JPH08108364A - Grinding work method - Google Patents

Abstract

PURPOSE: To provide a grinding work method by which a work of a hard and fragile material having high hardness can be ground with high efficiency and high accuracy. CONSTITUTION: In a grinding work method to grind a rotating work 1 by coming into contact with grinding wheels 8 and 11 while dressing the rotating grinding wheels 8 and 11 by an electrolytic in-process dressing method, the work 1 is ground while maintaining load electric power of a driving motor 10 to drive the grinding wheels 8 and 11 in rotation in a prescribed value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grinding method for mirror-grinding a work made of a hard and brittle material having a high hardness such as fine ceramics, and more specifically to a mirror grinding while dressing a conductive grindstone by an electrolytic in-process dressing method. Grinding method.

[0002]

2. Description of the Related Art Conventionally, as means for mirror-polishing a hard and brittle material such as ferrite by an electrolytic in-process dressing method while dressing a conductive grindstone, JP-A-4-11 has been proposed.
The technology disclosed in Japanese Patent No. 1771 is disclosed. FIG. 6 is a schematic side view of a main part of the above-described conventional mirror surface grinding processing apparatus.

As shown in FIG. 6, this mirror-surface grinding machine comprises a high-precision air spindle 21 and a cup-shaped grindstone 22 attached to the air spindle 21.
This is a mirror surface grinding processing device that employs a so-called vertical grinding method in which the spindle axis of is oriented horizontally and the grinding surface of the cup-shaped grindstone 22 is arranged in the vertical direction. In this processing apparatus, an air spindle 21 having a high rotational accuracy is used as a spindle for rotationally driving the cup-shaped grindstone 22, and a plurality of balance adjusting screws 24 are provided on a pressing flange 23 of the cup-shaped grindstone 22. The dynamic rigidity of the whole is increased, and as a result, the rotation accuracy of the spindle shaft is N.M. R. R. = 0.05 μm or less.

On the other hand, on the tip surface of the cup-shaped grindstone 22, there is a conductive grindstone 25 in which ultrafine abrasive grains (average particle size 1 to 2 μm) such as diamond or boron nitride (CBN) are firmly held by metal bond. The ring-shaped conductive grindstone 25 is configured to mirror-finish a workpiece 26 such as ferrite, glass, ceramics, or silicon.

The entire cup-shaped grindstone 22 is also made of a conductive material, and a conductive slip ring 27 is fitted and disposed at the base end portion thereof and connected to one electrode of an electrolytic power source 28. The carbon brushes 29 are provided so as to come into contact with each other. An electrolytic electrode 31 formed on an insulator 30 is provided at a position facing the conductive grindstone 25 attached to the cup-shaped grindstone 22, and the other electrode of the electrolytic power source 28 is connected to the electrolytic electrode 31. This insulator 30
A coolant supply port 32 for ejecting a weakly conductive coolant toward the conductive grindstone 25 is formed in the center of the electrolytic electrode 31.
The coolant is supplied between the 1 and the conductive grindstone 25. Therefore, a weak conductive coolant is jetted and supplied from the supply port 32 between the conductive grindstone 25 and the electrolytic electrode 31, and the conductive grindstone 25 is supplied from the electrolytic power source 28.
By applying a voltage to the electrolytic electrode 31, so-called electrolytic dressing is performed.

In the mirror surface processing method using this mirror surface processing apparatus, the air spindle 21 which can be moved back and forth in the direction of arrow X in FIG. 6 is advanced to bring the ground surface of the conductive grindstone 25 into contact with the workpiece 26, While the weakly conductive coolant is being supplied at the portions A and B, the workpiece 26 is indicated by the arrow Y.
Oscillate in the direction to perform mirror surface grinding. At this time, a voltage is applied between the conductive grindstone 25 and the electrolytic electrode 31 from the electrolytic power source 28 through the carbon brush 29 and the slip ring 27, and the coolant is ejected from the supply port 32 provided in the electrolytic electrode 31. The metal bond on the surface of the conductive grindstone 25 is eluted by electrolysis. As a result, the abrasive grains are projected onto the ground surface of the conductive grindstone 25, and at the same time, the clogging caused by the grinding powder or the like is removed. In this way, by rotating the slightly projected abrasive grains with high accuracy, the cutting edge of the ultrafine abrasive grains works effectively, and it becomes possible to perform highly precise mirror-surface grinding processing as compared with the conventional device. .

[0007]

However, the above-mentioned conventional technique has the following problems. (1) Since the work is oscillated in the direction of the arrow Y in FIG. 6 during the grinding process, the contact pressure between the grinding wheel and the work during the process changes, which adversely affects the shape accuracy of the machined surface of the work. There is a limit to accuracy. (2) In addition, even if the rocking in the direction of the arrow Y is stopped, when performing grinding of high hardness fine ceramics, the load power of the grindstone shaft motor becomes unstable, so stable machining is continued. It is difficult to do so, and the machining shape accuracy of the work is not stable.

The above problems will be described in detail.
In the case of the grinding method as in the prior art, the cutting speed and the cutting amount of the grindstone are preset as the processing conditions. However, in order to grind a high hardness fine ceramics work using a conductive grindstone made of ultrafine abrasive grains, it is impossible to process unless the cutting speed is set to an extremely low speed. However, in the electrolytic in-process dressing method, when the cutting speed is set to an extremely low speed, peeling of the oxide film due to contact between the work and the oxide film on the grinding wheel processing surface does not easily occur, and the film thickness of the oxide film increases. The load power of the grindstone shaft motor tends to change due to the change in the processing pressure due to the change. FIG. 7 is a table showing the relationship between the load power of the grinding wheel spindle motor and the elapsed time when the cutting operation of the grinding wheel is stopped at the contact position between the work and the grinding wheel. Figure 7
From the above, it can be seen that the load power of the grindstone shaft motor gradually increases from the time of contact between the workpiece and the cup-shaped grinding wheel (at the start of processing) to 50 minutes, and thereafter gradually decreases.

FIG. 8 is a table showing the relationship between the load power of the grindstone shaft motor and the work shape accuracy of the workpiece. From this, it is understood that the work shape accuracy of the workpiece becomes higher as the load power of the grindstone shaft becomes lower. Further, the grinding efficiency is also affected by the load power of the grindstone shaft motor. Figure 9 shows 3 high hardness CBN
It is a chart which shows the relationship between the load electric power of a grindstone axis motor at the time of grinding processing for 0 minute, and the amount of grinding removal. From this, it is understood that the higher the load power of the grindstone shaft motor, the higher the grinding efficiency.

The present invention has been made in view of the above conventional problems, and an object of the invention according to claim 1, 2 or 3 is as follows.
It is an object of the present invention to provide a grinding method that can perform a work of a hard and brittle material having a high hardness with high efficiency and high accuracy.

[0011]

In order to solve the above problems, the invention according to claim 1, 2 or 3 is directed to a rotating work while dressing a rotating grinding wheel by an electrolytic in-process dressing method. In the grinding method of abutting and grinding the grinding grindstone, the work is ground while the load power of a drive motor that rotationally drives the grinding grindstone is maintained at a predetermined value.

[0012]

In the operation of the invention according to claim 1, 2 or 3,
By maintaining the load power of the drive motor that rotationally drives the grinding wheel during the grinding process at a predetermined value, the shape accuracy of the ground surface of the work and the grinding removal amount of the work are maintained at desired values. In the operation of the invention according to claim 2, in addition to the above operation, the predetermined value of the load power of the drive motor for rotationally driving the grinding wheel is divided into a relatively high value and a low value, and the grinding process is performed in two stages. By doing so, the grinding efficiency of the work is improved. In the operation of the invention according to claim 3, in addition to the above operation, the load power for each step of the cutting operation is detected and compared with a set value, and when the value exceeds the set value, the step is returned by one step to rotate the grinding wheel. The load power of the driving motor to be driven is maintained at a predetermined value.

[0013]

Embodiment 1 FIGS. 1 to 3 show a first embodiment, FIG. 1 is a schematic view of a grinding apparatus used in a grinding method, FIG. 2 is a flowchart of the grinding method, and FIG. It is a figure which shows the screen of the interferometer showing processed shape accuracy.

The grinding apparatus used for the grinding method basically uses the same electrolytic in-process dressing method as in the prior art. In FIG. 1, the grinding device is roughly divided into a work shaft 19 and a grindstone shaft 20.
On the work shaft 19, a work 1 made of CBN is held by a work chuck 2, a work spindle 3 and a pulley 4,
A work shaft motor 7 arranged via a belt 5 and a belt 6 is configured to be rotationally driven around the shaft center A of the work spindle 3. In the grindstone shaft 20, the cup-shaped grinding wheel 8 is rotatably held by the grindstone shaft motor 10 provided at the rear portion of the grindstone shaft spindle 9 about the axis B of the grindstone shaft spindle 9 as a rotation center, and a drive not shown Depending on the device, it is movable in the direction of arrow X.

The machined surface 11 of the cup-type grinding wheel 8 contains # 600 diamond powder in order to retain conductivity.
Specially blended with metal powders such as copper, tin, iron, etc., and joined by a heat-treated sintered alloy. Reference numeral 12 denotes a negative electrode for performing the electrolytic in-process dressing method, which is made of copper or carbon graphite and is arranged so as to face the processing surface 11 of the cup-type grinding wheel 8. Reference numeral 18 denotes a plus electrode, which is slidably mounted on the rotary shaft of the grindstone shaft motor 10 and is electrically connected to the machined surface 11 of the cup-shaped grinding stone 8 via the central axis of the grindstone spindle 9. By applying a DC pulse voltage between the negative electrode 12 and the positive electrode 18 by the power supply device 13, the electrolytic in-process dressing method is possible.

Reference numeral 14 denotes a nozzle for supplying the weakly conductive coolant 15 by a coolant supply device (not shown). A power meter 16 is connected to the grindstone shaft motor 10, and the value of the load power of the grindstone shaft motor 10 detected there is transmitted to the controller 17.

Next, a grinding method using the above grinding apparatus will be described. First, the cup-type grinding wheel 8 is rotated while supplying the weak electric coolant 15 between the negative electrode 12 and the processed surface 11 of the cup-type grinding wheel 8. Next, electrolytic dressing is performed by applying a DC pulse voltage between the positive electrode 18 and the negative electrode 12 by the power supply device 13.

As shown in FIG. 2, when the grinding process is started, a preset machining surface 11 of the cup-shaped grinding wheel 8 is set.
The cup-shaped grinding wheel 8 moves in the direction of the arrow X to the contact position between the workpiece 1 and the workpiece 1, and the timer for measuring the elapsed processing time in the controller 17 is started. Next, cutting of the cup-shaped grinding wheel 8 into the work 1 is started at the set cutting speed (5 μm / min), and the grinding wheel shaft motor 10 is operated at each step of the cutting operation (cutting amount 0.1 μm).
The load power of is detected. When the detected load power is equal to or less than a preset value (0.7 kW), the cup-shaped grinding wheel 8 is continuously cut, and when the load power exceeds the preset value, the cup-shaped grinding wheel 8 is cut. Is work 1
Move 1 step away from (movement amount 0.1μ
m, moving speed 5 μm / min). After repeating these operations until the set machining time (30 min) is reached,
The cup-shaped grinding wheel 8 is detached from the work 1 and the grinding process is completed.

In this embodiment, when the thickness of the oxide film on the machined surface of the cup-shaped grinding wheel increased during machining,
When the cup grinding wheel moves backward one step at a time and conversely the film thickness decreases, the cup grinding wheel moves forward.
Grinding is performed while keeping the load power of the grindstone shaft motor constant at a preset value.

According to this embodiment, since the load power of the grindstone shaft motor during grinding is always maintained at a constant value (0.7 kW), as shown in the screen of the interferometer of FIG. A very good work shape accuracy of 0.4 μm can be obtained. Further, the grinding removal efficiency is as shown in FIG.
It changes depending on the load power of the grindstone shaft motor, but since the load power is maintained at 0.7 kW, it will be 0.
A grinding removal amount of 8 μm can be stably obtained.

In the present embodiment, it is possible to handle all kinds of work by changing the mesh of the grinding wheel, the grinding wheel moving speed, the grinding wheel moving amount, etc. according to the working characteristics of the work.

[0022]

Second Embodiment FIGS. 4 to 5 show a second embodiment, FIG. 4 is a flow chart of a grinding process, and FIG. 5 is a diagram showing a screen of an interferometer showing a processing shape accuracy of a ground work. The grinding apparatus used in this embodiment is the same as that shown in FIG.
Since the same one is used, the description is omitted.

In the grinding method of this embodiment, the number of processing steps is one.
It is divided into two processes, a secondary process (coarse grinding process) and a secondary process (finish grinding process). In the primary processing, the processing is the same as that of the first embodiment, or is set such that the load power (0.8 kW) of the grindstone shaft motor 10 is set higher, and after a predetermined processing time (20 min) has elapsed. In the secondary processing, the cup-shaped grinding wheel 8 is retracted away from the work 1 to a position where the load power (0.5 kW) of the grindstone shaft motor 10 is once low, and the processing is continued while maintaining the low load power, When the set time (primary machining + secondary machining = 30 minutes) has elapsed, the machining ends.

The grinding method will be described in detail with reference to FIG. When the processing is started, the processing surface 11 of the cup-type grinding wheel 8 is fed to the contact position with the work 1, and the timer for measuring the processing elapsed time is started. Next, the cutting of the cup-shaped grinding wheel 8 to the work 1 is started at the set cutting speed (5 μm / min), and the load power of the grinding wheel spindle motor 10 is increased at each step of the cutting operation (cutting amount 0.1 μm). To be detected. When the load power is less than the preset value (0.8 kW), the cup-shaped grinding wheel 8 is continuously cut, and when the load power exceeds the preset value, the cup-shaped grinding wheel 8 works. It moves one step in the direction away from 1 (moving amount 0.1 μm, moving speed 5 μm / min). The primary processing is performed by repeating these operations until the set time (20 min) has elapsed.

When the machining time set in the primary machining has elapsed, the cup-shaped grinding wheel 8 is moved away from the work 1 until the load power of the wheel spindle motor 10 decreases to a preset value (0.5 kW). Move to. After that, while detecting the load power of the grindstone shaft motor 10, if the load power is less than or equal to a preset value, the cup-type grinding wheel 8 is the work 1
1 step is moved in the cutting direction (moving amount 0.1 μm, moving speed 5 μm / min). When the load power exceeds a preset value, the cup-shaped grinding wheel 8 moves one step in the direction away from the work 1 (moving amount 0.1 μm, moving speed 5 μm / min). After performing the secondary processing by repeating these operations until the processing elapsed time reaches the predetermined time (30 min), the cup-shaped grinding wheel 8 is detached from the work 1 and the grinding processing is completed.

As a result, similarly to the first embodiment, in response to the variation in the thickness of the oxide film on the machined surface of the cup-type grinding wheel,
By moving the cup-type grinding wheel forward and backward, grinding is performed while maintaining the load power of the wheel shaft motor at a preset value. Further, in the first machining, machining is performed while maintaining a high load power of the grindstone shaft motor, and in the next machining, machining is performed while maintaining a low load power of the grindstone shaft motor.

In the present embodiment, similarly to the first embodiment, it is possible to stably grind a workpiece having a high hardness, and in the first grinding, rough grinding is carried out and a high load power (0.8k) of the wheel spindle motor is used.
Highly efficient processing is performed under W), and in the next processing, highly accurate processing is performed under low load power (0.5 kW) of the grindstone shaft motor. As a result, a grinding amount of about 0.8 μm can be stably obtained by processing for 30 minutes as in the first embodiment, and at the same time, as shown in the screen of the interferometer of FIG.
It is possible to obtain a processed surface with a higher accuracy of 3 μm.

In the grinding method of the present invention, in both the first and second embodiments, a cup-type grinding wheel is used to grind a work having a flat surface to be processed. The present invention is not limited to the grinding wheel and the work, and a spherical grinding wheel can be used to grind a workpiece having a spherical work surface. Further, it goes without saying that the grinding method of the present invention can be applied to a work having an aspherical surface or a conical surface.

[0029]

According to the inventions of claims 1 to 3, it is possible to grind a work of a hard and brittle material such as high hardness fine ceramics stably, highly efficiently and highly accurately. . According to the invention of claim 2, in addition to the above effects, it is possible to perform the grinding process with higher efficiency. According to the invention of claim 3, in addition to the above effects, more stable grinding can be performed.

[Brief description of drawings]

FIG. 1 is a schematic view of a grinding device used in a grinding method of a first embodiment.

FIG. 2 is a flowchart of a grinding method according to the first embodiment.

FIG. 3 is a view showing a screen of an interferometer showing a processed shape accuracy of a work ground by the grinding method of the first embodiment.

FIG. 4 is a flowchart of a grinding method according to a second embodiment.

FIG. 5 is a diagram showing a screen of an interferometer showing a processing shape accuracy of a work ground by the grinding method of the second embodiment.

FIG. 6 is a schematic side view of a main part of a prior art mirror surface grinding apparatus.

FIG. 7 is a table showing the relationship between the load power of the grinding wheel shaft motor of the grinding device used in the prior art or the present invention and the elapsed time.

FIG. 8 is a chart showing the relationship between the load power of the grindstone shaft motor of the grinding device used in the prior art or the present invention and the work shape accuracy of the workpiece.

FIG. 9 is a table showing a relationship between load power and a grinding removal amount of a grindstone shaft motor of a grinding device used in the prior art or the present invention.

[Explanation of symbols]

 1 Work 2 Work Chuck 3 Work Spindle 7 Work Axis Motor 8 Cup Type Grinding Wheel 9 Grindstone Axis Spindle 10 Grindstone Axis Motor 11 Machining Surface 12 Negative Electrode 13 Power Supply 16 Power Meter 17 Controller 18 Positive Electrode 19 Work Axis 20 Grindstone Axis

Claims (3)

[Claims] 1. A grinding motor in which a rotating grinding wheel is dressed by an electrolytic in-process dressing method, and the grinding workpiece is brought into contact with a rotating workpiece to grind it, and a drive motor for rotationally driving the grinding wheel. The grinding method, wherein the work is ground while the load power of No. 1 is maintained at a predetermined value. 2. A predetermined value of the load power of a drive motor for rotating the grinding wheel is maintained at a relatively high value and then maintained at a relatively low value. The grinding method described. 3. A method of maintaining the load power of a drive motor for rotating the grinding wheel at a predetermined value is one of the cutting operations.
The grinding method according to claim 1 or 2, wherein the load power for each step is detected and compared with a set value, and if the value exceeds the set value, the step is returned by one step.