SE1451635A1

SE1451635A1 - Cutting tool gripping tool

Info

Publication number: SE1451635A1
Application number: SE1451635A
Authority: SE
Inventors: Fumihito Sakurai; Kenji Watanabe
Original assignee: Daido Steel Co Ltd; Institute Of National Colleges Of Technology Japan
Priority date: 2012-06-29
Filing date: 2013-06-21
Publication date: 2014-12-22
Also published as: KR20150040812A; WO2014002905A1; SE1451635A2; JP5805019B2; SE538022C2; IN2014DN11026A; JP2014008572A; CN104640656A

Abstract

En skärverktygsgripare enligt uppfinningen är en skärverktygsgripare för att montera ettstavforrnat skärverktyg i en skärande maskin efter att en del av det stavformadeskärverktyget är infört i ett monteringshål och därigenom fixeras där, skärverktygsgripareninnefattar: en dämpande legeringsrörkropp som innefattar en dämpande legering med enkomponentkomposition innehållande, i terrner av massprocent, Cu: från 16,9 till 27,7 %,Ni: från 2,1 till 8,2 % och Fe: från 1,0 till 2,9 %, med C: 0,05 % eller mindre ochåterstoden är Mn och oundvikliga orenheter, och som innefattar som monteringshålet, ettgenomgående centrumhål längs en längsgående riktning av den dämpandelegeringsrörkroppen och som har en gängad yttre perifer yta; och en stel hållarrörkroppsom innefattar material med en elasticitets-modul större än den för dämpningslegeringenoch som har en gängad cylindrisk inneryta, och dämpningslegeringsrörkroppen har dengängade yttre perifera ytan gängat fixerat längs den gängade cylindriska innerytan för den stela hållarrörkroppen.

Description

15 20 25 to a cutting tool gripper, a cylindrical sleeve including a damping member is ﬁtted into a ﬁtting hole extending along the axis line of a cylindrical gripper body including a steel material, etc. and the shank part of a boring bar is inserted into the inner peripheral surface of the sleeve and pressed/fixed by a clamp screw. The outer peripheral surface portion opposite the abutting portion of the shank part on the clamp screw is arranged as a pressing face, and a damping member is interposed between the pressing surface and the opposing inner surface portion of the fitting hole to thereby damp/absorb Vibration generated in the boring bar and suppress deﬂection of the boring bar, particularly, prevent "chatter Vibration" due to resonant Vibration of the shank part and the gripper body. As the damping member usable in such a pressing face portion, aluminum, copper, zinc, brass, an alloy using such a metal as the main ingredient, a damping steel sheet, etc. are recited.

[0004] Furthermore, Patent Document 2 discloses a technique where a core member is threadably fitted along the axial center of a metal-made sleeve, a cutting tool is mounted by ﬁtting the shank thereof into a tool holding hole of the core member, and pure magnesium or a magnesium alloy, Which are lightweight and excellent in the Vibration absorptivity, can be used for the core member. The sleeve and the core member in a cutting tool gripper are formed separately so that Vibration transmitted to the mount of a cutting machine through a cutting tool gripper from a cutting tool at the time of cutting work can be absorbed by the core member.

[0005] Also, Patent Document 3 discloses a technique where a damping member is interposed between a cutting tool and a tool post to which the cutting tool is pressed and fixed, and it is stated that as the damping coefficient of the damping member is higher, Vibration at the time of cutting work can be suppressed and the impact response, for 10 15 20 25 example, in engaging the cutting tool can be reduced, but the damping performance is in a tradeoff relationship with the rigidity or strength expressed by tensile strength, etc. and an excessively high damping property rather leads to violent vibration of the cutting tool and incurs deterioration of the machining accuracy. In consideration thereof, the damping member is specified to be preferably a metal material having a tensile strength of 500 to 650 MPa and a logarithmic damping factor of 0.2 to 0.35, for example, a Mn- based damping alloy having a ﬁindamental composition of, in terms of atm%, Cu: 20i5%, Ni: 5i3% and Fe: 2i1%.

BACKGROUND ART DOCUMENT PATENT DOCUMENT

[0006] Patent Document 1: JP-UM-A-05-088804 Patent Document 2: Japanese Utility Model Registration No. 3,l53,247 Patent Document 3: JP-A-2004-202649 SUMMARY OF THE INVENTION PROBLEMS THAT THE INVENTION IS TO SOLVE

[0007] As disclosed in Patent Documents l to 3, it is Widely practiced to interpose a damping member between a cutting tool and a portion to Which the cutting tool is pressed and ﬁxed. The damping properties of the damping member greatly differ depending on the material thereof, nevertheless, studies have not been made on the design of a cutting tool gripper, etc. optimized for each material of the damping In other Words, it has not been necessarily true that vibration of a cutting tool member. is maximally suppressed to afford cutting Work With high machining accuracy. 10 15 20 25

[0008] The present invention has been made under these circumstances, and an object of the present invention is to provide a cutting tool gripper enabling cutting Work With excellent machining accuracy.

MEAN S FOR SOLVING THE PROBLEMS

[0009] A cutting tool gripper of the present invention is a cutting tool gripper for mounting a bar-shaped cutting tool in a cutting machine after one end part of the bar- shaped cutting tool is inserted into a mounting hole thereby being fixed, in Which the cutting tool gripper includes: a damping alloy tube body Which includes a damping alloy having a component composition containing, in terms of mass%, Cu: from 16.9 to 27.7%, Ni: from 2.1 to 82% and Fe: from 1.0 to 2.9%, With C: 0.05% or less and the remainder being Mn and unavoidable impurities, and Which affords, as the mounting hole, a center through hole along a longitudinal direction of the damping alloy tube body and has a threaded outer peripheral surface; and a rigid holding tube body Which includes a material having a Young's modulus larger than the damping alloy and has a threaded cylindrical inner surface, and the damping alloy tube body having the threaded outer peripheral surface is threadably fixed along the threaded cylindrical inner surface of the rigid holding tube body.

[0010] According to the invention in this aspect, the damping alloy tube body including an Mn-based twinned damping alloy having relatively high rigidity and strength and at the same time, having a high damping ability of efﬁciently absorbing vibration at a Wide frequency range is threadably fixed With a Wide area along the cylindrical inner surface of the rigid holding tube body, Whereby the cutting Work 10 15 20 25 performed by mounting a cutting tool in such a cutting tool gripper can afford excellent machining accuracy. [001 1] In the invention described above, the damping alloy tube body may be threadably fixed along the cylindrical inner surface while inserting an end part of the damping alloy tube body into the rigid holding tube body so that a ﬂange part provided in the opposite end part of the damping alloy tube body in the longitudinal direction is pressed against an end face of the rigid holding tube body. According to the invention in this aspect, the damping alloy tube body including an Mn-based twinned damping alloy having relatively high rigidity and strength is threadably ﬁxed more ﬁrmly with a wide area along the cylindrical inner surface of the rigid holding tube body, Whereby the cutting work performed by mounting a cutting tool in such a cutting tool gripper can afford more excellent machining accuracy.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] [Fig. 1] Fig. 1 is a lateral cross-sectional view and a front view showing the cutting tool gripper according to the present invention.

[Fig. 2] Fig. 2 is a lateral cross-sectional view and a front view showing a component part of the cutting tool gripper according to the present invention.

[Fig. 3] Fig. 3 is a lateral cross-sectional view and a front view showing a component part of the cutting tool gripper according to the present invention.

[Fig. 4] Fig. 4 is a lateral cross-sectional view showing a method for ﬁxing a cutting tool by the cutting tool gripper according to the present invention.

[Fig. 5] Fig. 5 is a view showing the measurement results of the roundness in the cutting work. 10 15 20 25 [Fig. 6] Fig. 6 is a view showing the measurement results of the surface roughness in the cutting Work.

[Fig. 7] Fig. 7 is a lateral cross-sectional view showing a method for fixing a cutting tool by the cutting tool gripper in another embodiment according to the present invention.

MODE FOR CARRYING OUT THE INVENTION

[0013] The cutting tool gripper as one embodiment of the present invention is described by referring to Figs. 1 to 4.

[0014] As shown in Fig. 1, the gripper 1 for gripping a cutting tool and mounting the cutting tool in a cutting machine is fabricated by concentrically combining a nearly cylindrical holding tube body including a rigid material (rigid holding tube body) 2 and a nearly cylindrical sleeve including a damping alloy (damping alloy tube body) 3.

The holding tube body 2 has a ﬂange 21 at one end part thereoﬁ the sleeve 3 is inserted from an end part opposite to the ﬂange 21, and a side surface of a ﬂange part 31 provided in one end part of the sleeve 3 is abutted on an end face 24 of the holding tube body 2.

[0015] Referring to Fig. 2 in combination, the inner peripheral surface 22 of the holding tube body 2 is provided With an intemal thread along the axis line over the entire length. Also, the holding tube body 2 is provided With a through hole 23 penetrating to the inner peripheral surface 22 from the outer peripheral surface, into Which a bolt for fixing a cutting tool is fitted as described later. A plurality of through holes 23 are provided along the axis line direction. The holding tube body 2 is a rigid 10 15 20 25 body including, for example, a steel such as S45C and having at least a Young's modulus larger than the sleeve 3 described later, and typically, it is preferable to have a Young's modulus as large as two times or more that of the sleeve 3.

[0016] As shown in Fig. 3, the outer peripheral surface 32 except for the ﬂange part 31 of the sleeve 3 is provided With an external thread along the axis line direction and can be threaded to correspond to the above-described internal thread on the inner peripheral surface 22 of the holding tube body 2. The inner peripheral surface of the tube-shaped sleeve 3 defines a mounting hole 34 for the insertion and mounting of a cutting tool.

The sleeve 3 is provided with a plurality of through holes 33 corresponding to through holes 23 of the holding tube body 2 and penetrating in the radial direction from the outer peripheral surface 32 to the inner peripheral surface. That is, each through hole 33 is provided at the position allowing for communication with the through hole 23 when the sleeve 3 is threadably fixed to the holding tube body 2 (see, Fig. 1).

[0017] The sleeve 3 includes a twinned Mn-based damping alloy that is a Mn-Cu-Ni- Fe-based damping alloy having a component composition containing, in terms of mass%, Cu: from 16.9 to 27.7%, Ni: from 2.1 to 82% and Fe: from 1.0 to 2.9%, with C: 0.05% or less and the remainder being Mn and unavoidable impurities (low content elements such as O and N). The composition range of each component (all in terms of mass%) is described below. If the amount of Cu is less than l6.9%, a twinned crystal is not generated, whereas if the amount thereof exceeds 27.7%, segregation is increased, resulting in failure to obtain sufficient damping properties. The amount of Cu is preferably from 19.7 to 25.0%. Ni is added as a third element together with main If the elements Mn and Cu, thereby being able to enhance the damping properties. amount of Ni is less than 2.1%, the element cannot contribute to change for twinned 10 15 20 25 crystal generation, Whereas if the amount thereof exceeds 8.2%, the contribution to the twinned crystal generation is saturated. Fe is added as a fourth element together With Mn and Cu or together With Ni, thereby being able to more enhance the damping properties. If the amount of Fe is less than 1.0%, the element cannot contribute to change for twinned crystal generation, Whereas if the amount thereof exceeds 2.9%, the contribution to the twinned crystal generation is saturated. The amount of C is set to be 0,05% or less, Whereby the damping properties can be prevented from deterioration even When Mn is evaporated and the relative concentration of C is raised.

[0018] As described above, the damping alloy in this embodiment forms a twinned crystal and absorbs vibration by converting an extemally imposed vibration energy to a frictional heat at the twinned crystal interface. This damping alloy has a high damping ability for vibration in a Wide frequency range and can efñciently absorb vibration, compared With a general damping alloy. Particularly, due to loading of compression stress, frictional heat is produced at the twinned crystal interface even With a smaller stress, and vibration can be efficiently absorbed. Furthermore, the damping alloy has high rigidity and strength, compared With a general damping alloy.

[0019] Again referring to Fig. 1, the inner peripheral surface 22 of the holding tube body 2 and the outer peripheral surface 32 of the sleeve 3 are screwed to each other and fixed With a large area, compared With a case of intemally ﬁtting smooth surfaces to each other. Furthermore, the sleeve 3 is screwed While pressing a side surface of the ﬂange part 31 thereof against the end face 24 of the holding tube body 2 as a rigid body having a larger Young's modulus, thereby applying a larger surface pressure to the outer peripheral surface 32 having faces that are inclined from the axis line direction by threading, as a result, the sleeve 3 is more firmly fixed to the holding tube body 2. 10 15 20 25

[0020] As shown in Fig. 4, the above-described gripper 1 is inserted into a holding hole 64 of a holder 60 fixed to a cutting machine (not shown) after inserting a grasp part 52 of a bar-shaped cutting tool 50 into the mounting hole 34. At this time, the side surface of the ﬂange 21 is abutted on the holder 60, and a chip 51 of the cutting tool 50 is protruded from the holder 60. In this state, a bolt hole 63 having an intemal thread, provided on the holder 60, is arranged at the position communicating With the through hole 23, 33 of the gripper 1 and a plurality of bolts 4 are fastened through the bolt holes 63, as a result, the distal end of the bolt 4 is abutted against the cutting tool 50. The cutting tool 50 is pressed in the travelling direction of the bolt 4, and the outer peripheral surface opposite to the abutting portion of the cutting tool 50 on the bolt 4 is pressed against the inner peripheral surface of the sleeve 3, thereby being fixed. As a result, the cutting Work can be performed While moving the chip 51 relative to a Workpiece.

[0021] According to the above-described embodiment, the sleeve 3 including a tWinned Mn-based damping alloy is threadably ﬁxed to the inner peripheral surface of the highly rigid holding tube body 2 With a large area, compared With a case of internally ﬁtting smooth surfaces to each other. Thereafter, a plurality of bolts 4 are fastened, Whereby the outer peripheral surface of the cutting tool 50, opposite to the portion abutted by the bolt 4, is pressed and ﬁxed to the inner peripheral surface of the sleeve 3. That is, the sleeve 3 fixes the cutting tool 50 while being, due to its rigidity, biased and compressed against the holding tube body 2 With a larger area covering the entire region in the axial direction and at the same time, over a Wide range in the circumferential direction.

As a result, by utilizing the characteristics of the above- described tWinned Mn-based damping alloy having higher vibration damping ability 10 15 20 25 under compression stress, a gripper 1 that can efficiently absorb vibration in a Wide frequency range and has high damping ability, is provided, in other Words, excellent machining accuracy is afforded.

[0022] Incidentally, the sleeve 3 is screwed inside the holding tube body 2 While pressing the side surface of ﬂange part 31 thereof to the end face 24 of the holding tube body 2 including a rigid body having a larger Young's modulus, Whereby the force exerted in the screw travelling direction by the sleeve 3 and the force exerted thereagainst by the ﬂange part 31 of the sleeve 3 are applied to the threaded outer peripheral surface 32 of the sleeve 3, i.e., the outer peripheral surface 32 having threaded faces that are a face inclined relative to the axis line direction, Whereby the sleeve 3 can be more ﬁrmly fixed to the holding tube body 2. In other Words, the vibration generated in the cutting tool 50 can be more efficiently absorbed.

[0023] [Evaluation Test] The results of the cutting Work (boring Work) using the cutting tool gripper in each of Example and Comparative Examples of the present invention are illustrated below by referring to Figs. 5 and 6. The results of the cutting Work Were evaluated by measuring the roundness and surface roughness as described later.

[0024] Example 1 is a cutting tool gripper (hereinafter referred to as "screw type") obtained by screwing together a sleeve 3 composed of an Mn-Cu-Ni-Fe-based damping alloy having a component composition of, in terrns of mass%, Cu: 22.4%, Ni: 5.2%, Fe: 2.0% and C: 0.01%, With the remainder being Mn and unavoidable impurities, and a holding tube body 2 composed of S45C. More specifically, the holding tube body 2 has an outer diameter of 40 mm, Where an internal thread of M33><2 is formed on the 10 10 15 20 25 inner peripheral surface thereof over the entire length. The sleeve 3 has an inner diameter of 25.2 mm, Where an external thread of M33><2 is formed on the outer peripheral surface thereof. The total length of the cutting tool gripper obtained by screW-ﬁxing these members, that is, the total length of the sleeve 3, is 96 mm.

[0025] Comparative Example l is a cutting tool gripper (hereinafter, referred to as "fitting type") obtained by, unlike Example l, fixing a cylindrical sleeve to a holding tube body by cold fitting, Without screwing together a sleeve 3 and a holding tube body 2. Here, the boundary diameter is 3l mm, and other dimensions are the same as in Example 1. Comparative Examples 2 and 3 are cutting tool grippers (hereinaﬁer, referred to as "integral type") obtained by integrally forming a holding tube body and a sleeve. The materials of Comparative Examples 2 and 3 are respectively S45C used for the holding tube body 2 of Example l and the Mn-Cu-Ni-Fe-based damping alloy used for the sleeve 3 of Example l.

[0026] As for the cutting work, boring Work for a feed distance of 80 mm Was performed in 3 passes on a Workpiece that is a cylindrical body composed of SUS304 and having a length of 200 mm, an outer diameter of 100 mm and an inner diameter of 62 mm, under the conditions of a cutting speed of l00 rn/min, a cutting amount of 0.5 mm, a feed rate of 0.2 mm/rev and a tool protrusion amount of 140 mm.

[0027] The roundness Was measured on the inner peripheral surface of a machined hole aﬁer 3 passes of boring Work by using a commercially available three-dimensional meter. In the measurement, the roundness Was measured in 4 portions at a depth of 3 mm, 6 mm, 25 mm and 45 mm from the end face of the machined hole, and for comprehensive evaluation of each case, the average value of measured values of 4 ll 10 15 20 25 portions was recorded. The average value of each case is shown in the lower part of Fig. 5.

[0028] The surface roughness was measured at 3 points by a commercially available surface roughness meter in a portion at a depth of 30 mm from the end face of the inner peripheral surface of the Workpiece every time the boring Work was performed for 1 pass, and the average value thereof was deterrnined. The boring work was performed in 3 passes, and the average value of the surface roughness Ra in every pass was recorded.

[0029] As shown in Figs. 5 and 6, in Example 1 of "screw type", the roundness was from 6.3 to 8.7 um and 7.4 um on average, and the surface roughness Ra was from 1.69 to 1.93 um. The surface roughness Ra showed a stable value even when the number of passes was increased.

[0030] On the other hand, in Comparative Example 1 of "ﬁtting type", the roundness Was from 11.9 to 21.4 um and 16.3 um on average and Was larger than in Example 1.

The surface roughness Ra was from 2.42 to 5.01 um and was also large compared with Example 1. That is, in terms of the machining accuracy evaluated by the roundness and surface roughness Ra, Example 1 was superior to Comparative Example 1.

[0031] In Comparative Example 2 of "integral type" composed of S45C, the roundness was from 9.2 to 10.1 um and 9.7 um on average and was larger than in Example 1.

Also, the surface roughness Ra was from 3.99 to 5.35 um and was larger than in Example 1.

That is, in terms of the machining accuracy evaluated by the roundness and surface roughness Ra, Example 1 was superior to Comparative Example 2. In 12 10 15 20 25 Comparative Example 2, it is considered that although the amplitude of vibration generated in the cutting tool Was relatively small and the roundness Was relatively high, the vibration generated could not be absorbed and the surface roughness Was increased.

[0032] In Comparative Example 3 of "integral type" composed of an Mn-Cu-Ni-Fe- based damping alloy having the same component composition as in Example 1, the roundness Was from 15.0 to 25.3 um and 18.4 um on average and Was larger than in Example 1. Also, the surface roughness Ra Was from 6.54 to 9.19 um and Was larger than in Example 1. That is, in terms of the machining accuracy evaluated by the roundness and surface roughness Ra, Example 1 Was superior to Comparative Example 3. It is considered that since the damping alloy Was applied to a large thickness compared With the screw type (Example 1) or the fitting type (Comparative Example 1), tWinned crystal deformation became insufficient and the vibration could not be efficiently converted to frictional heat, failing in obtaining good damping performance.

[0033] As described above, in the boring Work using the cutting tool gripper of Example 1, the machining accuracy evaluated by the roundness and surface roughness Was very excellent. This gripper 1 can achieve such high machining accuracy by threadably fixing a sleeve 3 using a tWinned Mn-based damping alloy that has high rigidity and strength compared With a general damping alloy and at the same time, can efficiently absorb vibration in a Wide frequency range particularly under compression stress, to a highly rigid holding tube body 2.

[0034] Also, as shown in Fig. 7, a continuous internal thread may be imparted to inner peripheral surfaces of a through hole 23 of the holding tube body 2 and a through hole 33 of the sleeve 3, and a setscrew 42 may be fastened thereto to abut its distal end on 13 10 15 20 the cutting tool 50 so that the cutting tool 50 can be pressed and fixed to the inner peripheral surface of the sleeve 3. At this time, the setscrew 42 does not protrude from the outer peripheral surface of the holding tube body 2 and does not come into contact With the holder 60. Incidentally, the holding tube body 2 is pressed and fixed to the holder 60 by a bolt (not shown). The setscrew 42 does not come into contact With the holder 60, so that vibration generated in the cutting tool 50 can be prevented from transmitting outside of the cutting tool gripper l. As another example, a shorter setscrew 42 may be used not to protrude from the outer peripheral surface of the sleeve 3. That is, by keeping the setscrew 42 from contacting not only With the holder 60 but also With the holding tube body 2, vibration generated in the cutting tool 50 can be prevented from being mediated by the sleeve 3 and transmitted outside.

[0035] While the present invention has been described above With reference to representative Examples thereof, the present invention is not necessarily limited thereto.

One skilled in the art Would be able to find Various alternative Examples and modiﬁcations Without departing from the gist of the present invention or the scope of patent claims attached.

[0036] This application is based on Japanese Patent Application (Patent Application No. 2012-146856) filed on June 29, 2012, the entirety of Which is incorporated herein by reference.

INDUSTRIAL APPLICABILITY [003 7] l4 According to the cutting tool gripper of the present invention, excellent machining accuracy is achieved in the cutting Work performed by rnounting a cutting tool in such a cutting tool gripper.

DESCRIPTION OF REFERENCE NUMERALS AND SIGNS [003 8] l Gripper 2 Holding tube body 3 Sleeve 22 Inner peripheral surface 31 Flange part 32 Outer peripheral surface 34 Mounting hole 50 Cutting tool 15

Claims

1. [Claim 1] A cutting tool gripper for mounting a bar-shaped cutting tool in a cutting machine after one end part of the bar-shaped cutting tool is inserted into a mounting hole thereby being fixed, Wherein the cutting tool gripper comprises: a damping alloy tube body Which comprises a damping alloy having a component composition containing, in terms of mass%, Cu: from 16.9 to 27.7%, Ni: from 2.1 to 82% and Fe: from 1.0 to 2.9%, With C: 0.05% or less and the remainder being Mn and unavoidable impurities, and Which affords, as the mounting hole, a center through hole along a longitudinal direction of the damping alloy tube body and has a threaded outer peripheral surface; and a rigid holding tube body Which comprises a material having a Young's modulus larger than the damping alloy and has a threaded cylindrical inner surface, and the damping alloy tube body having the threaded outer peripheral surface is threadably fixed along the threaded cylindrical inner surface of the rigid holding tube body.

2. [Claim 2] The cutting tool gripper according to claim l, Wherein the damping alloy tube body is threadably fixed along the cylindrical inner surface While inserting an end part of the damping alloy tube body into the rigid holding tube body so that a ﬂange part provided in the opposite end part of the damping alloy tube body in the longitudinal direction is pressed against an end face of the rigid holding tube body. 16