JPWO2016093300A1 - Processing method and processing apparatus - Google Patents

Abstract

Provided is a machining method capable of preventing a cutting tool and a target shape from interfering with each other and causing shape deterioration even when a steep standing wall whose direction is not uniform along the rotation direction is formed. During the rotation in the first rotation direction (first cutting step), the steep wall (WO1) having a predetermined inclination angle or more with respect to the traveling direction is selectively processed by the operation of retracting the cutting tool (80), and the second rotation direction In the rotation (second cutting step), the rising direction differs with respect to the circumferential direction of the workpiece (W) with respect to the standing wall (WO1) processed during the rotation in the first rotation direction, and a predetermined inclination angle or more with respect to the traveling direction. The steep standing wall (WO2) is selectively processed by the operation of retracting the cutting tool (80). For this reason, it is not necessary to machine a steep standing wall formed by protruding the cutting tool (80) during both rotations in the first and second rotation directions, and the back surface of the cutting tool (80). It is possible to prevent the side wall and the top of the standing wall (WO2) from interfering with each other and shape deterioration.

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 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. This tool servo processing controls the cutting edge position such as the cutting depth of the cutting tool according to the rotation angle of the workpiece, and projects or retracts the cutting tool according to the rotation direction or circumferential position of the workpiece. As a result, non-rotationally symmetric processing surfaces such as off-axis surfaces and free-form surfaces can be formed.
Tool servo processing includes Fast Tool Servo (Fast Tool Servo or FTS, a method of driving and controlling a tool base with a tool attached with a piezoelectric element) and Slow Tool Servo (Slow Tool Servo or STS, a machine tool with a tool base on it) There are two known methods of driving the shaft.

  However, even when tool servo machining as described above is used, when there is a steep standing wall in the target shape after machining the workpiece, the cutting tool may interfere with the target shape and high-precision machining may not be performed. . In other words, a steep standing wall that is formed in the direction in which the cutting tool is retracted (rise direction) is continuous with respect to the tool traveling direction determined by the rotation direction of the work spindle that rotates the work and the radial direction of the machining point. For the processing of the target shapes that are arranged side by side, there is no particular problem in processing. However, with respect to the formation of a target shape that has a steep standing wall that is formed in a direction in which the cutting tool protrudes (downward direction) with respect to the tool traveling direction, the cutting is performed when the cutting tool is cut. The back side of the tool interferes with the apex of the standing wall to cause shape deterioration.

  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 micromachining method does not presuppose a shape having a steep standing wall that is formed in the direction in which the cutting tool is projected, and seems to cause the same problem as in the case of the tool servo machining.

  Further, as a cutting method, a method of performing a fine cutting process by turning a workpiece and displacing a cutting tool in a cutting direction is known (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 directly applied to the 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 forming a steep standing wall whose direction is not uniform along the rotation direction during processing, the cutting tool and the target shape An object of the present invention is to provide a processing method and a processing apparatus that can prevent shape interference due to interference.

  In order to achieve the above object, a machining method according to the present invention is one of forward rotation and reverse rotation of a workpiece relative to the cutting tool using a cutting tool having a rake face and a flank face. While rotating in the first rotation direction and the second rotation direction which is the other, the cutting tool is moved relatively in the radial direction, the relative rotation direction and rotation angle of the workpiece, and the radial position of the cutting tool, A cutting method for cutting a workpiece by adjusting the axial position of the cutting tool according to the above, and at the time of rotation in the first rotation direction, at least a standing wall shape having a predetermined inclination angle or more with respect to the traveling direction of the cutting tool The shape portion of the workpiece is selectively machined by the operation of retracting the cutting tool, and when rotating in the second rotation direction, the circumferential portion of the workpiece is related to the standing wall-like shape portion processed during the rotation in the first rotation direction. Standing up The vertical wall-shaped portion having a different inclination direction and at least a predetermined inclination angle with respect to the advancing direction of the cutting tool is selectively machined by the operation of retracting the cutting tool, and either of the first and second rotational directions is selected. In association with or independently of the rotation of the workpiece, the non-standing wall-shaped portion excluding the standing wall-shaped portion having a predetermined inclination angle or more is processed by an operation of cutting or retracting the cutting tool.

  In the above-described processing method, when rotating in the first rotation direction, a vertical wall-shaped portion having a predetermined inclination angle or more (steeply rising type) with respect to the traveling direction is selectively processed by the operation of retracting the cutting tool, When rotating in the rotational direction, a vertical wall-shaped portion having a predetermined inclination angle or more (steeply rising type) with respect to the traveling direction is selectively processed by the operation of retracting the cutting tool. During any rotation, it is no longer necessary to machine the steep standing wall that is formed by protruding the cutting tool, preventing the back side of the cutting tool and the top of the standing wall from interfering with each other to prevent shape deterioration. it can.

  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, and a first drive mechanism for rotating the workpiece relative to the cutting tool relative to the rotation axis. A second drive mechanism that moves the cutting tool relatively in a radial direction perpendicular to the rotation axis, and a cutting tool that is relatively parallel to the rotation axis while being synchronized with the first and second drive mechanisms. A processing apparatus comprising a third drive mechanism to be moved and a control unit that controls the operation of the first to third drive mechanisms, wherein the control unit operates the first drive mechanism to rotate the workpiece forward and backward. While rotating to the 1st rotation direction which is one side among rotation, and the 2nd rotation direction which is the other, a 2nd drive mechanism is operated, a cutting tool is moved to radial direction, and a 3rd drive mechanism is made into 1st. And the relative movement of the workpiece by operating in synchronization with the second drive mechanism. The cutting tool is adjusted by adjusting the axial position of the cutting tool in accordance with the rotational direction and angle of rotation and the radial position of the cutting tool, and at least the cutting tool advances during the rotation in the first rotational direction. A vertical wall-shaped portion that is selectively machined by an operation of retracting a cutting tool with a predetermined inclination angle or more with respect to the direction, and is processed when rotating in the first rotational direction when rotating in the second rotational direction. The rising direction differs with respect to the circumferential direction of the workpiece with respect to the portion, and at least the vertical wall-shaped shape portion having a predetermined inclination angle or more with respect to the traveling direction of the cutting tool is selectively processed by the operation of retracting the cutting tool, Along with the rotation in any of the first and second rotation directions, the cutting tool is cut or retracted in the non-standing wall-shaped portion excluding the standing wall-shaped portion having a predetermined inclination angle or more. Processed by the work.

  In the above processing apparatus, when rotating in the first rotational direction, the vertical wall-shaped portion having a predetermined inclination angle or more with respect to the traveling direction is selectively processed by the operation of retracting the cutting tool, and proceeds during the rotation in the second rotational direction. Since the vertical wall-shaped portion with a predetermined inclination angle or more with respect to the direction is selectively machined by the operation of retracting the cutting tool, it is formed by protruding the cutting tool during both rotations in the first and second rotation directions. It is not necessary to machine such a steep standing wall, and it is possible to prevent the rear surface side of the cutting tool and the apex of the standing wall from interfering with each other to cause shape deterioration.

It is a block diagram explaining the processing apparatus concerning an embodiment. 2A and 2B are a side view and a plan view of the cutting tool. It is a conceptual diagram explaining the processing method of embodiment. 4A is a conceptual cross-sectional view for explaining processing by rotation in the first rotation direction, and FIG. 4B is a conceptual cross-sectional view for explaining processing by rotation in the second rotation direction. 5A and 5B are conceptual cross-sectional views for explaining a modified example in which FIGS. 4A and 4B are changed. 6A is a plan view for explaining processing by rotation in the first rotation direction, and FIG. 6B is a plan view for explaining processing by rotation in the second rotation direction. It is a flowchart explaining the manufacturing method using the apparatus of FIG. 8A and 8B are diagrams for explaining a specific processing example.

  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 two-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 backward at a desired speed around a rotation axis RA extending in parallel with the Z axis and extending horizontally. The rotation angle or the rotation attitude of 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 the third drive mechanism 95c, and the third drive mechanism 95c supports the cutting tool 80. The second drive mechanism 94c supports the third drive mechanism 95c and the cutting tool 80 and extends them along the horizontal X-axis direction and the vertical Y-axis direction (that is, the radial direction perpendicular to the rotation axis RA). It can be moved to a desired position at a desired speed. The third drive mechanism 95c is a support base member, and the cutting tool 80 is moved to a desired position along the horizontal Z-axis direction (that is, an axial direction parallel to the rotation axis RA) at a desired speed. It can be moved forward and backward. The drive control device 97 can monitor the cutting tool 80 or its cutting edge position via the second drive mechanism 94c and the like.

  With reference to FIG. 2A and 2B, the shape of the principal part of the cutting tool 80 is demonstrated. The cutting tool 80 includes 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 portion 81a, an angle γ1 formed by the first clearance surface 83b with respect to a surface perpendicular to the tool axis AX extending in the Z-axis direction is referred to as a first clearance angle, and a second clearance with respect to the surface perpendicular to the tool axis AX. An angle γ2 formed by the surface 83c is referred to as a second clearance angle. 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 is set to 10 to 60 °, the second clearance angle γ2 is set to 45 to 60 °, and the blade thickness (width t) is set to about 0.05 mm or more. It was. Although the illustrated tip portion 81a has a V-shaped tip shape, a semicircular or sword-tip shape can be employed 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, 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 forward and reverse. When the work spindle 95a is viewed in the + Z axis direction, the clockwise rotation (CW) is the forward rotation, and the work spindle 95a is viewed in the + Z axis direction. Thus, the counterclockwise (CCW) rotation is defined as reverse rotation. 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 82 of the cutting tool 80 is first placed on the rotation axis RA by the second drive mechanism 94c, and the tip 82 is moved (feeded) in the radial X-axis direction at a relatively low speed. Operation). In parallel with this, the third drive mechanism 95c moves the distal end portion 82 of the cutting tool 80 forward and backward at a relatively high speed in the Z-axis direction or the tool axis AX 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 advance and retreat, the Z position of the cutting tool 80, in other words, the axial position of the cutting tool 80 depends on the rotation direction and rotation angle of the work spindle 95a or the work W and the radial position of the cutting tool 80. Adjusted. 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 a plane, a spherical surface, a free curved surface, a step, and the like, as well as a combination of these.

  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 a step of operating the first and second drive mechanisms 94b, 94c, the third drive mechanism 95c, and the like. More specifically, the main control device 98 A design shape or a target shape that is a corrected shape corrected to realize this is received as machining shape information. This machining shape information includes, for example, the axial position 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 at the radial position. Yes. 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. The tip position 82 of the cutting tool 80 can be moved along the target shape while rotating relative to the workpiece W.

  The main control device 98 prepares a machining process divided into two cutting processes corresponding to forward and reverse rotations in consideration of machining convenience by the cutting tool 80 having the shape shown in FIG. 2A. 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, and the axial position 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 a cutting process that is normally performed in a lump as a first cutting process using forward rotation of the work spindle 95a and a second cutting process using reverse rotation of the work spindle 95a. Divided into two. Specifically, for 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 82 of the cutting tool 80 is calculated, For the second cutting process in which the spindle 95a is rotated in the counterclockwise direction (CCW) that is the second rotation direction, the locus of the machining point corresponding to the tip portion 82 of the cutting tool 80 is calculated, and these are individually stored in the storage unit. store. 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, the basic concept of the method for processing the workpiece W will be described with reference to FIGS. 3, 4A and 4B and the like.

  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, for example, in the clockwise direction, the tip portion 82 of the cutting tool 80 located at the radial position of the radius r from the rotation axis RA is relative to the workpiece W in the counterclockwise direction. It rotates in the general direction of travel Dr or the direction of rotation. At this time, the relative rotation angle of the tip portion 82 of the cutting tool 80 is θ. That is, the locus A of the tip portion 82 represented by the cylindrical coordinates (r, θ, zt) is set by controlling the axial position that is the coordinate value zt of the tip portion 82 of the cutting tool 80 in the Z-axis direction. The shape to be transferred to the surface Wa of the workpiece W can be arbitrarily set. Here, there is no particular problem as long as the change of the coordinate value zt, which is the axial position of the tip portion 82 of the cutting tool 80, corresponds to a slowly changing path as in the conventional optical surface. If the coordinate value zt of the portion 82 gives a path that changes abruptly, especially when machining is performed by moving forward in the Z-axis direction so that the tip 82 is cut, the tip 82 of the cutting tool 80 is used. Other portions, that is, the second flank (back surface) 83c and the like interfere with the target shape to be formed on the workpiece W, and shape deterioration occurs. Such a phenomenon remarkably occurs when the slope of the lower step of the target shape has a steeper slope than the second clearance angle γ2.

  4A and 4B are cross-sectional views for explaining a technique for avoiding shape deterioration caused by interference with a target shape to be formed on the workpiece W except for the tip portion 82 of the cutting tool 80. 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.

  4A and 4B, when rotating in the clockwise direction (CW) which is the first rotation direction, the standing wall WO1 which is a standing wall-like shape portion having a predetermined inclination angle or more with respect to the traveling direction Dr of the cutting tool 80 is cut. The tool 80 is selectively processed by the operation of retracting the tool 80. Further, when rotating in the counterclockwise direction (CCW) which is the second rotation direction, the cutting tool 80 is retracted into the standing wall WO2 which is a standing wall-like shape portion having a predetermined inclination angle or more with respect to the traveling direction Dr of the cutting tool 80. Selectively process by movement. Further, in association with the rotation in the clockwise direction (CW) or counterclockwise direction (CCW), a portion OF0 that is not a steep step, which is a non-standing wall-shaped portion excluding the standing walls WO1 and WO2 having a predetermined inclination angle or more, is cut. Machining is performed by the operation of cutting or retracting the tool 80. Here, the predetermined inclination angle is larger than the maximum clearance angle of the cutting tool 80 (second clearance angle γ2 in the present embodiment). Thereby, it can prevent that a part corresponding to the maximum clearance angle of the cutting tool 80 interferes with the vertex of standing wall WO1, WO2, and shape deterioration arises.

  The step amount of the standing wall-shaped portion (standing walls WO1 and WO2) is less than or equal to the maximum amplitude of the axial position of the cutting tool 80. The maximum amplitude of the cutting tool 80 in the axial direction, that is, the maximum amplitude of the tool servo is generally 1000 μm or less in FTS and 20 mm or less in STS. In the range of microfabrication, 1000 μm or less is common.

As shown in FIG. 4A, when the workpiece W is rotating in the clockwise direction (CW), which is the first rotation direction, even if there is a steep step in the target shape OF, the rotation direction or progress of the cutting tool 80 If it is a level | step difference which goes up in the direction Dr, precise processing will be attained only by retracting the cutting tool 80 in the −Z-axis direction and retracting it. That is, the flank surfaces 83b and 83c of the cutting tool 80 and the standing wall WO1 of the target shape OF do not interfere with each other and can be processed without deteriorating 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 WO2 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 WO2 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 WO2 interferes with the cutting tool 80 occurs when the inclination angle Δ of the standing wall WO2 is larger than the second clearance angle γ2 of the tip portion 81a of the cutting tool 80. However, when the width t of the first clearance surface 83b of the tip portion 81a is relatively wide, the same applies when the inclination angle Δ of the standing wall WO2 is larger than the first clearance angle γ1 corresponding to the first clearance surface 83b. Cause interference problems.

  Therefore, as shown in FIG. 4B, the workpiece W is rotated in the counterclockwise direction (CCW), which is the second rotation direction, about a part of the same locus A as shown in FIG. 4A. In this case, the step of the standing wall WO2 is reversed. That is, the standing wall WO2 that is a step that suddenly falls in the rotational direction or the traveling direction Dr by the clockwise (CW) rotation shown in FIG. 4A is rotated by the counterclockwise (CCW) rotation shown in FIG. 4B. It becomes a step that rises rapidly. As a result, the standing wall WO2 can be formed by operating the cutting tool 80 so as to be retracted in the −Z-axis direction and performing cutting, and the apex of the standing wall WO2 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 WO2 from being processed with a dull shape.

  As a result, if the processing by the clockwise (CW) rotation shown in FIG. 4A and the processing by the counterclockwise (CCW) rotation shown in FIG. 4B are combined, the target shape OF is formed on the surface Wa of the workpiece W. You can see that you can. At this time, in the example shown in the drawing, 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 (CW) rotation shown in FIG. 4A. Yes. That is, in the first cutting step shown in FIG. 4A, the pattern PA1 including the standing wall WO1 in the forward rotation direction and the portion (non-standing wall-shaped portion) OF0 that is not a steep step is processed. As a result, during the clockwise rotation (CW), not only the standing wall-shaped portion that rises sharply but also the non-standing wall-shaped portion is processed. Then, in the next second cutting step shown in FIG. 4B, the pattern PA2 including the upright wall WO2 in the reverse rotation 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. 4B. Furthermore, the pattern PA1 of FIG. 4A is not limited to the pattern PA1 including the single standing wall WO1, and may include a plurality of standing walls WO1, but the second type of the standing wall WO1 is of the second type. When the standing wall WO2 exists, the periphery of the standing wall WO2 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 processing shown in FIG. 4A and the processing shown in FIG. 4B cannot generally be performed simultaneously because the cutting tool 80 needs to be reversed with respect to the workpiece W. Therefore, even for a series of target shapes OF, it is necessary to individually switch and perform processing by clockwise (CW) rotation and counterclockwise (CCW) rotation. 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. 4A to the second cutting step shown in FIG. 4B, it is usually necessary to shift the tip 82 of the cutting tool 80 in the Z-axis direction. When it becomes larger, it becomes difficult to maintain the positional accuracy of the tip end portion 82. For this reason, it is desirable that the amount of shift or shift in the axial direction of the tip end portion 82 when switching from the processing shown in FIG. 4A to the processing shown in FIG. 4B is about 20 nm or less. That is, the axial displacement of the cutting tool 80 when switching from the clockwise direction (CW) to the counterclockwise direction (CCW) is preferably 20 nm or less. Thereby, it is hard to produce an error when switching the rotation direction, and the machining accuracy of the workpiece W can be increased. However, even if the amount of shift 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.

  In addition, when the first cutting step shown in FIG. 4A is performed, it is necessary not to process the standing wall WO2 having a reverse level difference or the front portion (standing wall-shaped shape portion) associated therewith. That is, in order to prevent the standing wall WO2 from being deteriorated, when the cutting tool 80 passes through the standing wall-shaped portion including the standing wall WO2, the cutting tool 80 is retracted with a sufficient margin in the −Z-axis direction. 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 WO2. However, when there are a plurality of standing walls WO2, the margin is set to the maximum step amount or more. 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. In a specific embodiment, it is 1000 μm or less in FTS and 20 mm or less in STS. Conversely, when the second cutting step shown in FIG. 4B is performed, it is necessary not to process the standing wall WO1 having the opposite step and the front portion (standing wall-shaped shape portion) associated therewith. For this reason, when the cutting tool 80 passes through the standing wall-shaped portion including the standing wall WO1, the swinging K is performed to retract the cutting tool 80 with a sufficient margin in the −Z axis direction.

  5A and 5B show a modification of the machining operation shown in FIGS. 4A and 4B. In this case, the processing by the counterclockwise (CCW) rotation shown in FIG. 5A precedes, and the processing by the clockwise (CW) rotation shown in FIG. 5B continues. In this case, the counterclockwise (CCW) rotation is forward rotation, and the clockwise (CW) rotation is reverse rotation. Also in this case, the first cutting process by the counterclockwise (CCW) rotation shown in FIG. 5A and the second cutting process by the clockwise (CW) rotation shown in FIG. 5B are combined to form the surface Wa of the workpiece W. The target shape OF can be formed. At this time, the portion OF0 of the target shape OF which is not a steep step is added to the processing by the counterclockwise (CCW) rotation shown in FIG. 5A in the illustrated example, but is shown in FIG. 5B. It can also be performed in addition to processing by clockwise rotation (CW).

  Hereinafter, a specific method for continuously performing the first cutting step by the clockwise (CW) rotation shown in FIG. 4A and the second cutting step by the counterclockwise (CCW) rotation shown in FIG. 4B will be described. The clockwise rotation (CW) that is the first rotation direction and the counterclockwise rotation (CCW) that is the second rotation direction are independently performed, and the radial position of the cutting tool 80 is the workpiece It changes so as to continuously increase or decrease within a range from the center position on the relative rotation axis of W to the outer peripheral position. As a result, the entire machining can be completed and the machining can be simplified by executing the clockwise (CW) machining and the counterclockwise (CCW) machining only once.

In the first cutting step shown in FIG. 6A, the tip end portion 82 of the cutting tool 80 is started from the outer peripheral position of the workpiece W in the −X-axis direction of the rotation axis RA by appropriately operating the second drive mechanism 94c. Then, the workpiece is moved in the + X direction to a position O through which the rotation axis RA that 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, the first and third drive mechanisms 94b and 95c also operate in synchronization with the second drive mechanism 94c. Thereby, the processing of the first pattern PA1 conceptually shown in FIG. 4A is performed on the entire surface Wa of the workpiece W. Thereafter, in the second cutting step shown in FIG. 6B, the tip end portion 82 of the cutting tool 80 is started from a position O through which the rotation axis RA that is the center of the workpiece W passes by appropriately operating the second drive mechanism 94c. Then, the rotation axis RA is moved in the + X-axis direction 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, the first and third drive mechanisms 94b and 95c also operate in synchronization with the second drive mechanism 94c. As a result, the entire surface Wa of the workpiece W is processed with the second pattern PA2 conceptually shown in FIG. 4B, and as a result, both the patterns PA1 and PA2 are combined to achieve the target on the surface Wa of the workpiece W. The shape to be obtained is obtained.
In this case, when moving from the step shown in FIG. 6A to the step shown in FIG. 6B, it is desirable to slightly retract the tip 82 of the cutting tool 80 in the −Z-axis direction because the rotation direction changes. Therefore, the machining accuracy by the cutting tool 80 can be easily maintained. When the process shown in FIG. 6A is shifted to the process shown in FIG. 6B, the rake face 83a of the tip portion 81a automatically changes the rotational direction or the traveling direction Dr as the cutting direction of the cutting tool 80 is changed. Turn to. That is, the direction of the cutting tool 80 is automatically reversed according to the rotation direction.

  When switching from the process shown in FIG. 6A to the process shown in FIG. 6B, it is necessary to match the angular relationship in the rotation direction of the workpiece W, that is, to change the coordinates related to the rotation angle of the machining position. That is, in the processing of FIG. 6B, the sign of the rotation angle θ in the processing of FIG. 6A is reversed and the phase is shifted by 180 °. In this case, it is possible to match both processing contents while separating the clockwise (CW) rotation and the counterclockwise (CCW) rotation.

  The combination of the cutting processes shown in FIGS. 6A and 6B is an exemplification, and after the outward cutting as shown in FIG. 6B, the inward cutting shown in FIG. 6A is performed, or the inward cutting shown in FIG. 6A is performed. It is also possible to perform outward cutting by reversing the rotation in the −X direction. In this case, an operation for reversing the direction of the cutting tool 80 is required.

  With reference to FIG. 7, 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 calculates the locus of the machining point with respect to the first cutting process adapted to the clockwise rotation (CW), which is the first rotation direction, from the machining shape information captured in step S11. The locus of the machining point is calculated for the second cutting process adapted to the counterclockwise (CCW) rotation. 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. 6A and 6B, the consistency of the two processed data is maintained by inverting the sign of the rotation angle θ and shifting the phase by 180 °. 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 process illustrated in FIG. 4A is performed. 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. 4B is performed.

  FIG. 8A is a diagram showing an example of processing using the processing apparatus 100 of FIG. In this case, the workpiece W is processed into a special retardation plate. Here, a dark part shows a low area | region and a bright part shows a high area | region. That is, the pair of locations B where the dark portion and the bright portion form a clear boundary indicate steep steps or standing walls. The steps formed in the pair of places B are symmetrical along the left and right sides of the drawing, that is, along the circumferential direction Dc, and therefore the rising directions are different from each other with respect to the circumferential direction Dc. However, by carrying out the processing method of the present embodiment, a steep and precise standing wall can be formed as shown in the point B.

  FIG. 8B is a diagram illustrating another processing example. In this case, a phase difference structure is formed only on a local portion of the entire circular surface of the workpiece W. Also in this case, the steps formed at the pair of locations B are symmetrical along the left and right sides of the drawing, that is, along the circumferential direction Dc, and therefore the rising directions are not different with respect to the circumferential direction Dc. However, by carrying out the processing method of the present embodiment, a steep and precise standing wall can be formed as shown in the point B.

  According to the processing method according to the present embodiment, during the rotation in the first rotation direction (first cutting step), the steep wall WO1 having a predetermined inclination angle or more with respect to the traveling direction is selectively selected by the operation of retracting the cutting tool 80. During the rotation in the second rotation direction (second cutting step), the steep standing wall WO2 having a predetermined inclination angle or more with respect to the traveling direction is selectively processed by the operation of retracting the cutting tool 80. For this reason, it is not necessary to process a steep standing wall formed by protruding the cutting tool 80 during both rotations in the first and second rotation directions, and the back surface side and the standing wall WO2 of the cutting tool 80 are eliminated. It is possible to prevent the deterioration of the shape due to interference with the apex.

  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.

  In addition, for example, when an error occurs 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. 4B, this is compensated for. Such control can be performed, but if the unintentional step formed as a result is low, it can be removed afterwards. 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. For example, a non-standing wall-shaped portion can be processed independently of the first and second cutting steps.

  In the above, the production of the retardation film has been exemplified. However, the present invention is not limited to this, and various optical elements including various surfaces, molding dies, and the like can be produced by the above processing method.

Claims (8)

Using a cutting tool having a rake face and a flank face, the workpiece is moved relative to the cutting tool in a first rotation direction that is one of forward rotation and reverse rotation and a second rotation direction that is the other. While rotating, the cutting tool is relatively moved in the radial direction, and the axial position of the cutting tool is set according to the relative rotation direction and rotation angle of the workpiece and the radial position of the cutting tool. A machining method for cutting a workpiece by adjusting,
When rotating in the first rotation direction, at least a vertical wall-shaped portion having a predetermined inclination angle or more with respect to the traveling direction of the cutting tool is selectively processed by an operation of retracting the cutting tool,
When rotating in the second rotation direction, the rising direction differs with respect to the circumferential direction of the workpiece with respect to the standing wall-shaped portion processed during the rotation in the first rotation direction, and at least predetermined with respect to the traveling direction of the cutting tool A vertical wall-shaped shape part having an inclination angle or more is selectively processed by the operation of retracting the cutting tool,
Along with or independently of the rotation in one of the first and second rotational directions, the cutting tool is cut into a non-standing wall-shaped shape portion excluding the standing wall-shaped shape portion having the predetermined inclination angle or more. Machining method to process by moving or retracting.   The processing method according to claim 1, wherein the non-standing wall-shaped portion is processed during the rotation in the first rotation direction.   The processing method according to any one of claims 1 and 2, wherein the predetermined inclination angle of the vertical wall-shaped portion is larger than a maximum clearance angle of the cutting tool.   The processing according to any one of claims 1 to 3, wherein an amount of axial displacement of the cutting tool when switching from one of the first and second rotational directions to the other is 20 nm or less. Method.   The processing method according to any one of claims 1 to 4, wherein a step amount of the standing wall-shaped portion is equal to or less than a maximum amplitude of an axial position of the cutting tool.   2. When switching from one of the first and second rotation directions to the other, the direction of the cutting tool is reversed to correspond to the rotation direction, and the angular relationship in the rotation direction of the workpiece is matched. The processing method as described in any one of -5.   The rotation in the first rotation direction and the rotation in the second rotation direction are independently performed, and the radial position of the cutting tool is set to the outer peripheral position from the center position on the relative rotation axis of the workpiece. The processing method according to any one of claims 1 to 5, wherein the processing method changes so as to continuously increase or decrease within a range up to. A cutting tool having a rake face and a flank; a first drive mechanism for rotating a work relative to the cutting tool around a rotation axis; and a radial direction perpendicular to the rotation axis of the cutting tool. A second drive mechanism that moves relative to the first drive mechanism, a third drive mechanism that moves the cutting tool relatively in an axial direction parallel to the rotation axis, in synchronization with the first and second drive mechanisms, A processing device including a control unit that controls the operation of the first to third drive mechanisms,
The control unit operates the first drive mechanism to rotate the workpiece in a first rotation direction which is one of forward rotation and reverse rotation and a second rotation direction which is the other, and the second drive mechanism. To move the cutting tool in the radial direction, and operate the third drive mechanism in synchronization with the first and second drive mechanisms, and the relative rotation direction and rotation angle of the workpiece and the Cutting is performed by adjusting the axial position of the cutting tool according to the radial position of the cutting tool,
When rotating in the first rotation direction, at least a vertical wall-shaped portion having a predetermined inclination angle or more with respect to the traveling direction of the cutting tool is selectively processed by an operation of retracting the cutting tool,
When rotating in the second rotation direction, the rising direction differs with respect to the circumferential direction of the workpiece with respect to the standing wall-shaped portion processed during the rotation in the first rotation direction, and at least predetermined with respect to the traveling direction of the cutting tool A vertical wall-shaped shape part having an inclination angle or more is selectively processed by the operation of retracting the cutting tool,
A cutting tool is cut into a non-standing wall-like shape portion excluding the standing wall-like shape portion having a predetermined inclination angle or more, accompanying or independently of rotation in any of the first and second rotation directions. A processing device that processes by moving or retracting.

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