JPS6244374A - Electro-discharge dresser for metal-bonded diamond grinding wheel - Google Patents

Abstract

PURPOSE:To dress a grinding wheel so efficiently irrespective of the quality of a work and size of diamond abrasive grains, by installing a discharge accelerator, having conductive particles mixed in a grinding fluid sticking fast to a grinding surface, separatably in this grinding surface. CONSTITUTION:While feeding a gap between a grinding surface of a metal- bonded diamond grinding wheel 1 in rotation and an electrode 10 being set up face-to-face in this grinding surface with a grinding fluid arc discharge is generated and the wheel 1 is pressed. At this time, an output signal out of a discharge state detecting circuit 11 is given to an input end at the negative side of a differential amplifier 20, comparing it with the reference value in a discharge state given to an input end at the positive side, and on the basis of the compared result, a motor 22 is driven, a screw 23 is moved, a discharge accelerator 25 composed of conductive matter is made contact with the grinding surface, and its conductive particles is mixed in the grinding fluid stuck on the grinding surface, whereby electro-discharge machining is accelerated, and wheel dressing is carried out in an efficient manner.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an electrical discharge dressing device for a metal-bonded diamond grindstone, which is used in a surface grinder, etc., and is particularly suitable for ceramic grinding.

[Background of the invention]

Conventionally, dressing of a metal-bonded diamond grinding wheel by electric discharge has been performed as follows. That is, an electrode is provided close to and facing the grinding surface of the grinding wheel, and while the grinding wheel is being rotated, an arc discharge is generated while supplying a grinding liquid between the grinding surface of the grinding wheel and the electrode, and the metal of the grinding wheel is The outer peripheral surface of the bond portion was removed and dressed.

In this case, if the object to be ground is electrically conductive, its chips will be mixed into the grinding fluid that adheres to the grinding surface of the grindstone during machining rotation of the grindstone, and the gap between the electrode and the grindstone (discharge gap ) will exist as conductive particles,
Works to promote discharge. However, when the object to be ground is an insulator such as a ceramic, insulating particles are present in the discharge gap and work to suppress discharge, or in other words, dressing. Furthermore, even if the object to be ground is a good conductor, during rough machining using a grindstone with large diamond abrasive grains, that is, during dressing during high-efficiency machining, the distance from the abrasive grain tip to the outer circumferential surface of the metal bond part becomes long, causing electrical discharge. It was difficult and the dressing was not done efficiently.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned circumstances, and provides an electrical discharge dressing device for a metal bond diamond grinding wheel that can dress efficiently regardless of the material of the object to be ground or the size of the diamond abrasive grains. The purpose is to

[Summary of the invention]

In the device of the present invention, when dressing by arc discharge, by bringing a discharge accelerator made of a conductive substance into contact with the grinding surface of the whetstone with appropriate pressure, chips of the discharge accelerator are added to the grinding fluid adhering to the grinding surface. The above-mentioned object is achieved by mixing conductive particles, which promote the generation of the arc discharge.

[Embodiments of the invention]

The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a diagram showing the overall configuration of an embodiment of an electric discharge dressing device for a metal-bonded diamond grinding wheel according to the present invention, in which numeral 1 indicates a metal-bonded diamond grinding wheel. A flange 4 is attached to the center of the grindstone 1, and as a shaft 5 supported by a bearing 6 rotates, the grindstone 1 is rotatable via the flange 4, for example, in the direction of arrow A. Reference numeral 2 denotes a workpiece, which is placed and fixed on a table 7. 3 indicates a grinding fluid supply nozzle.

8 is a pulse power supply, and the positive pole of the pulse output end is the brush 9.
It is connected to the grinding wheel 1 through the flange 4 and the negative electrode is connected to the electrode 10. 11 is a discharge state detection circuit, the details of which will be described later based on FIG. 3. 12 is a differential amplifier, and the analog output signal from the discharge state detection circuit 11 is applied to its negative input terminal.

Further, the reference value El of the discharge state is given to the positive input terminal. The output voltage of the differential amplifier 12 is amplified by the drive amplifier 13 and applied to the motor 14.

This motor 14 is coupled to a first gear 15, which is meshed with a second gear 16. This gear 16
A pole screw 17 is screwed through the central portion of the plate, and is prevented from moving in the vertical direction.

The pole screw 17 has a lower end connected to the electrode 10.
The upper end is screwed into a nut 19 fixed to the support frame 18. In this case, the nut 19 is fixed to the support frame 18 in an insulated manner,
Further, the motor 14 is also fixed to the support frame 18 in an insulated state.

On the other hand, the output signal of the discharge state detection circuit 11 is
0 to the negative input terminal of the differential amplifier 20.
The reference value E of the discharge state is at the positive input terminal of the .

is given. The output voltage of the differential amplifier 20 is amplified by a drive amplifier 21 and applied to the motor 22 to drive it. This motor 22 rotates an insulating screw 23 and moves this screw 23 in the left-right direction in the figure. 25
is a discharge accelerating material made of a conductive substance, which is connected to the screw 23 via a spring 24, and one end surface thereof can move toward and away from the grinding surface of the grindstone 1 as the screw 23 moves.

At the time of grinding, the workpiece 2 is first fixed on the table 7. Then, the table 7 is moved from side to side, rightward in the illustrated example, by a drive device (not shown), and the workpiece 2 is moved by a drive device (not shown).
The grindstone 1 is rotated at high speed while approaching the grindstone 1 side, and a grinding fluid is supplied as shown by the arrow, whereby the workpiece 2 is ground.

At this time, the grindstone 1 is also worn, and this will be explained below. FIG. 2 is a partially enlarged sectional view of the grindstone 1, and in FIG. 2, the same parts as in FIG. 1 are designated by the same reference numerals. Further, 1a indicates diamond abrasive grains, and 1b indicates a metal bond portion. δ1 indicates the amount of protrusion of the abrasive grain 1a from the metal bond portion 1b when the tip of the diamond abrasive grain 1a is worn out.

In such a worn state of the grindstone 1, the grinding efficiency decreases, so the amount of protrusion of the diamond abrasive grains 1a is increased as shown by δ. That is, the grinding wheel 1 is dressed by electric discharge machining (the outer peripheral surface portion of the metal bond portion 1b is removed).
This will be explained below. A pulse voltage from a pulse power source 8 is applied between the electrode 10 and the metal bond diamond grinding wheel 1 (metal bond portion tb) to generate an earth discharge between them. On the other hand, the grindstone 1 is rotated by a motor 5 (not shown), and grinding fluid is supplied to the grinding surface of the grindstone 1 from the grinding fluid supply nozzle 3. The discharge state detection circuit 11 detects the arc discharge state, and as will be described later, the output signal of the discharge state detection circuit 11 is designed to output a high voltage in proportion to the amount of discharge generated. Therefore, when the electrode 10 is far away from the grinding wheel 1, the output signal of the discharge state detection circuit 11 is a low voltage, for example Ov.
2 and compared with the reference value E1 of the discharge state, the motor 14 is rotated and the electrode 10 is
is sent by the pole screw 17 so that it approaches the grindstone 1. When the gap length between the electrode 10 and the grinding wheel 1 (to be precise, the metal bond part 1b) becomes short enough to generate an electric discharge, an arc discharge occurs, and as a result, the outer peripheral surface portion of the metal bond part 1a is removed from the surface side by electric discharge machining. Ru. The gap length for discharge generation is
In terms of discharge characteristics, as shown in FIG. 2, the larger the amount of conductive particles 25a in the discharge gap, the larger the discharge. That is, the conductive particles 25a are placed in the gap between the electrode 10 and the grinding wheel 1 using the grinding fluid 3a.
Discharge dressing is facilitated by mixing with the above. Therefore, in the present invention, a discharge accelerating material 25 made of a conductive material is disposed so as to be able to move toward and away from the grinding surface of the grinding wheel 1, and the material is made of a material that is relatively easy to grind, such as graphite (for example, a graphite electrode). The material is good. The pressing force of the discharge promoting material 25 against the grinding surface of the grinding wheel 1 during dressing is determined by the reference value E of the discharge state when the output signal from the discharge state detection circuit 11 is applied to the negative input terminal of the differential amplifier 20.
, and the differential voltage is power amplified by the drive amplifier 21 to rotate the motor 22 and adjusted by changing the position of the screw 23.

Next, a specific example of the discharge state detection circuit 11 will be explained based on FIG. 3. In FIG. 6, the same reference numerals as in FIG. 1 indicate the same parts. In addition, lla and llb are voltage dividing resistors for reducing the voltage between the electrode 10 and the grinding wheel 1 to an extent that does not damage each circuit that constitutes the detection circuit 11, which will be described later. 11c is a comparison amplifier Ii, and 11d is an AND gate. In the following, the operation of such a detection circuit 11 will be explained below. This will be explained with reference to the time chart shown in FIG. First, grindstone 1 and electrode 10
During this period, a pulse voltage as shown in waveform E in FIG. 4 is applied, and a voltage as shown in waveform E gap is input to the detection circuit 11. Here, a shows each waveform E gap in a non-discharge state, b in a normal discharge state, C in an abnormal discharge state, and d in a state in which the grinding wheel 1 and the electrode 10 are short-circuited.

Discharge waveform E obtained from the voltage dividing resistors 11a and llb
gap is given to the comparator amplifier 11c and compared with the reference value E3.6 The output waveform of the comparator amplifier 11c and the waveform E
When a waveform synchronized with is applied to the AND gate circuit lid, waveform F is obtained. Waveform G is obtained by applying this waveform F and timing pulse TI from timing pulse generation circuit 11f to D-type flip-flop lie.

This waveform G signal is a discharge state (including abnormal discharge state C and short circuit state d) detection signal, and this detection signal is detected by the resistor 11.
The DC average value is outputted from the output terminal 108 by smoothing by an integrating circuit consisting of g and capacitor llh. In practice, the waveform E ga
Since the states a, b, c, and d are mixed irregularly in time at p, the reference value E is set through experiments to facilitate discharge between the electrode 10 and the grinding wheel 1. The pressure contact force (contact pressure to the grinding surface of the grindstone 41) of the discharge promoting material 25 is adjusted so that the discharge promoting material 25 generates the discharge.

〔Effect of the invention〕

Abnormality As mentioned above, in the present invention, the discharge promoting material made of a conductive substance is brought into contact with the grinding surface of the whetstone and mixed into the grinding liquid adhering to the grinding surface, so that it is interposed in the discharge gap. Even if the object to be ground is an insulating material such as ceramic, or a grindstone for rough machining with large diamond abrasive grains, electrical discharge will be promoted and the dressing will be more efficient. .

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of an embodiment of the device of the present invention, FIG. 2 is a partially enlarged sectional view of the grindstone in FIG. 1, FIG. 3 is a block diagram showing a specific example of the discharge state detection circuit, and FIG. FIG. 4 is a time chart for explaining the operation of the above circuit. 1...Metal bond diamond grinding wheel, 1a...Diamond abrasive grain, 1b...Metal bond part, 2...
Workpiece, 3... Grinding fluid supply nozzle, 3a... Grinding fluid, 4... Flange, 8... Pulse power supply, 9...
・Brush, 10... Electrode, 25... Discharge promoting material,
25a...Electroconductive particles. Patent Applicant Hitachi Seiko Co., Ltd. Agent Patent Attorney Tadashi Akimoto Figure 1 Back Figure 2 Figure 3 Figure 4

Claims (1)

[Scope of Claims] 1. In an apparatus for dressing the grinding wheel by generating arc discharge while supplying grinding liquid between the grinding surface of a rotating metal bonded diamond grinding wheel and an electrode placed opposite to the grinding surface. , characterized in that a discharge accelerator made of a conductive substance that mixes conductive particles into the grinding fluid adhering to the grinding surface by contacting the grinding surface is provided on the grinding surface so as to be able to come into contact with and separate from the grinding surface. Electric discharge dressing device for metal bond diamond grinding wheels. 2. Claim 1, characterized in that the discharge promoting material is supported so that the contact pressure to the grinding surface can be adjusted.
Discharge dressing device as described in section.