JP2016203328A - Processing method and processing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cutting method or the like, which can prevent shape deterioration resulting from interference between a cutting tool and a target shape even in a case where a standing wall that is not uniform in direction along a radial direction during processing is formed.SOLUTION: In a processing method, while a workpiece W is rotated with respect to a cutting tool 80, the cutting tool 80 is relatively moved in a radial direction R, and in accordance with a blade edge position, which is the position of the blade edge 80a of the cutting tool 80 with respect to the workpiece W, the cutting tool 80 is displaced in the extending direction of a tool axis TX through which the blade edge 80 passes, thereby cutting the workpiece W. Here, a rotating position around the tool axis TX of the cutting tool 80 is adjusted in accordance with the blade edge position with respect to the workpiece W. Thus, even when a standing wall OW that is not uniform in direction along a radial direction R during processing is formed, interference between a target shape OF and a side part 80b of the blade edge 80a of the cutting tool 80 can be prevented.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a machining method and a machining apparatus that perform lathe machining with a cutting tool, and particularly to a machining method and a machining apparatus suitable for high-precision parts such as an optical element or a molding die thereof.

As a processing method of an optical surface or the like, there is a method of forming a concave surface or the like by moving a cutting tool in a radial direction while rotating a material using a lathe. By such lathe processing, a rotationally symmetric shape such as a spherical surface can be processed on the material, but a non-rotationally symmetric surface such as an off-axis surface cannot be processed. In order to overcome this, there is a method called tool servo processing in which the position of the cutting tool in the cutting direction is changed in synchronization with the rotational position of the rotating workpiece. In this tool servo machining, the cutting tool is protruded or retracted according to the position of the workpiece in the rotational direction or circumferential direction, and non-rotationally symmetric machining surfaces such as off-axis surfaces and free-form surfaces can be formed. it can.
Tool servo processing includes Fast Tool Servo (Fast Tool Servo or FTS, a method for driving and controlling a tool table with a cutting tool attached by a piezoelectric element), and Slow Tool Servo (Slow Tool Servo or STS, a tool table) There are two known methods of driving the axis of a machine tool.

  However, even if tool servo machining as described above is used, when there is a standing wall whose direction is not uniform along the radial direction in the target shape after machining the workpiece, the cutting tool and the target shape interfere with each other to achieve high accuracy. In some cases, it may not be possible to perform the processing. That is, for example, when forming an object having an upright wall portion whose direction gradually changes as the radial position increases, such as a spiral diffraction grating, a tool is applied to at least a part of such a target shape. Interference occurs between a portion that is not a rake face (for example, a side face) or a peripheral portion of the tool rake face, and machining is performed while destroying the target shape, thereby reducing machining accuracy.

In addition, as a fine processing method such as a mold for an array lens, by rotating the cutting tool with respect to the work while adjusting the rotation posture on the cutting tool side instead of turning the work, it is displaced in the cutting direction. A method of machining a plurality of concave surfaces as a locus of a cutting tool tip is known (see Patent Document 1). This fine processing method does not presuppose a shape in which a standing wall exists, and seems to cause the same problem as in the case of the tool servo processing.
Further, it is a cutting method for cutting a workpiece by applying vibration in the cutting direction to the workpiece held on the lathe spindle so that predetermined conditions are satisfied such as vibration frequency, amplitude, tool clearance angle, plunge cut angle, etc. It has been known that the tool flank and the workpiece are prevented from colliding with each other during vibration by setting within a range (see Patent Document 2). This cutting method is premised on vibration cutting in which the cutting edge is vibrated at high speed, and this method cannot be applied as it is to the above-mentioned tool servo processing.

JP 2011-11295 A JP 2002-96201 A

  The present invention has been made in view of the problems of the background art described above, and even when a vertical wall-shaped portion whose direction is not uniform along the radial direction during processing is formed, the cutting tool and the target An object of the present invention is to provide a processing method and a processing apparatus capable of preventing the shape from being deteriorated due to interference with the shape.

  In order to achieve the above object, the machining method according to the present invention moves the cutting tool relatively in the radial direction of the workpiece while rotating the workpiece with respect to the cutting tool having a rake face and a flank surface at the cutting edge, The workpiece is cut by displacing the cutting tool in the extending direction of the tool axis through which the cutting edge passes according to the cutting edge position, which is the position of the cutting edge of the cutting tool with respect to the workpiece (specifically, the position in the radial direction or circumferential direction). This is a processing method for performing processing, and the rotational posture around the tool axis of the cutting tool is adjusted in accordance with the cutting edge position of the cutting tool with respect to the workpiece. The tool axis of the cutting tool is also called a tool indexing axis, which corresponds to the direction in which the cutting tool extends with respect to the machining point corresponding to the cutting edge position, and usually extends substantially parallel to the rake face. It is not limited to.

  In the above processing method, the rotational posture around the tool axis of the cutting tool is adjusted according to the cutting edge position of the cutting tool with respect to the workpiece. Even in the case of forming, it is possible to prevent the outer shape of the cutting edge of the cutting tool, the shape of the peripheral portion and the target shape from interfering with each other, and it is possible to prevent the shape from being deteriorated.

  According to a specific aspect of the present invention, in the above processing method, the cutting edge according to the relative rotation angle of the workpiece with respect to the cutting edge of the cutting tool and the radial position with respect to the rotation axis of the cutting edge with respect to the workpiece. The inclination angle with reference to the radial direction around the tool axis is adjusted. In this case, not only the cutting amount in the direction of the tool axis but also the inclination angle around the tool axis is adjusted based on the rotation angle and the radial position.

  According to another aspect of the present invention, the inclination angle of the cutting edge around the tool axis is changed in a range of ± 45 ° at the maximum. In this case, the inclination angle around the tool axis of the cutting edge can be prevented from increasing, and the accuracy of adjusting the rotational posture around the tool axis of the cutting edge according to the position of the cutting edge can be increased.

  According to still another aspect of the present invention, the rotation speed of the workpiece with respect to the cutting tool is 500 rpm or less. In this case, it is possible to prevent fluctuations in the cutting edge position from increasing, and it is possible to increase the processing accuracy of the cutting tool.

  According to still another aspect of the present invention, the rotational posture around the tool axis of the cutting edge is changed so as to follow a standing wall-like shape portion formed on the workpiece. In this case, the standing wall-shaped portion can be formed with high accuracy. Note that the processing of the standing wall-shaped portion is a typical case where the outside of the cutting edge of the cutting tool in the radial direction interferes with the target shape.

According to still another aspect of the present invention, the cutting edge can be retracted at least in a vertical wall-shaped part having a predetermined inclination angle or more with respect to the moving direction of the cutting edge while rotating the workpiece in one first rotation direction with respect to the cutting edge. Select a vertical wall-shaped part with a predetermined inclination angle or more with respect to the direction of movement of the cutting edge by the action of retracting the cutting edge, while selectively processing by operation and rotating the workpiece in the other second rotation direction with respect to the cutting edge. In connection with the rotation in either of the first and second rotational directions, the blade edge is cut or pulled away from the non-standing wall-shaped portion excluding the standing wall-shaped portion having a predetermined inclination angle or more. Machining according to the motion that can be put.
In this case, at the time of rotation in the first rotation direction, a vertical wall-shaped portion (of a type that rises relatively steeply) with a predetermined inclination angle or more with respect to the traveling direction is selectively processed by the operation of retracting the cutting tool, When rotating in the rotational direction, the vertical wall-shaped portion (of a type that rises relatively steeply) with a predetermined inclination angle or more with respect to the traveling direction is selectively processed by the operation of retracting the cutting tool, so the first and second rotations In any rotation of the direction, it is not necessary to machine a steep standing wall formed by cutting the cutting tool so that it protrudes, and the back side of the cutting tool, that is, the flank side and the apex of the standing wall Can prevent the deterioration of the shape due to interference.

  According to still another aspect of the present invention, the step amount of the standing wall-shaped portion formed on the workpiece is equal to or less than the maximum amplitude of the axial position of the cutting tool. In this case, it is possible to precisely process the standing wall-shaped portion.

  In order to achieve the above object, a machining apparatus according to the present invention includes a cutting tool having a rake face and a flank face at a cutting edge, and a first drive for rotating a work relative to the cutting tool around a rotation axis. The cutting edge of the cutting tool passes according to the mechanism, the second drive mechanism that moves the cutting tool relatively in the radial direction perpendicular to the rotation axis, and the cutting edge position that is the cutting edge position of the cutting tool with respect to the workpiece. A third drive mechanism for displacing the cutting tool in the direction in which the tool axis extends; and a fourth drive mechanism for adjusting the rotational attitude of the cutting tool around the tool axis in accordance with the cutting edge position of the cutting tool relative to the workpiece. Prepare.

  In the above processing apparatus, the fourth drive mechanism adjusts the rotational posture around the tool axis of the cutting tool in accordance with the cutting edge position of the cutting tool with respect to the work, so the direction is uniform along the radial direction of the work during processing. Even when a standing wall-like shape portion that is not like is formed, the shape around the cutting edge of the cutting tool and the target shape can be prevented from interfering with each other, and shape deterioration can be prevented.

It is a block diagram explaining the processing apparatus concerning an embodiment. (A) And (B) is the side view and top view of a tool for cutting. It is a conceptual diagram explaining the processing method of embodiment. (A) is an enlarged view explaining the adjustment of the rotational posture of the cutting tool, and (B) is a diagram explaining the adjustment range of the inclination angle of the cutting tool. (A) is a conceptual sectional view explaining processing by rotation in the first rotation direction, and (B) is a conceptual sectional view explaining processing by rotation in the second rotation direction. (A) And (B) is a conceptual sectional view explaining the modification which changed Drawing 5 (A) and 5 (B). (A) is a top view explaining the process by rotation of a 1st rotation direction, (B) is a top view explaining the process by rotation of a 2nd rotation direction. (A) is a top view explaining a processing example, (B) is a perspective view explaining the attitude | position of a processing example and the tool for cutting. It is a flowchart explaining the manufacturing method using the apparatus of FIG. It is a top view explaining another example of processing.

  Hereinafter, a processing apparatus and a processing method according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram schematically illustrating a processing apparatus according to an embodiment. The illustrated machining apparatus 100 includes an NC drive mechanism 91 that enables a lathe-type cutting process that three-dimensionally displaces the cutting tool 80 while rotating the workpiece W, and a drive that drives while controlling the NC drive mechanism 91. A control device 97 and a main control device 98 that controls the overall operation of the device are provided.

The NC drive mechanism 91 has a structure in which a first drive mechanism 94b and a second drive mechanism 94c are placed on a pedestal 94a. Here, the first drive mechanism 94b rotatably supports the work spindle 95a. The first drive mechanism 94b is driven by the drive control device 97 to rotate the work spindle 95a forward or reverse at a desired speed around a rotation axis RA extending in parallel with the Z axis and extending horizontally, and the work spindle 95a. Can be detected and output to the drive control device 97 as angle information. On the other hand, the second drive mechanism 94c supports a movable portion 95b to which the cutting tool 80 is attached, and a third drive mechanism 95c and a fourth drive mechanism 95d are incorporated in the movable portion 95b. The second drive mechanism 94c can support the movable portion 95b and the cutting tool 80, and move them to desired positions along the horizontal X-axis direction and the vertical Y-axis direction at a desired speed. The third drive mechanism 95c is supported by the fourth drive mechanism 95d in the movable portion 95b, and moves the cutting tool 80 forward and backward at a desired speed to a desired position along the horizontal Z-axis direction. Can do. The fourth drive mechanism 95d can rotate the cutting tool 80 around the Z-axis direction extending horizontally. More specifically, the fourth drive mechanism 95d rotates the cutting tool 80 around the tool index axis or the tool axis TX of the cutting tool 80 that extends parallel to the Z axis and extends horizontally, and adjusts the rotation posture thereof. can do. The drive control device 97 can control the position and rotation posture of the cutting tool 80 or its cutting edge 80a via the second drive mechanism 94c and the like.
The workpiece W to be processed is made of metal, glass, ceramics, resin, or the like, and is formed on an optical element such as a special diffraction grating or a phase difference plate by directly cutting and forming a fine structure on itself. However, the optical element of this type may be processed into a corresponding shape as a mold for molding from resin, glass or the like.

  With reference to FIG. 2 (A) and 2 (B), the shape of the principal part of the cutting tool 80 is demonstrated. The cutting tool 80 includes, as a cutting edge 80a, a tip portion 81a having a tip portion 82 where cutting is actually performed, and a shank portion 81b that supports the tip portion 81a. The tip portion 81a has a rake face 83a on the front side, a first flank 83b at the tip, and a second flank 83c on the back side. In the tip part 81a, a tool axis (tool indexing axis) TX passes through the center or center of the tip part 82 so as to extend in the Z-axis direction. An angle γ1 formed by the first flank 83b with respect to the surface perpendicular to the tool axis TX is called a first flank angle, and an angle γ2 formed by the second flank 83c with respect to the surface perpendicular to the tool axis TX is set as the second flank. Called the corner. The second clearance angle γ2 is the maximum clearance angle of the tip portion 81a. The vertical direction t of the first flank 83b, that is, the width t in the Y-axis direction is referred to as the blade thickness. The tip portion 82 of the cutting tool 80 is an arc formed at the boundary between the rake face 83a and the first flank 83b, and moves in the Y-axis direction relative to the workpiece W shown in FIG. Then, the surface Wa of the workpiece W is cut. In a specific application example, the first clearance angle γ1 was set to 10 to 60 °, the second clearance angle γ2 was set to 45 to 60 °, and the blade thickness t was set to about 0.05 mm or more. Further, the rake face 83a extends substantially parallel to the XZ plane, but is slightly inclined so as to be on the −Y side on the root shank portion 81b side. In addition, although the illustrated chip part 81a has a V-shaped tip shape, a tip shape such as a semicircular shape can be adopted depending on the application.

Returning to FIG. 1, the drive control device 97 enables high-precision numerical control, and drives a motor, a position sensor, and the like built in the NC drive mechanism 91 under the control of the main control device 98. Thus, the first and second drive mechanisms 94b and 94c, the third drive mechanism 95c, the fourth drive mechanism 95d, and the like are appropriately operated to a target state. For example, the work spindle 95a and the work W are rotated around the rotation axis RA at a relatively high speed by the first drive mechanism 94b. The rotation of the work spindle 95a by the first drive mechanism 94b can be, for example, only in the forward direction, but can also be bidirectional in the forward and reverse directions. When the work spindle 95a is viewed in the + Z axis direction, the clockwise rotation (CW) is the forward rotation, and when the work spindle 95a is viewed in the + Z axis direction, the counterclockwise (CCW) rotation is the reverse rotation. To do. At this time, the first drive mechanism 94b calculates the rotation angle of the workpiece W from the rotation angle of the workpiece spindle 95a.
On the other hand, the machining point of the tip end portion 82 of the cutting tool 80 is first placed on the rotation axis RA by the second drive mechanism 94c, that is, the rotation axis RA and the tool axis TX are aligned, and the tip end portion 82 is moved to the workpiece W. Alternatively, the workpiece spindle 95a is moved (feeded) at a relatively low speed in the X-axis direction that is the radial direction of the workpiece spindle 95a. In parallel with this, the third drive mechanism 95c moves the tip portion 82 of the cutting tool 80 forward and backward at a relatively high speed in the Z-axis direction or the tool axis TX direction. Among the forward and backward movements, the + Z direction corresponds to the cutting operation or the forward movement operation of the cutting tool 80, and the −Z direction corresponds to the operation for retracting the cutting tool 80 or the backward movement operation. In such advancement and retreat, the Z position of the cutting edge 80a of the cutting tool 80, in other words, the axial position of the cutting edge 80a of the cutting tool 80, the rotation direction and rotation angle of the work spindle 95a or the work W, and the cutting tool 80 It is adjusted according to the radial position. Thereby, a mirror surface or the like having a desired shape can be formed at an arbitrary position on the surface Wa of the workpiece W. The shape formed on the surface Wa of the workpiece W includes not only a standing wall shape such as a step and a slope, but also a composite of these with a flat surface, a spherical surface, a free curved surface, and the like. Further, the fourth drive mechanism 95d changes the rotational posture of the cutting edge 80a of the cutting tool 80 in correspondence with the above operation. That is, the fourth drive mechanism 95d rotates the cutting tool 80 around a horizontally extending tool axis (tool indexing axis) TX so that the side portion 80b of the cutting edge 80a of the cutting tool 80 has a target shape. Prevent interference. Here, the side part 80b that causes interference includes the peripheral part of the rake face 83a in addition to the side face of the chip part 81a. In order to achieve such interference avoidance, the rotation posture or inclination angle of the cutting tool 80 or the cutting edge 80a depends on the rotation direction and rotation angle of the workpiece spindle 95a or workpiece W and the radial position of the cutting tool 80. Adjusted. Thereby, it is possible to prevent the side portion 80b of the blade edge 80a and the like from interfering with the target shape, and to prevent the blade edge 80a itself from working while breaking the target shape, such as a step formed on the surface Wa, a slope, etc. The processing accuracy of the standing wall shape can be maintained.

The main control device 98 has a storage unit (not shown) that receives and stores information related to the machining shape of the workpiece W from the outside. The main control device 98 is a control unit that controls the operation of the NC drive mechanism 91 in cooperation with the drive control device 97. The information regarding the machining shape of the workpiece W includes information corresponding to a step of operating the first drive mechanism 94b, the second drive mechanism 94c, the third drive mechanism 95c, the fourth drive mechanism 95d, and the like, and more specifically. The main controller 98 accepts the design shape of the workpiece W or a target shape which is a corrected shape corrected to realize this as machining shape information. This machining shape information is, for example, the axial direction of the cutting edge 80a of the cutting tool 80 as a function of the radial position of the workpiece spindle 95a or the workpiece W from the rotation axis RA and the rotation angle of the workpiece spindle 95a at the radial position. In addition to the position, the rotation posture (specifically, the inclination angle) of the cutting edge 80a of the cutting tool 80 is included. Accordingly, the rotational angle of the workpiece spindle 95a or the workpiece W is monitored via the first drive mechanism 94b while receiving the radial position feedback from the second drive mechanism 94c, and the cutting tool 80 is monitored by the third drive mechanism 95c. And the rotational posture of the cutting tool 80 can be adjusted, and the tip portion 82 of the cutting tool 80 is moved relative to the workpiece W along the target shape, And the inclination attitude | position can be kept appropriate with respect to a target shape.
Furthermore, in the main control device 98, in consideration of the convenience of processing by the cutting tool 80 having the shape shown in FIG. 2A, when the target shape includes a standing wall facing in the opposite direction like a groove shape or a saddle shape, The machining process is prepared not only for forward rotation but also divided into two cutting processes corresponding to forward and reverse rotation. That is, the main controller 98 determines the cutting tool 80 in the first cutting process corresponding to the normal rotation of the work spindle 95a from the machining shape information including the radial position, the rotation angle, the axial position and the like as described above. The locus of the machining point corresponding to the tip portion 82 and the locus of the machining point corresponding to the tip portion 82 of the cutting tool 80 in the second cutting process corresponding to the reverse rotation of the work spindle 95a are calculated. As described above, the main control device 98 performs the cutting process that is normally performed in a lump into a first cutting process that uses normal rotation of the work spindle 95a and a second cutting process that uses reverse rotation of the work spindle 95a. It can be divided and performed. Specifically, in the first cutting process in which the work spindle 95a is rotated in the clockwise direction (CW), which is the first rotation direction, the locus of the machining point corresponding to the tip portion 82 of the cutting tool 80 and the rotational attitude of the cutting edge 80a. Alternatively, for the second cutting step of calculating the tilt angle and rotating the work spindle 95a in the counterclockwise direction (CCW), which is the second rotation direction, the locus of the machining point and the cutting edge corresponding to the tip 82 of the cutting tool 80 The rotational attitude or inclination angle of 80a is calculated and stored individually in the storage unit. The trajectory of the first cutting process and the trajectory of the second cutting process described above may be prepared externally in advance and input to the main controller 98.

  Hereinafter, with reference to FIG. 3 etc., the basic concept of the processing method of the workpiece | work W is demonstrated.

The workpiece W shown in FIG. 1 is supported by the first drive mechanism 94b and rotates clockwise (CW) or counterclockwise (CCW) around the rotation axis RA together with the workpiece spindle 95a. On the other hand, when the work W is fixed as shown in FIG. 3, the cutting tool 80 rotates in the opposite direction, and a circular locus A is drawn. That is, when the workpiece W rotates together with the workpiece spindle 95a in the clockwise direction, for example, the cutting edge 80a or the tip portion 82 of the cutting tool 80 at the radial position (radial position) r in the radial direction R from the rotation axis RA is Rotates in the relative traveling direction or the rotational direction Dr, which is counterclockwise. At this time, the relative rotation angle of the tip portion 82 of the cutting tool 80 is θ. That is, the cutting edge 80a or the tip portion represented by the cylindrical coordinates (r, θ, zt) is controlled by controlling the axial position that is the coordinate value zt in the Z-axis direction of the cutting edge 80a or the tip portion 82 of the cutting tool 80. 82 trajectories A can be set, and the shape to be transferred to the surface Wa of the workpiece W can be arbitrarily set. At this time, the rotation speed of the work spindle 95a is set to a relatively low speed of 500 rpm or less. If the rotation speed of the workpiece spindle 95a or the workpiece W is large, it becomes difficult to synchronize the cutting edge 80a of the cutting tool 80 with the rotation of the workpiece spindle 95a, and it becomes difficult to ensure the processing accuracy. Is set to 500 rpm or less so that the processing accuracy can be easily secured.
If the change in the coordinate value zt, which is the axial position of the tip 82 of the cutting tool 80, corresponds to a slowly changing path as in the conventional optical surface, no particular problem occurs. When the coordinate value zt of 82 gives a path that changes rapidly, there arises a problem that the cutting edge 80a of the cutting tool 80 interferes with a target shape to be formed on the workpiece W.

  An example of a phenomenon in which the cutting edge 80a of the cutting tool 80 interferes with a target shape to be formed on the workpiece W will be described with reference to FIGS.

As shown in FIG. 2A, the cutting edge 80a of the cutting tool 80 has not only the tip portion 82 but also a side portion 80b in the vicinity of the tip portion 82. For this reason, there is no particular problem when the target shape to be processed into the workpiece W is relatively flat. However, when the target shape to be processed into the workpiece W forms a steep standing wall such as a groove shape or a bowl shape, the target shape May interfere with the cutting edge 80a.
FIG. 4A shows a case where the target shape OF is a steep standing wall OW. When machining such a standing wall OW, if the rake face 83a of the blade edge 80a extends in the radial direction R and is not parallel to the standing wall OW of the target shape OF as indicated by a dotted line, the outer edge of the tip end portion 82 of the blade edge 80a. Since the side part 80b adjacent to is arranged so as to be recessed into the standing wall OW of the target shape OF, interference occurs between them, and the cutting edge 80a itself performs processing while destroying the target shape OF. Will be reduced. On the other hand, if the rake face 83a of the blade edge 80a is arranged so as to extend in parallel with the standing wall OW of the target shape OF, the side portion 80b of the blade edge 80a and the like can be prevented from interfering with the standing wall OW of the target shape OF. The cutting edge 80a itself can prevent the machining while breaking the target shape OF and maintain the machining accuracy. Therefore, as shown in FIG. 3, the rotational attitude of the cutting edge 80a, that is, the inclination angle α with respect to the radial direction R is adjusted according to the rotation angle θ of the cutting edge 80a and the radial position r (for example, r1, r2) in the radial direction R. Then, as shown by a solid line in FIG. 4A, the rake face 83a is arranged so as to extend along the standing wall OW. In principle, when the standing wall OW is not processed, that is, when a relatively flat portion is processed, the inclination angle α of the blade edge 80a is returned to zero. However, when machining such a relatively flat portion, the machining itself is possible and the accuracy is not deteriorated without returning the inclination angle α of the blade edge 80a to zero. Therefore, in the vicinity angle region in which the rotation angle θ of the blade edge 80a approaches within the predetermined angle or less with respect to the position of the standing wall OW, the inclination angle α of the blade edge 80a is gradually increased or decreased to reach the standing wall OW. The rake face 83a extends along the standing wall OW. Conversely, in the vicinity angle region where the rotation angle θ of the blade edge 80a is within a predetermined angle or less with respect to the position of the standing wall OW, the inclination angle α of the blade edge 80a is changed to gradually return to zero. That is, when the standing wall OW is not processed, there is a certain degree of freedom in setting the inclination angle α of the cutting edge 80a, but it is desirable that the change in the inclination angle α of the cutting edge 80a is continuous and gentle.
FIG. 4B is a diagram illustrating an appropriate range of the inclination angle α of the blade edge 80a. When the inclination angle α of the blade edge 80a exceeds ± 45 °, the rake face 83a is greatly inclined with respect to the traveling direction of the blade edge 80a, and precise machining by the tip portion 82 becomes difficult. As shown in the drawing, when the inclination angle α of the blade edge 80a is within a range of ± 45 °, precise shape processing corresponding to the locus of the blade edge 80a is relatively easily achieved. Further, when the inclination angle α of the blade edge 80a is changed at a relatively large angle close to 45 °, it is not easy to increase the rotation speed of the workpiece spindle 95a and the workpiece W from the viewpoint of ensuring machining accuracy. Thus, when the inclination angle α of the cutting edge 80a is changed at a relatively large angle, it is desirable that the rotation speed of the work spindle 95a be close to the changing speed or the rotation speed of the inclination angle α of the cutting edge 80a.

  Furthermore, when the target shape includes a pair of standing walls or steps opposite to each other such as a groove shape or a saddle shape, a second flank surface provided on the tip 82 of the cutting tool 80 shown in FIG. There is a possibility that the back surface) 83c and the like interfere with the target shape to be formed on the workpiece W to cause shape deterioration. Such a phenomenon remarkably occurs in the case of the standing wall OW in which the slope of the lower step of the target shape has a steeper slope than the second clearance angle γ2.

  5 (A) and 5 (B) show a technique for avoiding shape degradation caused by interference of the second flank 83c other than the tip 82 of the cutting tool 80 with the target shape to be formed on the workpiece W. FIG. FIG. This cross-sectional view is a cross-section along the locus A as shown in FIG. 3 of the tip 82 of the cutting tool 80, and the vertical direction of the drawing indicates the position in the ± Z-axis direction, and the horizontal direction of the drawing. Indicates a position corresponding to the relative rotation angle θ of the tip 82.

As shown in FIG. 5A, when the workpiece W is rotating in the clockwise direction (CW), which is the first rotation direction, the cutting tool 80 is rotated even if there is a steep step in the target shape OF. If the level difference is higher than the direction or the direction of travel Dr, precise machining can be performed only by retracting the cutting tool 80 in the −Z axis direction. That is, the flank surfaces 83b and 83c of the cutting tool 80 and the standing wall OW1 of the target shape OF do not interfere with each other, and processing can be performed without degrading the target shape OF. On the other hand, when the workpiece W is rotating in the clockwise direction (CW), the cutting tool 80 is cut in the + Z-axis direction when machining a step that goes down in the rotational direction of the cutting tool 80 or the forward direction Dr. When cutting is performed so that the top wall OW2 of the target shape OF is cut and the flank surfaces 83b and 83c of the cutting tool 80 interfere with each other, the shape of the vertical wall OW2 becomes dull as shown by the dotted line D. It will be processed, and a processing residue will occur at the root.
The problem that the standing wall OW2 interferes with the cutting tool 80 occurs when the inclination angle Δ of the standing wall OW2 is larger than the second clearance angle γ2 of the tip portion 81a of the cutting tool 80. However, when the first flank 83b of the tip portion 81a is relatively wide, the same interference occurs when the inclination angle Δ of the standing wall OW2 is larger than the first flank angle γ1 corresponding to the first flank 83b. Problems arise.

  Therefore, as shown in FIG. 5B, the workpiece W is rotated in the counterclockwise direction (CCW), which is the second rotation direction, with respect to a part of the same locus A as shown in FIG. In this case, the step of the standing wall OW2 is reversed. That is, the standing wall OW2, which is a step that rapidly decreases in the rotation direction or the traveling direction Dr by the clockwise rotation (CW) shown in FIG. 5A, is counterclockwise (CCW) rotation shown in FIG. 5B. It becomes a level | step difference which goes up rapidly in the rotation direction or the advancing direction Dr. Thus, the standing wall OW2 can be formed by operating the cutting tool 80 so as to be retracted in the −Z-axis direction, and the top of the standing wall OW2 and the flank surfaces 83b and 83c of the cutting tool 80 interfere with each other. Thus, it is possible to reliably prevent the standing wall OW2 from being processed with a dull shape.

  As a result, the surface Wa of the workpiece W can be obtained by combining the processing by the clockwise rotation (CW) shown in FIG. 5A and the processing by the counterclockwise rotation (CCW) shown in FIG. It can be seen that the target shape OF can be formed. At this time, in the illustrated example, a portion (non-standing wall-shaped portion) OF0 that is not a steep step in the target shape OF is also added to the processing by the clockwise rotation (CW) shown in FIG. To do. That is, in the first cutting step shown in FIG. 5A, the pattern PA1 including the standing wall OW1 in the forward rotation direction and the portion (non-standing wall-shaped shape portion) OF0 that is not a steep step is processed. Then, in the second cutting step shown in FIG. 5B, the pattern PA2 including the upright wall OW2 in the reverse direction and the accompanying portion following it is processed. However, the portion that is not a steep step (non-standing wall-shaped portion) OF0 can be added to the second cutting step by the counterclockwise (CCW) rotation shown in FIG. 5B. Furthermore, the pattern PA1 in FIG. 5A is not limited to the pattern PA1 including the single standing wall OW1, but may include a plurality of standing walls OW1, but the pattern PA1 may be formed between the two first type standing walls OW1. When there are two types of standing wall OW2, the periphery of the standing wall OW2 is removed from the pattern PA1. That is, in this case, the first pattern PA1 and the second pattern PA2 are composed of elements that are alternately repeated a plurality of times.

  The machining shown in FIG. 5A and the machining shown in FIG. 5B cannot generally be performed simultaneously because the cutting tool 80 needs to be reversed with respect to the workpiece W. Therefore, even with a series of target shapes OF, it is necessary to switch between clockwise machining (CW) rotation and counterclockwise rotation (CCW) rotation, and to perform them individually. It is necessary to adjust so that the rotation angle θ does not shift. Furthermore, when switching from the first cutting step shown in FIG. 5A to the second cutting step shown in FIG. 5B, it is usually necessary to shift the tip 82 of the cutting tool 80 in the Z-axis direction. However, when this shift becomes large, it becomes difficult to maintain the positional accuracy of the tip 82. For this reason, it is desirable that the displacement amount or shift of the tip 82 when switching from the processing shown in FIG. 5A to the processing shown in FIG. 5B is about 20 nm or less. However, even if the amount of displacement or shift exceeds 20 nm, the cutting edge position of the tip 82 can be accurately corrected by using a control method using real-time or prior measurement.

  When performing the 1st cutting process shown in Drawing 5 (A), it is necessary not to process standing wall OW2 and the near part (standing wall-like shape part) accompanying this in which a level | step difference is reverse. That is, in order to prevent the standing wall OW2 from being deteriorated, the cutting tool 80 is retracted with a sufficient margin in the −Z-axis direction when the cutting tool 80 passes through the standing wall-shaped portion including the standing wall OW2. Missed swing K is required. At this time, the margin for retracting the cutting tool 80 needs to be equal to or greater than the step amount of the standing wall OW2, but when there are a plurality of standing walls OW2, the margin is equal to or greater than the maximum step amount. Such a maximum step needs to be less than or equal to the movable amount of the cutting tool 80 in the Z-axis direction, that is, the maximum amplitude, and is set to 1000 μm or less in a specific embodiment. Conversely, when performing the 2nd cutting process shown in Drawing 5 (B), it is necessary not to process upright wall OW1 and the front part (standing wall-like shape part) accompanying this in which a level | step difference is reverse. For this reason, when the cutting tool 80 passes through the standing wall-shaped portion including the standing wall OW1, the idle swing K is performed to retract the cutting tool 80 with a sufficient margin in the −Z-axis direction.

  6 (A) and 6 (B) show a modification of the machining operation shown in FIGS. 5 (A) and 5 (B). In this case, the processing by the counterclockwise (CCW) rotation shown in FIG. 6 (A) precedes, and the processing by the clockwise (CW) rotation shown in FIG. 6 (B) continues. Also in this case, the first cutting step by the counterclockwise rotation (CCW) shown in FIG. 6A and the second cutting step by the clockwise rotation (CW) shown in FIG. The target shape OF can be formed on the surface Wa of the workpiece W. At this time, the portion OF0 which is not a steep step in the target shape OF is added to the processing by the counterclockwise (CCW) rotation shown in FIG. 6A in the illustrated example. It can also be added to the processing by the clockwise (CW) rotation shown in FIG.

Hereinafter, the first cutting process by the clockwise rotation (CW) shown in FIG. 5A and the second cutting process by the counterclockwise rotation (CCW) shown in FIG. A typical method will be described.
In the first cutting step shown in FIG. 7A, the tip end portion 82 of the cutting tool 80, that is, the tool axis TX is set in the −X-axis direction of the rotation axis RA by appropriately operating the second drive mechanism 94c. Starting from the outer peripheral position of W, it is moved in the + X direction to a position O through which the rotation axis RA, which is the center of the workpiece W, passes. That is, the driving range of the tip 82 is from the outer peripheral position of the workpiece W to the center position O. At this time, not only the second drive mechanism 94c but also the third drive mechanism 95c and the fourth drive mechanism 95d operate in synchronization with the first drive mechanism 94b. Thereby, the processing of the first pattern PA1 illustrated in FIG. 5A is performed on the entire surface Wa of the workpiece W while the rotation posture of the cutting tool 80 is appropriately maintained. When machining is started from the outer peripheral position of the workpiece W as shown in FIG. 7A, the rotation posture or the inclination angle α of the cutting edge 80a is adjusted in advance so that the rake face 83a extends along the standing wall OW. It is desirable to perform a preparatory operation. Thereby, the rotation posture of the cutting edge 80a can be adjusted precisely, and the machining accuracy at the outer peripheral position of the workpiece W can be ensured.
Thereafter, in the second cutting step shown in FIG. 7B, the second drive mechanism 94c is appropriately operated to move the tip 82 of the cutting tool 80 from the position O through which the rotation axis RA that is the center of the workpiece W passes. It is started and moved in the + X direction of the rotation axis RA to the outer peripheral position of the workpiece W in the + X direction. That is, the driving range of the tip 82 is from the center position O to the outer peripheral position of the workpiece W. At this time, not only the second drive mechanism 94c but also the third drive mechanism 95c and the fourth drive mechanism 95d operate in synchronization with the first drive mechanism 94b. Thereby, the processing of the second pattern PA2 illustrated in FIG. 5B is performed on the entire surface Wa of the workpiece W while the rotational posture of the cutting tool 80 or the cutting edge 80a is appropriately maintained. As a result, a target shape can be obtained on the surface Wa of the workpiece W by combining the patterns PA1 and PA2.
In this case, when moving from the step shown in FIG. 7 (A) to the step shown in FIG. 7 (B), it is desirable to slightly retract the tip 82 of the cutting tool 80 in the −Z-axis direction because the rotation direction changes. However, since it is not necessary to displace even if it retracts, it is easy to maintain the processing accuracy by the cutting tool 80. When the process shown in FIG. 7 (A) is shifted to the process shown in FIG. 7 (B), the rake face 83a of the cutting edge 80a is automatically rotated in the rotational direction or the traveling direction, even though the cutting tool 80 does not rotate as it is. Turn to Dr. That is, the direction of the cutting tool 80 is automatically reversed in a functional sense in accordance with the rotation direction. At this time, the rotational posture of the cutting tool 80 can also be adjusted. In this case, the effect of adding an inclination angle to the reversal of the blade edge 80a can be obtained.

  When switching from the process shown in FIG. 7A to the process shown in FIG. 7B, the angular relationship in the rotation direction of the workpiece W is matched, that is, the coordinates relating to the rotation angle of the machining position are switched. There is a need. That is, in the processing of FIG. 7B, the sign of the rotation angle θ in the processing of FIG. 7A is reversed and the phase is shifted by 180 °.

  The combinations of the cutting processes shown in FIGS. 7A and 7B are examples, and after the outward cutting as shown in FIG. 7B, the inward cutting shown in FIG. 7A is performed. It is also possible to perform an outward cutting process in which the inward cutting process shown in FIG. 7A is reversed in the −X direction.

  A specific example of the target shape to be formed on the workpiece W will be described with reference to FIGS. The workpiece W can be produced with high accuracy and a spiral-shaped fine structure by the above-described method, thereby obtaining a highly accurate spiral diffraction grating. The spiral shape, which is a specific example of the processed shape PA, is curved and extended so that the groove 1a or the protrusion 1b expands radially outward, and the circumferential cross section of each groove 1a or protrusion 1b is rectangular. In this case, since the surface direction of the standing wall OW of the target shape is gradually rotated clockwise as the radial position r in the radial direction R of the blade edge 80a increases, the inclination angle α of the blade edge 80a is gradually adjusted to the radial position r. Must be increased, that is, rotated clockwise. Further, the standing wall OW constituting the target-shaped protrusion 1b includes the standing wall OW1 when the workpiece W is rotating in the clockwise direction (CW) and the standing wall when the workpiece W is rotating in the counterclockwise direction (CCW). OW2, as described above, the first cutting step by clockwise rotation (CW) as exemplified in FIG. 5A and the counterclockwise direction (CCW as exemplified in FIG. 5B) ) In the second cutting step by rotation.

  With reference to FIG. 9, the whole processing method using the processing apparatus 100 of FIG. 1 is demonstrated easily. First, the main controller 98 takes in the machining shape information related to the target workpiece W from the outside or the storage unit (step S11). Next, the main controller 98 determines the locus of the machining point and the inclination of the cutting edge 80a with respect to the first cutting process adapted to the clockwise rotation (CW), which is the first rotation direction, from the machining shape information acquired in step S11. While calculating | requiring an angle, the locus | trajectory of a process point and the inclination | tilt angle of the blade edge | tip 80a are calculated regarding the 2nd cutting process adapted to rotation of a counterclockwise direction (CCW). That is, the machining shape information is machined to obtain two separated machining data relating to the first and second rotation directions (step S12). At this time, as described with reference to FIGS. 7A and 7B and the like, the consistency of the two processed data is maintained by inverting the sign of the rotation angle θ and shifting the phase by 180 °. It is. In addition, an idle swing amount is appropriately set for each processing data in order to avoid interference. Next, the main controller 98 appropriately operates the NC drive mechanism 91 via the drive controller 97 to rotate the workpiece W so as to conform to the first cutting process in the clockwise direction (CW) which is the first rotation direction. The corners and the radial position of the cutting tool 80 are initialized (step S13). Next, the main control device 98 appropriately operates the NC drive mechanism 91 via the drive control device 97, and executes the processing in the first rotational direction, that is, the first cutting step (step S14). Thereby, the processing illustrated in FIG. 5A is performed while appropriately setting the rotation posture or the inclination angle of the blade edge 80a. Next, the main control device 98 appropriately operates the NC drive mechanism 91 via the drive control device 97 to adjust the workpiece W so as to conform to the second cutting process in the counterclockwise direction (CCW) that is the second rotation direction. The rotation angle and the radial position of the cutting tool 80 are initialized (step S15). Next, the main control device 98 appropriately operates the NC drive mechanism 91 via the drive control device 97, and executes the processing in the second rotational direction, that is, the second cutting step (step S16). Thereby, the process illustrated in FIG. 5B is performed while appropriately setting the rotation posture or the inclination angle of the blade edge 80a.

  According to the machining method according to the present embodiment, the rotational posture around the tool axis TX of the cutting tool 80 is adjusted in accordance with the cutting edge position of the cutting tool 80 with respect to the workpiece W. Even when the standing wall OW having a non-uniform orientation is formed, the side portion 80b of the cutting edge 80a of the cutting tool 80 and the target shape OF can be prevented from interfering with each other, and the resulting shape can be deteriorated. Can be prevented.

  The processing method according to the present embodiment has been described above, but the processing method according to the present invention is not limited to the above. For example, in the above embodiment, the cutting tool 80 is moved back and forth in the Z-axis direction and scanned in the X-axis direction, but the workpiece W side can be moved back and forth in the Z-axis direction and scanned and moved in the X-axis direction. .

  Moreover, in the said embodiment, although the workpiece | work W side was rotated, the same process can be performed also by rotating the cutting tool 80 side, without rotating the workpiece | work W side.

  Further, for example, there is an error between the first cutting process by the clockwise (CW) rotation shown in FIG. 4A and the second cutting process by the counterclockwise (CCW) rotation shown in FIG. If it occurs, control can be performed to compensate for this, but if the unintentional step formed as a result is low, it can be removed later. As a method for removing the step, for example, a beam processing type polishing method such as GCIB (Gas Cluster Ion Beam) can be used.

  In the above, although divided into the 1st cutting process and the 2nd cutting process, it can also divide into three or more cutting processes, and these can also be performed sequentially.

In the above, the production of the spiral diffraction grating is illustrated as the processed shape PA. However, the present invention is not limited to this, and various optical elements including various surfaces, molding dies, and the like are processed by the method of the present invention. It can be produced by a method. FIG. 10 illustrates a processed shape PA in which a diffraction grating composed of a large number of protrusions extending in a stripe shape is formed in a fan-shaped region. Such an optical element can also be precisely and efficiently manufactured by the method of the present invention.
Further, the target shape to be formed on the workpiece W does not have to be limited to a rectangular cross section in the circumferential direction as shown in FIG. 8B or the like, and the cross section in the circumferential direction may be a triangle or a sawtooth shape. . In this case, it becomes possible to complete the processing of the workpiece W only by the first cutting step shown in FIG.

  A ... locus, TX ... tool axis, RA ... rotary axis, W ... work, OF ... target shape, OW ... standing wall, OW1 ... standing wall, OW2 ... standing wall, 80 ... cutting tool, 80b ... side, 81a ... tip part 82 ... tip portion, 81a ... tip portion, 81b ... shank portion, 82 ... tip portion, 83a ... rake face, 83b, 83c ... relief surface, 91 ... NC drive mechanism, 94b ... first drive mechanism, 94c ... second Drive mechanism, 95a ... work spindle, 95c ... third drive mechanism, 95c ... third drive mechanism, 97 ... drive control device, 98 ... main control device, 100 ... processing device

Claims (8)

The cutting edge which is the position of the cutting edge of the cutting tool relative to the workpiece by moving the cutting tool relatively in the radial direction of the workpiece while rotating the workpiece with respect to the cutting tool having a rake face and a flank on the cutting edge. A machining method for cutting a workpiece by displacing the cutting tool in a direction in which a tool axis passes through the cutting edge according to a position,
A processing method comprising adjusting a rotational posture of the cutting tool around the tool axis in accordance with the cutting edge position of the cutting tool with respect to a workpiece.   Based on the relative rotation angle of the workpiece with respect to the cutting edge of the cutting tool and the radial position with respect to the rotation axis of the cutting edge with respect to the workpiece, the radial direction around the tool axis of the cutting edge is referred to The processing method according to claim 1, wherein the inclination angle is adjusted.   The machining method according to claim 2, wherein an inclination angle of the cutting edge around the tool axis is changed in a range of ± 45 ° at the maximum.   The processing method according to any one of claims 1 to 3, wherein a rotation speed of the workpiece with respect to the cutting tool is 500 rpm or less.   The machining method according to any one of claims 1 to 4, wherein a rotational posture of the cutting edge around the tool axis is changed along a vertical wall-shaped portion formed on the workpiece. While rotating the workpiece in one first rotation direction with respect to the cutting edge, at least a vertical wall-shaped part having a predetermined inclination angle or more with respect to the traveling direction of the cutting edge is selectively processed by an operation of retracting the cutting edge,
While rotating the workpiece in the other second rotation direction with respect to the cutting edge, at least a vertical wall-shaped part having a predetermined inclination angle or more with respect to the traveling direction of the cutting edge is selectively processed by an operation of retracting the cutting edge,
The operation of cutting or retracting the cutting edge of the non-standing wall-shaped portion excluding the standing wall-shaped shape portion having a predetermined inclination angle or more accompanying the rotation in any of the first and second rotation directions. The processing method according to any one of claims 1 to 5, wherein the processing method is performed.   The machining method according to any one of claims 5 and 6, wherein a step amount of the standing wall-shaped portion formed on the workpiece is equal to or less than a maximum amplitude of an axial position of the cutting tool. A cutting tool having a rake face and a flank face at the cutting edge;
A first drive mechanism for rotating the workpiece relative to the cutting tool relative to a rotation axis;
A second drive mechanism for moving the cutting tool relatively in a radial direction perpendicular to the rotation axis;
A third drive mechanism for displacing the cutting tool in a direction in which a tool axis passes through the cutting edge of the cutting tool in accordance with a cutting edge position that is a position of the cutting edge of the cutting tool with respect to a workpiece;
A fourth drive mechanism for adjusting a rotational attitude of the cutting tool around the tool axis in accordance with the cutting edge position of the cutting tool with respect to a workpiece;
A processing apparatus comprising:

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