Processing method

Abstract

In the machining method using the spherical core type machining machine (1), a tool mounting step (ST1) of holding the lens material (40) in the lens holder (41) and mounting the machining tool (5) on the spindle (6), a first spherical surface machining step (ST2) of performing a spherical surface machining operation, a first difference obtaining step (ST3) of obtaining the first machining radius (R1) of the machining target surface (40a) of the lens material (40) and obtaining the first difference (ΔR1) between the target radius (Re) and the first machining radius (R1), a first tool position setting step (ST4) of moving the machining tool (5) by a distance corresponding to the first difference (ΔR1) so that the distance between the first contact point (C1) in contact with the machining target surface (40a) on the tool surface (5a) of the machining tool (5) and the intersection point (O) of the rotation axis (L1) and the swing axis (L2) is the target radius (Re), and a second spherical surface machining step (ST5) of holding a new lens material (40) in the lens holder (41) and performing a spherical surface machining operation.

Description

Technical Field

[0001] The present invention relates to a method for processing a lens material using a ball-core type processing machine and a ball-core type processing machine.

Background Art

[0002] A ball-core type processing machine for spherically processing a lens material held by a lens holder with a processing tool mounted on a spindle is described in Patent Document 1. The ball-core type processing machine in this document presses the processing target surface of the lens material against the tool surface of the processing tool by biasing the lens holder toward the spindle side. Further, the ball-core type processing machine in this document rotates the spindle to rotate the processing tool around the rotation axis of the spindle, and swings the processing tool around a swing axis orthogonal to the rotation axis of the spindle. Thereby, the ball-core type processing machine transfers the spherical shape of the tool surface of the processing tool to the processing target surface of the lens material.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the spherical surface machining by a conventional spherical core type machining machine, the shape of the tool surface of the machining tool is transferred to the machining target surface of the lens material. Therefore, it is necessary for the machining tool to have a spherical surface having the same radius as the target lens surface on the tool surface. For this reason, the shape of the tool surface of the machining tool is required to be formed with an accuracy of plus / minus 1 μm (micrometer) or less. However, it is not easy to form the shape of the tool surface of the machining tool with the required accuracy, and the manufacture of such a high-precision machining tool depends on the skill of the craftsman. Further, as the radius of the target lens surface becomes smaller, it becomes more difficult to measure the tool surface of the machining tool, so it becomes more difficult to accurately form the tool surface of the machining tool. As a result, forming the tool surface of the machining tool requires a lot of time, hinders the stability of machining accuracy, and causes a decrease in productivity.

[0005] In view of the above problems, an object of the present invention is to propose a machining method that allows the accuracy of forming the tool surface of a machining tool at the initial stage to be more acceptable than in the past when performing spherical surface machining of a lens material using a spherical core type machining machine. 。

Means for Solving the Problems

[0006] In order to solve the above problems, the present invention uses a spherical core type machining device, presses the machining target surface of the lens material held by the lens holder against the tool surface of the machining tool mounted on the spindle, and swings the machining tool around a swing axis orthogonal to the rotation axis of the spindle while rotating the spindle. In the machining method for performing the spherical surface machining operation, a tool mounting step of holding the lens material in the lens holder and mounting the machining tool on the spindle, a first spherical surface machining step of performing the spherical surface machining operation for a set time, After completion of the first spherical surface machining step, a first difference obtaining step of measuring the machining target surface to obtain a first machining radius of the machining target surface, and obtaining a first difference between the target radius of the target lens surface to be formed on the machining target surface and the first machining radius; while fixing the swing axis, by moving the spindle in a direction along the rotation axis moving the machining tool in a direction along the rotation axis by a distance corresponding to the first difference andA first tool position setting step of setting, as the target radius, the distance between a first contact point that contacts the surface to be machined on the tool surface of the machining tool and the intersection point of the rotation axis and the swing axis; holding the new lens material in the lens holder, and then a second spherical surface machining step of performing the spherical surface machining operation for the set time, and having the set time is the machining time required to form a target lens surface on the machining target surface of the lens material is characterized in that

[0007] In the first spherical surface machining step performed using the spherical center type machining apparatus according to the present invention, by the spherical surface machining operation, on the surface to be machined of the lens material, a spherical surface corresponding to the locus along which a first contact point that contacts the lens material on the tool surface of the machining tool rotates and swings is formed. Therefore, the first machining radius obtained by measuring the surface to be machined in the first difference acquisition step corresponds to the distance from the intersection point of the rotation axis and the swing axis to the first contact point that contacts the lens material on the tool surface of the machining tool. Here, if the spherical surface machining operation is performed by setting the distance to the first contact point that contacts the lens material on the tool surface of the machining tool to the target radius of the target lens surface, the spherical surface corresponding to the locus along which the first contact point rotates and swings becomes a spherical surface having the target radius. Therefore, in the present invention, in the first difference acquisition step, the surface to be machined is measured to obtain a first difference between the first machining radius of the surface to be machined and the target radius. Further, in the next first tool position setting step, by moving the machining tool in the direction along the rotation axis by a distance corresponding to the first difference, the distance between the first contact point that contacts the surface to be machined of the lens material on the tool surface of the machining tool and the intersection point of the rotation axis and the swing axis is set as the target radius. Therefore, after the first tool position setting step, if the spherical surface machining operation (second spherical surface machining step) is performed, a target lens surface can be formed on the surface to be machined of the lens material. Further, in the present invention, if the surface to be machined is measured in the first difference acquisition step to obtain a first difference between the first machining radius of the surface to be machined and the target radius, the machining tool can be arranged at an appropriate position based on the first difference. Therefore, it is easy to arrange the machining tool at a position where the target lens surface can be formed on the lens material.

[0008] Thus, the processing method of the present invention does not assume that the shape of the tool surface of the processing tool coincides with the spherical surface having the target radius, and that the tool surface and the lens material are in surface contact during the spherical surface processing operation. That is, in the processing method of the present invention, an error between the shape of the tool surface of the processing tool and the spherical surface having the target radius is allowed, and it is assumed that the tool surface and the processing target surface of the lens material are partially in contact. Further, even if there is an error between the shape of the tool surface of the processing tool and the spherical surface having the target radius, after adjusting the position of the processing tool based on the first difference between the first processing radius of the processing target surface after the first spherical surface processing operation and the target radius, the spherical surface processing operation is performed, thereby forming a spherical surface having the target radius on the processing target surface. Therefore, the accuracy of the spherical shape of the tool surface of the processing tool can be allowed to be lower than before.

[0009] Next, the present invention repeats the second spherical surface processing step a preset first number of times, then measures the processing target surface of the last lens material to obtain a second processing radius of the processing target surface, and obtains a second difference between the target radius of the target lens surface to be formed on the processing target surface and the second processing radius in a second difference obtaining step. while fixing the swing axis, by moving the spindle in a direction along the rotation axis move the processing tool in a direction along the rotation axis by a distance corresponding to the second difference and a second tool position setting step of setting the distance between a second contact point on the tool surface of the processing tool in contact with the processing target surface and the intersection of the rotation axis and the swing axis as the target radius, and a third spherical surface processing step of holding a new lens material in the lens holder and performing the spherical surface processing operation for the set time. The third spherical surface processing step is repeated a preset second number of times.

[0010] According to the present invention, the second spherical surface machining process is repeated a preset first number of times. Therefore, lenses having the target lens surface can be continuously manufactured as many times as the second spherical surface machining process is repeated. Here, when the spherical surface machining operation is repeated, wear occurs on the tool surface of the machining tool. According to the findings obtained by the inventors through intensive studies, when the spherical surface machining operation of rotating and swinging the machining tool is repeated with the distance between the first contact point on the tool surface of the machining tool that contacts the machining target surface of the lens material and the intersection point of the rotation axis and the swing axis as the target radius, the tool surface will, due to wear, have a shape that highly accurately matches the spherical surface having the target radius. That is, when the spherical surface machining operation is repeated with the distance between the first contact point and the intersection point as the target radius, the machining tool is dressed to have a spherical surface with the target radius on its tool surface. In other words, by repeating the second spherical surface machining process after the first tool position setting process with the distance between the tool surface of the machining tool and the swing axis as the target radius, the ball-core type machining machine not only has the spherical surface machining function of machining the lens material into a spherical surface, but also has a tool forming function of wearing the tool surface of the machining tool to form a spherical surface having the same radius as the target lens surface on the tool surface of the machining tool. Therefore, according to the present invention, when the second spherical surface machining process is repeated, the target lens surface can be formed on the machining target surface of the lens material with high precision and stably.

[0011] Here, if the second spherical surface machining process is repeated further, the shape of the tool surface changes due to wear to include an error with respect to the spherical surface having the target radius. Therefore, at the end of the second spherical surface machining process, during the spherical surface machining operation, the spherical surface having a radius different from the target radius formed on the tool surface and the lens material no longer come into surface contact, and the tool surface comes into partial contact with the machining target surface of the lens material. Therefore, in the second difference acquisition process performed after the second spherical surface machining process, the machining target surface is measured to obtain a second difference between the second machining radius of the machining target surface and the target radius. Further, in the next second tool position setting process, the machining tool is moved in the direction along the rotation axis by a distance corresponding to the second difference. As a result, the distance between the second contact point on the tool surface of the machining tool that contacts the machining target surface of the lens material and the intersection point of the rotation axis and the swing axis is set as the target radius. Therefore, in the subsequent spherical surface machining operation (third spherical surface machining process), the target lens surface can be formed on the machining target surface of the lens material. Also, in the second difference acquisition process, if the machining target surface is measured to obtain the second difference between the second machining radius of the machining target surface and the target radius, the machining tool can be arranged at an appropriate position based on the second difference. Therefore, it is easy to arrange the machining tool at a position where the target lens surface can be formed on the lens material.

[0012] Here, in the conventional technique, when the spherical surface machining operation is repeatedly performed and the shape of the tool surface changes due to wear to include an error with respect to the spherical surface having the target radius, the manufacturing of the lens could not be restarted unless the machining tool was removed from the spindle and a craftsman molded the tool surface of the machining tool into a spherical surface having the target radius and then attached it to the spindle. In contrast, according to the present invention, by setting the distance between the second contact point on the tool surface of the machining tool that contacts the machining target surface of the lens material and the intersection point of the rotation axis and the swing axis as the target radius of the target lens surface, the manufacturing of the lens can be restarted. Therefore, the productivity of the lens is improved.

[0013] Also, if the third spherical surface machining process is repeated a preset number of times, the lens having the target lens surface can be continuously manufactured as many times as the third spherical surface machining process is repeated. Here, when the spherical surface machining operation is repeated, wear occurs on the tool surface of the machining tool. According to the findings obtained by the inventors, when the spherical surface machining operation is repeated with the distance between the second contact point on the tool surface of the machining tool that contacts the machining target surface of the lens material and the intersection point of the rotation axis and the swing axis as the target radius, the tool surface will, due to wear, have a shape that highly accurately matches the spherical surface having the target radius. That is, when the spherical surface machining operation is repeated with the distance between the second contact point and the intersection point as the target radius, the machining tool is dressed to have a spherical surface with the target radius on the tool surface. In other words, by repeating the second spherical surface machining process after the first tool position setting process with the distance between the tool surface of the machining tool and the swing axis as the target radius, the spherical machining machine not only has the spherical surface machining function of machining the lens material into a spherical surface, but also has a tool shaping function of wearing the tool surface of the machining tool to form a spherical surface having the same radius as the target lens surface on the tool surface of the machining tool. Therefore, according to the present invention, when the third spherical surface machining process is repeated, the target lens surface can be formed on the machining target surface of the lens material with high precision and stably.

[0014] In the present invention, in the spherical surface machining operation, it is desirable that the spindle rotation speed for rotating the spindle be 2000 rpm or less. By setting the spindle rotation speed lower than before, adjustment of the dynamic balance of the machining tool can be dispensed with. Therefore, the manufacture of the machining tool becomes easier. Here, the machining tool has the characteristic that it is more likely to wear when performing the spherical surface machining operation at a low rotation speed than when performing the spherical surface machining operation at a high rotation speed. Therefore, if the spindle rotation speed is set lower than before, the wear rate of the tool surface of the machining tool can be increased when repeating the second spherical surface machining step or the third spherical surface machining step. Thus, in the repeated second spherical surface machining step or third spherical surface machining step, a spherical surface having the same radius as the target lens surface can be formed on the surface of the machining tool in a short time. From this, by setting the spindle rotation speed to 2000 rpm or less, conditions can be arranged such that the tool surface of the machining tool is likely to wear and the tool surface is likely to be dressed. From the viewpoint of the machining efficiency of the machining target surface, it is desirable that the rotation speed be 1500 rpm or more.

[0015] In the present invention, in the spherical surface machining operation, the lens holder is rotated around a central axis passing through the holder center of the lens holder and the material center of the lens material held by the lens holder, and the rotation direction of the lens holder is the same as the rotation direction of the spindle, and the holder rotation speed for rotating the lens holder can be set to be 25% or more and 35% or less of the spindle rotation speed for rotating the spindle. By rotating the lens holder to rotate the lens material integrally with the lens holder, it is possible to prevent or suppress the occurrence of uneven cutting on the machining target surface during the spherical surface machining operation. Here, if the holder rotation speed is more than 35% of the spindle rotation speed, the difference in the rotation speeds of the machining tool and the lens material decreases, and the machining efficiency decreases. If the holder rotation speed is less than 25% of the spindle rotation speed, in the machining target surface of the lens material, the machining of the portion where the tool surface of the machining tool is in point contact may progress compared to other portions, and the spherical surface accuracy may deteriorate.

[0016] In this case, when the lens material rotates with the processing tool and the rotational speed of the lens holder exceeds the set rotational speed of the holder, the lens holder may be allowed to rotate beyond the rotational speed of the holder. By doing so, it is possible to prevent or suppress damage to the lens material during the spherical surface processing operation and roughness of the surface accuracy of the processing target surface.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0020] Hereinafter, with reference to the drawings, a spherical core type processing machine and a method for processing a lens material using the spherical core type processing machine will be described.

[0021] FIG. 1 is a front view of the lower shaft mechanism of the spherical core processing machine. FIG. 2 is a side view of the lower shaft mechanism of the spherical core processing machine. FIG. 3 is a front view of the upper shaft mechanism of the spherical core processing machine. As shown in FIGS. 1 and 2, the spherical core processing machine 1 includes a lower shaft mechanism 2 and an upper shaft mechanism 3. As shown in FIG. 1, the lower shaft mechanism 2 includes a spindle unit 7 having a spindle 6 to which a processing tool 5 is attached, a moving mechanism 8 that moves the spindle unit 7 in the rotational axis direction along the rotational axis L1 of the spindle 6, and a swinging mechanism 9 that swings the spindle unit 7 around a swinging axis L2 orthogonal to the rotational axis L1.

[0022] The spindle unit 7 includes a spindle motor 11, a first rotation transmission mechanism 12 that transmits the rotation of the spindle motor 11 to the spindle 6, and a frame 13 that supports the spindle motor 11 and the rotation transmission mechanism. The processing tool 5 is detachably attached to the spindle 6 via an adapter 14. Also, as shown in FIG. 2, the spindle unit 7 includes an inverter 15 that controls the rotational speed of the spindle motor 11. The processing tool 5 attached to the spindle 6 rotates around the rotational axis L1 by the drive of the spindle motor 11.

[0023] As shown in FIG. 1, the moving mechanism 8 includes a pair of plates 18 disposed on both sides of the spindle 6. Each of the pair of plates 18 is provided with a linear guide 19. The two linear guides 19 extend in parallel. The frame 13 of the spindle unit 7 is spanned across the two linear guides 19. The frame 13 is movable along the linear guide 19. Also, as shown in FIG. 2, the moving mechanism 8 includes a feed screw mechanism 21 and a tool position control servo motor 22. The feed screw mechanism 21 includes a nut 23 fixed to the frame 13 of the spindle unit 7 and a feed screw 24 supported by the plate 18. The tool position control servo motor 22 is supported by the plate 18 together with the feed screw 24. The rotation of the tool position control servo motor 22 is transmitted to the feed screw 24 via a second rotation transmission mechanism 25. The second rotation transmission mechanism 25 includes a timing belt 26.

[0024] A movement feed control command is input from the tool position controller 27 to the tool position control servo motor 22. The tool position control servo motor 22 rotates according to the movement feed control command of the tool position controller 27, and moves the spindle unit 7 in the direction along the linear guide 19. In this example, a servo motor is used to drive the feed screw 24, and by using a feed screw 24 with a high-precision pitch, the spindle unit 7 is moved with a resolution of 1 μm or less.

[0025] As shown in FIG. 1, the swing mechanism 9 includes two shafts 31 fixed to each of the pair of plates 18. Further, as shown in FIG. 2, the swing mechanism 9 includes a swing control servo motor 32. One of the shafts 31 is fixed to a base (not shown) via a pillow block 33. A shaft-side pulley 34 is attached to the other shaft 31. A motor-side pulley 35 is attached to the swing control servo motor 32. A timing belt 36 is stretched between the shaft-side pulley 34 and the motor-side pulley 35. The rotation of the swing control servo motor 32 is transmitted to the other shaft 31 via the timing belt 36.

[0026] A swing control command is input from the swing controller 37 to the swing control servo motor 32. The swing control servo motor 32 swings the shaft 31 at a predetermined swing angle and speed based on the swing control command input from the swing controller 37. As a result, the pair of frames 13 swing around the axes of the two shafts 31, so that the spindle unit 7 and the movement mechanism 8 swing around the axes of the two shafts 31. The axes of the two shafts 31 are the swing axis L2 around which the spindle unit 7 and the movement mechanism 8 swing. The swing axis L2 is orthogonal to the rotation axis L1 of the spindle 6. In this example, the intersection O of the swing axis L2 and the rotation axis L1 is located at the center of the spherical surface formed on the tool surface of the machining tool 5 attached to the spindle 6.

[0027] As shown in Fig. 3, the upper shaft mechanism 3 includes a lens holder 41 that holds the lens material 40. The lens holder 41 holds the lens material 40 by means of vacuum adsorption. Further, the upper shaft mechanism 3 includes a rotation mechanism 43 that rotates the lens holder 41, and a biasing mechanism 63 that exerts a biasing force for biasing the lens holder 41 toward the spindle 6 of the lower shaft mechanism 2. Furthermore, the upper shaft mechanism 3 includes a lifting mechanism 45 for lifting and lowering the lens holder 41.

[0028] The rotation mechanism 43 includes a lens rotation shaft 46 that extends upward from the lens holder 41. The lens rotation shaft 46 is coaxial with the lens holder 41. The lens rotation shaft 46 is rotatably held on the inner peripheral side of the hollow shaft 49 via bearings 47 and 48. The hollow shaft 49 is vertically movably held on the sleeve 25 via a metal bearing 51. Here, a rotary joint 52 is attached to the upper end portion of the lens rotation shaft 46, and vacuum from a vacuum source (not shown) is transmitted to the lens holder 41 through the lens rotation shaft 46. Therefore, the lens holder 41 can vacuum-adsorb the lens material 40.

[0029] Also, the rotation mechanism 43 includes a lens rotation motor 55 and a third rotation transmission mechanism 56 that transmits the rotation of the lens rotation motor 55 to the lens rotation shaft 46. The third rotation transmission mechanism 56 includes a gear 58 attached to the lens rotation shaft 46 via a one-way clutch 57, a motor gear 59 attached to the output shaft of the lens rotation motor 55, and an idler gear 60 that meshes with the gear 58 and the motor gear. The rotation speed of the lens rotation motor 55 is controlled by an inverter 61. Here, the lens holder 41 rotates around a predetermined central axis L3 as the lens rotation shaft 46 rotates. The central axis L3 coincides with the axis of the lens rotation shaft 46. Also, the central axis L3 passes through the holder center of the lens holder 41 and the material center of the lens material 40 held by the lens holder 41.

[0030] The biasing mechanism 63 includes a shaft head 64 provided at the upper end portion of the hollow shaft 49, a press base 65 attached above the shaft head 64, and a biasing spring 67 disposed between the ceiling portion 66 of the sleeve 25 and the press base 65. When the biasing spring 67 is compressed, the biasing mechanism 63 exerts a biasing force that biases the lens holder 41 downward via the press base 65 and the shaft 31. Further, the biasing mechanism 63 includes a bolt 68 that penetrates the ceiling portion 66 of the sleeve 25 and abuts against the upper end of the biasing spring 67. By advancing and retracting the bolt 68 with respect to the ceiling portion 66, the amount of compression of the biasing spring 67 can be adjusted.

[0031] Here, the central axis L3 about which the lens holder 41 rotates is orthogonal to the swing axis L2 about which the spindle unit 7 and the moving mechanism 8 swing in the lower shaft mechanism 2. Further, the central axis L3 about which the lens holder 41 rotates passes through the intersection point O (see FIG. 1) of the rotation axis L1 of the spindle 6 and the swing axis L2. The elevating mechanism 45 moves the rotation mechanism 43 and the biasing mechanism 63 in the direction of the central axis L3 along the central axis L3. Thereby, the elevating mechanism 45 moves the lens holder 41 in the direction of the central axis L3.

[0032] (Processing method) Next, a processing method for processing the lens material 40 using the above-described spherical core processing apparatus will be described. FIG. 4 is a flowchart of the processing operation. As shown in FIG. 4, in the processing operation, first, a tool mounting step ST1, a first spherical surface processing step ST2, a first difference acquisition step ST3, and a first tool position setting step ST4 are performed in this order. Next, the second spherical surface processing step ST5 is repeated a preset first set number of times (ST6). Thereafter, a second difference acquisition step ST7 and a second tool position setting step ST8 are performed in this order, and then the third spherical surface processing step ST9 is repeated a preset second set number of times (ST10).

[0033] In the tool mounting process ST1, the lens material 40 is held by the lens holder 41, and the processing tool 5 is mounted on the spindle 6. As shown in FIG. 3, the lens material 40 is vacuum-sucked (held) by the lens holder 41 with the processing target surface 40a facing the spindle 6 side.

[0034] In the first spherical surface processing process ST2, the spherical surface processing operation is performed for a set time. In the spherical surface processing operation, the lens holder 41 holding the lens material 40 is moved toward the spindle 6 side by the lifting mechanism 45 of the upper shaft mechanism 3. As a result, the ball core type processing machine 1 is in a state where the processing target surface 40a of the lens material 40 held by the lens holder 41 is pressed against the tool surface 5a of the processing tool 5 mounted on the spindle 6. Also, in the spherical surface processing operation, the spindle motor 11 and the swing control servo motor 32 are driven. As a result, the ball core type processing machine 1 swings the processing tool 5 around the swing axis L2 orthogonal to the rotation axis L1 of the spindle 6 while rotating the spindle 6. In this example, the spindle rotation speed for rotating the spindle 6 is controlled to 2000 rpm.

[0035] Also, in the spherical surface processing operation, the lens rotation motor 55 is driven to rotate the lens holder 41 around the central axis L3. The rotation direction of the lens holder 41 and the rotation direction of the spindle 6 are the same. In this example, the holder rotation speed for rotating the lens holder 41 is set to 30% of the spindle rotation speed for rotating the spindle 6. It is desirable that the holder rotation speed be 25% or more and 35% or less of the spindle rotation speed. Here, when the lens material 40 is carried around by the processing tool 5 and the holder rotation speed of the lens holder 41 exceeds the set holder rotation speed, the one-way clutch 57 functions and the lens holder 41 is allowed to rotate beyond the holder rotation speed. Note that the set time for performing the spherical surface processing operation is the processing time required to form the target lens surface G on the processing target surface 40a of the lens material 40. The set time is set in advance based on the hardness of the lens material 40, the shape of the target lens surface G, the hardness of the tool surface 5a of the processing tool 5, and the like.

[0036] FIG. 5 shows the state at the start of the spherical surface machining operation in the first spherical surface machining step ST2. FIG. 5 is an explanatory view of the contact state between the machining tool 5 and the lens blank 40. In FIG. 5, the machining target surface 40a of the lens blank 40 held by the lens holder 41 is pressed against the tool surface 5a of the machining tool 5 attached to the spindle 6 with a biasing force F.

[0037] In the example shown in FIG. 5, the radius Rr of the machining target surface 40a of the lens blank 40, the radius Rt of the tool surface 5a of the machining tool 5, and the target radius Re of the target lens surface G are all different. Also, the dimensional relationship of "the radius Rr of the machining target surface 40a of the lens blank 40 < the radius Rt of the tool surface 5a < the target radius Re of the target lens surface G" holds. In such a dimensional relationship, the tool surface 5a contacts the machining target surface 40a of the lens blank 40 partially. Here, the point of contact between the tool surface 5a of the machining tool 5 and the machining target surface 40a is defined as the contact point C.

[0038] FIG. 6 is an explanatory view of the shape of the machining target surface 40a of the lens blank 40 after the first spherical surface machining step ST2. In the first difference acquisition step ST3, first, the shape of the machining target surface 40a of the lens blank 40 after the spherical surface machining operation is measured, and the first machining radius R1 of the spherical surface formed on the machining target surface 40a is obtained. The measurement of the shape of the machining target surface 40a and the acquisition of the first machining radius R1 are performed by removing the lens blank 40 from the lens holder 41 and measuring it with a surface shape measuring machine for lenses (not shown). Also, the first difference ΔR1 between the first machining radius R1 and the target radius Re of the target lens surface G is obtained.

[0039] The first machining radius R1 obtained in the first difference acquisition step ST3 corresponds to the distance LC (see FIG. 5) between the contact point C that contacts the machining target surface 40a on the tool surface 5a of the machining tool 5 and the intersection point O of the rotation axis L1 and the swing axis L2. That is, in the spherical surface machining operation, since the machining tool 5 swings while rotating, the spherical surface formed on the machining target surface 40a is a locus where the contact point C swings around the intersection point O while rotating around the rotation axis L1. Here, since the target radius Re of the target lens surface G is a known value, this value is stored and held in the surface shape measuring machine, and when the measurement of the shape of the machining target surface 40a is completed, the first difference ΔR1 can be automatically output from the surface shape measuring machine.

[0040] In the first tool position setting step ST4, the first difference ΔR1 is input to the tool position controller 27. For example, the first difference ΔR1 is input to the tool position controller 27 from the surface shape measuring machine by communication. Note that the operator may manually input the first difference ΔR1 obtained in the first difference acquisition step ST3 to the tool position controller 27.

[0041] The tool position control servo motor 22 rotates according to the movement control instruction from the tool position controller 27, and moves the spindle unit 7 in the direction along the rotation axis L1 of the spindle 6 (the direction along the linear guide 19) by a distance corresponding to the first difference ΔR1. The moving direction of the spindle unit 7 is a direction that cancels out the first difference ΔR1 between the first machining radius R1 and the target radius Re of the target lens surface G. In this example, the tool position controller 27 can move the spindle unit 7 with a resolution of 1 μm or less. FIG. 7 is an explanatory diagram of a state in which the machining tool 5 is moved by a distance corresponding to the first difference ΔR1 in the first tool position setting step ST4. In FIG. 7, the machining tool 5 is in a state of being moved by a distance corresponding to the first difference ΔR1, and the machining target surface 40a of the lens blank 40 held by the lens holder 41 is pressed against the tool surface 5a of the machining tool 5 mounted on the spindle 6 with a biasing force F.

[0042] In the example shown in FIG. 6, the first machining radius R1 of the machining target surface 40a of the lens material 40 is smaller than the target radius Re of the target lens surface G. Therefore, in the first tool position setting step ST4, the machining tool 5 (spindle unit 7) is moved in a direction approaching the lens material 40 (lens holder 41) by the first difference ΔR1. As a result, the machining tool 5 is disposed at a position where the distance from the first contact point C1 to the intersection point O coincides with the target radius Re of the target lens surface G. Here, since the machining tool 5 rotates around the rotation axis L1 and swings around the swing axis L2 during the spherical machining operation, the distance from the first contact point C1 to the intersection point O can be described as the distance from the tip of the tool surface 5a of the machining tool 5 to the intersection point O.

[0043] When the first machining radius R1 of the machining target surface 40a of the lens material 40 is larger than the target radius Re of the target lens surface G, the machining tool 5 (spindle unit 7) is moved in a direction away from the lens material 40 (lens holder 41) by the first difference ΔR1. As a result, the machining tool 5 is disposed at a position where the distance from the first contact point C1 to the intersection point O coincides with the target radius Re of the target lens surface G. Further, if the first machining radius R1 of the machining target surface 40a of the lens material 40 coincides with the target radius Re of the target lens surface G, in the first tool position setting step ST4, the machining tool 5 (spindle unit 7) is not moved. That is, in this case, the target lens surface G is formed on the machining target surface 40a of the lens material 40, and the distance from the first contact point C1 to the intersection point O coincides with the target radius Re of the target lens surface G.

[0044] In the second spherical surface machining process ST5, the spherical surface machining operation is performed in a state where the distance between the first contact point C1 in contact with the machining target surface 40a of the lens material 40 on the tool surface 5a of the machining tool 5 and the intersection point O between the rotation axis L1 and the swing axis L2 is set to the target radius Re. In the spherical surface machining operation, the machining target surface 40a of the lens material 40 is pressed against the tool surface 5a of the machining tool 5 by the biasing force F. Here, in the spherical surface machining operation, since the machining tool 5 swings while rotating, the spherical surface formed on the machining target surface 40a is such that the first contact point C1 corresponds to a locus that swings at the target radius Re while rotating around the rotation axis L1. Therefore, the spherical surface formed on the machining target surface 40a becomes the target lens surface G having the target radius Re. Therefore, a lens having the target lens surface G can be manufactured.

[0045] Further, the second spherical surface machining process ST5 repeats the second spherical surface machining process ST5 a preset first set number of times. Therefore, lenses having the target lens surface G can be continuously manufactured for the number of times the second spherical surface machining process ST5 is repeated.

[0046] Here, when the spherical surface machining operation is repeated by repeating the second spherical surface machining step ST5, wear occurs on the tool surface 5a of the machining tool 5. According to the findings obtained by the inventors' intensive studies, the distance between the first contact point C1 that contacts the machining target surface 40a of the lens material 40 on the tool surface 5a of the machining tool 5 and the intersection point O of the rotation axis L1 and the swing axis L2 is defined as the target radius Re. When the spherical surface machining operation of rotating and swinging the machining tool 5 is repeatedly performed, the tool surface 5a becomes a shape that highly accurately matches a spherical surface having the target radius due to wear. That is, when the spherical surface machining operation is repeated with the distance between the first contact point C1 and the intersection point O being the target radius Re, the machining tool 5 is dressed to have a spherical surface with the target radius Re on the tool surface 5a. In other words, by repeating the second spherical surface machining step ST5 after the first tool position setting step ST4 where the distance between the tool surface 5a of the machining tool 5 and the swing axis L2 is the target radius Re, the ball core type machining machine 1 not only has a spherical surface machining function for machining the lens material 40 into a spherical surface, but also has a tool forming function of wearing the tool surface 5a of the machining tool 5 to form a spherical surface having the same radius (target radius Re) as the target lens surface G on the tool surface 5a of the machining tool 5. Therefore, when the second spherical surface machining step ST5 is repeated, the target lens surface G can be formed on the machining target surface 40a of the lens material 40 with high precision and stably.

[0047] Here, in the conventional technology, when machining the machining target surface 40a of the lens material 40 into a spherical surface, it is common to improve the productivity of the lens by setting the spindle rotation speed for rotating the spindle to 7000 rpm to 10000 rpm. In contrast, in this example, in the second spherical surface machining step ST5, the spindle rotation speed is set to 2000 rpm or less. The reason for this is that if the spindle rotation speed is set to a lower rotation speed than before, the wear rate of the tool surface 5a of the machining tool 5 can be increased when repeating the second spherical surface machining step ST5, and a spherical surface having the same radius (target radius Re) as the target lens surface G can be formed on the tool surface 5a of the machining tool 5 in a short time. That is, by setting the spindle rotation speed to 2000 rpm or less, the tool surface 5a of the machining tool 5 is easily worn, and conditions can be arranged such that the tool surface 5a is easily dressed.

[0048] However, if the second spherical surface machining step ST5 is repeated further, the shape of the tool surface 5a changes due to wear to include an error with respect to the spherical surface having the target radius Re. Therefore, at the end stage of the second spherical surface machining step ST5, the spherical surface formed on the tool surface 5a having a radius different from the target radius Re and the lens material 40 no longer come into surface contact, and the tool surface 5a partially contacts the machining target surface 40a of the lens material 40. For example, as shown in FIG. 5, the tool surface 5a contacts the machining target surface 40a of the lens material 40 at the second contact point C2.

[0049] Therefore, after repeating the second spherical surface machining step ST5 a first set number of times, the second difference acquisition step ST7, the second tool position setting step ST8, and the third spherical surface machining step ST9 are performed in this order. In the second difference acquisition step ST7, as in the case shown in FIG. 6 (similar to the first difference acquisition step ST3), the machining target surface 40a is measured to obtain the second difference ΔR2 between the second machining radius R2 of the machining target surface 40a and the target radius Re. Further, in the second tool position setting step ST8, as in the case shown in FIG. 7 (similar to the first tool position setting step ST4), the machining tool 5 is moved in the direction along the rotation axis L1 of the spindle 6 by a distance corresponding to the second difference ΔR2, so that the distance between the second contact point C2 where the machining target surface 40a of the lens material 40 contacts the tool surface 5a of the machining tool 5 and the intersection point O of the rotation axis L1 and the swing axis L2 is set to the target radius Re of the target lens surface G.

[0050] Therefore, in the subsequent spherical surface machining operation, the target lens surface G can be formed on the machining target surface 40a of the lens material 40. Thus, in the third spherical surface machining step ST9, a lens having the target lens surface G can be manufactured.

[0051] If the third spherical surface machining process ST9 is repeated the preset number of times, the lenses having the target lens surface G can be continuously manufactured as many times as the third spherical surface machining process ST9 is repeated. Here, when the spherical surface machining operation is repeated, wear occurs on the tool surface 5a of the machining tool 5. According to the findings obtained by the inventors through intensive studies, when the spherical surface machining operation is repeated with the distance between the second contact point C2 where the machining target surface 40a of the lens material 40 contacts the tool surface 5a of the machining tool 5 and the intersection point O of the rotation axis L1 and the swing axis L2 as the target radius Re, the tool surface 5a will, due to wear, have a shape that highly accurately matches the spherical surface having the target radius. That is, when the spherical surface machining operation is repeated with the distance between the second contact point C2 and the intersection point O as the target radius Re, the machining tool 5 is dressed so that the tool surface 5a has a spherical surface with the target radius. In other words, by repeating the third spherical surface machining process ST9 after the second tool position setting process ST8 where the distance between the tool surface 5a of the machining tool 5 and the swing axis L2 is set as the target radius Re, the spherical machining machine 1 not only has the spherical surface machining function for machining the lens material 40 but also has a tool forming function of wearing the tool surface 5a of the machining tool 5 to form a spherical surface having the same radius (target radius Re) as the target lens surface G on the tool surface 5a of the machining tool 5. Therefore, according to the present invention, when the third spherical surface machining process ST9 is repeated, the target lens surface G can be formed on the machining target surface 40a of the lens material 40 with high precision and stably. Also, in this example, in the third spherical surface machining process ST9, the spindle rotation speed is set to 2000 rpm or less. Therefore, it is possible to arrange conditions such that the tool surface 5a of the machining tool 5 is easily worn and the tool surface 5a is easily dressed.

[0052] Note that the first set number of times for repeating the second spherical surface machining process ST5 can be empirically set based on the hardness of the lens material 40, the shape of the target lens surface G, the ease of wear of the tool surface 5a of the machining tool 5, and the like. Also, the second set number of times for repeating the third spherical surface machining process ST9 can be empirically set based on the hardness of the lens material 40, the shape of the target lens surface G, the ease of wear of the tool surface 5a of the machining tool 5, and the like. The first set number of times and the second set number of times may be the same. Also, the first set number of times and the second set number of times may be different.

[0053] (Function and Effect) In the conventional machining method, at the start point of the spherical surface machining operation, when the target lens surface G is a concave lens surface, it is common to establish the dimensional relationship of "the radius Rr of the machining target surface 40a of the lens material 40 < the radius Rt of the tool surface 5a = the target radius Re of the target lens surface G". Also, when the target lens surface G is a convex lens surface, it is common to establish the dimensional relationship of "the radius Rr of the machining target surface 40a of the lens material 40 > the radius Rt of the tool surface 5a = the target radius Re of the target lens surface G". That is, in the conventional machining method, the shape of the tool surface 5a of the machining tool 5 is transferred to the machining target surface 40a of the lens material 40. Therefore, the machining tool 5 has a spherical surface with the same radius as the target lens surface G on the tool surface 5a. Thus, "Rt = Re" is set.

[0054] In contrast, in this example, the radius Rt of the tool surface 5a and the target radius Re of the target lens surface G may be different. Further, even if there is an error between the shape of the tool surface 5a of the processing tool 5 and the spherical surface having the target radius, based on the first difference ΔR1 between the first processing radius of the surface 40a to be processed after the first spherical surface processing operation and the target radius Re, after adjusting the position of the processing tool 5, a spherical surface processing operation is performed to form a spherical surface having the target radius Re on the surface 40a to be processed. Therefore, the accuracy of the spherical shape of the tool surface 5a of the processing tool 5 can be tolerated more than before. More specifically, in the conventional processing method of transferring the shape of the tool surface 5a of the processing tool 5 to the surface 40a to be processed of the lens material 40, the shape of the tool surface of the processing tool used for spherical surface processing is required to be formed with an accuracy of plus / minus 1 μm or less with respect to the shape of the target lens surface G. In contrast, in this example, the error of the shape of the tool surface 5a of the processing tool 5 with respect to the spherical surface of the target lens surface G can be tolerated within plus / minus 20 μm. As a result, the molding of the tool surface of the processing tool becomes easy, so that the manufacture of the processing tool becomes easy and the productivity of the processing tool is improved.

[0055] Further, in this example, in the second spherical surface processing step ST5, the spherical surface processing operation of rotating and swinging the processing tool 5 with the distance between the first contact point C1 in contact with the surface 40a to be processed of the lens material 40 on the tool surface 5a of the processing tool 5 and the intersection point O of the rotation axis L1 and the swing axis L2 as the target radius Re is repeatedly performed. As a result, the tool surface 5a is dressed into a shape that highly accurately matches the spherical surface having the target radius due to wear. Therefore, when the spherical surface processing operation is repeated, the target lens surface G can be formed on the surface 40a to be processed of the lens material 40 with high precision and stably.

[0056] Furthermore, if the repetition of the second spherical surface machining process ST5 exceeds the first set number of times, and at this point, the shape of the tool surface 5a has changed due to wear to include an error with respect to the spherical surface having the target radius Re, then the second difference acquisition process ST7, the second tool position setting process ST8, and the third spherical surface machining process ST9 are performed in this order. In the second difference acquisition process ST7, the machining target surface 40a is measured to obtain a second difference ΔR2 between the second machining radius R2 of the machining target surface 40a and the target radius Re. Also, in the second tool position setting process ST8, by moving the machining tool 5 in the direction along the rotation axis L1 of the spindle 6 by a distance corresponding to the second difference ΔR2, the distance between the second contact point C2 where the machining target surface 40a of the lens blank 40 contacts the tool surface 5a of the machining tool 5 and the intersection point O of the rotation axis L1 and the swing axis L2 is set to the target radius Re of the target lens surface G. Thereby, in the third spherical surface machining process ST9, a lens having the target lens surface G can be manufactured.

[0057] Here, in the conventional technique, when the spherical surface machining operation is repeatedly performed and the shape of the tool surface 5a has changed due to wear to include an error with respect to the spherical surface having the target radius Re, the machining tool 5 is removed from the spindle 6, and unless a craftsman molds the tool surface 5a of the machining tool 5 into a spherical surface having the target radius Re and then mounts it on the spindle 6, the production of the lens cannot be resumed. In contrast, in this example, by setting the distance between the second contact point C2 where the machining target surface 40a of the lens blank 40 contacts the tool surface 5a of the machining tool 5 and the intersection point O of the rotation axis L1 and the swing axis L2 to the target radius Re of the target lens surface G, the production of the lens can be resumed. Therefore, the productivity of the lens is improved. Furthermore, since ΔR1 (ΔR2) can be obtained numerically, the target radius Re can be set by communication or input by an operator to the tool position controller 27, and advanced spherical surface molding technology by a craftsman's hand is not required.

[0058] In the third spherical surface machining step ST9, a spherical surface machining operation is repeatedly performed by rotating and swinging the machining tool 5 with the distance between the second contact point C2 in contact with the machining target surface 40a of the lens material 40 on the tool surface 5a of the machining tool 5 and the intersection point O of the rotation axis L1 and the swing axis L2 as the target radius Re. As a result, the tool surface 5a is dressed into a shape that highly accurately matches a spherical surface having the target radius due to wear. Therefore, when the spherical surface machining operation is repeated, the target lens surface G can be formed on the machining target surface 40a of the lens material 40 with high precision and stably.

[0059] Here, in this example, in the first difference acquisition step ST3, if the machining target surface 40a is measured and the first difference ΔR1 between the first machining radius R1 of the machining target surface 40a and the target radius Re is acquired, then in the first tool arrangement step, the machining tool 5 can be arranged at an appropriate position based on the first difference ΔR1. Therefore, it is easy to arrange the machining tool 5 at a position where the target lens surface G can be formed on the lens material 40.

[0060] Also, in the second difference acquisition step ST7, if the machining target surface 40a is measured and the second difference ΔR2 between the second machining radius R2 of the machining target surface 40a and the target radius Re is acquired, then in the second tool position setting step ST8, the machining tool 5 can be arranged at an appropriate position based on the second difference ΔR2. Therefore, it is easy to arrange the machining tool 5 at a position where the target lens surface G can be formed on the lens material 40.

[0061] In this example, in the spherical surface machining operation, the rotational speed of the spindle 6 is set to 2000 rpm or less. By doing so, it is possible to eliminate the need to adjust the dynamic balance of the machining tool 5. Therefore, the manufacturing of the machining tool 5 becomes easier. Also, since the spindle rotational speed is set to 2000 rpm or less, in the second spherical surface machining step ST5 and the third spherical surface machining step ST9, conditions can be arranged such that the tool surface 5a of the machining tool 5 is easily worn and the tool surface 5a is easily dressed. From the viewpoint of the machining efficiency of the machining target surface 40a, it is desirable that the rotational speed be 1500 rpm or more.

[0062] In the spherical surface machining operation, the lens holder 41 is rotated around the central axis L3. The rotation direction of the lens holder 41 is the same as the rotation direction of the spindle 6. By rotating the lens holder 41, the lens material 40 can be rotated integrally with the lens holder 41, thereby preventing or suppressing the occurrence of uneven cutting on the machining target surface 40a during the spherical surface machining operation. Here, if the holder rotation speed is less than 25% of the spindle rotation speed, the polishing of the portion where the tool surface 5a of the machining tool 5 is in contact on the machining target surface 40a of the lens material 40 may progress more than other portions, and the spherical surface accuracy may deteriorate. If the holder rotation speed is more than 35% of the spindle rotation speed, the difference in the rotation speeds between the machining tool 5 and the lens material 40 decreases, and the machining efficiency decreases.

[0063] Also, in this example, when the lens material 40 is carried around by the machining tool 5 and the holder rotation speed of the lens holder 41 exceeds the set holder rotation speed, the lens holder 41 is allowed to rotate beyond the holder rotation speed. Thereby, breakage of the lens material 40 during the spherical surface machining operation or roughness of the surface accuracy of the machining target surface 40a can be prevented or suppressed.

[0064] The spherical core type machining machine 1 of the present invention also includes a spindle 6 to which the machining tool 5 is detachably attached, a rotation mechanism 43 that rotates the spindle 6 around the rotation axis L1, a swing mechanism 9 that swings the spindle 6 around a predetermined swing axis L2 orthogonal to the rotation axis L1, a movement mechanism 8 that moves the machining tool 5 relative to the swing axis L2 by moving the spindle 6 in the direction of the rotation axis L1 along the rotation axis L1, a lens holder 41 that holds the lens material 40 at a position facing the tool surface 5a of the machining tool 5, and a biasing mechanism 63 that biases the lens holder 41 toward the spindle 6 side. The spherical core type machining machine 1 performs a spherical surface machining operation in which the machining tool 5 is swung around the swing axis L2 while the spindle 6 is rotated around the rotation axis L1 in a state where the machining target surface 40a of the lens material 40 held by the lens holder 41 is pressed against the tool surface 5a of the machining tool 5 attached to the spindle 6. The movement mechanism 8 moves the spindle 6 with a resolution of 1 μm or less.

[0065] According to the ball-core type processing machine 1 of this example, the moving mechanism 8 that moves the spindle 6 in the direction of the rotation axis L1 moves the spindle 6 with a resolution of 1 μm or less. As a result, on the tool surface 5a of the processing tool 5, the distance between the contact point that contacts the processing target surface 40a of the lens material 40 and the intersection point O of the rotation axis L1 and the swing axis L2 can be set with a resolution of 1 μm or less. Therefore, even if the shape of the tool surface 5a of the processing tool 5 does not match the spherical shape of the target lens surface G, it becomes easy to form the target lens surface G on the processing target surface 40a of the lens material 40.

[0066] (Other embodiments) In addition, in the spherical surface processing operation, it is not necessary to forcibly rotate the lens holder 41.

[0067] Here, in a processing method for spherically processing a lens material using a ball-core type processing machine, even when the target lens surface is a convex lens surface, the processing target surface 40a of the lens material 40 is a convex surface, and the tool surface of the processing tool is a concave surface, the present invention can be applied.

Claims

1. A processing method for performing a spherical surface processing operation using a spherical core type processing device, the processing target surface of a lens material held by a lens holder is pressed against a tool surface of a processing tool attached to a spindle, and the processing tool is swung around a swing axis perpendicular to the rotation axis of the spindle while rotating the spindle, a tool mounting step of holding the lens material in the lens holder and mounting the processing tool on the spindle; a first spherical machining step of performing the spherical machining operation for a set time; a first difference acquisition step of measuring the processing target surface after completion of the first spherical surface processing step to acquire a first processing radius of the processing target surface, and acquiring a first difference between a target radius of a target lens surface to be formed on the processing target surface and the first processing radius; a first tool position setting process for moving the spindle in a direction along the rotation axis while keeping the swing axis fixed, thereby moving the machining tool in a direction along the rotation axis by a distance corresponding to the first difference, and setting the distance between a first contact point on the tool surface of the machining tool that contacts the surface to be machined and an intersection point of the rotation axis and the swing axis as the target radius; a second spherical surface processing step of holding a new lens material in the lens holder and performing the spherical surface processing operation for the set time, A processing method characterized in that the set time is a processing time required to form a desired lens surface on a processing target surface of a lens material.

2. a second difference acquisition step of measuring the processing target surface of the final lens material after repeating the second spherical surface processing step a first set number of times, to acquire a second processing radius of the processing target surface, and acquiring a second difference between a target radius of a target lens surface to be formed on the processing target surface and the second processing radius; a second tool position setting process in which the spindle is moved in a direction along the rotation axis while the swing axis is fixed, thereby moving the machining tool in a direction along the rotation axis by a distance equivalent to the second difference, and the distance between a second contact point on the tool surface of the machining tool that contacts the surface to be machined and an intersection point of the rotation axis and the swing axis is set as the target radius; a third spherical surface processing step of holding a new lens material in the lens holder and performing the spherical surface processing operation for the set time, 2. The method according to claim 1, wherein the third spherical surface machining step is repeated a second set number of times.

3. 3. The machining method according to claim 1, wherein in the spherical surface machining operation, the spindle is rotated at a spindle rotation speed of 2000 rpm or less.

4. In the spherical surface processing operation, the lens holder is rotated around a central axis passing through a holder center of the lens holder and a material center of the lens material held by the lens holder; a rotation direction of the lens holder and a rotation direction of the spindle are the same; 3. The processing method according to claim 1, wherein a holder rotation speed at which the lens holder is rotated is 25% or more and 35% or less of a spindle rotation speed at which the spindle is rotated.

5. The processing method according to claim 4, characterized in that, when the lens material rotates along with the processing tool and the holder rotation speed of the lens holder exceeds the set holder rotation speed, the lens holder is allowed to rotate beyond the holder rotation speed.

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