JP3250931B2 - Grinding method and apparatus using magnetic field - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grinding method and apparatus using a magnetic field.

[0002]

2. Description of the Related Art The present invention relates to a method and an apparatus for electrolytically dressing a conductive whetstone using a metal bond whetstone, for example, a conductive whetstone such as a cast iron fiber bond diamond whetstone, and applying a voltage to this whetstone to dress the whetstone by electrolysis. JP-A-1-188266 (Japanese Patent Application No. 63-12305) by the same applicant
And succeeded in mirror-polishing a semiconductor material such as silicon as an electronic material. Further, a method and apparatus called Electrolytic In-process Dressing (hereinafter referred to as ELID grinding method), which has developed this method and apparatus, have been developed and published by the applicant of the present invention (RIKEN Symposium `` Latest Technology Trends in Mirror Grinding ”, March 5, 1991).

[0003] This ELID grinding method comprises a grinding wheel having a contact surface with a workpiece, an electrode facing the grinding stone at an interval, a nozzle for flowing a conductive liquid between the grinding wheel and the electrode, and a grinding wheel and an electrode. Using a device consisting of an application device (power supply and power supply) for applying a voltage between the electrodes, applying a voltage between the grindstone and the electrode while flowing a conductive liquid between the grindstone and the electrode, and electrolyzing the grindstone. Dressing.

FIG. 6 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 (non-conductive film) mainly composed of e ₂ O ₃ ) is formed on the grindstone surface, and the electric resistance of the grindstone increases. This allows
The current decreases, the dissolution of the bond decreases, and the protrusion of the abrasive grains (sharpening of the grindstone) is substantially completed (B). When the grinding is started in this state (C), the diamond abrasive grains are worn as the workpiece is ground while the coating releases grinding dust. When the grinding is further continued (D), the non-conductive film 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 ( Grinding) is resumed. Therefore, during the grinding by the ELID grinding method, as shown in (B) to (D), the overelution of the bond is suppressed by the formation and removal of the film, and the protrusion of the abrasive grains (grinding of the grindstone) is automatically adjusted. You. (B) ~
The cycle shown in (D) is hereinafter referred to as an ELID cycle.

[0005] In the above-mentioned ELID grinding method, even if the abrasive grains are made fine, clogging does not occur in the grindstone due to the sharpening of the grindstone by the ELID cycle. Can be obtained by Therefore, the ELID grinding method can maintain the sharpness of the grinding wheel from high-efficiency grinding to mirror grinding, and is expected to be applied to various grinding processes.

[0006]

However, the above-mentioned ELI
In D-grinding, the protrusion of the abrasive grains (grinding of the grindstone) itself is automatically adjusted, but the size of the protrusion amount cannot be controlled. That is, the protrusion amount of the abrasive grains is preferably about 1/3 of the particle diameter, for example, 50 μm.
In the case of the conventional ELID grinding method, the electrolytic current value is determined by the material of the grindstone and the power supply voltage, and thus the amount of protrusion of the abrasive particles is also determined by the conventional ELID grinding method. I was

Therefore, in order to change the protrusion amount of the abrasive grains (and the electrolytic current value directly affected by the abrasive grains), the whetstone must be replaced with another material, the power supply voltage must be changed, or the DC power of the pulse power supply must be changed. It was necessary to change the components. However, this method requires preparing and testing various grindstones of different materials, and there is a problem that it takes too much cost and labor to obtain a desired amount of protrusion of abrasive grains. In addition, when voltage or current is increased, arc or local electrolysis is likely to occur, uniform abrasive grains cannot be protruded, stable sharpness cannot be maintained, and an excellent machined surface cannot be obtained. In order to change the direct current component, there is a problem that an electric circuit becomes complicated and many tests need to be performed.

Further, in the conventional ELID grinding, the metal (iron, cobalt, etc.) constituting the grinding wheel adheres to the surface of the electrode (cathode) by electrolysis like a kind of plating, and the gap between the grinding wheel and the electrode changes. There was a problem that it could be buried in severe cases. Therefore, conventionally, for example, 8 to 1
After continuous use for about 0 hours, it is necessary to mechanically remove this, and there has been a problem that it takes time to change the dimensions of the electrode and readjust it.

The present invention has been made to solve such a problem. That is, an object of the present invention is to provide a grinding method and apparatus capable of controlling an electrolytic current and thereby controlling an amount of protrusion of abrasive grains. Another object of the present invention is to provide a grinding method and apparatus capable of reducing the amount of metal adhered to the electrode surface, thereby enabling continuous operation for a long time.

[0010]

According to the present invention, a conductive liquid is caused to flow between a conductive and magnetic whetstone and an electrode, and a current is applied between the whetstone and the electrode via the conductive liquid. A grinding method using a magnetic field is provided, wherein a magnetic field is formed in a direction in which the current flows and intersects with the current, and the workpiece is ground while dressing the grindstone by electrolysis. According to a preferred embodiment of the present invention, it is preferable to change the magnetic field during grinding.

Further, according to the present invention, a conductive and magnetic grindstone having a contact surface with a workpiece, a conductive and magnetic material electrode opposed to the grindstone at an interval, A nozzle for flowing a conductive liquid therebetween, a voltage application device for flowing a current through the conductive liquid therebetween, and a magnetic field device for forming a magnetic field in a direction intersecting the current therebetween,
Thus, there is provided a grinding apparatus using a magnetic field, which grinds a work while dressing a grindstone by electrolysis. According to a preferred embodiment of the present invention, the directions of the magnetic field and the current are substantially orthogonal. Further, the whetstone and the electrode are made of a ferromagnetic material. Further, at least a portion of the magnetic field device facing the grindstone and the electrode is made of an insulator.

[0012]

The conductive liquid contains cations (Na⁺, K⁺, Ca
⁺⁺, Etc.) and anions (OH ^-, Cl^-, SO_Four ^-,
Etc.), and these ions affect the grinding performance
It is known to Therefore, the inventor of the present application
Controlling electrolytic current by applying a magnetic field to these ions
We focused on the possibility of being able to do so. Also, this magnetic field
Direct force also acts on Fe ions etc. generated from the grinding wheel
This also controls the amount of abrasive protrusion.
Control and reduce metal adhesion to the electrode surface
We focused on that. The present invention is based on such a new idea.
The effect was confirmed by a test.

That is, according to the above-described method and apparatus of the present invention, a conductive liquid is caused to flow between a conductive and magnetic whetstone and an electrode, and the conductive liquid is applied between the whetstone and the electrode by a voltage applying device. And a magnetic field is formed by a magnetic field device in the direction intersecting the current, thereby grinding the work while dressing the grindstone by electrolysis, so that the grindstone, the conductive liquid between the electrodes and the grindstone A current and a magnetic field can be formed crossing the surface, and the cations and anions contained in the conductive liquid can be moved in opposite directions along the grinding wheel surface by the so-called Fleming's left-hand rule. Can be moved along the surface of the grindstone. Therefore, the distribution of ions in the conductive liquid changes due to the magnetic field, and thereby the electrolytic current can be changed. In addition, since the Fe ions and the like are positively moved along the surface of the grindstone, the protrusion amount of the abrasive grains can be promoted, and the adhesion of metal to the electrode surface can be reduced.

[0014]

Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing a first embodiment of a grinding apparatus 10 according to the present invention. In this figure, a grinding device 10 of the present invention includes a conductive and magnetic grinding wheel 12 having a contact surface with a workpiece 1, a conductive and magnetic material electrode 14 opposed to the grinding wheel 12 at an interval, and a grinding wheel. 12 and electrode 1
4, a nozzle 16 for flowing a conductive liquid, a voltage applying device 18 for flowing a current I through the conductive liquid therebetween, and a magnetic field device 2 for forming a magnetic field B in a direction intersecting the current I therebetween.
0.

In FIG. 1, a grindstone 12 is a cylindrical grindstone, and the workpiece 1 is ground on the outer peripheral surface. The grindstone 12 is a conductive grindstone and is made of abrasive grains (diamond or CBN) and a bonding material for fixing the same, and the bonding material includes a ferromagnetic metal such as Fe, Co, and Ni. Further, the electrode 14 is also conductive, and is composed of Fe, C
It is made of a ferromagnetic metal such as o or Ni. That is, the electrode 1
4 is changed from a non-magnetic material such as copper, copper alloy, carbon or the like to a ferromagnetic material such as Fe, Co, Ni or the like, thereby forming a magnetic field loop passing through the grindstone 12 and the electrode 14, thereby forming a magnetic field B To make it more powerful.

The conductive liquid is the same as that of the conventional ELID grinding.
Use of This conductive liquid contains cations (Na⁺,
K⁺, Ca⁺⁺, Etc.) and anions (OH^-, Cl^-,
SO _Four ^-, Etc.). The conductive liquid is applied to the nozzle 1
6 to the contact portion between the work 1 and the grindstone 12,
It is supplied between the electrode 14. The voltage applying device 18
A power supply 18a and a power supply 18b.
A positive voltage is applied to the electrode 14 and a negative voltage is applied to the electrode 14.
Swelling. DC power supply 18a is, for example, about 60 V
And a pulse for turning this voltage ON and OFF
It can be supplied by waves. The power supply 18b is a whetstone
12 is slidably in contact with the side surface. With this configuration
Between the outer surface of the grinding wheel 12 and the inner surface of the electrode 14.
Pressure, and a current I through the conductive liquid existing therebetween.
Can flow.

The magnetic field device 20 comprises a pair of N-pole and S-pole magnets 20a in FIG. This magnet is a permanent magnet in this figure, but may be an electromagnet. S pole magnet 2
0a is in front of the grindstone 12, and the N pole magnet 20a is
And a magnetic field B generated by these elements is formed in a direction crossing a current I between the grindstone 12 and the electrode 14. Further, at least a portion of the magnetic field device 20 facing the grindstone and the electrode is preferably made of an insulator, and is preferably made entirely of an insulator.
For example, in the case of a permanent magnet, it is preferable to use a non-conductive ferrite magnet as a whole, and in the case of an electromagnet, it is preferable to use a non-conductive material for its core and the like. With this configuration, the influence of the magnetic field device 20 on the electrodes (for example, an apparent increase in area) can be avoided, and the magnetic field device 20 is prevented from being consumed by the influence of the current I and metal ions or the like are attached. can do.

The apparatus described above is used as follows.
That is, a conductive liquid flows between the grindstone 12 and the electrode 14 from the nozzle 16, a current I flows between the grindstone 12 and the electrode 14 via the conductive liquid by the voltage applying device 18, and a magnetic field device A magnetic field B is formed in a direction intersecting the current I by 20. Thus, the workpiece is ground while dressing the grindstone by electrolysis. Between the grinding wheel 12 and the electrode 14, a current I flowing from the grinding wheel 12 to the electrode 14 and a magnetic field B directed from the N pole to the S pole by the magnetic field device 20 are formed to intersect with each other. And anions can be moved in the opposite direction along the grindstone surface, and at the same time, Fe ions and the like generated from the grindstone 12 can also be moved along the grindstone surface. In addition, particularly when high efficiency machining is required by changing the direction or strength of the magnetic field B during grinding, the protrusion amount of the abrasive grains is increased, and a high quality finished surface is required. In such a case, the protrusion amount of the abrasive grains can be reduced.

FIG. 2A is a partial front view of FIG.
FIG. 2B is a partial cross-sectional view taken along line XX.
As shown in FIG. 2B, between the grinding wheel 12 and the electrode 14, a current I flowing from the grinding wheel 12 to the electrode 14 and a magnetic field B from the N pole to the S pole by the magnetic field device 20 are substantially orthogonal. Is formed. Note that the current I and the magnetic field B do not necessarily need to be orthogonal to each other, but need only intersect at least. Further, in FIGS. 1 and 2, the S pole is arranged on the front side of the grindstone 12 and the N pole is arranged on the back side of the grindstone 12. However, the present invention is not limited to this configuration. The S-pole may be arranged later, or the N-pole and S-pole may be arranged in a direction sandwiching the electrode 14 up and down in FIG. 1, and the N-pole and S-pole are partially embedded in the electrode 14. It may be an arrangement.

FIG. 3 is a diagram showing the relationship between the current I, the magnetic field B, and the force f acting between the grindstone 12 and the electrode 14. FIG. 3A shows the S pole on the front side as shown in FIGS. (B) shows the case where the N pole is arranged before the N pole and the S pole is arranged after the N pole. The intersection angle between the current I and the magnetic field B is θ
Then, according to Fleming's left-hand rule, f = I
A force f of B sin θ acts in a direction orthogonal to both the current I and the magnetic field B. Therefore, cations and anions contained in the conductive liquid can be moved in the opposite direction along the grindstone surface, and at the same time, Fe ions and the like generated from the grindstone 12 can also be moved along the grindstone surface. As a result, the distribution of ions in the conductive liquid changes due to the magnetic field, thereby changing the electrolytic current. In addition, since the Fe ions and the like are positively moved along the grindstone surface, the protrusion of the abrasive grains The amount can be promoted and the adhesion of metal to the electrode surface can be reduced.

FIG. 4A shows a second embodiment of the grinding apparatus 10 according to the present invention, and FIG. 4B is a partial sectional view taken along the line YY. In this figure, the grindstone 12 is a cup-shaped grindstone, and the work 1 is ground on its lower surface. The magnetic field device 20 includes a pair of S-pole and N-pole magnets 20a arranged to face the lower surface of the grindstone 12. The facing direction of the magnet 12 may be a circumferential direction as shown in the figure, or may be a radial direction. Other configurations are the same as those of the first embodiment shown in FIGS. With this configuration, as shown in FIG. 4B, a current I flowing from the grindstone 12 to the electrode 14 and a magnetic field B from the N pole to the S pole by the magnetic field device 20 are applied between the grindstone 12 and the electrode 14. Crosswise, cations and anions contained in the conductive liquid can be moved in opposite directions along the grindstone surface as in the first embodiment, and at the same time, Fe ions and the like generated from the grindstone 12 can also be grindstones. It can be moved along the surface.

Hereinafter, a test using the apparatus shown in FIG. 1 and its results will be described. Table 1 shows the magnets used in this test,
Electrodes, magnets, and other conditions are shown. As shown in this table, a cobalt-based metal-bonded grindstone (diameter 150 mm, thickness 10 mm) containing # 325 abrasive grains was used for the magnet 12 as a conductive and magnetic grindstone. This grinding wheel is equivalent to conventional ELID grinding. The electrode 14 is not a conventional copper (or copper alloy, carbon), but a conductive and magnetic electrode made of iron. Thereby, a strong magnetic field B is applied between the grindstone 12 and the electrode 14.
Could be formed. Further, a ferrite magnet having no conductivity, that is, an anisotropic Sr ferrite magnet (3600 to 4000 Gauss) was used as the magnet 20a. Other voltages, currents and pulse times are
It is almost the same as grinding.

[0023]

[Table 1]

FIG. 5 shows test results according to the present invention.
(A) is a comparison diagram of the actual electrolytic current value, and (B) is a comparison diagram of the electrolytic non-conductive film thickness. As shown in FIG. 5A, in the front S pole / back N pole (same as FIG. 1), about twice the current in the stable region after 30 minutes as compared with the case without the magnetic field (broken line). In the same manner, in the case of the front N pole / rear south pole (the reverse of FIG. 1), the current is between the absence of the magnetic field (broken line) and the front S pole / rear N pole. Therefore, by changing the direction or strength of the magnetic field, the electrolytic current can be controlled, whereby the amount of protrusion of the abrasive grains can be controlled. Also, particularly during grinding, by changing the direction or strength of the magnetic field, such as when high efficiency processing is required, increase the amount of protrusion of abrasive grains,
When a high-quality finished surface is required, the amount of protrusion of the abrasive grains can be reduced.

FIG. 5B is a comparison diagram of the electrolytic non-conductive film thickness.
It can be seen that the ELID grinding shown in FIG. 6 can be controlled. It should be noted that the present invention is not limited to the above-described embodiment, and it is needless to say that various changes can be made without departing from the gist of the present invention.

[0026]

As described above, according to the method and apparatus of the present invention, a conductive liquid is caused to flow between the conductive and magnetic whetstone 12 and the electrode 14, and the whetstone 1 is applied by the voltage applying device 18.
A current I flows between the electrode 2 and the electrode 14 via a conductive liquid,
In the meantime, a magnetic field B is formed in a direction intersecting the current I by the magnetic field device 20, and the work is ground while the grindstone is being dressed by electrolysis. Therefore, the current I is applied to the conductive liquid between the grindstone and the electrode and the grindstone surface. The magnetic field B can be formed to intersect, and the cations and anions contained in the conductive liquid can be moved in opposite directions along the grindstone surface according to the so-called Fleming's left-hand rule, and are simultaneously generated from the grindstone. Fe ions and the like can also be moved along the grindstone surface. Therefore, the distribution of ions in the conductive liquid changes due to the magnetic field, and thereby the electrolytic current can be changed. Further, since the Fe ions and the like are positively moved along the surface of the grindstone, the protrusion amount of the abrasive grains can be promoted, and the adhesion of metal to the electrode surface can be reduced.

Therefore, the grinding method and apparatus using a magnetic field of the present invention can control the electrolytic current, thereby controlling the amount of protrusion of the abrasive grains, and the amount of metal adhered to the electrode surface. , And thereby a long-time continuous operation can be achieved.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a first embodiment of a grinding apparatus according to the present invention.

FIG. 2 is a partial front view (A) of FIG. 1 and a partial cross-sectional view (B) along line XX thereof.

FIG. 3 is a relationship diagram of a current I, a magnetic field B, and a force f acting between a grindstone and an electrode.

FIG. 4 is a second embodiment of the grinding apparatus according to the present invention.

FIG. 5 is a test result according to the present invention.

FIG. 6 is an explanatory diagram showing an ELID cycle in the ELID grinding method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Work 10 Grinding device 12 Grinding stone 14 Electrode 16 Nozzle 18 Voltage application device 18a DC power supply 18b Feeder 20 Magnetic field device 20a Magnet I Current B Magnetic field f Force

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-304966 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B24B 53/00 B23H 3/00

Claims (8)

(57) [Claims] 1. A conductive liquid flows between a conductive and magnetic whetstone and an electrode, a current flows between the whetstone and an electrode via a conductive liquid, and intersects the current during the flow. A grinding method using a magnetic field, comprising: forming a magnetic field in a direction; and grinding the work while dressing the grindstone by electrolysis. 2. The grinding method using a magnetic field according to claim 1, wherein the magnetic field is changed during grinding. 3. A conductive and magnetic whetstone having a contact surface with a workpiece, a conductive and magnetic material electrode opposed to the whetstone at an interval, and a conductive liquid between the whetstone and the electrode. Nozzle, and a voltage applying device for flowing a current through the conductive liquid therebetween, and a magnetic field device for forming a magnetic field in a direction intersecting the current therebetween, thereby dressing the grindstone by electrolysis. A grinding device using a magnetic field, which grinds a workpiece while grinding. 4. The grinding apparatus according to claim 3, wherein directions of the magnetic field and the current are substantially orthogonal. 5. The grinding device using a magnetic field according to claim 3, wherein the grinding wheel and the electrode are made of a ferromagnetic material. 6. The grinding apparatus using a magnetic field according to claim 3, wherein at least a portion of the magnetic field device opposed to the grindstone and the electrode is made of an insulator. 7. The grinding device using a magnetic field according to claim 3, wherein the magnetic field device is a permanent magnet. 8. The grinding device using a magnetic field according to claim 3, wherein the magnetic field device is an electromagnet.