JP7496970B2 - Machining Tools - Google Patents

Description

The present invention relates to a machining tool such as a boring bar used to cut the inner surface of a cylindrical object.

For example, when cutting the inner circumferential surface of a cylindrical object, a boring bar is used as a processing tool. This boring bar has a mounting support part that is attached to the tool mounting part of a processing device such as an NC lathe, a shank part that extends from the mounting support part, and a cutting blade mounting part provided at the tip of the shank part, and a processing tip is attached to the cutting blade mounting part. When such a boring bar is used, since the shank part protrudes from the mounting support part, it is possible to insert the processing tip all the way to the inside of the cylindrical object, and therefore the inner circumferential surface of the cylindrical object can be cut by the processing tip.

However, when machining using such a boring bar, chatter vibrations (self-excited vibration phenomenon) are likely to occur due to the cutting resistance during cutting, and when machining the inner surface of a long, thin cylindrical object in particular, the shank portion of the machining tool also becomes long and thin, making chatter vibrations more likely to occur.

A boring bar with a structure designed to suppress this chatter vibration has been proposed (see, for example, Patent Document 1). In this boring bar, a pair of first recessed surfaces is provided on the base side of the shank, and a second recessed surface is provided on the tip side thereof, with the pair of first recessed surfaces arranged back to back facing each other in the first axial direction, and the pair of second recessed surfaces arranged back to back facing each other in the second axial direction. When an axis passing through the radial outer end of the cutting edge and the central axis of the shank is taken as a reference axis, the first axis is an axis that passes through the central axis of the shank and extends at a predetermined inclination angle with this reference axis, and the second axis is an axis that passes through the central axis of the shank and extends perpendicular to the first axis.

JP 2018-167347 A

However, even with this boring bar, because the shank portion has a solid structure, there is a problem in that it is difficult to effectively suppress the chatter vibration that occurs during machining. In other words, in order to suppress this chatter vibration, it is necessary to reduce the vibration amplitude in the thrust force direction of the machining resistance (cutting resistance) that occurs during machining (e.g., during cutting), reduce the fluctuation of the machining resistance, and suppress the amplification of this vibration amplitude, and with a solid structure, it is not easy to manufacture a boring bar that meets these conditions.

This type of chatter vibration problem can occur not only with boring bars, but also with other machining tools.

The object of the present invention is to provide a machining tool that reduces the vibration amplitude in the thrust direction of the machining resistance, thereby reducing the fluctuation of the machining resistance and thereby suppressing the occurrence of chatter vibration.

The machining tool of the present invention is a machining tool including a tool body having a mounting support part attached to a tool mounting part of a machining device, a shank part extending from the mounting support part, and a cutting blade mounting part provided at a tip part of the shank part, and a machining tip attached to the cutting blade mounting part of the tool body,
the shank portion is composed of a solid structure portion which is a solid structure, a lattice structure portion which is a lattice structure, and a hollow structure portion which is a hollow space, and the volume of the lattice structure portion of the shank portion is 20 to 40% of the total volume of the solid structure portion and the lattice structure portion of the shank portion,
Furthermore, in the front part on the cutting edge mounting side with respect to the axial center of the shank portion, the volume of the solid part is 20 to 40%, the volume of the lattice structure part is 25 to 45%, and the volume of the hollow structure part is 25 to 45% .

In such a machining tool, it is preferable that the weight of the front part of the shank of the machining tool is 60% or less of the weight of the rear part of the shank. By configuring it in this manner, the weight of the front part of the shank is reduced, and the dynamic rigidity of the shank portion can be increased.

The volume of the lattice structure at the front of the shank is preferably 40% or more of the combined volume of the solid structure and lattice structure at the front of the shank, and the proportion of the volume of the lattice structure at this front of the shank increases gradually toward the cutting edge attachment section. By configuring the shank in this way, the weight of the front of the shank becomes lighter toward the cutting edge attachment section, and the dynamic rigidity of the shank can be increased.

Furthermore, in this machining tool, when the shank portion is viewed from the cutting blade attachment side and divided into four portions counterclockwise around the central axis of the front portion of the shank with the cutting direction as the reference, into first to fourth regions, it is preferable that the volume of the lattice structure portion is the largest in the first region, the volume of the hollow structure portion is the largest in the second region, the volume of the solid structure portion is the largest in the third region, and the volume of the lattice structure portion is the largest in the fourth region, and further that the volume of the solid structure portion is 20-40% in the first region, and the volume of the lattice structure portion is 20-40% in the first region. In the first region, the volume of the solid structure is 30-50%, in the second region, the volume of the solid structure is 0-20% and the volume of the lattice structure is 10-30%, in the third region, the volume of the solid structure is 40-60% and the volume of the lattice structure is 30-50%, and in the fourth region, the volume of the solid structure is 20-40% and the volume of the lattice structure is 30-50%, and by configuring in this way, it is possible to provide a product that has sufficient strength against processing resistance (its main force, thrust force, and feed force).

Furthermore, it is preferable that the boundary surface between the solid structure and the lattice structure in the shank portion has a free-form surface shape . By configuring in this manner, the solid structure and the lattice structure can be optimally arranged. Furthermore, the shape including the solid structure, lattice structure and hollow structure in the shank portion is derived using topology optimization analysis, and by minimizing the amplitude in the cutting direction in the vibration mode of the machining tool that excites chatter vibration in the topology optimization analysis, it is possible to provide a machining tool that generates less chatter vibration.

Furthermore, each lattice structure of the lattice structure part of the shank part preferably has a solid occupancy rate of 30 to 70% and a lattice spacing of 0.5 to 5.0 mm. By adopting such a lattice structure, the strength of the shank part can be maintained. Also, by making the lattice structure part of the shank part a part of the liquid flow path, it can be used as a flow path for processing fluid, etc., without having to provide a dedicated flow path for the processing fluid.

According to the machining tool of the present invention, the shank portion of the machining tool is composed of a solid structure portion, a lattice structure portion, and a hollow structure portion, and the volume of the lattice structure portion of the shank portion is 20 to 40% of the total volume of the solid structure portion and the lattice structure portion of the shank portion, so that the solid portion can be made lighter while maintaining its strength, thereby increasing the dynamic rigidity of the shank portion and, as a result, suppressing the occurrence of chatter vibration during machining. If the lattice structure portion exceeds 40%, there is a risk of a decrease in strength, and if it is 20% or less, the mass cannot be reduced sufficiently, and as a result, the dynamic rigidity cannot be increased.
Furthermore, in the front part on the cutting edge attachment side with respect to the axial center of the shank portion, the volume of the solid part is 20 to 40%, the volume of the lattice structure part is 25 to 45%, and the volume of the hollow structure part is 25 to 45%, so that it is possible to maintain sufficient strength against machining resistance while achieving weight reduction.

FIG. 2 is a diagram showing a state in which a machining tool according to the present invention is attached to an NC lathe. FIG. 2 is a plan view showing the machining tool of FIG. 1 . FIG. 3 is a vertical end view showing the machining tool of FIG. 2 . 4(a) is an end view of the shank portion taken along line A-A in FIG. 3, FIG. 4(b) is an end view of the shank portion taken along line B-B in FIG. 3, and FIG. 4(c) is an end view of the shank portion taken along line CC in FIG. 5(a) is an end view at protruding position P1 of the shank portion, FIG. 5(b) is an end view at protruding position P2 of the shank portion, and FIG. 5(c) is an end view at protruding position P3 of the shank portion. 13 is a diagram showing the relationship between the protruding position of the shank portion and the volume ratio of the lattice structure portion. FIG. 4 is a diagram for explaining first to fourth regions in the shank portion. FIG. 13 is a diagram showing the ratio of solid structure portions, lattice structure portions, and hollow structure portions in the first to fourth regions. FIG. 4 is a diagram for explaining the amplitude in the cutting direction in the shank portion. FIG. 2 is a perspective view showing one lattice structure in the lattice structure portion of the shank portion. FIG. 13 is a diagram for explaining optimization of a shank portion of a machining tool. 12(a) shows the chatter vibrations that occurred in the machining experiment of the embodiment, where FIG. 12(a) shows the vibrations when L = 54 mm, FIG. 12(b) shows the vibrations when L = 60 mm, FIG. 12(c) shows the vibrations when L = 66 mm, and FIG. 12(d) shows the vibrations when L = 72 mm. 13(a) shows the magnitude of chatter vibrations that occurred in the machining experiment of Comparative Example 1, with FIG. 13(a) showing the vibrations when L = 36 mm, FIG. 13(b) showing the vibrations when L = 42 mm, FIG. 13(c) showing the vibrations when L = 48 mm, and FIG. 13(d) showing the vibrations when L = 52 mm. 14A shows the magnitude of chatter vibrations that occurred in the machining experiment of Comparative Example 2, with FIG. 14A showing the vibrations when L = 54 mm, FIG. 14B showing the vibrations when L = 60 mm, and FIG. 14C showing the vibrations when L = 66 mm. 1 is a diagram showing the L/D of a machining tool and the RMS value of acceleration during machining in machining experiments of an embodiment and comparative examples 1 and 2. FIG. Graph summarizing the results of processing experiments of the Example and Comparative Examples 1 and 2.

One embodiment of a machining tool according to the present invention will be described below with reference to the attached drawings. Note that in this embodiment, the machining tool will be described as a boring bar used for machining the inner surface of a cylindrical object (so-called boring processing), but the present invention can be similarly applied to machining tools other than boring bars.

In Figure 1, the NC lathe shown as an example of a processing device has a lathe body 2, and a spindle section 4 is provided at one end side (left side in Figure 1) of this lathe body 2. A spindle (not shown) is rotatably supported by this spindle section 4, and a chuck means 6 is attached to this spindle, and a workpiece (not shown) to be processed is detachably attached to this chuck means 6.

At the other end of the lathe body 2, a reciprocating table 12 is arranged so as to be movable in the Z-axis direction (left and right direction in FIG. 1), and a support table 14 is attached to the reciprocating table 12 so as to be movable in the X-axis direction (direction perpendicular to the paper surface in FIG. 1), and a turret 16 is attached to the support table 14. The turret 16 includes a support base 18 attached to the support table 14, and a turret body 20 supported by the support base 18 so as to be rotatable at a predetermined rotation angle. The turret body 20 is polygonal (e.g., octagonal), and a tool attachment portion 22 is provided corresponding to each face of the polygonal shape of the turret body 20. In this embodiment, a machining tool 26 (one embodiment of a machining tool according to the present invention) is attached to one of the tool attachment portions 22 via a tool holder 24.

Next, one embodiment of the machining tool 26 will be described with reference to Figures 2 to 8. The illustrated machining tool 26 is used when cutting the inner surface of a cylindrical object (not shown) as a workpiece. For example, when machining using the NC lathe of Figure 1, the cylindrical object is attached to the chuck means 6, and the machining tool 26 is attached to the tool attachment portion 22 of the turret 16 via the tool holder 24, and the machining tool 26 is applied to the inner surface of the workpiece (cylindrical object) rotating in a predetermined direction to perform cutting (so-called boring).

This machining tool 26 (also referred to as a "boring bar" in this embodiment) has a rod-shaped tool body 28, which has an attachment support portion 30 (region indicated by reference number 31), a shank portion 32 (region indicated by reference number 33) extending from the attachment support portion 30, and a cutting edge attachment portion 34 (region indicated by reference number 35) provided at the tip of the shank portion 32.

The mounting support part 30 is attached to, for example, a tool holder 24 (see FIG. 1) attached to the tool mounting part 22 of the turret 16, and this mounting support part 30 is constructed with a solid structure to ensure sufficient strength. This mounting support part 30 is formed with an outer shape that is approximately cylindrical.

The shank portion 32 is composed of a solid structure, a lattice structure, and a hollow structure, and by using such a structure, it is possible to reduce the frequency response of the vibration amplitude generated during processing. The shank portion 32 is also formed into an approximately cylindrical shape whose outer shape continues from the mounting support portion 30.

The cutting blade mounting part 34, like the mounting support part 30, is constructed from a solid structure and is provided with a mounting surface 38 that extends flat at a predetermined angle to the cutting direction during machining (the direction indicated by the arrow 36). A machining tip 40 (e.g., a cutting tip) is attached to this mounting surface 38 by a mounting screw (not shown) or the like, and machining of the workpiece is performed by the machining tip 40 attached to this tool body 28.

Next, the configuration of the shank portion 32 of the machining tool 26 will be described. In the shank portion 32, as can be seen from FIG. 3 and FIG. 4, the volume of the lattice structure portion 42 (part with a lattice structure) is set to be 15-85% of the total volume of the lattice structure portion 42 and the solid structure portion 44 (part with a solid structure), and the volume ratio of the lattice structure portion 42 is preferably 20-40%. If the volume of the lattice structure portion 42 is small (for example, less than 15% of the total volume), the effect of weight reduction due to the adoption of the lattice structure is small, and if the volume of the lattice structure portion 42 is large (for example, more than 85% of the total volume), the proportion of the lattice structure portion 42 will be large, and the strength of the shank portion 32 may be reduced. Reference numeral 46 denotes a hollow structure portion (part with a hollow structure).

In this shank portion 32, the weight of the shank front portion 50 (region indicated by reference number 51) on the cutting blade mounting portion 34 side, based on the center (i.e., axial centerline E) in the axial direction (left-right direction in Figs. 2 and 4, direction perpendicular to the paper surface in Fig. 3), is preferably 60% or less of the weight of the shank rear portion 52 (region indicated by reference number 53) on the mounting support portion 30 side, and is preferably 40 to 60%, for example. By configuring it in this way, the weight of the shank front portion 50 is about 40% lighter than the weight of the shank rear portion 52, and this weight reduction increases the dynamic rigidity of the shank portion 32 and suppresses the occurrence of chatter vibrations.

As can be seen from Figures 3 to 6, the volume of the lattice structure 42 in the shank front 50 is preferably 40% or more of the total volume of the solid structure 44 and the lattice structure 42 in the shank front 50, for example 40% to 70%. By configuring the shank front 50 in this way, it is possible to reduce its weight while maintaining its strength.

Figure 4(a) is an end view of the shank portion 32 taken along line A-A in Figure 3, Figure 4(b) is an end view of the shank portion 32 taken along line B-B in Figure 3, and Figure 4(c) is an end view of the shank portion 32 taken along line C-C in Figure 3. As can be seen from Figures 4(a) to (c), the lattice structure portion 42 is more provided on the front end side of the shank front portion 50 of the shank portion 32. Note that, based on the cutting direction indicated by the arrow 36, the end face of the shank portion 32 taken along line A-A in Figure 4(a) is at an angle of 36 degrees counterclockwise in Figure 3, the end face of the shank portion 32 taken along line B-B in Figure 4(b) is at an angle of 81 degrees counterclockwise in Figure 3, and the end face of the shank portion 32 taken along line C-C in Figure 4(c) is at an angle of 126 degrees counterclockwise in Figure 3.

As can be seen from Figures 4 and 5, in the shank front portion 50 of the shank portion 32, it is preferable to configure the proportion of the lattice structure portion 42 in the total volume of the solid structure portion 44 and the lattice structure portion 42 so that it gradually increases toward the cutting edge attachment portion 34 side (i.e., the tip side). By configuring it in this way, it is possible to reduce the weight of the shank front portion 50 while suppressing a decrease in strength.

In this embodiment, FIG. 5(a) is an end view of a portion P1 that is 0.6 times the protruding position of the shank portion 32 (in other words, 1/5 of the shank front portion 50), FIG. 5(b) is an end view of a portion P2 that is 0.75 times the protruding position of the shank portion 32 (in other words, 1/2 of the shank front portion 50), and FIG. 5(c) is an end view of a portion P3 that is 0.9 times the protruding position of the shank portion 32 (in other words, 4/5 of the shank front portion 50). In portion P3, the proportion of the spatial structure portion 46, which is an intermediate structure (spatial structure), is large, resulting in a large internal space.

Figure 6 shows the protruding position of the shank 32 at the shank front 50 of the shank 32 of this machining tool 26 and the volume ratio of the lattice structure 42 (the volume ratio of the lattice structure 42 to the total volume of the solid structure 44 and the lattice structure 42). At the base of the shank front 50 (e.g., a portion 0.55 times the protruding position of the shank 32), the volume ratio of the lattice structure 42 is about 30%, but at the tip side (e.g., a portion 0.95 times the protruding position), this volume ratio increases to about 80%, and this increase in volume ratio is configured to gradually increase toward the tip side (i.e., the cutting edge attachment portion 34 side).

In this machining tool 26, it is preferable to further configure the shank front portion 50 as follows: With reference to Figures 7 and 8, when the shank portion 32 is viewed from the cutting blade attachment portion 34 side, the shank front portion 50 is divided into four portions counterclockwise with respect to the cutting direction about its central axis O, with the range of 0 to 90 degrees being the first region Z1, the range of 90 to 180 degrees being the second region Z2, the range of 180 to 270 degrees being the third region Z3, and the range of 270 to 360 degrees being the fourth region Z4. When the first to fourth regions Z1 to Z4 are defined in this manner, it is preferable to configure the first region Z1 so that the lattice structure portion 42 has the largest volume, the second region Z2 so that the hollow structure portion 46 has the largest volume, the third region Z3 so that the solid structure portion 44 has the largest volume, and the fourth region Z4 so that the lattice structure portion 42 has the largest volume. By configuring in this way, it is possible to achieve a structure that has sufficient strength against machining resistance (the main force, thrust force, and feed force) while achieving weight reduction.

In addition, in the shank front portion 50 of the shank portion 32, the volume ratios of the solid structure portion 44, the lattice structure portion 42, and the hollow structure portion 46 are preferably configured to have the distribution ratios shown in FIG. 8. That is, in the first region Z1, with respect to the above-mentioned four divided first to fourth regions Z1 to Z4, it is preferable to configure the volume of the solid structure portion 44 to be 20 to 40%, the volume of the lattice structure portion 42 to be 30 to 50%, and the proportion of the lattice structure portion 42 to be greater, and in the second region Z2, the volume of the solid structure portion 44 is 0 to 20%, the volume of the lattice structure portion 42 is 10 to 30%, and the proportion of the lattice structure portion 42 is greater, but it is preferable to configure the proportion of the hollow structure portion 46 to be even greater than the proportion of the lattice structure portion 42.

In the third region Z3, it is preferable to configure the volume of the solid structure portion 44 to be 40-60% and the volume of the lattice structure portion 42 to be 30-50%, so that the proportion of the solid structure portion 44 is greater, and furthermore, in the fourth region Z4, it is preferable to configure the volume of the solid structure portion 44 to be 20-40% and the volume of the lattice structure portion 42 to be 30-50%, so that the proportion of the lattice structure portion 42 is greater. Even with this configuration, it is possible to achieve a structure that has sufficient strength against machining resistance (its main force, thrust force, and feed force) while achieving weight reduction, as described above.

As shown in Figures 3 to 5 and 7, in this shank portion 32, the boundary surface between the solid structure portion 44 (solid structure portion) and the lattice structure portion 42 (lattice structure portion) has a free surface shape. By configuring it in this way, the boundary between the solid structure portion 44 and the lattice structure portion 42 does not have a simple shape, and this makes it possible to provide a machining tool with an optimally arranged solid structure portion 44 and lattice structure portion 42.

The shape of the shank portion 32 (the portion having a lattice structure) of the machining tool 26 is preferably derived using topology optimization analysis, and by using such an analysis method, the optimized shape can be derived relatively easily. When using this topology optimization analysis, it is preferable to minimize the amplitude of the cutting direction 36 of the machining tool 26 (amplitude in the direction indicated by the double arrow 62 in FIG. 9) as shown in FIG. 9, and by performing the analysis process in this manner, the shank portion 32 of the machining tool 26 has a structure, for example, as described above.

To explain this with reference to FIG. 11, when not optimized (in other words, when a machining tool with a conventional structure is used), the entire shank of the machining tool is a solid structure, so that the chatter vibration generated during machining has a large vibration amplitude in the thrust force direction caused by machining resistance, as shown by curve Q, and accordingly, the fluctuation of the machining resistance also becomes larger, the vibration amplitude is amplified, and it tends to develop into chatter vibration. On the other hand, when optimized using topology optimization analysis (in other words, when the machining tool 26 of the above-mentioned embodiment is used), the shank 32 of the machining tool 26 includes a solid structure (solid structure portion 44), a lattice structure (lattice structure portion 42), and a hollow structure (hollow structure portion 46), so that the chatter vibration generated during machining has a small vibration amplitude in the thrust force direction caused by machining resistance, as shown by curve R, and therefore the vibration amplitude tends to be difficult to amplify, and as a result, the above-mentioned machining tool 26 can suppress the occurrence of chatter vibration.

The lattice structure of the shank portion 32 may employ various known lattice structures, for example, the structure shown in FIG. 10. In one lattice structure 70 (lattice structure) constituting the lattice structure portion 42, an upper connection surface 78 and a lower connection surface 80 are provided at the center of the top surface 74 and the bottom surface 76 of a reference cube 72 that is the reference for each lattice structure 70, and a pair of adjacent lattice structures 70 in the vertical direction are joined by the lower connection surface 80 of the upper lattice structure 70 and the upper connection surface 78 of the lower lattice structure 70. In addition, a pair of horizontal connection surfaces 84, 86 are provided on the side surface 82 of the reference cube 70, and these horizontal connection surfaces 84, 86 and the upper connection surface 78 are connected by upper inclined lattice portions 88, 90, and these pair of horizontal connection surfaces 84, 86 and the lower connection surface 80 are connected by lower inclined lattice portions 92, 94.

Although the horizontal connecting surfaces 84, 86 of one side 82 of the reference cube 72 have been described, the other three sides 96, 98, 100 are similarly configured, and therefore laterally adjacent lattice structures 70 are joined, for example, by a pair of horizontal connecting surfaces 84, 86 of the side 82 of one lattice structure and, for example, a horizontal connecting surface (not shown) of the opposing side 98 of the other lattice structure 70.

Since adjacent lattice structures 70 are joined vertically and horizontally as described above, the assembly of lattice structures 70 (lattice structure portion 42) is a three-dimensional combination of lattice structures 70.

Each of the lattice structures 70 preferably has a solid occupancy of 30 to 70%. If the solid occupancy is less than 30%, the strength of the lattice structure 42 may decrease, and if the solid occupancy is greater than 70%, it becomes closer to a solid structure, making it difficult to achieve sufficient weight reduction. The solid occupancy in the lattice structure 70 of this embodiment refers to the proportion of the volume of the reference cube 70 occupied by the lattice portions of the lattice structure (upper inclined lattice portions 88, 90 and lower inclined lattice portions 92, 94).

The lattice spacing of each lattice structure 70 is preferably 0.5 to 5.0 mm, and for smaller components, the lattice spacing will be smaller, so for a machining tool like this 26, it is preferable to set it to about 1.0 to 3.0 mm.

In this machining tool 26, the lattice structure 42 and hollow structure 46 in the shank 32 can be used as a liquid flow path to feed a liquid such as machining fluid toward the cutting blade attachment 34 (the machining tip 40 attached thereto). In this case, the continuous gaps in the lattice structure 42 function as part of the liquid flow path, and the machining fluid can be fed toward the cutting blade attachment 34 without providing a dedicated liquid flow path, thereby supplying the machining fluid to the machining area of the machining tool 26.

Although one embodiment of the machining tool according to the present invention has been described above, the present invention is not limited to this embodiment, and various changes and modifications are possible without departing from the scope of the present invention.

A machining experiment was conducted to confirm the effect of this machining tool. An NC lathe (6-inch comb-tooth NC lathe, model: TOP-TURN II) manufactured and sold by Takamatsu Machinery Co., Ltd. was used as the machining device for this experiment, and the machining tool was attached to the comb-tooth tool mounting table of this NC lathe via a tool holder to conduct the machining experiment. The shank portion of the machining tool in the example was produced with a 3D printer using steel powder (so-called powder of steel material). The shank portion of the machining tool was of the above-mentioned form, and had a lattice structure portion, a solid structure portion, and a hollow structure portion.

The structural ratios of the front of the shank were as follows: In the first region of the front of the shank, the solid structure was 31%, the lattice structure was 38%, and the hollow structure was 31%; in the second region, the solid structure was 12%, the lattice structure was 16%, and the hollow structure was 72%; in the third region, the solid structure was 47%, the lattice structure was 40%, and the hollow structure was 13%; and in the fourth region, the solid structure was 34%, the lattice structure was 38%, and the hollow structure was 28%.

The workpiece was S45C (diameter 53-59 mm, length 88 mm), and in this machining experiment, the cutting conditions were as follows: workpiece rotation speed: 486 rpm (adjusted so that the workpiece diameter was 60 mm and the peripheral speed was 90 m/min), feed rate: 0.15 mm/rev, depth of cut: 0.2 mm, cutting location: outer periphery of workpiece, dry machining.

In the examples, the protrusion amount L of the machining tool was changed, and the vibrations that occurred when L = 54 mm (L/D = 4.5), L = 60 mm (L/D = 5.0), L = 66 mm (L/D = 5.5), and L = 72 mm (L/D = 6.0) were recorded. Note that L/D is the ratio (length/diameter) of the length (L mm) to the diameter (D mm), and the protrusion amount of the machining tool is the distance from the cutting edge to the support jig (tool holder). In this machining experiment, the vibrations (chatter vibrations, etc.) that occurred during cutting were measured using a vibration measuring device (model number: 4507 B 001) manufactured by Brüel & Kjær.

The results of the machining experiment in Example 1 are shown in Figures 12, 15, and 16. When L = 54 mm and L = 60 mm, the vibration generated was small, as shown in Figures 12(a) and 12(b). However, when the protrusion amount was increased to L = 66 mm and L = 72 mm, the vibration generated was greatly amplified, and chatter vibration occurred, as shown in Figures 12(c) and 12(d).

As Comparative Example 1, a machining tool with a general steel shank was used to cut the same workpiece under the same cutting conditions as in the Example, and the vibrations (such as chatter vibrations) that occurred during this cutting were measured using the vibration measuring device described above (model number: 4507 B 001).

In this comparative example 1, the protrusion amount L of the machining tool was changed, and the vibrations that occurred when L = 36 mm (L/D = 3.0), L = 42 mm (L/D = 3.5), L = 48 mm (L/D = 4.0), and L = 52 mm (L/D = 4.5) were recorded.

The results of the machining experiment for Comparative Example 1 are shown in Figures 13, 15, and 16. When L = 36 mm and L = 48 mm, the vibration generated was small, as shown in Figures 13(a) and 13(c). However, when L = 42 mm and L = 52 mm, the vibration generated was greatly amplified, generating chatter vibration, as shown in Figures 13(b) and 13(d). When L = 42 mm and L = 52 mm, chatter vibration occurred in the form of two large peaks.

In addition, as a comparative example 2, a machining tool equipped with a shank made of cemented carbide was used to cut the same workpiece under the same cutting conditions as in the example, and the vibrations (such as chatter vibrations) generated during this cutting were measured using the vibration measuring device described above (model number: 4507 B 001).

In this comparative example 2, the protrusion amount L of the machining tool was also changed, and the vibrations that occurred when L = 54 mm (L/D = 4.5), L = 60 mm (L/D = 5.0), and L = 66 mm (L/D = 5.5) were recorded.

The results of the machining experiment for Comparative Example 2 are shown in Figures 14 to 16. When L = 54 mm and L = 60 mm, the vibration generated was small, as shown in Figures 14(a) and 14(b). However, when L = 66 mm, the vibration generated was greatly amplified, and chatter vibration occurred, as shown in Figure 14(c).

The experimental results of the Example and Comparative Examples 1 and 2 are summarized as shown in Figures 15 and 16. In Comparative Example 1, chatter vibration occurs even when the protrusion amount of the machining tool is about 42 mm (L/D = 3.5), but in the machining tool of the Example, chatter vibration does not occur until the protrusion amount of the machining tool is about 66 mm, and this protrusion amount at which chatter vibration occurs is almost the same as in Comparative Example 2. It was confirmed that the machining tool of the Example (i.e., one equipped with a steel shank portion having a lattice structure) has dynamic rigidity characteristics almost equivalent to those equipped with a shank portion made of cemented carbide, and can suppress the occurrence of chatter vibration.

2 lathe body 16 turret 24 tool holder 26 machining tool 28 tool body 30 attachment support portion 32 shank portion 34 cutting blade attachment portion 40 machining tip 42 lattice structure portion 44 solid structure portion 46 hollow structure portion 50 shank front portion 52 shank rear portion 70 lattice structure

Claims (9)

A machining tool including a tool body having a mounting support portion attached to a tool mounting portion of a machining device, a shank portion extending from the mounting support portion, and a cutting blade mounting portion provided at a tip portion of the shank portion, and a machining tip attached to the cutting blade mounting portion of the tool body,
the shank portion is composed of a solid structure portion which is a solid structure, a lattice structure portion which is a lattice structure, and a hollow structure portion which is a hollow space, and the volume of the lattice structure portion of the shank portion is 20 to 40% of the total volume of the solid structure portion and the lattice structure portion of the shank portion,
The machining tool is also characterized in that, in the front part on the cutting edge mounting portion side with respect to the axial center of the shank portion, the volume of the solid structure portion is 20 to 40%, the volume of the lattice structure portion is 25 to 45%, and the volume of the hollow structure portion is 25 to 45% . The machining tool according to claim 1, characterized in that the shank portion is composed of a rear shank portion on the mounting support portion side with respect to the axial center, and a front shank portion on the cutting blade mounting portion side with respect to the axial center, and the weight of the front shank portion is 60% or less of the weight of the rear shank portion . The machining tool described in claim 2, characterized in that the volume of the lattice structure portion at the front of the shank is 40% or more of the total volume of the solid structure portion and the lattice structure portion at the front of the shank, and in the front of the shank, the proportion of the volume of the lattice structure portion to the total volume of the solid structure portion and the lattice structure portion gradually increases toward the cutting edge attachment portion. The machining tool described in claim 2, characterized in that when looking at the shank portion from the cutting blade attachment portion side, the front portion of the shank is divided into four regions in a counterclockwise direction around its central axis with the cutting direction of the machining tool as a reference, into first to fourth regions, the volume of the lattice structure portion is the largest in the first region, the volume of the hollow structure portion is the largest in the second region, the volume of the solid structure portion is the largest in the third region, and the volume of the lattice structure portion is the largest in the fourth region. 3. The machining tool according to claim 2, characterized in that, when viewing the shank portion from the cutting blade attachment portion side, the shank front portion is divided into four portions counterclockwise around its central axis with respect to the cutting direction of the machining tool to define first to fourth regions, in the first region, the volume of the solid structure portion is 20 to 40% and the volume of the lattice structure portion is 30 to 50%, in the second region, the volume of the solid structure portion is 0 to 20% and the volume of the lattice structure portion is 10 to 30%, in the third region, the volume of the solid structure portion is 40 to 60% and the volume of the lattice structure portion is 30 to 50%, and in the fourth region, the volume of the solid structure portion is 20 to 40% and the volume of the lattice structure portion is 30 to 50%. 6. The machining tool according to claim 1, wherein a boundary surface between the solid structure portion and the lattice structure portion in the shank portion has a free-form surface shape. A machining tool according to any one of claims 1 to 6, characterized in that a shape including the solid structure, the lattice structure and the hollow structure in the shank portion is derived using a topology optimization analysis, and in the topology optimization analysis, an amplitude in the cutting direction in a vibration mode of the machining tool that excites chatter vibration is minimized. A machining tool according to any one of claims 1 to 7, characterized in that each lattice structure constituting the lattice structure portion of the shank portion has a solid occupancy rate of 30 to 70% and a lattice spacing of 0.5 to 5.0 mm. A machining tool as described in any one of claims 1 to 8, characterized in that a liquid flow path is provided inside the shank portion for supplying liquid to the cutting edge mounting portion side, and the lattice structure portion forms part of the liquid flow path.

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