JP3169631B2 - Method and apparatus for electrolytic dressing with semiconductor contact electrode - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for dressing a grinding wheel used for grinding in the field of machining, and more particularly to electrolytic dressing of a conductive grinding wheel for dressing a conductive grinding wheel by an electrolytic effect. Method and apparatus.

[0002]

2. Description of the Related Art An electrolytic dressing method and apparatus for a conductive grindstone, which uses a conductive grindstone such as a cast iron fiber bond diamond grindstone, applies a voltage to the grindstone and dresses the grindstone by electrolysis, has been disclosed by the same applicant as the present applicant. JP
It is disclosed in Japanese Patent Application No. 1-188266 (Japanese Patent Application No. 63-12305) and succeeded in mirror-polishing semiconductor materials such as silicon as electronic materials. Further, an electrolysis in-process dressing grinding method (Electrolytic Inproc
A method and apparatus referred to as “ess dressing: Elid grinding method” have been developed and published by the applicant of the present invention (RIKEN Cymbodium, “Latest Technology Trend of Mirror Surface Grinding”, held on March 5, 1991).

[0003] The Elid grinding method comprises a grindstone having a contact surface with a workpiece, an electrode facing the contact surface, a nozzle for flowing a conductive liquid between the grindstone and the electrode, and a voltage between the grindstone and the electrode. Is a device comprising a power source and a power supply for applying the voltage, applying a voltage between the grindstone and the electrode while flowing a conductive liquid between the grindstone and the electrode, and dressing the grindstone by electrolysis.

FIG. 8 shows a dressing mechanism by the Elid grinding method. At the beginning of sharpening of the grinding wheel (A), the electric resistance between the grinding wheel and the electrode is small and a relatively large current (5
-10A) flows. As a result, the metal part (bond) on the surface of the grindstone is dissolved by the electrolytic effect, and the non-conductive diamond abrasive grains protrude. In addition, when energization is continued, iron oxide (F
An insulating film mainly composed of e ₂ O ₃ ) is formed on the grindstone surface, and the electric resistance of the grindstone increases. This reduces the current,
Dissolution of the bond is reduced, and the protrusion of the abrasive grains (sharpening of the grinding stone) is substantially completed (B). When grinding is started in this state (C), the diamond abrasive grains are worn as the workpiece is ground, while the coating liberates grinding debris. When grinding is further continued (D), the insulating coating on the surface of the grindstone is removed by abrasion, the electric resistance of the grindstone decreases, the current between the grindstone and the electrode increases, the dissolution of the bond increases, and the protrusion of the abrasive grains (grindstone) ) Is resumed. Therefore, during the grinding by the Elid grinding method, the overelution of the bond is suppressed by forming and removing the coating as shown in (B) to (D), and the protrusion of the abrasive grains (grinding of the grindstone) is automatically adjusted. You. The above-described cycle shown in (B) to (D) is hereinafter referred to as an Elid cycle.

[0005]

The above-mentioned Elid grinding method is capable of stably obtaining good mirror surface roughness.
Although satisfactory, there were the following problems. (1) Before entering the Elid cycle of FIG. 8, in (A), the formed insulating film is thicker than the film thickness required in use, and therefore, before the actual mirror finishing, the optimum film thickness is obtained. Unnecessary grinding had to be performed until it became. (2) The dressing speed during the Elid cycle changes depending on the thickness of the insulating coating. That is, sparks are generated between the thin portion of the insulating film and the electrode, and the dressing may proceed locally. (3) In order to realize an optimal Elid cycle, it is essential that the electrolysis of the bond is suppressed by an insulating coating at a certain point in time. In relation to the above (1) and (2), the pulse or the pulse and the direct current It required mixed and complex power supplies.

Accordingly, it is an object of the present invention to provide an electrolytic dressing method and apparatus in which an insulating film is formed thinly and uniformly so that a DC power supply can be applied.

[0007]

According to the present invention, there is provided, in accordance with the present invention, a conductive liquid between a conductive grindstone having a contact surface with a workpiece and an electrode opposed to the contact surface. Flowing, applying a voltage between the whetstone and the electrode, in an electrolytic dressing method of dressing the whetstone by electrolysis, the conductive whetstone, characterized in that an electrode made of a semiconductor material is brought into contact with the contact surface of the whetstone An electrolytic dressing method is provided.

Further, according to the present invention, a conductive grindstone having a contact surface with a workpiece, an electrode facing the contact surface, a means for flowing a conductive liquid between the grindstone and the electrode, Means for applying a voltage between the whetstone and the electrode,
In an electrolytic dressing apparatus for dressing a grindstone by electrolysis, there is provided an electrolytic dressing apparatus for a conductive grindstone, wherein the electrode is made of a semiconductor material and is in contact with the contact surface of the grindstone.

[0009]

According to the method and apparatus of the present invention described above, since the electrode is made of a semiconductor material and is in contact with the contact surface of the grindstone, the difference in electrical resistance between the thin and thick portions of the insulating film is small. , Spark is less likely to occur. Therefore, the change in dressing speed due to the difference in the thickness of the insulating film is small.

Further, since the spark is small and the electrode is in contact with the contact surface of the grindstone, the insulating film formed in FIG. 8A before entering the Elid cycle becomes relatively thin. For this reason, before the actual mirror polishing is performed, the amount of grinding performed until the film thickness becomes optimum is reduced. Furthermore, since the change in dressing speed is small and the formed insulating coating is thin and uniform, a complete DC power supply can be applied.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram schematically showing an electrolytic dressing apparatus according to the present invention. In this figure, 10
Is a substantially disk-shaped conductive grindstone having a vertical axis, and the grindstone 10 is horizontally rotatably fixed to an upper head of a processing machine (not shown). This upper head
It can be moved in the horizontal and vertical directions together with the grindstone 10.

Below the upper head, a table 14 of a processing machine is provided horizontally. The table 14 is usually completely fixed, but may be movable horizontally and / or vertically. Table 14
A workpiece, that is, a work 16 is fixed to the upper surface of the workpiece in a generally known manner. The lower surface of the grindstone 10, that is, the work 16
The contact surface 12 is a horizontal cutting surface, and the upper surface of the work 16 is cut by bringing the contact surface 12 of the rotating grindstone 10 into contact with the upper surface of the work 16.

A horizontal plate-like electrode 20 made of a semiconductor material, for example, silicon, is urged under the portion of the grinding wheel 10 not in contact with the work 16 so as to evenly contact the contact surface 12 of the grinding wheel 10. It is provided. A plurality of nozzles 30 are provided around the grindstone 10, so that a weakly conductive cutting fluid, that is, a coolant, flows between the grindstone 10 and the electrode 20 via a supply pipe (not shown). The nozzle 30 is preferably provided so that coolant flows between the grindstone 10 and the work 16.

Further, the apparatus is provided with a power supply 40,
A positive voltage is applied to the grindstone 10 via a power supply 42 that comes into contact with the circumferential surface of the grindstone 10, while a negative voltage is applied to the electrode 20.
Can be applied. This power supply 40
Is preferably a DC constant voltage power supply, but may be a conventional pulse power supply or a power supply in which pulse and DC are mixed.
FIG. 2 is a diagram showing the electrode 20 and the power supply 42 used in the present invention in more detail.

In FIG. 1, an electrode 20 is formed by bonding silicon 24 as a semiconductor to both surfaces of a metal plate 22 having good conductivity, and a negative voltage is applied to the metal plate 22 from a power supply 40. The electrode 20 is horizontally fixed to one end of a substantially horizontal leaf spring 26, and the other end of the leaf spring 26 is fixed to an insulator 28.
It is fixed to the upper head 18 of the processing machine by known means. With this configuration, the electrode 20 is always urged upward by the elastic force of the leaf spring 26.

The power supply 42 is also fixed to the upper head 18 of the processing machine by known means while being urged against the outer peripheral surface of the grindstone 10 in a known manner. Although the configuration of the present invention has been described for a so-called cup grindstone, the present invention can also be applied to a straight grindstone and other grindstones. Next, a method of using the device according to the present invention will be described.

First, a conductive liquid, that is, a coolant, flows between the conductive grindstone 10 and the electrode 30. Next, a voltage is applied between the grindstone 10 and the electrode 20, and in this state, the grindstone 10 is brought into contact with the work 16 to perform cutting. The mechanism of dressing of the grinding wheel during cutting is basically the same as the conventional one.
As shown in FIGS. 8B to 8D, overelution of the bond is suppressed by forming and removing the film, and the protrusion of the abrasive grains (grinding of the grindstone) is automatically adjusted.

Example 1 Specular grinding was performed by an apparatus according to the present invention using a grinding machine, a grindstone, a power supply, a work material and the like shown in Table 1. The results are shown in FIGS. In the figure, (A) shows the conventional Eli
d shows the result of the grinding method, and (B) shows the result of the present invention.

[0019]

[Table 1]

(1) Dressing characteristics As in the case of the conventional apparatus, the decrease in the actual current with the energization time was recorded (FIG. 3, circle). When the current decreased to about 1 A, the state of the grindstone surface was such that a nonconductive film, that is, an insulating film was formed despite contact of the electrodes. (2) Mirror surface grinding characteristics Fig. 4 shows how the grinding resistance varies. As in the past, the grinding resistance tended to increase and stabilize with the mirror finishing of the processing surface, but showed a slightly higher load than in the past. It is thought that the abrasive pressure of the abrasive grains slightly occurred due to the contact pressure of the electrodes. (3) Roughness of Processed Surface FIG. 5 shows the roughness pattern of the nitrogen-silicon finished surface. As is clear from the figure, a mirror surface similar to the conventional one was obtained. (4) Application of DC power supply The results of investigation of the initial dressing characteristics with the DC power supply are shown in FIG. It can be seen from the current reduction behavior that a sufficiently thin non-conductive film was formed. (5) Mirror grinding characteristics by DC power supply In conventional electrolytic dressing using a normal DC power supply,
Although the film thickness at the time of dressing was too large and it was difficult to quickly remove the film, in the apparatus of the present invention, even if a DC power supply was used as shown in FIG.
Was obtained. Further, the cutting resistance when a DC power supply was used was slightly higher than that of the conventional one as shown in FIG.

[0021]

As described above, according to the method and apparatus of the present invention, since the electrode is made of a semiconductor material and is in contact with the contact surface of the grindstone, the electric connection between the thin and thick portions of the insulating coating is obtained. The difference in resistance is small, and sparks are unlikely to occur. Therefore, the change in dressing speed due to the difference in the thickness of the insulating film is small.

Further, since there is little spark and the electrode is in contact with the contact surface of the grindstone, the insulating film formed in FIG. 8A before entering the Elid cycle becomes relatively thin. For this reason, before the actual mirror polishing is performed, the amount of grinding performed until the film thickness becomes optimum is reduced. Further, since the change in dressing speed is small and the formed insulating film is thin and uniform, a great effect such as a complete DC power supply can be obtained.

[Brief description of the drawings]

FIG. 1 is a view schematically showing an electrolytic dressing apparatus according to the present invention.

FIG. 2 is a diagram showing an electrode and a power supply body in further detail.

FIG. 3 is a diagram showing behavior and characteristics by contact electrolytic dressing.

FIG. 4 is a diagram showing a grinding resistance when a pulse power supply is used.

FIG. 5 is a diagram showing surface roughness after Elid grinding.

FIG. 6 is a view showing surface roughness after Elid grinding using a DC power supply.

FIG. 7 is a diagram showing a grinding resistance when a DC power supply is used.

FIG. 8 is an explanatory diagram showing an Elid cycle in the Elid grinding method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Grinding stone 12 Contact surface 14 Table 16 Workpiece 18 Upper head 20 Electrode 22 Metal plate 24 Silicon 26 Leaf spring 28 Insulator 30 Nozzle 40 Power supply 42 Feeder

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B24B 53/00 B23H 5/00 B23H 5/10

Claims (2)

(57) [Claims] A conductive liquid is caused to flow between a conductive grindstone having a contact surface with a workpiece and an electrode facing the contact surface,
An electrolytic dressing method for applying a voltage between the whetstone and an electrode to dress the whetstone by electrolysis, comprising: bringing an electrode made of a semiconductor material into contact with the contact surface of the whetstone. . 2. An electroconductive grindstone having a contact surface with a workpiece, an electrode facing the contact surface, means for flowing a conductive liquid between the grindstone and the electrode, and A means for applying a voltage therebetween, in an electrolytic dressing apparatus for dressing the grindstone by electrolysis, wherein the electrode is made of a semiconductor material, and the conductive grindstone characterized in that it is in contact with the contact surface of the grindstone Electrolytic dressing equipment.