Machining method and spherical center-type machining apparatus
The spherical core processing apparatus addresses precision and productivity issues by oscillating the tool and adjusting positions based on machining radius differences, enabling high-precision and stable lens surface formation through controlled tool wear and partial contact, enhancing manufacturing efficiency.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- KOJIMA ENG
- Filing Date
- 2024-11-18
- Publication Date
- 2026-05-21
Smart Images
Figure JP2024040837_21052026_PF_FP_ABST
Abstract
Description
Processing method and spherical core type processing machine
[0001] The present invention relates to a method for processing a lens material using a spherical core type processing machine and a spherical core type processing machine.
[0002] A spherical 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 spherical 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 spherical 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 spherical 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.
[0003] International Publication No. 2015 / 162789
[0004] In the spherical processing by a conventional spherical core type processing machine, the shape of the tool surface of the processing tool is transferred to the processing target surface of the lens material. Therefore, it is necessary for the processing tool to have a spherical surface having the same radius as the target lens surface on the tool surface. For this reason, it is required to mold the shape of the tool surface of the processing tool with an accuracy of plus / minus 1 μm (micrometer) or less. However, it is not easy to mold the shape of the tool surface of the processing tool with the required accuracy, and the manufacture of such a high-precision processing tool depends on the skill of a craftsman. Further, as the radius of the target lens surface becomes smaller, it becomes more difficult to measure the tool surface of the processing tool, so it becomes more difficult to accurately mold the tool surface of the processing tool. As a result, molding the tool surface of the processing tool requires a lot of time, hinders the stability of processing accuracy, and causes a decrease in productivity.
[0005] In view of the above problems, an object of the present invention is to propose a processing method that allows the accuracy of molding the tool surface of a processing tool in the initial stage to be more acceptable than before when performing spherical processing of a lens material using a spherical core type processing machine. Another object is to provide a spherical core type processing machine having a mechanism necessary for such a processing method.
[0006] To solve the above problems, the present invention provides a processing method using a spherical core processing apparatus, in which the surface to be processed of a lens material held in a lens holder is pressed against the surface of a processing tool mounted on a spindle, and the processing tool is oscillated around a pivot axis perpendicular to the rotation axis of the spindle while the spindle is rotated, wherein the processing method comprises a tool mounting step of holding the lens material in the lens holder and mounting the processing tool on the spindle, a first spherical processing step of performing the spherical processing operation for a set time, and measuring the surface to be processed. The method is characterized by comprising: a first difference acquisition step of acquiring a first machining radius of the surface to be machined and acquiring a first difference between the target radius of the lens surface to be formed on the surface to be machined and the first machining radius; a first tool position setting step of moving the machining tool by a distance corresponding to the first difference in the direction along the rotation axis, and setting the first distance between the tool surface of the machining tool and the pivot axis as the target radius; and a second spherical machining step of replacing the lens material with a new lens material held in the lens holder and performing the spherical machining operation for the set time.
[0007] In the present invention, in the first spherical machining step performed using a spherical core machining apparatus, the spherical machining operation forms a spherical surface on the surface of the lens material that is to be machined, corresponding to the trajectory of the rotation and oscillation of the first contact point on the tool surface of the machining tool that contacts the lens material. Therefore, the first machining radius obtained by measuring the surface of the machined material in the first difference acquisition step corresponds to the distance from the intersection of the rotation axis and the oscillation axis to the first contact point on the tool surface of the machining tool that contacts the lens material. Here, if the distance from the tool surface of the machining tool to the first contact point that contacts the lens material is set to the target radius of the target lens surface and the spherical machining operation is performed, the spherical surface corresponding to the trajectory of the rotation and oscillation of the first contact point will be a spherical surface having the target radius. Therefore, in the present invention, in the first difference acquisition step, the surface of the machined material is measured and the first difference between the first machining radius and the target radius of the surface of the machined material is obtained. Furthermore, in the subsequent first tool position setting step, the machining tool is moved in the direction along the rotation axis by a distance corresponding to the first difference, so that the distance between the first contact point on the tool surface of the machining tool that contacts the surface to be machined of the lens material and the intersection point of the rotation axis and the oscillation axis is defined as the target radius. Therefore, if a spherical machining operation (second spherical machining step) is performed after the first tool position setting step, the target lens surface can be formed on the surface to be machined of the lens material. In addition, in the present invention, if the surface to be machined is measured in the first difference acquisition step and the first difference between the first machining radius of the surface to be machined and the target radius is acquired, the machining tool can be positioned appropriately based on the first difference. Therefore, it is easy to position the machining tool in a position where the target lens surface can be formed on the lens material.
[0008] Thus, the machining method of the present invention does not assume that the shape of the tool surface of the machining tool matches a spherical surface having the target radius, or that the tool surface and the lens material make surface contact during the spherical machining operation. In other words, the machining method of the present invention allows for errors between the shape of the tool surface of the machining tool and a spherical surface having the target radius, and assumes that the tool surface and the surface of the lens material to be machined make partial contact. Furthermore, even if there is an error between the shape of the tool surface of the machining tool and a spherical surface having the target radius, a spherical surface having the target radius is formed on the surface to be machined by adjusting the position of the machining tool based on the first difference between the first machining radius and the target radius of the surface to be machined after the initial spherical machining operation, and then performing the spherical machining operation. Therefore, the accuracy of the spherical shape of the tool surface of the machining tool can be tolerated more than in conventional methods.
[0009] Next, the present invention has a second difference acquisition step, in which the second spherical processing step is repeated a number of times predetermined, the processing target surface of the last lens material is measured to obtain a second processing radius of the processing target surface, and a second difference is obtained between the target radius of the target lens surface to be formed on the processing target surface and the second processing radius; a second tool position setting step, in which the processing tool is moved in the direction along the rotation axis by a distance corresponding to the second difference, and the distance between the second contact point on the tool surface of the processing tool that contacts the processing target surface and the intersection point of the rotation axis and the oscillation axis is set as the target radius; and a third spherical processing step, in which a new lens material is held in the lens holder and the spherical processing operation is performed for the predetermined time, wherein the third spherical processing step is repeated a number of times predetermined.
[0010] According to the present invention, the second spherical machining process is repeated a number of times predetermined. Therefore, lenses having the target lens surface can be manufactured continuously for the number of times the second spherical machining process is repeated. When the spherical machining operation is repeated, wear occurs on the tool surface of the machining tool. According to the findings obtained through diligent research by the inventors, when a spherical machining operation is repeatedly performed in which the machining tool is rotated and oscillated with respect to the distance between the first contact point on the tool surface of the machining tool that contacts the surface of the lens material to be machined and the intersection point of the rotation axis and the oscillation axis, the tool surface will, due to wear, become a shape that precisely matches a sphere having the target radius. In other words, when the spherical machining operation is repeated with respect to the distance between the first contact point and the intersection point as the target radius, the machining tool is dressed with a sphere having the target radius on its tool surface. In other words, by repeating the second spherical machining process after the first tool position setting process, in which the distance between the tool surface of the machining tool and the pivot axis is set to the target radius, the spherical core machining machine not only has a spherical machining function for machining lens material into a spherical shape, but also a tool shaping function that wears down the tool surface of the machining tool to form a spherical surface on the tool surface of the machining tool that has the same radius as the target lens surface. Therefore, according to the present invention, when the second spherical machining process is repeated, the target lens surface can be formed on the surface of the lens material to be machined with high precision and stability.
[0011] If the second spherical machining process is repeated, the shape of the tool surface will change due to wear, resulting in a shape that includes errors relative to the spherical surface with the target radius. Therefore, towards the end of the second spherical machining process, the spherical surface formed on the tool surface during the spherical machining operation, which has a radius different from the target radius, will no longer be in full contact with the lens material, and the tool surface will only be in partial contact with the surface of the lens material being machined. Thus, in the second difference acquisition process performed after the second spherical machining process, the surface of the machined object is measured to obtain the second difference between the second machining radius of the surface of the machined object and the target radius. Furthermore, in the subsequent 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 surface of the lens material being machined and the intersection of the rotation axis and the oscillation axis is defined as the target radius. Therefore, in the subsequent spherical machining operation (third spherical machining process), the target lens surface can be formed on the surface of the lens material being machined. Furthermore, in the second difference acquisition process, by measuring the surface to be machined and acquiring the second difference between the second machining radius of the surface to be machined and the target radius, the machining tool can be positioned appropriately based on the second difference. Therefore, it is easy to position the machining tool in a position where the target lens surface can be formed on the lens material.
[0012] In conventional technology, if the spherical machining operation is repeated and the shape of the tool surface changes due to wear, resulting in an error relative to a spherical surface with the desired radius, lens manufacturing could not be resumed until the machining tool was removed from the spindle, the tool surface was reshaped by a craftsman into a spherical surface with the desired radius, and then reattached to the spindle. In contrast, according to the present invention, lens manufacturing can be resumed by setting the distance between the second contact point on the tool surface of the machining tool that contacts the surface of the lens material, and the intersection point of the rotation axis and the oscillation axis, to the desired radius of the target lens surface. Therefore, the productivity of lens manufacturing is improved.
[0013] Furthermore, by repeating the third spherical machining process a predetermined number of times, lenses having the desired lens surface can be manufactured continuously for the same number of times the third spherical machining process is repeated. However, when the spherical machining operation is repeated, wear occurs on the tool surface of the machining tool. According to the inventors' findings, when the spherical machining operation is repeatedly performed with the distance between the second contact point, which contacts the surface of the lens material on the tool surface, and the intersection point of the rotation axis and the oscillation axis as the target radius, the tool surface will, due to wear, become a shape that precisely matches a sphere having the target radius. In other words, when the spherical 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 with a sphere having the target radius on its tool surface. In other words, by repeating the second spherical machining process after the first tool position setting process, in which the distance between the tool surface of the machining tool and the pivot axis is set to the target radius, the spherical core machining machine not only has a spherical machining function for machining lens material into a spherical shape, but also a tool shaping function that wears down the tool surface of the machining tool to form a spherical surface on the tool surface of the machining tool that has the same radius as the target lens surface. Therefore, according to the present invention, when the third spherical machining process is repeated, the target lens surface can be formed on the surface of the lens material to be machined with high precision and stability.
[0014] In the present invention, it is desirable to set the spindle rotation speed for the spherical machining operation to 2000 rpm or less. By setting the spindle rotation speed lower than conventional methods, it becomes unnecessary to adjust the dynamic balance of the machining tool. Therefore, the manufacturing of the machining tool becomes easier. Here, the machining tool has the characteristic of being more prone to wear when performing spherical machining operations at low rotation speeds compared to when performing spherical machining operations at high rotation speeds. Therefore, by setting the spindle rotation speed lower than conventional methods, the wear rate of the tool surface of the machining tool can be increased when repeating the second or third spherical machining process. Thus, in the repeated second or third spherical machining process, a sphere 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, it can be seen that by setting the spindle rotation speed to 2000 rpm or less, conditions can be created in which the tool surface of the machining tool is prone to wear and dressing. Furthermore, from the viewpoint of machining efficiency of the workpiece surface, it is desirable to set the rotational speed to 1500 rpm or higher.
[0015] In the present invention, during the spherical machining operation, the lens holder is rotated about a central axis passing through the holder center of the lens holder and the material center of the lens material held in the lens holder, the rotation direction of the lens holder and the rotation direction of the spindle are the same, and the holder rotation speed for rotating the lens holder can be set to 25% or more and 35% or less of the spindle rotation speed for rotating the spindle. By rotating the lens holder, the lens material is rotated integrally with the lens holder, which prevents or suppresses the occurrence of uneven machining on the workpiece surface during the spherical machining operation. However, if the holder rotation speed is greater than 35% of the spindle rotation speed, the difference in rotational speed between the machining tool and the lens material decreases, reducing machining efficiency. If the holder rotation speed is less than 25% of the spindle rotation speed, machining may progress more in areas where the tool surface of the machining tool makes point contact with the workpiece surface of the lens material compared to other areas, which may result in poor spherical accuracy.
[0016] In this case, if 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 can be allowed to rotate beyond the set holder rotation speed. This prevents or suppresses damage to the lens material and roughness of the surface accuracy of the processed surface during spherical machining.
[0017] Next, the present invention relates to a spherical core machining machine that performs a spherical machining operation in which the machining tool is oscillated around the oscillating axis while the spindle is rotated around the rotation axis, with the machining tool being oscillated around the oscillating axis while the machining tool is oscillated around the oscillating axis, with the machining tool being detachably mounted on a spindle; a rotation mechanism for rotating the spindle around a predetermined oscillating axis perpendicular to the rotation axis; a lens holder for holding a lens material at a position facing the tool surface of the machining tool; and a biasing mechanism for biasing the lens holder toward the spindle, wherein the machining surface of the lens material held by the lens holder is pressed against the tool surface of the machining tool mounted on the spindle, and the machining tool is oscillated around the oscillating axis while the spindle is rotated around the rotation axis, the moving mechanism is characterized in that it moves the spindle in a direction perpendicular to the oscillating axis with a resolution of 1 μm or less.
[0018] According to the spherical core machining machine of the present invention, the movement mechanism that moves the spindle in the rotation axis direction moves the spindle with a resolution of 1 μm or less. This makes it possible to set the distance between the contact point on the tool surface of the machining tool that contacts the surface to be machined of the lens material and the intersection point of the rotation axis and the oscillation axis with a resolution of 1 μm or less. Therefore, even if the shape of the tool surface of the machining tool does not match the spherical shape of the target lens surface, it becomes easy to form the target lens surface on the surface to be machined of the lens material.
[0019] This is a front view of the lower shaft mechanism of a spherical core machining machine. This is a side view of the lower shaft mechanism of a spherical core machining machine. This is a front view of the upper shaft mechanism of a spherical core machining machine. This is a flowchart of the machining method. This is an explanatory diagram of the contact state between the machining tool and the lens material at the start of the first spherical machining process. This is an explanatory diagram of the shape of the machined surface of the lens material after the first spherical machining process. This is an explanatory diagram of the state after the machining tool has been moved in the first tool position setting process.
[0020] The following describes a spherical core processing machine and a method for processing lens materials using a spherical core processing machine, with reference to the drawings.
[0021] Figure 1 is a front view of the lower shaft mechanism of a spherical core machining center. Figure 2 is a side view of the lower shaft mechanism of a spherical core machining center. Figure 3 is a front view of the upper shaft mechanism of a spherical core machining center. As shown in Figures 1 and 2, the spherical core machining center 1 comprises a lower shaft mechanism 2 and an upper shaft mechanism 3. As shown in Figure 1, the lower shaft mechanism 2 comprises a spindle unit 7 equipped with a spindle 6 on which a machining tool 5 is mounted, a moving mechanism 8 that moves the spindle unit 7 in the direction of rotation along the rotation axis L1 of the spindle 6, and a rocking mechanism 9 that rocks the spindle unit 7 around a rocking axis L2 perpendicular to the rotation 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 machining tool 5 is detachably mounted on the spindle 6 via an adapter 14. As shown in Figure 2, the spindle unit 7 also includes an inverter 15 that controls the rotational speed of the spindle motor 11. The machining tool 5 mounted on the spindle 6 rotates around the rotation axis L1 by the drive of the spindle motor 11.
[0023] As shown in Figure 1, the moving mechanism 8 includes a pair of plates 18 positioned on both sides of the spindle 6. Each of the 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 stretched across the two linear guides 19. The frame 13 is movable along the linear guides 19. The moving mechanism 8 also includes a feed screw mechanism 21 and a tool position control servo motor 22, as shown in Figure 2. 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 on the plate 18. The tool position control servo motor 22 is supported on 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] The tool position control servo motor 22 receives a movement control command from the tool position controller 27. The tool position control servo motor 22 rotates in accordance with the movement control command from the tool position controller 27, moving the spindle unit 7 in the direction along the linear guide 19. In this example, a servo motor is used to drive the lead screw 24, and by making the pitch of the lead screw 24 highly accurate, the spindle unit 7 is moved with a resolution of 1 μm or less.
[0025] As shown in Figure 1, the rocking mechanism 9 comprises two shafts 31 fixed to each of a pair of plates 18. As shown in Figure 2, the rocking mechanism 9 also comprises a rocking control servo motor 32. One shaft 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 rocking 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 rocking control servo motor 32 is transmitted to the other shaft 31 via the timing belt 36.
[0026] The oscillation control servo motor 32 receives oscillation control commands from the oscillation controller 37. Based on the oscillation control commands input from the oscillation controller 37, the oscillation control servo motor 32 oscillates the shaft 31 at a predetermined oscillation angle and speed. As a result, the pair of frames 13 oscillate around the axes of the two shafts 31, and the spindle unit 7 and the moving mechanism 8 oscillate around the axes of the two shafts 31. The axes of the two shafts 31 are the oscillation axis L2 on which the spindle unit 7 and the moving mechanism 8 oscillate. The oscillation axis L2 is perpendicular to the rotation axis L1 of the spindle 6. In this example, the intersection point O of the oscillation axis L2 and the rotation axis L1 is located at the center of the sphere created on the tool surface of the machining tool 5 mounted on the spindle 6.
[0027] As shown in Figure 3, the upper shaft mechanism 3 includes a lens holder 41 for holding the lens material 40. The lens holder 41 holds the lens material 40 by vacuum suction. The upper shaft mechanism 3 also includes a rotation mechanism 43 for rotating the lens holder 41 and a biasing mechanism 63 that exerts a biasing force to bias 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 raising and lowering the lens holder 41.
[0028] The rotating mechanism 43 includes a lens rotation shaft 46 extending 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 circumference of the hollow shaft 49 via bearings 47 and 48. The hollow shaft 49 is held vertically movably by the sleeve 25 via a metal bearing 51. A rotary joint 52 is attached to the upper end of the lens rotation shaft 46, and transmits vacuum from a vacuum source (not shown) through the lens rotation shaft 46 to the lens holder 41. Therefore, the lens holder 41 can vacuum-suction the lens material 40.
[0029] The rotation mechanism 43 also 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. The central axis L3 also passes through the holder center of the lens holder 41 and the material center of the lens material 40 held in the lens holder 41.
[0030] The biasing mechanism 63 comprises a shaft head 64 provided at the upper end of the hollow shaft 49, a press base 65 attached to the upper side of the shaft head 64, and a biasing spring 67 positioned between the top 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. The biasing mechanism 63 also includes a bolt 68 that penetrates the top portion 66 of the sleeve 25 and contacts the upper end of the biasing spring 67. The amount of compression of the biasing spring 67 can be adjusted by moving the bolt 68 back and forth relative to the top portion 66.
[0031] Here, the central axis L3 on which the lens holder 41 rotates is perpendicular to the oscillation axis L2 on which the spindle unit 7 and the moving mechanism 8 oscillate in the lower axis mechanism 2. Also, the central axis L3 on which the lens holder 41 rotates passes through the intersection point O (see Figure 1) of the rotation axis L1 and the oscillation axis L2 of the spindle 6. The lifting mechanism 45 moves the rotation mechanism 43 and the biasing mechanism 63 in the direction of the central axis L3. As a result, the lifting 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 spherical core processing apparatus described above will be explained. Figure 4 is a flowchart of the processing operation. As shown in Figure 4, the processing operation first involves the tool mounting process ST1, the first spherical processing process ST2, the first difference acquisition process ST3, and the first tool position setting process ST4, in that order. Next, the second spherical processing process ST5 is repeated for a predetermined number of times (ST6). After that, the second difference acquisition process ST7 and the second tool position setting process ST8 are performed in that order, and then the third spherical processing process ST9 is repeated for a predetermined number of times (ST10).
[0033] In the tool mounting process ST1, the lens material 40 is held in the lens holder 41, and the processing tool 5 is mounted on the spindle 6. As shown in Figure 3, the lens material 40 is held by vacuum suction in the lens holder 41 with the processing surface 40a facing the spindle 6.
[0034] In the first spherical machining process ST2, the spherical machining operation is performed for a set time. During the spherical machining operation, the lens holder 41, which holds the lens material 40, is moved toward the spindle 6 by the lifting mechanism 45 of the upper axis mechanism 3. As a result, the spherical core machining machine 1 presses the surface 40a of the lens material 40 held by the lens holder 41 against the tool surface 5a of the machining tool 5 mounted on the spindle 6. In addition, the spindle motor 11 and the oscillation control servo motor 32 are driven during the spherical machining operation. As a result, the spherical core machining machine 1 rotates the spindle 6 and oscillates the machining tool 5 around an oscillation axis L2 that is perpendicular to the rotation axis L1 of the spindle 6. In this example, the spindle rotation speed that rotates the spindle 6 is controlled to 2000 rpm.
[0035] In addition, during the spherical machining 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, if the lens material 40 rotates along with the machining tool 5 and the holder rotation speed of the lens holder 41 exceeds the set holder rotation speed, the one-way clutch 57 functions to allow the lens holder 41 to rotate beyond the holder rotation speed. The set time for performing the spherical machining operation is the machining time required to form the target lens surface G on the machining surface 40a of the lens material 40. The set time is predetermined 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 machining tool 5, etc.
[0036] Figure 5 shows the state at the start of the spherical machining operation in the first spherical machining process ST2. Figure 5 is an explanatory diagram of the contact state between the machining tool 5 and the lens material 40. In Figure 5, the machining surface 40a of the lens material 40 held in the lens holder 41 is pressed by a biasing force F against the tool surface 5a of the machining tool 5 mounted on the spindle 6.
[0037] In the example shown in Figure 5, the radius Rr of the workpiece surface 40a of the lens material 40, the radius Rt of the tool surface 5a of the processing tool 5, and the target radius Re of the target lens surface G are all different. Furthermore, the dimensional relationship "radius Rr of the workpiece surface 40a of the lens material 40 < radius Rt of the tool surface 5a < target radius Re of the target lens surface G" holds true. In this dimensional relationship, the tool surface 5a partially contacts the workpiece surface 40a of the lens material 40. Here, the point where the tool surface 5a of the processing tool 5 contacts the workpiece surface 40a is called the contact point C.
[0038] Figure 6 is an explanatory diagram of the shape of the processing surface 40a of the lens material 40 after the first spherical processing step ST2. In the first difference acquisition step ST3, first, the shape of the processing surface 40a of the lens material 40 after the spherical processing operation is completed is measured, and the first processing radius R1 of the sphere formed on the processing surface 40a is acquired. The measurement of the shape of the processing surface 40a and the acquisition of the first processing radius R1 are performed by removing the lens material 40 from the lens holder 41 and measuring with a lens surface shape measuring machine (not shown). In addition, the first difference ΔR1 between the first processing radius R1 and the target radius Re of the target lens surface G is acquired.
[0039] The first machining radius R1 obtained in the first difference acquisition step ST3 corresponds to the distance LC (see Figure 5) between the contact point C where the tool surface 5a of the machining tool 5 contacts the surface to be machined 40a, and the intersection point O of the rotation axis L1 and the oscillation axis L2. In other words, in spherical machining, the machining tool 5 rotates and oscillates, so the spherical surface formed on the surface to be machined 40a is the trajectory of the contact point C rotating around the rotation axis L1 and oscillating around the intersection point O. Here, since the target radius Re of the target lens surface G is a known value, this value can be stored in the surface shape measuring machine, and the first difference ΔR1 can be automatically output from the surface shape measuring machine when the measurement of the shape of the surface to be machined 40a is completed.
[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 via communication from the surface shape measuring machine. Alternatively, the operator may manually input the first difference ΔR1 acquired in the first difference acquisition step ST3 to the tool position controller 27.
[0041] The tool position control servo motor 22 rotates in response to a movement control instruction from the tool position controller 27, moving the spindle unit 7 by a distance corresponding to the first difference ΔR1 in the direction along the rotation axis L1 of the spindle 6 (the direction along the linear guide 19). The direction of movement of the spindle unit 7 is in the 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. Figure 7 is an explanatory diagram of the state in which the machining tool 5 has been moved by a distance corresponding to the first difference ΔR1 in the first tool position setting step ST4. In Figure 7, the machining tool 5 has been moved by a distance corresponding to the first difference ΔR1, and the machining target surface 40a of the lens material 40 held in the lens holder 41 is being pressed by a biasing force F against the tool surface 5a of the machining tool 5 mounted on the spindle 6.
[0042] In the example shown in Figure 6, the first machining radius R1 of the 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 that brings it closer to the lens material 40 (lens holder 41) by a first difference ΔR1. As a result, the machining tool 5 is positioned so that the distance from the first contact point C1 to the intersection point O matches the target radius Re of the target lens surface G. Here, since the machining tool 5 rotates around the rotation axis L1 and oscillates around the oscillation axis L2 during the spherical machining operation, the distance from the first contact point C1 to the intersection point O can be rephrased as the distance from the tip of the tool surface 5a of the machining tool 5 to the intersection point O.
[0043] In addition, 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 arranged 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 step ST5, a spherical surface machining operation is performed in a state where the distance between the first contact point C1 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 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 corresponds to a locus in which the first contact point C1 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] In addition, the second spherical surface machining step ST5 is repeated the preset first set number of times. Therefore, lenses having the target lens surface G can be continuously manufactured by the number of times the second spherical surface machining step ST5 is repeated.
[0046] Here, by repeating the second spherical machining process ST5, the spherical machining operation is repeated, causing wear to occur on the tool surface 5a of the machining tool 5. According to the findings obtained through diligent research by the inventors, when the spherical machining operation is repeatedly performed by rotating and oscillating the machining tool 5 with the distance between the first contact point C1, which contacts the 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 oscillation axis L2 as the target radius Re, the tool surface 5a will, due to wear, become a shape that precisely matches a sphere with the target radius. In other words, when the spherical machining operation is repeated with the distance between the first contact point C1 and the intersection point O as the target radius Re, the machining tool 5 is dressed with a sphere of the target radius Re on its tool surface 5a. In other words, by repeating the second spherical machining process ST5 after the first tool position setting process ST4, in which the distance between the tool surface 5a of the machining tool 5 and the pivot axis L2 is set to the target radius Re, the spherical core machining machine 1 not only has a spherical machining function for machining the lens material 40 into a spherical shape, but also a tool shaping function that wears down the tool surface 5a of the machining tool 5 to form a sphere on the tool surface 5a of the machining tool 5 having the same radius (target radius Re) as the target lens surface G. Therefore, when the second spherical machining process ST5 is repeated, the target lens surface G can be formed on the machining surface 40a of the lens material 40 with high precision and stability.
[0047] In conventional technology, when spherically machining the processing surface 40a of the lens material 40, the spindle rotation speed is generally set to 7,000 rpm to 10,000 rpm to improve the productivity of the lens. In contrast, in this example, the spindle rotation speed is set to 2,000 rpm or less in the second spherical machining step ST5. The reason for this is that by setting the spindle rotation speed lower than conventional methods, the wear rate of the tool surface 5a of the machining tool 5 can be increased when repeating the second spherical 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. In other words, by setting the spindle rotation speed to 2,000 rpm or less, conditions can be created in which the tool surface 5a of the machining tool 5 is easily worn and 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 a shape that includes 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, similar to the case shown in FIG. 6 (similar to the first difference acquisition step ST3), 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. Further, in the second tool position setting step ST8, similar to 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 spherical surface machining operation performed thereafter, 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 machining process ST9 is repeated a predetermined number of times, lenses having the target lens surface G can be manufactured continuously for the same number of times the third spherical machining process ST9 is repeated. When the spherical machining operation is repeated, wear occurs on the tool surface 5a of the machining tool 5. According to the findings obtained through diligent research by the inventors, when the spherical machining operation is repeated with the distance between the second contact point C2, which contacts the 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 oscillation axis L2 set as the target radius Re, the tool surface 5a will, due to wear, become a shape that precisely matches a sphere having the target radius. In other words, when the spherical machining operation is repeated with the distance between the second contact point C2 and the intersection point O set as the target radius Re, the machining tool 5 is dressed with a sphere having the target radius on its tool surface 5a. In other words, by repeating the third spherical machining process ST9 after the second tool position setting process ST8, in which the distance between the tool surface 5a of the machining tool 5 and the pivot axis L2 is set to the target radius Re, the spherical core machining machine 1 not only has a spherical machining function for machining the lens material 40 into a spherical shape, but also a tool shaping function that wears down the tool surface 5a of the machining tool 5 to form a sphere on the tool surface 5a of the machining tool 5 having the same radius (target radius Re) as the target lens surface G. Therefore, according to the present invention, when the third spherical machining process ST9 is repeated, the target lens surface G can be formed on the machining surface 40a of the lens material 40 with high precision and stability. In this example, the spindle rotation speed is set to 2000 rpm or less in the third spherical machining process ST9. Therefore, conditions can be set up in which the tool surface 5a of the machining tool 5 is easily worn down and the tool surface 5a is easily dressed.
[0052] The first set number of times the second spherical processing step ST5 is repeated can be set empirically based on the hardness of the lens material 40, the shape of the target lens surface G, the wear resistance of the tool surface 5a of the processing tool 5, etc. Similarly, the second set number of times the third spherical processing step ST9 is repeated can be set empirically based on the hardness of the lens material 40, the shape of the target lens surface G, the wear resistance of the tool surface 5a of the processing tool 5, etc. The first set number and the second set number may be the same. Also, the first set number and the second set number may be different.
[0053] (Effects) In conventional processing methods, at the start of the spherical processing operation, if the target lens surface G is a concave lens surface, it is common to establish the dimensional relationship "radius Rr of the processing surface 40a of the lens material 40 < radius Rt of the tool surface 5a = target radius Re of the target lens surface G". Also, if the target lens surface G is a convex lens surface, it is common to establish the dimensional relationship "radius Rr of the processing surface 40a of the lens material 40 > radius Rt of the tool surface 5a = target radius Re of the target lens surface G". In other words, in conventional processing methods, the shape of the tool surface 5a of the processing tool 5 is transferred to the processing surface 40a of the lens material 40. Therefore, the processing tool 5 has a spherical surface on its tool surface 5a that has the same radius as the target lens surface G. Thus, "Rt = Re".
[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 differ. Furthermore, 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, the position of the processing tool 5 is adjusted based on the first difference ΔR1 between the first processing radius and the target radius Re of the processing target surface 40a after the initial spherical processing operation, and then the spherical processing operation is performed to form a spherical surface having the target radius Re on the processing target surface 40a. Therefore, the accuracy of the spherical shape of the tool surface 5a of the processing tool 5 can be tolerated more than in the conventional method. More specifically, in the conventional processing method in which the shape of the tool surface 5a of the processing tool 5 is transferred to the processing target surface 40a of the lens material 40, the shape of the tool surface of the processing tool used for spherical processing is required to be molded with an accuracy of plus / minus 1 μm or less relative to the shape of the target lens surface G. In contrast, in this example, the error between the shape of the tool surface 5a of the processing tool 5 and the spherical surface of the target lens surface G can be tolerated at plus / minus 20 μm or less. This makes it easier to shape the surface of the machining tool, thus simplifying the manufacturing of the machining tool and improving the productivity of the machining tool.
[0055] Furthermore, in this example, in the second spherical machining step ST5, the machining tool 5 is repeatedly rotated and oscillated, with the distance between the first contact point C1, where the tool surface 5a of the machining tool 5 contacts the machining target surface 40a of the lens material 40, and the intersection point O of the rotation axis L1 and the oscillation axis L2 being the target radius Re. As a result, the tool surface 5a is dressed by wear to a shape that precisely matches a sphere with the target radius. Therefore, when the spherical 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 stability.
[0056] Furthermore, if the number of repetitions of the second spherical 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 relative to a sphere having the target radius Re, then the second difference acquisition process ST7, the second tool position setting process ST8, and the third spherical machining process ST9 are performed in this order. In the second difference acquisition process ST7, the workpiece surface 40a is measured to obtain the second difference ΔR2 between the second machining radius R2 of the workpiece surface 40a and the target radius Re. Also, in the second tool position setting process ST8, 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 on the tool surface 5a of the machining tool 5 that contacts the workpiece surface 40a of the lens material 40 and the intersection point O of the rotation axis L1 and the oscillation axis L2 is set to the target radius Re of the target lens surface G. As a result, in the third spherical machining process ST9, a lens having the target lens surface G can be manufactured.
[0057] In conventional technology, if the spherical machining operation is repeated and the shape of the tool surface 5a changes due to wear, resulting in an error relative to a spherical surface with the target radius Re, lens manufacturing could not be resumed until the machining tool 5 was removed from the spindle 6, the tool surface 5a of the machining tool 5 was reshaped into a spherical surface with the target radius Re by a craftsman, and then reattached to the spindle 6. In contrast, in this example, lens manufacturing can be resumed by setting the distance between the second contact point C2, which 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 oscillation axis L2, to the target radius Re of the target lens surface G. Therefore, lens productivity is improved. Furthermore, since ΔR1 (ΔR2) is obtained numerically, the target radius Re can be set by communication or input to the tool position controller 27 by an operator, eliminating the need for advanced spherical molding techniques by a craftsman.
[0058] Furthermore, in the third spherical machining step ST9, the machining tool 5 is repeatedly rotated and oscillated, with the distance between the second contact point C2, where the tool surface 5a of the machining tool 5 contacts the surface 40a of the lens material 40, and the intersection point O of the rotation axis L1 and the oscillation axis L2 being the target radius Re. As a result, the tool surface 5a is dressed by wear to a shape that precisely matches a sphere with the target radius. Therefore, when the spherical machining operation is repeated, the target lens surface G can be formed on the surface 40a of the lens material 40 with high precision and stability.
[0059] In this example, in the first difference acquisition step ST3, the surface to be machined 40a is measured and the first difference ΔR1 between the first machining radius R1 and the target radius Re of the surface to be machined 40a is obtained. Then, in the first tool placement step, the machining tool 5 can be placed in an appropriate position based on the first difference ΔR1. Therefore, it is easy to place the machining tool 5 in a position where the target lens surface G can be formed on the lens material 40.
[0060] Furthermore, in the second difference acquisition step ST7, if the workpiece surface 40a is measured and the second difference ΔR2 between the second machining radius R2 of the workpiece surface 40a and the target radius Re is obtained, then in the second tool position setting step ST8, the machining tool 5 can be positioned appropriately based on the second difference ΔR2. Therefore, it is easy to position the machining tool 5 in a position where the target lens surface G can be formed on the lens material 40.
[0061] In this example, the rotational speed of the spindle 6 is set to 2000 rpm or less during the spherical machining operation. This eliminates the need to adjust the dynamic balance of the machining tool 5. Therefore, the manufacturing of the machining tool 5 becomes easier. Furthermore, by setting the spindle rotational speed to 2000 rpm or less, conditions can be created in the second spherical machining step ST5 and the third spherical machining step ST9 where the tool surface 5a of the machining tool 5 is more easily worn and the tool surface 5a is more easily dressed. However, from the viewpoint of machining efficiency of the workpiece surface 40a, it is desirable to set the rotational speed to 1500 rpm or more.
[0062] Furthermore, during the spherical machining operation, the lens holder 41 is rotated around the central axis L3. The rotation direction of the lens holder 41 and the rotation direction of the spindle 6 are the same. By rotating the lens holder 41, the lens material 40 is rotated together with the lens holder 41, which prevents or suppresses uneven machining on the workpiece surface 40a during the spherical machining operation. However, if the holder rotation speed is set to less than 25% of the spindle rotation speed, the polishing of the part of the workpiece surface 40a of the lens material 40 that is in contact with the tool surface 5a of the machining tool 5 may progress more than other parts, which may result in poor spherical accuracy. If the holder rotation speed is set to more than 35% of the spindle rotation speed, the difference in rotational speed between the machining tool 5 and the lens material 40 decreases, reducing machining efficiency.
[0063] Furthermore, in this example, if the lens material 40 rotates along with the processing 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 set holder rotation speed. This prevents or suppresses damage to the lens material 40 and roughness of the surface accuracy of the processed surface 40a during the spherical machining operation.
[0064] Furthermore, the spherical core machining machine 1 of the present invention includes a spindle 6 on which a machining tool 5 is detachably mounted, a rotation mechanism 43 that rotates the spindle 6 around a rotation axis L1, a rocking mechanism 9 that rocks the spindle 6 around a predetermined rocking axis L2 perpendicular to the rotation axis L1, a moving mechanism 8 that moves the machining tool 5 relative to the rocking 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. The spherical core machining machine 1 performs a spherical machining operation by rotating the spindle 6 around the rotation axis L1 and rocking the machining tool 5 around the rocking axis L2 while pressing the surface 40a of the lens material 40 held by the lens holder 41 against the tool surface 5a of the machining tool 5 mounted on the spindle 6. The moving mechanism 8 moves the spindle 6 with a resolution of 1 μm or less.
[0065] In the spherical core machining machine 1 of this example, the movement 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. This makes it possible to set the distance between the contact point on the tool surface 5a of the machining tool 5 that contacts the surface 40a of the lens material 40 and the intersection point O of the rotation axis L1 and the oscillation axis L2 with a resolution of 1 μm or less. Therefore, even if the shape of the tool surface 5a of the machining 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 surface 40a of the lens material 40.
[0066] (Other embodiments) In addition, it is not necessary to forcibly rotate the lens holder 41 during the spherical processing operation.
[0067] Herein, in a processing method for spherically processing a lens material using a spherical core processing machine, the present invention can also be applied 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 concave.
Claims
1. A machining method using a spherical core machining apparatus, in which the surface to be machined of a lens material held in a lens holder is pressed against the tool surface of a machining tool mounted on a spindle, and the machining tool is oscillated around a pivot axis perpendicular to the rotation axis of the spindle while the spindle is rotated, comprising: a tool mounting step of holding the lens material in the lens holder and mounting the machining 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 surface to be machined to obtain a first machining radius of the surface to be machined to obtain a first difference between the target radius of the target lens surface to be formed on the surface to be machined and the first machining radius; a first tool position setting step of moving the machining tool by a distance corresponding to the first difference in the direction along the rotation axis, so that the distance between the first contact point on the tool surface of the machining tool that contacts the surface to be machined and the intersection of the rotation axis and the pivot axis is the target radius; A processing method characterized by comprising: a second spherical processing step, in which the new lens material is held in the lens holder and the spherical processing operation is performed for a set time.
2. The processing method according to claim 1, comprising: repeating the second spherical processing step for a predetermined number of first set numbers, measuring the processing target surface of the last lens material to obtain the second processing radius of the processing target surface, and obtaining the second difference between the target radius of the target lens surface to be formed on the processing target surface and the second processing radius; moving the processing tool by a distance corresponding to the second difference in the direction along the rotation axis, so that the distance between the second contact point on the tool surface of the processing tool that contacts the processing target surface and the intersection point of the rotation axis and the oscillation axis is the target radius; and holding the new lens material in the lens holder and performing the spherical processing operation for the set time, wherein the third spherical processing step is repeated for a predetermined number of second set numbers.
3. The machining method according to claim 1 or 2, characterized in that the spindle rotation speed for rotating the spindle in the spherical machining operation is 2000 rpm or less.
4. The processing method according to claim 1 or 2, characterized in that, in the spherical processing operation, the lens holder is rotated about a central axis passing through the holder center of the lens holder and the material center of the lens material held in the lens holder, the direction of rotation of the lens holder and the direction of rotation of the spindle are the same, and the holder rotation speed for rotating the lens holder is 25% or more and 35% or less of the spindle rotation speed for rotating the spindle.
5. The processing method according to claim 4, characterized in that, if 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.
6. A spherical core machining machine that performs a spherical machining operation in which the machining tool is oscillated around the oscillating axis while the spindle is rotated around the rotation axis, with the machining tool being oscillated around the oscillating axis while the machining tool is oscillated, with the machining tool being oscillated around the oscillating axis while the machining tool is oscillated, with the machining surface of the lens material held in the lens holder pressed against the tool surface of the machining tool mounted on the spindle, wherein the moving mechanism moves the spindle in a direction perpendicular to the oscillating axis with a resolution of 1 μm or less.