JPH0453630A - Machining device using electric discharge - Google Patents

Abstract

PURPOSE:To enable a machining device to machine a straight hole high in roundness by giving relative machining feed between a rotating electrode and a base material, while detecting the extent of torque in the rotating electrode of the device machining the base material by means of pulse discharge, and controlling the machining feed so as to keep the torque constant. CONSTITUTION:The foremost end of a pipe electrode 1 is brought into a state of approaching a work body 2 by drive of a servomotor 9, supplying a working pulse from a terminal 11, and this work body 2 is machined by means of electric discharge. During operation, the pipe electrode 1 is rotated at high speed by a motor 5, measuring a drive current of this rotary motor with a resistor 19 and detecting the extent of turning torque, and it is fed to a comparator 17 by way of an amplifier 20, comparing it with the setting reference value. When a detection torque signal is increased, output of this comparator 17 comes to a state of zero, whereby a gate 14 is closed and machining feed by the servomotor 9 is suspended, and when the detection torque signal is decreased, a relative output of the comparator 17 comes to a state of 1, and thereby the gate 14 is opened and a signal out of an analog-to-digital converter 15 is added to the servomotor 9, thus the machining feed is applied.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention uses a rotating electrode, makes it face the base material, and generates a pulsed electric discharge between the two, thereby performing, for example, drilling. , Weld coating processing, so-called STUD processing in which welded parts are discretely raised on the surface of the base material to form a large number of protrusions, etc. Equipment that processes the base material using electric discharge from a rotating electrode. Regarding improvements.

[Prior art and problems to be solved] Outer diameter is 1 m
mφ = 1000 to 20 using a pipe electrode with the following
A small-hole electric discharge machining apparatus is known that generates a pulse discharge between an electrode and a workpiece while rotating at a speed of about 0 rpm, feeds the electrode into the workpiece, and performs drilling.

In this small hole machining, the ratio of the machining depth L to the machined hole diameter L
When machining a deep hole where /D is 10 or more, the machining becomes extremely difficult due to vibration of the electrode tip, difficulty in removing machining debris, and decreased flow rate of machining fluid, making it impossible to obtain the desired machining depth. There were also problems in that holes with high straightness and diameter accuracy could not be obtained.

In addition, in this type of machining, machining fluid is supplied to the machining gap by a pressurized jet from the pipe electrode, and this jet of machining fluid is used to generate and extinguish electrical discharge, and to cool the electrode and workpiece. , maintaining the generation of explosive pressure in the discharge gap, removing machining debris and gas generated in the machining gap from the machining gap, and holding the rotating vibrator electrode as a fluid bearing.

Therefore, supply of this machining fluid and control of the supply pressure are extremely important in order to perform stable small hole machining.

On the other hand, in order to maintain a constant discharge gap, machining feed is applied to the electrode as machining progresses, causing the electrode to gradually penetrate deeper into the workpiece. Conventionally, when controlling this feed signal, the workpiece and electrode The voltage, current, etc. between the two are detected and compared with a reference voltage to drive and control the machining and feeding device.

However, for example, when the processing current density is about 5000 to 700
In this type of small hole machining, which is performed at a high current density reaching more than 0 A/cm', the ratio of voltage and current is not necessarily proportional to the discharge gap, so depending on the machining feed control as described above, However, it has been impossible to always keep the relative position of the electrode tip to the machined hole of the workpiece constant.

In addition, if pulse discharge is continued in a state where the machining gap cannot be maintained constant, not only will the side wall of the machined hole be reworked, making it impossible to maintain the precision of the machined hole, but also arc discharge will occur. This may cause the machining speed to drop, making machining impossible, or causing abnormal electrode wear.
In particular, it was extremely difficult to process small holes with a diameter of 0.3 mm or less.

In addition, an electric discharge is applied to the gap between the rotating electrode and the base material, and while the electrode is moved relative to the base material by small distances, the melt at the minute discharge point of the electrode is welded to the base material, creating a welded coating on the surface of the base material. When performing stud processing where electrode material is discretely spot welded from point to point intermittently on the welded heap,
Whether it is controlling the relative movement or controlling the generation of pulsed discharge, it is not possible to achieve stable and optimal control when the voltage, current, impedance, etc. of the machining gap are used as signals as in the past. It was difficult to do.

[Means to solve problems]

The present invention has been made to improve the above-mentioned drawbacks, and the purpose is to make the rotating electrode face the base material,
In a device that processes the base material by giving a relative machining feed between the two and generating a pulse discharge between the two, a device is installed to detect and measure the torque of the rotating electrode, and the detection signal is used to detect and measure the torque of the rotating electrode. This is achieved by providing a device that controls machining feed so that the torque is constant.

The above problem can also be solved by providing a device for controlling the machining power source to generate a pulsed discharge only when the output of the rotating electrode torque sensing and measuring device is below a certain limit value.

[Effect]

When the electrode rotates at high speed in a small hole drilled in the workpiece with the aid of machining fluid supply, the thin electrode tip emerges from its core due to the self-aligning action of the machining fluid. This is a type of hydraulic bearing action, and due to this centering action, the rotational torque is minimized when the motor is completely centered.

Therefore, by detecting and measuring the torque of this rotating electrode, it can be easily and accurately determined whether or not the core of the rotating electrode is protruding.

If the core is not protruding and the electrode tip is in contact with the inner wall of the machined hole, if the machining feed is continued and discharge machining is continued, the machined hole may be bent, arc discharge, short circuit, etc. However, by detecting the rotational torque of the electrode and feeding the machining with the center of rotation always protruding and causing pulsed discharge, a constant gap will always be maintained between the electrode and the base material. Since the diameter is maintained, stable machining is possible, and straight holes with high roundness can be machined.

In addition, in electrical discharge coating and stud processing, the torque increases rapidly when the rotating electrode is press-fitted into the welding layer, so by controlling the relative movement by detecting this torque, it is possible to always maintain electrical discharge welding under constant conditions. Therefore, it is possible to perform coating processing and stud processing with good surface accuracy and less unevenness.

〔Example〕

Hereinafter, the present invention will be explained with reference to the drawings.

11th i? 1 is a configuration diagram of an apparatus showing one implementation of fine and large electrical discharge machining. In the figure, l is a pipe electrode for fine and large drilling, 2 is a workpiece, and both are connected through a machining gap. facing each other.

Reference numeral 3 denotes a rotary spindle, which is rotatably supported by a bearing, and a chuck 4 provided at its tip fixes the pipe electrode l.

5 is a rotation motor for the spindle 3, and 6 is a ram supported by the head of the machine so as to be able to move up and down, and supports the motor 5 and the spindle 3 at its tip.

A feed screw 7 is screwed into a nut 8 fixed to the upper end of the ram, and is rotated by a servo motor 9 to control the vertical movement of the ram 6.

IO is a processing table that fixedly supports the workpiece 2, and has a mechanism for rotating the workpiece 2 in the X-axis and Y-axis directions perpendicular to the central axis of the pipe electrode 1, and further around the central Z-axis.

Reference numeral 11 denotes a connection terminal of a machining power source that passes machining pulses between the pipe electrode 1 and the workpiece 2, and the conduction polarity is different when the pipe electrode is the positive electrode and the workpiece 2 is the negative electrode, and vice versa. There are cases where it is polarized.

12 is an electrode, a resistor for detecting the average voltage between the workpieces, 1
Reference numeral 3 denotes an A/D converter for the detection signal, which passes this signal through an AND gate 14, and then supplies the analog signal converted by the A/D converter 15 again to the servo motor 9 to provide machining feed.

16 is a reference value setter which applies a setting signal to the gate 14;

Reference numeral 18 denotes a drive power supply for driving the rotary motor 5. A detection resistor 19 for detecting the motor drive current is inserted into this power supply circuit, and the detection signal is amplified by an amplifier 20.
In addition to step 5, the signal is compared with a reference signal set by the setting device 16.

Reference numeral 21 denotes a supply pipe for machining fluid supplied from a pump (not shown), which passes through a rotary joint 22, a neutral path of the rotary spindle 3, and supplies the machining fluid by injection to the machining gap from the chuck 4 through the pipe electrode.

Fine and large electrical discharge machining is performed with the tip of the pipe electrode 1, through which machining fluid is injected, facing the hole drilling position of the workpiece 2.

Positioning control of the processing position is performed while moving the workpiece 2 by controlling the XY table lO, fixing it when a predetermined position is reached, and moving the tip of the pipe electrode l to the workpiece 2 by driving the servo motor 9. The workpiece 2 is machined by turning on the switch and supplying machining pulses from the terminal 11 to cause electric discharge to occur.

The jet pressure of the machining fluid ejected from the pipe electrode 1 is normally at least 10 kg/cm'' or more, and machining is proceeded while discharging machining debris generated in the narrow machining gap with this jet. Machining is performed without deeply penetrating into the narrow area formed on the workpiece 2 by feeding the workpiece.

During processing, the pipe electrode 1 is rotated at high speed by the rotary motor 5. This rotation of the electrode also improves the effect of removing machining debris, generated gas, etc., and enables stable deep hole machining.

Therefore, when the pipe electrode l rotates at high speed in the machining liquid spouted at high pressure in the machined thin part of the workpiece 2, the tip of the thin electrode naturally centers due to the self-aligning action of the machining liquid. will appear.

If the tip of the electrode l swings and touches the thin hole wall, or if friction increases due to the intervening machining fluid, the drive current supplied from the power source 18 to the motor 5 that rotates the pipe electrode 1 increases in proportion to the torque. do.

On the other hand, when the core is rotated due to the self-aligning effect of rotation, the rotational torque is at its lowest and the current in the drive power supply circuit is at its minimum.

Therefore, if the drive current of the rotary motor is measured by the resistor 19, the rotational torque can be detected, and it can be determined whether the thin pipe electrode 1 is rotating at its core.

The detection signal is supplied to the comparison circuit 17 via the amplifier 20, where it is compared with a set reference value.

If the reference value is set so that the output of the comparator circuit 17 becomes 0 when the detected torque signal increases, the gate 14
is closed and processing feed by the servo motor 9 is stopped.

Conversely, when the detected torque signal decreases, the comparison circuit 17
The comparison output becomes state 1, and at this time, the gate 14 is opened and the signal from the A/D converter 15 is applied to the servo motor 9, so that machining feed is applied.

Therefore, by adjusting the setting of the reference value, it is now set so that only when the tip of the thin pipe electrode 1 is rotating with the centering control controlled and the core protruding, processing feed is given by the servo motor 9. do.

Then, when the center is off and runout is occurring, no machining feed is applied and machining can be controlled to stop.

Therefore, according to machining feed control using this torque detection,
It is now possible to machine straight holes that are always straight, and deep, narrow holes can be machined stably and at high speed.

Note that detection of the rotational torque is not limited to the drive current of the rotation motor; measurement using a torque strain sensor made of piezoelectric material TbDyFe, a method of detecting changes in the rotational speed of a torque motor, and other conventional known torque detection methods can also be used. It can be used at will.

Further, the setting of the reference value by the setting device 16 may be changed depending on the viscosity of the machining fluid, etc., or the machining feed may be a constant speed feed and the machining feed may be intermittent by torque detection. good.

Furthermore, although the control of machining feed has been described above, it may be configured such that torque changes are detected and machining pulses are supplied to perform machining only when the rotational torque is within a certain value range. The equipment also makes it possible to consistently machine straight holes.

Moreover, if the machining feed control and the machining pulse supply control are controlled simultaneously, the machining accuracy can be further improved and more stable high-speed machining can be performed.

FIG. 2 is a schematic diagram showing an example of coating processing by micro welding using electric discharge. In the figure, 23 is a workpiece, which is fixedly mounted on an NC table 24 with XY-axis drive control. Ru.

Reference numeral 25 denotes a coating material tip electrode, which is attached to the tip of a rotating spindle 26 and coats the surface of the base material 23 while moving relatively thereon.

33 is a rotation motor for the spindle 26, and 28 is a pulse power source for discharging, which is connected to the tip electrode 25 and the workpiece 23 through a conductor 27 to supply current between them.

29 is an NC control device, which is an X-axis motor 3 for driving the table.
The position of the workpiece 23 is controlled by supplying NC drive signals to the 0 and Y-axis motors 31.

Reference numeral 32 is a torque sensor using an electrostrictive material that detects rotational torque in the support portion of the rotating spindle 26, and feeds back a detection signal to the NC control device 29 to control relative movement. A signal is added to control the supply of machining pulses to the gap.

The coating process using the above-mentioned device is performed using the rotating tip electrode 25.
is brought into light pressure contact with the coated base material 23, and a pulsed current is applied from the power source 28 between the electrode and the base material in this rotating contact state to repeatedly generate pulsed discharge, and the electrode material is heated by the action of the heat and electric field caused by the discharge. Melt the minute part and transfer the molten part to base material 2
Weld to 3.

The tip electrode 25 rotates at high speed, and repeats welding and coating by pulse discharge while moving the discharge point, and also rubs and smooths the welded surface.

Due to the discharge, the discharge points of the electrode 25 and the base material 23 are simultaneously melted and welding occurs at the peaks of the discharge marks, or the electrode 25 is formed into a small chip shape with respect to the base material 23 to have a sufficiently small heat capacity. Therefore, the electrode material is transferred and welded to the base material, the discharge point moves, and the relative movement of the base material 23 forms a coating layer of the electrode material on the entire surface to be machined.

It is recommended that the tip electrode 25 be coated by welding while applying vertical vibration in addition to rotation to vibrate the discharge-melted part, and by repeating such operations while repeating pulse discharge, the required amount can be achieved. It is also possible to form a built-up coating.

In such electric discharge coating processing, by applying cemented carbide to the electrode material, a carbide coating can be formed on the base material and hardened, thereby forming a wear-resistant surface. I can do it.

The thickness of the coating layer can be up to about 0.3 mm, and practically about 0.05111 In is sufficient. If the coated area 1al is processed for about 1 minute, a coat approximately 0.05 mm thick can be obtained.

If the rotating electrode is press-fitted into the welded layer while the welded part is still not cooled by the electric discharge between the electrode and the coated workpiece base material, the rotational torque increases.

If the welded coating layer is strongly press-fitted into the welded coating layer during processing, the welded layer will leave large and deep marks, and the coating surface will be uneven, resulting in a rough and inaccurate coating layer. However, the rotational torque of the electrode 25 is always detected by the sensor 32, and this detection signal is sent to the NC control device 29.
Since the NC relative movement control is performed by feeding back to As a result, the coating process is always performed with a constant rotational torque, and as a result, a coating layer with low surface roughness and high precision can be obtained.

In addition, the torque detection signal is also supplied to the machining power supply 28, and if the machining pulse is controlled to be supplied between the electrode and the base material only when the torque signal is below a certain value, the generation of pulse discharge and its occurrence can be further reduced. The weld coating process can now be performed stably and always under constant conditions, making it possible to obtain an extremely good coating layer.

This electrical discharge coating process is a method that forms a uniform welding layer on the surface of the base material, or in the case of stud machining, which performs discrete overlay processing by intermittent relative movement between the electrode and the base material. ,−
Since this is a processing method in which the protrusions are raised high by repeating pulse discharges one after another in one location, it is particularly difficult to use the discharge voltage as a signal.

However, if the electrode is pushed into the welding layer, the rotational torque will increase, so by detecting the rotational torque of the electrode and controlling the feed of the electrode using the detected torque as a signal, welding can always be performed at a constant torque or less. This allows for stable stud machining.

Of course, even in the case of this stud machining, the machining power source can be controlled on and off based on torque detection, thereby enabling more precise machining.

In addition, control of machining feed, servo feed, machining pulse, etc. can be controlled by using fuzzy inference using the detected torque signal as an ambiguous input, and by inputting actual measured values through experiments in advance, fuzzy rules and member If the membership function is written to memory as a membership function and fuzzy inference is executed using this memorized membership function to control feed, etc., it is possible to perform the same control as conventionally based on the intuition and experience of a skilled operator, resulting in stable operation. Good processing is possible.

〔Effect of the invention〕

As explained above, the present invention detects the torque of the rotating electrode in small hole electrical discharge machining, electrical discharge coating machining, stud machining, etc. in which a rotating electrode is used to generate electrical discharge between the base material and the machining process. This detection signal is used to control the relative machining feed between the electrode and the base material so that the torque of the rotating electrode is below a certain level. Since the feed is applied with the electrode or the core protruding, and deep hole machining is performed, there is no possibility that the machined hole will be bent or the machining will not progress due to short circuits, and the hole will be deeper than the conventional depth ratio L/D. It is possible to machine straight holes, and stable machining increases the machining speed, making efficient hole machining possible.Also, it is possible to perform electric discharge while continuously moving the facing part of the electrode and the base material relative to each other. In the case of electrical discharge coating processing in which electrical discharge welds are generated and covered by welding, and stud processing in which protrusions are formed by stacking electrical discharge welding and are formed discretely on the surface of the base material, the torque of the rotating electrode is detected and processed using this as a signal. By controlling the feed and relative movement, it becomes possible to easily perform highly accurate coating and stud forming processes with good surface accuracy.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the apparatus of the present invention, and FIG. 2 is a schematic diagram showing another embodiment. l... Electrode 2... Base material 5... Rotating motor 9... Servo motor 10... Processing table 11... Processing pulse energizing terminal 12... Voltage detection Resistor 13... A/D converter 14... AND gate 15... A/D converter 16... Standard setter 17... Comparison circuit 18... Rotating motor Drive power supply 19...Current detection resistor 20...Amplifier Patent applicant Representative of INR Research Institute Co., Ltd. (7524) Mogami Seidai Department Figure 2

Claims (2)

[Claims] (1) In a device that processes the base material by placing a rotating electrode facing the base material, applying a relative machining feed between the two, and generating a pulsed discharge in the opposing gap, the torque of the rotating electrode is controlled. A machining device using electric discharge as described above, comprising a device for detecting and measuring the torque, and a device for controlling the machining feed rate so as to keep the output signal of the torque detecting device at a predetermined constant value. (2) In a device that processes the base material by placing a rotating electrode facing the base material, applying a relative machining feed between the two, and generating a pulsed discharge in the opposing gap, the torque of the rotating electrode is controlled. The above electric discharge characterized in that it is provided with a device for detecting and measuring, and a device for controlling a machining power source so as to generate a pulsed discharge in the facing gap only when the output signal of the torque detecting device is below a certain value. Processing equipment that uses