JPH021615B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a wire-cut electric discharge machining apparatus, particularly to an improvement in machining fluid supply control.

[Conventional technology]

The wire cut runs a thin wire, uses this as an electrode to supply machining liquid to the machining gap between the workpiece and the object to be machined, and performs machining by generating electric discharge through the machining liquid.

[Problem to be solved by the invention]

Machining fluid is normally jetted from opposing nozzles toward the machining area and flows into the tiny, constantly changing machining gap, so that a sufficient amount of fluid is always stably distributed at a sufficient flow rate. It's difficult.

The machining fluid jetted into the machining gap becomes a discharge medium and serves as a cooling means, but if the flow rate decreases, the discharge becomes an air arc and machining is not performed, and machining debris and generated gas are not removed. Electric discharge machining becomes unstable, and the thin wire electrode may break, making stable machining impossible.

The present invention has been proposed to improve this point.

[Means to solve the problem]

The wire cut electrical discharge machining apparatus of the present invention is an apparatus that performs electrical discharge machining while supplying a jet of machining fluid from a nozzle facing a machining gap between a wire electrode and a workpiece, and in which the machining fluid flow jetted from the nozzle is A light source that irradiates light, a sensor that detects transmitted light or reflected light, and a detection signal detected by the sensor for turbulence in the jetting machining fluid flow and a memorized detection signal for stable parallel flow are compared and determined. This system is provided with a control circuit that outputs a signal, and a flow rate control device that controls the flow rate of machining fluid to a stable parallel flow based on the signal output from the control circuit.

[Effect]

The machining fluid that is jetted from the nozzle into the machining gap is
When there is stable parallel flow, the amount of light received by the sensor is the maximum, and the more the liquid flow is disturbed, the more the amount of light received decreases. The sensor compares and discriminates detection signals output according to the amount of light received by the control circuit, and sends the results to the flow control device.The flow control device adjusts the processing fluid so that the amount of light received by the sensor approaches a stable parallel flow. Control flow rate and flow rate.

〔Example〕

The present invention will be explained below with reference to an embodiment of the drawings. In Fig. 1, 1 is a wire electrode, and the wire diameter is 0.1.
Copper, brass, or other alloy wire with a diameter of ~0.5 mm is used, and although not shown, it is normally wound and moved from one reel to the other, and the upper (lower) ) direction. 3
is a workpiece to be machined facing the wire electrode 1 between the guides 2, which is fixed to a processing table (not shown), and the processing table is equipped with an NC-controlled processing shape feeding device, and the workpiece 3 is connected to the wire electrode 1. Machining is performed by giving a relative feed of the machining shape between. 4 is a machining fluid supply nozzle provided on the workpiece toward the facing machining gap between the wire electrode 1 and the workpiece 3, and the machining fluid is usually tap water and is treated with an ion exchange resin to reduce the specific resistance. Distilled water of about 10 ² to ^{10 5} Ωcm is used, but of course water mixed with other substances or water mixed with oil can also be used. The machining fluid is supplied at a required flow rate by a pump (not shown), and is controlled by a flow rate control device 5 midway. Machining is performed by creating a pulse discharge between the wire electrode 1 and the workpiece 3 while supplying machining fluid.The pulse power source is one that generates direct current by turning on and off a switch element, or one that uses charging and discharging of a capacitor. A method of charging and discharging a capacitor using DC pulses may be used as desired, but this method is not shown. Reference numeral 6 denotes a laser oscillator that irradiates light for inspecting the jet state of the machining fluid jetted from the nozzle 4, 7 a reflector that irradiates the part of the liquid flow jetted from the nozzle 4, and 8 a reflector that emits light that passes through the liquid flow. A reflecting mirror 10 leading to the next sensor 9 is a control circuit that discriminates the detection signal of the optical sensor 9, and this output signal is applied to the flow rate control device 5 for automatic control. The sensor 9 described in FIGS. 2 and 3 can be used. This utilizes the principle of diffraction images such as Fraunhofer diffraction using laser light. The light emitted from the laser oscillator 6 is applied to the flowing water of the jet machining fluid, and the transmitted light is detected by the sensor 9. The sensor 9 has a plurality of photoelectric elements 9 ₁ , 9 ₂ , 9 ₃ arranged in a direction perpendicular to the running wire electrode 1 . ...9n are arranged at regular intervals with an interval d equal to the diffraction image.
That is, if the wire diameter of the wire electrode 1 is φ, the distance from the wire electrode 1 to the sensor 9 is x and the wavelength of the laser beam is λ, then the distance between the diffraction images can be obtained as d=λ/φ・x. , each photoelectric element 9 ₁ , 9 ₂ , 9
₃ ...9n are arranged with an interval d. A Fraunhofer diffraction image having an interval d as shown in FIG. 3 appears on the sensor 9 in which each photoelectric element is arranged. In this analytical image, the wave height value is parallel to the axis of the wire electrode 1, and interference fringes are distributed on horizontal coordinates symmetrically about the projected position of the wire electrode. This interference fringe spacing is d, which is equal to the spacing of the photoelectric elements 9. Therefore, the photoelectric elements 9 ₁ , 9 ₂ , 9 _{3 .} . . 9n are all arranged at positions where the interference fringes of the Fraunhofer diffraction image appear, so that they receive only the diffraction image and generate a signal.

The liquid flow jetted from the nozzle 4 is a parallel flow centered on the running wire electrode 1, and when a stable parallel flow is obtained, each photoelectric element 9 ₁ , 9 ₂ , 9
The amount of light received at ₃ ...9n is the maximum, but if turbulence occurs in the liquid flow, it will affect the interference fringes and reduce the amount of transmitted light. Therefore, the more the liquid flow is disturbed, the more the detection signal of the photoelectric element decreases, and by discriminating this with the discrimination circuit 10, the liquid flow state can be easily detected.

That is, the detection signal value of each photoelectric element 9 ₁ , 9 ₂ , 9 ₃ . A signal is generated by comparing and determining a signal with an input reference value. Each photoelectric element 9 ₁ ,
The detection signals of 9 ₂ , 9 ₃ . . . 9n may be determined individually, or the sum of the detection signals may be determined.

However, when the flow rate of the liquid jetted from the nozzle 4 decreases and air is drawn in from the surroundings to create a turbulent flow, the detection signal of the sensor 9 decreases, and this is stored in the discrimination control circuit 10. A control signal is applied to the flow rate control device 5 based on the comparison with a reference value for parallel flow to control the flow rate and flow velocity so as to provide stable parallel flow. When turbulent flow occurs, the change in the detection signal by the photoelectric element is approximately equal to that during normal machining when water is used as the machining fluid and an argon laser is used.
It was around 80-90%, and abnormalities could be easily detected.

In the above embodiment, the light detection of the jet liquid is detected and determined based on the signal of the sum of the upper and lower nozzles, and a control signal is output to control the upper and lower nozzles at the same time. The liquid detection and control can be configured to be performed independently.

Note that transmitted light, reflected light, scattered light, etc. can also be used at the same time to detect disturbances in the jet machining fluid by light irradiation. However, in the method using the Fraunhofer diffraction image described above, the detection angle can be increased because the diffraction image does not include scattered light or refracted light. Further, parallel light beams can be easily obtained by using a laser oscillator as the light source, but it goes without saying that light from another lamp may be used using a slit lens or the like.

〔Effect of the invention〕

When performing electric discharge machining while supplying a jet of machining fluid from a nozzle facing the machining gap between the wire electrode and the workpiece, if the machining fluid supplied jet from the nozzle to the machining gap is a stable parallel flow, the installed book The amount of light received by the sensor of the invention is maximum. and,
The more the liquid flow is disturbed, the more the amount of light received decreases. The sensor outputs a detection signal according to the amount of light received and sends it to the control circuit.The control circuit has the detection signal for stable parallel flow stored as a reference value, and the detection signal for stable parallel flow is stored as a reference value. When the amount of light received by the sensor decreases, the detection signal is compared with a reference value of a discrimination circuit and the result is sent to the flow rate control device. Upon receiving this signal, the flow rate control device can control the flow rate and flow velocity of the machining fluid so that the amount of light received by the sensor approaches a stable parallel flow.

In this way, by controlling the detection of the jet machining fluid, a parallel flow of a constant flow is caused to flow between the wire electrode 1 and the machining part of the workpiece 3, so that the machining fluid can be stably distributed even in a narrow gap, and the machining debris can be removed. It is possible to perform stable machining by improving the cooling effect, reducing the occurrence of arcs and short circuits, etc., and performing high-speed, high-efficiency electrical discharge machining without wire electrode breakage. .

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention, FIG. 2 is a partially enlarged detailed diagram, and FIG. 3 is an explanatory diagram thereof. DESCRIPTION OF SYMBOLS 1... Wire electrode, 3... Workpiece, 4... Nozzle, 5... Flow rate control device, 6... Light source, 9...
Sensor, 10...Discrimination control circuit.

Claims (1)

[Claims] 1. In an apparatus that performs electrical discharge machining while supplying a jet of machining fluid from a nozzle facing a machining gap between a wire electrode and a workpiece, a light source that irradiates light to the machining fluid flow jetting from the nozzle; A sensor that detects light or reflected light, and a control circuit that compares and discriminates between a detection signal for turbulence in a jetting machining liquid flow detected by the sensor and a stored detection signal for a stable parallel flow, and outputs a signal. and a flow rate control device for controlling the flow rate of machining fluid so that it becomes a stable parallel flow based on a signal output from the control circuit.