding system carried by the frame and the secondary of the feed motor comprises a magnet system which is carried by a part integral with the drive shaft or which is directly integrated into the drive shaft. The electrical power supply of the winding system generates a magnetic field which interacts with the magnet system.

[0041] The feed motor generates an axial electromotive force that drives the drive shaft, with which the feed motor's secondary is engaged, in translation. The electromotive force generated by the feed motor is axial, while the electromotive force generated by the rotary motor is radial.

[0042] Having the magnet system carried by the drive shaft and the winding system, which is heavier than the magnet system, by the chassis, not only facilitates the wiring for powering the corresponding motor, but also limits the mass to be moved, i.e. the mass of the drive shaft, which improves the precision and reliability of movement, particularly axial, of the drive shaft.

[0043] In one particular aspect, the major portion of the drive shaft extends within the machine tool frame.

[0044] A driving element and a driven element are considered to be in direct engagement when the speed of movement of the driving element is the same as that of the driven element. There is no relative sliding between the elements. An intermediate part may be present but without relative movement between the driving part and the driven part.

[0045] BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Other characteristics and advantages of the invention will emerge from the following description, which is purely illustrative and non-limiting and must be read in conjunction with the appended drawings, in which:

[0047] - Figure 1 is a schematic view of a machine tool carried by a mobile support system, such as a robot, for working a part, according to one embodiment of the invention;

[0048] - Figure 2 illustrates a sectional view of a machine tool equipped with a tool which is in contact with a workpiece, according to one embodiment of the invention;

[0049] - Figure 2A illustrates a sectional view of the machine tool of Figure 2 with a relative axial displacement of the workpiece relative to the machine tool, resulting in a relative axial displacement of the workpiece relative to the tool;

[0050] - Figure 2B illustrates an axial sectional view of the machine tool of Figure 2A with axial displacement of the tool obtained by axial displacement of the tool drive shaft, to compensate for the relative axial displacement of the workpiece with respect to the tool;

[0051] - Figure 3 is a schematic axial sectional view of a machine tool according to another embodiment;

[0052] - Figure 4 is a schematic axial sectional view of a machine tool according to another embodiment;

[0053] - Figure 5 is the flowchart of a working method with a working system according to one embodiment.

[0054] DETAILED DESCRIPTION

[0055] The inventive concept is described more fully below with reference to the accompanying drawings, in which embodiments of the inventive concept are shown. In the drawings, the size and relative sizes of elements may be exaggerated for clarity. Like numerals refer to like elements throughout the drawings. However, this inventive concept may be embodied in many different forms and should not be construed as being limited to the embodiments embodiments disclosed herein. Instead, these embodiments are provided so that this description is complete, and communicate the scope of the inventive concept to those skilled in the art.

[0056] A reference throughout the specification to "an embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the present invention. Thus, the occurrence of the phrase "in an embodiment" at various locations throughout the specification does not necessarily refer to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0057] With reference to the figures, a system for working a part P1 is shown. The working system includes a machine tool M1 comprising a frame 100 and, carried by the frame 100, a working assembly which comprises a motorization system 2, 3 and a drive shaft 400.

[0058] The drive shaft 400 is provided at one end with a tool holder 600 capable of receiving a tool 900 for working a part P1. In the embodiment illustrated in FIGS. 2, 2A, 2B, only one end of the drive shaft 400 is provided with a tool holder and therefore with a tool. According to other embodiments and as illustrated in FIG. 3, it can be provided that each end of the drive shaft 400 is provided with a tool holder 600 and therefore with a tool 900. The drive shaft 400 can be driven by the motorization system 2, 3 itself controllable by a control unit 8 as described below.

[0059] The motorization system 2, 3 is configured to not only allow at least one part 4001 of the drive shaft 400 to which the tool holder 600 is fixed in rotation so as to be able to rotate the tool 900 fixed to the tool holder 600 in a removable manner, but also to axially move said part 4001 of the drive shaft 400 (preferably by axial movement of another part 4002 of the drive shaft as explained below) to allow axial movement of the tool holder 600 and therefore the tool 900 coupled to the tool holder.

[0060] Having the thrust axis (direction), which corresponds to the axis of movement of the drive shaft (also called the feed axis), collinear with the tool axis allows for precise and reliable work on the part.

[0061] As detailed below, the machine tool makes it possible to obtain reliable and precise compensation in real time of the axial position of the tool holder drive shaft relative to the workpiece P1, and therefore of the tool, when a relative axial displacement of the position of the workpiece occurs relative to the frame of the machine tool.

[0062] The reliability of this compensation results from the decoupling of the rotational movement of the part of the drive shaft to which the tool holder 600 is fixed relative to the translational movement applied (directly or indirectly) to said part of the drive shaft to which the tool holder is fixed.

[0063] According to one embodiment and as illustrated in the figures, the drive shaft 400 comprises a first section 4001 and a second section 4002 secured to each other in axial displacement.

[0064] The first section 4001 to which the tool holder 600 is fixed, can be driven in rotation by a first motor 2 presented below. The second section 4002 can be driven in axial displacement by a second motor 3 presented below, and arranged with the first section 4001 to drive said first section 4001 in axial displacement, while being independent in rotation of said second section 4002. The two drive shaft sections are collinear.

[0065] In other words, the axial movement of the second section 4002 which causes the axial movement of the first section 4001 has no impact on the rotation of the first section 4001 to which the tool holder 600 is fixed. Conversely, the rotation of the first section 4001 has no impact on the axial positioning of the second section 4002. This makes it possible to ensure good control of the process parameters by making the control of the rotational and translational movement of the sections of the tool holder drive shaft independent of each other, while ensuring a thrust in the tool axis, which makes it possible to reliably and precisely obtain the desired final geometry for the workpiece during work operations, such as drilling and milling.

[0066] As shown in Figure 1, the machine tool can be carried by a support system R1, such as a polyarticulated robot. The support system R1 can also be a numerically controlled machine or a specific tooling device.

[0067] It can be provided that the support system R1 is itself mounted on a carriage system configured to move in several directions relative to the workpiece P1. The support system and / or the carriage system makes it possible to position the machine tool and therefore the tool according to the desired position and orientation relative to the workpiece.

[0068] In the example illustrated in Figure 1, the support system R1 comprises a main base (or frame) BT1 and an arm BRS1. The machine tool M1 is mounted articulated on the arm BRS1. Said arm BRS1 comprises one or more sections which can be articulated together. Said arm BRS1 is preferably itself mounted articulated on the base BT1.

[0069] Advantageously, the working system comprises a device for relative location of the machine M1 with the part to be produced P1 to allow, in particular before starting work on the part, to know precisely the position and / or the orientation of the machine tool relative to the part P1.

[0070] In the example shown in Figure 1, the support system R1 is movable independently of the workpiece P1. For example, the support system R1 can be positioned so that the machine tool M1 has a position and orientation as shown in Figure 1 in short broken lines.

[0071] The tool 900 is for example a drilling spindle. The tool 900 has a longitudinal axis A900 coaxial with the axis A400 of the drive shaft 400. The tool holder 600 also has an axis A600 which is coaxial with the axis A400 of the drive shaft 400.

[0072] Motorization system

[0073] As mentioned above, the machine tool M1 comprises an electric motorization system which includes a first motor 2, called a rotation drive motor, configured to rotate at least one part 4001 of the drive shaft 400.

[0074] The motorization system also includes a second motor 3, called a feed motor, which makes it possible to axially move said drive shaft 400, preferably by being in direct contact with a section 4002 which is independent in rotation of the section 4001 which carries the tool 900 via the tool holder 600. In other words, the feed motor 3 makes it possible to control the translation of the drive shaft along its longitudinal axis A400 without impacting the rotation of said shaft.

[0075] The rotation drive motor 2 is mounted integral in rotation with the section 4001 of the drive shaft 400 provided with the tool holder 600 for its rotation drive, while being in sliding connection with said section 4001, to allow axial movement of said section 4001 controlled by the feed motor 3.

[0076] The rotation drive motor 2 and the feed motor 3 are capable of being driven independently of each other. As recalled above, each motor can, under the control of the control unit 8, act on the drive shaft 400 independently of the action of the other motor on said shaft: One of the motors controls only the rotation of the shaft and the other only its axial displacement. As explained below, the two motors act respectively on two collinear sections of the drive shaft, which makes it possible not to generate a geometric defect at the end of the tool 900 fixed to the tool holder during the rotation of the latter.

[0077] Preferably, the rotation axis of the rotation drive motor 2 is coaxial with the axis of the feed motor 3.

[0078] Drive shaft

[0079] As recalled above, in the embodiment illustrated in Figures 1 and 2, the drive shaft 400 comprises a first section 4001 which can be driven in rotation by the motor 2 and at one end of which the tool holder 600 is fixed, and a second section 4002 which can be driven in axial displacement by the feed motor 3, so as to be able to push or pull axially on the first section 4001 to axially displace the tool 900 associated with the first section 4001 by the tool holder.

[0080] The connection 4003 between the first section 4001 and the second section 4002 is configured so that the first section 4001 and the second section 4002 are integral in axial displacement with each other, while maintaining freedom of rotation of the second section 4002 relative to the first section 4001.

[0081] The connection 4003 can thus be produced in the form of a pivot connection, with a pivot axis coaxial with the axis A400 of the shaft of the drive shaft 400. Optionally, the connection 4003 can be produced in the form of a ball joint.

[0082] Such a design of the machine makes it possible to obtain independence of action of one motor on the drive shaft with respect to the action of the other motor on said drive shaft.

[0083] Thus, the rotation of the 900 tool and its axial position relative to the machine frame can be controlled independently of each other and therefore reliably and precisely.

[0084] The connecting device 4003 between the two sections 4001, 4002, is free of axial play, and allows the second section 4002 to rotate freely relative to the first section 4001.

[0085] This compact architecture allows for thrust on the 900 tool in the axis of the drive shaft (spindle axis), as well as decoupling of the control of the two motors.

[0086] Such a design facilitates the creation of control loops such as drilling cycles with discontinuous cutting allowing fragmentation of the chip which thus facilitates its evacuation during the operation.

[0087] In the embodiment variant of Figure 3 (or Figure 4), the section 4002' which is provided with the tool holder is engaged with the feed motor 3, and the other section 4001' is engaged with the rotation drive motor 2. The section 4002' controllable in axial movement by the feed motor 3, thus extends between the tool 900 and the section 4001' controllable in rotation by the motor 2. In this case the connection 4003 is a rigid connection so that the sections 4001', 4002' are integral in axial movement and in rotation.

[0088] The section of the drive shaft 400 which is engaged with the feed motor 3 is distinct from the section of the drive shaft 400 which is engaged with the rotation drive motor 2.

[0089] According to one embodiment, the two sections of the shaft of the machine tool M1 are drilled, preferably axially in their center, in order to allow a coolant liquid to pass through for the drilling operations.

[0090] Rotary engine

[0091] The rotary motor 2 corresponds to a spindle motor which rotates the first section 4001 of the drive shaft 400 which carries the tool 900. The rotary motor 2 comprises a stator 200 fixed relative to the frame 100 of the machine M1 and a rotor 210 whose rotation speed can be controlled by a control module 810 of the control unit 8 as explained below.

[0092] According to one embodiment, the first section 4001 of the drive shaft 400 is a splined section coupled in rotation with the rotor 210 of the motor 2 by a meshing system integral with the rotor 210 which cooperates with the splined section.

[0093] Preferably, the meshing system comprises a main meshing member 220 and a secondary meshing member 230 spaced axially apart in order to distribute the drive torque, and increase the stiffness of the assembly and improve the precision of the rotation of the first section 4001 thanks to longer guidance of said first section.

[0094] Preferably, the stator of the rotation motor comprises a winding system and the rotor comprises a magnet system such that the electrical supply to the winding system generates a magnetic field which interacts with the magnet system. The rotary motor thus generates a radial electromotive force (electromagnetic torque) which rotates at least the portion of the drive shaft with which the rotor is engaged.

[0095] Advance motor

[0096] Preferably, the feed motor 3 is a linear motor configured to control the axial movement of the second section 4002. The use of a linear motor makes it possible to axially move the second section 4002 and thus the first section 4001 axially linked to the first section, without causing rotation or adding rotational movement to the second section 4002.

[0097] As shown in the figures, the advance motor 3 comprises a primary 300 and a secondary 310.

[0098] The primary 300 is fixed relative to the frame 100 of the machine M1 and the secondary 310, which is fixed or integrated into the drive shaft 400, is movable in translation relative to the primary 300 in a direction parallel to the axis of the drive shaft 400. According to a particular embodiment, it can be provided that the primary 300 and the secondary 310 of the advance module comprise respectively several primaries and several secondaries. The advance motor generates an axial electromotive force (with an axis parallel to the axis of the drive shaft) which drives in translation the drive shaft with which the secondary of the advance motor is engaged.

[0099] According to one embodiment of the invention, the primary part of the feed motor comprises a winding system carried by the frame and electrically powered, and the secondary part 310 comprises a magnet system. The secondary of the feed motor comprises a magnet system which is carried by a part secured to the drive shaft or which is directly integrated into the drive shaft. The electrical power supply of the winding system generates a magnetic field which interacts with the magnet system.

[0100] Having the magnet system carried by the drive shaft and the winding system, which is heavier than the magnet system, by the chassis, not only facilitates the wiring for powering the corresponding motor, but also limits the mass to be moved, i.e. the mass of the drive shaft, which improves the precision and reliability of movement, particularly axial, of the drive shaft. The distribution of the winding system and the magnet system could be reversed, but would be less advantageous.

[0101] The power supply of the winding system of the feed motor can be carried out in such a way as to move the magnetic field created along the axis of the drive shaft at a given speed. Preferably, a control unit makes it possible to control the speed of movement of the magnetic field generated according to the desired travel speed to control the axial travel speed of the drive shaft.

[0102] As detailed below, the movement of the drive shaft to obtain a new reference position P4ref of the drive shaft, relative to the frame of the machine tool, in order to compensate for the movement of the workpiece, is obtained by controlling a single motor which is the feed motor.

[0103] In the example illustrated in Figures 1 and 2, the secondary 310 is mounted integral in translation with the section 4002 in a direction parallel to the axis of the section 4002 (which also corresponds to the axis of the section 4001 of the drive shaft 400). The axial displacement of the secondary 310 is controllable by a control module 820 of the control unit 8.

[0104] The axial displacement of the secondary 310 of the motor 3 causes the axial displacement of the second section 4002 of the drive shaft. The secondary 310 of the motor 3 and the second section 4002 can be made from a single piece.

[0105] As explained below, the feed motor 3 makes it possible to move the drive shaft 400 to compensate for a relative axial movement of the frame 100 of the machine M1 with the part P1 (Figures 2, 2A, 2B).

[0106] Compared to a complete displacement of the machine M1, the fact - to compensate for a relative axial displacement of the part P1 relative to the frame 100 of the machine - of simply axially moving the drive shaft 400 relative to the frame 100 of the machine by moving the secondary 310 of the feed motor 3 which is coupled to the section 4002 of the drive shaft 400, makes it possible to limit the size of the feed motor 3 and therefore to limit the size (size and mass) of the machine M1. Limiting the moving mass makes it possible to increase the mechanical bandwidth of the system.

[0107] In other words, the fact of being able, during the working operation of the part P1, in the event of detection of a relative axial movement between the part P1 and the frame 100 of the machine, to move the tool 900 axially by moving the secondary 310 of the feed motor relative to the primary 300 of the motor feed rate 3 and therefore relative to the frame 100 of the machine, makes it possible not to have to move the entire machine tool to carry out an axial correction of relative axial movement between the part and the frame of the machine during the working operation of the part.

[0108] Of course, when the machine tool is positioned on a movement system such as the support system R1, preferably itself carried by a carriage system, the entire machine remains movable relative to the part in order to first position and / or orient the tool 900 according to the work on the part to be carried out.

[0109] The motor 3 manages the advance of the second section 4002 of the drive shaft by direct translational drive, i.e. an axial displacement of the second section 4002 and therefore of the tool 900.

[0110] Having a direct transmission of movement between the feed motor 3 and the second section 4002 of the drive shaft without a reducer such as a helical nut, allows, on the one hand, to have good efficiency, and, on the other hand, to have direct and therefore noise-free force feedback information.

[0111] Such a design of the machine thus makes it possible to control the rotation of the tool 900 using the rotary motor 2 independently of the axial movement of the tool which can be controlled using the feed motor 3.

[0112] The independence of the rotation of the first section 4001 from its axial movement makes it possible to create control loops, such as for example drilling cycles with discontinuous cutting allowing the fragmentation of the chip which thus facilitates its evacuation during the operation.

[0113] To compensate for the movement of the part, the axial displacement of the drive shaft is achieved by keeping the machine tool frame that carries the motors stationary in the Earth's reference frame. It is therefore the drive shaft that moves, preferably along and inside the machine tool frame, and not the frame that would be moved in the Earth's reference frame.

[0114] In one particular aspect, the major portion of the drive shaft extends within the machine tool frame.

[0115] Advantageously, the secondary of the feed motor is in direct engagement with said drive shaft. A driving element and a driven element are considered to be in direct engagement when the speed of movement of the driving element is the same as that of the driven element. There is no relative sliding between the elements. An intermediate part may be present but without relative movement between the driving part and the driven part.

[0116] Distance determination system

[0117] The machine tool comprises a distance measuring device 521 configured to, in particular during the working of the part P1 by the tool 900, measure a distance representative of the distance between the part P1 and the frame 100 of the machine.

[0118] The distance measuring device 521 is connected to the control unit 8 which is configured to determine, using a distance modification determination module 830, a modification of axial distance between the frame 100 of the machine tool and the workpiece P1 to be worked.

[0119] As explained below, when the module 830 determines that the distance D1 between the frame 100 of the machine tool and the workpiece P1 to be worked has been modified to a distance D1', for example when the difference in distance D1 - D1' is greater than a threshold value, then the module 840 commands the axial displacement of the drive shaft 400 for a modification of the axial reference position P4ref of the shaft 400 to compensate for this relative modification of distance between the workpiece P1 and the frame 100 of the machine. The axial reference position of the drive shaft is memorized by the control unit 8 to allow the execution of the work instructions for the workpiece, which include commands for axial displacement (and rotation) of the shaft 400 and therefore of the tool 900, as a function of said axial reference position of the drive shaft.

[0120] Steering unit

[0121] As recalled above, the control unit 8 comprises a rotation control module 810 for controlling the rotation speed of the rotation drive motor 2. The rotation control module 810 is preferably configured to allow a rotation speed to be maintained constant of motor 2 and therefore of the tool, while allowing the speed of the tool to be varied as required.

[0122] The control unit 8 also comprises a feed control module 820 for controlling the feed motor 3 to control the axial movement of the second section 4002 and therefore of the first section 4001 equipped with the tool holder 600.

[0123] The machine tool comprises a section position sensor 4002 which is engaged with the feed motor 3. Said position sensor is connected to the control unit 8 to enable the control unit to know precisely the position of the section, and to enable the amplitude of the waveform of the feed movement to be modified in real time.

[0124] Advantageously, the advance control module 820 is configured to enable axial movement at constant speed of the second section 4002 to be controlled.

[0125] Preferably, the advance control module 820 can also be configured to control a main axial movement of the second section 4002 with oscillations superimposed on the main axial movement.

[0126] The control unit allows the rotation drive motor 2 and the feed motor 3 to be controlled independently of each other, while allowing them to be controlled simultaneously.

[0127] The control unit 8 comprises a control module 840 which is configured to, following a change in distance determined by the module 830 between the frame 100 of the machine tool M1 and the workpiece P1 to be worked, control the feed motor 3 to axially move said drive shaft by a distance equal to the determined change in distance. The drive shaft then has a new axial reference position P4ref according to which the work instructions for the workpiece P1 can continue to be executed, which makes it possible to compensate for the relative axial displacement of the workpiece P1 with respect to the frame of the machine M1.

[0128] Thus, in the case where there is a relative axial movement between the frame 100 of the machine tool M1 and the workpiece P1 of a given value, the machine thus makes it possible to compensate by the same value, and this in real time, the axial position of the shaft 400 and therefore of the tool 900.

[0129] It is possible to provide that the machine tool includes an interface allowing the selection of one or more oscillation parameters (frequency and / or amplitude) and / or the shape of the signal (sine, triangle, trapezoid, etc.).

[0130] It is possible to envisage that these parameters can be selected according to given criteria such as the hardness of the material and can be modified in real time in order to promote chip fragmentation. It is also possible to envisage that the oscillation parameters can be automatically defined or modified by a module of the machine control unit according to the results of a work test phase on the material to be worked.

[0131] According to one embodiment, the control unit 8 is configured to modify in real time instructions supplied to each of the control modules 810 and 820, as a function of data relating to the current consumed by the feed motor 3, and data supplied by the system for determining the variation in distance between the machine M1 and the part P1.

[0132] According to one embodiment, the variation in distance between the machine tool M1 and the workpiece P1 can be measured using a distance sensor 521 configured to measure the distance between a support device, called a sheet metal pressing nose, mounted at the end of the machine nose on a part of the machine, i.e. at the end of the machine where the tool is located, which comprises a part 520 intended to come to bear against the workpiece P1 and a part 510 of the frame 100 of the machine relative to which the part 520 is movable in a direction parallel to the axis of the drive shaft. It can also be provided that the variation in distance is provided by the distance measuring sensor 521 mounted on the part 510.

[0133] The part 520 has a through opening for the passage of the working tool. The part 520 is mounted axially movable relative to the frame, for example by a return spring to allow it to be returned to bear against the workpiece so that a relative axial movement between the workpiece and the frame of the machine in the direction of moving away from the workpiece P1 results in an axial separation of the part 520 of the sheet metal pressing system relative to the part 510 associated with the frame of the machine.

[0134] Alternatively, the sheet metal pressing system may be mounted on a support external to the machine tool, and fixed relative to said machine tool. The sheet metal pressing system maintains a fixed part 510 and a movable part 520 itself in contact with the workpiece P1 with at least one distance sensor in order to measure a relative axial movement between the two parts 520, 510.

[0135] Preferably, the working system comprises a device for measuring the orthogonality of the tool (or the axis of the drive shaft 400) of the machine M1 with the part P1.

[0136] In Figure 2, the sheet metal pressing nose is initially supported on the part P1 so that the distance between the part 520 of the sheet metal pressing nose and the part 510 fixed to the frame 100 is equal to D1.

[0137] Figure 2A illustrates the case where, during the working of the part P1, said part P1 moves back relative to the frame of the machine: the movable part 520 of the sheet metal pressing nose which is returned to bear against the part, is then moved away from the frame 100 by a distance D1'. In particular, Figures 2, 2A, then 2B show a relative movement between the machine tool M1 and the production part P1 and the associated compensation at the level of the machine axis in order to keep the tool 900 in real time in the same position relative to said part P1.

[0138] The distance change determination system thus determines that the part P1 has moved axially by a distance D1 - D1'.

[0139] The compensation module 840 of the control unit 8 controls the axial displacement of the drive shaft, here to advance it, by a distance equal to D1 - D1 ' to compensate for the recoil of the part relative to the chassis, so that the reference position P4ref (original position) of the shaft 400, defined for example as being the position of the free end of the section 4002 relative to the chassis 100 is modified to a position P4ref, with a distance between said reference positions P4ref' and P4ref equal to the distance D1 - D1 '.

[0140] Thus, as visible in Figure 2B, the position of the drive shaft 400 (machine axis) relative to the part P1 is compensated by the value of the relative axial displacement between the part P1 and the frame of the machine, i.e. say the value D1 '-D1 , and the position of the drive shaft relative to the chassis has been advanced (in the direction of part P1 ) by the distance D1 - D1 '.

[0141] According to one embodiment, the module 830 of the control unit 8 is configured to analyze in real time the data from the two control modules 810 and 820, in order to deduce therefrom the relative position of the tool 900 with the part P1, before the tool is inside this part.

[0142] It is also possible to provide that the module 830 of the control unit 8 analyzes in real time the data from the two control modules 810 and 820, in order to deduce therefrom the relative position of the cutting tool 900 with respect to a change of material in the workpiece P1 and thus adapt in real time the cutting parameters to the material to be machined according to the strategy adopted.

[0143] It can also be provided that the module 830 of the control unit 8 analyzes in real time the data from the two control modules 810 and 820, to determine the wear rate of the tool 900.

[0144] Process

[0145] The system presented above makes it possible to implement a method of working a part using a machine tool M1 whose tool holder 600 is equipped with a tool 900 as described above. An example of the method is presented below in connection with Figure 5.

[0146] The method comprises the following steps. In step 1010, the machine tool M1 is positioned relative to the part P1 in order to be able to work on the part P1 using the tool 900 (by rotation and / or axial movement of the tool 900 relative to the part P1).

[0147] The distance between the part P1 and the frame 100 of the machine tool M1 is equal to a value D1, called the initial value. The drive shaft 400 has a reference axial position P4ref relative to the frame 100 of the machine tool. The reference axial position is represented in Figure 2 as the position of the end of the drive shaft 400 opposite the tool, but said reference axial position may be associated with another part of the drive shaft 400.

[0148] Said axial reference position P4ref is stored by the control unit 8.

[0149] In step 1020, working operations of the part P1 are executed 1020 by controlling the rotation drive motor 2 to drive the tool 900 in rotation, and / or by controlling the feed motor 3 to axially move the tool 900 relative to the part P1.

[0150] For the work of the part to be carried out, the axial movement of the tool 900 is controlled as a function of said axial reference position P4ref of the drive shaft.

[0151] At step 1030, during the processing of part P1, the control unit determines whether the distance between part P1 and the machine frame has changed.

[0152] If not, the working operations of part P1 continue to be executed (step 1020) without further intervention on the drive shaft.

[0153] If so, i.e. in the event of determination 1030 of a change in distance D1' between the part P1 and the frame 100 of the machine, the distance D1 between the part P1 and the frame 100 of the machine tool M1 is equal to a new value D1'.

[0154] The module 840 of the control unit then commands in step 1040, to compensate for the displacement of the part P1, the axial displacement, relative to the frame of the machine tool, of the drive shaft 400 of the tool holder 600 by a distance, called the compensation distance, corresponding to the difference between the new value D1 ' and the initial value D1 . The axial reference position of the drive shaft 400 is then modified to a new axial reference position P4ref' which is recorded by the control unit 8. This new axial reference position P4ref corresponds to the previous axial reference position P4ref plus said compensation distance.

[0155] At step 1050, the work operations of the part P1 continue to be executed according to the new reference position of the shaft P4ref.

[0156] The possibility of controlling the axial displacement of the drive shaft during operation of the machine tool makes it possible to correct the position of the tool and thus maintain the relative position of the tool with respect to the workpiece, even in the event of relative axial movement between the workpiece and the machine tool.

[0157] The control unit 8 is for example in the form of a processor and a data memory in which computer instructions executable by said processor are stored, or in the form of a microcontroller.

[0158] In other words, the functions and steps described can be implemented in the form of a computer program or via hardware components (e.g. programmable gate arrays). In particular, the functions and steps operated by the control unit, in particular for controlling the motors, can be carried out by instruction sets or computer modules implemented in a processor or controller or be carried out by dedicated electronic components or components of the programmable logic circuit type (or FPGA which is the acronym for field-programmable gate array, which literally corresponds to in-situ programmable gate array) or of the application-specific integrated circuit type (or ASIC which is the acronym for application-specific integrated circuit, which literally corresponds to application-specific integrated circuit). It is also possible to combine computer parts and electronic parts.

[0159] The control unit is thus an electronic and / or computer unit. When it is specified that said unit is configured to carry out a given operation, this means that the unit comprises computer instructions and the corresponding execution means which make it possible to carry out said operation and / or that the unit comprises corresponding electronic components.

[0160] The machine tool thus makes it possible to determine a possible relative axial movement between the frame 100 of the machine tool M1 and the workpiece P1, and to correct, in real time, this relative axial movement during the working operation of the workpiece.

[0161] The fact of having a decoupling of the two motors, with in particular a rotation of the first section controlled by the rotary motor 2, which is independent of the axial displacement of the second section controllable by the second motor 3, makes it possible not to generate a geometric defect at the end of the tool 900 when it rotates.

[0162] Indeed, the decoupling between the motors makes it possible to maintain the orientation of the interface between the tool holder 600 and the section of the shaft 4000 provided with the tool holder, the interface being in a reference plane which is perpendicular to the machine axis so as not to generate a geometric defect at the end of the tool 900 during the rotation thereof.

[0163] This correction allows precise work to be carried out on the part, particularly for milling operations, since the milling must generally be positioned very precisely in relation to the surface of the part P1.

[0164] Advantageously, the system can comprise an optical device making it possible to measure the quality of the work carried out on the part P1.

[0165] Applications

[0166] The machine tool may be a machine adapted to carry out various operations such as milling, routing, drilling, threading and nut tightening. The tool equipping the machine is then adapted to carry out said operation.

[0167] As previously mentioned, the machine tool can be mounted on a numerically controlled machine or on a robot, or on a tooling system.

[0168] According to one embodiment, the machine tool comprises a system for measuring the current consumed by the feed motor, and the control unit is configured to adapt the work process, such as the choice of an automatic change of cutting parameters when drilling a multi-material assembly taking into account the type of material being drilled and the second material to be drilled.

[0169] According to one embodiment, the machine tool comprises a sheet metal clamp nose coupling interface configured to be able to change the sheet metal clamp nose, preferably automatically, depending on the workpiece. This interface comprises a centering and a plane support in order to ensure repeatability of the positioning. Preferably, this interface also includes U pneumatic and electrical connections can be used, among other things, for sheet metal pressing functions, distance and orthogonality measurements of the machine M1 in relation to the workpiece P1 to be worked.

[0170] The nose can be a sheet metal clamp nose (or sheet metal clamp) as shown in Figure 2, a concentric collar version nose or a quarter turn version nose.

[0171] The sheet metal clamping nose can be used in automated applications and in applications involving machine tool positioning devices such as robots or CNC machines. The M1 machine tool can also be used in a portable version. Of course, the machine can be used without the nose for specific applications.

[0172] According to a particular aspect, in the case of using a nose, an internal guide for the tool holder is provided inside the nose in particular in order to limit the possible vibration modes.

[0173] According to one embodiment, the nose can thus comprise an internal element for guiding the tool holder as well as a blocking element 530, called a blocker, to block rotation of said tool holder allowing the tool holder to be screwed or unscrewed onto the first section 4001 of the shaft.

[0174] The tool holder is fixed on the first section of the drive shaft by screwing said tool holder onto the first section of the drive shaft. The blocker can be used for mounting or dismounting the tool holder relative to the drive shaft by locking the tool holder on this blocker by male-female cooperation to proceed with screwing or unscrewing said tool holder relative to the drive shaft.

[0175] According to one embodiment, the machine comprises electrical 710 and pneumatic 720 connections allowing the machine nose to be automatically connected and disconnected from the machine.

[0176] The invention is not limited to the embodiments illustrated in the drawings. Accordingly, it should be understood that, where the features mentioned in the appended claims are followed by reference signs, these signs are included solely for the purpose of improving the intelligibility of the claims and are in no way limiting the scope of the claims.

[0177] Furthermore, the term "comprising" does not exclude other elements or steps. Furthermore, features or steps that have been described with reference to one of the embodiments set forth above may also be used in combination with other features or steps of other embodiments set forth above.

Claims

Claims 1. System for working a part (P1), the system comprising a machine tool (M1) which comprises: - a chassis (100); - a drive shaft (400) having a longitudinal axis (A400), said drive shaft (400) being provided with a tool holder (600) to which a tool (900), such as a drilling spindle, is capable of being coupled; - a first motor (2), called a rotation drive motor, which is a rotary motor configured to rotate at least a portion of said drive shaft (400) provided with the tool holder (600); - a second motor (3), called a feed motor, said feed motor being configured to axially move said drive shaft (400) relative to the frame (100) of the machine tool (M1), and preferably being a linear motor; characterized in that the system also comprises a distance measuring device (521) configured to measure a distance representative of the distance between the part (P1) and the frame (100) of the machine tool (M1); - a control unit (8) configured to: - performing work operations on the part (P1) by controlling the rotation drive motor (2) to drive the tool holder (600) in rotation, and / or by controlling the feed motor (3) to axially move the tool holder (600); - determining using the distance measuring device (521) a change in axial distance (D1 '-D1 ) between the frame (100) of the machine tool and the workpiece (P1 ) to be worked resulting from a relative axial displacement between the workpiece (P1 ) and the frame (100) of the machine (M1 ); - depending on the determined distance modification between the machine tool (M1) and the workpiece (P1), controlling the second motor (3) so as to axially move said drive shaft (400) relative to the frame (100) of the machine tool (M1) to compensate for said relative axial displacement between the workpiece (P1) and the frame (100) of the machine (M1); and in that the rotation drive motor (2) and the feed motor (3) are configured so that the axial displacement of said at at least one part of the drive shaft (400) which is provided with the tool holder (600) is controllable independently of the rotation of said at least one part of the drive shaft (400) which is provided with the tool holder.

2. System according to claim 1, in which the feed motor (3) is a linear motor having a primary part (300) fixedly mounted relative to the frame (100) of the machine tool (1), and a secondary part (310), movably mounted, relative to the primary part, in a direction parallel to the axis of the drive shaft (400), the secondary part being fixed to a section (4002) of the drive shaft (400), or formed in a single piece with said section (4002) of the drive shaft (400).

3. System according to claim 2, in which the secondary part (310) comprises a magnet system and the primary part (300) of the feed motor (3) comprises an electrically energized winding system for, in the energized state, creating a magnetic field which interacts with the magnet system in order to generate an electromotive force with an axis parallel to the axis of the drive shaft.

4. System according to any one of the preceding claims, in which the distance measuring device (521) is carried by a movable part (520) of a support device, called a sheet metal pressing nose (520), said movable part (520) of the sheet metal pressing nose being mounted movable relative to a part (510) which is fixed relative to the chassis (100), the movable part (520) being configured to be returned to bear against the part (P1), the distance measuring device (521) being arranged to measure the distance between the movable part (520) and the fixed part (510) of the sheet metal pressing nose.

5. System according to any one of the preceding claims, in which the drive shaft (400) comprises a first section (4001) and a second section (4002) connected to each other by a connecting device (4003), one of the sections being engaged with the feed motor (3), the other section being engaged with the rotation drive motor (2).

6. System according to any one of the preceding claims, in which the drive shaft (400) comprises a first section (4001) and a second section (4002) connected to each other by a connecting device (4003) configured to make the first section (4001) and the second section (4002) integral in axial displacement with each other, while maintaining freedom of rotation of the first section (4001) relative to the second section (4002).

7. System according to claim 5 or 6, in which the first section (4001) to which the tool holder (600) is fixed can be driven in rotation by the rotation drive motor (2), and the second section (4002) can be driven in axial movement by the feed motor (3).

8. A system according to any preceding claim, wherein the system comprises a support system (R1), such as a polyarticulated robot, which carries the machine tool (M1) to enable the machine tool (1) to be positioned at the desired position and orientation relative to the workpiece, the machine tool (M1) being mounted articulated to the support system (R1).

9. System according to the preceding claim, in which the support system (R1) comprises a main base (BT1) and an arm (BRS1), the machine tool (M1) being mounted articulated on the arm (BRS1), said arm (BRS1) comprising one or more sections which can be articulated together, said arm (BRS1) preferably itself being mounted articulated on the base (BT1).

10. System according to any one of the preceding claims, in which the control unit (8) is configured to allow the drive shaft (400) to be moved in order to move the tool (900) axially in a variable speed movement to fragment the chip resulting from the work of the tool (900) on the part (P1) to be worked.

11. Method of working a part using a working system according to any one of the preceding claims, the machine tool (M1) of said working system comprising a tool holder (600) equipped with a working tool (900), the method comprising the following steps: - positioning (1010) of the machine tool (M1) relative to the part (P1) with a view to working the part (P1) using said tool (900); the distance (D1) between the part (P1) and the frame (100) of the machine tool (M1) being equal to a value (D1), called the initial value, the drive shaft (400) having an axial reference position (P4ref) relative to the frame (100) of the machine tool; - performing (1020) working operations on the part (P1) by controlling the rotational drive motor (2) to drive the tool (900) in rotation, and / or by controlling the feed motor (3) to axially move the tool (900); the axial movement of the tool (900) being controlled as a function of said axial reference position (P4ref) of the drive shaft; - during the working of the part (P1), determination (1030) of a change in distance (D1 ') between the part (P1 ) and the frame (100) of the machine, so that the distance (D1 ) between the part (P1 ) and the frame (100) of the machine tool (M1 ) is equal to a new value (D1 '); - compensation (1040) of the displacement of the part (P1) by axial displacement of the drive shaft (400) of the tool holder (600) by a distance, called the compensation distance, corresponding to the difference between the new value (D1') and the initial value (D1) so as to define a new axial reference position (P4ref') of the drive shaft (400), - continuation (1050) of the working operations of the part (P1) according to the new reference position of the shaft (P4ref').

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