JP2580806B2 - Electrolytic dressing method and apparatus - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method and an apparatus for electrolytically dressing a grindstone using a conductive binder.

"Prior art" When cutting or grinding hard brittle materials such as silicon, ferrite, and ceramics, use super-abrasive grains as abrasives and use metal as a binder to increase the wear resistance of the grindstone. In many cases, a metal-bonded grindstone or an electroformed grindstone, etc., using a steel is used.

By the way, in this kind of metal bond grindstone or electroformed grindstone, when cutting such a hard brittle material, the wear of the superabrasive grains is faster than the wear rate of the binder, and it is early after the start of grinding. There has been a problem that the cutting edge of the superabrasive grains on the ground surface is flattened and the amount of projection of the superabrasive grains is reduced, resulting in a marked decrease in sharpness.

For this reason, conventionally, in order to recover sharpness, SiC
, Al ₂ O _3, or the use of a dressing stone using abrasives, against the grinding surface of the frequent or grinding at the same time as the grinding wheel in between the grinding method for performing dressing has been employed.

However, in this method, the superabrasive grains are also damaged together with the binder, so that the abrasive layer is severely worn, the life of the grindstone is significantly shortened, and the operating rate of the grinding machine is limited by the dressing operation, thereby reducing the work efficiency. There is a drawback that causes a decrease.

Therefore, as shown in FIG. 5, a method of performing electrolytic dressing of a ground surface in parallel with grinding has been proposed in part.

In the figure, reference numeral 1 denotes a disk-shaped cutting grindstone, which is mounted on a spindle shaft 2 of a grinding machine, and an electrode 3 is arranged so as to cover a part of the outer periphery of the grindstone 1.

The electrode 3 is entirely formed of a metal such as copper, and includes a pair of crescent-shaped side plates 3A and a top plate portion 3B for fixing these side plates 3A in parallel. 4 are connected.

By rotating the grindstone 1 and grinding the workpiece W, the anode of the power supply is connected to the spindle shaft 2 of the grindstone 1 and the cathode is connected to the electrode 3, and at the same time, the electrolytic solution is supplied from the liquid supply path 4. The metal binder in the abrasive layer of the rotating grindstone 1 is gradually eluted.

According to this method, since only the binder is removed while leaving the abrasive grains, the effect of promoting the cutting of the superabrasive grains and maintaining good sharpness without damaging the superabrasive grains can be obtained.

[Problems to be Solved by the Invention] However, in the above dressing method, the anode is directly connected to the grindstone 1 and the electrode 3 has the side plate portions 3A. Dressing also proceeds. For this reason, when this method is used especially for an ultra-thin blade whetstone used for processing a semiconductor element, etc., there is a disadvantage that the thickness of the whetstone cannot be neglected and the cutting width accuracy is reduced.

Further, in the above method, the gap between the electrode 3 and the grindstone 1 has to be set to a relatively large value of about several mm to several cm, so that the effect of correcting the irregularities of the grinding surface of the grindstone is small. Truing had to be done separately.

Furthermore, since a large current is directly passed through the spindle shaft 2, when a cutting machine is used for a grinding machine in which the cut amount is controlled by a resistance value between the work material W and the grindstone 1, the leakage current may malfunction. Etc., which may have an adverse effect.

"Means for Solving the Problems" The present invention has been made to solve the above-mentioned problems, and the electrolytic dressing method of the present invention firstly arranges an insulator between and around a pair of electrodes, A dressing jig that exposes the tip of the electrode is arranged so that the tip of each electrode faces the grinding surface of the grindstone at a certain interval, and supplies the electrolytic grinding liquid between each electrode and the grinding surface. At the same time, the resistance between at least one of the electrodes and the abrasive layer is measured, and a current is applied between the electrodes while moving the dressing jig toward and away from the grindstone so that the resistance takes a value within a certain range. And

Prior to electrolytic dressing, the tip of each electrode was covered with an insulator, and the insulator was cut with a grindstone to be dressed, thereby forming a slit having a slightly larger opening width than the thickness of the grindstone. The tip surface of each electrode may be exposed at the bottom of the slit.

On the other hand, the electrolytic dressing apparatus according to the present invention supports a pair of electrodes in an insulated state, and adjusts the resistance value of at least one of the electrodes and the abrasive layer with the dressing jig exposing the tip surfaces of these electrodes. A separation amount detecting mechanism for measuring,
A separation amount adjusting mechanism that supports the dressing jig such that the tip end surface of each electrode faces the grinding surface of the grindstone, and moves the dressing jig toward and away from the grindstone in accordance with an output signal from the separation amount detection mechanism. And a liquid supply means for supplying an electrolytic grinding liquid to a gap between each electrode and the grinding surface, and a power supply mechanism for supplying electricity between the electrodes.

In addition, the dressing jig embeds a pair of electrodes in the insulator at a distance from each other, forms a slit having a width larger than the thickness of the outer peripheral portion of the grindstone at the tip of the insulator, and forms a tip of each electrode. Electrolytic dressing may be performed with the slit being exposed on the bottom surface of the slit at an interval, and an outer peripheral portion of a grindstone inserted into the slit.

In the dressing jig, a liquid supply path may be formed as a liquid supply means between the electrodes.

[Operation] According to the above-described electrolytic dressing method and apparatus, the dressing speed can be feedback-controlled by adjusting the amount of current. Therefore, by performing dressing simultaneously with grinding, the abrasive wear rate on the ground surface can be reduced. And the dressing speed can be balanced, and good grinding efficiency can be maintained over a long period of time.

In addition, since current flows between a pair of electrodes arranged opposite to the grinding surface of the grindstone, the current output from one electrode travels through the grinding fluid and enters the grindstone, flows through the surface portion of the grinding surface of the grindstone,
The current flows out from the grinding surface facing the other electrode, and finally, the current enters the other electrode. At that time, the metal binder elutes from the grinding surface of the grindstone, and the dressing proceeds. Therefore, almost no current flows on the side surface of the abrasive layer, and the side surface of the abrasive layer is hardly dressed. Therefore, the thickness of the abrasive layer is prevented from being reduced, and the grinding accuracy is improved over a long period of time. Can be maintained.

In addition, since the position of the dressing jig is controlled by directly or indirectly detecting the resistance value between the abrasive layer and the electrode, the gap between the ground surface and the electrode must be kept at an extremely small constant value. Is easy. Therefore, the dressing strength changes sharply in response to the unevenness of the ground surface, and the effect of correcting the shape of the ground surface is high.

In addition, since the abrasive layer is energized only in a narrow surface layer portion facing between the respective electrodes, unnecessary current does not flow to other portions of the grindstone, and a malfunction of the control circuit of the grinding machine or the like may occur. There is no possibility of inviting.

In addition, when a slit is formed at the tip of the dressing jig, and the tip surface of each electrode is exposed at the bottom of the slit, the side surfaces of the abrasive layer of the grindstone are electrically shielded on both side walls of the slit. Therefore, it is possible to further prevent the side surface of the abrasive grain layer from being dressed.

Further, when a liquid supply path is formed between the electrodes in the dressing jig, and the electrolytic grinding liquid is supplied through the liquid supply path, the electrolytic grinding liquid is effectively applied to the narrow gap between each electrode and the grinding surface. Can supply. Therefore, the dressing efficiency can be improved, and the metal ions eluted from the ground surface are not easily deposited on the electrode surface.

Embodiment FIG. 1 is a schematic view showing an embodiment of an electrolytic dressing apparatus according to the present invention.

Reference numeral 10 in the figure is a cutting grindstone such as a metal bond grindstone using a conductive binder, an electroformed grindstone or an electrodeposited grindstone,
The work table 12 is fixed to the spindle shaft 11 of the grinding machine.
The workpiece W fixed above is cut while supplying the grinding liquid from the nozzle 13.

On the other hand, reference numeral 14 denotes a dressing jig, which is a rectangular parallelepiped insulator 15 as shown in FIG. 2 and a pair of elongated plate-like electrodes embedded in the insulator 15 at intervals. It consists of 16 parts. The electrode 16 is an insulating material including a lead wire except for a portion corresponding to the bottom of the slit 18.
15 and insulated by insulating coating.

At the center of the insulator 15, a liquid supply hole 17 is formed along the middle of each electrode 16, and at the center of the distal end surface of the insulator 15, the width of the outer periphery of the grindstone 10 is almost completely inserted. slit
The slits 18 are formed up and down, and a part of the tip surface of each electrode 16 is exposed at the bottom surface of the slit 18.

In order to form such a slit 18, as shown in FIG. 4, only the base end of each electrode 16 is exposed (however, an electrically insulating coating is applied), and the ends are aligned. After being buried in parallel inside the insulator 15, the grindstone 10 to be dressed is ground to a position where the tip of each electrode 16 is exposed.
According to this method, it is easy to form the slit 18 having a width suitable for the thickness of the grindstone.

As a material of the insulator 15, various kinds of plastics, ceramics, and any other insulating materials may be used, but a material having good machinability is preferable. As the material of the electrode 16, a highly corrosion-resistant metal such as Ni, a Ni-based alloy, stainless steel, or Ta, or carbon or graphite is preferable.
Although the illustrated electrode 16 is in the shape of an elongated plate, the shape is not limited to this, and may be a rod or a terminal.

The thickness of the electrode 16 is determined according to the grindstone diameter and the grindstone thickness. In addition, the distance between the electrodes 16 is adjusted by the electrolytic grinding fluid.
Care should be taken not to short circuit between them. In addition, electrodes
The leads connected to 16 should also be well insulated.

The dressing jig 14 is fixed to the drive unit 20 of the separation amount adjusting mechanism 19, and is supported by the slit 18 with the outer peripheral portion of the grindstone 10 inserted to the back.

The separation amount adjusting mechanism 19 includes a high-precision stepping motor or the like as a driving source, and moves the dressing jig 14 toward and away from the grindstone 10 in accordance with an output signal from a separation amount detecting mechanism 24 described later.

A power supply device 22 is connected to each electrode 16 via an ammeter 21 to supply a settable constant current. Power supply device
The output capacity of 22 should be determined in consideration of ten types of grindstones, necessary dressing speed, and the like, but may be about 50 V × 10 ° for a normal grindstone.

A voltmeter 23 is connected between the electrodes 16, and the voltmeter 23 is further connected to a separation amount detection mechanism 24. When the voltage between the electrodes 16 exceeds a predetermined upper limit value (the resistance between each electrode 16 and the grindstone 10 increases), the separation amount detection mechanism 24 activates the separation amount adjustment mechanism 19, and the voltage between the electrodes becomes the upper limit value. The dressing jig 14 is advanced to a position below. When the voltage between the electrodes falls below the lower limit (the resistance between each electrode 16 and the grindstone 10 decreases), the distance adjusting mechanism 19 is operated to retract the dressing jig 14 to a position above the lower limit. Has become.

To use the above device, connect the liquid supply hole 17 to a liquid supply pump (not shown) and slit the electrolytic grinding liquid at a constant flow rate.
It is supplied to the gap between 18 and the grinding wheel 10. Then, the power supply device 22, the separation amount detection mechanism 24, and the separation amount adjustment mechanism 19 are operated, respectively.
The dressing jig 14 is moved to adjust the distance between each electrode 16 and the grinding surface of the grindstone 10 to be within a certain range. The optimum amount of separation differs depending on the type of the grindstone 10, and is set to, for example, 1 to 500 μm, preferably about 5 to 100 μm in the case of an electroformed thin blade grindstone. If the thickness is less than 1 μm, a short circuit between the electrode 16 and the grindstone 10 occurs at the beginning of the dressing, and the dressing efficiency is reduced, or the wear of the electrode 16 due to the passage of cuttings is not preferred. On the other hand, if it is larger than 500 μm, the effect of modifying the shape is reduced, and the ratio of dressing of the grinding wheel side surface is relatively increased, so that the dressing efficiency of the grinding surface of the grinding wheel is relatively reduced.

Further, the current density at the tip end surface of the electrode 16 is set to 0.1 to 100, preferably 0.1 to 50 ° / cm ² . If it is less than 0.1 A / cm ² , sufficient dressing cannot be performed, and if it is more than 100 A / cm ² , the electrolysis rate of the electrolytic solution increases, and a dressing effect commensurate with the increase in current cannot be expected. Note that the current density at the tip end surface of the electrode 16 substantially corresponds to the current density at the grinding wheel grinding surface.

It is desirable to continuously apply the current to the electrode 16,
Approximately the same effect can be obtained even if the operation is performed intermittently during grinding. In addition, even if the current is DC as shown,
It may be a pulse current or the like.

Since the distance between the grinding wheel 10 and the electrode 16 is small, a commonly used grinding fluid with low electrical conductivity can be used as the electrolytic grinding fluid, but in order to increase the dressing efficiency, improve the electrical conductivity. For this purpose, it is desirable to add an electrolyte containing NO ₃ ⁻ , Cl ⁻ , SO ₄ ²⁻ or the like. In order to prevent corrosion of the apparatus main body due to the addition of these electrolytes, an inhibitor may be added together.

According to the electrolytic dressing apparatus and method having the above-described configuration, the dressing speed can be feedback-controlled by adjusting the amount of current supplied to the electrode 16, so that the dressing proceeds simultaneously with the grinding to perform the dressing. The wear rate and the dressing rate can be balanced, and good grinding efficiency can be maintained over a long period of time.

Also, a pair of electrodes arranged opposite to the grinding surface of the grinding wheel 10
Since the current flows between 16, the electric current flows through the grinding fluid and flows mainly to the surface portion of the grinding surface, and hardly flows to the side surface portion of the grindstone 10. Thereby, the side surface of the grindstone 10 is not dressed,
Good grinding accuracy can be maintained over a long period of time by preventing the grinding wheel 10 from being thinned.

Further, in this example, since the position of the dressing jig 14 is controlled by measuring the voltage between the electrodes 16, the ground surface and the electrode 16 are controlled.
It is easy to keep the gap to the exact, very small constant value. For this reason, the dressing strength changes sharply in response to the unevenness of the ground surface, the effect of correcting the shape of the ground surface is high, and the configuration can be simplified as compared with a configuration in which the resistance value between the grindstone 10 and the electrode 16 is measured. Also, since the whetstone 10 is energized only in the surface layer portion in a narrow range opposed between the electrodes 16,
No extra current flows to other parts of the grindstone 10, and there is no possibility that a malfunction of a control circuit or the like of the grinding machine is caused.

In addition, a slit 18 is formed at the tip of the dressing jig 14, and the tip surface of each electrode 16 is exposed at the bottom surface of the slit 18, so that the side surfaces of the grindstone 10 are shielded on both side walls of the slit 18, and from the side surface. Of the binder can be further prevented.

Further, a liquid supply hole is provided between the electrodes 16 on the dressing jig 14.
Since the electrolytic grinding liquid 17 is formed and the electrolytic grinding liquid is supplied through the liquid supply hole 17, the electrolytic grinding liquid can be effectively supplied to the narrow gap between each electrode 16 and the grindstone 10, and the dressing efficiency is improved.

As the dressing progresses, it is inevitable that the ionized metal binder is reprecipitated on the tip surface of the electrode 16 on the cathode side, although the efficiency is very low. However, since the precipitated metal is shaved off by the superabrasive grains protruding from the grinding surface of the grindstone 10, there is no possibility that the electrode 16 on the cathode side and the grindstone 10 are short-circuited.

The present invention is not limited to the above embodiment, and the configuration of each unit may be changed as described below as needed.

For example, in the above-described embodiment, the constant current type power supply device 22 is used, and the voltage between the electrodes 16 is measured.
Although the resistance between the grinding wheel 10 and the grinding wheel 10 was indirectly detected, the spindle shaft 11 of the grinding wheel 10 and one of the electrodes 16 were used instead.
The jig position may be controlled by directly measuring the resistance value (or voltage) between them.

Further, the liquid supply path may not be formed inside the dressing jig 14 and the liquid may be supplied from the outside. Further, the present invention may be applied to a grindstone other than a disc-shaped grindstone such as a cup-shaped grindstone or an inner peripheral grindstone. It is also possible to apply

"Experimental Example" Next, the effect of the present invention will be demonstrated with an experimental example.

(Experimental Example 1) An apparatus similar to that shown in FIG. 1 was prepared, and dressing of the following diamond electroformed grindstone (electrodeposited Ni bond) was performed in parallel with the grinding.

Outer diameter 101mm x thickness 0.3mm x inner diameter 40mm Diamond abrasive grain size: 20 / 30μm Abrasive grain content 35vol%, blade tip protrusion 5mm As dressing jig, SUS3 with thickness 1.0mm x width 5mm
04 plates are used as electrodes, leaving only the base end exposed in parallel at 10 mm intervals, burying in epoxy resin, and after curing the resin,
A 6 mmφ liquid supply hole was formed in the middle of each electrode in parallel with the electrodes. Furthermore, after connecting a lead wire to the base end of each electrode, the base end was covered with an insulating material.

Next, this dressing jig was fixed to a slicing machine via a separation amount adjusting mechanism equipped with a micrometer, and was allowed to advance and retreat toward the center of the grindstone, and was opposed to the outer peripheral portion of the grindstone. Furthermore, a resistance meter was connected between each electrode and the grindstone.

Next, while operating the slicing machine and rotating the electroformed thin blade grindstone, the dressing jig was moved toward the grindstone by the separation amount adjusting mechanism, and cut into the tip surface thereof. When the two ohmmeters both showed a short circuit, the cutting was stopped, and the dressing jig was retracted 5 μm from that position using a micrometer.

Next, each electrode was connected to a DC constant current power supply, a liquid supply nozzle was fixed at the tip of the liquid supply hole, and a liquid supply pump was connected to the base end of the liquid supply hole.

After the above preparation was completed, a grinding experiment was performed under the following grinding conditions and dressing conditions.

Work material: Al ₂ O ₃ · TiC material, length 75 mm x width 75 mm x thickness 4 mm Feed rate: 30 mm x min. Depth of cut: 4.5 mm Pitch: 1 mm Total grinding distance: 5.25 m Grinding fluid: city water + Inhibitor small amount + NaNO ₃ 10 g / dressing current: 0.1 A Distance between each electrode and ground surface: 5 to 50 μm As a result, the cutting resistance in the normal direction showed 1 kgW in the initial stage of cutting, and then became constant at 0.5 kgW. The radial wear of the electroformed thin blade grindstone after cutting 5.25 m was 38 μm, and the variation range of the maximum chipping at each cutting line on the surface of the work material was in a very narrow range of 20 to 25 μm.

In addition, when the shape change of the cutting edge was cut into another work material of the same material by half cutting and examined from the cross-sectional shape of the formed groove, the thinning amount of the grindstone due to wear at a position 200 μm from the tip of the cutting edge was It was only 10 μm.

Next, after correcting the amount of grinding wheel cut by the amount of wear, the position of the dressing jig was optimized, and a new work material of the same material was cut again under the same grinding conditions as above, and these operations were repeated. The work material was cut five times.

After completion of each cutting, the kerf width, the cutting resistance, the maximum chipping, the amount of thinning at a position of 200 μm from the tip of the cutting edge, and the amount of cumulative wear in the radial direction were measured. Table 1 shows the results. The measurement was performed at the center of the final cutting line of each work material.

(Comparative Example 1) Instead of the dressing jig in Experimental Example 1,
15mm width x 15mm thickness rectangular dressing whetstone (WC400
A vitrified grindstone) was arranged along the front end of the same work material as described above, and the work material was cut under the same cutting conditions as above, and the dressing grindstone was cut for each cutting line. In this way, five workpieces were cut while correcting the cutting depth each time one workpiece was processed.

Table 1 shows the results of measurements on the same items as in the above-mentioned examples.

(Experimental Example 2) An apparatus similar to that of FIG. 1 was prepared, and the following diamond metal bond grindstone (bond: 85 wt% Cu + 15 w
t% Sn).

Outer diameter 101mm x thickness 1.0mm x inner diameter 40mm Diamond abrasive grain size: 40 / 60μm Abrasive grain content 25vol%, blade tip protrusion 10mm As a dressing jig, a 2.0mm thick x 5mm wide carbon plate is used as an electrode. The sheets were buried in epoxy resin with only the base end exposed at a parallel interval of 10 mm, and after curing the resin, a 6 mmφ liquid supply hole was formed in the middle of each electrode in parallel with the electrodes. Furthermore, after connecting a lead wire to the base end of each electrode, the base end was covered with an insulating material.

Next, this dressing jig was fixed to a slicing machine via a separation amount adjusting mechanism equipped with a micrometer, and was allowed to advance and retreat toward the center of the grindstone, and was opposed to the outer peripheral portion of the grindstone. Furthermore, a resistance meter was connected between each electrode and the grindstone.

Next, while operating the slicing machine and rotating the metal bond grindstone, the dressing jig was moved toward the grindstone by the separation amount adjusting mechanism and cut into the tip surface thereof. The cut was stopped when the two ohmmeters both showed a short circuit, and the dressing jig was retracted by 300 μm from that position using a micrometer.

Next, each electrode was connected to a DC constant current power supply, a liquid supply nozzle was fixed at the tip of the liquid supply hole, and a liquid supply pump was connected to the base end of the liquid supply hole.

Next, the grindstone is rotated, the liquid supply pump is operated to supply the grinding liquid from the liquid supply nozzle, and the current value of the DC stabilized power supply is reduced to 0.
A current was applied between the electrodes at 15 A, and the voltage between the electrodes was measured. The voltage upper limit of the DC power supply is set to 1 for the obtained voltage value of 15 V.
8 V and the lower limit were set to 14 V, and during the grinding, the separation amount adjusting mechanism was operated in accordance with the upper and lower limits to keep the distance between the grinding surface of the grinding wheel and the electrode constant.

After the above preparation was completed, a grinding experiment was performed under the following grinding conditions and dressing conditions.

Work material: Al ₂ O ₃ material, length 200 mm x width 120 mm x thickness 5 mm Feed rate: 30 mm / min. Depth of cut: 6.5 mm Pitch: 2 mm Total grinding distance: 10 m Grinding fluid: city water + small amount of inhibitor + 5 g of NaCl / Dressing current: 0.15 A As a result, the cutting resistance in the normal direction showed 22 kgW at the initial stage of cutting, and then became constant at about 1.7 kgW. The radial wear of the metal bond grindstone after cutting 10m is 350μm, and the maximum chipping variation range of each cutting line on the work material surface is 30
It was in a very narrow range of 3535 μm.

In addition, when the shape change of the cutting edge was cut into another work material of the same material by half cutting and examined from the cross-sectional shape of the formed groove, the thinning amount of the grindstone due to wear at the position of 500 μm from the tip of the cutting edge was It was only 20 μm.

(Comparative Example 2) Instead of the dressing jig in Experimental Example 2,
15mm width x 15mm thickness rectangular dressing whetstone (WC220
A vitrified grindstone) was arranged along the front end of the same work material as described above, and the work material was cut under the same cutting conditions as above, and the dressing grindstone was cut for each cutting line.

As a result of measuring the same items as in the experimental example, the cutting resistance in the normal direction showed 2.4 kgW in the initial stage of cutting, and then the cutting distance
3.1kgW at 3m, 4.8kgW at 6m, 5.9kgW at 10m, gradually increased as the cutting distance increased.

Radial wear of metal bond whetstone after cutting 10m is 580μm
was. The variation range of the maximum chipping at each cutting line on the surface of the work material was 35 to 50 μm. In addition, the amount of thinning of the grindstone due to wear at a position 500 μm from the tip of the
It was 5 μm.

(Experimental Example 3) An apparatus similar to that of FIG. 1 was prepared, and dressing of the following diamond electroformed grindstone (electrodeposited Ni bond) was performed in parallel with the grinding.

Outer diameter 76.2mm x thickness 0.13mm x inner diameter 40mm Diamond abrasive grain size: 8 / 16μm Abrasive grain content 31vol%, protruding edge 3mm As dressing jig, SUS3 with thickness 0.5mm x width 5mm
04 plates are used as electrodes, leaving only the base end exposed in parallel at 10 mm intervals, burying in epoxy resin, and after curing the resin,
A 6 mmφ liquid supply hole was formed in the middle of each electrode in parallel with the electrodes. Furthermore, after connecting a lead wire to the base end of each electrode, the base end was covered with an insulating material.

Next, this dressing jig was fixed to a slicing machine via a separation amount adjusting mechanism equipped with a micrometer, and was allowed to advance and retreat toward the center of the grindstone, and was opposed to the outer peripheral portion of the grindstone.

Next, connect each electrode to a stabilized DC power supply and set the current to 0.
05A, adjust the voltage value to 8V, operate the slicing machine while energizing between the electrodes, rotate the electroformed thin blade whetstone, move the dressing jig toward the whetstone by the separation amount adjustment mechanism, and I cut it. Then, when the voltage between the electrodes drops and a short circuit is indicated, the cutting is stopped,
From that position, use a micrometer to
It was retracted by 50 μm. Next, a liquid supply nozzle was fixed to the tip of the liquid supply hole, and a liquid supply pump was connected to the base end of the liquid supply hole.

After the above preparation was completed, a grinding experiment was performed under the following grinding conditions and dressing conditions.

Work material: Mirror-polished HIP ferrite (joined to the table with wax) Length 20 mm x width 50 mm x thickness 2 mm Feed rate: 20 mm / min. Depth of cut: 2.5 m Pitch: 0.5 mm Total number of cutting lines: 90 (Line) × 100 (work material) Grinding fluid: city water + small amount of inhibitor + 10 g of NaNO ₃ / dressing current: 0.05A The above test was conducted five times, but in all cases, the work material peeled off and scattered from the base metal. The cutoff of 9000 lines, which is the set value, was achieved without any occurrence.

(Comparative Example 3) The cutting test was carried out five times with the same conditions as in Experimental Example 3 without using the dressing jig in Experimental Example 3 above.

As a result, in each of the cutting tests, the number of cutting lines until the work material peeled off and scattered from the base metal before reaching the set value and the average work material was scattered was 826 lines.

“Effects of the Invention” As described above, according to the electrolytic dressing method and apparatus according to the present invention, the following excellent effects can be obtained.

Since the dressing speed can be feedback-controlled by adjusting the amount of electricity, by performing dressing simultaneously with grinding, it is possible to balance the abrasive wear speed and the dressing speed on the ground surface, and over a long period of time. And good grinding efficiency can be maintained.

Since current flows between a pair of electrodes arranged opposite to the grinding surface of the grindstone, current flows mainly through the surface of the grinding surface through the grinding fluid, and hardly flows on the side surface of the abrasive layer. Thereby, the side surface of the abrasive grain layer is less likely to be dressed, the thickness of the abrasive grain layer is prevented from being reduced, and good grinding accuracy can be maintained for a long period of time.

Since the position of the dressing jig is controlled by detecting the resistance value between the abrasive layer and the electrode, it is easy to accurately maintain the gap between the ground surface and the electrode at a very small constant value. Therefore, the dressing strength changes sharply in response to the unevenness of the ground surface, and the effect of correcting the shape of the ground surface is high.

Since the abrasive layer is energized only in a narrow area of the surface layer facing between the electrodes, unnecessary current does not flow to other parts of the grinding wheel, which may cause a malfunction of the control circuit of the grinding machine. There is no.

When a slit is formed at the tip of the dressing jig, the side surfaces of the grindstone are shielded on both side walls of the slit, so that the thickness of the grindstone can be further prevented.

When a liquid supply path is formed between the electrodes on the dressing jig, the electrolytic grinding liquid is supplied through the liquid supply path, so that the electrolytic grinding liquid can be effectively applied to the narrow gap between each electrode and the grinding surface. Can supply. Therefore, the dressing efficiency is improved, and the advantage that metal ions eluted from the ground surface are not easily deposited on the electrode is obtained.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an embodiment of an electrolytic dressing apparatus according to the present invention, FIGS. 2 and 3 are longitudinal sectional views and front views showing a dressing jig of the apparatus, and FIG. It is a longitudinal cross-sectional view which shows the dressing jig. FIG. 5 is a schematic view showing a conventional electrolytic dressing method. W: Work material, 10: Grinding stone, 11: Spindle shaft, 14 ...
... dressing jig, 15 ... insulator, 16 ... electrode, 17 ...
... Supply hole (Supply path), 18 ... Slit, 19 ... Separation amount adjustment mechanism, 20 ... Drive section, 21 ... Ammeter, 22 ... Supply mechanism, 23 ... Voltmeter, 24 ... Separation amount detection mechanism.

Claims (5)

(57) [Claims] 1. A method for electrolytically dressing a grinding surface of an abrasive layer while rotating a grindstone having an abrasive layer using a conductive binder around an axis, comprising: A dressing jig with the insulators placed and the tips of the electrodes exposed is placed so that the tips of the electrodes face the grinding surface of the grindstone at a fixed interval, and the gap between each electrode and the grinding surface is set. While supplying the electrolytic grinding fluid to the electrode, the resistance value of at least one of the electrodes and the abrasive layer is measured, and while the dressing jig advances and retreats with respect to the grinding stone so that the resistance value takes a value within a certain range, each electrode is An electrolytic dressing method, characterized in that a current is supplied between the electrodes. 2. Prior to the electrolytic dressing, the tip of each electrode is covered with an insulator, and the insulator is cut with a grindstone to be dressed, so that the opening width is slightly larger than the thickness of the grindstone. 2. The electrolytic dressing method according to claim 1, wherein a slit is formed, and a tip surface of each electrode is exposed at a bottom of the slit. 3. An apparatus for electrolytically dressing a ground surface of an abrasive layer while rotating a grindstone having an abrasive layer using a conductive binder around an axis, wherein the pair of electrodes are supported in an insulated state. A dressing jig exposing the tip surfaces of these electrodes, a separation amount detecting mechanism for measuring a resistance value between at least one of the electrodes and the abrasive layer, and a tip surface of each electrode having the dressing jig. Along with supporting the grinding surface of the grindstone so as to face it, a separation amount adjusting mechanism for moving the dressing jig toward and away from the grinding stone in accordance with an output signal from the separation amount detection mechanism, and a gap between each electrode and the grinding surface. An electrolytic dressing apparatus, comprising: a liquid supply means for supplying an electrolytic grinding liquid; and a power supply mechanism for supplying a current between the electrodes. 4. The dressing jig includes a pair of electrodes buried in an insulator at a distance from each other, and a slit having a width slightly larger than a thickness of an outer peripheral portion of the grindstone is formed at a tip of the insulator. 4. The electrolytic dressing apparatus according to claim 3, wherein the tip of each electrode is exposed at an interval on the bottom surface of the slit, and the electrolytic dressing is performed in a state where an outer peripheral portion of a grindstone is inserted into the slit. 5. The electrolytic dressing apparatus according to claim 3, wherein a liquid supply path is formed as a liquid supply means between the electrodes in the dressing jig.