System for machining workpiece comprising machine tool and corresponding machining method

Abstract

The invention relates to a system and a method for machining 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 a portion of the drive shaft (400), the portion cooperating with the tool holder (600); and a feed motor (3) for axially moving the drive shaft (400). An apparatus measures a distance representative of a workpiece (P1) and a frame (100) of a machine tool. The control unit (8) is configured to perform a machining operation on the workpiece by controlling the drive motor and / or the feed motor; a change in the axial distance between the frame and the workpiece of the machine tool caused by the relative axial movement between the workpiece and the frame is determined. A second motor is controlled to axially move the drive shaft to compensate for relative axial movement between the workpiece and the frame.

Description

Technical Field

[0001] The present invention generally relates to a system for machining a workpiece including a machine tool. Background Art

[0002] Machine tools are known from the prior art, for example for carrying out milling, trimming, drilling, tapping or nut tightening operations.

[0003] From document US Pat. No. 5,649,451 A a drilling system is known which comprises a fixture for holding a workpiece to be machined and a drilling machine configured to impart simultaneous linear and rotational movements to a drilling tool of the machine.

[0004] The machine includes a first motor and a second motor. The first motor includes a rotor coupled to a ball screw engaged with a helical ring on a drive shaft to convert rotational movement of the rotor into linear movement applied to the drive shaft.

[0005] The second motor includes a rotor coupled to a ball spline that engages with a spline on the drive shaft to transfer rotational movement of the rotor directly to the drive shaft while allowing the drive shaft to move linearly along its axis.

[0006] However, we have noticed that during machining, even in the state where the workpiece is held, the workpiece can move without the operator intending such movement. Thus, for example due to the tool pressing on the workpiece, the workpiece being machined may move backwards, which impairs the quality of the machining performed on the workpiece. In particular, the dimensions obtained for the area of ​​the workpiece thus machined may not correspond to the desired dimensions.

[0007] Document GB2593501A describes a robot that carries a machine tool including a drilling tool. The drilling tool includes an axial drill.

[0008] Document US2012020756A describes a drilling / milling unit suitable for being supported by an industrial robot. The unit comprises a spindle rotatable about an axis. An electric servomotor drives the hollow shaft axially via a belt. The electric servomotor drives the spindle via an associated belt.

[0009] The object of the present invention is to propose a new machine tool and a corresponding machining method, making it possible to overcome all or part of the problems disclosed above. Summary of the invention

[0010] To this end, the object of the present invention is a system for machining a workpiece, the system comprising a machine tool comprising:

[0011] -frame;

[0012] a drive shaft having a longitudinal axis, the drive shaft being provided with a tool holder to which a tool can be coupled, such as a drill spindle;

[0013] a first motor, called the rotary drive motor, which is a rotary motor configured to rotate at least a portion of a drive shaft, which portion of the drive shaft cooperates with the tool holder;

[0014] a second motor, called the feed motor, configured to axially move the drive shaft and preferably being a linear motor;

[0015] Characterized in that the system further comprises a distance measuring device, the distance measuring device being configured to measure a distance between a frame representing the workpiece and the machine tool;

[0016] - a control unit, configured to:

[0017] - performing a machining operation on the workpiece by controlling the rotary drive motor to rotate the tool holder, and / or by controlling the feed motor to axially move the tool holder;

[0018] - using a distance measuring device to determine a change in the axial distance between the workpiece and the frame of the machine tool caused by a relative axial movement between the frame of the machine tool and the workpiece to be machined;

[0019] - controlling the second motor to axially move the drive shaft as a function of a change in the distance determined between the machine tool and the workpiece to be machined, thereby compensating for a relative axial movement between the workpiece and the frame of the machine tool,

[0020] And the rotary drive motor and the feed motor are configured so that axial movement of at least a portion of the drive shaft engaged with the tool holder can be controlled independently of rotation of at least a portion of the drive shaft engaged with the tool holder.

[0021] The axial movement of at least a portion of the drive shaft cooperating with the tool holder can be controlled independently of the rotation of at least a portion of the drive shaft cooperating with the tool holder, which means that the rotation of at least a portion of the drive shaft has no effect on the axial movement of the drive shaft, and vice versa, which makes it possible to accurately and reliably move the drive shaft so as to move it forwards or backwards and thus bring it to a new axial reference position depending on the movement of the workpiece to be machined that must be compensated.

[0022] During operation of the machine tool, the possibility of controlling the axial movement of the drive shaft to which the tool holder is fastened 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 with respect to the workpiece to be machined, even in the event of relative axial movements between the workpiece to be machined and the frame of the machine tool.

[0023] The relative axial movement between the tool and the workpiece to be machined may be due to a movement of the workpiece as a whole (for example a backward movement of the workpiece) or even to a deformation of the workpiece to be machined during the machining it undergoes.

[0024] Taking into account changes in the relative position between the machine tool and the workpiece to be machined, it can be ensured that the process for machining the workpiece is precise and reliable.

[0025] Compensation of the relative axial movement between the machine tool and the workpiece to be machined makes it possible in particular to achieve effective breaking up of the chips generated by the tool machining the workpiece. It should be noted that uncompensated relative axial movement could worsen this breaking up of the chips, or even prevent it. Compensation of the relative axial movement also makes it possible to ensure the desired milling depth.

[0026] In the prior art document GB2593501A, the mobility of the drill bit is only used to perform a back and forth movement for drilling, but the document GB2593501A does not provide for the adjustment of the axial position of the drill bit relative to the machine frame to obtain a new reference position of the drill bit relative to the machine frame in order to compensate for the deviation measured between the machine frame and the workpiece to be processed. In GB2593501A, the robot arm itself is moved to compensate for the deviation between the workpiece and the drilling machine carried by the robot arm.

[0027] No provision is made in document GB2593501A to adjust the axial position of the drill bit relative to a frame of the machine tool, wherein the axial movement of a shaft carrying the drill bit relative to the frame is to be controlled independently of the rotation of said shaft carrying the drill bit, in order to compensate for the measured deviations.

[0028] In document GB2593501A, moving the robot arm carrying the machine tool itself in an attempt to correct for deviations during drilling causes problems of accuracy and reliability, since movement of the entire robot arm (which is heavy) is not as precise as moving the drill head relative to the frame via the feed motor.

[0029] Furthermore, such movements of the robot arm are a result of the movement of the robot's multiple axes, the movement of the machine tool not being well aligned with the drilling axis performed on the workpiece and thus affecting the machining quality of the tool.

[0030] The design of the system according to the invention makes it possible to correct the position of a machining tool, such as a drill bit, in real time while maintaining the drilling direction in the case of a drilling tool, and this is done in a simple and reliable manner.

[0031] In document US2012020756A, a rotary motor rotates the spindle, and the translational movement of the spindle is generated by the speed difference between the rotary motor and another motor. Therefore, there is no complete separation between the two movements of rotation and feed. For example, a slight change in the rotation speed of the rotary motor causes a slight translational movement of the spindle. In addition, in document US2012020756A, the feed movement also depends on the screw nut, which is a mechanical part that may loosen, resulting in axial positioning errors of the spindle, especially during the correction movement.

[0032] The design of the system according to the invention makes it possible to correct the position of a tool coupled to a tool holder carried by a drive shaft by the movement of a single motor, namely the feed motor, and thus to maintain the relative position of the tool holder and therefore the relative position of the tool with respect to the workpiece to be machined, even in the event of relative axial movements between the workpiece to be machined and the frame of the machine tool, and this is done in a precise and reliable manner and in real time.

[0033] The system may also include one or more of the following features in any technically acceptable combination.

[0034] According to one embodiment of the invention, the distance measuring device is carried by a movable part of a supporting device called a blank holder nose, the movable part of the blank holder nose being movably mounted relative to a part fixed to the frame, the movable part being configured to abut against the workpiece backwards, and the distance measuring device being arranged to measure the distance between the movable part of the blank holder nose and the fixed part.

[0035] According to one embodiment of the invention, the drive shaft comprises a first section and a second section connected together by a connecting device, wherein one section is engaged with the feed motor and the other section is engaged with the rotation drive motor.

[0036] According to one embodiment of the invention, the drive shaft comprises a first section and a second section connected together by a connection device, wherein the connection device is configured to enable the first section and the second section to move axially as a whole while maintaining the rotational freedom of the first section relative to the second section.

[0037] According to one embodiment of the invention, the first section to which the tool holder is fastened can be rotated by a rotary drive motor, and the second section can be axially moved by a feed motor.

[0038] According to one embodiment of the invention, the feed motor is a linear motor having a primary component fixedly mounted relative to the frame of the machine tool and a secondary component movably mounted in a direction parallel to the axis of the drive shaft, the secondary component being fastened to a section of the drive shaft or being formed integrally with the section of the drive shaft.

[0039] According to one embodiment of the invention, the system comprises a support system, such as an articulated robot, carrying a machine tool to allow it to be positioned in a desired position and orientation relative to a workpiece to be machined, the machine tool being articulatedly mounted to the support system.

[0040] According to one embodiment, the support system comprises a main base (or frame) and an arm on which the machine tool is hingedly mounted, the arm comprising one or more sections hinged together, the arm preferably itself hingedly mounted on the base.

[0041] According to one embodiment of the present invention, the control unit is configured to allow the drive shaft to move so as to axially move the tool at a variable speed so as to break chips generated by machining the tool on the workpiece to be machined.

[0042] The present invention also relates to a method for machining a workpiece using a machining system according to any one of the aforementioned embodiments, wherein a machine tool of the machining system comprises a tool holder equipped with a machining tool, the method comprising the following steps:

[0043] - positioning the machine tool relative to the workpiece in order to machine it with the tool; the distance between the workpiece 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;

[0044] - performing a machining operation on the workpiece by controlling the rotary drive motor to rotate the tool and / or by controlling the feed motor to axially move the tool;

[0045] The axial movement of the tool is controlled according to the axial reference position of the drive shaft;

[0046] - during machining of the workpiece, determining a change in the distance between the workpiece and the frame of the machine tool so that the distance between the workpiece and the frame of the machine tool is equal to a new value;

[0047] - compensating the movement of the workpiece by an axial movement of the drive shaft of the tool holder by a distance called compensation distance, which corresponds to the difference between the new value and the initial value, in order to define a new axial reference position of the drive shaft,

[0048] - continuing the machining operation on the workpiece according to the new reference position of the axis.

[0049] According to a particular aspect, in order to compensate for the movement of the workpiece, the axial movement of the drive shaft is performed while keeping the frame of the machine tool carrying the motor stationary in the ground reference system. Thus, the drive shaft preferably moves along and within the frame of the machine tool, rather than the frame moving in the ground reference system.

[0050] According to one embodiment of the invention, the rotary drive motor comprises a stator fixedly mounted relative to a frame of the motor, and a rotor directly engaged with the drive shaft.

[0051] Preferably, the stator comprises a winding system and the rotor comprises a magnet system, so that the supply of the winding system generates a magnetic field that interacts with the magnet system. The rotating electrical machine thus generates a radial electromotive force (electromagnetic torque) which rotates at least a portion of the drive shaft that is engaged with the rotor. The electromotive force generated by the rotating electrical machine is radial, while the electromotive force generated by the feed motor is axial.

[0052] Advantageously, the secondary of the feed motor is directly engaged with said drive shaft.

[0053] 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 carried by a component integral with the drive shaft or directly integrated into the drive shaft. Supplying the winding system generates a magnetic field that interacts with the magnet system.

[0054] The feed motor produces an axial EMF which translates the drive shaft which is engaged with the secondary of the feed motor. The EMF produced by the feed motor is axial, while the EMF produced by the rotary motor is radial.

[0055] The fact that the drive shaft carries the magnet system and that the frame carries the winding system, which is heavier than the magnet system, makes it possible not only to facilitate the wiring of the power supply for the corresponding electric motor but also to limit the mass to be moved, i.e. the mass of the drive shaft, which improves the precision and reliability of the movement of the drive shaft, in particular the precision and reliability of the axial movement.

[0056] According to a particular aspect, a large portion of the drive shaft extends within the frame of the machine tool.

[0057] A driver and a driven element are said to be in direct engagement when the speed of movement of the driver element is the same as the speed of movement of the driven element. There is no relative sliding between the elements. Intermediate components may be present, but there is no relative movement between the driver and driven components. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Other characteristics and advantages of the present invention will appear from the following description, which is illustrative only and not limiting, and must be read with reference to the accompanying drawings, in which:

[0059] Figure 1 is a schematic diagram of a machine tool for machining on a workpiece carried by a movable support system such as a robot according to one embodiment of the present invention;

[0060] Figure 2 shows a cross-sectional view of a machine tool according to one embodiment of the present invention, the machine tool being equipped with a tool in contact with a workpiece to be machined;

[0061] Figure 2A Shows Figure 2 A cross-sectional view of a machine tool, wherein the workpiece to be machined is axially moved relative to the machine tool, which results in a relative axial movement of the workpiece to be machined relative to the tool;

[0062] Figure 2B Shows Figure 2A An axial cross-sectional view of a machine tool, wherein the axial movement of the tool is obtained by the axial movement of the drive shaft of the tool to compensate for the relative axial movement of the workpiece to be machined relative to the tool;

[0063] Figure 3 is a schematic axial cross-sectional view of a machine tool according to another embodiment;

[0064] Figure 4 is a schematic axial cross-sectional view of a machine tool according to another embodiment;

[0065] Figure 5 is a flow chart of a machining method having a machining system according to one embodiment. DETAILED DESCRIPTION

[0066] The concept of the present invention will be described more completely below with reference to the accompanying drawings, in which embodiments of the concept of the present invention are shown. In the accompanying drawings, the size and relative size of the elements may be exaggerated for clarity. In all the accompanying drawings, similar reference numerals represent similar elements. However, this concept of the present invention can be implemented in a variety of different forms and should not be interpreted as being limited to the embodiments described herein. On the contrary, these embodiments are proposed to make this specification complete and to convey the scope of the concept of the present invention to those skilled in the art.

[0067] References throughout the specification to "one embodiment" mean that a particular feature, structure, or characteristic described in conjunction with one embodiment is included in at least one embodiment of the present invention. Thus, the phrase "in one embodiment" appearing in various places 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.

[0068] With reference to the figures, a system for machining a workpiece P1 is shown. The machining system comprises a machine tool M1 comprising a frame 100 and a machining assembly carried by the frame 100, the machining assembly comprising motorization systems 2, 3 and a drive axis 400.

[0069] The drive shaft 400 is provided at one end with a tool holder 600 capable of receiving a tool 900 for machining on the workpiece P1. Figure 2 , 2A In the embodiment shown in 2B, only one end of the drive shaft 400 is provided with a tool holder, and thus a tool is provided. Figure 3 As shown, it can be provided that each end of the drive shaft 400 is provided with a tool holder 600 and thus with a tool 900. The drive shaft 400 can itself be driven by the motorized system 2, 3 controlled by a control unit 8 as described below.

[0070] The motorized systems 2, 3 are configured such that not only can at least one portion 4001 of the drive shaft 400, to which the tool holder 600 is fastened, be rotated so as to be able to rotate the tool 900 fastened to the tool holder 600 in a removable manner, but also said portion 4001 of the drive shaft 400 can be axially moved (preferably by axial movement of another portion 4002 of the drive shaft, as explained below) so as to allow the tool holder 600 and therefore the tool 900 connected to the tool holder to move axially.

[0071] The fact of having the thrust axis (direction) corresponding to the movement axis of the drive shaft (also called feed axis) colinear with the axis of the tool allows precise and reliable machining on the workpiece.

[0072] As described in detail below, when the position of the workpiece to be machined undergoes relative axial movement relative to the machine tool frame, the machine tool enables reliable and accurate compensation of the axial position of the tool holder drive shaft relative to the workpiece P1 in real time, and thus reliable and accurate compensation of the axial position of the tool.

[0073] The reliability of this compensation results from the separation of the rotational movement of the portion of the drive shaft to which the tool holder 600 is fastened from the translational movement applied (directly or indirectly) to the portion of the drive shaft to which the tool holder is fastened.

[0074] According to one embodiment and as shown in the drawings, the drive shaft 400 includes a first section 4001 and a second section 4002 that are integral with each other in axial movement.

[0075] The first section 4001 to which the tool holder 600 is fastened can be rotated by a first motor 2 presented below. The second section 4002 can be axially moved by a second motor 3 presented below and is arranged together with the first section 4001 to axially move said first section 4001 independently of the rotation of said second section 4002. The two drive shaft sections are collinear.

[0076] In other words, the axial movement of the second segment 4002 causing the axial movement of the first segment 4001 has no effect on the rotation of the first segment 4001 to which the tool holder 600 is fastened. Conversely, the rotation of the first segment 4001 has no effect on the axial positioning of the second segment 4002. This ensures good control of the process parameters by making the control of the rotational and translational movements of the segments of the drive shaft of the tool holder independent of each other, while ensuring the thrust on the tool axis, which makes it possible to reliably and accurately obtain the desired final geometry of the workpiece to be machined during machining operations such as drilling and countersinking.

[0077] like Figure 1 As shown, the machine tool can be supported by a support system R1, such as a multi-joint robot. The support system R1 can also be a CNC machine tool or a specific process equipment.

[0078] It may be provided that the support system R1 itself is mounted on a carriage system configured to move in several directions relative to the workpiece P1 to be machined. The support system and / or carriage system make it possible to position the machine tool and thus the tool according to the desired position and orientation relative to the workpiece to be machined.

[0079] exist Figure 1 In the example shown, the support system R1 comprises a main base (or frame) BT1 and an arm BRS1. The machine tool M1 is mounted in an articulated manner on the arm BRS1. The arm BRS1 comprises one or more sections that can be articulated together. The arm BRS1 is preferably itself mounted in an articulated manner on the base BT1.

[0080] Advantageously, the machining system comprises means for positioning the machine M1 relative to the workpiece P1 to be manufactured, so that the position and / or orientation of the machine relative to the workpiece P1 is precisely known, in particular before starting machining of the workpiece.

[0081] exist Figure 1 In the example shown, the support system R1 can be moved independently of the workpiece P1. For example, the support system R1 can be positioned so that the machine tool M1 has Figure 1 The position and orientation are shown by short dashed lines.

[0082] The tool 900 is, for example, a drill 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 coaxial with the axis A400 of the drive shaft 400.

[0083] Motorized system

[0084] As mentioned above, the machine tool M1 comprises an electromechanical system including a first motor 2 , referred to as a rotary drive motor, configured to rotary drive at least a portion 4001 of a shaft 400 .

[0085] The motorization system also comprises a second motor 3, called the feed motor, which makes it possible to move said drive shaft 400 axially, preferably in direct engagement with a segment 4002 that is independent of the rotation of the segment 4001 that carries the tool 900 through 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 affecting the rotation of said shaft.

[0086] The rotary drive motor 2 is mounted to rotate integrally with a section 4001 of a drive shaft 400 provided with a tool holder 600 for rotary drive thereof, while being slidably connected to the section 4001 to allow axial movement of the section 4001 controlled by the feed motor 3 .

[0087] The rotary drive motor 2 and the feed motor 3 can be controlled independently of each other. As described above, each motor can act on the drive shaft 400 independently of the action of the other motor on the shaft under the control of the control unit 8: one of the motors controls only the rotation of the shaft, and the other controls only its axial movement. As described below, the two motors act on two colinear parts of the drive shaft, respectively, which makes it possible that when the tool holder rotates, no geometric defects are generated at the tip of the tool 900 fastened to the tool holder.

[0088] Preferably, the rotation axis of the rotary drive motor 2 is coaxial with the axis of the feed motor 3 .

[0089] Drive shaft

[0090] As mentioned above, in Figure 1 and 2 In the illustrated embodiment, the drive shaft 400 includes a first section 4001 and a second section 4002, wherein the first section can be rotated by a motor 2 and a tool holder 600 is fixed at one end thereof, and the second section can be axially moved by a feed motor 3 so as to be able to push or pull axially on the first section 4001, thereby causing the tool 900 associated with the first section 4001 to move axially through the tool holder.

[0091] The connection 4003 between the first segment 4001 and the second segment 4002 is configured to enable the first segment 4001 and the second segment 4002 to move axially as a whole while maintaining the rotational freedom of the second segment 4002 relative to the first segment 4001 .

[0092] The connection 4003 may thus be made in the form of a pivot connection, wherein the pivot axis is coaxial with the axis A400 of the drive shaft 400. Alternatively, the connection 4003 may be made in the form of a ball joint.

[0093] This design of the machine makes it possible to obtain independence of the action of one motor on the drive shaft relative to the action of the other motor on said drive shaft.

[0094] Thus, the rotation of the tool 900 and its axial position relative to the machine frame can be controlled independently of one another and thus in a reliable and precise manner.

[0095] The connection 4003 between the two segments 4001 , 4002 has no axial play and allows the second segment 4002 to rotate freely relative to the first segment 4001 .

[0096] This compact structure makes it possible to provide a thrust on the tool 900 in the axis of the drive shaft (spindle axis) and to decouple the control of the two motors.

[0097] This design facilitates the control and monitoring of cycles, such as drilling cycles with discontinuous cutting, allowing the breakage of chips and thus facilitating their evacuation during operation.

[0098] exist Figure 3 (or Figure 4 ), the segment 4002' that cooperates with the tool holder is engaged with the feed motor 3, while the other segment 4001' is engaged with the rotation drive motor 2. The segment 4002' that can be controlled to move axially by the feed motor 3 thus extends between the tool 900 and the segment 4001' that can be controlled to rotate by the motor 2. In this case, the connecting member 4003 is a rigid connecting member, so that the segments 4001', 4002' are integrated in axial movement and rotation.

[0099] The portion of the drive shaft 400 engaged with the feed motor 3 is different from the portion of the drive shaft 400 engaged with the rotation drive motor 2 .

[0100] According to one embodiment, two parts of the shaft of the machine tool M1 are drilled, preferably axially in their centre, in order to allow the passage of a cooling liquid for the drilling operation.

[0101] Rotating electric machines

[0102] The rotary motor 2 corresponds to a spindle motor that rotates the first portion 4001 of the drive shaft 400 carrying the tool 900. The rotary motor 2 comprises a stator 200 and a rotor 210 fixed relative to the frame 100 of the machine M1, the rotation speed of which can be controlled by the control module 810 of the control unit 8, as described below.

[0103] According to one embodiment, the first section 4001 of the drive shaft 400 is a splined section rotationally coupled to the rotor 210 of the electric machine 2 by a toothing system integral with the rotor 210 , the toothing system cooperating with the splined section.

[0104] Preferably, the meshing system comprises axially spaced primary and secondary meshing members 220, 230 to distribute the drive torque and increase the rigidity of the assembly and the rotational accuracy of the first section 4001 due to the longer guide of said first section.

[0105] Preferably, the stator of the rotating electrical machine comprises a winding system and the rotor comprises a magnet system, so that the energization of the winding system generates a magnetic field interacting with the magnet system. The rotating electrical machine thus generates a radial electromotive force (electromagnetic torque) which rotates at least a portion of the drive shaft engaged with the rotor.

[0106] Feed motor

[0107] Preferably, the feed motor 3 is a linear motor configured to control the axial movement of the second segment 4002. The use of a linear motor enables axial movement of the second segment 4002, and thus axial movement of the first segment 4001 axially coupled thereto, without rotating the second segment 4002 or increasing the rotational movement.

[0108] As shown in the figure, the feed motor 3 includes a primary stage 300 and a secondary stage 310 .

[0109] The primary 300 is fixed relative to the frame 100 of the machine M1 and the secondary 310, fastened to 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 feed module comprise several primaries and several secondaries, respectively. The feed motor generates an axial electromotive force (with an axis parallel to the drive shaft) which translates the drive shaft engaged with the secondary of the feed motor.

[0110] According to one embodiment of the invention, the primary part of the feed motor comprises a winding system carried by the frame and powered, and the secondary part 310 comprises a magnet system. The secondary of the feed motor comprises a magnet system carried by a component integral with the drive shaft or directly integrated into the drive shaft. The power supply of the winding system generates a magnetic field that interacts with the magnet system.

[0111] The fact that the drive shaft carries the magnet system and that the frame carries the winding system, which is heavier than the magnet system, makes it possible not only to facilitate the wiring of the power supply to the corresponding motor, but also to limit the mass to be moved, i.e. the mass of the drive shaft, which improves the precision and reliability of the movement of the drive shaft, in particular the axial movement. The distribution of the winding system and the magnet system could be reversed, but would be less advantageous.

[0112] The winding system of the feed motor can be powered so as to move the magnetic field generated along the axis of the drive shaft at a given speed. Preferably, the control unit makes it possible to control the movement speed of the generated magnetic field according to the desired movement speed to control the axial movement speed of the drive shaft.

[0113] As described in detail below, in order to compensate for the movement of the workpiece to be machined, the movement of the drive shaft relative to the machine frame to obtain a new reference position P4ref of the drive shaft is obtained by controlling a single motor as a feed motor.

[0114] exist Figure 1 and Figure 2 In the example shown, the secondary 310 is mounted to translate integrally with the segment 4002 in a direction parallel to the axis of the segment 4002 (which also corresponds to the axis of the segment 4001 of the drive shaft 400). The axial movement of the secondary 310 can be controlled by the control module 820 of the control unit 8.

[0115] The axial movement of the secondary 310 of the motor 3 causes the axial movement of the second section 4002 of the drive shaft. The secondary 310 of the motor 3 and the second section 4002 can be made into one and the same component.

[0116] As will be described below, the feed motor 3 makes it possible to move the drive shaft 400 to compensate for the difference between the frame 100 of the machine M1 and the workpiece P1 ( Figure 2 , 2A , 2B) relative axial movement.

[0117] The fact of compensating the relative axial movement of the workpiece P1 relative to the frame 100 of the machine by simply moving the secondary 310 of the feed motor 3 connected to the segment 4002 of the drive shaft 400, compared to the complete movement of the machine M1, makes it possible to limit the size of the feed motor 3 and therefore the size (total size and mass) of the machine M1. Limiting the moving mass makes it possible to increase the mechanical bandwidth of the system.

[0118] In other words, during a machining operation on the workpiece P1, if a relative axial movement between the workpiece P1 and the frame 100 of the machine is detected, the tool 900 can be axially moved by moving the secondary 310 of the feed motor relative to the primary 300 of the feed motor 3 and therefore relative to the frame 100 of the machine, which makes it unnecessary to move the entire machine tool to perform axial correction of the relative axial movement between the workpiece and the frame of the machine during the machining operation on the workpiece.

[0119] Of course, when the machine tool is located on a mobile system such as the support system R1, preferably itself carried by a carriage system, the entire machine remains movable relative to the workpiece to pre-position and / or orient the tool 900 according to the machining to be performed on the workpiece.

[0120] The motor 3 manages the feeding of the second section 4002 of the drive shaft, ie the axial movement of the second section 4002 , and therefore the axial movement of the tool 900 , by direct translational drive.

[0121] The fact that the movement is transmitted directly between the feed motor 3 and the second section 4002 of the drive shaft without a reduction gear such as a screw nut allows, on the one hand, good efficiency and, on the other hand, direct and therefore noise-free force feedback information.

[0122] This 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 .

[0123] The independence of the rotation of the first section 4001 with respect to its axial movement makes it possible to implement control and monitoring circuits, such as a drilling cycle with discontinuous cuts, allowing the breakup of the chips, which therefore facilitates their evacuation during operation.

[0124] To compensate for the movement of the workpiece, the axial movement of the drive shaft is performed while keeping the frame of the machine tool carrying the motor stationary in the ground reference system. Therefore, the drive shaft preferably moves along and within the frame of the machine tool, rather than a frame that moves in the ground reference system.

[0125] According to a particular aspect, a large portion of the drive shaft extends within the frame of the machine tool.

[0126] Advantageously, the secondary of the feed motor is in direct engagement with the drive shaft. The drive element and the driven element are said to be in direct engagement when the speed of movement of the drive element is the same as the speed of movement of the driven element. There is no relative sliding between the elements. There may be intermediate components, but there is no relative movement between the drive element and the driven element.

[0127] Distance determination system

[0128] The machine tool comprises a distance measuring device 521 configured to measure a distance representative of the distance between the workpiece P1 and the frame 100 of the machine tool, in particular during machining of the workpiece P1 by the tool 900 .

[0129] The distance measuring device 521 is connected to the control unit 8 which is configured to determine the change in the axial distance between the frame 100 of the machine tool and the workpiece P1 to be machined using a distance change determination module 830 .

[0130] As described below, when the module 830 determines that the distance D1 between the frame 100 of the machine tool and the workpiece P1 to be machined has changed to the distance D1', for example, when the distance difference D1-D1' is greater than a threshold value, the module 840 controls the axial movement of the drive shaft 400 to change the axial reference position P4ref of the shaft 400, thereby compensating for this relative change in the distance between the workpiece P1 and the frame 100 of the machine. The axial reference position of the drive shaft is stored by the control unit 8 so that machining instructions on the workpiece can be executed according to the axial reference position of the drive shaft, the machining instructions including commands for the axial (and rotational) movement of the shaft 400, and therefore including commands for the axial (and rotational) movement of the tool 900.

[0131] Control unit

[0132] As mentioned above, the control unit 8 comprises a rotation control module 810 which makes it possible to control the rotation speed of the rotary drive motor 2. The rotation control module 810 is preferably configured to allow a constant rotation speed of the motor 2, and therefore of the tool, to be maintained, while allowing the speed of the tool to be varied as required.

[0133] The control unit 8 further comprises a feed control module 820 making it possible to control the feed motor 3 to control the axial movement of the second section 4002 and thus the axial movement of the first section 4001 equipped with the tool holder 600 .

[0134] The machine tool comprises a sensor for the position of the segment 4002 engaging the feed motor 3. The position sensor is connected to the control unit 8 to allow the control unit to know the position of the segment precisely and to make it possible to modify the amplitude of the waveform of the feed movement in real time.

[0135] Advantageously, the feed control module 820 is configured such that the axial movement of the second section 4002 can be controlled at a constant speed.

[0136] Preferably, the feed control module 820 can also be configured to control the main axial movement of the second section 4002, wherein the oscillation is superimposed on the main axial movement.

[0137] The control unit makes it possible to control the rotary drive motor 2 and the feed motor 3 independently of each other while allowing them to be controlled simultaneously.

[0138] The control unit 8 comprises a control module 840 configured to control the feed motor 3 to move the drive shaft axially by a distance equal to the determined change in distance, after the change in distance between the frame 100 of the machine tool M1 and the workpiece P1 to be machined, determined by the module 830. The drive shaft has a new axial reference position P4ref, according to which the machining instructions on the workpiece P1 can continue to be executed, which makes it possible to compensate for the relative axial movement of the workpiece P1 with respect to the frame of the machine M1.

[0139] Thus, given a relative axial displacement of a given value between frame 100 of machine tool M1 and workpiece P1 to be manufactured, the machining therefore makes it possible to compensate the axial position of shaft 400 and therefore of tool 900 in real time by the same value.

[0140] It may be provided that the machine tool comprises an interface which makes it possible to select one or more oscillation parameters (frequency and / or amplitude) and / or the shape of the signal (sinusoidal, triangular, trapezoidal, etc.).

[0141] It can be provided that these parameters can be selected according to given criteria such as the hardness of the material and can be varied in real time to promote chip breakage.It can also be provided that the oscillation parameters can be automatically defined or varied by a module of the control unit of the machine according to the results of a machining test phase on the material to be machined.

[0142] According to one embodiment, the control unit 8 is configured to vary in real time the settings provided to each control module 810 and 820 , depending on data relating to the current consumed by the feed motor 3 and data provided by the system for determining distance variations between the machine M1 and the workpiece P1 .

[0143] According to one embodiment, the distance variation between the machine tool M1 and the workpiece P1 to be manufactured can be measured using a distance sensor 521, which is configured to measure the distance between a bearing device (called blank holder nose) and a part 510 of the machine frame 100, mounted at the tip of the machine nose on a part of the machine, i.e. at the end where the tool of the machine is located, the bearing device comprising a part 520 for abutting against the workpiece P1 to be machined, which part 520 is movable relative to the part in a direction parallel to the axis of the drive shaft. It can also be provided that the distance variation is provided by a distance measuring sensor 521 mounted on the part 510.

[0144] The component 520 has a through hole for the passage of the machining tool. The component 520 is mounted axially movably relative to the frame, for example by a return spring, to allow it to abut against the workpiece to be machined backwards, so that the relative axial movement between the workpiece to be machined and the frame of the machine in a direction away from the workpiece P1 causes an axial spacing of the component 520 of the blank holder system relative to the component 510 associated with the frame of the machine.

[0145] Alternatively, the blank holder system may be mounted on a support external to the machine tool and fixed relative to said machine tool. The blank holder system holds the fixed part 510 and the movable part 520 itself in contact with the workpiece P1 to be manufactured, which has at least one distance sensor to measure the relative axial movement between the two parts 520, 510.

[0146] Preferably, the machining system comprises means for measuring the orthogonality of the tool of the machine tool M1 (or the axis of the drive shaft 400 ) and the workpiece P1 .

[0147] exist Figure 2 , the blank holder nose is initially supported on the workpiece P1 so that the distance between the part 520 of the blank holder nose and the part 510 fastened to the frame 100 is equal to D1.

[0148] Figure 2A It is shown that during machining on a workpiece P1, said workpiece P1 moves backwards relative to the frame of the machine: the movable part 520 of the blank holder nose resting against the workpiece then moves a distance D1' away from the frame 100. In particular, Figure 2 , 2A 2B shows the relative movement between the machine tool M1 and the workpiece P1 to be machined and the related compensation at the machine tool axes to keep the tool 900 in the same position relative to the workpiece P1 in real time.

[0149] The distance change determination system thus determines that the workpiece P1 has moved axially by a distance D1 - D1 ′.

[0150] The compensation module 840 of the control unit 8 controls the axial movement of the drive shaft, feeding it here a distance equal to D1-D1' to compensate for the backward movement of the workpiece relative to the frame, so that the reference position P4ref (original position) of the shaft 400 changes to the position P4ref', wherein the distance between the reference position P4ref' and P4ref is equal to the distance D1-D1', and the reference position is, for example, defined as the position of the free end of the segment 4002 relative to the frame 100.

[0151] Therefore, if Figure 2BAs shown, the position of the drive shaft 400 (machine axis) relative to the workpiece P1 is compensated by the value of the relative axial movement between the workpiece P1 and the machine frame, that is, the value of D1'-D1, and the position of the drive shaft relative to the frame has been fed (in the direction of the workpiece P1) a distance D1-D1'.

[0152] 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 infer the relative position of the tool 900 and the workpiece P1 before the tool is located inside this workpiece.

[0153] 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 infer the relative position of the cutting tool 900 relative to the material changes in the workpiece P1 to be machined, and thus adjusts the cutting parameters in real time to adapt to the material to be machined according to the adopted strategy.

[0154] It may also be provided that the module 830 of the control unit 8 analyses in real time the data from the two control modules 810 and 820 in order to determine the wear rate of the tool 900 .

[0155] method

[0156] The above system makes it possible to implement a method for machining a workpiece using a machine tool M1, the tool holder 600 of which is provided with a tool 900 as described above. Figure 5 Give an example of this method.

[0157] The method comprises the following steps: In step 1010 , the machine tool M1 is positioned relative to the workpiece P1 so as to be able to machine the workpiece P1 using the tool 900 (by rotation and / or axial movement of the tool 900 relative to the workpiece P1 ).

[0158] The distance between the workpiece P1 and the frame 100 of the machine tool M1 is equal to a value D1 referred to as an initial value. The drive shaft 400 has an axial reference position P4ref relative to the frame 100 of the machine tool. The axial reference position is Figure 2 , the position is shown as the end of the drive shaft 400 opposite the tool, but the axial reference position can be associated with another part of the drive shaft 400.

[0159] The axial reference position P4ref is stored by the control unit 8 .

[0160] In step 1020 , a machining operation is performed 1020 on the workpiece P1 by controlling the rotary drive motor 2 to rotate the tool 900 , and / or by controlling the feed motor 3 to axially move the tool 900 relative to the workpiece P1 .

[0161] In order to perform machining on a workpiece, the axial movement of the tool 900 is controlled according to the axial reference position P4ref of the drive shaft.

[0162] In step 1030 , during machining on the workpiece P1 , the control unit determines whether the distance between the workpiece P1 and the machine frame has changed.

[0163] If not, the machining operation on the workpiece P1 continues (step 1020) without additional intervention of the drive axis.

[0164] If yes, ie if it is determined 1030 that the distance D1 ′ between the workpiece P1 and the frame 100 of the machine has changed, the distance D1 between the workpiece P1 and the frame 100 of the machine tool M1 is equal to the new value D1 ′.

[0165] Then, the module 840 of the control unit controls in step 1040 that, in order to compensate for the movement of the workpiece P1, the axial movement of the drive shaft 400 of the tool holder 600 relative to the machine frame is compensated by a distance, which is called the compensation distance, corresponding to the difference between the new value D1' and the initial value D1. Then, the axial reference position of the drive shaft 400 is changed to a new axial reference position P4ref' recorded by the control unit 8. This new axial reference position P4ref' corresponds to the previous axial reference position P4ref plus the compensation distance.

[0166] In step 1050 , the machining operation P1 on the workpiece is continued according to the new reference position P4ref′ of the axis.

[0167] The possibility of controlling the axial movement of the drive shaft during operation of the machine tool makes it possible to correct the position of the tool and thus maintain its relative position with respect to the workpiece to be machined, even in the event of a relative axial movement between the workpiece to be machined and the machine tool.

[0168] The control unit 8 is for example in the form of a processor and a data memory in which computer instructions executable by the processor are stored, or even in the form of a microcontroller.

[0169] In other words, the functions and steps described can be implemented in the form of a computer program or via hardware components (e.g. a programmable gate network). In particular, the functions and steps operated by the control unit, in particular for controlling the motor, can be implemented by an instruction set or computer module implemented in a processor or controller, or by dedicated electronic components or components of the field programmable gate array (FPGA) type or application specific integrated circuit (or ASIC) type. It is also possible to combine computer components and electronic components.

[0170] Thus, the control unit is an electronic and / or computer unit. When it is specified that the unit is configured to perform a given operation, this means that the unit comprises computer instructions and corresponding execution means enabling the execution of said operation, and / or the unit comprises corresponding electronic components.

[0171] The machine tool can thus determine possible relative axial movements between the frame 100 of the machine tool M1 and the workpiece P1 to be manufactured and correct these relative axial movements in real time during a machining operation on the workpiece.

[0172] The decoupling of the two motors, in particular the rotation of the first part controlled by the rotary motor 2, is independent of the axial movement of the second part, which can be controlled by the second motor 3, which allows no geometric defects to be generated at the tip of the tool 900 during its rotation.

[0173] In fact, the separation 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 on which it is provided, in a reference plane perpendicular to the machine axis, so as not to create geometric defects during the rotation of the tip of the tool 900 .

[0174] Since the countersink generally has to be positioned very accurately relative to the surface of the workpiece P1 , this correction makes it possible to carry out precise machining on the workpiece, in particular for countersinking operations.

[0175] Advantageously, the system may comprise optical means making it possible to measure the quality of the machining performed on the workpiece P1 .

[0176] application

[0177] The machine tool may be a machine adapted to perform different operations, such as milling, trimming, drilling, tapping and nut tightening operations.The tool mounted to the machine is then adapted to perform said operations.

[0178] As mentioned earlier, machine tools can be embedded on CNC machines or robots, or embedded on tool systems.

[0179] 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 machining process, for example to select automatic changes in cutting parameters taking into account the type of material being drilled and the second material to be drilled when drilling a multi-material component.

[0180] According to one embodiment, the machine tool comprises a connection interface of the blank holder nose, which is configured to be able to change the blank holder nose, preferably automatically, according to the workpiece to be machined. The interface comprises centering and planar bearings to ensure repeatability of positioning. Preferably, the interface also comprises pneumatic and electrical connections, which can be used for blank holder functions, distance and orthogonality measurement of the machine M1 relative to the workpiece P1 to be machined, etc.

[0181] The nose may be Figure 2 Shown is a blank retainer nose (or blank retainer), concentric collar type nose or quarter turn nose.

[0182] The blank holder nose can be used in automation applications involving a device for positioning a machine tool, such as a robot or a CNC machine. The machine tool M1 can also be used in a portable form. Of course, for specific applications, the machine can be used without a nose.

[0183] According to a particular aspect, in the case of use of a nose, an internal guide of the tool holder is provided within the nose, in particular in order to limit possible vibration modes.

[0184] According to one embodiment, the nose may therefore comprise an internal element for guiding the tool holder and a blocking element 530 , referred to as a blocker, to block the rotation of said tool holder, thereby making it possible to tighten or loosen the tool holder on the first section 4001 of the shaft.

[0185] The tool holder is fastened to the first part of the drive shaft by screwing the tool holder onto the first part of the drive shaft. The tool holder is blocked on the blocker by the cooperation of the convex and concave shapes to tighten or loosen the tool holder relative to the drive shaft, and the blocker can be used for installing or removing the tool holder relative to the drive shaft.

[0186] According to one embodiment, the machine comprises an electrical connection 710 and a pneumatic connection 720, enabling automatic connection and disconnection of the machine nose to the machine.

[0187] The present invention is not limited to the embodiments shown in the drawings. Therefore, it must be understood that when features mentioned in the appended claims are followed by reference signs, these signs are only used for the purpose of improving the intelligibility of the claims and in no way limit the scope of the claims.

[0188] Furthermore, the term "comprising" does not exclude other elements or steps. In addition, features or steps described with reference to one of the above embodiments may also be used in combination with other features or steps of other embodiments described above.

Claims

1. A system for machining a workpiece (P1), the system comprising a machine tool (M1), the machine tool comprising: - a frame (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), for example a drill spindle, can be coupled; a first motor (2), referred to as a rotary drive motor, which is a rotary motor configured to rotate at least a portion of the drive shaft (400) cooperating with the tool holder (600); a second motor (3), called feed motor, configured to move the drive shaft (400) axially relative to the frame (100) of the machine tool (M1), and preferably a linear motor; Characterized in that the system further comprises a distance measuring device (521), the distance measuring device being configured to measure the distance between the frame (100) representing the workpiece (P1) and the machine tool (M1); - a control unit (8) configured to: - performing a machining operation on the workpiece (P1) by controlling the rotary drive motor (2) to rotate the tool holder (600) and / or by controlling the feed motor (3) to axially move the tool holder (600); - using the distance measuring device (521) to determine the change in the axial distance (D1'-D1) between the frame (100) of the machine tool and the workpiece (P1) to be machined, caused by the relative axial movement between the workpiece (P1) and the frame (100) of the machine (M1); - controlling the second motor (3) to axially move the drive shaft (400) relative to the frame (100) of the machine tool (M1) as a function of the variation of the distance determined between the machine tool (M1) and the workpiece (P1) to be machined, thereby compensating the relative axial movement between the workpiece (P1) and the frame (100) of the machine (M1); And wherein, the rotary drive motor (2) and the feed motor (3) are configured so that the axial movement of at least a portion of the drive shaft (400) that cooperates with the tool holder (600) can be controlled independently of the rotation of at least a portion of the drive shaft (400) that cooperates with the tool holder.

2. The system according to claim 1, wherein: The feed motor (3) is a linear motor having a primary component (300) fixedly mounted relative to the frame (100) of the machine tool (1) and a secondary component (310) movably mounted relative to the primary component in a direction parallel to the axis of the drive shaft (400), the secondary component being fastened to a section (4002) of the shaft drive (400) or being formed integrally with the section (4002) of the drive shaft (400).

3. The system according to claim 2, wherein: The secondary component (310) includes a magnet system, and the primary component (300) of the feed motor (3) includes a powered winding system, which is used to generate a magnetic field that interacts with the magnet system in a powered state to generate an electromotive force with an axis parallel to the axis of the drive shaft.

4. A system according to any one of the preceding claims, wherein: The distance measuring device (521) is carried by a movable part (520) of a supporting device called a blank holder nose (520), the movable part (520) of the blank holder nose being movably mounted relative to a fixed part (510) of the frame (100), the movable part (520) being configured to abut against the workpiece (P1) backwards, and the distance measuring device (521) being arranged to measure the distance between the movable part (520) and the fixed part (510) of the blank holder nose.

5. A system according to any one of the preceding claims, wherein: The drive shaft (400) comprises a first section (4001) and a second section (4002) connected together by a connecting device (4003), one of the two sections being engaged with the feed motor (3) and the other section being engaged with the rotary drive motor (2).

6. A system according to any one of the preceding claims, wherein: The drive shaft (400) includes a first section (4001) and a second section (4002) connected together by a connecting device (4003), and the connecting device is configured to enable the first section (4001) and the second section (4002) to move axially as a whole while maintaining the rotational freedom of the first section (4001) relative to the second section (4002).

7. The system according to claim 5 or 6, wherein: The first section (4001) to which the tool holder (600) is fastened can be rotated by the rotary drive motor (2), and the second section (4002) can be axially moved by the feed motor (3).

8. A system according to any one of the preceding claims, wherein: The system comprises a support system (R1), such as an articulated robot, which carries the machine tool (M1) to allow the machine tool (1) to be positioned in a desired position and orientation relative to the workpiece to be machined, the machine tool (M1) being articulatedly mounted to the support system (R1).

9. System according to the preceding claim, wherein: The support system (R1) comprises a main base (BT1) and an arm (BRS1), the machine tool (M1) being hingedly mounted on the arm (BRS1), the arm (BRS1) comprising one or more parts that can be hinged together, and the arm (BRS1) is preferably itself hingedly mounted on the base (BT1).

10. A system according to any one of the preceding claims, wherein: The control unit (8) is configured to allow the drive shaft (400) to move so that the tool (900) moves axially at a variable speed, thereby breaking chips generated by machining the workpiece (P1) by the tool (900).

11. A method for machining a workpiece using a machining system according to any one of the preceding claims, wherein a machine tool (M1) of the machining system comprises a tool holder (600) equipped with a machining tool (900), the method comprising the following steps: - positioning (1010) the machine tool (M1) relative to the workpiece (P1) in order to machine the workpiece (P1) using the tool (900); the distance (D1) between the workpiece (P1) and the frame (100) of the machine tool (M1) being equal to a value (D1) referred to as the initial value, the drive shaft (400) having an axial reference position (P4ref) relative to the frame (100) of the machine tool; - performing (1020) a machining operation on the workpiece (P1) by controlling the rotary drive motor (2) to rotate the tool (900) and / or by controlling the feed motor (3) to axially move the tool (900); The axial movement of the tool (900) is controlled according to the axial reference position (P4ref) of the drive shaft; - during machining on the workpiece (P1), determining (1030) a change in the distance (D1') between the workpiece (P1) and the frame (100) of the machine tool, so that the distance (D1) between the workpiece (P1) and the frame (100) of the machine tool (M1) is equal to a new value (D1'); - compensating (1040) the movement of the workpiece (P1) by an axial movement of the drive shaft (400) of the tool holder (600) by a distance called a compensation distance, the compensation distance corresponding to the difference between the new value (D1') and the initial value (D1) to define a new axial reference position (P4ref') of the drive shaft (400), - continuing (1050) the machining operation on said workpiece (P1) according to said new reference position (P4ref') of said axis.

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