JPH0379237A - Electric machining device - Google Patents

Abstract

PURPOSE:To miniaturize the feeding mechanism of a machining electrode, and to reduce the weight thereof by displacing a moving body by utilizing the impact force of an inertia body at the time a strain element is extendedly or compressedly driven, and by constituting a machining electrode associatedly provided to this moving body so that it can be minutely driven. CONSTITUTION:An inertia body 8 is impactedly driven by the stresses being produced when a strain element 7 is extended or compressed. Then, a moving body 3 is minutely moved against the sliding resistance provided to the moving body 3 through the reaction of the impact force, thereby a machining electrode 5 is moved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to electrical machining equipment such as electrical discharge machining equipment and electrolytic machining equipment, and particularly relates to an improvement in a feeding mechanism for machining electrodes.

[Prior Art] As is well known, this type of electrical machining device advances the machining process while making the workpiece and the machining electrode face each other with a small gap in between, thereby making the process compatible with the machining electrode possible. Hollow processing is being performed. Conventionally, a servo actuator using a hydraulic cylinder or a pulse motor has been used as a feeding mechanism for a processing electrode.

[Problems to be Solved by the Invention] However, the conventional device as described above has the following problems.

(+) In other words, if a processing electrode feeding mechanism uses a hydraulic cylinder or a pulse motor, the feeding mechanism itself would be considerably large and heavy, so it would be difficult to feed the processing electrode using a solid support erected on the table. It supports the mechanism. Therefore,
When the workpiece becomes large, the above-mentioned support gets in the way,
A problem arises in that the workpiece cannot be placed on the processing table and processing cannot be performed.

(2) Furthermore, since the feeding mechanism is large, there is a problem in that it is difficult to insert the feeding mechanism into a small space of the workpiece and process the workpiece.

(3) Since it is mechanically difficult to set a large feeding mechanism at a free angle, it is common to perform processing from the top of the workpiece. Therefore, for example, if a hole is to be machined on the side surface of a workpiece, the workpiece must be rotated and moved so that the machined surface faces upward, which is a hassle.

(4) In a feed mechanism using a hydraulic cylinder, the response time from valve operation to cylinder operation is long.

In addition, the feed mechanism using a pulse motor uses a reducer and a screw feed mechanism, and is equipped with a reduction mechanism with a large reduction ratio to enable minute movement adjustments. Therefore, the responsiveness of the feeding of the machining electrode deteriorates.

Therefore, when the machining speed is increased, it becomes difficult to maintain a constant micro-gap between the workpiece and the machining electrode, resulting in the problem that abnormal electrical discharge occurs and machining accuracy is impaired. In order to prevent such abnormal discharge, measures are taken to slow down the feed speed of the machining electrode or to reduce the discharge current, but such measures have the separate problem of lowering machining efficiency. A point occurs.

The present invention has been made to solve the above-mentioned problems, and in particular, the first invention aims to make the processing electrode feeding mechanism small and lightweight; In addition to the above objects, the second invention provides an electric processing device that can increase the responsiveness of feeding the processing electrode and accurately control the gap between the workpiece and the electrode. With the goal.

[Means for Solving the Problems] In order to achieve the above object, the present invention has the following configuration.

That is, the first invention described in claim (1) is an electric machining device that processes a workpiece with a machining electrode and a workpiece facing each other with a gap therebetween, in which sliding resistance is applied. A processing electrode feeder comprising: a movable body slidably supported in a state of The apparatus is equipped with a mechanism, and the movable body is displaced by the impact force of the inertial body when the strain element is driven to expand and contract, thereby moving the processing electrode provided in relation to the movable body.

Further, a second invention according to claim (2) includes, in addition to each configuration of the first invention, a gap detection means for detecting the size of the gap between the processing electrode and the workpiece; and gap control means for driving and controlling the strain element so as to maintain the gap constant based on the detection signal from the gap detection means.

[Work] The effects of the present invention are as follows.

According to the first invention, the inertial body is impulsively driven by the stress when the strain element expands or contracts, and the reaction (impact force) overcomes the sliding resistance applied to the movable body and moves the movable body. The processing electrode moves by making minute movements.

According to the second invention, the size of the gap between the machining electrode and the workpiece is detected, and based on the detection signal, the gap or the electrical discharge machining state falls within a predetermined range or state (spark discharge). The drive of the strain element is controlled as follows.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing a schematic configuration of an electric discharge machining apparatus according to an embodiment of the present invention.

In the figure, reference numeral 1 is a feed mechanism for moving the processing electrode 5. The feed mechanism 1 includes a rotatably supported cylindrical guide 2, and a movable body 3 is slidably inserted into the lower part of the guide 2.

The movable body 3 is pressed from the side by a spring 4 which is provided on the lower peripheral surface of the guide 2 and whose pressing force can be adjusted. It is configured to be granted. A processing electrode 5 is attached to the lower surface of the movable body 3, and a rod 6 used for detecting the position of the movable body 3 is erected on the upper surface of the movable body 3.

A known strain element 7 such as a piezoelectric element, an electrostrictive element, or a magnetostrictive element, and an inertial body 8 are loosely fitted into this rod 6 in that order, and the movable body 3 and the inertial body 8 are connected to each other via the strain element 7. connected. A position detection mechanism such as a differential transformer 9 is provided inside the upper part of the guide 2, and the position of the processing electrode 5 is detected by detecting the amount of elevation of the rod 6 using the differential transformer 9. has been done.

In addition to the feeding of the machining electrode 5 during electrical discharge machining, the reference numeral 10 indicates
This is a feed control circuit for moving the processing electrode 5 to an arbitrary position. This feed control circuit 1o detects a deviation S between the position detection signal Sl given from the differential transformer 9 and a position command signal S2 set in advance according to the set position of the processing electrode 5.
3, a voltage-frequency conversion circuit 12 that outputs a movement signal S4 which is a pulse signal with a frequency corresponding to the deviation S3, and a movement direction for specifying the movement direction of the processing electrode 5. The UP/DOWN signal S5 output from the movement direction designation circuit 13 including the designation circuit 13 is
The movement signal S is applied to the strain element drive circuit 20 via the switch SWI and output from the voltage-frequency conversion circuit 12.
4 is applied to the strain element drive circuit 20 via the switch SW2.

The reference numeral 30 indicates an electrical discharge machining control circuit for proceeding with electrical discharge machining while maintaining a small gap δ between the machining electrode 5 and the workpiece W, and the reference numeral 20 indicates a strain element drive circuit. This electric discharge machining control circuit 30 includes a power supply circuit 31 for applying a high voltage between the machining electric excavation 5 and the workpiece W, and a discharge current detection circuit 32 for detecting the discharge current during machining, The resistor R in the power supply circuit 31 and the discharge current detection circuit 32 form gap detection means that indirectly detects the gap between the machining electrode 5 and the workpiece W. The discharge current detection circuit 32 of the means outputs a discharge current detection signal obtained by converting the discharge current into a voltage value, that is, a signal s6 corresponding to the gap, to the voltage-frequency conversion circuit 33 and the comparison circuit 34. This voltage-
The frequency conversion circuit 33, the comparison circuit 34, and the strain element drive circuit 20 form gap control means for driving and controlling the strain element 7. The comparison circuit 34 of the means compares the optimal gap δ between the machining electrode 5 and the workpiece W or a reference value vatv predetermined according to the discharge state with the discharge current detection circuit S6. , its comparative output UP/D
The OWN signal S7 is sent to the machining amount setting circuit 35 and the switch SW.
It is output to the strain element drive circuit 20 via I. The movement signal S8, which is the output signal of the voltage-frequency conversion circuit 33, is given to the distortion element drive circuit 20 and the processing amount setting circuit 35 via the switch SW3 and the switch SW2, respectively. The machining amount setting circuit 35 is configured to preset the machining amount to be subjected to electric discharge machining (specifically, the distance by which the machining electrode 5 set at a predetermined position is lowered from that position).
It consists of a P/DOWN counter and a comparison circuit 34.
When the UP signal is given from the voltage-frequency conversion circuit 33, the movement signal S8 from the voltage-frequency conversion circuit 33 is counted UP, and the DO
DOW the movement signal s8 when the WN signal is given.
Count N. The machining amount setting circuit 350 force down-up signal and the machining start command are given to the switch SW3 as an opening/closing control signal, and the machining start command is also given as an opening/closing control signal to the switch SW4 included in the power supply circuit 31.

The distortion element drive circuit llR2O receives an UP/DOWN signal S4 given from the movement direction designation circuit 3 or the comparison circuit 34.
Alternatively, based on S7 and the movement signal S4 or S8 given from the voltage-frequency conversion circuit 12 or 33, a drive signal S9 for slightly moving the moving body 3 downward or upward is outputted to the distortion element 7.

Note that the gap detection means may be any other known means as long as it can detect the gap, and the gap control means may be the voltage-frequency control means if a pulse signal is obtained from the strain element drive circuit 2o itself or another circuit. The conversion circuit 33 may not be provided.

Next, the operation of the embodiment will be described with reference to the above-described configuration.

First, the principle of movement of the processing electrode 5 in this embodiment will be explained.

A minute movement device using an impact force using a strain element is disclosed in detail in Japanese Patent Laid-Open No. 63-299785, and an example thereof will be described here with reference to FIGS. 2 and 3.

When the processing electrode 5 is to be lowered, a drive signal S9 as shown in the left diagram of FIG. 2(C) is applied to the strain element 7. When the drive signal S9 has a voltage of 1, the distortion element 7 is in the contracted state 1 (shape B of length L) as shown in FIG. is gradually lowered to the voltage level, whereby the strain element 7 expands to a length of L+ΔL. At this time, the moving body 3 is stationary due to the sliding resistance provided by the spring 4, and only the inertial body 8 is displaced (see FIG. 3 (A-2)). Set the level to V,
When the force is suddenly returned from vI to vI, the inertial body 8 descends due to the rapid contraction of the strain element 7, and applies a downward impact force to the movable body 3 via the strain element 7.

When this impact force becomes larger than the sliding resistance of the moving body 3,
The movable body 3 descends by a minute distance corresponding to the magnitude of the impact force, and the processing amount i5 also decreases accordingly (Fig. 3 (A)
-3)).

When trying to raise the processing electrode 5, please refer to Fig. 2 (C).
A drive signal S9 as shown in the right figure is applied to the distortion element 7. When the drive signal S9 is at voltage 2, the strain element 7 is in an expanded state as shown in FIG. 3 (B-1)! ! I (state of length +ΔL). When the level of the drive signal S9 is gradually increased to the level of the voltage vI, the strain element 7 contracts and becomes longer. At this time, the moving body 3 is stationary due to the sliding resistance provided by the spring 4, and only the inertial body 8 is displaced (see FIG. 3 (B-2)). level vl
When the force is suddenly returned from v2 to v2, the inertial body 8 rises due to the rapid expansion of the strain element 7, and applies an upward impact force to the moving body 3 via the strain element 7. When this impact force becomes larger than the sliding resistance of the movable body 3, the movable body 3 rises by a minute distance corresponding to the magnitude of the impact force, and the processing electrode 5 also rises accordingly (see Fig. 3). (See B-3).

The operation of the apparatus of this embodiment using the principle of movement of the processing electrode 5 as described above will be described below.

When starting electric discharge machining, first, a position command signal S2 for lowering the machining electrode 5 to a predetermined position is given to the feed control circuit 10, and the moving direction designation circuit 1
3, the direction of movement (in this case, downward) is specified. Note that when moving the machining electrode 5 to a predetermined position (when a machining start command is not given), switch SWI,
SW2 is set on the feed control circuit 10 side.

When a descending command is given, the movement direction specifying circuit 13 outputs:
A DOWN signal S5 is output (see FIG. 2(a)), and this DOWN signal S5 is applied to the distortion element drive circuit 20.

On the other hand, the current position of the processing electrode 5 is detected by a differential transformer 9, and its position detection signal S1 is given to the differential circuit 11 of the feed control circuit IO.

The difference circuit 11 receives a position command signal S2 and a position detection signal S1.
The deviation S3 from the difference S3 is output to the voltage-frequency conversion circuit 12, and the voltage-frequency conversion circuit 12 outputs a movement signal S4 having a frequency corresponding to the deviation S3 (see the left diagram in FIG. 2 Φ). This movement signal S.4 is applied to the distortion element drive circuit 20 via the switch SW2. As a result, the strain element drive circuit 20 outputs to the strain element 7 a drive signal 39 (see the left diagram in FIG. 2(C)) that slightly moves the moving body 3 downward. As a result, the processing electrode 5 is integrated with the movable body 3 and lowered to a predetermined position (see the left diagram in FIG. 2(d)).

When starting electrical discharge machining, the machining amount of the workpiece W is set by presetting in the machining amount setting circuit 35 how far the machining electrode 5, which is set at a predetermined position, should be lowered from that position. Ru.

Then, in response to a machining start command from the operator, the switches SWI and SW2 are switched to the electrical discharge machining control circuit 30 side, and the switch SW of the electrical discharge machining control circuit 30 is switched to the electrical discharge machining control circuit 30 side.
3 and SW4 are switched to the ON state. As a result, a high voltage is applied between the machining electrode 5 and the workpiece W by the power supply circuit 31, and the machining electrode 5 and the workpiece W are lowered to a predetermined position by the feed control circuit 10 described above.
If the gap is wider than the gap at which discharge starts, discharge does not occur immediately even if a machining start command is given, so the discharge current detection signal S6 is zero. As a result, the comparison circuit 34 outputs the DOWN signal S7. On the other hand, when the discharge current detection signal S6 input to the voltage-frequency conversion circuit 33 is zero, the voltage-frequency conversion circuit 33 outputs a movement signal S8 having a relatively high frequency. The distortion element drive circuit 20 receives the DOWN signal S from the comparison circuit 34 described above.
7 and the movement signal S8 from the voltage-frequency conversion circuit 33, a drive signal 39 (see the left diagram in FIG. 2(C)) for slightly moving the processing electrode 5 downward is output to the strain element 7. do.

When the gap between the machining electrode 5 and the workpiece W gradually becomes smaller, electric discharge starts at a certain point.

The voltage-frequency conversion circuit 33 performs voltage-frequency conversion so that the frequency of the movement signal S8 becomes lower as the discharge current detection signal S6 increases. As a result, as the processing electrode 5 approaches the workpiece W, its descending speed decreases.

The discharge current detection signal S6 is the reference value VI! If it is approximately equal to or less than F, the comparison circuit 34 outputs DO
Since the WN signal S7 is given to the strain element drive circuit 20,
The processing electrode 5 continues to descend. Further, the DOWN signal S
7 is given to the machining amount setting circuit 35, the machining amount setting circuit 35 counts down the movement signal S8, and as a result, the count value of the machining amount setting circuit 35 gradually decreases from the initially set reset value. In other words, since the integrated value of the movement signal S8 corresponds to the amount of descent of the machining electrode 5, the count output of the machining amount setting circuit 35 indicates that the machining electrode 5 must be lowered as much as possible in order to perform the required amount of machining. This will show you what to do.

Until the processing amount setting circuit 35 counts up, that is,
Switch SW3 is ON before the required amount of machining is completed.
Since the movement signal s8 is in the switch SW3. SW
2 to the strain element drive circuit 20.

On the other hand, if the machining electrode 5 descends too much during machining and the gap δ becomes too small (too much), a large discharge current will be detected by the discharge current detection circuit 32.The discharge current detection signal S6 will be lower than the reference value (If the comparator circuit 34 becomes DOW)
Switch from N signal to UP signal (see Figure 2 (a))
, by giving this UP signal to the strain element drive circuit 20, the strain element drive circuit 20 sends a drive signal S9 (see the right diagram of FIG. 2(C)) for raising the processing electrode 5 to the strain element 7. Output to. As a result, the processing electrode 5 is slightly moved upward (see the right diagram in FIG. 2(d)), and the gap δ is widened. When the UP signal is output from the comparison circuit 34, the machining amount setting circuit 35, which manually inputs this signal, is switched to UP counting, and as a result of counting up the movement signal S8, the machining amount is increased by the amount that the machining electrode 5 has risen. When the zero gap δ to which the count value of the setting circuit 35 is corrected reaches the optimum value, the comparator circuit 34 is switched again to DOW N (f), and the electrical discharge machining proceeds in the same manner as described above. Electric discharge machining is performed while maintaining the gap δ between the electrode 5 and the workpiece W at an optimum value.

When the required amount of machining is performed and the machining amount setting circuit 35 counts up, the count up signal output from the machining amount setting circuit 35 turns the switch SW3 to the OFF state and cuts off the movement signal S8. ,
The lowering of the machining electrode 5 is stopped, and electrical discharge machining is completed.

Note that the present invention can also be modified as follows.

(1) In the embodiment shown in FIG. 1, the spring 4 is used as a means for applying sliding resistance to the moving body 3, but this is because the guide 2 and the moving body 3 are connected as shown in FIG. Each of them is made of a magnetic material, and by configuring an electromagnet with a coil 41 wound around the movable body 3 and applying an electromagnetic force between the movable body 3 and the guide 2, sliding resistance is created on the movable body 3. According to this embodiment, by controlling the current flowing through the coil 41, it is possible to easily increase or decrease the sliding resistance. Sliding resistance may be imparted to the moving body 3 by configuring the moving body 3 with a permanent magnet.

(2) In the embodiment shown in FIG. 5, a strain element 7a for electrode feeding is interposed between the movable body 3 and the inertial body 8, and a strain element 7a for adjusting the gap is interposed between the movable body 3 and the processing electrode 5. A strain element 7b is interposed. According to this embodiment, the strain element 7a for electrode feeding
is driven based on a movement signal from the feed control circuit 10 to quickly move the machining electrode 5, while the strain element 7b for gap adjustment is driven based on a movement signal from the electric discharge machining control circuit 30 to perform machining. The gap between the electrode 5 and the workpiece W can be controlled at high speed and with high accuracy. Processing electrode 5
Movement and gap control can be performed separately.
It is also possible to do both at the same time.

Note that when controlling the gap by applying a drive signal to the strain element 7, the processing electrode 5 itself acts as an inertial body to move the moving body 3 by applying an impact force to the moving body 3,
As a result, the processing electrode 5 is displaced. Of course, another inertial body may be provided between the strain element 7b and the processing electrode 5.

(3) FIG. 6 shows an application example in which the electrical processing device according to the present invention is attached to a robot hand.

That is, according to the present invention, the feeding mechanism 1 can be configured to be small and lightweight, so that the feeding mechanism 1 can be attached to the robot hand 42. According to such a machining device, it is possible to perform desired hole machining not only on the upper surface of the workpiece W but also on any inclined surface, so that machining efficiency can be significantly improved.

(4) FIG. 7 shows a processing device in which a plurality of feed mechanisms 1 are attached to a support base 43. Each feeding mechanism 1 can be formed in a small size, so they can be arranged in close contact with each other, and since each feeding mechanism 1 can be driven independently, it can be processed in one piece, unlike conventional devices. Compared to equipment that uses electrodes to drill multiple holes,
The accuracy of each hole machining can be improved.

(5) FIG. 8 shows an example in which the present invention is applied to an electrolytic processing apparatus.

In this electrolytic processing apparatus, a feeding mechanism including a moving body 3, a strain element 7, and an inertial body 8 is formed in a hollow shape. pump 45
The electrolytic solution 46 supplied from the inertial body 8 flows through the hollow and jets out from the tip of the insulator 44 attached to the lower end of the inertial body 8, and the hole is formed by passing an electric current through this jet. As described in the above embodiment, by applying a drive signal to the strain element 7, the insulator 44 is driven at a minute pitch, so that highly accurate processing can be performed.

(6) FIG. 9 shows another example of application.

In this application example, the feed mechanism 1 is composed of a servo system using a pulse motor 45, and a strain element 7 is used to control the gap between the processing electrode 5 and the workpiece W. That is,
The rotation amount of the pulse motor 50 for raising and lowering the processing electrode 5 is detected by the rotary encoder 51, and this detection signal is fed back to the differential circuit 52. The difference circuit 52 provides a differential output between the detection signal and the position command signal to the voltage-frequency conversion circuit 53. The output signal of this voltage-frequency conversion circuit 53 is transmitted to the pulse motor 5 via a motor drive circuit 54.
0, the processing electrode 5 is sent to a specified position.

On the other hand, the gap control system includes an electrical discharge machining control circuit 30 and a strain element drive circuit 20 similar to those described in FIG. The moving body 3 is provided with sliding resistance by a spring 4. According to this application example, the machining electrode 5 itself acts as an inertial body by the expansion and contraction drive of the strain element 7 and applies an impact force to the movable body 3, so that the movable body 3 moves, and as a result, the machining electrode 5 is also displaced. With such application examples,
Since the gap between the processing electrode 5 and the workpiece W can be controlled with high precision, it is possible to obtain the effect of improving processing accuracy. In addition, even in such an application example, the inertial bodies may be individually provided as in the embodiment shown in FIG.

[Effects of the Invention] As is clear from the above description, according to the first invention as set forth in claim (1), the movable body is moved by using the impact force of the inertial body when the strain element is driven to expand and contract. By displacing the movable body, the machining electrode installed in relation to the movable body is configured to be minutely driven, so compared to conventional devices that use servo systems such as pulse motors and hydraulic cylinders, the machining electrode The feeding mechanism can be made smaller and lighter. Therefore, according to the present invention, it is easy to attach the processing electrode feeding mechanism to a robot hand or the like and move it freely, and as a result, it is possible to process a large workpiece or move it to any surface of the workpiece. can be easily processed, as well as processing in small spaces.

Further, according to the second invention, the strain element is driven at high speed according to the gap between the processing electrode and the workpiece, so that the gap can be quickly set to an optimal distance. therefore,
According to the present invention, the gap is maintained in an optimal state even when the discharge current is relatively large, so that it is possible to improve machining efficiency and machining accuracy.

[Brief explanation of drawings]

1 to 3 are explanatory diagrams of an electric discharge machining apparatus according to an embodiment of the present invention, in which FIG. 1 is a block diagram showing its schematic configuration, FIG. 2 is an operation waveform diagram, and FIG. FIG. 3 is an explanatory diagram of the operation of the feeding mechanism. Fig. 4 is an explanatory diagram of a modification of the means for applying sliding resistance to a moving body, Fig. 5 is an explanatory diagram of a modification using two strain elements, and Fig. 6 is an illustration of a modification of the means for applying sliding resistance to a moving body. FIG. 7 is an explanatory diagram of a processing device equipped with a plurality of feed mechanisms, FIG. 8 is an explanatory diagram of an electrolytic machining device according to another embodiment of the present invention, and FIG. 9 is an explanatory diagram of a processing device equipped with a plurality of feed mechanisms. FIG. 1... Feeding mechanism 2... Guide 3... Moving body 4... Spring 5... Machining electrode
6... Ron door, 7a, 7b... Strain element 8... Inertial body 9... Differential transformer lO.
...Feed control circuit 11...Differential circuit 12...Voltage-frequency conversion circuit 13...Movement direction designation circuit 20...Strain element drive circuit 30...Electric discharge machining control circuit 31...Power supply circuit 32... Discharge current detection circuit 33... Voltage-frequency conversion circuit 34... Comparison circuit 35... Machining amount setting circuit 41... Coil 42... Robot hand 43... Support stand W. ... Workpiece SWl, SW2. SW3... Switch St... Position detection signal S2... Position command signal S3... Deviation 34, S8... Movement signal S5.37... UP/DOWN signal S9... Drive signal ■□ ,...Reference value δ for gap setting...Gap

Claims (2)

[Claims] (1) In an electric machining device that processes a workpiece with a machining electrode and a workpiece facing each other across a gap, a movable body is slidably supported with sliding resistance applied. and an inertial body connected to the movable body via a strain element, the movable body being displaced by the impact force of the inertial body when the strain element is driven to expand and contract. An electrical processing apparatus characterized in that a processing electrode provided in relation to the movable body is moved by moving the movable body. (2) The electrical processing apparatus according to claim (1), further comprising: gap detection means for detecting the size of the gap between the machining electrode and the workpiece; and based on the detection signal from the gap detection means, the An electrical processing device comprising: gap control means for driving and controlling a strain element to maintain a constant gap;