JP3077994B2 - Electrolytic dressing grinding equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a processing method and a processing apparatus used in grinding in the field of mechanical processing, and in particular, a displacement table for realizing a mirror surface property and a precise property. And a method and apparatus for creating a mirror surface shape using electrolytic dressing grinding.

2. Description of the Related Art Conventionally, processing of an ultra-precision functional component having precise mirror surface properties and shape accuracy, such as an optical lens and a mirror, requires an extremely complicated and many processing steps. In the processing step, first, a rough product shape is given by grinding, and then polishing using free abrasive grains such as lapping or polishing is performed. Such a processing method is very primitive, and it is difficult to automate as well as to improve the productivity. Therefore, the ratio of relying on human means is still small.

The present inventors have developed a high-precision metal bond ultra-fine grain grinding wheel (CIFB
-D grinding wheel) by applying an in-process dressing action by weak electrolysis, developed a highly stable and highly efficient mirror surface grinding method.
No. 5 proposed. This electrolytic in-process dressing grinding method makes it possible to apply particularly the mirror grinding of hard and brittle materials in all steps. For example, development of a comprehensive processing system such as an optical lens and a radiation mirror is desired.

On the other hand, during processing, the workpiece is vibrated and driven by a solid actuator such as a laminated piezoelectric element,
Japanese Patent Application No. 62-155340 proposes a work-piece vibrating apparatus for abrasive grain processing aiming at high working efficiency by the impact breaking action of the work. In this apparatus, a combined effect with a high-strength metal bond superabrasive grindstone is expected.

Furthermore, while utilizing the advantages of the above-described electrolytic in-process dressing grinding method, such as the homework of grinding performance, high grinding ratio, and high accuracy, the processing principles and apparatuses were integrated with the aim of higher removal efficiency. An electrolytic dress vibration grinding method and apparatus have been proposed in Japanese Patent Application No. 1-51327.

(Problems to be Solved by the Invention) As described above, the conventional low-coupling grindstone grinding and lapping methods are used to grind an optical lens, a synchrotron radiation mirror or a pure plane made of a hard and brittle material, which is the object of the present invention. However, using a processing method by polishing requires a long processing time, and the accuracy is not stable because of human means.
There were various problems such as low productivity. Further, no method has been developed yet that enables a precise mirror surface property and shape accuracy by using a processing method such as the electrolytic in-process dressing grinding and the electrolytic dress vibration grinding. In particular, since lenses and mirrors have a parabolic surface, a spherical surface, and an aspherical surface in shape, it has been extremely difficult to achieve such surface accuracy in grinding.

The present invention is based on the basic technology such as electrolytic in-process dressing grinding and electrolytic dress vibration grinding developed by the present inventors, and does not simply perform vibration crushing, but uses a displacement table for precise positioning and a mirror surface grinding method. It is an object of the present invention to provide an ultra-precision mirror surface shape creation grinding method and apparatus which enables precise mirror surface properties and high shape accuracy by realizing quality control, short delivery time, and automation.

(Means for Solving the Problems) The above-described problems are solved by a conductive grindstone that is driven to rotate, a grinding fluid supplied so as to contact the grindstone surface of the conductive grindstone with the conductive grindstone being an anode side, and a cathode. As a side, a power supply means for applying a voltage between the anode and the cathode, and an upper plate for fixedly holding the workpiece, and the workpiece facing the grinding wheel surface A displacement table having an actuator for displacing the upper plate so as to be slightly displaced or inclined by a small angle, a drive signal supply means for supplying a displacement drive signal to each of the actuators, and a displacement for each of the actuators And a sensor for detecting a processing load, and a displacement drive signal output by the drive signal supply means are controlled in accordance with a detection signal output by the sensor, so that a desired amount of displacement and inclination of the workpiece can be accurately determined. And a parallel processing control device for appropriately correcting the displacement amount and the tilt amount of the displacement table, and an electrolytic dressing grinding device for grinding a mirror-like curved surface on the workpiece. Can be achieved.

(Operation) Hereinafter, the present invention will be described in more detail.

The CIFB-D grindstone is obtained by mixing and sintering diamond abrasive grains with a cast iron fiber base material, and the abrasive grains are held by the strong bonding force of the cast iron fibers. In electrolytic dressing grinding, a weak current is supplied via the grinding fluid between the CIFB-D grinding wheel and the electrode, dressing is performed in-process, and the hard and brittle material is easily removed by the protrusion of the abrasive grains by an action similar to cutting. It is to be processed. Therefore, the fine abrasive CIFB-
By controlling and applying a weak current to the D grindstone, reliable projection of the abrasive grains is maintained, and a mirror surface with extremely high precision surface properties can be obtained.

Further, the shape processing of the spherical surface and the aspherical surface as the object of the present invention is performed by accurate positional control of the displacement table. FIGS. 7 (A) to 7 (D) show shapes of spherical and aspherical surfaces. 6A and 6B show an arrangement of three actuators for controlling the processing state and the position of the displacement table. Further, FIGS. 5A and 5B are schematic views showing the transition process of the posture of the displacement table.

First, the position control of each actuator at the time of processing the concave shape in FIG. 7A will be described in the transition process of FIG. 5A. The relationship between the respective displacements applied from the process a in which the grinding wheel surface starts to contact the work surface to the process g in which the grinding wheel surface comes into contact with and finishes the predetermined shape processing is illustrated. In the case of this processing, the displacements of the actuators 62 and 63 in FIG. 6A are always the same. In the process a before the start of the machining, the total actuator displacement is 0, but the actuator 61 is moved together with the contact start process b of the grinding wheel.
Displace greatly with respect to 62 and 63. In step c, the displacement of the actuator 61 is reduced, and in the intermediate step d, the total displacement is made equal. Thereafter, the actuators are sequentially performed in steps e and f.
The displacements of 62 and 63 are made larger than 61, and the total displacement is set to 0 again in the final process g.

On the other hand, in the case of the convex shape shown in FIG. 7 (B), the control of the displacement of the actuators 61, 62 and 63 is completely opposite to that in the case of the above-described control of the concave shape. Since the shape is related to the AA cross section, the displacement of the actuators 62 and 63 is controlled in the same manner as in the respective steps shown in FIG. 5A.

Further, FIGS. 7 (C) and 7 (D) show the case of shape processing having a curved shape in a cross section in two directions. In FIG. 10C, the control for the same AA section as in the case of FIG. 10A and the control process for the BB section orthogonal to this section (No. 5B)
(See the figure). Each control can be performed at the same time by coping with displacement software. However, the convex / concave surface in one direction and the convex surface in two directions can be processed by a cup grindstone, but the use of a straight grindstone as shown in FIG. 6B is premised on the concave surface in two directions. However, the same control direction can be applied to the concave surface with respect to the AA cross section shown in FIG. 5A. The composite shape of the above-mentioned processing shapes can of course be achieved by a combination of the respective control methods.

Although the control method of the displacement table described above is described using an example in which three actuators are used, by setting the number of actuators to four or more, it is possible to allocate position control evenly in the number of drive lines. Become. In addition, data is accumulated in the storage device of the CPU of the control system by the processing and execution, and it is possible to establish an appropriate displacement table control method and control conditions.

(Effects of the Invention) The present invention employs electrolytic dressing grinding by setting the displacement table of the present invention on a general surface grinder or the like, thereby enabling accurate fine positioning control of the displacement table and the use of fine abrasive tips. Since the grinding is combined, many effects can be obtained. For example, vibrations unique to processing machines,
It can be avoided from a critical problem such as low dynamic rigidity in precision grinding, and can be avoided by applying a variable rigidity control program of the displacement table even if a load is applied during machining. As a result, it has become possible to realize high-precision plane and planar texture processing on a general low-precision processing machine.

Further, according to the present invention, it is possible to create a spherical surface and an aspherical surface of a lens, a mirror or the like with a highly accurate surface property and a precise shape. That is, it has become possible to create a spherical surface, an aspherical surface, or a pure plane of a hard and brittle material such as glass, silicon, and silicon carbide, which has been extremely difficult in the past. Therefore, it is possible to impart a desired shape to a special functional component, for example, a radiation mirror or the like, to which such a material is imposed, and to produce the surface properties such as surface roughness and flatness with high precision. . Furthermore, according to the present invention, the conventional manufacturing process has been renewed,
It is possible to shift to an unmanned processing step and provide a high-quality and high-performance product.

(Example) Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a configuration diagram of an entire apparatus for carrying out the present invention. The conductive grindstone 5 to which the shape and the protrusion of the abrasive grains are precisely given by the electrolytic dressing is set on the rotating shaft of the grinding machine and driven to rotate. In the electrolytic in-process dressing grinding, the power supply 2 for setting the grindstone 5 to the potential of the (+) pole and the (−) electrode 3 placed close to the grindstone surface are used.
, And is started by the electric power supplied from the power supply device 1 via At this time, the conductive grinding liquid is supplied between the conductive grinding wheel surface and the (−) electrode by the coolant nozzle 4. By these means, the projection of the abrasive grains is always maintained during the processing on the conductive grinding wheel surface, so that it is possible to cope with the impartation of the mirror surface property by the fine abrasive grains and the precise shape processing.

On the other hand, in the same figure, in parallel with the electrolytic in-process dressing grinding, the position of the workpiece 17 is controlled by driving a displacement table (shown in detail in FIG. 2) 13 installed on the grinding machine 12. Is precisely controlled. At this time, the displacement table is provided with a drive signal supply means 14 for supplying the displacement drive signal and a measurement signal relay means for relaying a signal from a detection means incorporated in the displacement table for measuring an actual displacement / load during machining. By 15 parallel processing controllers 16,
The displacement drive / control is performed very precisely.

FIG. 2 is a plan sectional view showing the structure of the displacement table 13 in FIG. This displacement table holds the workpiece
An upper plate 18 for positioning and a base 19 for holding the entire table on a grinding machine can be roughly classified. An actuator 20, which is a driving means for realizing a predetermined displacement and positioning of the upper plate from the base, is disposed between them. A lower end of the actuator is fixed to the upper surface of the base, and a transmission plate piece 21 that is in contact with the upper plate and transmits the displacement of the actuator to the upper plate is fixed to the upper end of the actuator. This transmission plate piece has a curved three-dimensional shape at the center thereof so that different displacements of three actuators can be reliably transmitted to the upper plate 18 for precise positioning. At the same time, to achieve precise positioning,
The preload strut 22 obtains the relaxing force of the preload spring 23 so that the upper portion of the transmission plate piece 21 and the upper plate 18 always contact at a predetermined pressure.
A mechanism is provided for bringing the actuator 20 into close contact with the upper plate 18 and the base 19 at a predetermined preload. O-rings 24 and 25 for preventing a machining liquid (coolant) required for actual machining from entering the inside of the displacement table are arranged on the outer peripheral portion of the upper plate 18 and the outer peripheral portion of the base portion 19. Sealed by the inner surfaces of the casing 26 and the base casing 27. At this time, a thin plate 28 is sandwiched between the lower surface of the upper plate casing 26 and the upper surface of the base unit casing 27, and by fixing bolts 29, 30, 31 for each part,
Thin plate 28 and upper plate 18, upper plate part casing 26 and thin plate 28, thin plate 28
The base casing 27 and the base casing 27 and the base 19 are securely fixed and held. Therefore, the thin plate 28
Then, even if a shearing force (force pressing the upper plate in the horizontal direction) is applied during processing between the upper plate 18 and the base 19,
Sufficient lateral stiffness is achieved. Furthermore, upper plate 18 and base
A sensor 32 for detecting the actual displacement with respect to 19 or the load existing between them is arranged at the bottom of the base 19 by a holding / fixing tool 34. Sensor is a ring actuator
Detection rod 33 that penetrates through the center of 20 and extends from the lower surface of transmission plate piece 21
The displacement is detected by facing or contacting with the actuator, and a signal is input to the actuator from an external control system to drive the upper plate 18.
Further, a base bottom casing 35 and a base bottom seal thin plate 36 for preventing intrusion of a machining fluid are fixed to the bottom of the base 19. Cables for transmitting drive signals and detection signals of a plurality of actuators and sensors communicate with the outside of the displacement table through holes provided in a base bottom casing or the like. During actual machining, the upper plate of the displacement table
18 Specimen plate for fixing and holding the workpiece fixed to the upper surface 37
Is attached. Further, the displacement table base portion 19 is provided with a fixing / holding means for facilitating mounting on the processing machine.

FIG. 3 is a block diagram of a control system of the displacement table. The control of the displacement table 13 shown in FIG. 2 is performed as follows. Sensor that detects the amount of drive of the displacement table
A signal 39 from 32 is transmitted through an amplifier 42 that amplifies to a predetermined amplitude to a synchroscope 43 connected for the purpose of displaying a part of the signal to a system operator, and one is an A / D converter. Introduced in 44. Via the A / D converter 44, the detection signal is input to the CPU 45, which is the heart of the control system. The signal calculated by the CPU enters the D / A converter 46, is output to the drive circuit 40 of the actuator 20, and is driven by the DC power supply 41 that supplies power to the actuator. In addition to the two input / output signals, the CPU 45 is connected to a display 47 for displaying a drive / control state of the system to a system operator, and a printer 48 for hard-copying the drive / control results. I have. CPU
As the signal processing in the above, it is responsible for the command processing for supplying the drive signal calculated on the initial software to the actuator of the displacement table via the D / A converter, while the input signal is input from the A / D converter. A feedback function is also provided for determining whether or not the initial displacement table drive signal is appropriate by referring to the detected signal, and for in-process correcting / correcting the drive signal. This CPU alone has the applicability of controlling the grinding machine in addition to the control function of the displacement table by the control system alone.

Hereinafter, an experimental example will be described in which a synchrotron radiation mirror (concave mirror) is assumed using silicon carbide as a hard and brittle material and processed with a sample having a diameter of 30 mm and a length of 51 mm. Table 1 shows the specifications of the grinding machine and equipment shown in FIG.

First, truing of the CIFB-D grinding wheel was performed using a # 100C grinding wheel or the like, and initial dressing was performed by electrolytic dressing. Electrolytic dressing grinding process is rough finish, medium finish,
This was performed in three stages of the final finish, and the displacement table was used only in the final finish. The grinding conditions at this time are a grinding wheel peripheral speed of 1200 m / min and a feed speed of 100 mm / min. next,
The silicon carbide of the workpiece is bonded and fixed on a displacement table set on a grinding machine, and coarse-grain CIFB-D straight grinding wheel #
A round bar having a diameter of 30 mm and a length of 51 mm was processed into a square bar by using 600.
The cut depth is 15 μm. Subsequently, it was replaced with a CIFB-D grindstone # 1200 that had been truing and dressing in advance, and the finished surface formed on the surface of the workpiece in the rough finish was medium-finished to the extent that gloss was obtained. Cut depth 15μm
It is. In this state, the initial processing flatness was about 0.5 μm. The final finish was performed by Elid mirror surface grinding using a fine-grain CIFB-D grinding wheel # 4000 in two stages of a cut amount of 2 μm and 1 μm. The Elid condition at this time is as follows: applied voltage 90 V, peak current 2
4A, pulse frequency on12 μs, off3 μs. The curvature of the concave mirror is R60m. The displacement table was designated and controlled with a maximum displacement of 6.5 μm within a processing distance of 51 mm per bus. This is an extremely precise control of the R processing in which the displacement is monotonically increased from the machining start point, is maximized at the center of the workpiece, and is monotonously decreased again. as a result,
As shown in Fig. 4, the processing surface shape is 6.5μ at the maximum displacement.
m recesses were created. Table 2 shows the specifications of the displacement table, and Table 3 shows the specifications of the displacement table control system.
Note that the actuator on the displacement table
A displacement of 6.5 μm is obtained.

In FIG. 4, the measured surface roughness was _Ra = 6.
88 nm and R _max = 40-50 nm were obtained, and it was found that the surface exhibited a surface close to plastic flow due to the tip of fine abrasive grains essential for Elid grinding.

In this embodiment, Elid grinding using a # 4000CIFB-D grindstone was applied to a normal processing machine, a predetermined control was performed on the displacement table, and it was possible to realize creation of a highly accurate surface property and a precise shape.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing the configuration of an apparatus according to the present invention, FIG. 2 is a cross-sectional view showing the configuration of the displacement table of FIG. 1, and FIG. 3 is a block diagram of a control system for the displacement table. FIG. 4 is a diagram showing an example of a precision-shaped workpiece that has been ground in the present embodiment. FIGS. 5A and 5B are diagrams schematically showing a transition process of the posture of the displacement table. 6A and 6B are diagrams showing an arrangement of three actuators for controlling a machining state and a position of a displacement table, and FIG. 7 is a diagram showing an example of a machining shape of a workpiece. It is. (Explanation of symbols) 1... Power source 2... Power supply 3... Negative electrode 4. 4 ″... Coolant nozzle 5... Grindstone 12... Grinding machine 13. ... drive signal supply means, 15 ... measurement signal supply means, 16 ... parallel processing control device, 17 stores ... workpiece, 18 ... top plate, 19 ... base, 21 ... transmission plate piece, 20 , 61, 62, 63 ... Actuator, 22 ... Preload support, 23 ... Spring, 24, 25 ... O-ring, 26, 27, 35 ... Casing, 28, 36 ... Thin plate, 29, 30, 31 …… Fixing bolt, 32 …… Sensor, 33 …… Detector rod, 34 …… Fixer, 37 …… Sample plate, 39 …… Sensor signal, 40 …… Drive circuit, 41 …… DC power supply, 42 …… Amplifier, 43… Synchroscope, 44… A / D converter, 45… CPU, 46… D / A converter, 47… Display, 48… Printer.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FI B24B 53/00 B24B 53/00 D (72) Inventor Zhao Zhong 2-1, Hirosawa, Wako-shi, Saitama Pref. RIKEN (56) References JP-A-2-53557 (JP, A) JP-A-1-188266 (JP, A) JP-A-1-138563 (JP, U) JP-A-63-67070 (JP, U) JP-A-63 −74269 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B24B 13/00 B23H 5/00 B23H 5/06 B23Q 1/30 B24B 41/06 B24B 53/00

Claims (4)

(57) [Claims] 1. An anode and a cathode, wherein a conductive grindstone which is rotationally driven and a grinding fluid supplied so as to contact the grindstone surface of the conductive grindstone are used as a cathode side with the conductive grindstone as an anode side. A power supply means for applying a voltage therebetween, and an upper plate for fixedly holding the workpiece, and slightly displacing the workpiece toward the grindstone surface or inclining by a small angle A displacement table having an actuator for displacing the upper plate such that the upper plate is displaced, a drive signal supply means for supplying a displacement drive signal to each of the actuators, and a sensor for detecting the displacement and the processing load of each of the actuators And, controlling the displacement drive signal output by the drive signal supply means according to the detection signal output by the sensor,
A parallel processing control device for appropriately correcting the displacement amount and the inclination amount of the displacement table so that the desired amount of the displacement and the inclination can be accurately given to the workpiece; and a mirror-like curved surface on the workpiece. Dressing grinding equipment for grinding of steel. 2. The device according to claim 1, wherein the sensor is arranged on a central axis in the operation direction of the actuator. 3. The apparatus according to claim 1, wherein at least three actuators are arranged along a surface of the upper plate. 4. The apparatus according to claim 1, wherein said actuator is a laminated piezoelectric element.