JP2519910B2 - Wire cut electrical discharge machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a wire-cut electric discharge machine that cuts a workpiece into a required shape by electric discharge machining with a wire electrode.

[Prior Art] A wire electrode used for wire-cut electric discharge machining has a thin wire diameter of about 0.03 to 0.3 mmφ and is apt to vibrate or bend during machining. Therefore, during high-speed, high-load machining where concentrated discharge is likely to occur, or during machining of a workpiece having a large plate thickness, the generated concentrated discharge causes wire breakage, which lowers machining performance and machining accuracy.

Therefore, in order to detect the occurrence of the concentrated discharge and its precursor phenomenon, the electrical characteristics of the discharge pulse generated based on the application of the voltage pulse for wire electrical discharge machining or the voltage pulse for inspection are detected and determined. Or to provide a detector for detecting discharge light near the entrance to detect the occurrence of discharge near the entrance to the workpiece of the wire electrode, which is said to cause more concentrated discharge during high-speed machining, The excessive discharge in the vicinity of the entrance is determined as the concentrated discharge by the detection discharge light.

[Problems to be Solved by the Invention] However, in detecting the electrical characteristics of the voltage, current, etc. of the discharge pulse based on the former machining gap applied voltage pulse, the arc shape caused by the machining gap state including various other factors is present. It is difficult to distinguish the abnormal discharge, etc. from the discharge pulse generated by the concentrated discharge part, and there is a problem that the detection control is inaccurate and excessive, and there is a problem in the vicinity of the entrance of the latter wire electrode to the workpiece. In the detection judgment by the discharge light detection, the concentrated discharge generated in other parts in the plate thickness of the work piece cannot be detected, and there is much noise in the discharge light detection, and the plate thickness of the work piece becomes large. There is a problem in that the occurrence of the concentrated discharge state leading to the wire electrode disconnection cannot be detected and discriminated accurately.

Therefore, the present invention has been proposed for the purpose of quickly and reliably detecting the concentrated discharge generated at any portion of the thickness of the work piece, without being affected by the size of the thickness of the work piece. .

[Means for Solving the Problems] The above-described object of the present invention is to move the wire electrode in the axial direction between the guides arranged at predetermined intervals while renewing the wire electrode while moving the wire electrode from a direction substantially perpendicular to the electrode axial direction. The workpiece is made to face each other through a minute gap, and the voltage pulse supplied from the machining power supply is applied between the workpiece and the wire electrode with the machining liquid interposed in the gap to generate pulse discharge. In wire-cut electric discharge machining, which provides a relative machining feed on the plane in the perpendicular direction between the wire electrode and the workpiece, the wire electrode passes through the workpiece-machined portion and is ejected. Radiation temperature detection device that measures the temperature of the processed wire electrode at the incoming part in a non-contact manner with an infrared sensor, and a reference value that sets the reference value of the temperature signal according to the selected wire cut electrical discharge machining conditions Setting And a detection device for comparing the detected temperature of the radiation temperature detection device with a reference value of the temperature signal set by the setting device and outputting a determination signal of the presence or absence of concentrated discharge in a machining gap of a predetermined level or more. This is achieved by adopting a configuration provided with and.

[Operation] According to the above configuration, the temperature of the processed wire electrode portion that passes through the processed portion of the work piece and comes out one after another is continuously and accurately measured by the infrared sensor with high sensitivity and responsiveness. By comparing the measured temperature with the reference value of the temperature signal based on the empirical rule corresponding to the currently selected wire-cut electrical discharge machining conditions, the wire electrode is exposed to a concentrated discharge state above a predetermined level while passing through the machining part. It is possible to accurately and quickly determine whether or not there is a concentrated discharge that has occurred regardless of where the concentrated discharge has occurred, and regardless of where the concentrated discharge has occurred, any concentrated discharge that has occurred in any part of the entire plate thickness of the work piece can be detected and distinguished. It is possible to accurately output the avoidance determination signal for preventing disconnection.

〔Example〕

The present invention will be described below with reference to one embodiment of the drawings.
In the figure, reference numeral 1 is a wire electrode, which is continuously fed out from a reel (not shown), travels along upper and lower guides 2, and is picked up as shown by an arrow. The wire electrode 1 is given a required tension and movement speed by a brake and a take-up device (not shown), and the electrode 1 moves linearly between the guides 2.
The workpiece 3 is opposed to and processed. Reference numeral 4 denotes a nozzle for supplying a processing liquid (ion exchange treated water), which is a workpiece 3
The wire electrode 1 is provided above and below and surrounds the guide 2.
It is provided coaxially with. Reference numeral 5 denotes a current-carrying electron that contacts and energizes the wire electrode 1 in the nozzle 4, and a machining pulse power source (not shown) is connected to perform pulse discharge between the electrode 1 and the workpiece 3 for machining.

FIG. 2 is a work piece 3 of the wire electrode 1 in FIG.
In the specific example of the radiation temperature detection device 6 for the wire electrode 1 provided in the portion that has passed through the processed portion facing the wire electrode 1
A reflecting mirror 7 is provided at the center, and the reflected light is focused by a lens 8 to Pb
The infrared sensor 10 such as S detects the temperature due to radiation. 9
Is a filter, 11 is a detection signal amplifier, and 12 is a discrimination device.
The temperature rise due to discharge concentration is determined by comparing with the reference value set by the setter 13 according to the currently set machining conditions and the empirical rule of data etc. when machining under the machining conditions.

When electric discharge machining is performed between the wire electrode 1 moving between the guides 2 and the workpiece 3 by pulse discharge, the wire electrode 1
The discharge point is heated by the discharge heat. When the discharge point moves and is distributed to each part of the wire electrode 1 to generate an electric discharge and stable machining is performed, the temperature rise of the wire electrode part moving and passing through the machining part facing the workpiece 3. Is not that high. However, the bending of the wire electrode 1,
When a concentrated discharge is generated at one place of the wire electrode 1 due to the influence of vibration, machining waste, etc., the temperature of the wire electrode 1 suddenly rises, and the temperature rise of that portion radiates infrared rays to the surroundings. Therefore, the infrared rays emitted from the wire electrode 1 that has moved through the processed portion are collected by the reflecting mirror 7,
It is focused by the lens 8 and detected by the infrared sensor 10 at its focus. The detection signal of the sensor 10 increases in proportion to the temperature rise of the wire electrode 1, and the sensor detection signal increases when concentrated discharge occurs. The detection signal is amplified by the intermediate amplifier 11 and input to the discriminating device 12.
A reference value corresponding to the machining condition currently set by the setter 13 is input to the discriminating device 12, and when the machining condition increases the machining energy, the reference value is increased, and when the machining energy is reduced, the reference value is increased. Enter a setting to reduce the value. The determination device 12 compares the reference value with the detection signal from the sensor 10 to make a determination. For example, if the comparison differential voltage is small, it is determined that the temperature rise of the wire electrode 1 is low and the discharge is normal, and if the difference voltage is large, the temperature rise of the electrode is high and concentrated discharge is generated. Of course, you can also make stepwise judgments in multiple stages,
The state of transition from stable discharge to abnormal discharge can be easily determined.

For example, with a Bs electrode with a wire diameter of 0.2 to 0.3 mmφ, SKD material is 100 mm
When processing at a processing speed of ² / min, wire electrode 5m / min
The temperature of the most recent wire electrode part that has moved and passed through the processing part is detected by the PbS infrared sensor,
By determining the detection signal by the discriminating device 12 and controlling the supply of the machining voltage pulse when the state in which the concentrated arc discharge occurs is determined, stable machining can be performed without disconnecting the wire electrode. .

In this way, by measuring the temperature of the wire electrode in a non-contact manner by the infrared sensor, it is possible to perform temperature measurement without disturbing the running state of the wire electrode and perform accurate machining, and the infrared sensor has high sensitivity. Since the responsiveness is good, the temperature of the wire electrode emerging from the processed part of the workpiece can be continuously and accurately measured one after another even when the wire electrode moves at high speed. By comparing with the reference value, it is possible to accurately and promptly determine the occurrence state of the concentrated discharge regardless of the location where the concentrated discharge occurs. Further, as the infrared sensor, a well-known high-sensitivity infrared sensor such as an InSb sensor is used in addition to the PbS sensor.

The control of the wire-cut processing device based on the determination of the concentrated discharge by measuring the temperature of the wire electrode as described above is not limited to the interruption control of the power supply, but also the extension width of the machining pulse, the reduction control of the discharge current peak value, and the wire electrode It is possible to perform control of moving traveling speed, tension, control of jet pressure of the working fluid supplied from the nozzle, and other combined control.

〔The invention's effect〕

As described above, the present invention provides a radiation temperature detection device that measures the temperature of the electrode in a non-contact manner with an infrared sensor in a portion that passes through a processed portion of the wire electrode that faces the workpiece,
Since a device for determining the degree of concentration of electric discharge is provided by comparing the detection signal of the device with a reference value set by the processing conditions, an increase in the temperature of the wire electrode is mainly caused by infrared rays emitted from the electrode. It is possible to perform non-contact and easy measurement by measuring through a medium, and because it does not disturb the running state of the wire electrode for temperature measurement, it is possible to perform accurate processing, and the infrared sensor High sensitivity and good responsiveness enable accurate and reliable temperature detection even with wire electrodes moving at high speed. Therefore, the reference value that is set by inputting this detection signal according to the processing conditions,
That is, when the processing conditions are rough processing conditions of high energy, the reference value is also increased, and when the processing conditions are finishing processing conditions of low energy, the reference value is set to be lower, and the detection signal is compared with this reference value. Since the concentrated discharge is determined by this method, no matter where the concentrated discharge occurs in the plate thickness of the work piece, the size of the plate thickness is not significantly affected, and stable discharge machining enables wire electrode It is possible to accurately determine the case where the temperature suddenly rises to a high temperature due to the occurrence of the concentrated arc discharge in distinction from the case where the temperature rises. When a concentrated discharge is generated by this determination, the machining pulse control, the wire electrode movement control, the jet machining liquid control, and the like are quickly performed to prevent wire electrode disconnection and enable stable machining.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a partially enlarged detailed view thereof. 1 ... Wire electrode 2 ... Guide 3 ... Workpiece 4 ... Nozzle 5 ... Conductor 6 ... Radiation temperature detector 7 ... Reflector 8 ... Lens 10 ... Infrared sensor 12 ... Discrimination device 13 …… Reference value setting device

Claims (1)

(57) [Claims] 1. A wire electrode is axially renewed and fed between guides arranged at a predetermined interval, and a workpiece is opposed to each other through a minute gap from a direction substantially perpendicular to the electrode axial direction. , A voltage pulse supplied from a machining power source is applied between the workpiece and the wire electrode in a state where the machining liquid is interposed in the gap to generate pulse discharge, and between the wire electrode and the workpiece. In a wire-cut electric discharge machine that provides relative machining feed on the plane in the right angle direction, a machined wire electrode provided at a portion where the wire electrode comes out after passing through a processed part of a workpiece. A radiation temperature detection device that measures the temperature in a non-contact manner with an infrared sensor, a reference value setting device that sets a reference value of a temperature signal that corresponds to the selectively set wire cut electrical discharge machining condition, and detection of the radiation temperature detection device temperature And a reference value of the temperature signal set by the setting device, and a discriminating device for outputting a discriminating signal for the presence or absence of concentrated discharge in a machining gap having a predetermined level or more is provided. Cut electric discharge machine.