JPH11262860A - Extremely precise grinding method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide extremely precise grinding work using electrolytic dressing resulting in high finishing precision, a shorter dressing cycle time and less demand of consuming power by satisfying the profile precision of a grinding wheel surface required for precise grinding while maintaining the cutting capability and elasticity of the grinding wheel surface. SOLUTION: A conductive resin bond grinding wheel formed with abrasive grains combined through conductive resin bond is used as a conductive grinding wheel constituting a grinding wheel 2 and electrolytic dressing is applied to the grinding wheel surface 2a of the grinding wheel 2 during grinding work for a workpiece W with the grinding wheel 2. With the electrolysis of the electrolytic dressing, only conductive material is dissolved in resin bond and abrasive grains and resin are left on the grinding wheel surface 2a, without requiring the production of an oxide film as in ELID grinding.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultra-precision grinding method and a grinding apparatus, and more particularly to a grinding technique using a super-abrasive grindstone utilizing electrolytic dressing.

[0002]

2. Description of the Related Art In recent years, as one of the advanced precision processing techniques,
Attention has been paid to ultra-precision grinding technology using super-abrasive grindstones.Particularly, diamond grindstones in which diamond abrasive grains are bonded by resin-based or metal-based bonding materials are ideal for grinding hard and brittle materials such as ceramics. Used as a whetstone.

The truing and dressing of this type of superabrasive grindstone is difficult with conventional general mechanical truing and dressing techniques, and requires a long time for the operation. was there.

In this regard, attention has been paid to the fact that most of these types of superabrasive grindstones are conductive grindstones using a conductive bonding material such as a conductive resin bond or a metal bond. An example in which an electric truing and dressing technique such as electrolytic dressing is applied to truing and dressing of a superabrasive grindstone is increasing.

[0005] Discharge truing performs truing using a discharge action, and is generally applied to truing of a metal bond grindstone. In the case of a centerless grinder equipped with a grinding wheel made of a metal bond and a diamond grinding wheel, this discharge truing is performed by using a grinding wheel (+).
A discharge truer (discharge truing electrode) composed of a metal disk provided at regular intervals in opposition to the grinding wheel surface (cylindrical grinding surface) of the grinding wheel as a pole.
By applying positive and negative voltages to the electrodes while rotating the grinding wheel and the discharge tool at a predetermined speed, the metal bond portion on the surface of the grinding wheel is dissolved and removed by the discharge action between the electrodes, and the grinding is performed. The protruding state of the abrasive grains on the surface is formed and maintained.

[0006] On the other hand, the electrolytic dressing, which performs dressing using an electrolytic action, is also generally applied to dressing of a metal bond grindstone. A typical example of this electrolytic dressing is Electrolytic In-process Dressing (EL).
ID), a metal bond
Taking a centerless grinder equipped with a grinding wheel made of diamond grinding wheels as an example, the grinding wheel has a (+) pole,
Dressing electrodes provided at regular intervals opposite to the grinding wheel surface (cylindrical grinding surface) of the grinding wheel are used as (-) poles, and a coolant (electrolyte) is supplied to these gaps during grinding of the workpiece. When a direct current is passed, the metal bond portion of the ground surface is eluted by the electrolytic action, so that the abrasive grains protrude from the ground surface.

[0007]

However, in such conventional discharge truing and electrolytic dressing,
Each has the following problems, and the desired effect of the ultra-precision grinding technique cannot be sufficiently exerted, so that further improvement has been demanded.

That is, in the former discharge truing, the profile accuracy of the grinding wheel surface of the grinding wheel cannot be improved to a level required for ultra-precision grinding.

Specifically, in ultra-precision grinding using a grinding wheel made of a super-abrasive grinding wheel, it is necessary to ensure the roundness and straightness of the grinding wheel and to precisely align the tips of the abrasive grains. ,
In electric discharge truing, a method is used in which the bonding material of the grinding stone is melted and removed by the discharge action, and the grinding wheel is rotated to remove the material. It is difficult to create a surface with the required profile accuracy.

Moreover, there are many abrasive grains which are hardly held by the bonding material on the surface of the grinding wheel, and the surface of the grinding wheel is in an unstable state. Scratch (scratch) occurs, and high finishing accuracy as precision grinding cannot be obtained.

Further, in the latter electrolytic dressing, it has been difficult to apply it to high-efficiency machining such as centerless grinding for the following reasons.

(1) In the conventional electrolytic dressing, in a high-efficiency machining such as centerless grinding, the grinding wheel is severely worn, and therefore, the frequency of the electrolytic dressing is large and the running cost is high.

That is, the specific mechanism of the conventional electrolytic dressing is shown in FIG. 4 in a state where the surface of the metal bond grinding wheel a having the (+) pole is worn (see FIG. 4).
(a)), a DC current flows while a coolant (electrolyte) is supplied to a gap between the surface of the grinding wheel and the electrode surface of the dressing electrode b which is a (-) pole. Then, by the electrolytic action, first, the metal component (iron) d in the metal bond c on the surface of the grinding wheel is eluted and ionized, and a chip pocket is formed on the surface of the grinding wheel (FIG. 4 (b)). An oxide film e of a metal component d is formed on the surface of the grinding wheel.
(c)). The oxide film e maintains the projected state of the abrasive grains f on the surface of the grindstone and imparts elasticity to the holding of the abrasive grains.

However, in such a configuration in which the oxide film e is formed on the surface of the grindstone, in high-efficiency processing such as centerless grinding, the grindstone is severely worn, and the oxide film e falls off and disappears in a short time. I will. For this reason, it is necessary to frequently perform electrolytic dressing, resulting in an increase in running cost.

(2) Since the cycle time of electrolytic dressing per cycle is relatively long, when a wide grindstone is used as in a centerless grinding machine, the dressing cycle time is particularly long, and the grinding cycle time is reduced. As a result, not only the desired high-efficiency machining cannot be performed, but also high finishing accuracy as precision grinding cannot be stably obtained in ELID grinding.

(3) Due to the length of the dressing cycle time as described above, in the case of a wide whetstone, a uniform dressing effect cannot be obtained over the entire whetstone surface, and the whetstone surface is formed with a required profile accuracy. Difficult to maintain.

(4) In the electrolytic dressing, a relatively large current needs to be passed. Particularly, a large current is required for the electrolytic dressing of a wide grinding wheel, and the power supply device is large and expensive. In addition, the electricity bill increases, leading to a significant increase in running costs.

The present invention has been made in view of such a conventional problem, and an object of the present invention is to provide an ultra-precision grinding process using electrolytic dressing while ensuring the sharpness and elasticity of the grinding wheel surface. Provide ultra-precision grinding technology that satisfies the profile accuracy of the grinding wheel surface required for precision grinding, achieves high finishing accuracy, and can reduce dressing cycle time and power consumption. Is to do.

[0019]

In order to achieve the above object, an ultra-precision grinding method according to the present invention is a grinding method using a conductive grindstone using electrolytic dressing, wherein a conductive resin bond is used as the conductive grindstone. Along with using a conductive resin bond whetstone in which the abrasive grains are combined, during the grinding of the workpiece with this conductive resin bond whetstone,
It is characterized in that electrolytic dressing is performed on the grindstone surface of the conductive resin bond grindstone.

The ultra-precision grinding apparatus of the present invention is a centerless grinding apparatus for carrying out the above-mentioned grinding method, wherein a conductive grinding wheel constituting a grinding wheel has abrasive grains bonded by a conductive resin bond. And an electrolytic dressing electrode is provided facing the surface of the grinding wheel of the grinding wheel.

In the present invention, a conductive resin bond grindstone formed by bonding abrasive grains with a conductive resin bond containing a conductive material that does not require the formation of an oxide film by an electrolytic action is used as the conductive grindstone. An electrolytic dressing electrode is provided to face the grindstone surface of the conductive resin bond grindstone.

During the grinding of the workpiece with the conductive resin-bonded grindstone, a DC current is supplied while supplying a coolant (electrolyte) to a gap between the grindstone surface of the conductive resin-bonded grindstone and the electrode surface of the electrolytic dressing. As a result, the conductive metal component on the grinding surface is eluted by the electrolytic action, the clogging on the grinding wheel surface is removed in-process, and the projected state of the abrasive grains is recovered.

In this case, as the conductive material contained in the resin bond, a metal material such as copper or tungsten is used. For this reason, only the conductive substance (metal component) in the resin bond is dissolved by the electrolytic action, and only the abrasive grains and the resin remain on the surface of the grinding stone, and there is no need to form an oxide film as in ELID grinding. In addition, a sufficient protrusion amount of the abrasive grains can be obtained, and the elasticity of the resin itself has elasticity in the holding state of the abrasive grains.

As a result, the necessary conditions for increasing the grinding efficiency and improving the grinding accuracy (surface roughness), that is, the sufficient amount of protrusion of the abrasive grains, and the bond (including the oxide film) holding the abrasive grains ), The two conditions of resilience are simultaneously satisfied.

Further, since it is not necessary to form an oxide film, electrolytic dressing can be performed even with a wide whetstone with low power consumption, and the electrolytic dressing time can be shortened as compared with ELID grinding.

[0026]

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

Embodiment 1 FIG. 1 shows an ultra-precision grinding apparatus according to the present invention. This grinding device is specifically a centerless grinding machine, and includes an electrolytic dressing device 1 as a dressing device.

The basic configuration of the centerless grinding machine is the same as that of a conventional well-known grinding machine. The centerless grinding machine mainly includes a grinding wheel 2, an adjusting wheel 3, a blade 4, and the like. Is rotatably supported by the adjusting wheel 3 and the blade 4, and is ground while being passed through between the grinding wheel 2 and the adjusting wheel 3 in the axial direction.

The grinding wheel 2 is made of a conductive grinding wheel in which abrasive grains are bonded by a conductive bonding material, and the grinding wheel surface 2a is a cylindrical grinding surface. So-called super-abrasive grains such as fine diamond abrasive grains and CBN (cubic boron nitride) abrasive grains are used as the abrasive grains, and a conductive resin bond containing a conductive substance is used as the conductive bonding material. Preferably, copper (Cu), tungsten (W), or a mixture thereof is contained as a conductive material. In the illustrated embodiment, the conductive grinding wheel 2 is formed by bonding fine diamond abrasive grains by a conductive resin bond.

Although not specifically shown, the grinding wheel 2 is rotatably supported on a grinding wheel base (not shown) via a grinding wheel shaft 5 and is linked to a rotary drive source via a power transmission mechanism. Have been. Further, the grinding wheel 2 is electrically connected to the (+) pole of the power supply 11 via the power supply 10.

In the electrolytic dressing apparatus 1, the dressing electrode 15 is arranged at a position deviating from a grinding position of the grinding wheel 2, that is, a rotational support position of the workpiece W (an upper position of the grinding wheel 2 in the drawing). At the same time, although not shown, an electrolytic solution supply nozzle is provided between the grinding surface 2a of the grinding wheel 2 and the annular electrode surface 15a of the dressing electrode 15.

The electrolytic dressing electrode 15 is specifically in the form of a multi-electrode. In the illustrated embodiment, a plurality of small electrodes 16, 16,... (5 in the illustrated case) are arranged in the axial direction of the grinding surface 2 a of the grinding wheel 2.
) To form an electrolytic dressing electrode 15.

Each of the small electrodes 16 has an annular electrode surface 16 a facing the grinding surface 2 a of the grinding wheel 2.
The annular electrode surface 15a of the electrolytic dressing electrode 15 is formed by the electrode surfaces 16a, 16a,.

Each of the small electrodes 16, 16,... Constituting the dressing electrode 15 is electrically connected to a (-) pole of the power supply 11 from a power supply 17 via a programmable electrode switching unit 18.

The reason why the dressing electrode 15 is in the form of a multi-electrode composed of a plurality of small electrodes 16, 16,... Is to devise a technique for electrolyzing the wide ground surface 2a with a small power source. When a grinding wheel having a narrow grinding wheel width is electrolyzed, a single electrode is used.

In the centerless grinding machine constructed as described above, the workpiece W is rotatably driven on the surface of the workpiece while the workpiece W is rotatably supported centerlessly by the adjusting wheel 3 driven to rotate by the blade 4. Wheel 2 of wheel 2
a, and during the grinding, the dressing apparatus 1 performs in-process electrolytic dressing according to the properties of the ground surface 2a as needed.

In this electrolytic dressing, an electrolytic solution supply nozzle (not shown) supplies an electrolytic coolant between the grinding surface 2a and the annular electrode surface 15a of the dressing electrode 15, and also supplies the grinding wheel 2 and the dressing electrode 15 DC current is supplied to the Then, due to the electrolytic action, the conductive metal component on the grinding surface 2a is eluted, the clogging on the grinding surface 2a is removed in-process, and the projected state of the abrasive grains is recovered and maintained.

In this case, since the conductive material contained in the resin bond is a metal material such as copper or tungsten, only the conductive material A in the resin bond C is formed by the electrolytic action as shown in FIG. Elutes and ionizes,
Chip pockets are formed on the ground surface 2a, leaving only the abrasive grains B and the resin C (FIG. 4B), and do not require the formation of an oxide film (see FIG. 4C) as in ELID grinding. .

Accordingly, a sufficient amount of the abrasive grains protruding from the grinding surface 2a is obtained, and the abrasive grains are held elastically by the elasticity of the resin itself, thereby impairing the grinding efficiency which is a feature of the centerless grinding. Also, no scratch occurs on the surface of the workpiece W, and high grinding accuracy (surface roughness) can be secured.

Further, since no oxide film is formed on the grinding surface 2a, even with the wide grinding wheel 2 as in the illustrated embodiment,
Electrolytic dressing can be performed with low power consumption, and the electrolytic dressing time is significantly reduced as compared with the conventional ELID grinding (see FIG. 4).

Embodiment 2 A precision grinding apparatus according to this embodiment is shown in FIG. 3. Specifically, in addition to the electrolytic dressing apparatus 1 according to Embodiment 1, a centerless grinding apparatus provided with a discharge truing apparatus 20 is also provided. On the board, the same reference numerals as those in the first embodiment denote the same components or components.

The discharge truing device 20 has a discharge truing electrode 21 disposed on the opposite side of the adjusting wheel 3 with respect to the grinding wheel 2. In other words, the discharge truing device 2
Numeral 0 is disposed on the upstream side in the rotation direction of the grinding wheel 2 with respect to the electrolytic dressing apparatus 1.

The discharge truing electrode 21 is specifically in the shape of a small disk having a narrow width, and its outer peripheral surface portion is
The cylindrical electrode surface 21a is opposed to the grinding surface 2a of the grinding wheel 2.

Although not specifically shown, the discharge truing electrode 21 is rotatably supported on a discharge truing electrode base via a discharge truing electrode shaft arranged in parallel with the grinding wheel shaft 5 and has a power source. It is linked to a rotary drive source via a transmission mechanism. As a result, the discharge truing electrode 21 is rotationally driven in a state where the electrode surface 21a is opposed to the grinding surface 2a of the grinding wheel 2 so as to be parallel to the grinding surface 2a.

The discharge truing electrode 21 is slidable in a direction (arrow direction) parallel to the grinding wheel shaft 5 of the grinding wheel 2 and is linked to a slide drive source to grind the grinding wheel 2. The traverse moves in the direction of the grinding wheel axis 5 along the surface 2a.

The discharge truing electrode 21 is electrically connected to the power supply 11 via a discharge / electrolysis switching unit (switching operation unit) 25 for electrode switching together with the programmable electrode switching unit 18 of the electrolytic dressing electrode 15. ing. Specifically, the discharge truing electrode 21
Is electrically connected to the discharge / electrolysis switching unit 25 via the power supply 22, and the discharge / electrolysis switching unit 25 is electrically connected to the (−) pole of the power supply 7 to discharge the (−) pole. It is a truing electrode. Therefore, the discharge
By manually or automatically switching the electrolytic switching unit 25, the discharge truing electrode 21 and the electrolytic dressing electrode 15 are selectively switched.

In the centerless grinding machine configured as described above, discharge truing is performed by the discharge truing device 20 prior to the electrolytic dressing in the first embodiment.

This discharge truing is performed at any time during the grinding process or while the grinding process is stopped, depending on the properties of the grinding surface 2a of the grinding wheel 2. Specifically, the discharge truing electrode 21 is applied to the grinding surface 2a. Traverse while rotating, grinding wheel 2 and discharge truing electrode 2
1, a DC current is applied to the ground surface 2a.
Is melted and removed by the discharge action to form chip pockets, and the protrusion amounts of the abrasive grains on the grinding surface 2a are made uniform.

In this case, in order to prevent cooling water or the like from entering the discharge region between the electrode surface 21a and the grinding surface 2a, cooling air is injected from a cooling air nozzle (not shown) into this discharge region.

Subsequently, switching is performed by the discharge / electrolysis switching unit 25 so that the electrolytic dressing electrode 15 is operated from the discharge truing electrode 21, and the electrolytic dressing by the electrolytic dressing apparatus 1 is executed in-process. The specific mechanism of the electrolytic dressing is the same as that described in the first embodiment.

Thus, as described above, the discharge truing is performed prior to the electrolytic dressing, in other words, the grinding surface 2a of the grinding wheel 2 is ground from the shape formed by the discharge truing, and at the same time, the electrolytic dressing is started. By executing in a process, in addition to the effect of the first embodiment described above, the effect of discharge truing is exhibited as a synergistic effect, and centerless grinding with higher grinding efficiency and higher grinding accuracy can be realized. Other configurations and operations are the same as those of the first embodiment.

The above-described embodiment merely shows a preferred embodiment of the present invention, and the present invention is not limited to this, and various design changes can be made within the scope.

For example, although the illustrated embodiment is a centerless grinding machine, the present invention can be applied to grinding machines of other grinding methods such as a surface grinding machine and a cylindrical grinding machine.

[0054]

As described in detail above, according to the present invention,
In ultra-precision grinding using electrolytic dressing,
As the conductive grindstone, a conductive resin bond grindstone in which abrasive grains are bonded by a conductive resin bond containing a conductive substance is used, and the conductive resin bond grindstone is used during grinding of a workpiece with the conductive resin bond grindstone. Electrolytic dressing is applied to the grindstone surface, so while maintaining the sharpness and elasticity of the grindstone surface, satisfying the profile accuracy of the grindstone surface required for precision grinding,
High finishing accuracy can be obtained, and the dressing cycle time and power consumption can be reduced.

Specifically, since a metal material such as copper or tungsten is used as the conductive material contained in the resin bond, the following effects can be obtained.

(1) Only the conductive material (metal component) in the resin bond is dissolved by the electrolytic action, and only the abrasive grains and the resin remain on the grindstone surface. Therefore, it is necessary to form an oxide film as in ELID grinding. do not do. For this reason, a sufficient protrusion amount of the abrasive grains can be obtained, and the elasticity of the resin itself has elasticity in the holding state of the abrasive grains. Thus, no scratch is generated on the workpiece surface.

As a result, there are two necessary conditions for improving the grinding efficiency and improving the grinding accuracy (surface roughness) (the amount of protrusion of the abrasive grains is sufficient, the bond holding the abrasive grains (including the oxide film). ) Is satisfied at the same time.

(2) Since it is not necessary to form an oxide film, it is possible to perform electrolytic dressing with power saving even with a wide whetstone.
The electrolytic dressing time is also shortened as compared with the case of ELID grinding, so that the running cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a schematic configuration of a centerless grinding machine according to a first embodiment of the present invention.

FIG. 2 is an enlarged schematic view showing an electrolytic dressing step of the electrolytic dressing apparatus in the centerless grinding machine.

FIG. 3 is a perspective view showing a schematic configuration of a centerless grinding machine according to a second embodiment of the present invention.

FIG. 4 is an enlarged schematic view corresponding to FIG. 2, showing an electrolytic dressing step in conventional ELID grinding.

[Explanation of symbols]

Reference Signs List 1 electrolytic dressing device 2 grinding wheel 2a grinding surface of grinding wheel (grinding wheel surface) 3 adjusting wheel 4 blade 10 power supply 11 power supply 15 dressing electrode 15a ring electrode surface of dressing electrode 16 small electrode 20 discharge truing device 21 discharge truing electrode 21a discharge Cylindrical electrode surface of truing electrode 22 Feeder 25 Discharge / electrolysis switching unit (switching operation unit) A Conductive substance in resin bond B Abrasive C Resin in resin bond W Workpiece

Claims (5)

[Claims] 1. A grinding method using a conductive grindstone utilizing electrolytic dressing, wherein a conductive resin bond grindstone having abrasive grains bonded by a conductive resin bond is used as the conductive grindstone. An ultra-precision grinding method, wherein electrolytic dressing is performed on a grindstone surface of a conductive resin-bonded grindstone during grinding of a workpiece with the resin-bonded grindstone. 2. The ultra-precision grinding method according to claim 1, wherein discharge truing is performed prior to said electrolytic dressing. 3. The ultra-precision grinding method according to claim 2, wherein the discharge truing is performed while grinding of the conductive grindstone is stopped. 4. The ultra-precision grinding method according to claim 2, wherein the discharge truing is performed during the grinding of the conductive grindstone. 5. A centerless type grinding apparatus provided with a grinding wheel using a conductive grinding wheel having abrasive grains bonded by a conductive bonding material, wherein the conductive grinding wheel constituting the grinding wheel is a conductive resin. An ultra-precision grinding apparatus characterized in that abrasive grains are bonded by a bond and an electrolytic dressing electrode is provided to face the grinding wheel surface of the grinding wheel.