A deep boring tool system with a built-in active dynamic absorber, for controlling unwanted machine chatter

Abstract

An electromagnetic actuator assembly, integrated within a boring tool, for controlling unwanted machining vibration, comprising an outer tubular oscillating mass made of ferromagnetic material, through which the magnetic flux can pass; an inner stator that comprises an electromagnet assembly, located at the center of the tubular oscillating mass, for applying a controllable magnetic field to the oscillating mass; one or more damping elements, each having one or more springs and / or a damping material with predetermined stiffness and damping properties (such as a polymer or oil); a controller for providing a desired current to the electromagnets of the electromagnet assembly to obtain the controllable magnetic field; a holder for allowing the rotation of the electromagnet assembly to a desired angle, for stimulating the oscillating mass to apply a damping force, based on a combination of the magnetic field and stiffness and damping properties, which is aligned with the direction of the unwanted vibration.

Description

[0001] - 1 -

[0002] A DEEP BORING TOOL SYSTEM WITH A BUILT-IN ACTIVE DYNAMIC ABSORBER, FOR CONTROLLING UNWANTED MACHINE CHATTER

[0003] Field of the Invention

[0004] The present invention relates to the field of metal cutting tools. More particularly, the invention relates to a deep boring tool system with a built-in dynamic absorber that combines passive and active approaches for controlling unwanted machine chatter and disconnecting continuous chips formed during machining processes.

[0005] Background of the Invention

[0006] Vibrations in machining processes of metal cutting are undesirable as they adversely affect product quality, increase component wear, and create harmful background noise. As a result, the production yield is limited. Avoiding these vibrations imposes a limitation on the Length-to-Diameter (L / D) ratio (between the length L and the diameter D) of the tool, which currently constitutes a significant technological barrier and a direct hindrance to market demands. The Length-to-Diameter ratio refers to the relationship between the length of a cutting tool or boring bar and its diameter, and is a critical factor in determining the stability, rigidity, and performance of the machining operation, especially in processes like boring and drilling. A high L / D ratio can lead to increased vibrations and chatter, while a lower L / D ratio generally results in a more stable and predictable machining process.

[0007] Vibrations can be classified into three categories: free vibrations, forced vibrations, and self-excited vibrations. The type of vibrations with a dominant negative impact on machining processes are self-excited vibrations, known as chatter (unwanted vibrations that happen during the cutting process), along with forced vibrations (that are caused by external, periodic forces acting on the machine tool, like those from unbalanced rotating parts or nearby machinery. These vibrations occur at the same frequency as the excitation force and can negatively impact surface finish and - 2 - dimensional accuracy). The chatter phenomenon occurs when the cutting tool interacts with the workpiece, while generating mechanical waves. This often results from the regenerative effect, where vibrations from previous passes influence the current pass (a pass refers to a single, individual movement of the cutting tool across the workpiece to remove material, which is repeated multiple times to achieve the desired shape and surface finish). The cutting force depends on the vibrations of both the tool and the workpiece from present and past cycles, leading to unstable conditions.

[0008] Avoiding chatter requires system modifications, such as operating with conservative machining parameters (that negatively impact production yield), using shorter turning tools, adding auxiliary devices to the machine, or employing other advanced technologies. Forced vibrations, which also have adverse effects, typically accompany chatter vibrations. These are primarily triggered by workpiece imbalance, misalignment of components, and chip detachment.

[0009] Existing solutions for reducing unwanted vibrations in machining can be categorized into five approaches. The first and second approaches are already implemented in off-the-shelf products. The first approach involves system changes, including properly selecting machining parameters, turning tools, cutting machines, clamping devices, and cooling systems. The second approach, known as passive vibration control, employs components capable of altering resonant frequencies or absorbing energy without external energy consumption, as shown in Fig. la. The third approach is active vibration control, which uses an external energy source to reduce vibrations. This method relies on vibration measurement, a control algorithm, and an actuator that converts electrical control signals into mechanical energy, as shown in Fig. lb. Unlike the passive approach, this approach can address uncertainties and external disturbances, thereby providing operational flexibility and significantly improving quality and production yields. The fourth approach, semi-active vibration control, uses an external energy source with low power consumption to control the dynamic properties of passive components, as illustrated in Fig. lc. The fifth - 3 - approach is hybrid vibration control, defined as a combination of multiple approaches to achieve optimal efficiency, performance, and minimal external energy consumption.

[0010] The hybrid approach, which combines passive and active damping techniques, holds significant potential. Leveraging assets and understanding the mechanical and physical characteristics of machining processes can lead to developing a minimally sized device tailored to market needs and geometric constraints. A significant geometric constraint in design is a small internal volume confined by a maximum outer diameter for deep internal turning and a minimum internal diameter for allowing coolant flow through a channel along the tool to the turning zone. This approach can enhance turning performance and outputs, increase the Length-to- Diameter (L / D) ratio of the turning tool, and reduce wear, rejects, and background noise. Additionally, by using sensors, a hybrid system can provide real-time health monitoring and recommendations to the workshop.

[0011] In machining, forces are applied to the workpiece to remove material, resulting in reactive forces on the cutting tool. When the workpiece rotates during material removal, the tool does not move in a perfectly circular path, leading to vibrations that affect surface quality and accuracy. Under certain conditions influenced by various factors, such as machining parameters (cutting speed, feed rate, and depth of cut), material type, and the geometric shape of the tool, increased vibrations known as chatter develop. This phenomenon commonly occurs with long tools, where the Length-to-Diameter (L / D) ratio of the boring bar exceeds five. Long deep boring bars tend to be less rigid with lower natural frequencies, making the cutting force more likely to induce vibrations that degrade surface quality and damage the cutting tool.

[0012] The magnitude and direction of the cutting force vary during and between processes. Introducing external forces in the opposite phase to the cutting force can optimally reduce vibrations. Since the direction varies, numerous prior art studies present two different approaches: the first approach introduces forces in two - 4 - primary directions to balance the cutting force, while the second approach introduces a unidirectional force either radially or tangentially to partially cancel out the vibrations. The unidirectional approach addresses the geometric constraint challenge.

[0013] Deep boring tools have been developed using a passive device implanted in the boring bar's internal cavity, based on the principle of a Tuned Mass Damper (TMD - a device that reduces mechanical vibrations in structures by adding a mass, spring, and damper system to the structure, tuned to resonate at the same frequency as the structure's vibration. This out-of-phase resonance dissipates energy and reduces the overall structural vibration). This approach employs a mass-spring-damper system (a mechanical model used to study dynamics and vibrations in engineering and physics. It consists of mass a spring and a damper that dissipates energy, typically through friction or resistance, and provides a force that opposes the velocity of the mass) tuned to the boring bar's natural frequency, generating a counter-phase force to the tool's tip vibrations, thereby expanding the Stability Lobe Diagram (SLD - in which the stable and unstable areas are separated by the graph of a critical cutting parameter plotted against the spindle speed. Stability lobe diagrams can be used to optimize machining processes in terms of maximizing material removal rate under stable cutting conditions) and improving performance. The drawback of such systems is that the tool must be clamped at a precise location matching the tool length, thereby limiting operational flexibility. Moreover, this solution is unsuitable for turning components with resonant frequencies close to those of the tool, meaning it is only applicable to high-stiffness materials. Additionally, TMD-based technology requires a geometric volume that is not feasible for small-diameter deep boring tools.

[0014] Recent developments in active control using piezoelectric actuators and electromagnetic actuators have been explored.

[0015] Another problem that appears during machining is the generation of chips (small fragments or pieces or fragments of material that are produced when a cutting tool - 5 - removes material from a workpiece during machining or metal cutting processes.) which are curled when material is removed from the workpiece, resulting in additional unwanted vibrations.

[0016] Continuous chips arise during the machining of ductile materials at high speeds and minimal friction between the tool and the workpiece, resulting from the continuous plastic deformation induced by the tool. These chips maintain a consistent thickness throughout their length and often yield a favorable surface finish. However, they can be challenging to handle and dispose of due to their continuous form, necessitating the use of chip breakers. This problem mainly occurs when the workpiece material is relatively soft, such as aluminum, Kovar (is a nickel-iron-cobalt alloy with controlled thermal expansion, to match the expansion rates of certain glasses and ceramics, preventing stress and cracking during temperature changes) and Titanium. Therefore, chip breaking is vital to avoid the generation of long, tangled chips that can disrupt the machining process, damage the workpiece or tool, and complicate the chip disposal.

[0017] It is therefore an object of the present invention to provide a deep boring tool system which is compact and is capable of significantly increasing productivity.

[0018] It is another object of the present invention to provide a deep boring tool system which is capable of improving the Length -to-diameter (L / D) ratio of cutting tools, and enhancing product quality.

[0019] It is a further object of the present invention to provide a deep boring tool system which is capable of reducing wear and background noise.

[0020] It is still another object of the present invention to provide a deep boring tool system that has self-centering alignment with manual or automated capabilities relative to the cutting force. - 6 -

[0021] It is yet another object of the present invention to provide a deep boring tool system capable of facilitating high-pressure coolant flow to the cutting tool, with the possibility of using the coolant flow for minimizing the size of the absorber.

[0022] It is a further object of the present invention to provide a deep boring tool system which can be assembled on a standard boring bar or integrated within an existing cutting tool.

[0023] It is a further object of the present invention to provide a deep boring tool system which has chip breaking capability.

[0024] Other objects and advantages of the invention will become apparent as the description proceeds.

[0025] Summary of the Invention

[0026] An electromagnetic actuator assembly, integrated within a boring tool, for controlling unwanted machining vibration, comprising: a) an outer tubular oscillating mass made of ferromagnetic material, through which the magnetic flux can pass; b) an inner stator that comprises an electromagnet assembly, located at the center of the tubular oscillating mass, for applying a controllable magnetic field to the oscillating mass; c) one or more damping elements, each having one or more springs and / or a damping material with predetermined stiffness and damping properties (such as a polymer or oil); d) a controller for providing a desired current to the electromagnets of the electromagnet assembly to obtain the controllable magnetic field; and e) a holder for allowing the rotation of the electromagnet assembly to a desired angle, for stimulating the oscillating mass to apply a damping force, based on - 7 - a combination of the magnetic field and stiffness and damping properties, which is aligned with the direction of the unwanted vibration.

[0027] The damping force may be adjusted manually, or by a physical characteristic force. The actuator assembly applies force in one direction, which is manually or automatically adjusted to be aligned with the chatter cutting force.

[0028] The optimal force direction may be achieved through self-centering, manual adjustment, or using an actuator or any combination thereof.

[0029] The damping force may be precisely opposite to the direction of the chatter-induced force.

[0030] The stator may be a two-axis stator being controlled in both axes by two bipolar current controllers, to thereby obtain an equal force in any required direction.

[0031] The stator may be located in the center, and the oscillating mass operates peripherally.

[0032] The angle of damping force application may be changed through rotational movement around its central axis.

[0033] The stator may further comprise a fluid passage formed in the center of the stator for allowing a coolant fluid to flow towards the cutting area.

[0034] The controller may control the operation, based on robust adaptive dynamic programming utilizing reinforcement learning, small gain theorem, and gain scheduling method.

[0035] The tubular oscillating mass may be shaped as a cylinder.

[0036] The electromagnetic actuator assembly may further comprise permanent magnets, symmetrically embedded within the stator, such that the stiffness and damping - 8 - properties are determined by the current flowing through the electromagnet assembly and the magnetic field applied by the permanent magnets.

[0037] A deep boring tool system, comprising: a) an electromagnetic actuator assembly; b) a deep boring bar, into which the actuator assembly is integrated; c) a cutting tool head connected to the deep boring bar; d) a tool holder, mounted on a lathe; e) a vibration sensor; and f) a control system, connected to the hybrid actuator module via wiring, for providing power supply to the actuator assembly and reading data from the vibration sensor.

[0038] The vibration sensor may be an accelerometer for measuring vibrations and the overall force direction developed from the vibrations.

[0039] The controller may be adapted to disconnect continuous chips formed in the workpiece by generating radial vibrations being perpendicular to the workpiece surface.

[0040] Chip breaking may be caused by intermittent chip thickness variations that are created by adjusting the timing between radial oscillations of the hybrid actuator module and the workpiece rotation, or by adjusting the relative timing or angular displacement between the oscillation and the tool's feed motion in a turning process.

[0041] The controller may also be adapted to disconnect continuous chips formed in the workpiece by interrupting continuous chip formation using a high-frequency wave that generates high-frequency vibrations to create intermittent cutting action. - 9 -

[0042] Brief Description of the Drawings

[0043] The above and other characteristics and advantages of the invention will be better understood through the following illustrative and non-limitative detailed description of preferred embodiments thereof, with reference to the appended drawings, wherein:

[0044] Fig. la (prior art) shows a passive approach;

[0045] Fig. lb (prior art) shows an active approach;

[0046] Fig. lc (prior art) shows a semi-active approach;

[0047] Fig. 2 shows a deep boring tool system, which combines passive and active approaches for controlling unwanted machine chatter, according to an embodiment of the invention;

[0048] Fig. 3 is an exploded view of the hybrid actuator module, according to an embodiment of the invention;

[0049] Fig. 4 shows one example to connecting the integrated hybrid actuator to a standard cutting tool using thread connector.

[0050] Fig. 5 illustrates a possible location of an accelerometer;

[0051] Fig. 6 illustrates the elements of the hybrid actuator module, according to an embodiment of the invention;

[0052] Fig. 7 shows the change of the stator angle and the force direction angle, with the variation of the chatter force direction;

[0053] Fig. 8 shows a two-axis stator with a rotating and oscillating outer mass, according to an embodiment of the invention;

[0054] Fig. 9 illustrates the structure of a hybrid rotating stator, made of a ferromagnetic material with a bore 91 along its central axis, for allowing the passage of cooling fluid and serving as the rotation axis;

[0055] Figs. lOa-lOc show the magnetic flux lines and their intensity, obtained without electrical current, with the application of positive current; - 10 -

[0056] Figs. lla-llb illustrate an active force at a desired angle, for generating radial vibrations which are perpendicular to the workpiece surface;

[0057] Fig. 12 shows the process of chip braking using the phase shift method; and Fig. 13 shows the process of chip braking using the high-frequency vibration method.

[0058] Detailed Description of the Invention

[0059] The present invention provides a deep boring tool system with a built-in dynamic absorber that uses a hybrid vibration control device combining passive and active approaches for controlling unwanted machine chatter, forced vibration or any other type of unwanted vibration.

[0060] The proposed deep boring tool system is used for machining processes that involve material removal, such as turning (a machining process where a lathe is used to rotate the metal while a cutting tool moves in a linear motion to remove metal along the diameter, to create a cylindrical shape) or milling (the process of machining using rotary cutters to remove material by advancing a cutter into a workpiece).

[0061] The proposed novel deep boring tool system uses the unidirectional approach combined with a hybrid actuator module that allows the damping force to rotate until it aligns with the cutting force (self-centering capability). This new concept addresses the geometric constraints while optimally minimizing vibrations resulting from the cutting force. This active deep boring tool system is based on a unique hybrid electromagnetic-permanent magnetic-mechanical TMD actuator module with a unique structure and allows the construction of a miniature hybrid unidirectional actuator with self-centering capability relative to the cutting force. The unidirectional hybrid actuator module is adaptable to a wide range of market needs, with very small diameters and a greater L / D ratio than the current standard for L / D ratio, without compromising market demands and constraints. The unidirectional hybrid actuator module also uses an externally tuned mass to the stator as part of - li the optimization process, while facilitates of high-pressure coolant flow, thereby leveraging the coolant for thermal optimization of the miniature hybrid actuator module. The modular design of the deep boring tool system allows it to be assembled on a standard boring bar, or be integrated within an existing tool.

[0062] Fig. 2 shows a deep boring tool system 100, which combines passive and active approaches for controlling unwanted machine chatter, according to an embodiment of the invention. The deep boring tool system 100 comprises a deep boring bar 20 into which a hybrid actuator module (assembly) is integrated, a hybrid actuator module 30, a cutting tool head 40 connected to the deep boring bar 20, a tool holder 10 that is mounted on a lathe / CNC / turning machine (not shown) and one or more vibration sensors. The hybrid actuator module 30 is mounted as an add-on module on the standard boring bar and it can be embedded within a dedicated boring bar 20 according to predetermined requirements. A control system 60 is connected to the hybrid actuator module 30 wirelessly or via wiring 50, for providing control power supply to the hybrid actuator module 30 and reading data from the vibration sensors.

[0063] Fig. 3 is an exploded view of the hybrid actuator module 30, according to an embodiment of the invention. The modular design of the hybrid actuator module 30 is suitable for connection to a standard boring bar. The hybrid actuator module 30 comprises an oscillating mass 16, which is specially shaped as a cylinder (made of ferromagnetic material), a standard serrated adapter 43, commonly used by several manufacturers of boring bars, and a central tube 73 for allowing coolant fluid transfer. A modular connector, such as a threaded connector 401 (shown in Fig. 4), or a simple bolt connection, can also be used. The central tube 73 runs along the central axis 33 of the hybrid actuator module 30, thereby allowing coolant fluid to be transferred to the serrated cover 23, which connects to the boring heads and the insert holder. There is a coolant passage opening that continues into a coolant channel, for directing the coolant fluid towards the cutting area to cool the cutting - 12 - insert (a removable cutting tip), while preventing vibrations and wear on the insert. Bolts 53 are used to attach the hybrid actuator module 30 to a standard boring bar.

[0064] The hybrid actuator module 30 includes a tri-axial accelerometer 63 (serving as a vibration sensor) for measuring vibrations and the overall force direction developed from the vibrations due to all the previously mentioned factors, as shown in Fig. 5, which illustrates a possible location of the accelerometer.

[0065] Fig. 6 illustrates the elements of the hybrid actuator module 30, according to an embodiment of the invention. The hybrid actuator module 30 has a unique structure which is implemented in an inverted manner with respect to a conventional design. Here, the inner stator (the fixed part) is located at the center of the hybrid actuator module 30 and comprises an electromagnet assembly, located at the center of the oscillating mass, for applying a controllable magnetic field to the oscillating mass. This arrangement allows the coolant fluid to pass through a pipe that also serves as the rotation axis for the entire hybrid actuator module 30. The rotation capability of the hybrid actuator module 30 allows changing the direction of the damping force to be precisely opposite to the direction of the chatter-induced force. This configuration achieves maximum directional force density, which allows even smalldiameter tools to receive high damping energy, along with the precise ability to adjust the damping force angle towards the chatter-induced force (the vibration direction).

[0066] The hybrid actuator module 30 comprises an oscillating mass 16, which is specially shaped as a cylinder, made of ferromagnetic material, through which the magnetic flux passes, as shown in Figs. lOa-lOc. The hybrid actuator module 30 also comprises springs 36 and 56, as well as a damping element 4 made from material with damping properties, such as a polymer (although any other passive damping material like oil can be used). The overall needed stiffness and damping properties are determined by a controller through electromagnets. The controller may be configured to control the operation of the electromagnetic actuator assembly, based on robust adaptive - 13 - dynamic programming (an algorithmic technique used to solve complex problems by breaking them down into simpler, overlapping subproblems) and utilizing reinforcement learning (a machine learning paradigm where an agent learns to make decisions in an environment to maximize a cumulative reward), small gain theorem (analyzing the behavior of certain control systems that contain or utilize saturation), and gain scheduling method (a control strategy used for nonlinear systems, where a family of linear controllers, each designed for a specific operating point, is employed).

[0067] A controlled hybrid electromagnetic assembly 66 allows the overall damping of vibrations. Element 26 (which may be for example, a rotary actuator) of the hybrid actuator module 30 functions as a a holder that enables rotation on the axis of the electromagnetic assembly for allowing the rotation of the electromagnet assembly to a desired angle, to stimulate the oscillating mass to apply a damping force, based on a combination of the applied magnetic field and stiffness and damping properties, such that the damping force angle is aligned with the direction of the unwanted vibration, towards the vibration direction. The stator is located in the center, and the oscillating mass operates peripherally. In one embodiment, the damping force direction is precisely opposite to the direction of the chatter-induced force.

[0068] The angle can be adjusted manually, or automatically, by the rotary actuator (a device that converts energy, into rotational motion. It produces torque and is used to move objects in a circular or oscillating motion within a limited range, often less than a full revolution) or be self-adjusted, by a physical characteristic force such as a body oscillating around the center of mass. The angle is adjusted to be aligned with the chatter cutting force. The optimal force direction may be achieved through selfcentering, manual adjustment, or using a rotary actuator, or any combination thereof. - 14 -

[0069] Fig. 7 illustrates how the hybrid actuator module 30 can achieve force alignment by changing the angle in response to variations in the direction of chatter forces. The angle of the damping force application is changed through rotational movement around its central axis.

[0070] Fig. 8 shows a two-axis stator (electromagnetic actuator) 80 with a rotating and oscillating outer mass 81, according to an embodiment of the invention. By controlling both axes, an equal force in any required direction can be achieved. This capability requires two bipolar current controllers.

[0071] Fig. 9 illustrates the structure of a hybrid rotating stator 90, made of a ferromagnetic material with a bore 91 along its central axis, for allowing the passage of cooling fluid and serving as the rotation axis. Permanent magnets 39 and 49 generate bias by means of a constant magnetic field, intended to elicit a rapid response from the hybrid actuator module 30 without requiring a constant electrical current. Also, using the permanent magnets reduces the current required to flow in the electromagnet, since they already generate a magnetic flux, which is completed by the electromagnet to achieve a desired damping effect. The electromagnet coils 29 and 59 have a number of turns through which the desired electrical current (to the electromagnets of the electromagnet assembly to obtain a controllable magnetic field) passes, to create the required magnetic force.

[0072] Fig. 10a shows the magnetic flux lines obtained without electrical current, allowing for an optimal operating point. Fig. 10b shows the magnetic flux lines and their intensity with the application of negative current. Fig. 10c shows the magnetic flux lines and their intensity with the application of positive current.

[0073] In turning operations, the hybrid actuator module 30 embedded at the end of a boring bar 20 plays a key role in reducing chatter by generating anti-vibration waves that stabilize the cutting or turning process. According to another embodiment, the hybrid actuator module 30 is further adapted to function as a chip breaker, to disconnect continuous chips 111, formed in the workpiece 110 (Figs, lla-llb). The - 15 - hybrid actuator module 30, positioned inside the boring bar 20, is controlled by dedicated algorithm to induce, by an active force 113 at a desired angle 0, radial vibrations which are perpendicular to the workpiece 110 surface, as shown in Figs, lla-llb. This vibration-assisted machining approach allows efficient chip breaking.

[0074] Two complementary methods (called herein the phase shift method and the high- frequency vibration method) are used to enhance the functionality of the hybrid actuator module 30, for the purpose of chip breaking, depending on the type of metal to be machined or turned. These complementary methods allow the actuator's dual role to minimize chatter while optimizing chip breaking, thereby improving machining efficiency and surface quality.

[0075] In the phase shift method, the timing between the radial oscillations of the hybrid actuator module 30 and the workpiece rotation is adjusted, as shown in Fig. 12. According to the phase shift method intermittent chip thickness variations are created, to cause chip breaking. The phase shift refers to the relative timing or angular displacement between the oscillation of the hybrid actuator module 30 embedded at the end of a boring bar 20 and the rotation of the workpiece 110 or the tool's feed motion in a turning process. Precise control of the phase shift, along with the amplitude and frequency of the actuator's radial vibrations, is critical for effective chip breaking and preventing the creation of long, continuous chips. The phase shift between the actuator's radial oscillations and the workpiece rotation (or tool feed) controls the chip formation and breakage. By optimizing the phase shift, the hybrid actuator module 3 modulates the cutting dynamics to obtain efficient chip segmentation. The phase shift works in tandem with the hybrid actuator module's vibration amplitude, vibration frequency, and the machining feed rate, to optimize chip breaking.

[0076] Fig. 12 shows the process of chip braking using the phase shift method. The thickness of the formed continuous chips is shown between the lines 121 and 122, - 16 - where the step of the boring bar 2 is 0.005 inches. Dotted line 123 represents the phase shift over time. As a result, at point a on the graph, the chip thickness becomes almost zero and the current chip brakes, while the creation of a new chip begins. This process is repeated to obtain chip breaking every predetermined or desired cycle.

[0077] Fig. 13 shows the process of chip braking using the high-frequency vibration method. In the high-frequency vibration method (for chip breaking) rapid oscillations of a cutting tool caused by the hybrid actuator module 30 (that generates a high- frequency wave 131) are used to interrupt continuous chip formation during machining, such as turning. This method uses high-frequency vibrations (typically in the range of 100 Hz to several kHz) to create intermittent cutting action, thereby causing chips to break into smaller, manageable pieces. This reduces entanglement, improves surface finish, prolongs the tool life, and increases operational safety. High- frequency Vibration-Assisted Machining (VAM) often uses actuators such as piezoelectric or electrodynamic systems, to obtain precise and rapid oscillations. The generated high-frequency wave 130 overrides on the anti-vibration wave and further induce rapid oscillations to effectively cause chips segmentation, thereby preventing long, tangled chip formations. The generation of a high-frequency wave 130 is repeated as required.

[0078] As various embodiments and examples have been described and illustrated, it should be understood that variations will be apparent to one skilled in the art without departing from the principles herein. Accordingly, the invention is not to be limited to the specific embodiments described and illustrated in the drawings.

Claims

- 17 -Claims1. An electromagnetic actuator assembly, integrated within a boring tool, for controlling unwanted machining vibration, comprising: a) an outer oscillating mass made of ferromagnetic material, through which the magnetic flux can pass; b) an inner stator that comprises an electromagnet assembly, located at the center of said oscillating mass, for applying a controllable magnetic field to said oscillating mass; c) one or more damping elements, each having one or more springs and / or a damping material with predetermined stiffness and damping properties; d) a controller for providing a desired current to the electromagnets of said electromagnet assembly to obtain said controllable magnetic field; and e) a holder for allowing the rotation of said electromagnet assembly to a desired angle, for stimulating said oscillating mass to apply a damping force, based on a combination of said magnetic field and stiffness and damping properties, wherein the damping force angle is aligned with the direction of said unwanted vibration, towards the vibration direction.

2. An electromagnetic actuator assembly according to claim 1, in which the damping force is adjusted manually, or by a physical characteristic force.

3. An electromagnetic actuator assembly according to claim 1, in which the actuator assembly applies force in one direction, which is manually or automatically adjusted to be aligned with the chatter cutting force.

4. An electromagnetic actuator assembly according to claim 3, in which the optimal force direction achieved through self-centering, manual adjustment, or using an actuator or any combination thereof.- 18 -5. An electromagnetic actuator assembly according to claim 1, in which the damping force is precisely opposite to the direction of the chatter-induced force.

6. An electromagnetic actuator assembly according to claim 1, in which the stator is a two-axis stator being controlled in both axes by two bipolar current controllers, to thereby obtain an equal force in any required direction.

7. An electromagnetic actuator assembly according to claim 1, in which the stator is located in the center, and the oscillating mass operates peripherally.

8. An electromagnetic actuator assembly according to claim 1, in which the angle of the damping force application is changed through rotational movement around its central axis.

9. An electromagnetic actuator assembly according to claim 1, in which the stator further comprises a fluid passage formed in the center of said stator for allowing a coolant fluid to flow towards the cutting area.

10. An electromagnetic actuator assembly according to claim 1, in which the controller controls the operation of said electromagnetic actuator assembly, based on robust adaptive dynamic programming utilizing reinforcement learning, small gain theorem, and gain scheduling methods.

11. An electromagnetic actuator assembly according to claim 1, in which the oscillating mass is tubular or shaped as a cylinder.

12. An electromagnetic actuator assembly according to claim 1, in which the damping material is a polymer or oil.- 19 -13. An electromagnetic actuator assembly according to claim 1, further comprising permanent magnets, symmetrically embedded within said stator, such that the stiffness and damping properties are determined by the current flowing through said electromagnet assembly and the magnetic field applied by said permanent magnets.

14. A deep boring tool system, comprising: a) an electromagnetic actuator assembly; b) a deep boring bar, into which said actuator assembly is integrated; c) a cutting tool head connected to said deep boring bar; d) a tool holder, mounted on a lathe; e) a vibration sensor; and f) a control system, connected to said hybrid actuator module wirelessly or via wiring, for providing power supply to said actuator assembly and reading data from said vibration sensor.

15. A deep boring tool system according to claim 14, in which the vibration sensor is an accelerometer for measuring vibrations and the overall force direction developed from the vibrations.

16. An electromagnetic actuator assembly according to claim 1, in which the controller is adapted to disconnect continuous chips formed in the workpiece by generating radial vibrations being perpendicular to the workpiece surface.

17. A deep boring tool system according to claim 14, in which the controller is adapted to disconnect continuous chips formed in the workpiece by generating radial vibrations being perpendicular to the workpiece surface.

18. A deep boring tool system according to claim 17, in which chip breaking is caused by intermittent chip thickness variations that are created by adjusting the timing- 20 - between radial oscillations of the hybrid actuator module and the workpiece rotation.

19. A deep boring tool system according to claim 17, in which chip breaking is caused by adjusting the relative timing or angular displacement between the oscillation and the tool's feed motion in a turning process.

20. A deep boring tool system according to claim 14, in which the controller is adapted to disconnect continuous chips formed in the workpiece by interrupting continuous chip formation using a high-frequency wave that generates high- frequency vibrations to create intermittent cutting action.

21. A deep boring tool system according to claim 14, in which the vibration sensor is an accelerometer for measuring vibrations and the overall force direction developed from the vibrations.

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