Wire electrical discharge machine and auto wire feeding method of wire electrical discharge machine

A wire electrical discharge machine includes: a guide pipe as a guide member arranged on a path for feeding a wire electrode from a feed roller toward a workpiece and having a passage hole through which the wire electrode is passed; an airflow generator for generating a flow of compressed air in the passage hole and switching a flow direction of compressed air flowing through the passage hole between a forward direction and a reverse direction; a deflection detector for detecting a deflection of the wire electrode; and a control device for controlling the airflow generator so as to generate a flow of compressed air in the forward direction in the passage hole during auto wire feeding and, when the deflection detector detects the deflection, change the flow direction of compressed air to the reverse direction and thereafter switch the flow direction of compressed air to the forward direction.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2017-252888 filed on Dec. 28, 2017, the contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a wire electrical discharge machine having an auto wire feeding function for automatically feeding a wire electrode and an auto wire feeding method of the wire electrical discharge machine.

Description of the Related Art

Generally, a wire electrical discharge machine has an auto wire feeding function of automatically inserting a wire electrode into a machining start hole formed in an object to be machined (workpiece) or a machining groove formed by wire electrical discharge machining to perform wire feeding.

However, there are cases where the tip of the wire electrode cannot be inserted into the machining start hole or the machining groove in the workpiece but touches the workpiece, and then the wire electrode is deflected or bent, resulting in failure in auto wire feeding. For this reason, Japanese Laid-Open Patent Publication No. 2017-035744 discloses a configuration in which when a deflection of the wire electrode is detected, a retry process of auto wire feeding is executed by turning the wire electrode feed rollers in reverse to rewind the wire electrode and then turning the rollers forward to feed the wire electrode.

SUMMARY OF THE INVENTION

However, since the motor for turning the roller requires a drive time for actuating the roller from the starting torque to the rated torque, the retry process tends to take time. As a result, there is a concern that the time required for auto wire feeding becomes long disadvantageously.

The present invention has been devised to solve the above problem, it is therefore an object of the present invention to provide a wire electrical discharge machine and an auto wire feeding method of a wire electrical discharge machine, which can shorten the time required for auto wire feeding.

A first aspect of the present invention resides in a wire electrical discharge machine, which includes: a feed roller configured to feed a wire electrode toward a workpiece; a collecting roller configured to collect the wire electrode having passed through the workpiece; a guide member arranged on a path for feeding the wire electrode from the feed roller toward the workpiece and having therein a passage hole through which the wire electrode is passed; an airflow generator configured to generate a flow of compressed air in the passage hole and to switch a flow direction of the compressed air flowing through the passage hole between a forward direction which corresponds to a feeding direction of the wire electrode and a reverse direction opposite to the feeding direction of the wire electrode; a deflection detector configured to detect a deflection of the wire electrode; and a control device configured to control the airflow generator so as to generate a flow of the compressed air in the forward direction in the passage hole during auto wire feeding and so as to, when the deflection detector detects the deflection, change the flow direction of the compressed air flowing through the passage hole to the reverse direction and thereafter switch the flow direction of the compressed air from the reverse direction to the forward direction.

A second aspect of the present invention resides in an auto wire feeding method of a wire electrical discharge machine for automatically feeding a wire electrode. The wire electrical discharge machine includes: a feed roller configured to feed a wire electrode toward a workpiece; a collecting roller configured to collect the wire electrode having passed through the workpiece; a guide member arranged on a path for feeding the wire electrode from the feed roller toward the workpiece and having therein a passage hole through which the wire electrode is passed; and an airflow generator configured to generate a flow of compressed air in the passage hole and to switch a flow direction of the compressed air flowing through the passage hole between a forward direction which corresponds to a feeding direction of the wire electrode and a reverse direction opposite to the feeding direction of the wire electrode. The auto wire feeding method includes: a first step of controlling the airflow generator so as to generate the flow of the compressed air in the forward direction in the passage hole; a second step of detecting a deflection of the wire electrode; and a third step of controlling the airflow generator so as to, when the deflection of the wire electrode is detected, change the flow direction of the compressed air flowing through the passage hole to the reverse direction and thereafter switch the flow direction of the compressed air from the reverse direction to the forward direction.

In the present invention, the compressed air slightly moves the tip of the wire electrode in a random manner, so that it is possible to retry insertion of the wire electrode into the machining start hole or the machining groove of the workpiece. Therefore, compared to the case where the motor is controlled to alternately repeat the rewinding and feeding of the wire electrode, it is possible to achieve retry of wire feeding without requiring time to drive the motor from the starting torque to the rated torque. Thus, according to the present invention, it is possible to shorten the time required for auto wire feeding.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Now, the wire electrical discharge machine and the auto wire feeding method of the wire electrical discharge machine according to the present invention will be detailed by describing preferred embodiments with reference to the accompanying drawings.

Embodiment

[Configuration of Wire Electrical Discharge Machine]

FIG. 1is a diagram showing a configuration of essential components of a wire electrical discharge machine10according to the embodiment. The wire electrical discharge machine10is a machine tool for machining a workpiece W with electric discharge generated between the workpiece W and a wire electrode12.

The workpiece W is supported on an unillustrated table. The workpiece W may also be referred to as a work. The material of the workpiece W is, for example, a metal material such as an iron-based material or a superhard material (e.g., tungsten carbide). The wire electrode12is formed of, for example, tungsten-based, copper alloy-based, brass-based metal or the like.

The wire electrical discharge machine10includes a supply system unit14for supplying the wire electrode12to the workpiece W and a collection system unit16for collecting the wire electrode12exhausted by machining on the workpiece W.

The supply system unit14is a unit for feeding the wire electrode12toward the workpiece W and is arranged above the workpiece W. The supply system unit14includes at least an unillustrated wire bobbin, feed rollers20, a guide pipe22, and a supply side wire guide24, arranged in order from the upstream side in the feed direction of the wire electrode12.

The feed rollers20deliver or feed the wire electrode12supplied from an unillustrated wire bobbin, which is the supply source of the wire electrode12, to the workpiece W. The feed rollers20are rotated by the torque given by a supply side motor26.

The guide pipe22is a guide member for guiding the wire electrode12sent out from the feed rollers20toward the workpiece W. The guide pipe22is laid out in a path for feeding the wire electrode12from the feed rollers20toward the workpiece W. In the guide pipe22, an passage hole22afor allowing the wire electrode12to pass through is formed in the feed direction (axial direction of the guide pipe22).

The supply side wire guide24guides the wire electrode12that passes through the passage hole22aof the guide pipe22toward the downstream side. The supply side wire guide24has a supply side die guide24a. The supply side die guide24apositions the wire electrode12to be fed to the workpiece W above and near the workpiece W.

The collection system unit16is a unit for collecting the wire electrode12fed downward through the workpiece W, and is arranged below the workpiece W. The collection system unit16includes, at least, a collection side wire guide30, collecting rollers32and an unillustrated bucket for collecting the spent wire electrode12, arranged in order from the upstream side in the feed direction of the wire electrode12.

The collection side wire guide30guides the wire electrode12that has passed through the machining start hole wa or the machining groove wb of the workpiece W, toward the collecting rollers32. The collection side wire guide30has a collection side die guide30a. The collection side die guide30apositions the wire electrode12that has passed through the workpiece W, below and near the workpiece W. The wire electrode12is supported by the supply side die guide24aand the collection side die guide30a.

The collecting rollers32are arranged under the collection side wire guide30to collect the spent wire electrode12. The collecting rollers32are rotated by the torque given by a collection side motor34. The wire electrode12taken up by the collecting rollers32is collected by the unillustrated bucket.

The feed rollers20, the guide pipe22, the supply side wire guide24, the collection side wire guide30, and the collecting rollers32are arranged on a straight line in the vertical direction (the direction in which the force of gravity acts). Therefore, the wire electrode12, which is fed from the feed rollers20and collected by the collecting rollers32, is sent along the vertical direction. When the wire electrode12is collected by the collecting rollers32, a predetermined tension is applied to the wire electrode12.

The wire electrical discharge machine10further includes a wire cutter40, an airflow generator42, a deflection detector44, a tension detector46, and a control device48.

The wire cutter40is provided, for example, between the guide pipe22and the supply side wire guide24to cut the wire electrode12. The wire cutter40may be controlled by the control device48. InFIG. 1, a blade type cutting tool is illustrated as the wire cutter40for cutting the wire electrode12, but other cutting means may be used for the wire cutter40. For example, electric current may be applied locally to a portion of the wire electrode12to be cut, to thereby heat and anneal the portion, and thereafter apply torque to the wire electrode12, whereby the wire electrode is cut at the annealed portion.

The airflow generator42is a device for generating a flow of compressed air in the passage hole22aof the guide pipe22, and includes an air compressor50, a supply pipe52and a three-way valve54. The air compressor50generates compressed air and injects the generated compressed air into the supply pipe52.

The supply pipe52guides the compressed air ejected from the air compressor50to the passage hole22aof the guide pipe22. The supply pipe52includes a main pipe52athat communicates the air compressor50with the three-way valve54, a first branch pipe52bthat communicates the three-way valve54with an upper air port23aof the guide pipe22, and a second branch pipe52cthat communicates the three-way valve54with a lower air port23bof the pipe22.

The upper air port23ais formed in the passage hole22aat a position near an inlet for the wire electrode12(i.e., on an inlet side for the wire electrode12) and is located at a different position from the inlet for the wire electrode12, and communicates with the passage hole22a. The lower air port23bis formed in the passage hole22aat a position near an outlet for the wire electrode12(i.e., on an outlet side for the wire electrode12) and is located at a position different from the outlet for the wire electrode12, and communicates with the passage hole22a.

The three-way valve54communicates the main pipe52awith the first branch pipe52bor the second branch pipe52c, and is controlled by the control device48. When the three-way valve54communicates the main pipe52awith the first branch pipe52b, the compressed air generated by the air compressor50is injected into the passage hole22afrom the upper air port23aof the guide pipe22. An upper part of the passage hole22aabove the upper air port23ais narrower than a part of the passage hole22abetween the upper air port23aand the lower air port23bso that the air-flow resistance in the passage hole22abecomes higher on the upper side than on the lower side of the upper air port23a. Therefore, the compressed air flows forward through the passage hole22ain the same direction as the feed direction of the wire electrode12.

On the other hand, when the three-way valve54communicates the main pipe52awith the second branch pipe52c, the compressed air generated by the air compressor50is injected into the passage hole22afrom the lower air port23bof the guide pipe22. A lower part of the passage hole22abelow the lower air port23bis narrower than the part of the passage hole22abetween the upper air port23aand the lower air port23bso that the air-flow resistance in the passage hole22abecomes higher on the lower side than on the upper side of the lower air port23b. Therefore, the compressed air flows in reverse through the passage hole22ain the direction opposite to the feed direction of the wire electrode12.

In this way, the airflow generator42can switch the direction of the compressed air flowing through the passage hole22aof the guide pipe22between the forward direction and the reverse direction.

The deflection detector44detects deflection of the wire electrode12. Although the deflection detector44is installed between the feed rollers20and the guide pipe22inFIG. 1, the deflection detector44may be installed at another position. The detection result detected by the deflection detector44is output to the control device48.

The tension detector46detects the tension of the connected wire electrode12. Although the tension detector46is installed upstream of the feed rollers20inFIG. 1, the tension detector46may be installed at another position. The detection result detected by the tension detector46is output to the control device48.

The control device48includes a processor such as a CPU and a memory in which a program is stored, and the processor runs a program stored in the memory to thereby provide the function as the control device48of the present embodiment. The control device48is a computer that appropriately controls diverse parts (the supply side motor26, the collection side motor34and the airflow generator42) of the wire electrical discharge machine10.

The control device48starts the auto wire feeding process at the start of machining or after cutting of the wire electrode12by the wire cutter40. That is, the control device48controls the airflow generator42to thereby generate a forward flow of compressed air in the passage hole22aof the guide pipe22. Specifically, the control device48controls the three-way valve54to establish communication between the main pipe52aand the first branch pipe52b, and thereafter actuates the air compressor50to thereby create forward flow of compressed air in the passage hole22aof the guide pipe22.

In this state, as the control device48controls the supply side motor26to rotate the feed rollers20, the wire electrode12is sent out from the wire bobbin to the workpiece W.

In this way, the control device48feeds the wire electrode12to the workpiece W while generating compressed air flowing in the forward direction through the passage hole22aof the guide pipe22. As a result, the control device48can move the wire electrode12forward while preventing slack of the wire electrode12by compressed air. Therefore, the wire electrode12can be easily inserted into the machining start hole wa or the machining groove wb of the workpiece W.

In order to collect the wire electrode12passing through the machining start hole wa or the machining groove wb of the workpiece W, the control device48controls the collection side motor34to start rotating the collecting rollers32before the wire electrode12fed by the feed rollers20reaches the collecting rollers32.

Further, when starting auto wire feeding, the control device48monitors the deflection and tension of the wire electrode12during auto wire feeding, based on the outputs from the deflection detector44and the tension detector46. The term “during auto wire feeding” means a period from the time at which the feed rollers20starts feeding the wire electrode12downward in order to start auto wire feeding of the wire electrode12until the time at which the wire electrode12is fed by a predetermined length. The predetermined length is a distance from the feed rollers20to the collecting rollers32at least. If the wire electrode12is fed downward by at least the distance from the feed rollers20to the collecting rollers32, the wire electrode12is collected by the collecting rollers32so that a predetermined tension is applied to the wire electrode12. Therefore, the control device48can determine that the auto wire feeding is successful, based on the output from the tension detector46.

Specifically, when the deflection detector44has detected no deflection of the wire electrode12while the tension detector46detects a tension equal to or higher than a threshold until the predetermined length of the wire electrode12is fed, the control device48determines that the auto wire feeding is successful. In this case, the control device48stops the airflow generator42, the supply side motor26and the collection side motor34to complete the auto wire feeding process.

On the other hand, when the deflection detector44detects a deflection of the wire electrode12before the predetermined length of the wire electrode12is fed, the tip of the wire electrode12abuts against the workpiece W or any other object because the wire electrode12cannot be inserted through the machining start hole wa or the machining groove wb of the workpiece W or for any other reason. In this case, the control device48starts a retry process.

That is, the control device48controls the supply side motor26and the collection side motor34to stop the feed rollers20and the collecting rollers32. In this state, the control device48controls the airflow generator42to alternately switch the direction of the compressed air flowing through the passage hole22aof the guide pipe22between the reverse direction and the forward direction.

Specifically, the control device48controls the three-way valve54so as to switch connection of the main pipe52aof the supply pipe52in turns to the second branch pipe52cand to the first branch pipe52b, thereby switch the direction of compressed air flowing through the passage hole22aof the pipe22between the reverse direction and the forward direction. Note that this switching operation is performed, for example, about several times per second.

As a result, the control device48can slightly move the tip of the wire electrode12in a random manner. Therefore, the wire electrode12can be easily inserted into the machining start hole wa or the machining groove wb of the workpiece W even if the tip of the wire electrode12collides with or touches the workpiece W or any other object because the wire electrode12cannot be inserted through the machining start hole wa or the machining groove wb of the workpiece W or for any other reason.

When the deflection that has been detected by the deflection detector44becomes undetected, the control device48controls the airflow generator42to maintain the direction of compressed air flowing through the passage hole22aof the guide pipe22in the forward direction, and terminates the retry process. Thereafter, the control device48controls the supply side motor26to rotate the feed rollers20again and resume the feeding of the wire electrode12, thereby resuming auto wire feeding.

On the other hand, when the deflection of the wire electrode12does not become undetected by the deflection detector44even after the number of times that the flowing direction of the compressed air has been alternately switched between the reverse direction and the forward direction exceeds a predetermined number of times, the control device48determines that auto wire feeding has failed. In this case, the control device48stops the airflow generator42and terminates the retry process and the auto wire feeding process. When the auto wire feeding fails, the wire electrode12is cut by the wire cutter40, and the auto wire feeding process is restarted as necessary.

Next, the auto wire feeding method of the wire electrical discharge machine10will be described.FIG. 2is a flow chart showing a flow of an auto wire feeding process executed by the control device48of the wire electrical discharge machine10.

At step S1, the control device48controls the airflow generator42so as to generate a forward flow of compressed air in the passage hole22aof the guide pipe22, then the control goes to step S2. At step S2, the control device48controls the supply side motor26to turn the feed rollers20, thereby starting feeding of the wire electrode12. The control device48also controls the collection side motor34to turn the collecting rollers32, and the control proceeds to step S3.

At step S3, the control device48determines whether or not a deflection of the wire electrode12has been detected by the deflection detector44. When no deflection of the wire electrode12is detected, the control proceeds to step S4.

At step S4, the control device48determines whether or not the auto wire feeding has succeeded. Here, when the wire electrode12is collected by the collecting rollers32without slack or deflection of the wire electrode12and the tension detector46detects a tension that is equal to or greater than the threshold value, the control device48determines that the auto wire feeding has been successfully done. On the other hand, if the wire electrode12has not yet been collected by the collecting rollers32and tension equal to or greater than the threshold value is not detected, the control device48determines that the auto wire feeding has not yet been successful, and the control returns to step S3so as to monitor the deflection of the wire electrode12based on the output from the deflection detector44.

When deflection of the wire electrode12is detected at step S3, the control proceeds to step S5, in which the control device48executes a retry process. The operation of this retry process will be described later. When the deflection of the wire electrode12becomes undetected by executing the retry process, the control proceeds to step S4. When the deflection of the wire electrode12does not become undetected even after the retry process has been executed, the control goes to step S6.

At step S6, the control device48stops the airflow generator42, and the control proceeds to step S7. At step S7, the control device48controls the supply side motor26to stop the feed rollers20, whereby feeding of the wire electrode12is stopped. Thus, the auto wire feeding process is completed.

Next, the retry process will be described.FIG. 3is a flowchart showing the flow of the retry process at step S5shown inFIG. 2.

At step S11, the control device48, by controlling the supply side motor26and the collection side motor34, stops the feed rollers20and the collecting rollers32so that feeding of the wire electrode12is stopped. Then, the control proceeds to step S12.

The control device48controls the airflow generator42so as to cause compressed air to flow in the passage hole22aof the guide pipe22in the reverse direction at step S12, and then controls the airflow generator42so as to cause compressed air to flow in the passage hole22aof the guide pipe22in the forward direction at step S13. Thereafter, the control device48proceeds to step S14.

At step S14, the control device48determines whether or not deflection of the wire electrode12has become undetected by the deflection detector44. If it is undetected, the control device48proceeds to step S15. At step S15, the control device48controls the supply side motor26and the collection side motor34to turn the feed rollers20and the collecting rollers32again so as to resume the feeding of the wire electrode12. Thus, the control device48terminates the retry process and goes to step S4(seeFIG. 2).

On the other hand, if the deflection of the wire electrode12has not become undetected at step S14, the control device48proceeds to step S16and determines whether or not the number of times the retry operation has been performed exceeds a predetermined number of times. The retry operation is an operation for switching the flow direction of compressed air in the passage hole22abetween the reverse direction and the forward direction successively at steps S12and S13, and one set of the steps S12and S13corresponds to one retry operation.

If the number of times of retry operation does not exceed the predetermined number of times, the control device48returns to step S12and sequentially executes step S12and step S13to alternately switch the flow direction of the compressed air between the reverse direction and the forward direction. When the number of times of retry operation exceeds the predetermined number of times, the control device48determines that the auto wire feeding has failed. In this case, the control device48ends the retry process and proceeds to step S6(seeFIG. 2).

As described above, in the present embodiment, when deflection of the wire electrode12is detected during auto wire feeding, the feeding of the wire electrode12is stopped while the airflow generator42is controlled so as to change the direction of the compressed air flowing through the passage hole22ain the guide pipe22to the reverse direction and then switch to the forward direction.

As a result, in this embodiment, the tip of the wire electrode12can be slightly moved in a random manner by compressed air. Therefore, in the present embodiment, when the wire electrode12touches or abuts against the workpiece W or any other object and thereby undergoes a deflection due to deviation of the wire electrode12from the machining start hole wa or the machining groove wb, it is possible to retry to insert the wire electrode12into the machining start hole wa or the machining groove wb by compressed air.

Accordingly, in the present embodiment, it is possible to achieve retry of auto wire feeding without requiring time to drive the motor from the starting torque to the rated torque, which would be needed in the case where the supply side motor26is controlled to repeat rewinding and feeding of the wire electrode12alternately. As a result, according to the present embodiment, it is possible to shorten the time required for auto wire feeding.

When the supply side motor26is controlled to alternately repeat the rewinding and feeding of the wire electrode12, the wire electrode12tends to move up and down regularly at the same position. In contrast to this, in the present embodiment, as described above, the tip of the wire electrode12is slightly moved irregularly at different positions by the viscosity of the compressed air. Therefore, according to the present embodiment, as compared to the case where the supply side motor26is controlled to alternately repeat the rewinding and feeding of the wire electrode12, the wire electrode12can be inserted more easily through the machining start hole wa or the machining groove wb.

In addition, as compared to the case where the supply side motor26is controlled to alternately repeat the rewinding and feeding of the wire electrode12, the moving length of the tip of the wire electrode12when it slightly moves tends to be smaller. Therefore, according to the present embodiment, by slightly moving the tip of the wire electrode12finely and irregularly in a short time in a minutely vibrating manner, it is possible to shorten the time required for auto wire feeding while enabling easy insertion of the wire electrode12into the machining start hole wa or the machining groove wb.

Though the present invention has been described by referring to the embodiment as an example, the technical scope of the present invention should not be limited to the range of the above embodiment. It goes without saying that various modifications and improvements can be added to the above embodiment. Further, it is also apparent from the scope of claims that those added with such modifications and improvements should be incorporated in the technical scope of the invention.

FIG. 4is a partly enlarged diagram showing a wire electrical discharge machine of Modification 1, modified from that shown inFIG. 1. Herein, the same components as those described above are allotted with the same reference numerals and repeated explanation will be omitted as appropriate.

The airflow generator42in the wire electrical discharge machine10of Modification 1 further includes a turbulence generating member56. The turbulence generating member56disturbs the flow of compressed air and is detachably arranged in the lower air port23bof the guide pipe22.

FIG. 5is a diagram showing a configuration example (1) of the turbulence generating member56. The turbulence generating member56shown inFIG. 5has a substantially oval shaped main body56aand flow passages56bformed in the main body56a. The flow passage56bis a recessed portion on the minor axis side of the main body56a. Screw thread grooves56care formed on the major axis side of the main body56a. The screw thread grooves56ccorrespond to screw thread ridges formed on the wall of the guide pipe22around the lower air port23b.

Therefore, the turbulence generating member56shown inFIG. 5can be screwed to the wall of the guide pipe22around the lower air port23b. In this arrangement, gaps are formed between the wall of the guide pipe22around the lower air port23band the flow passages56bof the turbulence generating member56provided in the lower air port23b, and compressed air passes through the gaps. The flow passages56bcan be shifted by turning the main body56aon the screw thread grooves56c.

Instead of the turbulence generating member56shown inFIG. 5, it is also possible to provide a turbulence generating member56shown inFIG. 6or a turbulence generating member56shown inFIG. 7. The turbulence generating members56shown inFIGS. 6 and 7have a cylindrical main body56dand flow passages56eformed in the main body56d.

The main body56dis fitted into the lower air port23bin a slidable manner on the wall of the guide pipe22around the lower air port23b. Therefore, the flow passages56ecan be shifted by sliding the main body56d. The flow passage56epenetrates from one end face of the main body56dto the other end face. The flow passage in the example shown inFIG. 6has a circular cross-section, whereas the flow passage in the example shown inFIG. 7has a fan shaped cross-section, but other shapes may be used. Although the number of the flow passages56eis three in the examples shown inFIGS. 6 and 7, more than three flow passages or a single flow passage is possible.

In the wire electrical discharge machine10of Modification 1, the turbulence generating member56is provided in the lower air port23bof the guide pipe22, so that it is possible to disperse the compressed air injected from the air compressor50into the lower air port23bvia the second branch pipe52cto thereby produce turbulent flow of air. As a result, it is possible to slightly move the tip of the wire electrode12more irregularly by the compressed air flowing through the passage hole22aof the guide pipe22through the flow passages56bof the turbulence generating member56.

It should be noted that the turbulence generating member56may have a configuration other than the configurations shown inFIGS. 5 to 7, for example, a protrusion or the like which protrudes from the wall of the guide pipe22around the lower air port23btoward the interior of the lower air port23b.

In addition, although the turbulence generating member56is provided in the lower air port23bof the guide pipe22, it may be provided in the second branch pipe52c. In other words, the turbulence generating member56may be provided on the flow path through which compressed air flows between a position at which the compressed air is injected and a position near the outlet for the wire electrode12in the passage hole22a. More specifically, this flow path corresponds to a flow path from the air compressor50to the lower air port23b. In order to slightly move or vibrate the tip of the wire electrode12in a more random manner, the turbulence generating member56is preferably arranged in the lower air port23b.

FIG. 8is a diagram showing a configuration of essential components of a wire electrical discharge machine10of Modification 2. Herein, the same components as those described above are allotted with the same reference numerals and repeated explanation will be omitted as appropriate.

The wire electrical discharge machine10of Modification 2 has an airflow generator42A that is different from the airflow generator42of the above embodiment. The airflow generator42A further includes an ejector60. The ejector60communicates with the three-way valve54via the second branch pipe52cand communicates with the first branch pipe52bvia a communication pipe60a.

In this airflow generator42A, when the three-way valve54connects the main pipe52awith the first branch pipe52b, the compressed air generated by the air compressor50is injected from the upper air port23aof the guide pipe22into the passage hole22a. Therefore, the compressed air flows through the passage hole22ain the forward direction or the same direction as the feed direction of the wire electrode12.

On the other hand, when the three-way valve54connects the main pipe52awith the second branch pipe52c, the compressed air generated by the air compressor50is discharged to the outside via the ejector60. Along with this discharge, the air (compressed air) of the guide pipe22flows in the reverse direction through the passage hole22aand is drawn from the upper air port23avia the communication pipe60aby the ejector60.

In this way, the airflow generator42A of Modification 2 draws in the air inside the passage hole22afrom the inlet side for the wire electrode12in the passage hole22aso that the compressed air flows through the passage hole22ain the reverse direction.

Therefore, similarly to the airflow generator42of the above-described embodiment in which compressed air is injected from the outlet side for the wire electrode12in the passage hole22a, the airflow generator42A of Modification 2 is able to switch the flow direction of compressed air flowing through the passage hole22abetween the forward direction and the reverse direction.

In the above embodiments, the feed rollers20, the guide pipe22, the supply side wire guide24, the collection side wire guide30and the collecting rollers32are arranged vertically (i.e., in the direction of gravitational force) on a straight line in this order from the upstream side of the wire feeding direction. However, the feed rollers20, the guide pipe22, the supply side wire guide24, the collection side wire guide30, and the collecting rollers32may be arranged on a straight line in order from the upstream side of the wire feeding direction in a direction intersecting the vertical direction or the direction of gravitational force.

In the above embodiment, determining the success or failure of auto wire feeding is based on whether or not the tension detector46detects a tension that is equal to or greater than the threshold when the wire electrode12is collected by the collecting rollers32without slack or deflection of the wire electrode12. However, other methods may be used as a method for determining the success or failure of auto wire feeding.

For example, a detector plate may be arranged on the downstream side of the collecting rollers32in the wire feeding direction, so as to determine that the auto wire feeding is successful when contact of the wire electrode12is detected by the detector plate and determine that the auto wire feeding has failed when no contact is detected by the detector plate. It should be noted that this determination method and the determination method of the above embodiments may be used together.

The above Modifications 1 to 4 may be arbitrarily combined as long as no contradiction arises.

Technical ideas that can be grasped from the above embodiment and modifications are described below.

The wire electrical discharge machine (10) includes: a feed roller (20) configured to feed a wire electrode (12) toward a workpiece (W); a collecting roller (32) configured to collect the wire electrode (12) having passed through the workpiece (W); a guide member (22) arranged on a path for feeding the wire electrode (12) from the feed roller (20) toward the workpiece (W) and having therein a passage hole (22a) through which the wire electrode (12) is passed; an airflow generator (42,42A) configured to generate a flow of compressed air in the passage hole (22a) and to switch the flow direction of the compressed air flowing through the passage hole (22a) between the forward direction which corresponds to the feeding direction of the wire electrode (12) and the reverse direction opposite to the feeding direction of the wire electrode (12); a deflection detector (44) configured to detect a deflection of the wire electrode (12); and a control device (48) configured to control the airflow generator (42,42A) so as to generate a flow of the compressed air in the forward direction in the passage hole (22a) during auto wire feeding and so as to, when the deflection detector (44) detects the deflection, change the flow direction of the compressed air flowing through the passage hole (22a) to the reverse direction and thereafter switch the flow direction of the compressed air from the reverse direction to the forward direction.

Thus, the compressed air slightly moves the tip of the wire electrode (12) in a random manner, so that it is possible to retry insertion of the wire electrode (12) into the machining start hole (wa) or the machining groove (wb) of the workpiece (W). Therefore, compared to the case where the motor is controlled to alternately repeat the rewinding and feeding of the wire electrode (12), it is possible to achieve retry of wire feeding without requiring time to drive the motor from the starting torque to the rated torque. As a result, the time taken for auto wire feeding can be reduced.

The control device (48) may be configured such that when the deflection detector (44) detects the deflection, the control device (48) switches the flow direction of the compressed air flowing through the passage hole (22a) alternately between the reverse direction and the forward direction until the deflection becomes undetected by the deflection detector (44). As a result, even if the switching is repeated many times, it is possible to reduce the time taken for auto wire feeding, as compared to the case where the motor is controlled to alternately repeat the rewinding and feeding of the wire electrode (12).

The airflow generator (42,42A) may be configured to inject the compressed air into the passage hole (22a) from a position near the outlet for the wire electrode (12) (i.e., an outlet side for the wire electrode) in the passage hole (22a) so that the compressed air flows through the passage hole (22a) in the reverse direction.

The airflow generator (42) may include a turbulence generating member (56) configured to disturb the flow of the compressed air, the turbulence generating member being arranged on a flow path of the compressed air between the outlet side for the wire electrode (12) in the passage hole (22a) and a position at which the compressed air is injected. This makes it possible to slightly move the tip of the wire electrode (12) in a more random manner.

The turbulence generating member (56) may be provided at an air port (23b) formed at a different position from the outlet for the wire electrode (12) on the outlet side for the wire electrode (12) in the passage hole (22a). This also makes it possible to slightly move the tip of the wire electrode (12) in a more random manner.

The airflow generator (42A) may be configured to draw in air inside the passage hole (22a) from a position near the inlet for the wire electrode (12) (i.e., an inlet side for the wire electrode) in the passage hole (22a) so as to flow the compressed air in the passage hole (22a) in the reverse direction.

The auto wire feeding method is a method for a wire electrical discharge machine (10) for automatically feeding a wire electrode (12). The wire electrical discharge machine (10) includes: a feed roller (20) configured to feed a wire electrode (12) toward a workpiece (W); a collecting roller (32) configured to collect the wire electrode (12) having passed through the workpiece (W); a guide member (22) arranged on a path for feeding the wire electrode (12) from the feed roller (20) toward the workpiece (W) and having therein a passage hole (22a) through which the wire electrode (12) is passed; and an airflow generator (42,42A) configured to generate a flow of compressed air in the passage hole (22a) and to switch the flow direction of the compressed air flowing through the passage hole (22a) between the forward direction which corresponds to the feeding direction of the wire electrode (12) and the reverse direction opposite to the feeding direction of the wire electrode (12). The auto wire feeding method includes: a first step (S1) of controlling the airflow generator (42,42A) so as to generate the flow of the compressed air in the forward direction in the passage hole (22a); a second step (S3) of detecting a deflection of the wire electrode (12); and a third step (S5) of controlling the airflow generator (42,42A) so as to, when the deflection of the wire electrode (12) is detected, change the flow direction of the compressed air flowing through the passage hole (22a) to the reverse direction and thereafter switch the flow direction of the compressed air from the reverse direction to the forward direction.

Thus, the compressed air slightly moves the tip of the wire electrode (12) in a random manner, so that it is possible to retry insertion of the wire electrode (12) into the machining start hole (wa) or the machining groove (wb) of the workpiece (W). Therefore, compared to the case where the motor is controlled to alternately repeat the rewinding and feeding of the wire electrode (12), it is possible to achieve retry of wire feeding without requiring time to drive the motor from the starting torque to the rated torque. As a result, the time taken for auto wire feeding can be reduced.

The third step (S5) may be effected such that when the deflection of the wire electrode (12) is detected, the flow direction of the compressed air flowing through the passage hole (22a) is switched alternately between the reverse direction and the forward direction until the deflection of the wire electrode (12) becomes undetected. As a result, even if the switching is repeated many times, it is possible to reduce the time taken for auto wire feeding, as compared to the case where the motor is controlled to alternately repeat the rewinding and feeding of the wire electrode (12).

The airflow generator (42,42A) may be configured to inject the compressed air into the passage hole (22a) from an outlet side for the wire electrode (12) in the passage hole (22a) so that the compressed air flows through the passage hole (22a) in the reverse direction.

The airflow generator (42) may include a turbulence generating member (56) configured to disturb the flow of the compressed air, the turbulence generating member being arranged on a flow path of the compressed air between the outlet side for the wire electrode (12) in the passage hole (22a) and a position at which the compressed air is injected. This makes it possible to slightly move the tip of the wire electrode (12) in a more random manner.

The turbulence generating member (56) may be provided at an air port (23b) formed at a different position from the outlet for the wire electrode (12) on the outlet side for the wire electrode (12) in the passage hole (22a). This also makes it possible to slightly move the tip of the wire electrode (12) in a more random manner.

The airflow generator (42A) may be configured to draw in air inside the passage hole (22a) from the inlet side for the wire electrode (12) in the passage hole (22a) so as to flow the compressed air in the passage hole (22a) in the reverse direction.