JPH07205006A - Lens grinding method - Google Patents

Abstract

PURPOSE:To provide a lens grinding method by which both rough grinding and finish grinding can be carried out by one grindstone, and also efficient lens finishing can be enabled. CONSTITUTION:Grinding is carried out by turning a chuck while feeding coolant 7 through a nozzle 6, and by turning a conductive grindstone 4. Simultaneously, in the first half of the grinding, the conductive grindstone 4 is made positive by means of a power supply device, and an electrode 5 is made negative, and a d.c. pulse voltage is applied for carrying out rough grinding. Next, while keeping the polarity to be applied as it is, the voltage is changed to a d.c. working voltage. Otherwise, the conductive grindstone 4 is made negative, and the electrode 5 is made positive, and a d.c. working voltage is applied. Then, a film is formed on the grinding surface 4a, and the amount of projection 1 of the diamond abrasive grain 20 from the grinding surface 4a is reduced. On the latter half of grinding, finish grinding is carried out while keeping this condition. After completion of finish grinding, spark-out is carried out for finishing grinding.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spherical surface forming process using a grinding wheel for a lens, and more particularly to a spherical surface forming process method to which electrolytic dressing is applied.

[0002]

2. Description of the Related Art Conventionally, as a lens spherical surface forming process by electrolytic dressing, for example, an invention described in Japanese Patent Application Laid-Open No. 3-60973 has been proposed. The above-described invention is, as shown in FIGS. 9 and 10, a chuck 61 configured to be rotatable.
A spherical member 62 is held by. Spherical member 62
A conductive grinding tool 64 having a swivel angle α is rotatably opposed to and held by the shaft center 63. The grinding surface 65 of the conductive grinding tool 64 is made of a sintered alloy obtained by specially blending abrasive grains such as diamond powder and metal powder such as Cu, Sn and Fe, and heat-treating.

In the vicinity of the grinding surface 65 of the conductive grinding tool 64, an electrode 66 formed in a shape similar to the processing curvature RA of the spherical surface member 62 is installed oppositely with a slight gap l. The electrode 66 is connected to the (-) pole of the DC power supply device 67. The (+) pole of the DC power supply device 67 is connected to the brush 68 that contacts the outer peripheral surface of the conductive grinding tool 64.
Further, a nozzle 70 for supplying the coolant 69 is provided in a slight gap 1 between the grinding surface 65 of the conductive grinding tool 64 and the electrode 66.

In the spherical surface generating method using the apparatus having the above structure, first, the chuck 61 holding the spherical member 62 is rotated, the conductive grinding tool 64 is rotated, and the grinding surface 65 is changed to the spherical member. Grinding is performed by contacting the surface to be ground 62. At the same time, the (+) pole is applied from the DC power supply device 67 to the conductive grinding tool 64 via the brush 68, and the electrode 66
The (-) pole is applied to. Further, grinding is performed while supplying the coolant 69 from the nozzle 70. As described above, the grinding surface 65 of the conductive grinding tool 64 is evenly and uniformly dressed, and stable spherical surface creation processing can be performed.

[0005]

However, in the above-mentioned electrolytic dressing of the prior art, the main purpose is to prevent uneven wear and clogging of the grinding tool caused by working, and to prevent the amount of protrusion of the abrasive grains in the grinding tool. I couldn't control it. Therefore, there is a problem that it is not possible to efficiently grind the lens by performing rough grinding and finish grinding with one grindstone.

Therefore, the present invention has been made in view of the above problems in the prior art, and an object thereof is to provide a lens grinding method capable of efficiently processing a lens with one grindstone.

[0007]

1 to 4 are conceptual views showing the present invention. The processing method of the present invention uses an existing spherical surface creating machine (hereinafter referred to as a CG machine), and the description will be given mainly on the vicinity of the grinding surface of the conductive grinding wheel and the electrode.
A chuck (not shown) loaded with a lens (not shown) while supplying a coolant (weakly-electric grinding liquid) 7 from a nozzle 6.
While rotating the conductive grinding wheel 4,
The grinding surface 4a formed at the end is brought into contact with the processing surface of the lens to perform grinding processing. Simultaneously with this processing, a DC pulse voltage of 140 V, 10 A or more is applied by using a conductive grinding wheel 4 as a plus and an electrode 5 as a minus from a power supply device (not shown), and a discharge is generated between the two. By this discharge, as shown in FIG. 1, the iron-based bond 21 is removed, and the protrusion amount l of the diamond abrasive grains 20 from the grinding surface 4a is l.
Grows larger. In the first half of processing, this state is maintained and rough grinding is performed.

Next, the polarity applied to the conductive grinding wheel 4 and the electrode 5 is changed to the DC steady voltage of 60 V and 3 A with the same polarity. Alternatively, the conductive grinding wheel 4 is made negative, the electrode 5 is made positive, and a steady DC voltage of 60 A, 3 A is applied. Then, as shown in FIG. 2, the coating film 23 is formed on the grinding surface 4a, and the protrusion amount l'of the diamond abrasive grains 20 from the grinding surface 4a becomes small. In the latter half of processing, this state is maintained and finish grinding is performed. After finishing grinding, spark out is performed to finish the grinding process.

[0009]

When a DC pulse voltage of 140 V, 10 A or more is applied with the conductive grinding wheel 4 being positive and the electrode 5 being negative, discharge is generated between the iron-based bond 21 of the conductive grinding wheel 4 and the electrode 5. Occur. Then, the iron-based bond 21 is removed by the thermal shock caused by the discharge, the protrusion amount l of the diamond abrasive grains 20 from the ground surface 4a increases, and the notch for the lens is large, so that the lens can be efficiently processed (see FIG. 1).

On the other hand, when the conductive grinding wheel 4 is positive, the electrode 5 is negative, and a steady DC voltage of 60 V, 3 A is applied, iron in the iron-based bond 21 is ionized and Fe ^{3+ is added.}
And oxygen ions O ²⁻ in the coolant (weakly-electric grinding liquid) 7 combine to form Fe ₂ O ₃ . This Fe ₂ O
₃ adheres to the grinding surface 4a to form the coating 23 (see FIG. 3). Therefore, the diamond abrasive grains 20 from the grinding surface 4a
The amount of protrusion l'of is small, the amount of cut into the lens is small, and processing with small cracks can be performed.

Further, the conductive grinding wheel 4 is set to a negative value,
When a DC steady voltage of 60 V and 3 A is applied with the copper (Cu) electrode 5 as a plus, the metal forming the electrode 5 is ionized and moves to the grinding surface 4 a of the conductive grinding wheel 4. The ionized copper receives electrons on the grinding surface 4a of the conductive grinding wheel 4, adheres to the surface of the grinding surface 4a as metallic copper, and forms a film 23 (see FIG. 4). Therefore, the protrusion amount l'of the diamond abrasive grains 20 from the grinding surface 4a becomes small, the cutting amount to the lens is small, and the processing with small cracks can be performed.

[0012]

Embodiment 1 FIGS. 5 and 6 show an apparatus used in this embodiment, FIG. 5 is a schematic configuration diagram of a main portion, and FIG. 6 is a schematic circuit diagram of a power supply device. It should be noted that this embodiment will be described with reference to FIGS. A lens 1 is held on a chuck 2 provided at the tip of a work shaft 3 of a CG machine (not shown). The lens 1 is held by a work shaft 3 so as to be rotatable and movable back and forth.

Reference numeral 4 is a conductive grinding wheel fixed to a grindstone shaft (not shown) of the GC machine. The conductive grinding grindstone 4 is rotatable by the grindstone shaft and is capable of swinging angularly with respect to the axis of the work shaft 3. Is held. The electroconductive grinding wheel 4 is obtained by fixing the diamond abrasive grains 20 of mesh # 325 with an iron-based bond 21. The ground surface 4a of the electroconductive grinding wheel 4 is separated from the ground surface 4a by a distance of 0.1 mm and the electrode 5 made of carbon is used.
Is installed.

A carbon power feeding brush 8 is disposed in contact with the outer peripheral surface of the conductive grinding wheel 4. The electrode 5 and the power feeding brush 8 are connected to the negative pole and the positive pole of the power supply device 9, respectively, and are configured to be able to apply a voltage.
The power supply device 9 has a voltage adjustment button 3 for adjusting the applied voltage.
0 and a steady / pulse switch 31 for switching the applied voltage to steady or pulse. A nozzle 6 supplies the coolant 7 to the processing area. As the coolant 7, a weakly electric grinding liquid for electrolysis was used.

In the present embodiment, a spherical lens having a diameter of 120, a radius of curvature of 35 mm and a material of LAH66 was machined by using the apparatus having the above-mentioned structure. The lens 1 is loaded on the chuck 2. Next, the coolant 7 is supplied, the conductive grinding wheel 4 is rotated at 14,000 rpm, and at the same time, the voltage adjustment button 30 of the power supply device 9 is set to 140V so that
The pulse changeover switch 31 is set to a pulse, and a DC pulse voltage of 140 V is set to the electrode 5 and the conductive grinding wheel 4 so that the peak current is 10 A. Then, electric discharge occurs between the electrode 5 and the iron-based bond 21 of the conductive grinding wheel 4, and the iron-based bond 21 is removed.

By positively removing the iron-based bond 21, the protrusion amount l of the diamond abrasive grain 20 is 0.025.
mm or more (see FIG. 1). The chuck 2 loaded with the lens 1 is rotated at 400 rpm, and the conductive grinding wheel 4 is cut into the processed surface of the lens 1.
Cutting is performed in this state up to 0.4 mm out of the total cutting depth of 0.6 mm, and rough grinding is performed. Then, the voltage adjustment button 30 of the power supply device 9 is set to 60V, and the steady / pulse changeover switch 3
1 is set to a steady state, the voltage applied to the electrode 5 and the conductive grinding wheel 4 is set to a DC steady state voltage of 60 V, and the peak current is set to 3 A.

Then, Fe ³⁺ ions in the iron-based bond 21 and O ²⁻ ions in the coolant 7 combine to form a film (Fe ₂ O ₃ ) 23 on the ground surface 4a of the conductive grinding wheel 4. (See Figure 3). By forming the coating film 23, the protrusion amount l ′ of the diamond abrasive grains 20 is 0.01 mm.
Kept below. The remaining 0.2 mm of the total depth of cut is cut in this state and finish grinding is performed. After finishing the cut, spark out for 5 seconds.

Thereafter, the conductive grinding wheel 4 is returned to its original position, at the same time, the rotation of the chuck 2 and the conductive grinding wheel 4 is stopped, the supply of the coolant 7 is stopped, and the lens 1 is removed from the chuck 2. As a result, the grinding process, which used to be performed using two types of whetstones in the past, is 3 μm, which is the same as the conventional one with one whetstone.
It was possible to process to a surface roughness of Rmax.

According to this embodiment, rough grinding and finish grinding can be performed with one grindstone, and the lens can be efficiently processed.

[0020]

[Embodiment 2] FIGS. 7 and 8 show an apparatus used in this embodiment, FIG. 7 is a schematic configuration diagram of a main portion, and FIG. 8 is a schematic circuit diagram of a power supply apparatus. It should be noted that this embodiment will be described with reference to FIGS. In this embodiment, the switching device 1 is provided between the electrode 5 and the power supply brush 8 and the power supply device 9 in that the carbon electrode 5 in the first embodiment is replaced with a copper (Cu) electrode 5.
The difference is that it is configured by providing 0, and other configurations are composed of the same constituent parts, and the same constituent parts are designated by the same reference numerals and the description thereof is omitted. Changeover switch 1 of changeover device 10
0a is for switching the electrode 5 and the pole of the power feeding brush 8 between plus and minus.

Using the apparatus having the above structure, in this embodiment, the diameter is φ20, the radius of curvature is 35 mm, and the material is LaSFO16.
The lens was spherically processed. The lens 1 is loaded on the chuck 2. Next, the coolant 7 is supplied and the electroconductive grinding wheel 4 is rotated at 14,000 rpm, and at the same time, the voltage adjustment button 30 of the power supply device 9 is set to 140V so that
The pulse changeover switch 31 is set to pulse. Furthermore, the changeover switch 10a of the changeover device 10 sets the electrode 5 to the negative pole and the feed brush 8 to the positive pole, and sets a DC pulse voltage of 140 V to the peak current 10A for the electrode 5 and the conductive grinding wheel 4. Then, electrode 5
Electric discharge occurs between the iron-based bond 21 of the conductive grinding wheel 4 and the iron-based bond 21 is removed.

By positively removing the iron-based bond, the protrusion amount l of the diamond abrasive grains 20 is 0.025 mm.
The above is maintained (see FIG. 1). The chuck 2 loaded with the lens 1 is rotated at 400 rpm, and the conductive grinding wheel 4 is cut into the processed surface of the lens 1. Cutting is performed in this state up to 0.4 mm out of the total cutting depth of 0.6 mm, and rough grinding is performed.

Next, the voltage adjustment button 30 of the power supply device 9
Is set to 60V and the steady / pulse changeover switch 31 is set to steady, and the changeover switch 10a of the changeover device 10 changes the electrode 5 from the negative pole to the positive pole to supply the power to the brush 8.
Switch from the positive pole to the negative pole. Then, electrode 5
Copper is ionized and moves toward the conductive grinding wheel 4.
The ionized copper Cu ²⁺ receives electrons from the conductive grinding wheel 4 and becomes copper and adheres to the ground surface 4a of the conductive grinding wheel 4 to form a copper coating 23 (see FIG. 4).

By forming the copper coating 23, the protrusion amount l'of the diamond abrasive grains 20 is kept at 0.01 mm or less. The remaining 0.2 mm of the total depth of cut is cut in this state for finish grinding. After finishing the cut, spark out for 5 seconds. After that, the conductive grinding wheel 4 is returned to its original position, and at the same time, the rotation of the chuck 2 and the conductive grinding wheel 4 is stopped, the supply of the coolant 7 is stopped, and the lens 1 is removed from the chuck 2. Due to the above, the grinding process, which was conventionally performed using two types of grindstones, is 3μ
It was possible to process to a surface roughness of mRmax.

According to this embodiment, the same effects as those of the first embodiment can be obtained, and the thickness of the film can be made uniform, and the film thickness can be easily controlled.

[0026]

As described above, according to the lens grinding method of the present invention, rough grinding and finish grinding can be performed with one grindstone, and the lens can be efficiently processed.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing the present invention.

FIG. 2 is a conceptual diagram showing the present invention.

FIG. 3 is a conceptual diagram showing the present invention.

FIG. 4 is a conceptual diagram showing the present invention.

FIG. 5 is a schematic configuration diagram showing a first embodiment.

FIG. 6 is a schematic circuit diagram showing a first embodiment.

FIG. 7 is a schematic configuration diagram showing a second embodiment.

FIG. 8 is a schematic circuit diagram showing a second embodiment.

FIG. 9 is a schematic configuration diagram showing a conventional example.

10 is a view on arrow A in FIG. 9. FIG.

[Explanation of symbols]

 1 Lens 2 Chuck 3 Work Axis 4 Conductive Grinding Wheel 5 Electrode 6 Nozzle 7 Coolant 8 Brush 9 Power Supply Device 10 Switching Device 30 Voltage Adjustment Button 31 Steady / Pulse Switching Switch

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location B24D 3/34 A

Claims (1)

[Claims] 1. A positive DC pulse is applied to the conductive grinding wheel and a negative DC pulse is applied to the electrode in the first half of the process when an electrode is provided so as to face the working surface of the conductive grinding wheel, and spherical generation grinding is performed by the curve generator method. Machining while applying voltage, and in the latter half of the machining, apply positive to the conductive grinding wheel and apply negative DC steady voltage to the electrodes, or apply negative to the conductive grinding wheel and apply positive DC steady voltage to the electrodes. The lens grinding method is characterized in that the processing is performed while finishing the processing by performing spark out at the end.