JP2000176832A - Grinding method - Google Patents

Abstract

(57) [Problem] To improve the grinding efficiency by using a simple control system, reducing the grinding time without lowering the processing accuracy. A load on abrasive grains is obtained in advance by experiments and the like, a cutting speed is set so that the load is constant with respect to a cutting amount, and the cutting amount is divided.
By inserting a cutting pause time between the divided cutting amounts, the feed speed to the work is controlled such that the load current value at the time of cutting into the work becomes substantially constant within a close range within the allowable load limit 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 capable of efficiently grinding a work in a short time by a grinding means such as a grindstone.

[0002]

2. Description of the Related Art Conventionally, for example, a processing method of rotating a grindstone at a high speed to grind a workpiece into a desired shape has been used.

In the grinding method according to the prior art, for example, the amount of cut into a work is gradually reduced in a rough grinding step, a finish grinding step, etc., so that both improvement in grinding efficiency and high processing accuracy can be achieved. I'm trying.

[0004]

However, in the above-described grinding method according to the prior art, for example, when grinding the inner surface of the work with respect to the hole, the cutting depth increases because the rigidity of the grinding wheel shaft system is small. As a result, bending occurs in the grinding wheel shaft system. Therefore, a residual (an uncut amount) is generated between a preset value for the inner surface grinding of the workpiece and an actually ground removal amount.

Therefore, in the grinding method according to the prior art, the cutting operation is temporarily stopped in the final step of the grinding process.
After adjusting the amount of deflection of the grinding wheel shaft system to be zero, or performing a minute cut corresponding to the uncut amount, or by increasing the spark-out time, to remove the uncut amount for the workpiece. I have.

[0006] For this reason, the conventional grinding method has a disadvantage that the amount of cut per unit time cannot be increased. Further, if the cutting efficiency per unit time is increased to improve the grinding efficiency, a complicated control system is required, and there is a disadvantage that a large cost is required for capital investment.

For example, Japanese Unexamined Patent Publication (Kokai) No. 58-171257 discloses a method in which both the cutting speed and the number of revolutions of the work are controlled so that the processing conditions at the time of rough grinding and at the time of finish grinding become appropriate values. Although a grinding control method that performs efficient and good surface roughness grinding is disclosed, a complicated control process and control system are required,
There is a problem that a large cost is required as in the above-described conventional method.

The present invention has been made in consideration of the above-mentioned problems, and it is possible to use a simple control system, shorten the grinding time without lowering the processing accuracy, and improve the grinding efficiency. An object of the present invention is to provide a simple grinding method.

[0009]

In order to achieve the above object, the present invention provides a method for grinding a workpiece with a grindstone, the method comprising: moving a grinding surface formed on an outer periphery of the grindstone; The load on the abrasive grains and the allowable limit value are calculated in advance from the diameter of the work and the rotation speed of the work,
Based on the calculated data, the cutting speed is set so that the load is substantially constant with respect to the cutting amount, the step of grinding the workpiece according to the set conditions, and the load current value of the spindle are measured. The feed speed of the grindstone is increased until the load current value reaches the allowable load limit value, and when the load current value reaches the allowable load limit value, the rotation speed of the work is set so that the load current value becomes the minimum. And further increasing the feed speed of the grindstone, dividing the cutting amount into a plurality when the load current value exceeds the allowable load limit value, and inserting a cutting pause time between the divided unit cutting amounts. And, repeating the division of the individual unit cut amount and the insertion of the cut pause time until the load current value decreases,
Controlling the feed rate such that the load current value at the time of cutting is substantially constant within the allowable load limit value and in a range close to the allowable load limit value, and the individual unit cut amount is set to a predetermined value. And stopping the division when the following condition is satisfied.

In this case, for each of the divided unit cut amounts, the feed rate is increased until the load current value reaches the allowable load limit value, and the division is repeated until the unit cut amount becomes equal to or less than the fine polishing amount. . The number of times of inching can be reduced by gradually increasing the cutting pause time inserted between the plurality of divided unit cutting amounts.

According to the present invention, the load on the abrasive grains is determined in advance, the cutting speed is set so that the load is constant with respect to the cutting amount, and the load current value at the time of cutting into the work falls within the allowable load limit value. Is controlled to be substantially constant in a range close to the workpiece. Therefore, the grinding time can be shortened by performing the grinding process on the work while maintaining the state in which the grinding efficiency for the work is maximized.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of a grinding method according to the present invention will be described below in detail with reference to the accompanying drawings.

As shown in FIG. 1, the grinding device 10 includes a table 12 formed in a substantially rectangular shape, and an arrow X direction (feed direction) and / or an arrow Y direction ( A spindle 14 provided to be displaceable along the cutting direction) and a grindstone 16 mounted on a rotating shaft of the spindle 14.

A rotational driving force of a rotary drive source (not shown) is transmitted to the spindle 14, and a grindstone 16 mounted on the rotary shaft of the spindle 14 is driven by the rotary drive source under the action of the rotary drive source. It is provided so as to rotate at high speed integrally with the shaft.

The grindstone 16 is provided so as to be displaceable integrally with the spindle 14 in the feed direction of arrow X under the driving action of an unillustrated actuator.
4 is provided so as to be displaceable along the arrow Y direction, which is the cutting direction, integrally with 4. Therefore, the feed speed and the cutting speed of the grinding wheel, which will be described later, are performed by controlling the displacement speed of the actuator.

The grinding device 10 has a main shaft 18 fixed to the table 12 and a work 22 detachably held via a chuck member 20 connected to the main shaft 18. In the present embodiment, an example in which an outer cup forming a constant velocity joint is used as the workpiece 22 and the inner wall surface 26 of the cup portion 24 of the outer cup is ground will be described below as an example.

As shown in FIG. 2, a rotational driving force of a rotary driving source (not shown) is transmitted to the main shaft 18, and a work 22 held on a chuck member 20 is driven by a predetermined action under the driving action of the rotary driving source. It is provided rotatably in the direction.

The grinding apparatus 10 for carrying out the grinding method according to the present embodiment is basically constructed as described above. Next, the operation and effect of the grinding apparatus will be described.

First, before grinding the inner wall surface 26 of the cup portion 24 of the work 22 with the grindstone 16, data on the grindstone 16 mounted on the spindle 14 is calculated. This data includes the maximum peripheral speed of the grindstone 16, the diameter of the grindstone 16, the diameter of the work 22, and the load on the abrasive grains obtained based on the rotation speed of the work 22, and the allowable load limit value. Calculated from the data. Based on the data, when grinding the work 22, so that the load on the grindstone 16 is kept constant,
The cutting speed in the arrow Y direction is set in advance.
Note that the “maximum peripheral speed” refers to the moving speed of the grinding surface formed on the outer periphery of the grindstone 16.

Next, a rotary drive source (not shown) is driven,
The rotational driving force is transmitted to the spindle 14 to rotate the grindstone 16 in a predetermined direction, and the work 22 connected to the main shaft 18 via the chuck member 20 is rotated. As described above, in a state where the work 22 and the grindstone 16 are rotated together, the actuator (not shown) is driven to displace the spindle 14 in the direction of the arrow X, and the work 22 and the grindstone 1 are rotated.
6 by bringing the grinding surface of the grindstone 16 into contact with the inner wall surface 26 of the cup portion 24 of the work 22.
The grinding process is started (Step S1).

Hereinafter, the grinding method according to the present embodiment will be described with reference to the flowcharts shown in FIGS.

When the grinding surface of the grindstone 16 is in contact with the inner wall surface 26 of the cup portion 24 of the work 22, the work 22 is ground at a predetermined cutting speed so as to keep the load on the abrasive grains of the grindstone 16 constant. Then, the load current value (load level) of the spindle at the time of the grinding is measured by a current measuring means (not shown) (step S2). FIG. 5 shows a load current curve of the spindle 18 measured by a current measuring means (not shown) under such conditions. The grinding process is divided into a rough polishing region, a fine polishing region, and a spark-out region.

Subsequently, the load current value of the main shaft 18 is increased by urging an actuator (not shown) to gradually increase the feed speed of the grindstone 16 in the direction of the arrow Y (step S3) (see FIG. 6). . When the load current value of the spindle 18 reaches the allowable load limit value (step S
In 4), the rotation speed of the work 22 is adjusted, and the rotation speed of the work 22 is set so that the load current value of the main shaft 18 is minimized (step S5).

For example, the rotational speed of the work 22 is set to about 10 to 2
The rotation speed is set so that the load current value becomes minimum while increasing or decreasing the rotation speed in a range of 0%. By setting the number of revolutions of the work 22 so that the load current is minimized, the load current curve is reduced overall and is separated from the allowable load limit value.

With the rotational speed of the workpiece 22 set in step S5 fixed, the feed speed of the grindstone 16 in the direction of arrow Y is further increased under the urging action of an actuator (not shown) (step S6). in this case,
The feed speed of the grindstone 16 is increased until the load current value of the spindle 18 reaches the allowable load limit value.

When the load current value of the spindle 18 exceeds the allowable load limit value (step S7), the preset cutting amount for the work 22 is divided into two (step S8), and is shown in FIG. As described above, the cutting is paused between the divided first and second cutting amounts, and the grinding process is started again (Step S).
9). This cutting pause time is performed by, for example, deactivating an actuator (not shown) to stop the displacement of the grindstone 16 in the arrow Y direction. Divided first
By inserting the cut-off time between the cut amount and the second cut amount, the load current curve is reduced overall and is separated from the allowable load limit value. When the cutting pause time is not included, a load current curve in which the load current value exceeds the allowable load limit value is maintained for a predetermined time, as shown by a broken line in FIG.

In a state where a cutting pause time is provided between the divided first cutting amount and the second cutting amount, the feed speed is further increased and the load current value of the main shaft 18 is measured. In this case, when the measured load current value has not decreased, the cut amount is divided into three, and the cut amount is divided between the first cut amount and the second cut amount, and between the second cut amount and the second cut amount. A cutting pause time is inserted between the three cutting amounts.

With respect to each of the divided unit cut amounts, the feed speed is further increased (step S1).
0), as shown in FIG. 8, the feed speed is increased until the load current value of the spindle 18 reaches the allowable load limit value (step S11). For example, when the cut amount is divided into two, the feed speed is increased for the divided first cut amount, and the feed speed is also increased for the second cut amount after the cut pause time has elapsed.

Further, the feed rate is increased until the load current value of the spindle 18 at the divided first and second cut amounts reaches the allowable load limit value, and the load current value reaches the allowable load limit value. When the first
The cutting amount is divided into a third cutting amount and a fourth cutting amount, and the second cutting amount is divided into a fifth cutting amount and a sixth cutting amount. The feed speed at the divided third to sixth cut amounts is increased, and thereafter, the division and the insertion of the cut pause time are similarly repeated (see FIG. 9).

It is to be noted that by increasing the cutting pause time inserted between each of the divided unit cutting amounts,
It is possible to reduce the number of inchings that are displaced stepwise (see FIG. 10).

Steps S8 to S11 are repeated until the unit cut amount of the rough grinding region divided into a plurality of pieces becomes equal to or smaller than the fine grinding amount, and the unit cut amount of the rough grinding region is precisely adjusted. When the amount becomes less than the grinding amount, the division for the cutting amount is stopped, and the grinding is completed (steps S11 and S12).

If the slope (increase rate or increase acceleration) of the load current curve exceeds the set value instead of Steps S8 and S9, the load current value exceeds the allowable load limit value. May be divided, a cutting pause time is inserted between the divided cutting amounts, and the load current value at which the cutting pause time is inserted may be measured.

In the grinding method according to the present embodiment, the load on the abrasive grains is determined in advance by experiments and the like, and the cutting speed is set so that the load is constant with respect to the cutting amount. The feed speed to the work 22 is controlled so that the load current value is substantially constant in a close range within the allowable load limit value.

Therefore, in the grinding method according to the present embodiment, the grinding accuracy is degraded by performing the grinding process on the work 22 while maintaining the state where the grinding efficiency on the work 22 is maximized. And the grinding time can be reduced. As a result, the cutting amount per unit time can be increased, and the grinding efficiency can be improved.

Further, in the grinding method according to the present embodiment, grinding can be performed by a simple control system without requiring ancillary equipment such as an expensive control system, and the manufacturing cost can be reduced. Becomes possible.

[0036]

According to the present invention, the following effects can be obtained.

That is, by performing the grinding process on the work while maintaining the state where the grinding efficiency for the work is maximized, the grinding time can be reduced without deteriorating the processing accuracy. As a result, the cutting amount per unit time can be increased, and the grinding efficiency can be improved.

Further, according to the present invention, since the grinding can be performed by a simple control system without requiring any additional equipment such as an expensive control system, the manufacturing cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a plan configuration diagram of a grinding apparatus that performs a grinding method according to an embodiment of the present invention.

FIG. 2 is a partially enlarged sectional view of the grinding device shown in FIG.

FIG. 3 is a flowchart showing steps of a grinding method according to the embodiment of the present invention.

FIG. 4 is a flowchart showing steps of a grinding method according to the embodiment of the present invention.

FIG. 5 is a diagram showing a load current curve of a spindle when a workpiece is ground at a predetermined cutting speed.

FIG. 6 is a diagram showing a load current curve of the main shaft when the feed speed is increased in FIG.

FIG. 7 is a diagram showing a load current curve of a main shaft when a cutting amount is divided into two and a cutting pause time is inserted between the divided cutting amounts.

FIG. 8 is a diagram showing a load current curve of the main shaft when the feed speed is increased in FIG.

FIG. 9 is a diagram showing a load current curve of the main shaft when the feed speed is increased by inserting a cutting pause time between divided individual unit cutting amounts.

FIG. 10 is a diagram showing a load current curve of the spindle when the cutting pause time is increased in FIG. 9;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Grinding apparatus 14 ... Spindle 16 ... Grinding stone 18 ... Spindle 20 ... Chuck member 22 ... Work 24 ... Cup part 26 ... Inner wall surface

Claims (3)

[Claims] 1. A method for grinding a workpiece with a grindstone, wherein a load on a grain and an allowable limit are determined based on a moving speed of a grind surface formed on an outer periphery of the grindstone, a diameter of the grindstone, a diameter of the work, and a rotation speed of the work. And a step of setting the cutting speed so that the load is substantially constant with respect to the cutting amount based on the calculated data, grinding the work under the set conditions, and a load current value of the spindle. Is measured, the feed speed of the grindstone is increased until the measured load current value reaches the allowable load limit value, and when the load current value reaches the allowable load limit value, the load current value is minimized. And setting the number of revolutions of the work to, further increasing the feed speed of the grindstone, dividing the cut amount into a plurality when the load current value exceeds the allowable load limit value, the divided unit cut amount A step of inserting a cutting pause time between, and repeating the division of the individual unit cutting amount and the insertion of the cutting pause time until the load current value decreases, the load current value at the time of cutting is within the allowable load limit value and Controlling the feed rate so as to be substantially constant in a range close to the allowable load limit value, and stopping the division when the individual unit cutting amount reaches a predetermined value set in advance. Grinding method characterized by having. 2. The grinding method according to claim 1, wherein, for each of the divided unit cut amounts, a feed rate is increased until a load current value reaches an allowable load limit value;
A grinding method characterized in that the division is repeated until the unit cut amount is equal to or less than the fine polishing amount. 3. The grinding method according to claim 1, wherein a cutting pause time inserted between a plurality of divided unit cutting amounts is gradually increased.