JPH06507843A - electrical spark discharge machine - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] There are various types of electrical spark discharge machines, but the A common method in which sparks are blown into the spark gap and erodes the processed material to create a shape. It has special characteristics. The conditions for sparks to fly depend on the speed of the intended work and the finished product. Although it varies depending on the material, etc., it is necessary to maintain the spark to ensure that the spark will fly. Applying a much higher voltage to the gap than is necessary to sustain it causes a spark to fly. is often desired. Conventionally, a series resistor (including internal resistance) is used, Adjust the output of the generator to produce a discharge current, and the gap between the sparks before the sparks fly. (Open circuit) As the output voltage becomes higher, the spark discharge causes a rapid increase in current. The voltage across the spark gap is necessary to maintain the discharge current at the desired level. It is said to settle down in important places. This arrangement uses a large amount of power in the regulating resistor. It has been observed that the amount of waste is wasted. For example, the voltage at which sparks fly is 1 00 volts, the discharge current is 100 amperes, which is necessary to maintain the discharge. The gap voltage is 27 volts (all typical examples), then once the When the flowers fly, 7,300 watts are on the duty cycle (DUJ7 cycle). The rest is wasted as wasted heat. In addition to wasting energy, this , high voltage generators capable of supplying high output currents are required; It is worth it.

British Patent Publication (GB-A-1196644) describes high voltage, high impedance A discharge machine that has a means of generating low voltage and high current after generating low voltage and high current. Disclosed. To connect the power supply to the work gap (to+kgn), Force switching means are provided. Its switching means are complex and expensive. Low voltage supply conditions when switching off with voltage supply and during spark extinction There is a transition period between when the switch is turned on and when the switch is turned on. For this purpose, the machine works people become poor.

British Patent Publication (GI3-A-947363) describes the discharge current and low voltage supply is taken from the main output transformer, or the high voltage supply is taken from the transformer and the Low voltage high current supply with transistorized switch function is used to reduce current Discloses a machine that produces In such devices low voltage high current supply It is difficult to ensure the timing of the discharge current due to the relationship between The correct spark gap may not always exist.

It is an object of the invention to power the discharge machine so that there is little or no wastage of power. The object of the present invention is to provide a simple and relatively inexpensive device for supplying.

According to another aspect of the invention, the relatively low short circuit output current and the A first power supply having a relatively high open circuit output voltage to strike a spark between the to maintain a low open circuit output voltage and spark discharge between the electrode and the workpiece. between the electrode and the workpiece, consisting of a second power source with a relatively high short-circuit output current. An electric discharge machine that generates sparks in a spark gap to erode the processed material, the The first and second power supplies are connected in parallel during the duty cycle and In addition, when the high load output voltage of the first power supply is higher than the high load output voltage of the second power supply, A discharge machine characterized by being provided with a means for preventing reverse current from flowing between two power sources. equipment will be provided.

During use, sparks are emitted by the first power source, which is a low short-circuit power source. Firstly, it is less expensive, and secondly, sparks fly and the gaps between When the voltage drops to, for example, 27 volts, the wasted power is lower.

For example, at the same discharge voltage of 100 volts, the short circuit current of the first power supply is 0.5 amperes. If so, the wasted power is only 36.5 watts. Furthermore, the discharge current The cost is much lower because the second power supply, which provides most of the , and the power wasted is also reduced. For example, open circuit of the second power supply If the output voltage is 45 volts at a discharge current of 100 amperes, then The wasted power is only 1800 watts.

Arrays can be quite simple in nature. For example, the preferred embodiment and the second power supply are connected in parallel during the duty cycle. or two or more diodes are placed in series with the output of the second power supply to Reverse current in the second power supply when the loaded output voltage is higher than that of the second power supply are arranged to prevent water from flowing. So, apply a discharge voltage to the spark gap. In connection with this, a switch control device that reduces the operating time of the second power supply is required. No. The word 1 prevent-1 here means that there is a so-called small "leakage" current. It is also intended to include the practical fact that

The duty cycle of the discharge machine is preferably such that the first stage is parallel to the spark gap. a second switch means in series with the output of the second power supply; and a duty cycle switch means. the first switch means is opened and the second switch means is closed; to close the first switch means and open the second switch means when the cycle is not cycling. and a switch control means.

The first power source preferably has a plurality of different discharge sources so that different operating states can be set. regulated to supply one of the electrical voltages.

Since the second power supply does not receive high voltage, a transistor is used to control its output current. It can be used. In this way, the discharge machine is preferably controlled in series with the output of the second power source. transistor means having a conductive path and a control gate of the transistor means; and means for providing a control signal current to determine the current in the controlled conductive path.

The advantage of this is that the duty cycle of the control signal Since it can be changed automatically between cycles, the discharge current can also be changed automatically. That's true. Experiments have shown that when properly adjusted (maat mouth 1ions), High working speed and fine finish are achieved at the same time. - e.g. current control means; However, the shape of the periodic current, for example, the ratio of current in continuous cycles is 1:2:4 or 1 :transistor means to supply what is a successive repetition of 4.16. can be adjusted to control As an alternative means, the current control means is such that the second power source is to generate a pseudo-random sequence of output currents. A signal generator may be provided and arranged to determine the control signal.

According to another aspect of the invention, the device has a relatively high open circuit output voltage and a relatively low short circuit output voltage. A spark discharge is sent between the workpiece and the electrode from the first power source that supplies the output current. And the 21st! has a relatively low open circuit current until the end of its processing! by the source spark discharge, which consists of maintaining a spark discharge between the workpiece and the electrode. A method for processing a workpiece, the first and second By connecting two power supplies in parallel, the highly loaded output voltage of the first power supply is It is specially designed to prevent reverse current from flowing in the second power supply when exceeding that of the power supply. A method is provided for identifying the characteristics.

By way of example, an embodiment of the invention will be described with reference to the accompanying drawings. In addition, each Regarding the figures, FIG. 1 is a block diagram of a spark generator of a discharge machine which is an embodiment of the present invention. and Figure 2 is a detailed diagram of the high voltage, high current generator of Figure 1, and Figure 3 shows the switch waveforms. vinegar.

Referring to the figure, a spark gap 2 is shown diagrammatically between the workpiece 4 and the electrode 6. ing. − In the example, the electrode is the opposite of what you want to erode the workpiece into its shape. It is a replica in the form of , and in use, the measured spark gap parameter This allows it to approach the workpiece at a controlled speed.

A first high voltage generator 8 is connected directly to said gap 2. High voltage generator 8 times The path is illustrated in FIG.

Here, the commercial transformer T1 has a primary winding 10 connected to a commercial power source (not shown). have The secondary winding 12 of the transformer T1 has + There are taps supplying 45V, -55V, -155V, and -155V. illustrated As shown above, the +45V tap is connected to one of the inputs to the rectifying and smoothing network 14 of the discharge power supply. Directly connected. The other input to the rectifying and smoothing network 1-4 is illustrated at 16. OV of winding 12, -55V, -155V.

-255V tap can be selected, thereby connecting it to Gap 2. The output of the rectifying and smoothing circuit network 14 is 45V, 100V, 200■, 300■ Among them, DIP (duxl 1nline pack, not shown) age) can be selected as determined by the voltage selection input from the switch. connected to a relay means. Winding 12 is not intended to carry large currents. First, the combined internal resistance of the winding 12 and the rectifying and smoothing circuit 14 reduces the short-circuit voltage of the generator 8. For example, the output power is 0.5 ampere at 300V, or 1 ampere at 100v. It is said that it is limited to A.

Also shown in more detail in FIG. 2 is a second high current generator 16 and a current control circuit 1- A series circuit consisting of 8 is connected to gap 2. The transformer T1 further includes: It has a secondary winding 20 that can carry a large current and therefore has a low internal resistance. So For example, the winding rectifies an open circuit voltage of 45V and a short circuit current of 120 Amps. 45 connected to the input of the high current rectifying and smoothing circuit 22 so as to result in an output of It has an output of V and 0■. The current control circuit 18 consists of a string of parallel transistors, Only one is illustrated in FIG. The current control device is connected to the transistor. A constant base-emitter voltage is applied to the base-collector conductive path at a known temperature. It takes advantage of the transistor's ability to generate a constant current. each transistor By connecting an emitter resistor to the temperature reference diode (temperature Transistor heat sink using e + ele + ence diode) (heat 5 ink) is thermally balanced, the variable (ma + 1ables) ) is controlled (not shown).

A spark time axis generator 24 is installed to control the duty cycle of the discharge machine. , thereby reducing the duty cycle and repeating of the spark time axis in lead 26. The repeat speed can be changed. The spark time axis is parallel FET drive 28 and series FE are input to the T drive 30, and they are each connected in parallel to the gap 2. FET 32 connected in series to the high current generator 16 and the current control circuit 18. It controls the switching means in the form of FET34, so that in the duty cycle F ET32 becomes an open circuit and I''ET24 works, while the duty cycle When not, FET32 works and FET34 becomes an open circuit.

When not on duty cycle, the gap is as follows: a) FET32 b) isolated from the high voltage end of power supply 16 by FET 34;

In the duty cycle, first a certain high voltage is selected to open the gap 2. supply a line voltage, e.g. 300v. High current voltage at the beginning of the duty cycle A Schottky diode 36 is placed there to prevent reverse current from flowing at the source. connected in series. High voltage causes rapid sparks between workpiece and electrode is blown away, which causes a rapid increase in current, which is caused by the high voltage generator 8 The gap voltage is rapidly lowered to 45V for regulation characteristics. schottky As soon as a voltage is applied to the diode 36 in the forward direction, the current control means 18 A high current source that supplies most of the gap current up to 120 amps, determined by A discharge current is also supplied by generator 16 . The voltage applied to gap 2 is Sensed by servo control signal circuit 38, the resulting control signal is Adjust the position of the electrode relative to the workpiece so that the voltage applied to the top is adjusted to 27V. used to control the position. When the voltage applied to the gap is higher, the voltage The pole is brought closer to the workpiece. The voltage applied to the gap is lower than 27V When this happens, either stop the electrode from approaching the workpiece or move it back. servo control The signal also passes through drive 40 to the voltmeter and through drive 42 to the voltmeter. It is fed into the speaker and provides a visual and audible indication of the condition at the gap.

The gap current is selected from a DIP switch (not shown) and its setting (t elling) is decoded by the digital-to-analog converter 44. ), and then the bases of the transistor banks of the current control circuit 18 are Provides input to driving circuit 46.

Since the gap current is constant at a given setting, it also allows the generator Since a constant voltage drop at 16 is determined, if the gap voltage is too low, the current A higher voltage drop in the string of transistors of the control circuit 18 and therefore in that part means heat dissipation. The low gap voltage allows the servo control to move the electrode away from the workpiece. (or at least stop it from approaching), but the reaction is very It is slow and cannot protect the current control transistor. To protect the gap voltage (essentially) disconnects the node between FET 34 and the current control circuit by arc extinguishing circuit 48. The signal is sensed on the lead 50 and compared to a variable reference signal on lead 50. The arc extinguishing circuit has changed. If the output of converter 44 is set to zero, the arc will be extinguished until the gap voltage is restored.

The switching waveforms are shown in FIG.

Other digital inputs (not shown) to the digital-to-analog converter It can be automatically repeated based on input from the time axis. In this way, for example, 1 :2.4 or 1.4:16 current may be supplied, or a pseudo A random digital sequence generator is indexed by time axis (1ndex ed) so that the input to the digital-to-analog converter is a pseudo-random sequence. You can do it as well. Experiments have shown that such an arrangement allows fine finishing, For example, a conventional machine capable of handling 2 amperes of current may be capable of handling much higher currents, even could be achieved with a conventional machine at a working speed corresponding to 30 amperes. Rukoto has been shown. The invention is not limited to the embodiments shown here.

For example, the tap of the secondary winding 12 of the transformer is 0.60V (ac), 155V (ac), 220V (ac), and that of the secondary winding 2° is 18V (ac) N, 18V(ac)N, or 18V(ac)N.

and pulse generator Series FET drive Parallel FET drive FIG.3 6rTlnOOri/nnQ77 Continuation of front page , LU, MG, MN, MW, NL, No, PL, RO, RU, SD, SE, 　US (72) Inventor Dosage, Taipari United Kingdom, Midorisex, 100 H.G., Pillingdon, G. United Kingdom, Pax Nisel 24 Days, Stoke Porges, Pa. Inload

Claims (10)

[Claims] 1. A relatively low short-circuit output current and a first power source having a relatively high open circuit output voltage; and a first power source having a relatively high open circuit output voltage; Relatively low open circuit output voltage and relatively high short circuit output current to maintain spark discharge between the electrode and the workpiece to erode the workpiece. A discharge machine that generates a spark in a spark gap, wherein the first and second power sources are connected in parallel during the duty cycle, the high load output of said first power supply; reverse current in the second power supply when the voltage is higher than the high load output voltage of the second power supply; A discharge machine characterized in that it is equipped with a means for preventing the flow of. 2. when the load output voltage of the first power supply is higher than the high load output voltage of the second power supply; The means for preventing reverse current from flowing in the second power source is the output of the second power source. A claim characterized in that it consists of one or more diodes arranged in series with The machine described in item 1. 3. a first switch means in parallel with the spark gap, a second switch means in series with the output of the second power supply; switch means for opening said first switch means and for opening said first switch means in a duty cycle; closing the second switch means and closing the first switch when not on duty cycle; switch control means for closing the means and opening the second switch means; A machine according to claim 1 or 2, characterized in that: 4. The first power source is adjusted to supply any one of a plurality of different discharge voltages. Claim 1, 2 or 3, characterized in that it has means for making it possible to The machine described. 5. transistor means having a control conductive path in series with the output of said second power supply; A current control is applied to the control gate of said transistor means to determine the current in the conductive path. Claim 1, 2, 3 or 4, further comprising means for supplying a signal. machine. 6. the current control signal between one duty cycle and the next; 6. Machine according to claim 5, characterized in that it has dynamically varying current control means. 7. The current control means controls transistor means that generates a periodic current. 7. Machine according to claim 6, characterized in that the machine is arranged so as to 8. The current control means comprises a pseudo-random series arranged to determine a control signal. a pseudo-random sequence of output currents from said second power supply; 7. The machine according to claim 6, wherein the machine generates . 9. a first power supply having a relatively high open circuit output voltage and generating a relatively low short circuit output current; sparks between the workpiece and the electrode, and the relatively low open circuit output voltage. A second power supply with high voltage and a relatively high short-circuit output current until the end of the machining process is used. by a spark discharge consisting of maintaining a spark between the workpiece and the electrode. A method of processing a workpiece, the method comprising: processing a workpiece during a duty cycle; Two power supplies are connected in parallel, and the high load output voltage of the first power supply exceeds that of the second power supply. A method characterized by preventing reverse current from flowing in the second power supply when exceeding the second power supply. . 10. When the load output voltage of the first power supply is higher than that of the second power supply, the second In order to prevent reverse current from flowing in the power supply, one or more wires are connected in series with the output of the second power supply. 10. A method according to claim 9, characterized in that arranging two or more diodes.