Damper device, machine tool and assembly method of a damper device

Abstract

A damper device (12) for a machine tool (10), the damper device comprising a tubular element (20) having a cavity (40) and a central axis (18), the tubular element comprising a first surface (48); a damping mass (32) arranged within the cavity and movable radially relative to the central axis and relative to the tubular element; at least one spring element (34, 36) supporting the damping mass relative to the tubular element, the damping mass and the at least one spring element being arranged to attenuate vibrational kinetic energy of the damper device; at least one fixing portion (26) having a second surface (54) and a fixed inner portion (50) within the cavity; and a vibration damping material (30) disposed between the first surface and the second surface, the vibration damping material being arranged to attenuate vibrational potential energy of the damper device; wherein the vibration damping material is substantially uniformly compressed between the first surface and the second surface.

Description

TECHNICAL FIELD

[0001] The present disclosure relates generally to damper devices for machining operations. In particular, a damper device for a machine tool, a machine tool comprising such a damper device, a method of assembling a damper device for a machine tool, a damper device assembled according to the method and a machine tool comprising such a damper device are provided. BACKGROUND

[0002] Machine tools can be used for various machining processes, such as milling, turning, boring, grinding and drilling processes. Machine tools can comprise one or more cutting teeth and a tool holder holding the cutting teeth. Machining vibrations, also referred to as chatter, occur naturally during machining operations and correspond to the relative movement between the workpiece and the machine tool. Machine tools typically use material removal rate as a key performance indicator. High material removal rates require high speeds, high depths of cut and high feed rates. All three parameters will tend to increase vibrations in the machine tool during machining processes. However, vibrations of the machine tool deteriorate the surface quality of the machined workpiece, limit the production rate and increase the production cost.

[0003] To attenuate vibrations in the machine tool, the machine tool can comprise a tuned mass damper assembly comprising a damping mass. By tuning the natural frequency of the mass damper assembly to match the vibration frequency of the machine tool, vibration energy is transferred to the damping mass to stabilize the movement of the machine tool. The natural frequency of the mass damper assembly is typically tuned by manually fine-tuning the support stiffness of the damping mass, so that a match of the two frequencies is obtained. The manual tuning step of the mass damper assembly is complex and requires knowledge in structural vibration analysis. For this reason, pre-tuned mass dampers with a viscous fluid inside are commonly used. Machine tools with pre-tuned mass dampers perform well in their target frequency range, which is typically determined by their diameter, their overhang and the stiffness of the machine tool clamps.

[0004] WO2018044216A1 and WO2019168448A1 each disclose a machine tool having a mass damper assembly with a spring element and a damping mass. The spring element comprises a material having a frequency dependent elastic modulus to provide a self-tuning effect. The self-tuning effect significantly increases the operating frequency range of the mass damper assembly. SUMMARY

[0005] It is an object of the present disclosure to provide a damper device for a machine tool having improved performance.

[0006] It is another object of the present disclosure to provide a damper device for a machine tool that improves surface finishing capabilities of the machine tool.

[0007] It is another object of the present disclosure to provide a damper device for a machine tool that has improved vibration damping.

[0008] It is another object of the present disclosure to provide a damper device for a machine tool that has improved vibration damping over a wider range of vibration frequencies.

[0009] It is another object of the present disclosure to provide a damper device for a machine tool that has a cost-effective, reliable and / or less complex design.

[0010] It is another object of the present disclosure to provide a damper device for a machine tool that enables a cost-effective, reliable and / or less complex assembly.

[0011] It is another object of the present disclosure to provide a damper device for a machine tool that has a high stiffness.

[0012] It is another object of the present disclosure to provide a damper device for a machine tool that has a long service life.

[0013] It is another object of the present disclosure to provide a damper device for a machine tool that solves several or all of the above-mentioned objects in combination.

[0014] It is another object of the present disclosure to provide a machine tool comprising a damper device that solves one, several or all of the above-mentioned objects.

[0015] It is another object of the present disclosure to provide a method of assembling a damper device for a machine tool that solves one, several or all of the above-mentioned objects.

[0016] It is another object of the present disclosure to provide a method of assembling a damper device for a machine tool that is cost-effective, reliable and / or less complex.

[0017] It is another object of the present disclosure to provide a method of assembling a damper device for a machine tool that enables a fast implementation.

[0018] According to a first aspect, there is provided a damper device for a machine tool, the damper device comprising a tubular element having a cavity and a central axis, the tubular element comprising a first surface; a damping mass arranged within the cavity and being movable radially with respect to the central axis and with respect to the tubular element; at least one spring element supporting the damping mass with respect to the tubular element, the damping mass and the at least one spring element being arranged to dampen vibrational kinetic energy of the damper device; at least one fixation portion having a second surface and a fixation inner portion inside the cavity; and a vibration damping material arranged between the first surface and the second surface, the vibration damping material being arranged to dampen vibrational potential energy of the damper device; wherein the vibration damping material is substantially uniformly compressed or uniformly compressed between the first surface and the second surface.

[0019] When a cutting force is applied to a cutting tooth supported by the damper device, vibrations are excited in the damper device. Then, vibrational energy carried by the vibration waves will be converted between vibrational kinetic energy and vibrational potential energy inside the machine tool. When the vibrational kinetic energy is highest, the vibrational potential energy is lowest, and vice versa, because the sum of the vibrational kinetic energy and the vibrational potential energy is substantially constant, if not damped. When the vibration waves reach the vibration damping material, the vibration waves are damped by the vibration damping material and reflected and / or transmitted through the vibration damping material. When the vibration waves reach the damping mass, the vibration waves are damped and reflected by the damping mass. The process continues until the vibration waves are fully damped.

[0020] The damping mass supported by the at least one spring element will dampen the vibrational kinetic energy, and the vibration damping material will dampen the vibrational potential energy. Thus, the damper device will sequentially dampen the vibrational energy. The vibration damping material can be sheared and further compressed to dampen the vibrational potential energy.

[0021] Further, the damper device will vibrate at multiple frequencies during machining. Another advantage of the damper device is that the vibration damping material will also dampen vibrations at frequencies outside the nominal range of the mass damper assembly.

[0022] By means of the vibration damping material, the vibration damping capacity of the damper device is significantly improved. Thus, the machining performance of the damper device is also significantly improved.

[0023] The damper device comprises a mass damper assembly and a structural damper assembly. The mass damper assembly comprises a damping mass and at least one spring element. The structural damper assembly comprises a damping material. The structural damper assembly can further comprise a first surface and a second surface. Thus, the structural damper assembly constitutes an additional damping source in addition to the mass damper assembly. Each of the mass damper assembly and the structural damper assembly can be assembled on one or more of the at least one fixed part.

[0024] The compression of the damping material prior to use of the damper device locks the shape of the damping material. As the damping material is compressed between the first surface and the second surface, a twisting of the damping material leading to damage can be avoided. During assembly, the damping material can be compressed at least 3%, such as at least 5%, such as at least 10% from an uncompressed state in a radial direction relative to the central axis.

[0025] The damping material can be symmetrically distributed relative to the central axis. For example, the damping material can surround the first surface or the second surface. The compression of the damping material will help to center the at least one fixed part relative to the central axis.

[0026] The damping material can extend along the central axis. For example, the length of the damping material along the central axis can be at least half the length of the damping mass along the central axis, such as more than the length of the damping mass along the central axis.

[0027] The first surface and the second surface can have substantially corresponding shapes or corresponding shapes. The damping material can be provided as a layer between the first surface and the second surface. The first surface can be in contact or not in contact with the second surface.

[0028] The fixed inner part can be fitted into the cavity by a transition fit or an interference fit. In this way, the bending area of the moment of force can be maintained when the fixed inner part is inserted into the cavity, despite the introduction of the structural damper assembly. Thus, the introduction of the structural damper assembly has minimal impact on the static stiffness of the damper device when the damper device is clamped in a tool holder.

[0029] Throughout this disclosure, the damper device can be a tool holder or a tool. A possible difference between a tool and a tool holder is that a tool comprises one or more cutting teeth, while a tool holder does not comprise cutting teeth.

[0030] The damper device can be used for various machining operations, such as milling, turning, boring, grinding, and drilling operations. The damper device can be configured to hold or support one or more cutting teeth for machining a workpiece. In this case, the cutting teeth can be detachably connected to the damper device or can be integrally formed with the damper device. The damper device can for example be a tool holder which supports another tool holder which in turn holds the cutting teeth.

[0031] The damper device can comprise an end effector. The mass damper assembly can be arranged between the end effector and the structural damper assembly. The end effector is provided at a front end of the damper device. The damper device thus further comprises a rear end opposite the front end.

[0032] The tubular element and the at least one fixation portion can be made of the same material. Examples of suitable materials include steel, tungsten alloy, and tungsten carbide. The tubular element can comprise a cylindrical outer surface and / or a cylindrical inner surface.

[0033] The damper device can further comprise a rear end. In this case, each of the at least one fixation portion is directly or indirectly fixed to the rear end. In the present disclosure, the fixation portion can alternatively be referred to as a locking portion.

[0034] The damping mass can be supported on one or both sides by one or more spring elements. The damping mass may, for example, be supported on one side by only one spring element and on the opposite side by only one spring element. Alternatively, the damping mass can be supported on one side by a plurality of spring elements and on the opposite side by a plurality of spring elements. Alternatively, the damping mass can be supported on one side only by one or more spring elements and can not be supported on the opposite side.

[0035] Each spring element can be configured to convert vibrational energy into heat. Each spring element can be an elastic element. Each spring element can have a frequency-dependent elastic modulus. In this way, a self-tuning effect can be obtained. For example, the spring element can have a frequency-dependent elastic modulus such that the resonance frequency of the damping mass substantially matches or matches the vibrational frequency of the damper device in a range of vibrational frequencies from 100 Hz to 1000 Hz, for example from 20 Hz to 3000 Hz. Materials having such a frequency-dependent stiffness can have a structural dimension of 100 nm or less in at least one dimension.

[0036] As an alternative to a material having such a frequency-dependent elastic modulus, the at least one spring element can be made of rubber or an elastomer. Rubber and elastomers generally have a damping ratio below 10%.

[0037] The first surface and the second surface can be tapered. By means of the tapered design of the first surface and the second surface, the damper device provides a self-locking effect when compressing the damping material. The self-locking effect refers to the fact that the force exerted by the damping material on the first surface and the second surface due to the compression of the damping material does not cause a separation between the first surface and the second surface.

[0038] The tapered design of the first surface and the second surface also enables a high pre-compression of the damping material. In this way, at least 95% of the surface area of the damping material, for example almost 100% of the surface area, can be in contact with the first surface and the second surface. This in turn enables the damper device to have a high performance to transmit the vibration wave through the damping material, thereby effectively damping the vibration potential energy. Furthermore, the tapered design in combination with the compression of the damping material enables to avoid any gap between the damping material and the first surface and / or the second surface and to avoid that the damping material is smeared away due to frictional resistance.

[0039] The first surface and the second surface can be rotationally symmetrical with respect to the central axis. For example, each of the first surface and the second surface can be conical. As a possible alternative, the tapered shape can comprise a convex or concave shape of the first surface and the second surface.

[0040] In case the first surface is arranged outside of the second surface, the tapered front end portion can be smaller than the tapered rear end portion. That is, the tapered design can be configured such that the front end portions of the first surface and the second surface span a smaller area than the rear end portions of the first surface and the second surface, respectively. In contrast, in case the first surface is arranged inside of the second surface, the tapered front end portion can be larger than the tapered rear end portion. The tapered shape of the first surface and the second surface makes the damper device very easy to assemble.

[0041] The first surface and / or the second surface can have an average inclination with respect to the central axis of at least 0.2 degrees, for example at least 0.5 degrees, for example at least 1 degree, for example 1.5 degrees. Alternatively or additionally, the first surface and the second surface can have an average inclination with respect to the central axis of less than 30 degrees, for example less than 10 degrees, for example less than 5 degrees.

[0042] The at least one fixing portion can be assembled by a relative movement between the tubular element and the at least one fixing portion along the central axis such that the damping material is substantially uniformly compressed or uniformly compressed between the first surface and the second surface.

[0043] When assembling the damper device, at least one of the one or more fixation parts can be inserted into the cavity. The at least one fixation part can be inserted into the cavity from the rear end of the tubular element. Alternatively or additionally, the mass damper assembly can be inserted into the cavity from the rear end of the tubular element. Inserting the at least one fixation part and the mass damper assembly into the tubular element does not substantially affect the geometric accuracy of the cutting teeth held by the tubular element. By sliding the at least one fixation part into the cavity, a uniform pre-compression is applied to the damping material without deforming, smearing and damaging the damping material. The design of the damper device enables simultaneous and uniform pre-compression on one or more surface areas of the damping material.

[0044] Before compressing the damping material between the first surface and the second surface, the tubular element can be formed as a single piece. In this way, the stiffness of the tubular element is high. As a result, the geometric accuracy of the damper device is high.

[0045] As a possible alternative, the tubular element can be formed as two halves (e.g. split in a plane comprising the central axis). In this case, one or more of the mass damper assembly, the damping material, and the at least one fixation part can be inserted radially into the first half. Then, the second half can be connected to the first half to close the tubular element, and thereby uniformly compress the damping material. In this variant, the first surface and the second surface need not be tapered.

[0046] The damping material can comprise a viscoelastic material. Such a viscoelastic material is solid, but can easily deform and twist due to friction or adhesion. The viscoelastic material can be a polymer material. Alternatively or additionally, the viscoelastic material can be a pressure sensitive adhesive. One example of a damping material is an acrylic resin polymer.

[0047] The cavity can comprise a cylindrical cavity portion. In this case, the damper mass can be arranged within the cylindrical cavity portion. Furthermore, at least a portion of one or more of the at least one fixation part can be arranged within the cylindrical cavity portion.

[0048] The cavity can comprise a tapered cavity portion defining the first surface. Alternatively, the first surface can be a tapered outer surface of the tubular element.

[0049] The at least one fixation part can comprise at least two fixation parts fixed relative to each other. Each of the at least two fixation parts can be fixed to the rear end of the damper device or the machine tool.

[0050] The fixed inner portion can comprise a fixed cylindrical portion. In this case, the fixed cylindrical portion can be assembled into the cylindrical cavity portion by means of a transition fit or an interference fit. However, the fixed cylindrical portion and the cylindrical cavity portion can comprise irregularities to improve the fit between them and / or to improve the alignment between the at least one fixed portion and the tubular element. For example, the fixed cylindrical portion and the cylindrical cavity portion can comprise recesses and corresponding grooves. Alternatively or additionally, the fixed cylindrical portion and the cylindrical cavity portion can have corresponding slightly elliptical cross-sectional shapes.

[0051] One or more of the at least one spring element can be connected to the fixed inner portion. Thus, the damper device can comprise at least one spring element between the damping mass and the fixed inner portion.

[0052] The second surface can be inserted into the cavity. Alternatively, the second surface can surround the tubular element.

[0053] The at least one fixed portion can comprise a mandrel. In this case, each of the mass damper assembly and the structural damper assembly can be assembled on the mandrel.

[0054] The damping material can have a damping ratio of at least 10%, for example at least 20%, for example at least 30%. Most metals have a damping ratio of 0% to 0.1%. Rubber can have a damping ratio of 5% to 7.5%. The loss factor can be defined as twice the damping ratio. Thus, the damping material can have a corresponding ratio of at least 20%, for example at least 40%, for example at least 60%. The damping material need not have a frequency-dependent elastic modulus as described for the at least one spring element.

[0055] The first surface and the second surface can be conical. Alternatively or additionally, the first surface and the second surface can be parallel.

[0056] The damping material can have a thickness of less than 1 mm, for example less than 0.5 mm, for example less than 0.2 mm, for example 0.1 mm.

[0057] The damping material has a Poisson's ratio of at least 0.35, for example at least 0.4, for example at least 0.45. The damping material can have a bulk modulus of 1.1 times to 16.7 times its Young's modulus, for example 3.3 times. Alternatively or additionally, the damping material can have a bulk modulus of 3 times to 49.7 times its shear modulus, for example 9.7 times.

[0058] According to a second aspect, there is provided a machine tool comprising a damper device according to the first aspect. The machine tool can be configured to machine a workpiece. The machine tool can for example be a milling tool, a turning tool, a boring tool, a grinding tool or a drilling tool.

[0059] According to a third aspect, there is provided a method of assembling a damper arrangement for a machine tool, the method comprising providing a tubular element having a cavity and a central axis, the tubular element comprising a first surface; providing a damping mass arranged within the cavity and being movable radially relative to the central axis and relative to the tubular element; providing at least one spring element supporting the damping mass relative to the tubular element, the damping mass and the at least one spring element being arranged to dampen vibrational kinetic energy of the damper arrangement; providing at least one fixation part having a second surface and a fixation inner part inside the cavity; providing a vibration damping material between the first surface and the second surface, the vibration damping material being arranged to dampen vibrational potential energy of the damper arrangement; and positioning the first surface and the second surface relative to each other such that the vibration damping material is substantially uniformly compressed or uniformly compressed between the first surface and the second surface.

[0060] The first surface and the second surface can be tapered. In this case, the method can further comprise moving the tubular element and the at least one fixation part relative to each other along the central axis such that the vibration damping material is substantially uniformly compressed or uniformly compressed between the first surface and the second surface.

[0061] According to a fourth aspect, there is provided a damper arrangement assembled according to the method of the third aspect. The damper arrangement according to the fourth aspect can be of any type according to the first aspect.

[0062] According to a fifth aspect, there is provided a machine tool comprising a damper arrangement according to the fourth aspect. The machine tool according to the fifth aspect can be of any type according to the second aspect. BRIEF DESCRIPTION OF DRAWINGS

[0063] Further details, advantages and aspects of the disclosure will become apparent from the following description taken in conjunction with the drawings, in which:

[0064] Figure 1 Fig. 1 schematically illustrates a perspective side view of a machine tool comprising a damper arrangement;

[0065] Figure 2 Fig. 2 schematically illustrates a side view of another example of a damper arrangement;

[0066] Figure 3 Fig. 3 schematically illustrates a cross-sectional side view of the damper arrangement in Fig. 1 in an unassembled state; Figure 2 Fig. 4 schematically illustrates a cross-sectional side view of the damper arrangement in Fig. 2 in an unassembled state;

[0067] Figure 4 Fig. 5 schematically illustrates a cross-sectional side view of the damper arrangement in Fig. 1 in an assembled state; Figure 2 Fig. 6 schematically illustrates a cross-sectional side view of the damper arrangement in Fig. 2 in an assembled state; and3 a cross-sectional side view of the damper device in

[0068] Figure 5 a side view schematically illustrating another example of a damper device;

[0069] Figure 6 a cross-sectional side view of the damper device in Figure 5

[0070] Figure 7 a cross-sectional side view of the damper device in Figure 5 and 6

[0071] Figure 8 a side view schematically illustrating another example of a damper device;

[0072] Figure 9 a cross-sectional side view of the damper device in Figure 8

[0073] Figure 10 a cross-sectional side view of the damper device in Figure 8 and 9

[0074] Figure 11 a perspective side view schematically illustrating another example of a machine tool comprising another example of a damper device;

[0075] Figure 12 a cross-sectional side view of the damper device in Figure 11

[0076] Figure 13 a cross-sectional side view of the damper device in Figure 11 and 12

[0077] Figure 14 a perspective side view schematically illustrating another example of a damper device;

[0078] Figure 15 a cross-sectional side view of the damper device in Figure 14

[0079] Figure 16 a cross-sectional side view of the damper device in Figure 15 ​​​​​​​​DETAILED DESCRIPTION

[0080] In the following, a damper device for a machine tool, a machine tool comprising such a damper device, a method of assembling a damper device for a machine tool, a damper device assembled according to the method, and a machine tool comprising such a damper device will be described. Identical or similar reference numerals will be used to denote identical or similar structural features.

[0081] Figure 1 A perspective side view of a machine tool 10a, in this example a milling cutter, is schematically shown. The machine tool 10a comprises a tool holder 12 and a plurality of cutting teeth 14 for machining a workpiece (not shown). The tool holder 12 is one example of a damper device according to the present disclosure. The machine tool 10a of this example comprises four cutting teeth 14.

[0082] The tool holder 12 comprises an end effector 16, in this example a milling head. The end effector 16 is provided at a front end of the tool holder 12. The cutting teeth 14 are connected to the end effector 16. Figure 1 A central axis 18 of the machine tool 10a is also shown.

[0083] The tool holder 12 further comprises a tubular element 20. The tubular element 20 is concentric with the central axis 18. In this example, the end effector 16 is connected to the tubular element 20.

[0084] The tool holder 12 further comprises a rear end 22. In operation of the machine tool 10a, the rear end 22 is fixedly clamped in a tool holder clamp, for example a rotatable spindle (not shown) of the machine tool. During machining of the workpiece, there is relative movement between the machine tool 10a and the workpiece, for example relative rotation around the central axis 18. Thus, the machine tool 10a can be moved and the workpiece can be stationary, or vice versa.

[0085] Figure 2 A side view of a further example of a tool holder 12a is schematically shown. The tool holder 12a is one example of a damper device according to the present disclosure. The tool holder 12a can replace the tool holder 12 in Figure 1 The tool holder 12a comprises a tubular element 20a. The tool holder 12a differs from the tool holder 12 in that the end effector 16 is integrally formed with the tubular element 20a. Figure 2 One of a plurality of seats 24 is also shown, to which a cutting tooth 14 can be connected.

[0086] Figure 3 A perspective view of the tool holder 12a in an unassembled state is schematically shown. Figure 2Figure 2 shows a cross-sectional side view of the tool holder 12a of Figure 1. In addition to the tubular element 20a, the tool holder 12a comprises a fixed portion 26a, a mass damper assembly 28, and a damping material 30. The tubular element 20a and the fixed portion 26a can be made of the same material, for example steel, tungsten alloy, or tungsten carbide.

[0087] The mass damper assembly 28 of this example comprises a damping mass 32 and one spring element 34 and 36 on each side of the damping mass 32. The tool holder 12a further comprises a structural damper assembly 38 which in turn comprises the damping material 30. Here, the mass damper assembly 28 is arranged between the end effector 16 and the structural damper assembly 38. Here, each of the mass damper assembly 28 and the damping material 30 are arranged on the fixed portion 26a.

[0088] The tubular element 20a comprises a cavity 40a. The cavity 40a is open at the rear end and closed at the front end by the end effector 16. The cavity 40a of this example comprises a cylindrical cavity portion 42a and a tapered cavity portion 44a, here exemplified as a conical cavity portion. The cylindrical cavity portion 42a and the tapered cavity portion 44a meet at an edge 46a. The cylindrical cavity portion 42a extends along the central axis 18 a longer distance than the tapered cavity portion 44a, here approximately 20% longer. The inner surface of the tapered cavity portion 44a forms one example of a first surface 48a according to the present disclosure. The diameter of the first surface 48a is smaller at the edge 46a than at the rear end.

[0089] The tubular element 20a of this example has a constant outer diameter. Furthermore, the tubular element 20a is formed as a single piece. The tool holder 12a with the tubular element 20a formed as a single piece results in a run-out of the cutting teeth 14 relative to a clamping area of the tool holder 12a, for example in the rear end 22 of the tool holder 12a, of less than 10 pm.

[0090] The fixed portion 26a is here exemplified as a mandrel. The fixed portion 26a comprises a fixed inner portion 50a and a fixed tapered portion 52a. In this example, the fixed inner portion 50a is cylindrical and the fixed tapered portion 52a is conical. The outer surface of the fixed tapered portion 52a forms one example of a second surface 54a according to the present disclosure. The first surface 48a and the second surface 54a have respective conical shapes. In this example, each of the first surface 48a and the second surface 54a is inclined by 1.5 degrees relative to the central axis 18. The fixed portion 26a further comprises a central bore 56 extending therethrough along the central axis 18.

[0091] As Figure 3As shown, the damping material 30 is provided as a thin, uniform thickness layer on the second surface 54a. The damping material 30 substantially covers the entire second surface 54a, e.g., covers at least 95% thereof, e.g., covers at least 99% thereof. In this particular example, the damping material 30 is longer along the length of the central axis 18 than the damper mass 32 along the length of the central axis 18, here about twice as long.

[0092] The tool holder 12a of this example further comprises a front lock 58. The damper mass 32 is arranged between the front lock 58 and the fixed inner portion 50a.

[0093] The tool holder 12a of this example further comprises a front thermal barrier element 60 and a rear thermal barrier element 62. The front and rear thermal barrier elements 60, 62 provide thermal protection, e.g., for dry machining. The front thermal barrier element 60 is arranged between the front lock 58 and the front spring element 34. The front thermal barrier element 60 is received in a recess of the front lock 58.

[0094] The rear thermal barrier element 62 is arranged between the rear spring element 36 and the fixed inner portion 50a. The rear thermal barrier element 62 is received in a recess in the fixed inner portion 50a. In this way, the damper mass 32 is connected to the fixed inner portion 50a via the rear spring element 36 and the rear thermal barrier element 62. Providing the front and rear thermal barrier elements 60, 62 in respective recesses improves the alignment with the central axis 18.

[0095] The front spring element 34 can be attached to each of the front thermal barrier element 60 and the damper mass 32. The rear spring element 36 can be attached to each of the damper mass 32 and the rear thermal barrier element 62.

[0096] The tool holder 12a of this example further comprises three O-rings 64, 66, and 68. The first O-ring 64 is received in a radially outer groove in the front lock 58. The second O-ring 66 is received in a radially outer groove in a rear region of the fixed inner portion 50a. The third O-ring 68 is received in a radially outer groove in a rear region of the fixed tapered portion 52a.

[0097] The tool holder 12a of this example further comprises a fluid conduit 70. The fluid conduit 70 is in fluid communication with the bore 56. The fluid conduit 70 is connected to the fixed portion 26a. In this particular example, the fluid conduit 70 is threadably connected into a front opening of the fixed inner portion 50a.

[0098] The damping material 30 has a damping ratio of more than 10%, for example more than 30%. The damping material 30 comprises a solid phase of an acrylic resin. Such an acrylic resin behaves as an elastic solid when it is subjected to a compression load, and as a high viscosity fluid when it is subjected to a shear or tensile load. At room temperature (20°C), the acrylic resin can have a Young's modulus E of 0.15 MPa to 60 MPa, a shear modulus G of 0.05 MPa to 20 MPa, a bulk modulus K of 2.5 MPa to 1000 MPa and / or a Poisson's ratio υ of about 0.49.

[0099] The bulk modulus K can be defined as:

[0100]

[0101] or as:

[0102]

[0103] In this example, the spring elements 34 and 36 are also made of acrylic resin. Thus, the damping material 30 and the spring elements 34 and 36 can be made of the same material.

[0104] As Figure 3 illustrated, the tool holder 12a of this example is initially provided in a first unit 72a and a second unit 74a. The first unit 72a comprises the tubular element 20a and the end effector 16. The second unit 74a comprises the fixed part 26a, the mass damper assembly 28 and the damping material 30. The second unit 74a further comprises the front lock 58, the O-rings 64, 66 and 68, the front thermal isolation element 60, the rear thermal isolation element 62 and the fluid conduit 70.

[0105] Figure 4 A cross-sectional side view of the tool holder 12a in the assembled state is schematically illustrated in Figure 2 and 3 The tool holder 12a of this example is assembled by inserting the fixed part 26a with the mass damper assembly 28 and the damping material 30 into the cavity 40a. Due to the correspondingly tapered first surface 48a and second surface 54a and due to the compressibility of the damping material 30, the first surface 48a and the second surface 54a become positioned relative to each other such that the damping material 30 is uniformly compressed therebetween when the fixed part 26a enters the cavity 40a. The damping material 30 can be compressed, for example, by 10% from its original thickness (in Figure 3 The compression of the damping material 30 will help to center the fixed part 26a relative to the central axis 18, for example with a precision of 0.01 mm.

[0106] By sliding the fixed portion 26a along the central axis 18 into the cavity 40a in this manner, a uniform pre-compression is applied to the damping material 30 without deforming, rubbing off, or damaging it. In this specific example, the damping material 30 is disposed between the first surface 48a and the second surface 54a, such that the first surface 48a does not contact the second surface 54a.

[0107] When the fixed part 26a is moved to compress the damping material 30, the damping material 30 may also be slightly sheared. However, compression is the main stress on the damping material 30 during assembly.

[0108] The tapered design of the first surface 48a and the second surface 54a provides high compressibility during assembly. The compression of the damping material 30 provides a self-locking effect, preventing the first surface 48a and the second surface 54a from separating from each other.

[0109] The fixed internal portion 50a is fitted into the cylindrical cavity portion 42a via a transition fit. Thus, despite the introduction of the structural damper assembly 38, the bending region of the moment can be maintained when the fixed internal portion 50a is inserted into the cavity 40a. Consequently, the introduction of the structural damper assembly 38 has minimal impact on the static stiffness of the tool holder 12a when it is clamped in the tool holder.

[0110] When the retaining part 26 is inserted into the cavity 40a, the mass damper assembly 28 connected to the retaining part 26a enters the cylindrical cavity portion 42a in front of the retaining part 26a. The retaining part 26a is secured to the rear end 22 before or after assembling the tool holder 12a.

[0111] like Figure 4 As shown, the structural damper assembly 38 in this example also includes a first surface 48a and a second surface 54a. A damping mass 32 is disposed within a cylindrical cavity portion 42a and is radially movable relative to the central axis 18 and relative to the tubular element 20a. Spring elements 34 and 36 support the damping mass 32 relative to the tubular element 20a. O-rings 64, 66, and 68 provide a seal for the cavity 40a and protect the mass damper assembly 28 and the structural damper assembly 38 from oil and dust in the machining environment.

[0112] During machining using machine tool 10a, cutting force is applied to the cutting teeth 14, and vibration occurs in all parts of machine tool 10a. Energy-carrying vibration waves propagate back and forth in tool holder 12a. Vibration energy alternates between vibration kinetic energy and vibration potential energy. The vibration kinetic energy from the vibration in tool holder 12a is transferred to damping mass 32 via spring elements 34 and 36 (where the vibration kinetic energy is attenuated and reflected).

[0113] The damping material 30 acts as a spring. The damping material 30 attenuates the potential energy of the vibrations, independent of the frequency of the vibrations of the tool holder 12a. Thus, the damping material 30 is also able to attenuate vibrations at frequencies outside the nominal range of the mass damper assembly 28. The damping material 30 can be sheared and / or further compressed in order to absorb the vibration energy in this way. Part of the vibration wave will also be reflected and / or transmitted through the damping material 30. Vibration waves with frequencies close to the prominent frequencies of the tool holder 12a will be reflected to a greater extent. The prominent frequencies of the tool holder 12a are determined by its structure, for example by its length to diameter ratio.

[0114] The mass damper assembly 28 and the structural damper assembly 38 work simultaneously and independently to attenuate vibrations during a machining operation. The structural damper assembly 38 and the mass damper assembly 28 thus cooperate to effectively attenuate the machining vibrations. Thus, the surface finish provided by the machine tool 10a is improved and the lifetime is increased. The introduction of the structural damper assembly 38 has a minimal impact on the stiffness of the tool holder 12a, the run-out of the cutting teeth 14 and the weight balance of the tool holder 12a.

[0115] In case the damping material 30 is not provided and there is an interference fit between the first surface 48a and the second surface 54a, there will be a very low damping ratio between the tubular element 20a and the fixed portion 26a, for example less than 1%. However, by means of the damping material 30, the damping ratio between the tubular element 20a and the fixed portion 26a can be significantly higher, for example 10% or more. In this way, the damping material 30 is able to attenuate the potential energy of the vibrations more effectively.

[0116] In this example, the tubular element 20a has an outer diameter of 25 mm and the damping material 30 has a thickness of 0.1 mm. Thus, the tool holder 12a has a reduced static stiffness of only 0.1% compared to a corresponding tool holder with an interference fit between the first surface 48a and the second surface 54a. However, due to the damping material 30, the dynamic stiffness of the tool holder 12a is increased by 100% compared to such a corresponding tool holder. The significantly increased dynamic stiffness enables the tool holder 12a to attenuate vibrations more effectively by means of the damping mass 32.

[0117] Figure 5 A side view of a further example of a tool holder 12b is schematically shown. The tool holder 12b is a further example of a damper device according to the present disclosure. Mainly differences with respect to the tool holder 12a are described. The tool holder 12b comprises a tubular element 20b.

[0118] Figure 6 a cross-sectional side view of the tool holder 12b in the unassembled state. As Figure 5 shown, the tubular element 20b is identical to the tubular element 20a. The tubular element 20b comprises a cavity 40b, a cylindrical cavity portion 42b, a tapered cavity portion 44b defining a first surface 48b, and an edge 46b between the cylindrical cavity portion 42b and the tapered cavity portion 44b. Figure 6

[0119] Instead of the fixed portion 26a, the tool holder 12b comprises a first fixed portion 26b1 and a second fixed portion 26b2. The first fixed portion 26b1 is connected to the second fixed portion 26b2 in front of the second fixed portion 26b2. The front parts of the first fixed portion 26b1 and the second fixed portion 26b2 form a fixed inner portion 50b. The fixed inner portion 50b has the same dimensions and functions as the fixed inner portion 50a.

[0120] The second fixed portion 26b2 comprises a fixed tapered portion 52b having a second surface 54b. The fixed tapered portion 52b and the second surface 54b have the same design as the fixed tapered portion 52a and the second surface 54a, respectively.

[0121] Figure 7 a cross-sectional side view of the tool holder 12b in the assembled state. As Figure 5 and 6 shown, the tool holder 12b is assembled by inserting the second unit 74b into the first unit 72b to compress the damping material 30 between the first surface 48b and the second surface 54b. Figure 4

[0122] a side view of another example of a tool holder 12c. The tool holder 12c is another example of a damper device according to the present disclosure. Mainly differences with respect to the tool holder 12a are described. The tool holder 12c comprises a tubular element 20c. Figure 8

[0123] a cross-sectional side view of the tool holder 12c in the unassembled state. The tubular element 20c comprises a cavity 40c having only a cylindrical cavity portion 42c. The tubular element 20c comprises a tapered first surface 48c at its rear end part. The first surface 48c is an outer surface of the tubular element 20c. The first surface 48c is conical and has a larger diameter at its front end part than at its rear end part. Figure 9 Figure 8

[0124] ​​​The tool holder 12c further comprises a first fixed portion 26c1 and a second fixed portion 26c2. The first fixed portion 26c1 and the second fixed portion 26c2 are not directly connected to each other. However, when the tool holder 12c is assembled (e.g. by being fixed to the rear end portion 22), the first fixed portion 26c1 and the second fixed portion 26c2 are fixed relative to each other. The second fixed portion 26c2 surrounds a rear portion of the first fixed portion 26c1.

[0125] The first fixed portion 26c1 is entirely cylindrical (except for the recesses for the second and third O-rings 66, 68). The first fixed portion 26c1 comprises a fixed inner portion 50c having a circular cross-section.

[0126] The second fixed portion 26c2 is generally cylindrical. The second fixed portion 26c2 comprises a fixed tapered portion 52c defining a tapered second surface 54c. The second surface 54c has an inner diameter at the front end portion that is larger than an inner diameter at the rear end portion. The damping material 30 is provided on the second surface 54c.

[0127] Figure 10 A perspective side view of the tool holder 12c in an assembled state is schematically shown in Figure 8 and 9 A cross-sectional side view of the tool holder 12c in the assembled state is schematically shown in FIG. 9. The tool holder 12c can be assembled by fixing the first fixed portion 26c1 and the second fixed portion 26c2 of the second unit 74c to each other (e.g. by being connected to the rear end portion 22) and moving the first unit 72c along the central axis 18 into the space between the first fixed portion 26c1 and the second fixed portion 26c2. Similar to the tool holders 12a and 12b, a relative movement between the first surface 48c and the second surface 54c along the central axis 18 will result in a uniform compression of the damping material 30 therebetween. However, in the tool holder 12c, the second surface 54c surrounds the tubular element 20c.

[0128] Figure 11 A perspective side view of another example of a machine tool 10b comprising a tool 12d is schematically shown in FIG. 10. The tool 12d is another example of a damper device according to the present disclosure. The tool 12d of this example comprises a tubular element 20d and an end effector 16 that is integrally formed with the tubular element 20d. The end effector 16 comprises a plurality of cutting teeth 14, here six helical cutting teeth 14.

[0129] Figure 12 A perspective side view of the tool holder 12c in an unassembled state is schematically shown in Figure 11Figure 6 is a cross-sectional side view of the tool 12d in the assembled state. The tubular element 20d is identical to the tubular element 20a except for the end effector 16. The tubular element 20d includes the cavity 40d, the cylindrical cavity portion 42d, the tapered cavity portion 44d defining the first surface 48d, and the edge 46d between the cylindrical cavity portion 42d and the tapered cavity portion 44d.

[0130] Similar to the tool holder 12b, the tool 12d includes a first fixed portion 26dl and a second fixed portion 26d2. The first fixed portion 26dl is connected to the second fixed portion 26d2 in front of the second fixed portion 26d2. The front portions of the first fixed portion 26dl and the second fixed portion 26d2 form a fixed inner portion 50d. The fixed inner portion 50d has the same dimensions and functionality as the fixed inner portion 50b.

[0131] The second fixed portion 26d2 includes a fixed tapered portion 52d having a second surface 54d. The fixed tapered portion 52d and the second surface 54d have the same design as the fixed tapered portion 52b and the second surface 54b, respectively.

[0132] Figure 13 Figure 7 is a perspective side view of the tool holder 12e in the assembled state. The tool holder 12e is identical to the tool holder 12b except for the mounting interface 76. The mounting interface 76 is identical to the mounting interface 76b. Figure 11 and 12 Figure 8 is a cross-sectional side view of the tool 12d in the assembled state. Similar to the tool 12b in Figure 5, the tool 12d is assembled by inserting the second unit 74d into the first unit 72d to compress the damping material 30 between the first surface 48d and the second surface 54d. Figure 7

[0133] Figure 14 Figure 9 is a perspective side view of another example of a tool holder 12e. The tool holder 12e is another example of a damper device according to the present disclosure. The tool holder 12e of this example includes a tubular element 20e and a mounting interface 76 for mounting a cutting head (not shown). The mounting interface 76 of this particular example includes threads and is formed integrally with the tubular element 20e.

[0134] Figure 15 Figure 10 is a perspective side view of the tool holder 12e in the unassembled state. The tubular element 20e is identical to the tubular element 20a except for the mounting interface 76. The tubular element 20e includes the cavity 40e, the cylindrical cavity portion 42e, the tapered cavity portion 44e defining the first surface 48e, and the edge 46e between the cylindrical cavity portion 42e and the tapered cavity portion 44e. Figure 14

[0135] ​​Similar to tool holder 12b, tool holder 12e includes a first fixed portion 26el and a second fixed portion 26e2. First fixed portion 26el is connected to second fixed portion 26e2 in front of second fixed portion 26e2. The front portions of first fixed portion 26el and second fixed portion 26e2 form a fixed interior portion 50e. Fixed interior portion 50e has the same dimensions and functionality as fixed interior portion 50b.

[0136] Second fixed portion 26e2 includes a fixed tapered portion 52e having a second surface 54e. Fixed tapered portion 52e and second surface 54e have the same design as fixed tapered portion 52b and second surface 54b, respectively.

[0137] Figure 16 A cross-sectional side view of tool holder 12e in an assembled state is shown schematically in FIG. 18. Figure 15 Similar to tool holder 12b, tool holder 12e includes a first fixed portion 26el and a second fixed portion 26e2. First fixed portion 26el is connected to second fixed portion 26e2 in front of second fixed portion 26e2. The front portions of first fixed portion 26el and second fixed portion 26e2 form a fixed interior portion 50e. Fixed interior portion 50e has the same dimensions and functionality as fixed interior portion 50b. Figure 7 Similar, tool holder 12e is assembled by inserting second unit 74e into first unit 72e to compress damping material 30 between first surface 48e and second surface 54e.

[0138] One or both of machine tools 10a and 10b can be referred to alternatively by reference numeral “10”. One, several or all of tool holders 12, 12a-12c and 12e and tool 12d can be referred to alternatively by reference numeral “12”. One, several or all of tubular elements 20a-20e can be referred to alternatively by reference numeral “20”. One, several or all of fixed portions 26a-26e can be referred to alternatively by reference numeral “26”. One, several or all of cavities 40a-40e can be referred to alternatively by reference numeral “40”. One, several or all of cylindrical cavity portions 42a-42e can be referred to alternatively by reference numeral “42”. One, several or all of tapered cavity portions 44a, 44b, 44d and 44e can be referred to alternatively by reference numeral “44”. One, several or all of first surfaces 48a-48e can be referred to alternatively by reference numeral “48”. One, several or all of fixed interior portions 50a-50e can be referred to alternatively by reference numeral “50”. One, several or all of second surfaces 54a-54e can be referred to alternatively by reference numeral “54”.

[0139] While the disclosure has been described with reference to example embodiments, it is to be understood that the application is not limited to the foregoing description. For example, it is understood that the dimensions of the components can be varied as desired. Consequently, the application is intended to be limited only by the scope of the appended claims.

Claims

1. Damper device (12) for a machine tool (10), the damper device (12) comprising: - a tubular element (20) having a cavity (40) and a central axis (18), the tubular element (20) comprising a first surface (48); - a damping mass (32) arranged within the cavity (40) and being movable radially with respect to the central axis (18) and with respect to the tubular element (20); - at least one spring element (34, 36) supporting the damping mass (32) with respect to the tubular element (20), the damping mass (32) and the at least one spring element (34, 36) being arranged to dampen vibrational kinetic energy of the damper device (12); - at least one fixing portion (26) having a second surface (54) and a fixing inner portion (50) inside the cavity (40); and - a damping material (30) arranged between the first surface (48) and the second surface (54), the damping material (30) being arranged to dampen vibrational potential energy of the damper device (12); wherein the damping material (30) is substantially uniformly compressed between the first surface (48) and the second surface (54). The first surface (48) and the second surface (54) are tapered.

2. The damper device (12) according to claim 1, wherein The first surface (48) and / or the second surface (54) have an average inclination of at least 0.2 degrees with respect to the central axis (18).

3. The damper device (12) according to claim 2, wherein The at least one fixing portion (26) is assembled by a relative movement between the tubular element (20) and the at least one fixing portion (26) along the central axis (18) such that the damping material (30) is substantially uniformly compressed between the first surface (48) and the second surface (54).

4. Damper device (12) according to claim 2 or 3, wherein The damping material (30) comprises a viscoelastic material.

5. The damper device (12) according to any one of claims 1 to 3, wherein The cavity (40) comprises a cylindrical cavity portion (42), wherein the damping mass (32) is arranged within the cylindrical cavity portion (42), and wherein at least a portion of one or more of the at least one fixing portion (26) is arranged within the cylindrical cavity portion (42).

6. The damper device (12) according to any one of claims 1 to 3, wherein The cavity (40) comprises a tapered cavity portion (44) defining the first surface (48).

7. The damper device (12) according to any one of claims 1 to 3, wherein The at least one fixing portion (26) comprises at least two fixing portions (26) fixed with respect to each other.

8. The damper device (12) according to any one of claims 1 to 3, wherein The fixing inner portion (50) comprises a fixing cylindrical portion.

9. The damper device (12) according to any one of claims 1 to 3, wherein One or more of the at least one spring element (34, 36) is connected to the fixing inner portion (50).

10. The damper device (12) according to any one of claims 1 to 3, wherein, The second surface (54) is inserted into the cavity (40).

11. Damper device (12) according to any one of claims 1 to 3, wherein The at least one fixing portion (26) comprises a mandrel.

12. The damper device (12) according to any one of claims 1 to 3, wherein The damping material (30) has a damping ratio of at least 10%.

13. The damper device (12) according to any one of claims 1 to 3, wherein The first surface (48) and the second surface (54) are conical.

14. The damper device (12) according to any one of claims 1 to 3, wherein, The first surface (48) and the second surface (54) are tapered.

15. The damper device (12) according to any one of claims 1 to 3, wherein, The first surface (48) and the second surface (54) are parallel.

16. The damper device (12) according to any one of claims 1 to 3, wherein, The damping material (30) has a thickness of less than 1 mm.

17. The damper device (12) according to any one of claims 1 to 3, wherein, The damping material (30) has a Poisson's ratio of at least 0.

35.

18. A machine tool (10) comprising a damper arrangement (12) according to any one of claims 1 to 17.

19. A method of assembling a damper arrangement (12) for a machine tool (10), the method comprising: - providing a tubular element (20) having a cavity (40) and a central axis (18), the tubular element (20) comprising a first surface (48); - providing a damping mass (32) arranged within the cavity (40) and being movable radially with respect to the central axis (18) and with respect to the tubular element (20); - providing at least one spring element (34, 36) supporting the damping mass (32) with respect to the tubular element (20), the damping mass (32) and the at least one spring element (34, 36) being arranged to attenuate vibrational kinetic energy of the damper arrangement (12); - providing at least one fixation part (26) having a second surface (54) and a fixation inner part (50) inside the cavity (40); - providing a damping material (30) between the first surface (48) and the second surface (54), the damping material (30) being arranged to attenuate vibrational potential energy of the damper arrangement (12); and - positioning the first surface (48) and the second surface (54) with respect to each other such that the damping material (30) is substantially uniformly compressed between the first surface (48) and the second surface (54).

20. The method of claim 19, wherein, The first surface (48) and the second surface (54) are tapered, and wherein the method further comprises moving the tubular element (20) and the at least one fixation part (26) with respect to each other along the central axis (18) such that the damping material (30) is substantially uniformly compressed between the first surface (48) and the second surface (54).

21. A damper arrangement (12) assembled according to the method of claim 19 or 20.

22. A machine tool (10) comprising a damper arrangement (12) according to claim 21.

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