Boring bar and non-rotating boring tool, and boring arrangement comprising such a boring bar

Abstract

A boring bar (2) of a non-rotating boring tool, comprising: an elongate body (6) which is configured to be attached to a support structure of a metal cutting machine and is arranged to carry a tool part (4) provided with a cutting element (5); and at least two electrically controlled vibration actuators (16) for active vibration damping of the boring bar (2), each actuator comprising a damping mass (16a) arranged in a movable manner, and each actuator being configured to generate a vibration force parallel to the working axis (17) of the actuator, the working axis of the actuator being perpendicular to the central axis (15) of the damping mass, wherein each actuator is a single-axis actuator having a single working axis, and wherein the actuators are arranged such that their working axes are angularly offset from each other. The actuators (16) are arranged in a longitudinal series in the elongate body (6), wherein the central axis (15) of the damping mass (16a) of each actuator coincides with the longitudinal axis (7) of the elongate body.

Description

TECHNICAL FIELD

[0001] The present invention relates to a boring bar. The present invention also relates to a non-rotating boring tool and a boring arrangement comprising such a boring bar. BACKGROUND ART

[0002] A cantilever boring bar having a cutting element at its free end can be used to perform different types of machining operations on a rotating workpiece of metallic material, such as, for example, internal or external turning. During the machining operation, the cutting element is subjected to cutting forces from the rotating workpiece, including a radial force and a tangential force, the radial force being directed along a line that extends perpendicular to the rotational axis of the workpiece and intersects the rotational axis and the contact point between the cutting element and the workpiece, the tangential force being perpendicular to the radial force and being directed in the tangential direction of the workpiece surface at the contact point between the cutting element and the workpiece. These mutually perpendicular cutting forces will cause vibrations in the boring bar, which in turn may cause noise, impaired workpiece surface finish, tool breakage and other undesirable effects.

[0003] To reduce the vibrations of the boring bar caused by the cutting forces on the cutting element at the outer end of the boring bar during machining of a workpiece, different types of active damping systems have been developed. Such an active damping system may comprise: at least one vibration sensor for sensing the vibrations of the boring bar; and at least one electronically controlled vibration actuator for generating a vibration force in the boring bar, wherein the vibration actuator is controlled by an electronic control unit depending on the measurement signals from one or more vibration sensors so as to introduce in the boring bar an anti-vibration that will interfere with and thereby cancel the vibrations caused by the cutting forces in the boring bar.

[0004] An active damping system of the above type is disclosed in US 5 170 103 A, wherein the vibration actuator is housed in a cavity inside the boring bar.

[0005] An active damping system may comprise one or more vibration actuators that are mounted on a machine tool, outside the ram of the machine tool, as disclosed in EP 3 511112A1, so as to damp the vibrations in the ram. SUMMARY OF THE INVENTION

[0006] It is an object of the present invention to provide a boring bar of the above type having a novel and advantageous design.

[0007] According to the present invention, said object is achieved by a boring bar.

[0008] The boring bar according to the present invention is configured for use in a non-rotating boring tool and comprises:

[0009] - An elongate body configured to be attached to a support structure of a metal cutting machine, the elongate body having a rear end and an opposite front end, the front end being arranged to carry a tool part provided with cutting elements; and

[0010] - At least two electrically controlled vibration actuators for active vibration damping of the boring bar.

[0011] Each of the at least two actuators includes a damping block movably arranged and is configured to generate a vibration force parallel or at least substantially parallel to the working axis of the actuator by movement of the damping block, the working axis of the actuator being perpendicular to the central axis of the damping block, wherein each of the at least two actuators is a single-axis actuator having a single working axis, and wherein the at least two actuators are arranged such that their working axes are angularly offset from each other. Further, the at least two actuators are arranged in a longitudinal series in the elongate body, wherein the central axis of the damping block of each of these actuators coincides or substantially coincides with the longitudinal axis of the elongate body. Thus, the damping blocks of the at least two actuators are arranged in the elongate body centered on the longitudinal axis of the elongate body, which will simplify the calculations used in the control of the actuators, thereby enabling a damping system with good response and the ability to damp vibrations in the boring bar to be achieved in an accurate and rapid manner.

[0012] In addition, by the above arrangement of the at least two actuators, these actuators are located in the elongate body, and the working axes of these actuators are perpendicular to the longitudinal axis of the elongate body and are oriented in mutually different directions. Thus, the actuators in question can be optimized to counteract vibrations in different angular directions with respect to the longitudinal axis of the boring bar, which is beneficial for achieving efficient vibration damping. In this case, a first actuator can be optimized, for example, to counteract vibrations caused by the above-mentioned radial force on the cutting element, and another actuator can be optimized to counteract vibrations caused by the above-mentioned tangential force on the cutting element. In the latter case, it is suitable to use two actuators arranged such that their working axes extend perpendicular to each other, since the radial force is perpendicular to the tangential force.

[0013] In addition to the two or more actuators arranged in the elongate body in the manner defined above, i.e., in addition to the at least two actuators described above, the boring bar may also include one or more additional actuators arranged in any other suitable manner as required.

[0014] According to an embodiment of the present invention, the number of the at least two actuators is n, where n≥2, and the at least two actuators are arranged in the elongate body such that the working axis of each of the n actuators is oriented at an angle of 180° / n relative to another one of the n actuators, wherein the respective working axes of the n actuators are uniformly angularly distributed, and wherein the working axis of each of the n actuators has a separate angular orientation that is different from the angular orientation of the working axes of the other actuators of the n actuators. Thus, if the number of the actuators in question is 2, their working axes are oriented at an angle of 90° to each other, if the number of the actuators is 3, their working axes are oriented at an angle of 60° to each other, and so on. Further, each pair of adjacent actuators is preferably arranged such that their working axes are oriented at an angle of 180° / n relative to each other, which means that the working axis of each actuator arranged in consecutive order after a previous actuator of the n actuators is oriented at an angle of 180° / n to the working axis of the previous actuator.

[0015] According to another embodiment of the present invention, the elongate body comprises:

[0016] - an elongate main portion configured to be attached to a support structure of a metal cutting machine, the main portion having a rear end and an opposite front end,

[0017] - a front portion having a rear end and an opposite front end, the rear end of the front portion facing the front end of the main portion, the front end of the front portion being arranged to carry the tool portion, and

[0018] - at least one damping module arranged between the front end of the main portion and the rear end of the front portion and housing one or more of the at least two actuators.

[0019] The aforementioned front portion of the elongating body is connected to the main portion of the elongating body via the at least one damping module, wherein the at least one damping module forms a length section of the elongating body. Thus, the main portion, the at least one damping module, and the front portion form separate and successively arranged length sections of the elongating body, as seen in the longitudinal direction of the elongating body. Thereby, the vibration actuator can be integrated into the elongating body of the boring bar by first mounting the actuator within the housing of the associated damping module and then fixing the damping module between the main portion and the front portion of the elongating body, which will facilitate the assembly of the boring bar. In this case, the working direction of the actuator relative to the contact point between the cutting element and the workpiece can be adjusted, if required, by adjusting the rotational position of the associated damping module relative to the front portion of the elongating body. Further, by accommodating the actuator within a separate damping module, the damping characteristics can be easily adapted to specific requirements by modifying the damping module without having to change other parts of the boring bar. The number of actuators in the boring bar can vary depending on specific requirements by changing the number of damping modules arranged between the main portion and the front portion of the elongating body. The arrangement of the actuator within a separate damping module arranged between the main portion and the front portion of the elongating body also makes it easy to position the actuator close to the front end of the elongating body, which is an advantageous position for the actuator as it is adjacent to the cutting element generating the vibration of the boring bar. Further, the use of a separate damping module makes this part of the boring bar more easily adaptable to the requirements of the actuator with the aim of maximizing the stroke of the damping block and the actuator.

[0020] However, as an alternative, the elongating body of the boring bar can be devoid of a separate damping module of the aforementioned type, wherein the at least two actuators are jointly accommodated within the same cavity inside the elongating body or separately accommodated within separate cavities inside the elongating body.

[0021] The at least one damping module preferably has the same cross-sectional outer peripheral surface shape as the main portion and / or the front portion. Further, the main portion and / or the front portion and / or the at least one damping module are advantageously cylindrical, preferably circular cylindrical.

[0022] According to an embodiment of the invention, the outer peripheral surface of the main portion and the outer peripheral surface of the at least one damping module are flush or substantially flush with each other. The elongating body of the boring bar can thereby be designed with a smooth outer peripheral surface.

[0023] According to another embodiment of the invention, the at least one damping module is clamped between the main part and the front part by means of tie rods, which preferably extend through a passage in the at least one damping module. Thereby, one or more damping modules can be fixed in a simple and reliable manner between the main part and the front part of the elongate body. Each of the tie rods can have a first end fixed to the main part and a second, opposite end fixed to the front part.

[0024] According to another embodiment of the invention, the elongate body comprises at least two damping modules of the above-described type arranged in series with one another between the front end of the main part and the rear end of the front part, wherein the at least two actuators are arranged in different damping modules of these damping modules. Thereby, the actuators in question can be integrated in a simple manner in the elongate body of the boring bar. As an alternative, the at least two actuators can be accommodated in one and the same damping module. The at least two damping modules are advantageously arranged against one another. However, as an alternative, some intermediate element can be arranged between the at least two damping modules. The front part of the boring bar is preferably arranged such that its rear end abuts against the front end of the foremost one of the at least two damping modules. However, as an alternative, some intermediate element can be arranged between the front part and the foremost damping module. The rearmost one of the at least two damping modules is preferably arranged such that its rear end abuts against the front end of the main part. However, as an alternative, some intermediate element can be arranged between the main part and the rearmost damping module.

[0025] For the purpose of facilitating the manufacture of the elongate body, the at least two damping modules are advantageously of the same design and dimensions.

[0026] Further advantageous features of the boring bar according to the invention will become apparent from the following description.

[0027] The invention also relates to a non-rotating boring tool comprising a boring bar of the above-described type and a tool part provided with a cutting element, wherein the tool part is detachably attached to or integrally formed with the front end of the elongate body.

[0028] According to an embodiment of the invention, the tool part is adjustable in terms of its rotational position relative to the elongate body. Thereby, it will be possible to adjust the angular position of the cutting element relative to the working axis of the at least two actuators in order to optimize the damping characteristics.

[0029] According to another embodiment of the present invention, the cutting element includes a rake face, a flank face, and a cutting edge formed at the intersection between the rake face and the flank face. When observed in a cross-sectional plane perpendicular to the longitudinal axis of the elongate body and intersecting the cutting edge at the radially outermost point, a straight and imaginary reference line L intersects the cutting edge at the radially outermost point and extends at an angle of 6° with respect to the flank face on the outer side of the cutting element in this cross-sectional plane. And when observed in this cross-sectional plane, the working axis of the actuator closest to the front end of the elongate body:

[0030] · forms an angle of 90° ± 10°, preferably 90° ± 5°, more preferably 90° ± 1° with the reference line L, or

[0031] · forms an angle of 0° ± 10°, preferably 0° ± 5°, more preferably 0° ± 1° with the reference line L.

[0032] The clearance angle of the cutting element of the non-rotary boring tool is usually 6° or close to 6°, which means that the above-mentioned tangential force on the cutting element will be basically directed along the reference line L defined above, and the above-mentioned radial force on the cutting element will be basically perpendicular to this reference line L. In order to achieve efficient vibration damping of the boring bar of the non-rotary boring tool, advantageously, the working axis of the actuator closest to the front end of the boring bar is arranged to be substantially parallel to the radial force on the cutting element, so as to allow the actuator to efficiently damp the vibration caused by this radial force, or the working axis of the actuator closest to the front end of the boring bar is arranged to be substantially parallel to the tangential force on the cutting element, so as to allow the actuator to efficiently damp the vibration caused by this tangential force. When the working axis of the actuator closest to the front end of the boring bar is arranged to form an angle of 90° ± 10° with the above-mentioned reference line L, the actuator will thus be concentrated on damping the vibration in the boring bar caused by the radial force on the cutting element. On the contrary, when the working axis of the actuator closest to the front end of the boring bar in the damping module is arranged to form an angle of 0° ± 10° with the above-mentioned reference line L, the actuator will be concentrated on damping the vibration in the boring bar caused by the tangential force on the cutting element.

[0033] According to another embodiment of the present invention, the boring tool includes at least one vibration sensor, and the at least one vibration sensor is mounted to the elongate body or to the tool part at the front end of the elongate body. Thus, the vibration will be detected at a position close to the cutting element, which enables efficient cancellation of the vibration caused by the cutting force acting on the cutting element.

[0034] Further advantageous features of the boring tool according to the present invention will be apparent from the following description.

[0035] The invention further relates to a boring arrangement comprising a boring tool shank of the above type and an electronic control unit configured to control the current to the at least two actuators in order to control the generation of the vibration force in these actuators. The boring arrangement preferably further comprises at least one vibration sensor configured to generate a measurement signal related to the vibration of the boring tool shank and to send the measurement signal to the electronic control unit, wherein the electronic control unit is configured to receive the measurement signal from the at least one vibration sensor and to control the current to the at least two actuators depending on the measurement signal from the at least one vibration sensor in order to control the generation of the vibration force in these actuators depending on these measurement signals.

[0036] Further advantageous features of the boring arrangement according to the invention will become apparent from the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] With reference to the accompanying drawings, a detailed description of an embodiment of the invention is given below by way of example.

[0038] In the drawings:

[0039] Figure 1 is a side view of a non-rotating boring tool according to an embodiment of the invention,

[0040] Figure 2 is according to Figure 1 a longitudinal sectional view along line II-II of

[0041] Figure 3 is Figure 1 an exploded view of the boring tool of

[0042] Figure 4 is from Figure 1 an exploded view of the boring tool in another direction of

[0043] Figure 5 is Figure 1 a perspective view of the front end of the boring tool of

[0044] Figure 6a and Figure 6b is Figure 1 a front view of the boring tool of

[0045] Figure 7a is from Figure 1 a perspective view above the cutting element comprised in the boring tool of

[0046] Figure 7b is from Figure 7a a perspective view below the cutting element of

[0047] Figure 7c is Figure 7a a side view of a cutting element,

[0048] Figure 8a is a perspective view from above of an alternative cutting element,

[0049] Figure 8b is from Figure 8a a perspective view from below of a cutting element,

[0050] Figure 8c is Figure 8a a side view of a cutting element,

[0051] Figure 9 a schematic view of a boring arrangement according to an embodiment of the present invention,

[0052] Figure 10 is a schematic view of an alternative boring arrangement according to an alternative embodiment of the present invention, and

[0053] Figure 11 is a schematic view of another alternative boring arrangement according to another alternative embodiment of the present invention. DETAILED DESCRIPTION

[0054] In Figures 1 to 5 is shown a non-rotating boring tool 1 according to an embodiment of the present invention. The boring tool 1 is adapted to perform different types of machining operations on a rotating workpiece of metallic material, such as for example internal or external turning. The boring tool 1 includes a boring tool shank 2 which will be fixed to a support structure 3 of a metal cutting machine (shown very schematically in Figures 9 to 11 ) so as to project from the support structure 3 in a cantilever manner. The boring tool shank 2 includes an elongate body 6 which is configured to be attached to the support structure 3 of the metal cutting machine. The elongate body 6 has a rear end 6b and an opposite front end 6a. A longitudinal axis 7 of the elongate body extends between the rear end 6b and the front end 6a of the elongate body.

[0055] The boring tool 1 further includes a tool part 4 provided with a cutting element 5, wherein the tool part 4 is carried by the elongate body 6 and is mounted to the elongate body at the front end 6a of the elongate body. As an alternative, the tool part 4 may be integrally formed with the front end 6a of the elongate body, which means that the tool part 4 and the elongate body 6 are combined into a common part.

[0056] The boring bar 2 includes at least two electro-controlled vibration actuators 16 for active vibration damping of the boring bar 2. Each of these actuators 16 includes a damping block 16a arranged movably, and each of these actuators 16 is configured to generate a vibration force parallel or at least substantially parallel to the working axis 17 of the actuator by the movement of its damping block, the working axis 17 of the actuator being perpendicular to the central axis 15 of the damping block 16a. Each of the at least two actuators 16 is a single-axis actuator having a single working axis 17, and these actuators 16 are arranged such that their working axes 17 are angularly offset from each other. Thus, the actuators 16 are arranged at mutually different rotational positions in the elongate body 6.

[0057] The actuator 16 is configured to generate a vibration force to counteract the vibration induced in the boring bar 2 by the cutting force acting on the cutting element 5 during machining of a rotating workpiece. The vibration force generated by the actuator 16 can also be used to intermittently vibrate the cutting element 5 in order to break up larger metal chips cut from the workpiece by the cutting element 5 into fragments.

[0058] The actuators 16 are arranged in series longitudinally in the elongate body 6, i.e., arranged successively in the longitudinal direction of the elongate body, wherein the central axis 15 of the damping block 16a of each of these actuators 16 coincides or at least substantially coincides with the longitudinal axis 7 of the elongate body 6. Thus, the working axis 17 of each of the actuators 16 extends in a cross-sectional plane perpendicular to the longitudinal axis 7 of the elongate body 6.

[0059] In Figures 1 to 5 the embodiment shown, the number of the actuators 16 is 2, but as an alternative, the boring bar 2 can include more than two such actuators 16 arranged in the elongate body 6 such that the working axes 17 of all these actuators 16 are preferably oriented in mutually different directions. The working axes 17 of these actuators 16 are preferably evenly angularly distributed, wherein the working axis 17 of each of these actuators 16 is oriented at an angle of 180° / n with respect to another of these actuators, where n is an integer corresponding to the number of the actuators 16. Thus, when the number of the actuators 16 is 2, these actuators are preferably arranged in the elongate body 6 such that their working axes 17 are oriented at an angle of 90° with respect to each other, i.e., perpendicular to each other, as Figure 1 and Figure 2As shown. When the number of the actuators 16 is 3, these actuators are preferably arranged in the elongate body 6 such that their working axes 17 are oriented at an angle of 60° to each other. When the number of the actuators 16 is 4, these actuators are preferably arranged in the elongate body 6 such that their working axes 17 are oriented at an angle of 45° to each other, and so on. In addition, the actuators 16 in each pair of adjacent actuators are preferably arranged such that their working axes are oriented at an angle of 180° / n with respect to each other.

[0060] In Figures 1 to 5 In the embodiment shown, the elongate body 6 of the boring bar 2 consists of a plurality of separate parts 10, 12, 14 which are connected to each other and together form the elongate body 6, wherein these parts 10, 12, 14 constitute a plurality of separate length segments, i.e., separate segments, of the elongate body 6. Thus, these parts 10, 12, 14 constitute successive segments of the elongate body 6 of the boring bar, as seen in its longitudinal direction. In this case, the elongate body 6 includes an elongate main part 10 configured to be attached to the support structure 3 of the metal cutting machine. The main part 10 has a rear end 10b and an opposite front end 10a. The main part 10 is preferably tubular and will be attached to the support structure 3 at its rear end 10b. In the embodiment shown, the main part 10 is cylindrical and has a circular cross-sectional shape. However, the main part 10 may also have any other suitable cross-sectional shape, such as an oval or a polygonal cross-sectional shape.

[0061] Figures 1 to 5 The elongate body 6 shown further includes a front part 12. The front part 12 has a rear end 12b and an opposite front end 12a, wherein the rear end 12b faces the front end 10a of the main part 10. The front end 12a of the front part is arranged to carry the above-mentioned tool part 4. Thus, the tool part 4 is attached to the front part 12 at the front end 12a of the front part 12 of the boring bar. As an alternative, the tool part 4 may be integrally formed with the front part 12, which means that the tool part 4 and the front part 12 are combined into a common component. In the embodiment shown, the front part 12 is cylindrical and has a circular cross-sectional shape. However, the front part 12 may also have any other suitable cross-sectional shape, such as an oval or a polygonal cross-sectional shape.

[0062] The elongating body 6 may further include at least one damping module 14 disposed between the front end 10a of the main portion 10 and the rear end 12b of the front portion 12, wherein the damping module 14 has a rear end 14b and an opposite front end 14a, the rear end 14b facing the main portion 10 and the front end 14a facing the front portion 12. In the illustrated embodiment, the elongating body 6 includes two such damping modules 14, which are arranged in series with each other between the front end 10a of the main portion 10 and the rear end 12b of the front portion 12. Thus, the two damping modules 14 are arranged in series with each other in the longitudinal direction of the elongating body 6. As an alternative, the elongating body 6 may include more than two damping modules 14 arranged in series with each other in the longitudinal direction of the elongating body, or include a single damping module 14. The front portion 12 is connected to the main portion 10 via the damping module 14.

[0063] In the illustrated embodiment, the damping module 14 is cylindrical and has a circular cross-sectional shape. However, the damping module 14 may also have any other suitable cross-sectional shape, such as an elliptical or polygonal cross-sectional shape.

[0064] Each of the damping modules 14 is provided with at least one of the above-described actuators 16, wherein the actuator 16 is disposed in the housing 14c of the associated damping module, and the damping block 16a of the actuator 16 is movable relative to the housing 14c. In the illustrated embodiment, the damping block 16a is movable relative to the housing 14c of the damping module 14 against the action of a return spring 16b disposed on the opposite side of the damping block 16a. The actuator 16 may be of the electromagnetic type, wherein the vibration force is electromagnetically generated. However, any other suitable type of vibration actuator may also be used.

[0065] In the illustrated embodiment, each damping module 14 is provided with a single actuator 16. However, as an alternative, an individual damping module 14 may be provided with two or more actuators 16.

[0066] In the illustrated embodiment, the damping modules 14 are in direct abutment with each other, wherein the rear end 14b of the foremost damping module abuts against the front end 14a of another damping module (i.e., the rearmost damping module). As Figures 1 to 5 shown, the front portion 12 may be arranged such that its rear end 12b abuts directly against the front end 14a of the foremost damping module, and the rearmost damping module may be arranged such that its rear end 14b abuts directly against the front end 10a of the main portion 10.

[0067] The outer peripheral surface 18 of the main portion 10 and the outer peripheral surface 19 of each damping module 14 are advantageously flush or substantially flush with each other, as Figure 1 、 Figure 2 and Figure 5As shown. In addition, the outer peripheral surface 20 of the front portion 12 is flush or substantially flush with the outer peripheral surface 19 of the foremost damping module 14.

[0068] For ease of maintenance and repair of the boring bar 2, the main portion 10, the damping module 14, and the front portion 12 are preferably detachably mounted to one another. In the illustrated embodiment, the damping module 14 is clamped between the main portion 10 and the front portion 12 by tie rods 22. Each tie rod 22 has a first end 22a and an opposite second end 22b, the first end 22a being fixed to the main portion 10 and the second end 22b being fixed to the front portion 12. In addition, each tie rod 22 extends through aligned channels 23 in the damping module 14. As an alternative, the different portions 10, 12, 14 of the elongate body 6 may be mounted to one another in any other suitable manner.

[0069] In the illustrated embodiment, the actuator 16 in each damping module 14 is accessible through two openings on opposite sides of the damping module, where each opening is covered by a removably mounted cover plate 24 that forms part of the outer peripheral surface 19 of the damping module and is fixed in the associated opening by fastening elements 25 in the form of screws. The channels 23 for some of the above-mentioned tie rods 22 may be provided in the cover plate 24.

[0070] In the illustrated embodiment, cooling fluid is supplied to the tool portion 4 through a first feed tube 26 and at least one second feed tube 27, the first feed tube 26 extending axially through the main portion 10 of the elongate body 6, and the at least one second feed tube 27 extending between the main portion 10 and the front portion 12 of the elongate body parallel to the tie rods 22. In the illustrated example, the boring bar 2 is provided with two such second feed tubes 27. The first feed tube 26 is fixed to the main portion 10 of the elongate body by a first end piece 28a and a second end piece 28b, the first end piece 28a being fixed to the main portion 10 at the front end 10a of the main portion 10 and the second end piece 28b being fixed to the main portion 10 at the rear end 10b of the main portion 10. Each of the second feed tubes 27 is connected to the first feed tube 26 via an internal passage in the first end piece 28a. In addition, each of the second feed tubes 27 may be arranged to extend through aligned channels 29 in the damping module 14.

[0071] In order to enable adjustment of the working axis 17 of the actuator 16 relative to the cutting element 5, the front part 12 of the elongate body 6 can be adjusted in terms of its rotational position relative to the damping module 14, which means that the front part 12 can be attached to the foremost damping module 14 in different selectable rotational positions relative to the damping module. As an alternative or in combination with this rotational adjustability of the front part 12 relative to the damping module 14, the tool part 4 provided with the cutting element 5 can be adjusted in terms of its rotational position relative to the front part 12 of the elongate body, which means that the tool part 4 can be attached to the front part 12 in different selectable rotational positions relative to the front part. The damping module 14 can also be arranged such that its actuator 16 can be adjusted in terms of its rotational position relative to the housing of the damping module. When the number of damping modules 14 is 2 or greater, the damping modules can be arranged such that their respective rotational positions can be adjusted relative to each other.

[0072] The cutting element 5 fixed to the tool part 4 can be a positive cutting element, as Figures 7a to 7c shown in, or a negative cutting element, as Figure 8a shown in FIGS. 8a to 8c. The cutting element 5 includes a front cutting face 30 on the upper side, a bottom side 31, and a peripheral flank face 32, wherein the bottom side 31 extends parallel to or substantially parallel to the front cutting face 30, and the peripheral flank face 32 extends between the front cutting face 30 and the bottom side 31. A cutting edge 33 is formed at the intersection between the front cutting face 30 and the flank face 32. In the illustrated example, the cutting edge 33 extends along the periphery of the front cutting face 30 around the entire front cutting face 30. In the case of the positive cutting element 5, the flank face 32 extends at an acute angle α relative to the front cutting face 30, as Figure 7c shown in. In the case of the negative cutting element 5, the flank face 32 extends at a right angle relative to the front cutting face 30, as shown in FIG. 8c.

[0073] A hole 34 extends through the cutting element 5 between the front cutting face 30 and the bottom side 31. The cutting element 5 is configured to be releasably mounted to the tool part 4, wherein the bottom side 31 of the cutting element 5 rests on a support surface 35 provided in a tool seat for the cutting element in the tool part 4 (see Figure 6a ). The cutting element 5 is fixed to the tool seat in the tool part 4 by a fastening element 36 in the form of a screw (see Figure 5 ), which screw extends through the hole 34 in the cutting element 5 and engages in a threaded hole in the support surface 35 in the tool seat.

[0074] In the illustrated example, the cutting element 5 includes two cutting corners 37 opposite to each other and located on opposite sides of the cutting element. The cutting element 5 is to be fixed to the tool part 4, with one cutting corner 37 facing outward away from the longitudinal axis 7 of the boring bar 2, and the cutting element 5 is intended to contact the rotating workpiece via this outward-facing cutting corner 37. During machining of the rotating workpiece, the boring tool 1 is generally positioned relative to the workpiece such that the above-mentioned tangential force F on the cutting element 5 t will be directed at an angle θ of approximately 6° relative to the flank face 32, as Figure 7c shown in

[0075] and Figure 8c. Figure 6a and Figure 6b A straight and imaginary reference line L (see Figures 7a to 7c is defined in a cross-sectional plane that is perpendicular to the longitudinal axis 7 of the elongate body 6 and intersects the cutting edge 33 at the radially outermost point 39, where the reference line L intersects the cutting edge 33 at the radially outermost point 39 and, in this cross-sectional plane, extends at an angle β of 6° relative to the flank face 32 on the outside of the cutting element 5, i.e., extends at this angle β which is measured on the outside of the cutting element 5. Thus, when Figure 6a and Figure 6b the positive cutting element 5 of the type with a 6° clearance angle shown in

[0076] is fixed to the tool part 4, the reference line L can extend perpendicular to the rake face 30 of the cutting element, as Figure 6a shown in r and r .

[0077] According to an advantageous alternative, the actuator 16 closest to the front end 6a of the elongate body 6 is advantageously arranged in a rotational position in the elongate body 6 such that its working axis 17 (when viewed in the above-mentioned cross-sectional plane) forms an angle of 90° ± 10° with the said reference line L (as Figure 6bas shown in, preferably at an angle of 0° ± 5°, more preferably at an angle of 0° ± 1°. In this case, the working axis 17 of the actuator is substantially parallel to the tangential force F on the cutting element 5 t arranged parallelly. By such an arrangement of the actuator 16 closest to the front end 6a of the elongate body, the actuator will be optimized to counteract the vibration caused by the tangential force F on the cutting element 5 t induced.

[0078] In Figures 9 to 11 a different embodiment of a boring arrangement 40 including a boring bar 2 of the above type is very schematically shown. The boring arrangement 40 further includes an electronic control unit 41 configured to control the current supply to the actuators 16 in the elongate body 6 so as to control the generation of the vibration force in these actuators. The current is supplied from a power source to the actuators 16, and the power source can be an external power source 42, as Figure 9 shown in, or a power supply unit 42' which is mounted to the elongate body 6, as Figure 11 shown in, or is mounted to the support structure 3 or any other part of the metal cutting machine, as Figure 10 shown in. The power supply unit 42' includes at least one energy storage member, for example in the form of a battery, for storing electrical energy. The electronic control unit 41 can be mounted to the front part 12 of the elongate body 6, as Figure 10 and Figure 11 shown in, or is mounted to any other part of the elongate body. As a further alternative, the electronic control unit 41 can be mounted to the support structure 3 or any other part of the metal cutting machine, as Figure 9 shown in.

[0079] The boring arrangement 40 further includes at least one vibration sensor 43, for example in the form of an accelerometer, which is configured to generate a measurement signal related to the vibration of the boring bar 2 and send the measurement signal to the electronic control unit 41 via a wireless connection or a cable connection. The at least one vibration sensor 43 is preferably mounted to the front part 12 of the elongate body 6 or is mounted to the tool part 4, but as an alternative, it can be mounted to any other suitable part of the elongate body 6.

[0080] The electronic control unit 41 is configured to receive the measurement signals from the above at least one vibration sensor 43 and, depending on these measurement signals, control the current supply to the actuators 16 so as to control the generation of the vibration force in each actuator 16 depending on these measurement signals, and thereby counteract the vibration induced in the boring bar 2 by the cutting forces F r 、F t during machining of the workpiece.

[0081] The present invention is of course not limited in any way to the embodiments described above. On the contrary, many possibilities for modifying the present invention will be obvious to those skilled in the art without departing from the basic idea of the present invention defined in the appended claims. In some applications, twice the energy is required for damping in the direction of the radial cutting force than in the tangential direction. Thus, the boring bar may include three damping actuators, wherein the respective working axes of two of the three damping actuators are oriented in the same manner, preferably perpendicular to the reference line L, i.e., oriented in the direction of the radial cutting force, while the working axis of the third actuator may be oriented parallel to the reference line L and perpendicular to the working axes of the other two actuators.

Claims

1. A boring bar (2) for a non-rotary boring tool, said boring bar (2) comprising: - an elongate body (6) configured to be attached to a support structure of a metal cutting machine, said elongate body (6) having a rear end (6b) and an opposite front end (6a), said front end (6a) being arranged to carry a tool part (4) provided with a cutting element (5); and - at least two electrically controlled vibration actuators (16) for active vibration damping of the boring bar (2), each of said at least two electrically controlled vibration actuators (16) comprising a damping mass (16a) arranged in a movable manner, and each of said at least two electrically controlled vibration actuators (16) being configured to generate a vibration force parallel or at least substantially parallel to the working axis (17) of the electrically controlled vibration actuator by movement of the damping mass, the working axis of the electrically controlled vibration actuator being perpendicular to the central axis (15) of the damping mass (16a), wherein each of said at least two electrically controlled vibration actuators (16) is a single-axis actuator having a single working axis (17), and wherein said at least two electrically controlled vibration actuators (16) are arranged such that their working axes (17) are angularly offset from each other, wherein said at least two electrically controlled vibration actuators (16) are arranged in a longitudinal series in said elongate body (6), wherein the central axis (15) of the damping mass (16a) of each of these electrically controlled vibration actuators (16) coincides or substantially coincides with the longitudinal axis (7) of the elongate body (6), characterized in that said elongate body (6) comprises: · an elongate main part (10) configured to be attached to a support structure of a metal cutting machine, said main part (10) having a rear end (10b) and an opposite front end (10a), · a front part (12) having a rear end (12b) and an opposite front end (12a), said rear end (12b) facing said front end (10a) of said main part (10), said front end (12a) of said front part (12) being arranged to carry said tool part (4), and · at least one damping module (14) arranged between said front end (10a) of said main part (10) and said rear end (12b) of said front part (12) and accommodating one or more of said at least two electrically controlled vibration actuators (16); and - said front part (12) of said elongate body (6) is connected to said main part of said elongate body via said at least one damping module (14), wherein said at least one damping module (14) forms a length section of said elongate body (6).

2. The boring bar according to claim 1, characterized in that The number of the at least two electro-controlled vibration actuators (16) is n, i.e., n electro-controlled vibration actuators, where n≥2, and the at least two electro-controlled vibration actuators (16) are arranged in the elongate body (6) such that the working axis (17) of each of the n electro-controlled vibration actuators is oriented at an angle of 180° / n relative to another one of the n electro-controlled vibration actuators, wherein the n electro-controlled vibration actuators have corresponding working axes (17) with a uniform angular distribution, and wherein the working axis (17) of each of the n electro-controlled vibration actuators (16) has a separate angular orientation which is different from the angular orientation of the working axes of the other electro-controlled vibration actuators among the n electro-controlled vibration actuators.

3. The boring bar according to claim 2, characterized in that each pair of adjacent electro-controlled vibration actuators (16) is arranged such that their working axes (17) are oriented at an angle of 180° / n relative to each other.

4. The boring bar according to claim 1, characterized in that the at least one damping module (14) has the same cross-sectional outer peripheral surface shape as the main part (10) and / or the front part (12).

5. The boring bar according to any one of claims 1-4, characterized in that the main part (10) and / or the front part (12) and / or the at least one damping module (14) is cylindrical.

6. The boring bar according to any one of claims 1 to 4, characterized in that the outer peripheral surface (18) of the main part (10) and the outer peripheral surface (19) of the at least one damping module (14) are flush or substantially flush with each other.

7. The boring bar according to any one of claims 1 to 4, characterized in that the at least one damping module (14) is clamped between the main part (10) and the front part (12) by a tie rod (22).

8. The boring bar according to any one of claims 1 to 4, characterized in that the front part (12) of the elongate body can be adjusted in terms of its rotational position relative to the at least one damping module (14).

9. The boring bar according to any one of claims 1 to 4, characterized in that the at least two electro-controlled vibration actuators (16) are accommodated in the same damping module (14).

10. The boring bar according to any one of claims 1 to 4, characterized in that the elongate body (6) includes at least two such damping modules (14) arranged in series with each other between the front end (10a) of the main part (10) and the rear end (12b) of the front part (12), wherein the at least two electro-controlled vibration actuators (16) are arranged in different damping modules among these damping modules (14).

11. The boring bar according to claim 5, characterized in that The main part (10) and / or the front part (12) and / or the at least one damping module (14) are cylindrical.

12. The boring bar according to claim 7, characterized in that the drawbar (22) extends through a passage (23) in the at least one damping module (14).

13. A non-rotating boring tool, characterized in that the non-rotating boring tool comprises: - a boring bar (2) according to any one of claims 1 to 12; and - a tool part (4) provided with a cutting element (5), wherein the tool part (4) is detachably attached to the front end (6a) of the elongate body or is integrally formed with the front end.

14. The non-rotating boring tool according to claim 13, characterized in that the tool part (4) is adjustable in terms of its rotational position relative to the elongate body (6).

15. The non-rotating boring tool according to claim 13 or 14, characterized in that the cutting element (5) comprises a rake face (30), a flank face (32) and a cutting edge (33), the cutting edge (33) being formed at the intersection between the rake face and the flank face, wherein, when observed in a cross-sectional plane perpendicular to the longitudinal axis (7) of the elongate body (6) and intersecting the cutting edge (33) at the radially outermost point (39), a straight and imaginary reference line L intersects the cutting edge (33) at the radially outermost point (39), and in the cross-sectional plane, extends at an angle (β) of 6° relative to the flank face (32) on the outside of the cutting element (5), and wherein, when observed in the cross-sectional plane, the working axis (17) of the electro-controlled vibration actuator (16) closest to the front end (6a) of the elongate body: · forms an angle of 90° ± 10° with the reference line L, or · forms an angle of 0° ± 10° with the reference line L.

16. The non-rotating boring tool according to any one of claims 13 to 14, characterized in that the boring tool (1) comprises at least one vibration sensor (43), the at least one vibration sensor (43) being mounted to the elongate body (6) or to the tool part (4) at the front end (6a) of the elongate body.

17. The non-rotating boring tool according to claim 15, characterized in that when observed in the cross-sectional plane, the working axis (17) of the electro-controlled vibration actuator (16) closest to the front end (6a) of the elongate body: · forms an angle of 90° ± 5° with the reference line L, or · forms an angle of 0° ± 5° with the reference line L.

18. The non-rotating boring tool according to claim 15, characterized in that when observed in the cross-sectional plane, the working axis (17) of the electro-controlled vibration actuator (16) closest to the front end (6a) of the elongate body: · forms an angle of 90° ± 1° with the reference line L, or ·Form an angle of 0° ± 1° with the reference line L.

19. A boring arrangement, characterized in that the boring arrangement comprises: - a boring tool shank (2) according to any one of claims 1 to 12; and - an electronic control unit (41), the electronic control unit (41) being configured to control the current to the at least two electrically controlled vibration actuators (16) so as to control the generation of the vibration force in these actuators.

20. The boring arrangement according to claim 19, characterized in that: - the boring arrangement (40) comprises at least one vibration sensor (43), the at least one vibration sensor (43) being configured to generate a measurement signal related to the vibration of the boring tool shank (2) and to send the measurement signal to the electronic control unit (41); and, - the electronic control unit (41) is configured to receive the measurement signal from the at least one vibration sensor (43), wherein the electronic control unit (41) is configured to control the current to the at least two electrically controlled vibration actuators (16) depending on the measurement signal from the at least one vibration sensor (43) so as to control the generation of the vibration force in these electrically controlled vibration actuators (16) depending on these measurement signals.

Images