DD148838A5 - METHOD AND CIRCUIT ARRANGEMENT FOR FEED CONTROL OF SPARK PROCESSING MACHINES - Google Patents

Abstract

The invention relates to a method and a circuit arrangement for feed control of spark machining machines, through which a higher effectiveness is achieved. The object of the invention is to control the feed so that the size of the machining gap remains constant, independently of the respective technological process parameters. In addition, the circuit contains means for automatic short-circuit protection. According to the invention, the voltage is examined and differentiated by means of three comparators, at which the spark discharge takes place. From this, the control variables for the feed are determined via an electronic system, which is then controlled so that the desired constancy of the machining gap results.

Description

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Method and circuit arrangement for feed control of Punkenbearbeitungsmascliinen

Field of application of the invention:

The invention relates to a method and a circuit arrangement for controlling the feeding of thread-type electrode processing machines.

Characteristic of the known technical solutions:

Spark-wire spark-machining machines are known, whose pulse generator is designed as an RC generator, wherein the control of the stepping motor-driven feed takes place as a function of the mean value of the voltage in the machining gap, wherein the control system comprises a device for determining the speed of the feed at a fixed value. for a

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contains certain workpiece, and the speed is automatically controlled within narrow limits around the setpoint.

These punch machining machines have the disadvantage that the stability of the machining gear is not maintained during the entire machining period, in particular when machining a workpiece with a variable cross section.

can be obtained, since the mean value of the stress in the machining gap, which ensures the constant maintenance fluctuates in a range whose limits by two to three orders of magnitude smaller than the ratio of the limits of the range in which the speed of the feed in the change of the workpiece cross-section is changed. The method of controlling the feed in relation to the mean value in the machining gap also has the disadvantage that it requires a control system which leads to uninterrupted operations for controlling the speed of feed during the machining of a single workpiece, resulting in a reduction in productivity of the machining process.

Object of the invention;

With the inventive control of the feed, the mentioned disadvantages are to be eliminated.

Explanation of the essence of the invention;

The invention is primarily based on the object, a method for controlling the advance of.Sunkenbearbeitungsmaschinen to design so that the size of the machining gap can be kept at a constant and controlled size, during the entire processing time and irrespective of the selected technological mode ,

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According to the invention, in order to ensure an optimum discharge frequency and to adapt the feed rate to the erosion process quickly, the speed of the process is changed so that the level of each discharge is maintained in a predetermined range. The decision to increase the feed rate to maintain it at a constant value or to reduce it is made dependent on the level of discharges, depending on whether the discharges are at a level above an upper limit, between upper and lower limits, respectively take place below the lower limit of the range. The variation gradient of the speed is directly proportional to the magnitude of the speed with which the feed is carried out at the moment when the decision to change this speed is made. In order to rapidly adjust the speed of the feed to the speed of the erosion process to accommodate a sudden increase in the workpiece cross section without external interference during machining, the feed after the short circuit ceases at a speed commencing at the beginning of a short circuit becomes the lower limit of the speed change as close as possible, resumed, and finding the optimum speed for the new Arbeitsbedigungen takes place at a small increase in the rate of advance speed. In order to avoid a short circuit during the processing time, the variation rate of the feed rate at a given time is greater in its waste than in its increase.

For purposes of determining the sense of change in feed rate, i. so that the level at which the electrical discharge takes place is constant and as high as possible, contains the circuitry for control

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of the feed according to the invention, a logical system that makes logical decisions and consists of three voltage comparators. It also includes a circuit for detecting the instant in which the voltage between the electrodes exceeds the first predetermined level, a circuit that makes the decision to reduce the feed rate for the pail, that the electrical discharge takes place at a voltage whose value is below the second predetermined level, a circuit for detecting the moment in which the voltage between the electrodes exceeds the second predetermined level, a circuit that makes the decision to keep the feed rate constant in the case where the discharge takes place at a voltage which is between the second and third predetermined levels, a circuit that makes the decision to increase the feed rate for the pail, that the electrical discharge takes place at a voltage above the third predetermined level, and a circuit for issuing d It commands to change the feed rate by the system to form the corresponding feed control quantity in the sense of increasing, decreasing or keeping constant the same. For the purpose of constituting the feed speed, it further includes a clock generator which controls a direct counter and a reversible counter controlled in response to the logical speed change decision, a coincidence circuit for the digits set in _m , a deletion circuit in FIG Coincidence moment in the direct counter entered numeral and a circuit for detecting the beginning of a Kursschlusses, which consists of a system for counting after each discharge of the pulses generated by the clock generator. Furthermore, a gate is provided, ie the achievement of a maximum digit

detected, if a short circuit starts and which controls a circuit for writing a number in the reversible counter, which corresponds to a small feed speed and on the other hand controls a block for placarding a short circuit in the machining gap. In order to maintain a certain variation slope of the feed rate, which is proportional to the speed in the view where the change decision is made, the control circuit includes a gate which supplies the pulses obtained at the output of the coincidence circuit to the input of the instruction distribution circuit Feed rate variation depending on the decision made and the other to a monostable multivibrator to form the control pulses for the electromechanical feed system supplies. In order to avoid a short circuit during the processing time, the control system on the web for controlling the speed increase of the feed contains a frequency pulse divider which alters the numbers inscribed in the reversible counter to establish the prescribed speed.

In order to detect the presence of the short circuit in the working space by means of an auxiliary voltage applied to the electrodes and to switch off the working voltage from the electrodes during the short circuit test, a monostable multivibrator is triggered at the moment in which the short circuit between the electrodes has been detected Transistor drives, having in the collector circuit a relay whose contacts apply the test voltage to the electrodes and controls the locking of the power transistor of the generator by means of an electrical switch. The relay is connected by means of a logic UIID function circuit which combines the presence of the short circuit and the test condition.

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held during the short circuit in the test state.

In order to detect the presence in the short circuit machining gap by means of an auxiliary voltage applied to the electrodes and to disconnect the working voltage from the electrodes during the Kurzschlußprufung, at the moment in which the short circuit between the electrodes was detected, a monostable multivibrator is driven, the one Flip-flop circuit for storing the occurred Kurzschlußzugtandes on the one hand, on the one hand a transistor that applies the test voltage to the electrodes controls and on the other hand via a logic gate an optoelectronic coupler drives the locking of the power transistor of the clock generator controlled by the electronic switch. The circuit is maintained in the test position for the duration of the short circuit by means of a transistor which also passes the test voltage applied to the electrodes to the base of another transistor which saturates at the moment the short circuit disappears and thereby the reconnection of the transistor Operating voltage which causes the return to the initial position of the flip-flop circuit for storing the short-circuit state when a predetermined level is exceeded.

Explo sation example:

An exemplary embodiment of the invention will be explained in more detail below with reference to FIGS. 1, 2, 3, 4. Show it:

1: the block diagram of the control system and the clock generator,

2: the block diagram of the circuit decisions making the logical decisions

 '.' group,

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Pig, 3 and 4: Embodiment of the circuit unit for short circuit testing in the working space.

In Pig. 1, the block diagram of the control system of the feed and the pulse generator is shown. For example, assume that the feed is effected by a stepper motor system, i. the feed rate is proportional to the frequency of the motor control pulses. The pulse generator consists of a transformer rectifier set TR, a power transistor T- ,, a limiting resistor Rn and a capacitor C-j, which discharges in the working space formed between the filamentary electrode 1 and the workpiece 2. The pulse charging of the capacitor C-, is backed up by the control by means of a multivibrator 3, which is connected by means of an electronic switch 4 to the base of the power transistor T- ^. The decoupling of the multivibrator 3 from the base of the transistor T-, and its locking in the Palle of the occurrence of a short circuit in the workspace and Palle the interruption of the processing process at the end of the work program or the disappearance of the normal working conditions of the machine automatically. The voltage between the filamentary electrode 1 and the workpiece 2 is divided by means of a resistive divider R2, Ro and the input of the logical decision system SL, which is shown in Pig. is shown supplied.

The logical system SL examines the IT level at which each discharge takes place in the working space and, depending on this level, makes the decision on an increase in the speed of the feed at the output EH, via a reduction in the speed of the feed at the output E-. or by keeping the speed constant at the output E ₀ .

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The formation of the variable frequency pulses for controlling the stepper motors is accomplished by a circuit consisting of a direct counter HD .., a reversible counter NR and a co-occurrence circuit Cc for the counters HD. and NR inscribed digits secured. At the input of the counter HD., The pulses generated by a clock generator CT are introduced by means of an ITICHT gate CL ₁ . If any digit is written in the counter ITR, the coincidence circuit Cc controls at the moment when the counter HD. counted number of pulses coincides with the number inscribed in the counter HR, a flip-flop circuit CBB ₁ on. The flip-flop circuit CBB ₁ then controls by means of a HAITD gate CLp a monostable multivibrator CBI / L, which serves to form the necessary to control the stepper motors pulses of appropriate duration. The output pulse of the gate CLp v / ird is supplied to one of the inputs of the reversible counter HR by means of a UHD gate CL ~ depending on the decision made by the logical system SL decision. The gate CL ^ is locked in the case where the logical system SL decides to keep the speed of the feed constant, and in this case the number written in the reversible counter HR remains unchanged, thus obtaining at the output of the monostable multivibrator CBLL Pulses with constant frequency. The flip-flop circuit CBB ₁ causes the deletion of the counter HD ₁ after detecting each coincidence.

When the logical system SL decides to increase the speed of the feed, that is, to increase the frequency for controlling the stepper motors, a logic signal appears at its output E ^, which by means of a flip-flop circuit CBB _{2 is} an UlTD-Tor-CL , opens, whereby the output pulses of the gate CLp via the gates CLo, CL., CL, - and a frequency divider 5 the counter input

counter UR are transmitted in the reverse sense. The ITAiID-TOr CL, - is locked when the number reaches the minimum prescribed value corresponding to the largest frequency with which the stepping motors can be controlled. The arrival of the smallest number written to the counter IJR is detected by means of a read circuit for the states of the counter IT _m .

If a reduction in the speed of the feed, ie a reduction in the frequency for controlling the stepper motors is effected by the logical system SL, appears at its output Er, a logic signal which opens a UHD gate CLg by means of the flip-flop circuit CBB ₂ , so that the output pulses of the gate CLp via the gates CLo, CLg and a UAITD gate CL _? be transmitted directly to the counter input of the counter ITR. The CLy is latched when the number written to the ITR counter has reached the maximum prescribed value corresponding to the minimum frequency with which the stepping motors can be controlled. The arrival of the largest number written in the counter ITR is detected by means of a read circuit for the states of the counter IT ^.

The logic system SL outputs at its output a logic signal Eg which unlocks the gate CL ^ when a decision is made to keep the stepper motor control frequency constant.

The Ausgangsinroulse the clock generator GT are using

also

an ITICHT gate CL _Q and a HAlTO gate CLq to the input of the counter ITD ₂ transmitted. The pulses generated by the clock generator GT are counted by the counter ITD ₂ (only) after each discharge. At the moment, at dom, the voltage at the terminal of the discharging capacitor C-, (after he has given his energy to the working space) a

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reaches a certain level, the logic system SL acts by means of the logic signal which occurs at its output B, the deletion of the number written in the counter ND _P.

If the terminal voltage of the capacitor C-, after discharge no longer reaches the predetermined level after a long time, so the clear signal of the counter is no longer present, the number of pulses written into the counter p reaches a certain value, which by means of an ITAlTO gate CL ₁₀ is detected, whereupon the door CLp is locked. At the same time, the output signal of the gate CL, _Q causes the presence of a short circuit in the working space by "locking the power transistor T-, by means of a short-circuit test block BTS, the circuit diagram in the Pig. 3 and 4 is shown.

If the presence of a short circuit in the working space is determined by means of the course check block BTS, a logic signal which controls the return of the filamentary electrode appears at the output E. and at the output E 1. the control for locking the power transistor T ^ is maintained.

The logic output of the door CL-.Q, which occurs in the event of a short circuit in the working space, controls the Einschräjebung a number in the counter HR with a maximum approximated Y / ert by means of a write-6, whereby the feed after the disappearance of the short circuit in Workspace is resumed at a speed approaching the lower limit.

When the short circuit in the working space disappears, which is detected by the short circuit test block BTS vmrde, the

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Coupling the multivibrator 3 to the base of the transistor T ₁ , at the output B of the logic system SL the clearing signal of the counter M ^ appears, the gate CLg is unlocked, and at the output of the inonostable multivibrator CBSiL appear very low frequency pulses for stepper motor control, which allows the resumption of feed with a speed approaching the lower limit.

In Pig. 2 is the logical system SL which makes the decision about a possible change in the speed of the feed. At the input I _{1 of} the logic system SL, the electroerosive discharge pulses are introduced between the filamentary electrode 1 and the workpiece 2, which are divided by means of the resistance divider R ₂ »R-. These pulses, which follow an exponential function, are fed to the inputs of three voltage level comparators A, B, C; the smallest level is detected by comparator A and the largest ITiνeau by comparator C.

If the charge of the working capacitor C has started, the level predefined on the comparator A is exceeded at a certain point in time, at its output a logic level 1 reversed by a NOT gate CL ₁₁ is maintained. In this sequence, the comparators B and C have a logic level 0 _e at the output. The transition of the pulse at the output of the comparator A from 0 to 1 results in the flip-flop formed by the two NOT gates CL ₁ P and CL ₁ -3. Circuit in the state of the logic level 1 at the output of the door CL ^ over. The control pulse of this flip-flop circuit is supplied to one input of a delay circuit R ^ Cp by means of a circuit consisting of the NOT gate CL ₁₄ and CL ₁₅ and the NAND gate CL ₁ ^. The logic signal 0 at the output of the gate CL ₁₁ , which when exceeding the comparator A

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detected levels is supplied to a NAHD gate CL ^, at the output then a logic signal 1 occurs. If the discharge takes place in the working space before reaching the level detected by the comparator B, a logical signal 0 occurs at the output of the gate CL-, ~, since the comparator A is in the state 0 and the gate CL 1, 1 passes. The logic signal O at the output of the gate GL-, rj causes the transition of the flip-flop circuit, which consists of the NAIiD T ore η CL-, η and CL-, "in the state with the logic signal 0 am Exit of the door CL, <->. As a consequence, in the event that the discharge in the working space takes place under the Niejyau ^ f detected by the comparator B, a logical level 0 appears at the output Er of the logical system, which means that a decision has been made to reduce the technological advance.

If the charge of the capacitor Cx exceeds the level set at the comparator B after exceeding dea at the comparator A of predetermined level, then at the output of the comparator B a level 1 is reached, which is reversed by a NAND gate CLpQ. As a result, the logic level 1 is maintained at the output of the comparator A and the logical level 0 at the output of the comparator C,

The logic level 0 at the output of the gate CL ₂ Q generates a logic signal 1 at the output of the gate CL-, "· When transition of the comparator B from state 0 to state 1, the flip-flop circuit consisting of the two NAND Doors CLg- ^ and CL22, in a state with the logic level 1 'at the output of the door CLp pass. The control pulse of this flip-flop circuit by means of a scarf device consisting of the non-ports CLp-, and CL ₃ . and from the NAND gate CL ₂ c> having an 'delay circuit R5C0 on an input.

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If the discharge takes place in the working space before reaching the level detected by the comparator C, a logic signal is obtained at the output of a NAND gate CL ₂ g which comprises a flip-flop circuit consisting of the two NAND gates CLp~ and CLpo a state with the logic level 0 at the output of the gate CLgg added. Accordingly, when the discharge in the working space takes place at a level which is between the predetermined levels for the comparators B and C, a logic signal 0 is obtained at the output Eq of the logic system SL, which is a decision to control the feed for the Yfert, whom he had before unloading, corresponds.

If the charge of the working capacitor C- exceeds the predetermined level by the comparator B also exceeds the predetermined level by the comparator C, occurs at the output of the comparator C, a logic level 1, which is reversed by a NOT gate CL ₂ g becomes. At the output Hr of the logical system, a logic level 0 is obtained, which corresponds to a decision to increase the feed. The AND gate CL ~ q serves to put the output of the gate CL ^ g in the logic state 1 and that gate CL ^ g by means of the two gates CLpi ^unc ^ ^ o? ^ ^It "t ^e ^ ^s to lock the flip-flop circuit, provided that the discharge of the capacitor Cj ^ at a voltage is used as the comparator is greater by G or smaller than the detected level from the comparator B.

At the output E »of the logic system, after each discharge, i. after each drop in voltage between the electrodes below the level set by the comparator A, a logic signal 0 is obtained. The logic signals appearing at the outputs Ej, Eg, Eu and E ^ are still required by the circuitry for frequency forming the pulses needed to control the stepping notches

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are, taken over. The stepper motors were included in the explanation of Pig. I already mentioned.

In Pig. 3 shows a first embodiment of the block BTS for short-circuit testing in the working space. Here, the electrical resistance of the working space is checked by means of an auxiliary voltage, which was supplied via relay contacts. The output signal of the door CL-.Q from Pig. I is fed to the input Ig of the test block BTS. The signal at the input I _{0 of} the test block has a logic level 0 when, after a discharge caused by the attainment of a logic level 0 at the output E ^ of the logical system SL according to Pig. 1 detects that the voltage between the electrodes is not restored by the comparator A according to Pig. reaches predetermined level after a predetermined time. It thus provides the possibility that the counter ND2 (Pig.1) is brought into the state in which it generates a logic signal 0 at the output of its Tora CL, q.

The signal at input I.- is reversed by a NOT gate CL., -, and a monostable multivibrator CBBIg is triggered, which latches a transistor Tp for a certain time, V7a the closure of the contacts of a relay d and Apply the test voltage U- ^ to the two electrodes. At the same time, the power transistor T-J ^ is locked by means of the electronic switch 4 (Pig. I) by the logic signal 1 reached at the output E 1 of the test block BTS.

If there is a short circuit in the working space, a transistor T 1, which is connected in parallel with another transistor T 1, is latched, whereby the transistor T, in turn, is latched by means of the contact of the relay d. The logic level 1, which then occurs at the collectors of the transistors ToV and T *, causes the locking of the transistor Tg by the saturation of a

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another transistor T ₁ -. The logic signal 1 obtained at the output E of the test block BTS represents the confirmation of the presence of a short circuit in the working space. It controls the return of the filamentary electrode by means of a control system of the stepping motors SCMPP represented by a dashed line in FIG are, however, outside the scope of the present invention. When the short circuit disappears, the transistors Tp and T are saturated, the relay d opens its contacts, whereby the voltage U ₁ is switched off by the electrodes and the multivibrator 3 is coupled to the base of the transistor 1 by means of the electronic switch 4 (Pig becomes.

Another embodiment of the short-circuit block BTS, in which the electrical resistance in the working space is checked by means of an auxiliary voltage applied to the electrodes by means of transistors, is shown in Pig. 4 shown.

The logic signal 0 at the input Iq of the test block BTS, which is negated by the gate CL, .., causes the triggering of the monostable multivibrator CBMg »which drives a flip-flop circuit CBB-. If, after a discharge, the level determined by the comparator A (FIG. 2) is not exceeded for a certain time, a logic signal 1 occurs at the output of the flip-flop circuit CBB-, which is supplied via a UHD gate CL ^ ₂ saturates the transistor of an opto-electronic coupler Tg. At the output E., of the test block BTS is then obtained a logic signal 1, which locks the power transistor T .. of the generator by means of the electronic switch 4. At the same time, the command for saturation of two transistors T " and T _{Q is given} by means of a switch 7 for the logic pulses. If there is a short circuit in the working space, another transistor Tq remains locked, and the transistor Tg of the opto

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Kopplers remains saturated by means of a Umpolers 8 for the logical pulses. At the output E of the test block BTS, the command for returning the thread-like electrode to the contour of the workpiece is given.

At the moment of the short circuiting in the working space, the transistor Tq is saturated and at the output of the gate CL ^ ₂ v / ird a logic signal O is obtained, which locks the transistor Tg of the optoelectronic coupler. As a result, the working voltage is applied cynically to the filamentary electrode and the workpiece. When the level set at the comparator A is reached, the ¹ flip-flop circuit CBB. Goes to the state 0 with its output, and zv? Ar due to the logic signal 1, which is at the output E ». of the logical system SL and which is reversed by the IJICHT gate CL ^. In this way, the short-circuit test block BTS is put in the wait state by means of the transistors Τγ and Tg at whose base the lock is controlled.

The invention has the following advantages:

- First, it ensures increased productivity of the machining process,

- Second, it ensures the constant maintenance and the controlled maintenance of the working space during the entire processing time by the constant maintenance of the level of the discharge voltage

Third, it provides excellent process stability, regardless of the cross-sectional variations of the workpiece, without the need for operator intervention during machining.

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Claims (6)

21.8 706 invention claim Method for controlling the advance of spark machining machines, characterized in that, in order to maintain the machining gap at a constant and controlled size during the entire processing period, independently of the selected technological operation,
for the purpose of providing a maximum discharge frequency and for quickly adapting the feed rate to the speed of the erosion process
Feed is changed so that the level of each discharge is obtained within a predetermined range,
wherein the decision is made to increase the feed rate, maintain it at a constant value, or reduce it as a function of the level of discharge, either at a level above or between the upper limit
upper and lower limits or below the lower limit, and that the fall in the change in speed is directly proportional to the magnitude of the speed with which the feed at the moment in which the
Decision to make their change. Method according to item 1, characterized in that, for the purpose of rapid adjustment of the speed of the feed to the speed of the erosion process, in order to adapt to a sudden increase of the workpiece cross-section without external intervention, upon the occurrence of a short circuit, the resumption of the feed after the elimination of the short circuit a speed approaching its lower limit of variation as much as possible, while determining the optimum speed for the new working conditions with a small rate of increase in the speed of the technological feed. - 18 - 21 8 706 3. The method according to item 1, characterized in that in order to avoid a short circuit during the loading • the variation in the rate of advance at a given point in time is greater in terms of its reduction than in terms of its increase. 4. A circuit arrangement for carrying out the method according to item 1, characterized in that they for the purpose of determining the sense of change in the feed rate, that is to keep constant the level at which the electrical discharge erosion / on a maximum value, a logical system (SL) for making logical decisions, which consists of three voltage comparators (A; B; C), that a circuit for detecting the instant in which the voltage between the electrodes exceeds the first predetermined voltage level is provided (GL ₁₁ , CL ... , CL .., - * CL..g), that it is a circuit that makes the decision to feed reduction, if the electrical discharge is at a below the second predetermined level voltage value (CL ₁₂ JCL ₁ -, CL-j ·?, CL ₁ Q, C ^ -iq) »a circuit for detecting the instant in which the voltage between the electrodes is the second predetermined level exceeds (CL ₂₀ , CL ₂ -, CL ₂ , CLpr-) »a circuit which makes the decision to keep constant the feed rate in the pallet that the electrical discharge takes place at a voltage lying between the second and the third predetermined level (CL ₂₁ , CL ₂₂ , CL ₂ ,, CL ₂ ,, CL ₂ Q, CL _{0 0} ), a decision making circuit for increasing the feed rate in the Pail, that the EOD at above the third predetermined level (CL ₂ q), and a circuit for distributing the control of the feed rate change to the system for forming the feed rate variable in terms of increasing, decreasing or keeping constant (CBB ₂ , CLg, - ¹⁹ - 21 8 _{5 6} , CL ₇ , H _H , H _m ). Circuit arrangement according to item 4, characterized in that, in order to form the frequency of the control pulses for a feed mechanism, it comprises a clock generator (GT) which controls a direct counter (ND.) And a reversible counter (NR) in dependence on the logical decision to control the speed change, a coincidence circuit (C) for the numbers written in said counters, an erase circuit (CBB ₁ for erasing the number written to the direct counter at the moment of coincidence, a detection circuit for the instant of occurrence of a short circuit, consists of a direct counter (NDp) counting pulses delivered by the clock generator (GT, CLq, CL ~) after every discharge and a NAND gate (CL ^ ₀ ) for detecting the reaching of a maximum number in the event of a Short circuit are provided, on the one hand, a circuit (6) for writing a small feed speed The number of indices corresponding to the number of incompressible counters (NR) and the block (BTS) for the short-term check in the machining gap. Circuit arrangement according to item 4, characterized in that, in order to obtain a variation in the feed rate which is proportional to the speed at the moment the change decision was made, it contains an AND gate (CLp) equal to that at the output of the coincidence circuit (Cc CBB ..) received on the one hand to the input of the circuit for distributing the control signals for the speed change of the feed in response to the decision made (CL-) and on the other a monostable multivibrator (CBLL) to form control pulses for the electromechanical ^ Vor s chub sy st em feed t ♦ - 20 - .20- ^{21 8 706} 7. Circuit arrangement according to item 4 to 6, characterized in that it contains a frequency divider (5) for the purpose of preventing the occurrence of a short circuit during the processing time on the web to control the increase in speed of the feed, the numbers in the reversible counter for fixing the prescribed speed are changed. 8. The circuit arrangement according to item 4, which checks the presence of the short circuit in the working space by means of an auxiliary voltage applied to the electrodes and which shuts off the working voltage from the electrodes during the short-circuit test, characterized in that at the moment of detecting the short circuit between the electrodes a monostable Flip-flop (CBM ₀ ) is driven, which in turn drives a transistor (Tp) having in its collector circuit a relay (d) whose contacts apply the test voltage to the electrodes and the locking of the power transistor (T ₁ ) of the generator by means of the electric Switch (4), wherein the relay for the duration of the short circuit by means of a UHD gate, which detects the presence of the short circuit and the test condition together (T-, T-, Tj-) is kept in the test state. 9. Circuit arrangement according to item 4, which detects the occurrence of a short circuit in the working space by means of an auxiliary voltage supplied to the electrodes and which shuts off the working voltage from the electrodes during the short circuit test, characterized in that at the moment of detecting the short circuit between the electrodes, a monostable multivibrator (CBMp) which is a flip-flop circuit (CBB-), which stores the occurrence of the short circuit, 218 706 which in turn drives, on the one hand, a transistor (T ₇ ) which applies the test voltage to the electrodes and, on the other hand, activates an optoelectronic coupler (T) by means of an AND gate (CL ^^) which locks the power transistor (T ₁ ). the pulse generator by means of the electronic switch (4) is effected, wherein the circuit for the duration of the short-circuit by means of a transistor (Tq) is held in the test position, the further applied to the electrodes test voltage to the base of another transistor (T _q ), which saturates at the moment of the short circuit disappears and allows the supply voltage to be connected, which, when a predetermined level is exceeded, causes the return of the flip-flop (GBS) to store the occurrence of the short to the initial position. 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