JPS6218313B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Conventionally, there is a method of measuring grinding force through the output of a motor that rotates a grindstone, but this method is not suitable for measuring small machining forces due to its poor sensitivity. Another possible method is to insert a force detector into the workpiece fixing part, but this method is not practical because it impairs the rigidity of the machine body during grinding. In such a highly rigid grinding machine, no method has yet been proposed for measuring micromachining forces in-process (during machining) without impairing its rigidity or workability.

Furthermore, no method has yet been proposed for in-process detection of the distance between the grinding wheel and the workpiece, or the state of contact, including damage to the grinding wheel, and there is therefore an extremely strong need for unmanned operation of grinding machines. Despite this, there were concerns that it could not be carried out safely.

In view of the above circumstances, an object of the present invention is to detect and monitor the contact state between the grinding wheel and the workpiece in-process without impairing the rigidity and workability of the machine body, and as a result, reduce machining time. It is an object of the present invention to provide a grinding machine monitoring device that can shorten the time and automate emergency stop when an abnormality occurs.

To achieve this purpose, the grinding machine according to the present invention includes a workpiece attached to a machine body, a grindstone that rotates to grind the surface of the workpiece, a grinding fluid having conductivity, and a grinding fluid attached to the workpiece or the grindstone. Voltage measurement comprising a nozzle that is injecting the grinding fluid and electrically insulated from the machine body, and measuring a contact potential difference generated between the grinding fluid and the workpiece through the nozzle. The present invention is characterized in that a means is provided so that the grinding state can be monitored based on the state of change of the contact potential difference.

The contact potential difference detected and monitored by the above configuration changes with changes in the temperature of the workpiece, so the grinding state can be grasped by monitoring the contact potential difference.

Hereinafter, the most preferred specific embodiments for carrying out the present invention will be described in detail.

FIG. 1 shows the structure around the grinding wheel of a surface grinder, and in the figure, a grinder 1 is supported rotatably in the direction of the arrow. The workpiece 2 is fixed to a table 3 that is a part of the machine body, and the table 3 reciprocates in the left-right direction in the figure while keeping the workpiece 2 fixed. The first nozzle 4-1 is supported by an insulating plate 6 while being electrically insulated from the machine body. Grinding fluid having electrical conductivity is ejected and supplied from the nozzle 4-1 via the grinding fluid hose 7-1. The grinding fluid ejected from the nozzle 4-1 enters the gap between the grindstone and the workpiece. The grindstone 1 is an electrical insulator, and the workpiece 2, table 3, and nozzle 4-1 are made of metal that is a good electrical conductor.
A measuring resistor 9-1 is connected between the nozzle 4-1 and the table 3, and the voltage generated across the resistor 9-1 is amplified by an amplifier 10-1. A first output V _T1 representing the contact potential difference between the two terminals is obtained.

On the other hand, the second nozzle 5 is arranged close to the outer periphery of the grindstone 1, and is electrically insulated from the machine body like the first nozzle 4-1. This second
An external power supply 11 and a measuring resistor 9-2 are connected in series between the nozzle 5 and the table 3, and the voltage generated across the resistor 9-2 is amplified by an amplifier 10-2. It is designed to obtain an output V _gap of . The present invention is a system in which a minute current is passed through a fluid nozzle, and the fluid nozzle corresponds to a fluid contact.

In this embodiment, the grinding fluid ejected from the first nozzle 4-1 is designed to flow along the outer peripheral surface of the grindstone in the rotation direction of the grindstone, but as shown in FIG. The nozzles 4-2 may be arranged close to each other, or the nozzles 4-3 may be arranged to face the outer peripheral surface of the grindstone from a direction perpendicular to the side surface of the grindstone.

Further, near the outer periphery of the grindstone 1, an air flow is generated along the rotational direction of the grindstone, and the grinding fluid is present in the form of a mist. The amount of the grinding fluid contained in the air flow layer (hereinafter referred to as the entanglement layer) in which the grinding fluid exists in the form of a mist is
When a certain amount of grinding fluid is supplied from -1 to the surface of the workpiece 2, the amount of grinding fluid contained in the drag layer 8 increases as the distance between the grinding wheel 1 and the workpiece 2 gets closer. As the electrical resistance between the second nozzle 5 and the table 3 decreases, the current flowing through the resistor 9-2 increases, and the output V
Since _{the gap} becomes large, it becomes possible to detect the approach distance between the grinding wheel 1 and the workpiece 2. This makes it possible to avoid rapid approach during dry grinding, reducing overall machining time. In order to improve the approach sensitivity, the optimum flow rates from the first and second nozzles may be determined experimentally. Further, even when a defect occurs on the outer circumferential surface of the grindstone, the value of the output V _gap changes, so that an abnormal state called a defect in the grindstone can be detected. Moreover, since no flexible means is installed between the workpiece and the machine body, and the workpiece is firmly fixed on the table, the rigidity of the machine body and workability are not impaired. Moreover, since the nozzle is electrically insulated from the machine body, the grinding fluid is made conductive, and a simple voltage measuring means is installed, the grinding state can be detected in-process and automatic processing can be performed in case of abnormal machining. It can be stopped.

Fig. 3 shows the grinding fluid-workpiece contact potential difference V _T1 ,
The actual measured value of the approach output V _gap representing the electrical resistance between the grindstone and the workpiece is shown. The actual measured values are recorded on a recording paper on which many parallel lines are printed at equal intervals in the vertical direction in the figure. That is, the upper curve in the figure represents the actual measured value of the output V _gap , and the lower curve in the figure represents the actual measured value of the output V _T1 . The magnitude of these outputs is indicated by the scale between the parallel lines, for example, the output V _gap shows 1V in 12 scales, and the output V _T1 shows 0.1V in 9 scales. In addition, the number written below the recording paper in the figure indicates the distance l between the grinding wheel and the workpiece, and the number 0 means that the grinding wheel is in contact with the workpiece, which means that dry grinding (left side in the figure) and actual grinding ( (right side in the figure). Symbol S indicates the distance that the recording paper moves in one second, symbol R indicates the right stroke of the table 3, L indicates the left stroke (see Figure 1), and W-1 and W-2 indicate the lower end of the grinding wheel. The figure shows the state where the part has passed through the workpiece. On the other hand, the output V _ga
As is clear from _{the p} waveform, the output increases as the wheel moves from left to right in the figure (as the grinding wheel approaches the workpiece), and as it becomes larger than a certain value, the distance between the grinding wheel and the workpiece becomes sufficiently small. It is possible to detect that the grinding fluid has worn out and increase the flow rate of the grinding fluid in the nozzle 4-1 in preparation for actual grinding, and also to slow down the cutting speed. FIG. 4 shows a record when it was determined that the grinding wheel was sufficiently close to the workpiece when the output V _gap value reached 1V, and the amount of grinding fluid was increased. Figure 5 shows the waveform of the output V _gap when the flow rate of the second nozzle 4-2 is made minute and the flow rate of the first nozzle 4-1 is adjusted to an appropriate amount in order to improve the sensitivity of the approach between the grindstone and the workpiece. show.

FIG. 6a is a schematic diagram showing a state in which V _T1 is being measured while feeding the workpiece in the opposite direction to the peripheral speed of the grindstone, and FIG. 6b in the same direction as the peripheral speed of the grindstone.

FIG. 7 shows details of the contact potential difference V _T1 waveform after actual grinding begins. In this grinding example, a workpiece that has been ground in advance is used, so the workpiece surface has a concave shape unique to grinding, and it can be seen that the first contact of the grindstone with the workpiece is at the end of the workpiece. In addition, the magnitude of the output V _T1 representing the contact potential difference is different between the right stroke (R in the figure) and the left stroke (L in the figure) of the table feed, but this is because in the right stroke, as shown in Figure a, immediately after grinding, Since the work surface temperature is high, the contact potential difference increases due to the influence of temperature, and the output V
_T1 is large, and in the left stroke, as shown in FIG. 2B, the work surface temperature immediately before grinding has already become low, so the output V _T1 shows a small value. The symbol P indicates the position where the amount of grinding fluid from the nozzle 4-1 is increased.

In Fig. 7, the cut was made by 1 μm in each pass from the left end of the figure to the position indicated by the symbol Q.
Further to the right, it is in a state of spark-out (micro-grinding). Corresponding to the concave shape of the workpiece grinding surface, the output V _T1 waveform also shows a concave shape (W-3 in the figure), and the output V _T1 increases with the number of sparkouts.
It is clearly detected that the magnitude of is decreasing.

FIG. 8 shows that minute defects in the grindstone can be detected during dry grinding using the output V _gap waveform. That is, as shown in Figure 8a, the grindstone is
It has an outer diameter of 275 mm, a width of 25 mm, and a peripheral speed of 1800 rpm (peripheral speed 24
m/s), and has a notch A on the outer peripheral surface with a depth of 1 mm and a width of 5 mm in the circumferential direction. The entangled layer 8 in FIG. 1 becomes discontinuous at the notch A, and when the notch A is located directly below the second nozzle 5 (see FIG. 1), the electrical resistance increases and the output V _gas As is clear from the figure, becomes a small value instantaneously (A-1 in the figure). Sign 0.1S is 1/10
This is the distance that the recording paper moves in seconds, and 1 rev indicates the distance that the recording paper moves in one rotation of the grindstone.

FIG. 9 shows the state of grindstone damage when actual grinding is carried out under the same grindstone conditions as explained in FIG. 8.
That is, since the output V _gap decreases every rotation of the grindstone, the waveform is wider than the waveforms shown in FIGS. 3 to 7. This tendency is also clearly seen in the output V _T1 waveform.

In the embodiments described above, the grinding fluid was poured onto the outer peripheral surface of the grinding wheel, but as shown in FIG.
An application example of a structure in which grinding fluid is injected into the center of the flange 13 fixed to the tip of the flange 2 will be described.
That is, in the figure, a main shaft 12 is rotatably supported by a machine body 3 via a ball bearing 14, and a grindstone 1 is fixed to the tip of the main shaft 12 via a flange 13. Said nozzle 5
-1 and the outer ring of the ball bearing 14
Connect a 5V external DC power supply and a 20KΩ measuring resistor in series to generate a voltage corresponding to the potential difference of the main shaft bearing 14.
Vc can be measured by a voltage measuring means (not shown). In Fig. 10, the waveform of the voltage Vc when the grinding fluid is injected from the nozzle 5-1 and the spindle is started to rotate is shown in Fig. 10a, and the waveform when it moves from the rotating state to the stopped state is shown in Fig. 10a. Shown in b. In this way, it is possible to clearly detect and monitor not only the large difference in voltage Vc between stop and rotation, but also the resistance value fluctuation in one rotation synchronization of the bearing.

Application examples of the present invention are not limited to surface grinders; FIGS. 11 and 12 show an example of application to a cylindrical grinder, and FIG. 13 shows an example of application to a centerless grinder.

In FIG. 11, the grinding fluid electrically insulated from the machine body is poured from the nozzle 4-4 onto the grinding surface of the workpiece 15, thereby reducing the potential difference between the nozzle 4-4 and the tailstock 17. It can be detected by amplifier 10-5 through resistor 9-4.

FIG. 12 shows an example in which two nozzles 4-4 and 4-5 are used, and the nozzle 4-5 is placed close to and opposite the end of the workpiece 15, the headstock 16, the tailstock 17, etc. .

In FIG. 13, the grinding fluid nozzle 4-6 and the work rest 20 are electrically insulated from the machine body.
As in the previous example, the potential difference between the two is detected by the resistor 9-5 and the amplifier 10-6, and the contact state between the work 21 and the work rest 20 can be detected, and abnormal vibration states due to chatter etc. can be monitored. can do. In this case, an externally applied voltage can also be applied in series with the measuring resistor 9-5. for example,
By applying an alternating voltage, the amplifier 10-
Due to the amplitude fluctuation of the AC component included in the output of 6,
It is also possible to detect the contact state between the work 18 and the work rest 17.

Therefore, the grinding machine embodying the present invention can detect and monitor the contact state between the grinding wheel and the workpiece in-process without impairing the rigidity of the machine body or the work quality, and can automatically detect and monitor the contact state between the grinding wheel and the workpiece in the event of abnormal machining. This is effective in making an emergency stop.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG.
The figure is a configuration diagram showing another embodiment of the present invention, FIGS. 3 to 5 are waveform diagrams showing the grinding wheel approach output, and FIG.
The figure is a schematic diagram depicting the state in which the contact potential difference is measured during grinding, Figure 7 is a waveform diagram showing the contact potential difference during actual grinding, and Figures 8 and 9 are each output in the case of a grinding wheel defect. Waveform diagram, Fig. 8a is a partial perspective view showing the grindstone notch, Fig. 10 is a partial sectional view showing an application example of the present invention, and Figs. 10a and b are when the spindle rotation is stopped according to the above application example. 11 to 13 are configuration diagrams showing still another application example of the present invention. 1... Grindstone, 2... Workpiece, 3... Machine body,
4-1 to 4-5... first nozzle, 5... second nozzle, 6... electrical insulator, 7-1, 7-2...
Grinding fluid hose, 9-1, 9-2...Measuring resistance, 1
0-1 to 10-6...Amplifier, 11...External power supply.

Claims (1)

[Claims] 1. A workpiece attached to a machine body, a grindstone that rotates to grind the surface of the workpiece, a grinding fluid having conductivity, and a grinding fluid that is injected onto the workpiece or the grindstone, and from the machine body. an electrically insulated nozzle, and a voltage measuring means for measuring a contact potential difference generated between the grinding fluid and the workpiece via the nozzle, and a voltage measuring means is provided to measure the contact potential difference generated between the grinding fluid and the workpiece, depending on the state of change of the contact potential difference. A grinding state monitoring device for a grinding machine, characterized in that it is configured to be able to monitor the grinding state of a grinding machine.