JPS62176762A - Dressing of grindstone consisting of superhard abrasive grain - Google Patents

Abstract

PURPOSE:To permit the speedy reduction of the grinding resistance immediately after trueing by activating the breakage of abrasive grains by increasing the damage applied onto an abrasive wheel by grinding-working a dressing roll in the state where the peripheral speed is reduced below that in the normal grinding, immediately after the trueing of the abrasive wheel. CONSTITUTION:After the truing for an abrasive wheel 12 is completed, the revolution speed of a motor 13 for driving a grindstone is reduced by controlling a motor speed control circuit 40, and the peripheral speed of the abrasive wheel 12 is reduced below the normal speed. Then the cutting-in grinding work is carried out for a dressing roll at a constant speed. If the detection value of a grinding resistance detector 35 is larger than a standard value at this time, the grinding work for the dressing roll is continued, and if the detection value is less than the standard value, the grinding work is completed. Thus, the grinding work is carried out by reducing the peripheral speed of the abrasive wheel, and the damage of the grindstone 12 is increased by increasing the load per piece of the superhard abrasive grain, and the breakage of the abrasive grains is activated, and the formation of acute cutting edge is accelerated. Therefore, the rate of the reduction of the grinding resistance is increased, and the speedy restoration to the ordinary grinding resistance is permitted.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for dressing an ultra-hard, low-grain grindstone.

<Prior art> In general, in a grinding device using a grinding wheel made of ultra-hard abrasive grains such as a diamond or CB N grinding wheel, the grinding resistance is high immediately after truing the grinding wheel and immediately before truing the next grinding wheel. Changes greatly. That is, as shown in Fig. 4, immediately after truing the grinding wheel (a,
In cases b, c, and d), the grinding resistance is high, and as the workpiece is ground, the grinding resistance decreases and reaches a steady state. This is because immediately after truing, the amount of protrusion of the abrasive grains from the bond on the outer peripheral surface of the stone is small, and the cutting edge at the tip of the abrasive grains is blunted, so the cutting ability of the grinding wheel becomes poor and the grinding resistance increases. As the grinding process progresses, the bonds between the abrasive grains are scraped by the chips generated during the grinding process, forming chip pockets, and the cutting edge at the tip of the abrasive grains becomes sharper, reducing the grinding resistance. It is.

<Problem to be solved by the invention> For this reason, in the past, when the cutting quality of the grinding wheel is poor immediately after truing the grinding wheel, efforts have been made to suppress the increase in grinding resistance by, for example, reducing the cutting speed of the grinding wheel head. However, in such a method, it takes a considerable amount of time for the grinding resistance to decrease to the normal level, and during this time the workpiece must be ground at a reduced grinding efficiency as described above, which reduces the cycle time. There was a problem with the length of time.

<Means for Solving the Problems> In view of the above-mentioned conventional problems, the present invention is designed to reduce the large grinding resistance immediately after truing to the steady grinding resistance in a short time. After truing a grinding wheel with ultra-hard abrasive grains, the dressing roll is ground by lowering the peripheral speed of the grinding wheel from the normal peripheral speed for grinding the workpiece, and the grinding resistance during this dressing roll grinding is predetermined. After the peripheral speed of the grinding wheel has decreased to a reference value, the peripheral speed of the grinding wheel is returned to the normal peripheral speed and the workpiece is ground.

<Function> □ With the above configuration, when the truing of the grinding wheel is completed, the peripheral speed of the grinding wheel is reduced and the dressing roll is ground. As a result, the grinding wheel actively crushes the ultra-hard, low-grain particles, producing sharp cutting edges quickly and reducing grinding resistance. When the grinding resistance decreases to a predetermined reference value, the circumferential speed of the grinding wheel is returned to the normal circumferential speed for one summer in order to proceed to the workpiece grinding cycle.

<Example> Embodiments of the present invention will be described below based on the drawings.

In FIG. 1, reference numeral 10 indicates a head of a grinding device, and a grindstone head 11 is placed on this bed 10 so as to be movable forward and backward. A grinding wheel 12 made of ultra-hard abrasive grains such as diamond or CBN is rotatably supported on the grinding wheel head 11, and this grinding wheel 12 is driven by a belt transmission device 14 by a grinding wheel driving motor 13 installed on the grinding wheel head II. It is designed to be rotationally driven through. However, the grindstone drive motor 1
Reference numeral 3 is an AC motor, the rotational speed of which is controlled by an inverter, which will be described later. The grindstone head 11 is moved forward and backward by a feeding mechanism using a servo motor 15 as a driving source.

A table 17 is placed on the bed 1o, a workpiece W is supported between a headstock 18 and a spindle 19 installed on the table 17, and a spindle drive motor is installed on the headstock 18. It is designed to be rotationally driven by 20.

In FIG. 2, 21 indicates a truer that trues the grinding wheel 12 every time a certain number of workpieces W are ground;
This cutting ram 21 is supported on the grinding wheel head 11 so as to be movable in the radial and axial directions of the grinding wheel 12.
It has a rotating shaft bearing. The cutting ram 22 is cut by a unit amount toward the grinding wheel 2 by a cutting device 23 using a motor as a driving source, and is moved in the axial direction of the grinding wheel by a traverse device (not shown) to true the grinding wheel 12. It looks like this.

Further, reference numeral 25 denotes a dredge/nosing roll for dressing the grinding wheel 12, which is rotatably supported by a cutting table 26 that is supported movably in the radial direction of the grinding wheel 12. As described later, after the truing of the grinding wheel 12 is completed, the dressing roll 25 is cut toward the lower stone wheel 12 by a cutting device 27 using a motor as a drive source, and is ground by the grinding wheel 12. It has become.

In addition, in the figure, 28 indicates a truer drive motor, and 29 indicates a dressing roll drive motor.

Reference numeral 30 denotes a numerical control device that distributes pulses to the drive circuit 31 that drives the servo motor 15 to feed and control the grindstone head 11, and this numerical control device 3 mainly includes an arithmetic processing device 32, a memory 33, and a pulse distributor 34. Reference numeral 35 denotes a grinding resistance detection device that detects grinding resistance by inputting the power of the grindstone drive motor 13, and the output of this detection device 35 is inputted to the arithmetic processing device 32 via an interface 36. The memory 33 stores a grinding program for grinding the workpiece W, and also stores a preset reference value F of grinding resistance.
O is written 1. It has been a.

Reference numeral 40 indicates a motor speed control circuit consisting of an inverter 41. A signal corresponding to the grinding resistance detected by the grinding resistance detection device 35 is given to this control circuit 4o, and the control circuit 4o controls the grinding wheel according to this signal. The rotation speed of the drive motor 13 is controlled.

That is, the inverter 41 constituting the motor speed control circuit 40 rectifies a three-phase AC power source using a SIRISK to convert it into a DC voltage, and turns this DC voltage on and off at a predetermined period using the SYRISK to generate an arbitrary AC voltage. This AC voltage is applied to the AC motor 13 for driving the grindstone, and the AC motor 13 is rotated at a speed corresponding to the frequency of the AC voltage output from the inverter 14.

The arithmetic processing unit 32 is configured to control an inverter 41 to change the circumferential speed of the grinding wheel in accordance with the grinding resistance input from the grinding resistance detection device 35. teeth,
The peripheral speed of the grinding wheel 12 is controlled to be converted to a much lower peripheral speed (for example, 30 m/s) than the normal peripheral speed (for example, 80 m/s) for grinding the workpiece W, and the grinding resistance is predetermined. When it becomes smaller than the reference value FO, the grindstone circumferential speed is controlled to return to the normal circumferential speed in order to shift to the grinding cycle of the workpiece W.

That is, immediately after truing when the grinding resistance is high, the frequency of the AC voltage output from the inverter 41 is lowered to reduce the rotation speed of the AC motor 13, and after the grinding resistance becomes equal to or less than the reference value FO, the inverter 41 The rotational speed of the AC motor 13 is increased by increasing the frequency of the AC voltage output from the AC motor 13.

Next, the process of dressing the grinding wheel 12 in the above-described configuration will be explained based on FIG. 3.

When the truing of the grinding wheel 12 is completed, the motor speed control circuit 40 is first controlled in step 101 to reduce the rotational speed of the grinding wheel drive motor 13, and the rotation speed of the grinding wheel 12 is reduced.
is converted to a lower peripheral speed (for example, 30 m/s) than the normal peripheral speed (for example, 80 m/s). Next, in step 102, the dressing roll 25 is cut toward the grinding wheel 12 at a constant speed, and the dressing roll 25 is ground. In step 103, the grinding resistance detected by the grinding resistance detection device 35 is set to a reference value F.
It is determined whether it is smaller than O. If NO, the process returns to step 102 to continue the grinding of the dressing roll 25, and if YES, the process moves to step 104 to complete the grinding of the dressing roll 25. Ru.

In this way, the dressing roll 25 is
By performing the grinding process, the load applied to each super-hard abrasive grain of the grinding wheel 12 becomes large, and the damage to the grinding wheel 12 increases, and for this reason, the super-hard abrasive grains are actively crushed. , the formation of sharp cutting edges is promoted. Therefore, the reduction ratio of the grinding resistance to the amount of grinding increases as shown by the solid line in FIG. 5, and the grinding resistance is quickly restored to a steady state. For comparison, the ratio of decrease in grinding resistance to the amount of grinding when grinding is performed under normal grinding conditions (grinding wheel circumferential speed of 80 m/s) is shown by the broken line in FIG.

When the grinding of the dressing roll 25 is completed in step 104, the motor speed control circuit 40 is controlled in step 105 to increase the rotational speed of the grinding wheel drive motor 13, and the peripheral speed of the grinding wheel 12 reaches the normal peripheral speed. After that, the grinding cycle of the workpiece W is started.

In the above embodiment, an example was described in which the grindstone drive motor (AC motor) is controlled by an inverter in order to control the circumferential speed of the grindstone, but various known methods can be used to control the motor speed. .

Further, in the above embodiment, an example was described in which the grinding resistance is detected from the power of the grinding wheel drive motor, but such grinding resistance may be detected by, for example, a strain gauge attached to the center of the grinding wheel, or alternatively, the grinding resistance may be detected by a strain gauge attached to the center of the grinding wheel. It is also possible to detect by the differential pressure between the front and rear pockets of the bearing.

<Effects of the Invention> As described above, in the present invention, immediately after the grinding wheel is trued, the dressing roll is ground with the circumferential speed of the grinding wheel being lower than that during regular grinding. It has the effect of increasing damage to the grinding wheel, activating the crushing of ultra-hard abrasive grains, and quickly reducing grinding resistance immediately after truing.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is an overall view of the grinding device including a plan view and a block diagram, FIG. 2 is a diagram showing the relationship between the grinding wheel, the truing device, and the dressing device, and FIG. Figure 3 is a flowchart showing the dressing process, Figure 4 is a diagram showing the change in grinding resistance with respect to the number of grinding pieces, and Figure 5 is a diagram showing the change in grinding resistance with respect to the amount of grinding when the peripheral speed of the grinding wheel is reduced. . DESCRIPTION OF SYMBOLS 11... Grinding wheel head, 12... Grinding wheel, 13... Grinding wheel drive motor, 25... Dressing roll, 35...
...Grinding resistance detection device, 40...Motor speed control circuit.

Claims (1)

[Claims] (1) In a grinding device in which a grinding wheel made of ultra-hard abrasive grains is rotatably mounted on a grinding wheel head, after the grinding wheel is trued,
The peripheral speed of the grinding wheel is lowered than the normal peripheral speed for grinding the workpiece, and the dressing roll is ground by the grinding wheel, and after the grinding resistance during this grinding process has decreased to a predetermined reference value, the grinding wheel is A method for dressing an ultra-hard abrasive grindstone, characterized in that grinding of a workpiece is performed by returning the circumferential speed to the normal circumferential speed.