Mold manufacturing method

Abstract

To provide a manufacturing method of a mold that makes it possible, in a recess to be cut first, to restrain a radius of curvature of the recess in one direction from falling outside a standard value in comparison with the case where the radius of curvature of the recess in the one direction is larger than a radius of curvature of the recess in a direction intersecting the one direction.SOLUTION: In a mold manufacturing method, when cutting a plurality of spherical coronal recesses 102 on a working surface 100A by moving, relative to the working surface 100A, a cutting edge 20A of an end mill 20 rotating around a rotary shaft 21 angled sharply with respect to the working surface 100A of a work 100, the radius of curvature of the recess 102 to be cut first is determined by setting the position of the cutting edge 20A of the end mill 20 so that the radius of curvature in the Y direction projected from the cutting edge 20A of the end mill 20 on the working surface 100A is smaller than the radius of curvature in the X direction, and cutting of the recess 102 is started.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a mold. [Background technology]

[0002] The following Patent Document 1 discloses a method for manufacturing a mold in which a mold for molding a microlens array is placed on the placement surface of a holding table, and multiple concave curved surfaces are formed by cutting the mold with an end mill, wherein the end mill cuts the mold while rotating around its central axis, and there are two or more combinations of a circumferential placement angle of the placement surface centered on an axis perpendicular to the placement surface relative to the central axis, and an angle of the central axis relative to the placement surface, and one of the combinations is selected for each of the multiple concave curved surfaces to be formed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-043444 Summary of the Invention [Problem to be solved by the invention]

[0004] For example, when a mold having a plurality of recesses is manufactured by cutting, there is a concern that the radius of curvature of the recesses may deviate from the standard value during the process of cutting the recesses.

[0005] The purpose of the present disclosure is to obtain a method for manufacturing a mold that can prevent the radius of curvature of a recess from falling outside the standard value, compared to when the radius of curvature of the recess in one direction, which is cut first, is larger than the radius of curvature of the recess in an intersecting direction that intersects with the one direction. [Means for solving the problem]

[0006] In the method for manufacturing a mold according to the first embodiment, when the cutting edge of a tool that rotates around an axis inclined at an acute angle to the machining surface of the mold is moved relative to the machining surface to cut multiple spherical crown-shaped recesses into the machining surface, the cutting edge is positioned so that the radius of curvature of the recesses to be cut first is smaller in one direction when the tool is projected onto the machining surface than in an intersecting direction that intersects with the one direction, and then the cutting process is started.

[0007] A mold manufacturing method according to a second aspect is a mold manufacturing method according to the first aspect, in which the position of the cutting edge is set so that the radius of curvature of the recess in the one direction is at the lower limit of a standard value, and then the radius of curvature of the recess in the intersecting direction is set within the standard value.

[0008] A third aspect of the mold manufacturing method is a mold manufacturing method according to the second aspect, in which the setting of the position of the cutting edge so that the radius of curvature of the recess in the intersecting direction falls within the standard value is the setting of the mounting position of the tool relative to a rotation means that rotates the tool.

[0009] A fourth aspect of the mold manufacturing method is the mold manufacturing method described in the third aspect, in which the mounting position of the tool relative to the rotation means is set so that the position of the cutting edge of the tool becomes larger.

[0010] A fifth aspect of the method for manufacturing a mold is a method for manufacturing a mold according to any one of the first to fourth aspects, wherein the mold material constituting the mold has a surface treatment layer formed thereon that is primarily composed of metal and has a thickness greater than the depth of the recesses, and the recesses are formed in the surface treatment layer.

[0011] A sixth aspect of the method for manufacturing a mold is a method for manufacturing a mold described in any one of the first to fifth aspects, in which, when forming one recess, the cutting edge of the tool is moved in a spiral pattern relative to the mold material constituting the mold in a direction from the outer periphery of the recess toward the center, or from the center of the recess toward the outer periphery.

[0012] The mold manufacturing method according to the seventh aspect is a mold manufacturing method according to any one of the first to sixth aspects, in which after rough machining of all of the recesses with a first tool, the tool is replaced and finish machining of all of the recesses is performed with a second tool. [Effects of the Invention]

[0013] According to the mold manufacturing method of the first aspect, it is possible to prevent the radius of curvature of the recess from falling outside the standard value, compared to when the radius of curvature of the recess in one direction in the recess that is cut first is larger than the radius of curvature of the recess in the intersecting direction that intersects with the one direction.

[0014] According to the mold manufacturing method of the second aspect, the position of the cutting edge can be set more easily than when the position of the cutting edge is set only once so that the radius of curvature of the recess in the intersecting direction is within the standard value.

[0015] According to the manufacturing method of the mold of the third aspect, the position of the cutting edge of the tool can be set more easily than when the attachment portion of the tool is moved.

[0016] According to the mold manufacturing method of the fourth aspect, the radius of curvature in one direction in the recess cut first is more likely to be smaller than the radius of curvature in the intersecting direction that intersects with the one direction, compared to when the position of the cutting edge of the tool is set so that the rotational diameter of the cutting edge is smaller.

[0017] According to the method for manufacturing a mold according to the fifth aspect, corrosion of the mold material can be suppressed compared to when the mold material is exposed to the outside.

[0018] According to the method for manufacturing a mold of the sixth aspect, the waviness of the surface of the recess can be reduced compared to when the cutting edge of the tool is moved relative to the metal material in the radial direction of the recess.

[0019] According to the mold manufacturing method of the seventh aspect, the surface precision of the recess is better than when a single tool is used to finish machining the recess. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a perspective view showing a processing device to which a mold manufacturing method according to a first embodiment is applied. [Figure 2] FIG. 10 is a perspective view showing a state in which a recess is cut into a workpiece by an end mill of a processing device. [Figure 3] FIG. 10 is a front view showing a state in which a recess is cut into a workpiece by an end mill of the processing device. [Figure 4] FIG. 2 is a plan view showing a plurality of recesses formed in a workpiece. [Figure 5] FIG. 1 is a perspective view showing a microlens array manufactured using a mold. [Figure 6] FIG. 10 is a perspective view showing a state in which a microlens array manufactured using a mold is assembled. [Figure 7] 10A and 10B are diagrams showing examples of dimensions of roughing and finishing when forming recesses in a workpiece using an end mill of a processing device. [Figure 8] 10 is a graph showing the relationship between the number of recesses machined and the radius of curvature of the recesses, and is a graph showing a state in which the radius of curvature of the recesses in the Y direction (short side direction) is outside the standard value. [Figure 9] This is a graph showing the relationship between the number of recesses machined and the radius of curvature of the recesses, and shows a state in which the radius of curvature of the recesses in the Y direction (short side direction) is within the standard value by setting the position of the cutting edge of the end mill. [Figure 10] 10 is a graph showing the relationship between the number of recesses machined and the radius of curvature of the recesses, and shows a state in which the radius of curvature of the recesses in the X direction (longitudinal direction) and the Y direction (transverse direction) is within the standard value by fine-tuning the position of the cutting edge of the end mill. [Figure 11] FIG. 10 is a front view showing a state in which the cutting edge of the end mill of the processing device is worn. [Figure 12] 10A and 10B are diagrams illustrating changes in the cutting shape of a recess when the cutting edge of an end mill of a processing device is worn. [Figure 13](A) is a graph showing the relationship between the number of recesses machined and the radius of curvature of the recesses when the first and fourth surfaces on the movable side are formed using the manufacturing method of the mold of the first embodiment, and (B) is a graph showing the relationship between the number of recesses machined and the radius of curvature of the recesses when the second and third surfaces on the fixed side are formed using the manufacturing direction of the mold of the first embodiment. [Figure 14] (A) is a plan view showing the movement trajectory of the cutting edge of the end mill when cutting the recess for the first time, and (B) is a plan view showing the movement trajectory of the cutting edge of the end mill when cutting the recess for the second time. [Figure 15] (A) is a graph showing the relationship between the number of recesses machined and the radius of curvature of the recesses when the first and fourth surfaces on the movable side are formed using a comparative mold manufacturing method, and (B) is a graph showing the relationship between the number of recesses machined and the radius of curvature of the recesses when the second and third surfaces on the fixed side are formed using a comparative mold manufacturing method. [Figure 16] Graph (A) shows the relationship between the number of recesses machined and the geometric waviness when the first and fourth surfaces on the movable side are formed using a comparative mold manufacturing method, and graph (B) shows the relationship between the number of recesses machined and the geometric waviness when the second and third surfaces on the fixed side are formed using a comparative mold manufacturing method. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, embodiments for implementing the technology of the present disclosure will be described. In the following description, the direction indicated by arrow X (arrow X direction, X direction) shown as appropriate in the drawings will be the longitudinal direction (horizontal direction) of the workpiece, the direction indicated by arrow Y (arrow Y direction, Y direction) will be the lateral direction (horizontal direction) of the workpiece, and the direction indicated by arrow Z (arrow Z direction, Z direction) will be the height direction (vertical direction) of the workpiece. These arrow X direction, arrow Y direction, and arrow Z direction are directions that intersect with each other (specifically, directions that are perpendicular to each other). Note that when it is necessary to indicate one of the directions of the arrow X direction, it may be described as one side of the X direction or the other side of the X direction. The same applies to the arrow Y direction and the arrow Z direction.

[0022] [First embodiment] FIG. 1 is a perspective view of a processing apparatus 10 to which a mold manufacturing method according to a first embodiment is applied.

[0023] (Overall configuration of mold manufacturing equipment) As shown in FIG. 1, the processing apparatus 10 is an apparatus for manufacturing a mold by processing a workpiece 100. The workpiece 100 is an example of a mold material that constitutes a mold. In other words, the workpiece 100 is an object to be processed by the processing apparatus 10, and the processing apparatus 10 is an example of a mold manufacturing apparatus. The workpiece 100 is, for example, a long, narrow rectangular parallelepiped. The processing apparatus 10 is equipped with a holder 12 that holds the workpiece 100. The holder 12 fixes the longitudinal sides of the workpiece 100 with a fixture (not shown). A processing surface 100A is provided on the upper surface of the workpiece 100 held by the holder 12. The holder 12 holds the workpiece 100 so that the processing surface 100A is horizontal. The processing surface 100A is an example of a processing surface of a mold.

[0024] In the processing apparatus 10, when the workpiece 100 is held by the holder 12, the longitudinal direction of the workpiece 100 is the direction of arrow X, the lateral direction of the workpiece 100 (the direction perpendicular to the longitudinal direction) is the direction of arrow Y, and the height direction of the workpiece 100 (the direction perpendicular to both the X and Y directions) is the direction of arrow Z. In this embodiment, the depth direction of the processing apparatus 10 corresponds to the direction of arrow X, and the width direction of the processing apparatus 10 corresponds to the direction of arrow Y. Furthermore, the height direction of the processing apparatus 10 corresponds to the direction of arrow Z.

[0025] The processing device 10 includes a moving unit 14 to which the holding unit 12 is attached, and a Y-direction driving unit 16 that moves the moving unit 14 in the direction of the arrow Y. The processing device 10 is configured such that the Y-direction driving unit 16 moves the moving unit 14 in the direction of the arrow Y, thereby moving the workpiece 100 held by the holding unit 12 in the direction of the arrow Y.

[0026] The processing device 10 also includes an end mill 20 that processes the processing surface 100A of the workpiece 100, a support unit 22 that rotatably supports the end mill 20, and a motor mounting unit 24 on which a motor that rotates the end mill 20 is disposed. The end mill 20 is an example of a tool. The support unit 22 and the motor mounting unit 24 are examples of a rotating means. The processing device 10 also includes a moving unit 26 to which the support unit 22 and the motor mounting unit 24 are attached, and a Z-direction driving unit 28 that moves the moving unit 26 in the direction of arrow Z. The processing device 10 is configured such that the end mill 20 moves in the direction of arrow Z by moving the moving unit 26 in the direction of arrow Z using the Z-direction driving unit 28.

[0027] The processing device 10 also includes an X-direction drive unit 30 that moves the moving unit 26 and the Z-direction drive unit 28 in the direction of the arrow X. The processing device 10 is configured such that the X-direction drive unit 30 moves the moving unit 26 and the Z-direction drive unit 28 in the direction of the arrow X, thereby moving the end mill 20 in the direction of the arrow X.

[0028] Furthermore, the processing apparatus 10 includes a control unit 32 that controls each unit of the processing apparatus 10. For example, the control unit 32 controls the Y-direction drive unit 16, the Z-direction drive unit 28, and the X-direction drive unit 30. The control unit 32 also controls the motor of the motor mounting unit 24, thereby controlling the rotation of the end mill 20.

[0029] The moving unit 14 is a plate-shaped member arranged along the vertical direction. For example, the Y-direction driving unit 16 is equipped with a hydraulic cylinder, and the tip of the rod of the hydraulic cylinder is attached to the moving unit 14. The Y-direction driving unit 16 moves the rod of the hydraulic cylinder back and forth to move the moving unit 14 in the direction of the arrow Y.

[0030] For example, the Z-direction driving unit 28 is an actuator that moves the moving unit 26 in the direction of the arrow Z, and moves the moving unit 26 along a rail (not shown) arranged in the direction of the arrow Z. Furthermore, for example, the X-direction driving unit 30 is an actuator that moves the moving unit 26 and the Z-direction driving unit 28 in the direction of the arrow X, and moves the moving unit 26 and the Z-direction driving unit 28 along a rail (not shown) arranged in the direction of the arrow Z.

[0031] (End mill configuration) FIG. 2 shows a perspective view of the workpiece 100 and the tip of the end mill 20 (the cutting edge 20A side). FIG. 3 shows a front view of the workpiece 100 and the tip of the end mill 20 as viewed from the direction of arrow X. As shown in FIGS. 2 and 3, the tip of the end mill 20 is made of a plate-like member. When viewed from a direction perpendicular to the plate surface, the cutting edge 20A, which constitutes a part of the tip, has a triangular shape with an R-shaped cut. In FIGS. 2 and 3, most of the mounting portion of the end mill 20 (opposite the tip) is inserted into a hole (described in detail later) in the cylindrical body of the support portion 22, so only a portion of the longitudinal direction of the mounting portion (one end side) is shown. The mounting portion of the end mill 20 is, for example, an elongated rectangular parallelepiped with a square cross section. As shown in FIG. 3, the base end of the plate-like member, which is the tip side of the end mill 20, is integrally attached to one longitudinal end of the mounting portion of the end mill 20. The central axis passing through the center of a cross section in a direction intersecting the longitudinal direction of the mounting portion of the end mill 20 and extending in the longitudinal direction of the mounting portion will hereinafter be referred to as the "central axis of the end mill 20."

[0032] The end mill 20 rotates around a rotation axis 21 (described later) while being inclined with respect to the machining surface 100A of the workpiece 100. The rotation axis 21 is an example of an axis. The angle θ between the machining surface 100A of the workpiece 100 and the rotation axis 21 is an acute angle. That is, the end mill 20 rotates around the rotation axis 21 that is inclined at an acute angle with respect to the machining surface 100A of the workpiece 100. For example, the angle θ between the machining surface 100A of the workpiece 100 and the rotation axis 21 is set to 45°±6.35°. For example, a diamond cutting tool (i.e., a nano ball end mill) manufactured by A.L.M.T. Corporation is used as the end mill 20.

[0033] The rotation axis 21 of the end mill 20 is arranged along the Y direction when projected onto the machining surface 100A of the workpiece 100 (see FIGS. 2 and 3). In other words, the end mill 20 is attached to the support part 22 so that the rotation axis 21 of the end mill 20 is along the Y direction when projected onto the machining surface 100A of the workpiece 100. Here, the Y direction is an example of one direction. Furthermore, the X direction is an example of an intersecting direction that intersects with the one direction. Note that FIGS. 2 and 3 show a state in which the rotation axis 21 and the central axis of the end mill 20 are substantially aligned.

[0034] Although not shown, the support part 22 has a cylindrical body. In other words, the cylindrical body is connected to the rotation shaft 21 of the motor of the motor mounting part 24 and is rotatably supported by the support part 22 via bearings or the like. The end mill 20 is attached with its mounting part inserted into a hole in the cylindrical body of the support part 22, and the mounting part is pressed against the inner surface (inner wall surface) of the hole in the cylindrical body in a direction intersecting the central axis of the end mill 20 by a plurality of screws. Therefore, the end mill 20 rotates around the rotation shaft 21 due to the rotation of the motor of the motor mounting part 24.

[0035] The processing device 10 rotates the rotation axis 21 of the end mill 20 (rotates the end mill 20 around the rotation axis 21) and moves the cutting edge 20A of the end mill 20 in the X, Y, and Z directions relative to the processing surface 100A of the workpiece 100, thereby cutting a spherical crown-shaped recess 102 into the processing surface 100A. The recess 102 is a curved surface recessed from the surface of the processing surface 100A.

[0036] (Work configuration) FIG. 4 shows a plan view of the machined surface 100A of the workpiece 100 after machining. As shown in FIG. 4, the machined surface 100A of the workpiece 100 is cut using an end mill 20 (see FIG. 2, etc.) to form a plurality of spherical crown-shaped recesses 102 on the machined surface 100A of the workpiece 100. As an example, the plurality of spherical crown-shaped recesses 102 are arranged in two rows in a staggered pattern (alternate) along the X direction on the machined surface 100A of the workpiece 100. A mold 110 is manufactured by forming the plurality of recesses 102 on the machined surface 100A of the workpiece 100. The mold 110 is used to manufacture microlens arrays 200, 202 (see FIG. 5, etc.). The recesses 102 may be formed in a single row along the X direction, or in three or more rows in a staggered pattern along the X direction.

[0037] As shown in FIG. 3, a surface treatment layer 101 containing, as an example, a metal as a main component is formed on the surface of the workpiece 100. In this case, the processing surface 100A of the workpiece 100 becomes the surface of the surface treatment layer 101. The "metal" constituting the surface treatment layer 101 is, for example, a metal that has an oxide coating that prevents corrosion and rust. Examples of the "metal" include nickel, stainless steel, and titanium. In this embodiment, the surface treatment layer 101 is a nickel plating layer.

[0038] The surface treatment layer 101 has a thickness (thickness in the Z direction) greater than the depth (maximum depth in the Z direction) of the recesses 102. In this embodiment, the multiple recesses 102 are formed in the surface treatment layer 101. The thickness of the surface treatment layer 101 is, for example, 300 μm. The recesses 102 are formed so that the depth (maximum depth in the Z direction) of the deepest bottom surface from the surface of the surface treatment layer 101 is, for example, 90 μm.

[0039] (Configuration of microlens array) Fig. 5 shows microlens arrays 200 and 202 manufactured using the mold 110, and Fig. 6 shows the state of a lens array formed by assembling the microlens arrays 200 and 202. As shown in Fig. 5 and Fig. 6, the microlens arrays 200 and 202 are rectangular parallelepiped-shaped.

[0040] The microlens array 200 includes a first surface S1 on which two rows of staggered lenses 210 are formed, and a second surface S2 on which two rows of staggered lenses 210 are formed, on both sides in a direction perpendicular to the longitudinal direction. The microlens array 202 includes a third surface S3 on which two rows of staggered lenses 210 are formed, and a fourth surface S4 on which two rows of staggered lenses 210 are formed, on both sides in a direction perpendicular to the longitudinal direction. The first surface S1 and the fourth surface S4 are movable sides, and the second surface S2 and the third surface S3 are fixed sides. The lenses 210 are convex lenses with a protruding center. The lenses 210 are formed by a plurality of recesses 102 in the mold 110.

[0041] The microlens arrays 200 and 202 are assembled so that the second surface S2 of the microlens array 200 and the third surface S3 of the microlens array 202 face each other (see FIG. 6).

[0042] (Mold configuration) As an example, in a mold 110 for manufacturing microlens arrays 200, 202 corresponding to A3-sized paper, approximately 1,300 recesses 102 are formed in two staggered rows. The cutting edge 20A of the end mill 20 gradually wears out when cutting 1,300 recesses 102. For this reason, it is possible to replace the end mill 20 midway through cutting 1,300 recesses 102 (for example, after about 650 recesses). However, if the end mill 20 is replaced midway, the old end mill 20 will need to be removed from the cylindrical body of the support portion 22 and a new end mill 20 will need to be attached to the cylindrical body of the support portion 22. In other words, the end mill 20 needs to be detached from the processing device 10. In this case, there is a processing error between the old end mill 20 and the new end mill 20, and it is difficult to attach the old end mill 20 and the new end mill 20 in exactly the same condition to the cylindrical body of the support part 22, so it is difficult to match the misalignment between the center axis of the end mill 20 and the rotation axis 21, and as a result, there may be variations in the spacing between adjacent recesses 102 at the end mill replacement point (i.e., the pitch of the recesses 102 may no longer be uniform).

[0043] Therefore, in the mold manufacturing method of this embodiment, after all (e.g., 1,300) recesses 102 are roughly machined on the machining surface 100A of the workpiece 100 with the first end mill 20, the first end mill 20 is replaced with the second end mill 20. Furthermore, all (e.g., 1,300) recesses 102 are finish-machined with the second end mill 20. Figure 7 shows an example of the dimensions of the recesses 102 formed on the machining surface 100A of the workpiece 100 when rough-machined and the dimensions of the recesses 102 when finish-machined.

[0044] When the first end mill 20 is replaced with the second end mill 20, there is a concern that the end mill 20 may miss a cut due to misalignment between the center axis of the end mill 20 and the rotation axis 21. Here, a miss refers to the second end mill 20 being unable to cut the recess 102 that was roughly machined by the first end mill 20. Furthermore, the misalignment between the center axis of the end mill 20 and the rotation axis 21 refers to the misalignment (difference = misalignment 1 - misalignment 2) between the center axis of the first end mill 20 and the rotation axis 21 and the misalignment (difference = misalignment 1 - misalignment 2) between the center axis of the second end mill 20 and the rotation axis 21. As shown in FIG. 7 , if the cutting depth of the bottom of the recess 102 during finish machining of the recess 102 using the second end mill 20 is 3 μm, the second end mill 20 can finish machining the recess 102 without a miss if the misalignment between the center axis of the end mill 20 and the rotation axis 21 is within 15 μm.

[0045] 14(A) and (B) show plan views of the movement trajectory of cutting edge 20A of end mill 20 rotating around rotation axis 21 when forming one recess 102. As shown in Fig. 14(A), when forming one recess 102, cutting edge 20A of end mill 20 moves spirally relative to workpiece 100 in a direction from the outer periphery of recess 102 toward the center (for example, in the direction of arrow C1).

[0046] 14(A), the cutting edge 20A of the end mill 20 is moved spirally (in the direction of arrow C1) at a predetermined first depth from a first portion 122A on the outermost periphery toward the center, as shown in a movement trajectory 122, to cut the recess 102 for the first time. This forms a circular recess 102 at the predetermined first depth.

[0047] 14(B), the cutting edge 20A of the end mill 20 is moved spirally (in the direction of arrow C2) by a predetermined second depth from a second portion 124A slightly inward from the outermost first portion 122A toward the center, as shown in movement trajectory 124. This further cuts the circular recess 102 of the first depth formed by the first cutting of the recess 102 to a second depth. As a result, the peripheral portion becomes inclined, and if the first depth and the second depth are the same, a recess 102 having a depth twice the predetermined depth (the first depth or the second depth) is formed. Thereafter, although not shown, the cutting edge 20A of the end mill 20 may be moved spirally by a predetermined depth from a third portion slightly inward from the second portion 124A toward the center.

[0048] By performing spiral machining multiple times with the cutting edge 20A of the end mill 20, a spherical crown-shaped recess 102 is formed on the machined surface 100A of the workpiece 100.

[0049] (Setting of processing conditions for processing equipment) In the processing device 10 of this embodiment, only the "R (radius of curvature) of the cutting edge 20A of the end mill 20" and the "R (radius of curvature) of the target lens" can be set as processing conditions. The "R (radius of curvature) of the cutting edge 20A of the end mill 20" is a value determined by the end mill 20 used. In other words, the "R (radius of curvature) of the cutting edge 20A of the end mill 20" is set as the set value directly to the dimension of the R (radius of curvature) of the cutting edge 20A of the end mill 20 selected for cutting the processing surface 100A of the workpiece 100. Furthermore, the "R (radius of curvature) of the target lens" is the movement trajectory of the cutting edge 20A of the end mill 20 when the cutting edge 20A moves when cutting the processing surface 100A of the workpiece 100. In other words, the "R (radius of curvature) of the target lens" cannot be set in either the X direction alone or the Y direction alone. Therefore, when the set value of "R (radius of curvature) of the target lens" is changed, both the X direction (R in the X direction) of "R (radius of curvature) of the target lens" and the Y direction (R in the Y direction) of "R (radius of curvature) of the target lens" are changed. In other words, when the movement locus of the cutting edge 20A of the end mill 20, which is the "R (radius of curvature) of the target lens", is changed, both the Y direction and the X direction R (radius of curvature) of the recess 102 are changed. Here, R in the X direction refers to the radius of a cross section in the X direction that passes through the center of the recess 102 (the center of the bottom of the recess 102) when the recess 102 is formed by cutting the machining surface 100A of the workpiece 100 with the end mill 20, as shown in FIG. 12 . a - a Similarly, R in the Y direction is the radius of curvature of a cross section passing through the center of the recess 102 and along the Y direction when the recess 102 is formed by cutting the processing surface 100A of the workpiece 100 with an end mill 20, as shown in FIG. b - b This refers to the radius of curvature of the

[0050] (Comparative example of mold manufacturing method) Before describing the details of the method for manufacturing a mold according to this embodiment, a method for manufacturing a mold according to a comparative example will be described.

[0051] In the mold manufacturing method of the comparative example, only the "R (radius of curvature) of the cutting edge 20A of the end mill 20" and the "R (radius of curvature) of the target lens" are set, and multiple recesses 102 are formed on the processing surface 100A of the workpiece 100. In this way, a mold for molding the microlens arrays 200 and 202 is manufactured.

[0052] FIG. 15(A) shows measurement data of a mold used to form the first surface S1 and the fourth surface S4 of the microlens arrays 200 and 202, illustrating the relationship between the number of recesses 102 machined and R (radius of curvature). FIG. 15(B) shows measurement data of a mold used to form the second surface S2 and the third surface S3 of the microlens arrays 200 and 202, illustrating the relationship between the number of recesses 102 machined and R (radius of curvature). The number of recesses 102 machined is the number of recesses 102 machined by cutting. R (radius of curvature) is the actual measurement value of R (radius of curvature) in the X direction (longitudinal direction) and Y direction (transverse direction) of the recesses 102. USL1 in FIG. 15(A) is the upper limit of the specification, and LSL1 is the lower limit of the specification. USL2 in FIG. 15(B) is the upper limit of the specification, and LSL2 is the lower limit of the specification.

[0053] 15(A), in the mold for forming the first surface S1 and the fourth surface S4, the X-direction (longitudinal direction) of the R (radius of curvature) of the recess 102 is within the specified value, but the Y-direction (transverse direction) of the R (radius of curvature) of the recess 102 is outside the specified value. In other words, the Y-direction (transverse direction) of the R (radius of curvature) of the recess 102 exceeds the upper limit of the specified value USL1. The problem that the Y-direction (transverse direction) of the R of the recess 102 is outside the specified value is thought to occur, for example, due to wear of the cutting edge 20A of the end mill 20 and a poor initial position of the end mill 20 (i.e., the position where cutting of the workpiece 100 is started).

[0054] As shown in Figure 15(B), in the mold for molding the second surface S2 and the third surface S3, the X direction (longitudinal direction) of R (radius of curvature) of the recess 102 and the Y direction (transverse direction) of R (radius of curvature) of the recess 102 are both within the standard values.

[0055] Figure 16(A) shows measurement data of a mold used to form the first surface S1 and fourth surface S4 of microlens arrays 200 and 202, illustrating the relationship between the number of recesses 102 machined and the actual measured value of waviness of the recesses 102. Figure 16(B) shows measurement data of a mold used to form the second surface S2 and third surface S3 of microlens arrays 200 and 202, illustrating the relationship between the number of recesses 102 machined and the actual measured value of waviness of the recesses 102. The waviness in the X direction is the value measured in the X direction along the curved surface of the surface that constitutes the recesses 102. The waviness in the Y direction is the value measured in the Y direction along the curved surface of the surface that constitutes the recesses 102. USL3 in Figures 16(A) and 16(B) is the upper limit of the specification value.

[0056] As shown in FIGS. 16(A) and 16(B), the waviness of the recess 102 in the X direction and the waviness in the Y direction are both substantially equal to or less than the upper limit of the standard value USL3.

[0057] From the measurement data of the mold of the comparative example, it is desirable to manufacture the mold so that the R (radius of curvature) of the recess 102 shown in FIG. 15(A) in the Y direction (short direction) falls within the standard value.

[0058] (Specific example of the method for manufacturing the mold of this embodiment, and the operation of this embodiment) Next, a specific example of the method for manufacturing the mold of this embodiment and the operation of this embodiment will be described.

[0059] In the mold manufacturing method of this embodiment, the position of the cutting edge 20A of the end mill 20 is set so that the R (radius of curvature) of the recess 102 to be cut first is smaller in the Y direction when the rotation axis 21 of the end mill 20 is projected onto the machining surface 100A of the workpiece 100 than in the X direction, and cutting of the recess 102 begins (see data T1 and T2 shown in FIG. 10). Note that data T1 in FIG. 10 refers to the leftmost data (■) among the multiple data (■) shown in FIG. 10. Similarly, data T2 in FIG. 10 refers to the leftmost data (●) among the multiple data (●) shown in FIG. 10.

[0060] For example, the position of the cutting edge 20A of the end mill 20 is first set so that the R (radius of curvature) of the recess 102 in the Y direction is on the side of the lower limit LSL1 of the standard value (see data T1 shown in FIG. 9 ). The “side of the lower limit LSL1 of the standard value” is preferably within 20, more preferably within 10, and even more preferably within 5 of the lower limit LSL1 of the standard value, assuming that the range of the standard value is 100. In this embodiment, the position of the cutting edge 20A of the end mill 20 (i.e., the movement trajectory of the cutting edge 20A) is first set so that the R (radius of curvature) of the recess 102 in the Y direction is within the standard value and close to the lower limit LSL1 of the standard value (see data T1 shown in FIG. 9 ; hereinafter, this is referred to as “Y-direction setting”). Then, for example, the position of the cutting edge 20A of the end mill 20 is set so that the R (radius of curvature) of the recess 102 in the X direction is within the standard value (see data T2 shown in FIG. 10 ), independently of the setting in the Y direction (i.e., so as not to affect the setting in the Y direction). In this embodiment, the position of the cutting edge 20A of the end mill 20 is set so that the R (radius of curvature) of the recess 102 in the X direction is at the center of the standard value (the center between USL1 and LSL1) (see data T2 shown in Figure 10).

[0061] More specifically, in the machining device 10, after both the "R (radius of curvature) of the cutting edge 20A of the end mill 20" and the "R (radius of curvature) of the target lens" are set, a copper workpiece (a workpiece for test machining) is cut to form multiple (e.g., four) recesses 102. Then, among the multiple (e.g., four) recesses 102, the recesses 102 formed in the later cuts (e.g., the third and fourth) are measured, and the average of the measured R values ​​in the X direction and the Y direction of the recesses 102 is calculated. Since the two average values ​​often differ, the two average values ​​may be further averaged. This determines the difference between the set "R (radius of curvature) of the target lens" and the measured R (radius of curvature) of the recesses 102. The set value of the "R (radius of curvature) of the target lens" is again changed so that this difference becomes zero. When this change is made, the X direction of the "target lens R (radius of curvature)" is changed, and at the same time, the Y direction of the "target lens R (radius of curvature)" is also changed. The reason for cutting a copper workpiece (workpiece for trial machining) here is to reduce wear on the cutting edge 20A of the end mill 20. In addition, the reason for measuring the third and fourth recesses 102, which are later in the machining order, is to collect data that is close to that of actual mold manufacturing by measuring the recesses 102 machined by the end mill 20, which has become heated by cutting the workpiece.

[0062] Fig. 8 shows the first measured data, which is the relationship between the number of recesses 102 processed and R (radius of curvature). Fig. 8 is a diagram corresponding to Fig. 15(A) of the comparative example. Note that Fig. 8 lists all data in the X direction (longitudinal direction) and Y direction (transverse direction), but at this point, only the X direction (longitudinal direction) data on the leftmost side in Fig. 8 and the Y direction (transverse direction) data on the leftmost side are available. The other data are at a level that can be predicted from experience.

[0063] The above statement, "The set value of the 'target lens R (radius of curvature)' is changed again so that the difference between the set 'target lens R (radius of curvature)' and the measured R (radius of curvature) of the recess 102 becomes zero" refers to changing from the state shown in FIG. 8 to the state shown in FIG. 9. In other words, as shown in FIG. 9, the set value of the 'target lens R (radius of curvature)' is changed so that the Y-direction data T1 on the leftmost side is within the standard value (between USL1 and LSL1) and near the lower limit of the standard value LSL1. As described above, changing the 'target lens R (radius of curvature)' changes both the X-direction of the 'target lens R (radius of curvature)' and the Y-direction of the 'target lens R (radius of curvature)'. Therefore, the data in FIG. 9 appears as if it has been slid from top to bottom compared to FIG. 8.

[0064] Thereafter, in the mold manufacturing method of this embodiment, the position of the cutting edge 20A of the end mill 20 attached to the support part 22 of the processing device 10 is changed (i.e., finely adjusted). By finely adjusting the position of the cutting edge 20A of the end mill 20, the R (radius of curvature) of the recess 102 in the X direction is set to be within the standard value (see data T2 shown in FIG. 10).

[0065] That is, in this embodiment, the setting of the position of the cutting edge 20A of the end mill 20 so that the R (radius of curvature) of the recess 102 in the X direction falls within a standard value is the setting of the mounting position of the end mill 20 relative to the support part 22 that rotatably supports the end mill 20. More specifically, the mounting part of the end mill 20 is inserted into a hole in the cylindrical body of the support part 22, and is attached to the cylindrical body with multiple screws. Therefore, the mounting position of the end mill 20 is set (changed) by setting (changing) the position of the cutting edge 20A of the end mill 20 with the mounting part of the end mill 20 attached to the cylindrical body with multiple screws. In this embodiment, when setting the mounting position of the end mill 20 relative to the support part 22, the position of the cutting edge 20A of the end mill 20 is set so that the rotation diameter of the cutting edge 20A of the end mill 20 is large. In other words, the attachment position of the end mill 20 relative to the support portion 22 is set so that the runout between the central axis of the end mill 20 and the rotation axis 21 is increased so that the rotation diameter of the cutting edge 20A of the end mill 20 around the rotation axis 21 is increased. In other words, the attachment position of the end mill 20 relative to the support portion 22 is set so that the distance between the central axis of the end mill and the rotation axis 21 is increased at the cutting edge 20A.

[0066] Specifically, in the processing device 10, the end mill 20 is inserted into the hole in the cylindrical body (not shown) of the support part 22 as described above. The tip of the end mill 20 (near the cutting edge 20A) is then struck in a direction intersecting the direction of the rotation axis 21 to increase the radius of curvature (R) in the X direction (to increase the runout of the central axis of the end mill 20 relative to the rotation axis 21 at the cutting edge 20A). This fine-tunes the position of the cutting edge 20A. This shifts the position of the cutting edge 20A by several μm. Since the end mill 20 then rotates around the rotation axis 21, the cutting edge 20A becomes eccentric by several μm relative to the rotation axis 21. This changes the X direction of the "radius of curvature (R) of the target lens." Note that, at this time, the Y direction of the "radius of curvature (R) of the target lens" remains unchanged. That is, as shown in FIG. 10, R (radius of curvature) in the X direction is increased, and the first data T2 (the leftmost data T2) in the X direction (longitudinal direction) is positioned near the center of the standard value of R (the center between the upper limit USL1 of the standard value of R and the lower limit LSL1 of the standard value of R).

[0067] Before striking the tip of the end mill 20 (near the cutting edge 20A), the position of the cutting edge 20A of the end mill 20 may be adjusted to a position where the diameter of the recess 102 is largest when the end mill 20 is rotated, and if this is still not sufficient, the tip of the end mill 20 may be struck to increase the runout of the central axis of the end mill 20 relative to the rotation axis 21.

[0068] The above idea was obtained from the knowledge that the R (radius of curvature) of the recess 102 in the X direction does not affect the wear of the cutting edge 20A of the end mill 20, but the R (radius of curvature) of the recess 102 in the Y direction affects the wear of the cutting edge 20A of the end mill 20.

[0069] (Affected by wear on the cutting edge of the end mill) Here, the influence of wear on the cutting edge 20A of the end mill 20 will be described.

[0070] As shown in FIG. 11, as the number of recesses 102 machined increases, the cutting edge 20A of the end mill 20 wears from the initial state of edge 50 shown by the solid line to the state of edge 51 shown by the two-dot chain line.

[0071] When the cutting edge 20A of the end mill 20 is worn as described above, the R (radius of curvature) of the recess 102 changes from the initial state of the solid curved surfaces 152A and 152B to the state of the broken curved surfaces 154A and 154B after wear, as shown in Figure 12.

[0072] As described above, the rotation axis 21 of the end mill 20 is set to be along the Y direction when projected onto the machining surface 100A of the workpiece 100, and the end mill 20 rotates around the rotation axis 21. Therefore, when the cutting edge 20A of the end mill 20 is worn down like the edge 51 shown in Fig. 11, the Y-direction R (radius of curvature) of the recess 102 changes from the state of the curved surface 152B indicated by the solid line to the state of the curved surface 154B indicated by the dashed line, as shown in cross section bb in Fig. 12. In other words, the wear of the cutting edge 20A of the end mill 20 directly affects the shape of the recess 102.

[0073] On the other hand, when the cutting edge 20A of the end mill 20 is worn down as shown in edge portion 51 in Fig. 11, R (radius of curvature) in the X direction changes from the state of curved surface 152A indicated by the solid line to the state of curved surface 154A indicated by the dashed line, as shown in cross section aa in Fig. 12. In other words, although there is an effect of wear on the cutting edge 20A of the end mill 20, the cutting amount only decreases from the state of curved surface 152A after machining assuming no wear as shown by the solid line to the state of curved surface 154A indicated by the dashed line, and R (radius of curvature) remains almost unchanged. This is because the trajectory of the cutting edge 20A of the end mill 20 rotating around the rotation axis 21 becomes R (radius of curvature) in the X direction.

[0074] (Summary of the functions and effects of this embodiment) Next, the operation and effects of this embodiment will be described.

[0075] In the method for manufacturing a mold according to this embodiment, the cutting edge 20A of an end mill 20, which rotates around a rotation axis 21 inclined at an acute angle with respect to a machining surface 100A of a workpiece 100, is moved relative to the machining surface 100A to cut a plurality of spherical crown-shaped recesses 102 into the machining surface 100A. At this time, the position of the cutting edge 20A of the end mill 20 is set so that the R (radius of curvature) of the recesses 102 to be cut first is smaller in the Y direction when the cutting edge 20A of the end mill 20 is projected onto the machining surface 100A than in the X direction (see FIG. 10 ).

[0076] 13(A) shows measurement data of a mold used to form the first surface S1 and the fourth surface S4 of the microlens arrays 200 and 202, illustrating the relationship between the number of recesses 102 machined and R (radius of curvature). Also, FIG. 13(B) shows measurement data of a mold used to form the second surface S2 and the third surface S3 of the microlens arrays 200 and 202, illustrating the relationship between the number of recesses 102 machined and R (radius of curvature). As shown in FIGS. 13(A) and 13(B), the mold measurement data indicates that both the X-direction R (radius of curvature) of the recesses 102 and the Y-direction R (radius of curvature) of the recesses 102 are within the specified values. That is, it is confirmed that the Y-direction R (radius of curvature) of the recesses 102 is within the specified value even when the cutting edge 20A of the end mill 20 is worn.

[0077] Therefore, in the mold manufacturing method of this embodiment, it is possible to prevent the R (radius of curvature) of the recess 102 from falling outside the standard value, compared to when the R (radius of curvature) of the recess in the Y direction is larger than the R (radius of curvature) of the recess in the X direction in the recess that is cut first.

[0078] Furthermore, in the mold manufacturing method of this embodiment, the position of the cutting edge 20A of the end mill 20 is set so that the R (radius of curvature) of the recess 102 in the Y direction is on the lower limit LSL1 side of the standard value (see data T1 in Figure 9), and then the R (radius of curvature) of the recess 102 in the X direction is set so that it is within the standard value (between USL1 and LSL1) (see data T2 in Figure 10).

[0079] Therefore, in the mold manufacturing method of this embodiment, the position of the cutting edge 20A of the end mill 20 can be set more easily than when the cutting edge position is set only once so that the R (radius of curvature) of the recess in the X direction is within the standard value.

[0080] Furthermore, in the mold manufacturing method of this embodiment, the position of the cutting edge 20A of the end mill 20 that keeps the R (radius of curvature) of the recess 102 in the X direction within the standard value is set by setting the mounting position of the end mill 20 relative to the support part 22 that rotatably supports the end mill 20.

[0081] Therefore, in the method for manufacturing a mold according to this embodiment, the position of the cutting edge 20A of the end mill 20 can be set more easily than when the attachment portion of the end mill 20 is moved.

[0082] In the mold manufacturing method of this embodiment, the attachment position of the end mill 20 relative to the support part 22 is set so that the cutting edge 20A of the end mill 20 has a large rotation diameter.

[0083] Therefore, in the mold manufacturing method of this embodiment, the R (radius of curvature) in the Y direction of the recess 102 to be cut first is more likely to be smaller than the R (radius of curvature) in the X direction, compared to when the position of the end mill cutting edge is set so that the rotational diameter of the end mill cutting edge is smaller.

[0084] In the mold manufacturing method of this embodiment, the workpiece 100 is provided with a surface treatment layer 101 that is mainly composed of metal and has a thickness greater than the depth of the recesses 102. The recesses 102 are formed in the surface treatment layer 101 (see FIG. 3).

[0085] Therefore, in the method for manufacturing a mold according to this embodiment, corrosion of the workpiece 100 can be suppressed compared to when the mold material that constitutes the workpiece is exposed to the outside.

[0086] Furthermore, in the mold manufacturing method of this embodiment, when forming one recess 102, the cutting edge 20A of the end mill 20 is moved spirally relative to the workpiece 100 in a direction from the outer periphery of the recess 102 toward the center.

[0087] Therefore, in the mold manufacturing method of this embodiment, the waviness of the surface of the recess 102 can be reduced compared to when the cutting edge of the end mill is moved relative to the workpiece in the radial direction of the recess.

[0088] Furthermore, in the manufacturing method of the mold of this embodiment, after all the recesses 102 are roughly machined with the first end mill 20, the end mill 20 is replaced and all the recesses 102 are finish-machined with the second end mill 20.

[0089] Therefore, in the mold manufacturing method of this embodiment, the surface precision of the recess 102 is better than when a single end mill is used to finish machining the recess.

[0090] [Modification] As a modified example, when forming one recess 102, the cutting edge 20A of the end mill 20 may be moved spirally relative to the workpiece 100 in a direction from the center of the recess 102 toward the outer periphery (the directions of arrows C3 and C4 shown in FIGS. 14(A) and 14(B)). This makes it possible to reduce the waviness of the surface of the recess 102 compared to when the cutting edge of the end mill is moved relative to the workpiece in the radial direction of the recess.

[0091] 〔supplementary explanation〕 In the above embodiment, the position of the cutting edge 20A of the end mill 20 is set so that the R (radius of curvature) of the recess 102 to be cut first is smaller in the Y direction when the cutting edge 20A of the end mill 20 is projected onto the machining surface 100A than in the X direction, and cutting of the recess 102 is started, but the present disclosure is not limited to this configuration. For example, instead of the X direction perpendicular to the Y direction, a cross direction intersecting the Y direction may be used. Furthermore, instead of the Y direction, any one direction may be used, and a cross direction intersecting the one direction may be used.

[0092] In the above embodiment, the recess 102 was formed in the surface treatment layer 101 mainly composed of metal on the surface of the workpiece 100, but the present disclosure is not limited to this, and the recess 102 may also be formed in the metal material that constitutes the mold.

[0093] In the above embodiment, the cutting edge 20A of the end mill 20 is moved spirally relative to the machining surface 100A of the workpiece 100, but the trajectory along which the cutting edge 20A of the end mill 20 is moved relatively can be changed.

[0094] In the above embodiment, all recesses 102 are roughly machined with the first end mill 20, and then all recesses 102 are finished with the second end mill 20, but it is also possible to cut the recesses 102 with one end mill 20 without replacing the end mill 20.

[0095] In the above embodiment, the components constituting the processing device 10 can be changed. Also, the shape of the workpiece 100 can be changed.

[0096] Although the present invention has been described in detail with reference to specific embodiments, it will be apparent to those skilled in the art that the present invention is not limited to such embodiments, and that various other embodiments are possible within the scope of the present invention. [Explanation of symbols]

[0097] 20 End mill (example of tool) 20A cutting edge 21 Rotating shaft (example of shaft) 22 Support unit (an example of a rotating means) 24 Motor mounting portion (an example of a rotation means) 100 Workpiece (an example of metal material that makes up a mold) 100A machined surface 101 Surface treatment layer 102 recess 110 Mold LSL1 Lower limit of specification (an example of the lower limit of specification)

Claims

1. When cutting a plurality of spherical crown-shaped recesses having the same standard values ​​of the radii of curvature in two directions orthogonal to the machining surface of a mold by moving the cutting edge of a tool that rotates around an axis inclined at an acute angle to the machining surface relative to the machining surface, the position of the cutting edge is set so that the radius of curvature of the recess to be cut first in one direction, when the axis about which the tool rotates is projected onto the machining surface, is smaller than the radius of curvature in an intersecting direction intersecting with the one direction, and then the position of the cutting edge is set so that the radius of curvature in the one direction is on the lower limit side of the standard value, and the radius of curvature in the intersecting direction is set so that it is within the standard value, and then the cutting is started; The cutting process is terminated after the radius of curvature in the one direction becomes larger than the radius of curvature in the intersecting direction within the specified value. Mold manufacturing method.

2. 2. The method for manufacturing a mold according to claim 1, wherein the position of the cutting edge is set so that the radius of curvature of the recess in the intersecting direction falls within the standard value by setting the mounting position of the tool relative to a rotating means for rotating the tool.

3. 3. The method for manufacturing a mold according to claim 2, wherein the mounting position of the tool relative to the rotating means is set so that the cutting edge of the tool has a large rotation diameter.

4. a surface treatment layer containing metal as a main component is formed on a mold material constituting the mold, the surface treatment layer having a thickness greater than the depth of the recess; The mold manufacturing method according to claim 1 , wherein the plurality of recesses are formed in the surface treatment layer.

5. A method for manufacturing a mold described in any one of claims 1 to 4, wherein, when forming one recess, the cutting edge of the tool is moved relative to the mold material constituting the mold in a spiral pattern in a direction from the outer periphery of the recess toward the center, or in a direction from the center of the recess toward the outer periphery.

6. After rough machining all of the recesses with a first tool, the tool is replaced; The method for manufacturing a mold according to any one of claims 1 to 5, wherein a second tool is used to finish all of the recesses.

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