US3439146A - Protective system for electro-erosion metalworking - Google Patents

Protective system for electro-erosion metalworking Download PDF

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Publication number
US3439146A
US3439146A US560503A US3439146DA US3439146A US 3439146 A US3439146 A US 3439146A US 560503 A US560503 A US 560503A US 3439146D A US3439146D A US 3439146DA US 3439146 A US3439146 A US 3439146A
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United States
Prior art keywords
erosion
relay
electrode
feed arrangement
electro
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US560503A
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English (en)
Inventor
Werner Ullmann
Franco Donati
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Agie Charmilles SA
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Agie Charmilles SA
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23H—WORKING OF METAL BY THE ACTION OF A HIGH CONCENTRATION OF ELECTRIC CURRENT ON A WORKPIECE USING AN ELECTRODE WHICH TAKES THE PLACE OF A TOOL; SUCH WORKING COMBINED WITH OTHER FORMS OF WORKING OF METAL
    • B23H1/00—Electrical discharge machining, i.e. removing metal with a series of rapidly recurring electrical discharges between an electrode and a workpiece in the presence of a fluid dielectric
    • B23H1/02—Electric circuits specially adapted therefor, e.g. power supply, control, preventing short circuits or other abnormal discharges
    • B23H1/024—Detection of, and response to, abnormal gap conditions, e.g. short circuits
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23H—WORKING OF METAL BY THE ACTION OF A HIGH CONCENTRATION OF ELECTRIC CURRENT ON A WORKPIECE USING AN ELECTRODE WHICH TAKES THE PLACE OF A TOOL; SUCH WORKING COMBINED WITH OTHER FORMS OF WORKING OF METAL
    • B23H7/00—Processes or apparatus applicable to both electrical discharge machining and electrochemical machining
    • B23H7/14—Electric circuits specially adapted therefor, e.g. power supply
    • B23H7/18—Electric circuits specially adapted therefor, e.g. power supply for maintaining or controlling the desired spacing between electrode and workpiece

Definitions

  • the present invention relates to an improved protective device or arrangement for electro-erosive metal workinging cooperating with a pulse generator and a reversible electrode feed mechanism for the interruption of arcs in the working gap.
  • the harmful nature of arcs in electro-erosive metalworking is well known.
  • the arc produces a change in structure in the surface of the workpiece to be worked to a depth of millimeters. Additionally, the shape of the work electrode is not accurately reproduced in the workpiece because the arc melts parts of the surface.
  • the present invention is generally characterized by the provision of means responding to current changes in the work gap and means responding only to one direction of the drive 'by which the electrode feed arrangement is actuated, for applying signals to a device connected on the output side of the said means, which device can respond only to the simultaneous presence of the signals and only after a predetermined time.
  • the protective arrangement according to the invention provides the further important advantage that it is so designed and is so adaptable that it can cooperate with any conceivable form of construction of reversible electrode feed arrangement without modifications having to be made to the latter.
  • an electrode feed arrangement incorporating a servomotor which influences the movement of the electrode through a reduction gear.
  • the invention is also applicable to other types of feed arrangements, for example those comprising two servomotors which act on the electrode movement through two reduction gears and a differential gear. Hydraulic and pneumatic electrode feed arrangements are also contemplated. In the latter case, instead of the servomotor or servomotors there is provided an electromagnetic setting device comprising two electric coils for the forward or backward movement of the electrodes.
  • the circuit of the protective device or. arrangement according to the invention is the same as will be hereinafter described.
  • the current supply to the working gap is interrupted and the electrical parameters, such as pulse frequency, the pulse interval ratio, the pulse amplitude and the pulse width which have been set at the pulse generator, are changed.
  • the arc is interrupted and, upon restoration of the current supply, the formation of a further arc is avoided.
  • the electrical parameters may be changed either separately or all together. This may be achieved in accordance with the working operation to be performed (roughing, finishing) and/or in accordance with the materials present as the work electrode and as the tool.
  • FIG. 1 shows the circuit arrangement of the protective device, which consists of the component parts 2, 3, 4 and 6, in combination with a pulse generator 1 and a reversible electrode feed arrangement 5 (for example motor M).
  • This servomotor M may be thought to incorporate an armature and influences electrode movement through a suitable reduction gear, all such components for convenience in illustration being collectively designated by reference character 50.
  • Numeral 50 may be also thought of as representing two servomotors influencing electrode movement through two reduction gears and a differential gear, or, in fact, can be considered as any other suitable electrode feed arrangement, specifically those previously mentioned, such as pneumatic or hydraulic drives having electromagnetic setting or adjustment means.
  • Pulse generators having no storage members are known, and therefore only a part of such a pulse generator 1 is shown.
  • reference numerals 100 and 101 denote the electro-erosion current circuit which terminates at the electrode 106 and the workpiece 107.
  • the transistor TR1 is connected, as an electronic switch, to the line 100.
  • This transistor TRl which is only shown once, may naturally constitute a number of parallel-controlled electronic switches.
  • Such electronic switch TR1 is actuated by the timer 109.
  • the working gap between the work or working electrode 106 and the workpiece '107 is sufliciently small and the transistor TRl has been brought into the conductive state, there is set up at the work gap a working spark corresponding to the voltage UB applied to the electro-erosion circuit .100, 101.
  • the electrode 106 is pushed more deeply into the workpiece 107 by the reversible electrode feed arrangement 5 in accordance with the amount of material removed from such workpiece 107.
  • This relay 25 which may alternatively be constructed as an electronic switch or transductor, has in its circuit a current-limiting resistor 22, while in parallel with the relay 25 there is connected a Zener diode 23 and a capacitor 24.
  • the Zener diode 23 maintains the voltage in the arrangement 2 at a constant value. This is important because the voltage drop across the resistor 11 fluctuates within wide limits.
  • the capacitor 24 is provided an an integrating member, and consequently the pulsating voltage between the conductors 200 and 201 is converted into a mean value. Only when the capacitor 24 is fully charged does the relay 25 respond or pull up, so that the contacts 2.6 and 27 are connected together. It will thus be apparent from the foregoing that the relay 25 responds only when a sulficiently large current has flowed for a relatively long time across the work gap G between the electrode 106 and the workpiece 107, that is to say, even when an arc is present.
  • the servomotor M of the electrode feed arrangement 5 responds and withdraws the electrode 106 from the workpiece 107. As described in the foregoing, the arc is also pulled along.
  • an armature voltage is set up in such a manner that the junction or connecting point 508 is positive in relation to the junction or connecting point 509. This potential is applied to the component element 4.
  • Connected to the connecting point 508 are a current-limiting resistor 412 and a diode 413, a resistor 415 and the base of the transistor TR2.
  • the conductor 407 is connected to the connecting point 509'.
  • the Zener diode 4'14 maintains the voltage at a constant value.
  • a positive signal is set up at the capacitor 416, with the result that the base of the transistor TR2 is positive.
  • the npn-transistor TR2 is thus rendered conductive in its collector-emitter path.
  • a negative potential passes through the resistors 419, 420 to the base of the npn-transistor TR3, so that its collector-emitter path is blocked or rendered non-conductive.
  • the electromagnetic relay responds or pulls up through the conductor 406, the resistor 424, the transistor TR4 and the conductor 407, and connects the contacts 43 and 44.
  • This relay 45 may of course be an electronic switch or a transductor.
  • a relay valve 39 Connected in parallel with this memher is a relay valve 39, the anode circuit of which includes an electromagnetic relay 310. As soon as the capacitor 38 has been charged, the relay valve 39 constructed as a glow discharge lamp ignites, whereby the relay 310 is pulled up or responds. The control voltage of the whole electroerosion installation is present at the conductors 104, 105.
  • the electro-erosion installation is de-energized.
  • an acoustic and/or optical warning device denoted by reference numeral 311
  • an automatic device 6 is energized, which changes the electrical parameters such as, for example, the pulse repetition frequency, the pulse interval ratio, the pulse amplitude and the pulse width.
  • the automatic device 6 can increase the pressure in the dielectric liquid and the level of this liquid, so that the washing conditions in the working gap are improved.
  • the automatic device 6 may be selectively set in operation upon attraction of the relay 310 as a result of appropriate construction of the contact 35 of the aforesaid relay.
  • the relay 45 is de-energized through the transistors TR2, TR3, TR4 and also falls off.
  • the relay 310 which may be an electronic switch or a transductor, has fallen off, the voltage UB is restored at the pulse generator 1.
  • the servomotor M rotates in the forward direction, i.e. the electrode 106 is again fed forwards in the direction of the work gap G, until normal working pulses are again set up.
  • the relay 25 pulls up again, and as soon as the servomotor M iS reversed again owing to the arc, the relay 45 also begins to pull up. Consequently, the main voltage UB at the pulse generator 1 is again interrupted by the attraction of the relay 310. This cycle may be repeated a number of times, but in practice it is found that, owing to the changes of the electric parameters at the pulse generator 1 and of the washing conditions of the dielectric liquid in the working gap (no further arc can be formed when the whole installation is restarted by the relay 310.
  • the box denoted by reference numeral 6 contains an automatic control device for the pulse generator 1 and the circuit of the dielectric liquid.
  • the circuit is not shown because it is known as such in erosion machines.
  • the automatic control device 6 changes the electrical parameters set up at the pulse generator 1, such as the pulse frequency, the pulse interval ratio, the pulse amplitude and the pulse width, after response of the whole protective arrangement, i.e. after occurrence of an arc.
  • the automatic control device 6 consists of known switching parts, such as a programing device, an electronic counting circuit or a stepby-step selector.
  • the programing device may be an astable multivibrator which, according to the desired program, applies a predetermined number of pulses to the step-by-step selector or to the electronic counting circuit consisting of bistable multivibrators. In the case of the latter, the number of bistable multivibrators present is equal to the desired number of counting stages.
  • the output of each counting stage is connected to the control input of one of the aforesaid electrical parameters in the pulse generator 1 and the conveyor pump in the circuit of the dielectric liquid. The same applies to the outputs when a step-by-step selector is employed instead of the elec tronic counting circuit.
  • control device 6 When the relay 310 in the device 3 has pulled up on occurrence of an arc in the work gap G and simultaneous reverse running of the electrode feed arrangement 5, the control device 6 is energized by the contacts 35. It is to be noted that the control device 6 need not in all circumstances be associated with the protective arrangement. It may be optionally added to the protective arrangement as an advantageous improvement.
  • the programming apparatus in the control device emits a number of pulses pre-set in the programing arrangement by an operator, for example by means of a normal telephone dial.
  • the operator can thus pre-set by means of the dial the changes required at the pulse generator 1 or in the circuit of the dielectric liquid after the occurrence of an are, so that when the relay 310 falls off (restarting of the Whole erosion installation) no further arcing can occur.
  • Fixedy associated with each output of a counting stage within the electronic counting circuit or the step-bystep selector is a control input for the electrical parameters at the pulse generator 1 and for the liquid circuit.
  • the desired outputs are selected in turn.
  • the potential change occurring at the selected outputs produces a change of the electrical parameters and washing conditions which have been set in the pulse generator 1 and in the liquid circuit before the response of the whole protective arrangement.
  • the change takes place in a particular ratio in relation to the value originally set.
  • the pulse width may be reduced by 10 percent and/ or the operating voltage UB raised by a few percent and the liquid pressure may 'be raised by a few percent.
  • the change fed into the programing arrangement is one which affects only those control quantities which, as shown by practical experience, may greatly favor restriking of the are after restarting of the whole erosion installation, or which obviate the causes of the arc.
  • the protective arrangement according to the invention protects the whole electro-erosive working installation in such a manner that protracted arcs cannot give rise to any danger. This is particularly important because a number of electro-erosion installations are attended to by one operator or the installations are operated at night.
  • the protective arrangement thus makes it possible for the electro-erosion installations to be run without supervision while optimum efiiciency is maintained in regard to removal of material.
  • resistor 11 provided in the erosion circuit in the work gap G to tap the input voltage
  • coil current transformer
  • a protective device for interrupting arcs in the work gap defined by the electrode and workpiece of the erosion circuit, said protective device comprising means responding to current changes at the work gap, means responding only to one direction of driving of said electrode feed arrangement, and means for receiving signals from said current change-responding means and said means responding only to one direction of driving of said reversible electrode feed arrangement, said signal receiving means only being actuated upon simultaneous presence of signals from both said current change-responding means and said means responding only to one direction of driving of said reversible electrode feed arrangement and only after a predetermined time.
  • said current change-responding means comprises a control circuit incorporating a Zener diode for maintaining constant, and a capacitor for integrating, the pulsating input voltage tapped in the erosion circuit.
  • said electrode feed arrangement comprises a drive incorporating a servomotor with a reduction gear.
  • said electrode feed arrangement comprises a drive having two servomotors with a differential gear.
  • said electrode feed arrangement includes a hydraulic drive having an electromagnetic adjustment element.
  • said electrode feed arrangement includes a pneumatic drive having an electromagnetic adjustment element.
  • said servomotor includes an armature, said means responding to only one direction of driving of said electrode feed arrangement being connected on the input side to said armature of said servomotor and comprising a switchlng relay, a Schmitt trigger and a transistor actuating said switching relay.
  • said electrode feed arrangement includes a fluid control valve having an electromagnetic coil, said means responding to only one direction of driving of said electrode feed arrangement being connected on the input side to said electromagnetic coil and comprising a switching relay, a Schmitt trigger and a transistor actuating said switching relay.
  • said electrode feed arrangement incorporates a servomotor
  • said means responding to only one direction of driving of said electrode feed arrangement incorporates a Zener diode for maintaining constant, and a capacitor for integrating, the armature voltage of said servomotor.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Electrical Discharge Machining, Electrochemical Machining, And Combined Machining (AREA)
US560503A 1965-07-15 1966-06-27 Protective system for electro-erosion metalworking Expired - Lifetime US3439146A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CH996865A CH438519A (de) 1965-07-15 1965-07-15 Funkenerosionseinrichtung mit reversierbarem Elektrodenvorschub

Publications (1)

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US3439146A true US3439146A (en) 1969-04-15

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US560503A Expired - Lifetime US3439146A (en) 1965-07-15 1966-06-27 Protective system for electro-erosion metalworking

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US (1) US3439146A (enrdf_load_stackoverflow)
AT (1) AT258431B (enrdf_load_stackoverflow)
CH (1) CH438519A (enrdf_load_stackoverflow)
DE (1) DE1565388C3 (enrdf_load_stackoverflow)
GB (1) GB1120292A (enrdf_load_stackoverflow)
SE (1) SE340211B (enrdf_load_stackoverflow)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2063115A1 (en) * 1969-04-02 1971-07-09 Inoue K Servo-system for electro-machining
US3654420A (en) * 1970-08-14 1972-04-04 Mitsubishi Electric Corp Apparatus for shaping a workpiece by electrical discharge with detection means for stopping the shaping operation under abnormal conditions
US4628171A (en) * 1985-01-11 1986-12-09 Port City Machine & Tool Company Mechanical feed EDM machine for making threaded and nonthreaded bores

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3597570A (en) * 1968-05-27 1971-08-03 Mitsubishi Electric Corp Device for detecting sustained arcing across electrospark machining gaps
WO1981002127A1 (en) * 1980-01-22 1981-08-06 Mitsubishi Electric Corp Electrical discharge machining apparatus which detects gap status between electrode and workpiece
US4602142A (en) * 1982-06-30 1986-07-22 Mitsubishi Denki Kabushiki Kaisha Electric discharge system including means to normalize the interpole gap to minimize abnormal discharge conditions

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3183397A (en) * 1963-02-28 1965-05-11 Cincinnati Milling Machine Co Motor control apparatus
US3288693A (en) * 1963-07-23 1966-11-29 Exnii Metallorezhushtchikh Sta Method for automatically controlling electrode device feeding in electric erosion machines and an arrangement to carry out this method

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3183397A (en) * 1963-02-28 1965-05-11 Cincinnati Milling Machine Co Motor control apparatus
US3288693A (en) * 1963-07-23 1966-11-29 Exnii Metallorezhushtchikh Sta Method for automatically controlling electrode device feeding in electric erosion machines and an arrangement to carry out this method

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2063115A1 (en) * 1969-04-02 1971-07-09 Inoue K Servo-system for electro-machining
US3654420A (en) * 1970-08-14 1972-04-04 Mitsubishi Electric Corp Apparatus for shaping a workpiece by electrical discharge with detection means for stopping the shaping operation under abnormal conditions
US4628171A (en) * 1985-01-11 1986-12-09 Port City Machine & Tool Company Mechanical feed EDM machine for making threaded and nonthreaded bores

Also Published As

Publication number Publication date
AT258431B (de) 1967-11-27
DE1565388B2 (de) 1975-03-06
DE1565388C3 (de) 1975-11-06
DE1565388A1 (de) 1970-03-19
SE340211B (enrdf_load_stackoverflow) 1971-11-08
GB1120292A (en) 1968-07-17
CH438519A (de) 1967-06-30

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