JPH01193124A - Power unit for electrochemical finishing machine - Google Patents

Abstract

PURPOSE:To machine and finish a work of three dimensional configuration in a short time and with high accuracy by providing a control device for selectively operating at least two sets of power units consisting of parallel-connected plural condensers and an electrodischarge switch connected to the above condensers and for supplying working pulses. CONSTITUTION:Condensers 27a-1-27a-n of a first power unit out of two sets of power units are charged with a specified voltage V1 assuring a specified current density, and condensers 27b-1-27b-n of a second power unit being charged with a higher voltage V2 than the specified voltage V1. When working pulses are supplied, a control device 24 is operated to allow the second power unit to discharge electric charges from the condensers of the power unit and obtain the specified current density in a short time. After that, the discharge from the condensers of the second power unit is stopped, the electric charges charged with the voltage V1 are discharged from the condensers of the first power unit, and working pulses of the specified current density are supplied between the electrodes.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a power supply device for an electrolytic finishing machine, and in particular improves the rise characteristics of a pulse current to process the surface of a workpiece in a short time and with high precision. Connect to the power supply of the electrolytic finishing machine for finishing.

[Conventional technology] Conventionally, metal processing machines fill the gap between the workpiece and the electrode with an electrolytic solution such as sodium nitrate or sodium chloride, flow this electrolytic solution at high speed, and generate electrolysis that inhibits stable electrolytic action. An electrolytic processing machine (Japanese Unexamined Patent Application Publication No. 1983-1983) that processes materials by passing a direct current from the workpiece to the electrode while removing eluted metal compounds, metal ions, hydrogen gas, etc.
71921 and Japanese Unexamined Patent Publication No. 60-44228), the workpiece and the electrode are placed facing each other with a small gap in a machining fluid such as water or kerosene, and these are connected to an appropriate power source. Electric discharge machines (see Japanese Patent Publication No. 60-26646 and Japanese Patent Application Laid-Open No. 60-177819) are known that generate instantaneous spark discharge or transient arc discharge between electrodes, and process a workpiece using the discharge energy. .

[Problems to be Solved by the Invention] However, the former electrolytic processing machine has problems, particularly in machining with a three-dimensional bottom (meaning machining of a three-dimensional structure formed in the shape of a concave hole). It is difficult to accurately transfer the electrode to the workpiece, making it difficult to obtain high-precision surface quality, and with the latter electric discharge machine, it is difficult to obtain good surface roughness. However, there is an inconvenience in that a lot of time and effort are required for surface finishing such as mirror finishing.

Therefore, the present applicant has proposed an electrolytic finishing machine that eliminates these inconveniences in Japanese Patent Application No. 62-27616 (Japanese Unexamined Patent Application No. 62-27616).
3-196321), the power supply device of this electrolytic finishing machine charges a plurality of capacitors with a voltage that provides a predetermined current density, and connects the charges between the capacitors and the workpiece. By simultaneously turning on a plurality of discharge switches, a discharge is caused and a machining pulse is supplied between the machining holes.

However, in this power supply device, the rise characteristic of the pulse current of the processing pulse is gradual, and there is a disadvantage that it is difficult to obtain highly accurate surface quality in finishing processing. That is, in the above-mentioned electrolytic finishing machine, the area of the workpiece to be processed is usually large, and the current value of the processing pulse is also very large. Therefore, in order to reduce loss, the power supply lines used to connect the capacitor, electrodes, and workpieces should have a large cross-sectional area and be as short as possible, but each has its limits, and as shown in Figure 4. , discharge switch 29
There is an external resistance R and an inductance between this and the workpiece 2.

Therefore, even if the resistance R of the power supply line is 1mΩ and the inductance is 1μH, the power supply line will be 1ms e
It has a time constant of c (T=L/R). This time constant can be reduced by increasing the external resistor R, but increasing this R increases power supply voltage loss and requires an inefficient high-voltage power supply. The reality is that power supply devices in this area sacrifice the rise characteristics of the pulse current of the processing pulse to some extent.

Therefore, the purpose of this invention is to provide an electrolytic finishing process that eliminates the above-mentioned disadvantages, improves the rising characteristics of the supplied pulse current, and finishes the machined surface of a workpiece with high precision in a short time to obtain a mirror-like glossy surface. The power supply device of the machine is realized.

[Means for solving the problem] In order to achieve this object, the present invention arranges a workpiece and an electrode having an electrode surface that follows the machined surface of the workpiece in an electrolytic solution so as to face each other with a predetermined gap, In this apparatus, the workpiece is finished machined while supplying a machining pulse having a predetermined current density between the poles and ejecting an electrolytic solution into the gap to remove machining debris from the gap, wherein the poles are connected in parallel. A capacitor that supplies machining pulses by discharging electric charge between
At least two sets of power supplies each consisting of a discharge switch connected between the capacitor and the workpiece to supply and disconnect the discharge of charge from the capacitor, and a rectifier connected between the capacitor and the power supply to prevent reverse flow of charge from the capacitor. The unit and the capacitor of the power supply unit are charged with a predetermined voltage (V1) that provides at least the predetermined current density, and a voltage (V2) higher than this voltage, and the voltage (
The present invention is characterized in that it includes a control device that selectively turns on the discharging switches of the power supply unit charged at the voltage (V2) and the power supply unit charged at the voltage (V1).

[Function] According to the configuration of the present invention, a plurality of capacitors connected in parallel, a discharge switch connected between the capacitors and the workpiece,
For example, two sets of power supply units each consisting of the capacitor and a rectifier connected between the power supply are provided, and the capacitor of the first power supply unit is charged with a predetermined voltage V1 that provides a predetermined current density, and the second power supply unit is charged with a predetermined voltage V1 that provides a predetermined current density. The unit's capacitor is charged with a voltage V2 higher than the voltage v1. Then, when supplying machining pulses, the charge is discharged from the capacitor of the second power supply unit, and the electric charge is raised to a predetermined current density in a short time, and when the predetermined current density is reached, the charge from the second capacitor is discharged. At the same time, the electric charge charged at the voltage V1 is discharged from the capacitor of the first power supply unit, and a machining pulse of a predetermined current density is supplied between the electrodes.

[Embodiments] Hereinafter, embodiments of the present invention will be described in detail and specifically with reference to the drawings.

1 to 3 show one embodiment of the invention. In FIG. 1, 1 is an electrolytic finishing machine, and this electrolytic finishing machine 1 includes an electrode fixing device 4 for fixing an electrode 3, and an electrode drive unit 5.
A control device 11 consisting of a drive conversion section 6 that converts rotational motion of the machine into a reciprocating motion, a power supply device 7 that generates processing pulses, a motor drive control section 8, a processing condition control section 9, and an electrolyte flow control section 10; Input device 1 for inputting data etc. related to ri2
2, an electrolyte filtration device 13, a processing tank 15 containing an electrolyte 14, and the like.

The electrode fixing device 4 has an electrode 3 made of, for example, pure copper or graphite attached to the lower end of a rod 16 provided at its lower part, with a gap such that the electrode surface 3a and the processed surface 2a of the workpiece 2 are spaced in a three-dimensional direction. Fix it so that it maintains 17. The electrode fixing device 4 is moved up and down by the electrode drive section 5 and drive conversion section 6 to set the gap 17 to a predetermined value. That is, the rotation of the motor 18 is controlled by control signals output from the motor drive control section 8 based on signals from the rotary encoder 19 and the tacho generator 20 of the electrode drive section 5, and the rotational movement of the motor 18 is transferred to the drive conversion section 6. The electrode fixing device 4 is converted into a reciprocating motion by
The input device 12 moves the electrode surface 3a and the machining surface 2a up and down to set a predetermined gap 17 between the electrode surface 3a and the machining surface 2a. The gap etc. are input, and these signals are outputted to the motor drive control section 8 and the machining condition control section 9, and the electrolyte filtration device 13 filters the electrolyte 1 containing electrolytic products generated during machining.
4, and supplies the electrolyte 14 to the machining tank 15 based on the control signal from the electrolyte flow control unit IO, and filters the electrolytic products generated between the machining surface 2a and the electrode surface 3a during machining. Fresh electrolyte 14 is spouted into the gap 17 via the spout nozzle 21 in order to eliminate the above.

The power supply device 7 generates machining pulses with a predetermined current density calculated based on the machining area of the workpiece 2 in response to a control signal from the machining condition control section 9.
It has a charging/discharging section 23 and a charging/discharging control section 24, and is configured as shown in FIG. 2, for example.

That is, in FIG. 2, the DC power supply section 22 is connected to the transformer 25.
and a rectifier 26, the voltage is lowered to a predetermined value by the transformer 25, and rectified by the rectifier 26 to obtain a direct current, which is then used in the capacitors 27a-1 to 27a-n and 27 to be described later.
b -1 to 27 b -n.

Further, the charging/discharging section 23 includes two sets of charging/discharging sections 23a and 23b.
The charging/discharging unit 23a includes a plurality of parallel-connected capacitors 27a that discharge charges between the workpiece 2 and the electrode 3.
-1 to 27 a -n and each of these capacitors 27a-1
-27a-n, and diodes 28a-1 to 28a-n to prevent backflow of charges to the DC power supply section 22 side.
n, discharge switches 29a-1 to 29a-n that are opened and closed to discharge the charge to the discharge side, and electricity from the DC power supply unit 22 to charge each of the capacitors 27a-1 to 27a-n to a predetermined value. Charging switch 30a that turns on and off the power of
It consists of. Note that since the charging/discharging section 23b is similarly configured, a description thereof will be omitted.

Charge and discharge control section 2 that controls the charge and discharge sections 23a and 23b
4 is a power storage device 27a-1 to 27a-n, 27b-1 to 2
Voltage detectors 31a, 3 that detect charging voltage values of 7b-n
1b, and a charging voltage setting section 36a of the processing condition control section 9.
, 36b and the voltage detector 31a.
, 31b, a current detector 35 that detects the current value of the charge discharged between the workpiece 2 and the electrode 3, and the minimum current setting section 39. The current comparator 34 compares the minimum current value from the A/D converter with the detected current value detected by the current detector 35, and a gate circuit 33.

Further, the machining condition control section 9 of the control device 11 that controls the charge/discharge control section 24 controls the charging voltage setting section 36a, 36
b, a pulse generation section 37, a current waveform setting section 38, a minimum current setting section 39, and a calculation/processing section (C
PU) consists of 40 grade. Note that the reference numeral 41 in FIG. 2 indicates discharge switches 29a-1 to 29a-n and 29b-1 to 29.
This is a diode that prevents the discharge switch from being destroyed by back electromotive force when b-n is opened.

Next, the finishing operation by this electrolytic finishing machine 1 will be explained.

During finishing, data regarding the workpiece 2 is inputted using the input device 12, and then the workpiece 2, which has been machined into a desired shape by electrical discharge machining, is fixed to a workpiece fixing device such as a surface plate, and an electrode fixing device 4 is used. The electrode 3 used during the electric discharge machining is fixed to the lower end of the rod 16, and the electrode 3 is lowered to a position that maintains a predetermined machining gap with the workpiece 2, and the electrolyte 14 is supplied to the machining tank 15. .

Then, when finishing machining is started, the CPU 40 first calculates a voltage v1 at which a predetermined current density ip is obtained, which is calculated according to the machining area of the workpiece 2, and sends this voltage v1 to the charging voltage setting section 36a. In addition to setting the voltage vl
For example, twice the voltage v2 (2×■1) is set in the charging voltage setting section 36b, and the capacitors 27a-1 to 27a-n are set to the voltage v1, and the capacitors 27b-1 to 27b-n are set to the voltage V2. Charge each. Note that the voltage v2 is 1.5X
V1 to 3XV1 is suitable.

Power storage units 27a-1 to 27a-n and 27b-1 to 27b
-n is charged with voltages Vl and v2, the gate circuit 33 is controlled as follows by the control signals of the pulse generator 37 and current waveform setter 38 of the processing condition control section 9 to perform machining between the gaps. Supply pulse.

That is, the discharge switches 29b-1 to 29b- of the gate circuit 33 are activated by the control signal from the processing condition control section 9.
Turn on the gate corresponding to the high voltage ■2 to discharge the charge from the capacitors 27b-1 to 27b-n, and when the predetermined current density is reached, the discharge switch 29b-1 is turned on.
29b-n is turned off, and the discharge switches 29a-1 to 29a-n are turned on to discharge the charges from the capacitors 27a-1 to 27a-n charged with the voltage Vt. As a result, as shown in FIG. 3(A), a pulsed current having a predetermined current density with improved rise characteristics is obtained.

Note that the reference numeral t1 in FIG.
-n is the time to discharge the charge, t2 is the capacitor 27a-1
~27a-n, the time until the peak value of the current density is reached, which is constant regardless of the voltage supplied from 27b-1 to 27b-n, and the symbol A indicates the pulse current by the capacitors 27b-1 to 27b-n. .

After supplying a machining pulse with a predetermined current density by the above method, the electrode 3 is raised and the electrolytic solution is spouted from the spout nozzle 21 into the gap 17, machining debris etc. in the gap 17 are removed, and the electrode 3 is is lowered to its original position again, and the gap 17 is
With the electrolyte stationary, by the same method as above,
The workpiece 3 is finished machined by repeating a series of steps of supplying the next machining pulse a predetermined number of times.

In this way, in the present invention, two sets of a plurality of parallel-connected capacitors are provided, and one of the capacitors 27b-1 to 27
b-n is charged at a voltage v2 higher than the voltage ■1 at which a predetermined current density is obtained, and the other capacitor 27a-1 is charged.
~27 a −n is the voltage Vt at which a predetermined current density is obtained.
The charge is discharged from the capacitors 27b-1 to 27b-n until a predetermined current density is reached, and then the capacitors 27a
Since charges are discharged from -1 to 27 a -n, a high-voltage machining pulse is supplied at the rise of the machining pulse, making it possible to improve the rise characteristics of the pulse current. In addition, the power supply unit with high voltage V2 is used only at the rise of the processing pulse, and after the specified current density is reached, the power supply unit with the specified voltage Vl is used, so it is necessary to use the high voltage power supply all the time. This enables efficient use of the power supply unit.

In the above embodiment, a case has been described in which two sets of power supply units are provided, but the present invention is not limited to this at all, and three or more sets may be provided and these may be used selectively.

[Effects of the Invention] As explained in detail above, the present invention provides at least two power supply units each including a plurality of parallel-connected power storage units and a discharge switch connected to the power supply units, and controls the power supply units by a control device. Since the machining pulse is supplied by selective activation, at the start of the machining pulse, the power supply is supplied from the power supply unit that has charged the capacitor with a high voltage, and after that, the power supply is supplied from the power supply unit that has charged the condenser with a predetermined voltage. Therefore, it is possible to improve the rise characteristics of the pulse current of the processing pulse, and it is possible to finish finishing a three-dimensional workpiece in a short time and with high precision.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of an electrolytic processing machine implementing this invention;
FIG. 2 is a block diagram of the power supply device of the processing machine, FIG. 3 is a current waveform and its timing chart, and FIG. 4 is a diagram showing an equivalent circuit of the main part. 2... Work, 3... Electrode, 7... Power supply device, 9
. . . Processing condition control unit, 11 . . . Control device, 23a,
23b... Charge/discharge unit, 24... Charge/discharge control unit, 27
a-1 to 27a-n, 27b-1 to 27b-no, capacitors 29a-1 to 29a-n, 29b-1 to 29b-n,
...Discharge switch, 33...Gate circuit, 36a, 36b...Charging voltage setting section, 37...Pulse generation section, 38...Current waveform setting section, 40...CP
U. Patent applicant Shizuoka Seiki Co., Ltd. Representative Shigeo Suzuki Figure 1 Figure 3 Figure 4

Claims (1)

[Claims] A. A workpiece and an electrode having an electrode surface patterned after the machined surface of the workpiece are placed facing each other in an electrolytic solution with a predetermined gap, and a processing pulse having a predetermined current density is applied between the electrodes. At the same time, the workpiece is finished machined while ejecting electrolytic solution into the gap to remove machining debris from the gap, (b) a plurality of electrolytes are connected in parallel and a machining pulse is applied between the electrodes by discharging an electric charge; It consists of a capacitor to be supplied, a discharge switch connected between the capacitor and the workpiece to supply and disconnect the discharge of charge from the capacitor, and a rectifier connected respectively between the capacitor and a power source to prevent reverse flow of charge from the capacitor. at least two sets of power supply units; c. charging the capacitors of the power supply units with at least a predetermined voltage (V1) that provides the predetermined current density and a voltage (V2) higher than this voltage; A power supply device for an electrolytic finishing machine, comprising: a control device that selectively turns on a discharge switch of a power supply unit charged at voltage (V2) and a discharge switch of a power supply unit charged at voltage (V1).