JP2007175830A - Christmas tree formed milling cutter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an excellent sharpness without a slant of a tree-shaped groove, in a christmas tree formed milling cutter which is gradually reduced in size toward the tool end while repeating increase and decrease in blade end diameter. <P>SOLUTION: When the outer peripheral cutting edge 38 is a helical flute inclined at a helix angle λ ranging from 3° to 17° in the opposite direction (counterclockwise helix direction) to the tool rotating direction, seen from the shank 32 side, the sharpness is improved to obtain a favorable machined surface (a finished surface), and a slant of a christmas tree formed groove is restrained. When the rake angle of the outer peripheral cutting edge 38 ranges from 4° to 16°, an excellent sharpness can be obtained to further improve the cutting performance. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a Christmas cutter, and more particularly, to a Christmas cutter with excellent sharpness with less processing grooves (tree-shaped grooves).

As an attachment structure for attaching a turbine impeller such as a gas turbine to a rotating shaft, one blade 14 of the turbine impeller is provided in a number of tree-shaped grooves 12 formed on the outer peripheral portion of the rotating shaft 10 as shown in FIG. There are some that fit each other. FIG. 8 is an enlarged cross-sectional view of the tree-shaped groove 12, which is symmetrical with respect to the groove center S, and the groove width increases or decreases in the groove depth direction (downward in the figure) like an inverted Christmas tree. It is gradually narrowed and is provided with three wide portions 16, 18, and 20 that are spaced apart in the groove depth direction and have a wide groove width, and the width dimensions of these wide portions 16, 18, and 20 are deep positions. The one on the (groove bottom side) is smaller. And as a tool for cutting such a tree-shaped groove, the edge diameter of the outer peripheral cutting edge gradually increases and decreases with increasing or decreasing toward the tool tip side corresponding to the change of the groove width of the tree-shaped groove. Christmas cutters are known. The cutter described in Patent Document 1 is one example, and is for rough machining provided with a corrugated luffing cutting edge as an outer peripheral cutting edge.
JP-A-11-267916

  However, in such a conventional Christmas cutter, there is a problem that the sharpness is lost depending on the processing conditions, and the tree-shaped groove taole becomes large.

  The present invention has been made against the background described above, and an object of the present invention is to provide a Christmas cutter with less tree-shaped grooves and excellent sharpness.

  In order to achieve this object, the present inventors have conducted various experiments and researches. As a result, the twist direction of the outer peripheral cutting edge is reversed, and when cutting intermittently with rotation around the axis, It has been found that when cutting is performed by cutting into the workpiece first from the diameter side, the sharpness is improved and the number of tree-shaped grooves is reduced. That is, the conventional Christmas cutter is driven to rotate in the clockwise direction of the axis when viewed from the shank side, and is moved in a direction perpendicular to the axis with respect to the workpiece, thereby intermittently cutting the tree. While the shape groove is cut, the outer peripheral cutting edge is right-handed, so when cutting intermittently, the tool tip is cut first from the small diameter side into the workpiece. The small-diameter portion has a low cutting speed and a low rigidity and is separated from the grip portion (shank or the like) of the tool.

  The present invention has been made on the basis of the above knowledge. In the first invention, the diameter of the outer peripheral cutting edge is gradually decreased to increase or decrease as it goes toward the tip of the tool, and is rotated around the axis. In the Christmas cutter that cuts the tree-shaped groove of the inverted Christmas tree shape by being moved relative to the workpiece in a direction perpendicular to the axis, the outer peripheral cutting edge rotates the tool as viewed from the shank side. Inclined at a twist angle in the range of 3 ° to 17 ° in the direction opposite to the direction.

  2nd invention is the Christmas cutter of 1st invention, The rake angle of the said outer periphery cutting edge is in the range of 4 degrees-16 degrees, It is characterized by the above-mentioned.

  Thus, when the outer peripheral cutting edge is a twisted blade inclined at a twist angle in the range of 3 ° to 17 ° in the direction opposite to the tool rotation direction seen from the shank side, according to the experiments by the present inventors, The sharpness was improved and a good machined surface was obtained, and the tree-shaped groove taole was suppressed. This is because if the outer peripheral cutting edge is a twisted blade inclined in the direction opposite to the tool rotation direction, cutting is performed by cutting into the workpiece first from the large-diameter portion on the shank side during intermittent cutting. Since the large diameter portion has a high cutting speed and high rigidity and is close to the gripping portion of the tool, it is considered that the cutting performance is improved as compared with the case where cutting is performed from the small diameter portion on the tip side.

  In the second invention, since the rake angle is in the range of 4 ° to 16 °, an excellent sharpness is obtained and the cutting performance is further improved.

  The outer peripheral cutting edge of the present invention is left-handed when the tool rotation direction viewed from the shank side is right-handed, and is right-handed when left and right, but this is a chip discharge groove that forms the outer peripheral cutting edge. Is defined by the twist angle. When the twist angle of the chip discharge groove (= the twist angle of the outer peripheral cutting edge) is smaller than 3 °, the sharpness is deteriorated, the cutting resistance is increased, the vibration and the cutting noise are increased, and the processing surface is deteriorated. If the angle is larger than 17 °, minute chipping is likely to occur, the processed surface is deteriorated, and the thickness of the tree-shaped groove is increased. Therefore, it is necessary to set the angle within the range of 3 ° to 17 °.

  If the rake angle of the outer peripheral cutting edge is smaller than 4 °, the sharpness becomes worse, the vibration and cutting noise increase, and the machining surface becomes worse. On the other hand, if the rake angle is larger than 16 °, minute chipping easily occurs. Since the surface becomes worse, it is desirable that the angle be in the range of 4 ° to 16 °.

  The Christmas cutter of the present invention is suitably applied to a finishing tool having a cutting allowance of about 1.0 mm or less, for example, but for a roughing Christmas cutter provided with a roughing cutting edge such as a corrugated as an outer cutting edge. It can also be applied.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
The Christmas cutter 30 shown in FIG. 1 is for finishing with a cutting depth (cutting allowance) of about 0.5 mm with respect to the side surfaces on both sides of the roughly processed tree-shaped groove. The shank 32 and the blade 34 are integrated. In preparation. The blade portion 34 is provided with four chip discharge grooves 36 at equiangular intervals around the axis O, four outer peripheral cutting edges 38 along the chip discharge groove 36, and the outer peripheral cutting edges thereof. 38 is provided with a bottom blade 39 that is continuous. The outer peripheral cutting edge 38 and the bottom cutting edge 39 perform cutting when the Christmas cutter 30 is rotated clockwise as viewed from the shank 32 side, and the chip discharge groove 36 is 3 ° to 17 °. Is inclined counterclockwise at a twist angle λ within the range of. Further, the outer peripheral cutting edge 38 is gradually reduced in diameter while increasing or decreasing the blade tip diameter toward the tool tip side corresponding to the uneven shape of the groove side surface of the tree-shaped groove to be processed. The rake angle is in the range of 4 ° to 16 °.

  FIG. 2 is a photograph showing a comparison between the product of the present invention and the conventional product, and the product of the present invention in (a) is a case where the outer peripheral cutting edge 38 with a twist angle λ = 5 ° is provided. The conventional product (b) is a case where a straight blade parallel to the axis O is provided as the outer peripheral cutting edge 38.

  Such a Christmas cutter 30 is rotated around the axis O and is moved relative to the workpiece in a direction perpendicular to the axis O, whereby the reverse Christmas as shown in FIG. 8 is performed. A tree-shaped tree-shaped groove can be cut.

Here, FIG. 3 (a) shows the results of examining the cutting performance when the twist angle λ is changed variously, and FIG. 3 (b) shows the cutting performance when the rake angle of the outer peripheral cutting edge 38 is changed variously. It is the result of having investigated. 4A is a processing condition when examining cutting performance, and FIG. 4B is a diagram for explaining the meaning of the evaluation symbols described in FIGS. 3A and 3B. Among the evaluation items in FIG. 3, “vibration”, “cutting sound”, and “finish surface” are related to sharpness, “vibration” is the magnitude of vibration of the entire machine, and “cutting sound” is sound quality and volume. “Finished surface” is the surface state of the processed surface, and both were compared and evaluated with the tester's sense based on the evaluation criteria of FIG. 4 (b). “Abrasion” and “blade chipping” were comparatively evaluated by visual inspection by a tester through microscopic observation after cutting. “Cutting resistance (N)” is a maximum value measured by a load sensor such as a strain gauge during cutting. As shown in FIG. 5, the “groove thickness (mm)” is an average value of the deviation dimensions ΔX ₁ and ΔX ₂ at the groove bottom positions on both side walls of the cut tree-shaped groove. "Is generally 0.05 mm as a limit value, that is, an allowable maximum value. Further, such “groove taole” is a phenomenon caused by the difference between up-cut and down-cut, and is inclined to the up-cut side (left side) as shown by a dotted line in FIG. In addition, the tree-shaped groove | channel of FIG. 5 is the schematic which abbreviate | omitted increase / decrease in the width dimension, and showed both side surfaces as a simple inclined surface.

  From the result of FIG. 3 (a), when the twist angle λ is 5 °, 10 °, or 15 ° by left-handed twist, “vibration”, “cutting sound”, and “finish surface” related to sharpness. Are “o”, almost no “wear” and “blade chipping”, “groove taole” is 0.02 mm to 0.04 mm and below the limit value, and “cutting resistance” is 2200 to 2400. It can be seen that relatively small and comprehensive cutting performance is obtained. On the other hand, when the twist angle λ is 0 ° or 5 ° with right twist, the sharpness is deteriorated and the cutting resistance is increased, the vibration and cutting noise are increased and the finished surface is deteriorated, while the twist angle λ is increased. When the left twist is 20 °, minute chipping is likely to occur, the finished surface is deteriorated, and the thickness of the tree-shaped groove is increased. From this, it is desirable that the twist angle λ is inclined within a range of about 3 ° to 17 ° in the direction opposite to the tool rotation direction (left twist direction in the embodiment) as viewed from the shank 32 side. If the outer peripheral cutting edge 38 of the Christmas cutter 30 is a torsional blade inclined in the direction opposite to the tool rotation direction seen from the shank 32 side, the workpiece is first processed from the large diameter portion on the shank 32 side during intermittent cutting. Cutting is performed by cutting into an object, but the large diameter part has high cutting speed and high rigidity and is close to the gripping part of the tool, so compared with the case where cutting is performed from the small diameter part on the tip side. Therefore, the cutting performance is considered to be improved.

  In addition, from the result of FIG. 3 (b), when the rake angle is 5 °, 10 °, or 15 °, a good sharpness is obtained and there is no chipping and a good cutting performance is obtained. I understand. On the other hand, when the rake angle is 0 °, the sharpness deteriorates and the vibration and cutting noise increase and the finished surface is deteriorated. On the other hand, when the rake angle is 20 °, minute chipping is likely to occur and the finished surface is deteriorated. Becomes worse. Therefore, it is desirable that the rake angle is in the range of about 4 ° to 16 °.

  Thus, according to the Christmas cutter 30 of the present embodiment, the outer peripheral cutting edge 38 is a twisted blade inclined at a twist angle λ in the range of 3 ° to 17 ° in the direction opposite to the tool rotation direction seen from the shank 32 side. As a result, the sharpness is improved and a good processed surface (finished surface) is obtained, and the tree-shaped groove taole is suppressed. Moreover, since the rake angle is in the range of 4 ° to 16 °, an excellent sharpness is obtained and the cutting performance is further improved.

  In addition, although the said Example demonstrated the case where this invention was applied to the Christmas cutter 30 for finishing, it is also possible to apply to the Christmas cutter 50 for roughing shown in FIG. That is, the outer peripheral cutting edge 52 of the Christmas cutter 50 is constituted by a luffing cutting edge whose blade tip diameter is finely increased and decreased as shown in Patent Document 1, and the phase of the waveform has a plurality of phases. The outer peripheral cutting edges 52 are shifted in the axial direction by 1 / n (n is the number of blades, 3 in the embodiment). Then, the outer peripheral cutting edge 52 is twisted within the range of 3 ° to 17 ° in the direction opposite to the tool rotation direction (left-handed twisting direction in the embodiment) viewed from the shank 32 side in the same manner as the outer peripheral cutting edge 38. And the rake angle may be in the range of 4 ° to 16 °.

  As mentioned above, although the Example of this invention was described in detail based on drawing, this is an embodiment to the last, and this invention implements in the aspect which added various change and improvement based on the knowledge of those skilled in the art. Can do.

It is a front view which shows the Christmas cutter which is one Example of this invention. It is the photograph which compares this invention product and shows a conventional product (straight blade). In the Christmas cutter of FIG. 1, it is a figure explaining the result of having investigated cutting performance about the case where (a) various twist angles (lambda) and (b) various rake angles are changed. It is a figure explaining the process conditions and evaluation criteria in the cutting performance test of FIG. It is a figure explaining the "groove of a groove | channel" of FIG. It is a figure which shows the other Example of this invention, and is a front view equivalent to FIG. It is a figure which shows the tree-shaped groove | channel for attaching the blade | wing of a turbine impeller. It is sectional drawing which expands and shows the tree-shaped groove | channel of FIG.

Explanation of symbols

  12: Tree-shaped groove 30, 50: Christmas cutter 32: Shank 38, 52: Peripheral cutting edge λ: Twist angle

Claims (2)

By gradually increasing the diameter of the cutting edge of the outer peripheral cutting edge toward the tip of the tool, the diameter of the cutting edge gradually decreases, and while being driven to rotate around the axis, it is moved relative to the workpiece in a direction perpendicular to the axis. In the Christmas cutter that cuts the tree-shaped groove of the reverse Christmas tree shape,
The outer peripheral cutting edge is inclined at a twist angle within a range of 3 ° to 17 ° in a direction opposite to the tool rotation direction as viewed from the shank side. The Christmas cutter according to claim 1, wherein a rake angle of the outer peripheral cutting edge is in a range of 4 ° to 16 °.

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