JPH0313012B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a wire cut electric discharge machining apparatus.

A wire-cut electric discharge machining device using a wire electrode winds the wire electrode while pulling it from one reel to the other reel, and the workpiece is opposed from a direction approximately perpendicular to the axis of the wire electrode, which moves in the axial direction. During electrical discharge machining, a gap is formed, and during this time
In addition to supplying machining fluid such as water or oil to By relatively applying machining feed such as a predetermined contour shape to the body on the plane in the perpendicular direction, various shapes can be cut and punched. The wire electrode used usually has a wire diameter of 0.05 to 0.5 mm.
Although a thin wire of about φ is used, it has the disadvantage that it is easy to cut because the diameter of the wire electrode is relatively small. This drawback can be improved to some extent by devising a method for supplying a jet of machining liquid to the machining area. This is mainly achieved by appropriately cooling the wire electrode and workpiece in the electrical discharge machining area, that is, between machining, and by removing machining debris generated during machining, by supplying machining fluid in a more contrived manner. Electric discharge machining can be performed without abnormal discharge such as arc discharge by removing machining debris from the machining gap and interposing a machining fluid whose concentration of machining products is reduced to a predetermined value or less. This is so that it can be done. That is, simply spouting machining fluid from an external nozzle to the machining area cannot remove machining debris beyond a predetermined level, and the machining fluid is not supplied to the inside of the machining space. Cooling in a predetermined state could not be achieved, and as a result, abnormal discharge and wire electrode breakage often occurred.

For example, despite the wide variety of workpiece thicknesses and machining shapes, the injection supply of machining fluid
For example, even if the injection pressure, injection flow rate, flow rate, etc. are changed, the injection from the nozzle is only supplied from a fixed direction near the surface of the workpiece. axial direction)
There were various problems such as incomplete supply of machining fluid to the center of the workpiece.

It is also possible to supply sufficient machining fluid to the center of the thickness of the workpiece by increasing the machining fluid supply pressure and speeding up the flow rate, but it is difficult to supply sufficient machining fluid in this way. In this case, the supply pressure must be made considerably high, and there is a problem in that the machining fluid scatters violently.

In view of the above-mentioned problems, the present invention was invented with the aim of making it possible to sufficiently supply machining fluid to the machining part under a relatively low pressure supply state, and the machining fluid is connected to a wire electrode. It has a machining fluid supply nozzle that sprays coaxially, an opening diameter that is the same as or smaller than the width of the machining groove, and an opening that is placed a minute distance away from the wire electrode. an auxiliary machining liquid supply nozzle that injects auxiliary machining liquid, a rotation mechanism that rotates the auxiliary machining liquid supply nozzle around a wire electrode, and a control device that controls the operation of the rotation mechanism, and a control device that controls the operation of the rotation mechanism. The rotation mechanism is controlled so that the opening of the nozzle is always located on the back side of the wire electrode with respect to the machining progress direction, and the auxiliary machining liquid is supplied at a faster flow rate than the machining liquid injected from the machining liquid supply nozzle. The feature is that machining is performed while jetting machining liquid from a nozzle.

Hereinafter, the present invention will be explained with reference to illustrated embodiments.

The embodiment of the present invention shown in FIG. 1 is a perspective view seen from above showing a state in which a workpiece 1 is subjected to electrical discharge machining by a wire electrode 2, and the lower surface example of the workpiece 1 is also similar. It has the configuration mode shown in FIG.
The mounting and moving table etc. are omitted. Wire cut electrical discharge machining using the wire electrode 2 is performed using a starting hole 1a formed at a predetermined position of the workpiece 1.
The machining process starts from , forms a bent machining groove 3 as shown in the figure, and is in a state where machining progresses in the direction of the arrow 3a at the current position. As shown by the dotted line, the machining fluid 4 is sprayed around the wire electrode 2 from a normal wire electrode coaxial machining fluid supply nozzle 7 in the form of a jet flow that surrounds the wire electrode 2 coaxially. ing. The diameter of the machining fluid injection opening of this nozzle 7 is set to be larger than the width of the machining groove 3. And a close aide of the wire electrode 2,
Wire electrode 2 in the direction of machining progress (during machining)
The opening of the auxiliary machining liquid supply nozzle 5 is arranged close to the back side of the wire electrode 2, close to the right side of the wire electrode 2 in the figure. This auxiliary machining fluid supply nozzle 5 is located at a minute distance from the wire electrode 2, that is, approximately 1 mm, and has a width equal to the machining groove width of the machining groove 3 of the workpiece, which is formed by electric discharge machining using the wire electrode 2. or a width smaller than the width of the opening, and supplies the machining fluid approximately parallel to the wire electrode. The auxiliary machining liquid supply nozzle 5 is rotated about the wire electrode 2 by a rotation mechanism which will be described later. Therefore, among the machining fluids that are injected coaxially with the wire electrode 2, the machining fluid that is supplied from this auxiliary nozzle 5 is as follows:
It is sprayed directly into the machining groove 3 immediately behind the wire electrode 2 approximately along the axis of the wire electrode 2, and the wire electrode 2
and during processing = distribution of processing fluid in the G section,
That is, mainly the stagnation of the injected processing liquid by the nozzle 7,
By appropriately controlling the outflow, the machining fluid can be efficiently and accurately supplied to the machining part, and as a result, the machining fluid can moderately cool the part G between machining and reduce the Since the concentration of processed products such as processed waste is maintained at an appropriate level and air is prevented from entering the processed portion, cutting of the wire electrode 2 is prevented.

Further, the operation of the present invention will be explained with reference to FIG. FIG. 2 shows the state of the wire electrode 2 during processing. As shown in the figure, the cross-sectional contour line 1b of the machining surface or inter-machining surface of the workpiece 1 is given a machining feed by control so as to increase machining performance such as machining speed. As described above, the wire electrode 2 has an arcuate convex shape in the machining feed direction 3a, and the wire electrode 2 corresponding thereto is also renewed in the axial direction in a curved state due to pressure during machining such as discharge pressure. In other words, the position of the wire electrode 2 is not the same near the surface and inside the workpiece 1, but is slightly shifted. Therefore, the jet axis of the machining fluid injected from the normal machining fluid supply nozzles 7, 7' does not coincide with the axis of the machining part wire electrode 2 or the contour line 1b, and therefore the wire electrode 2 and the During the machining interval G between the contour line 1b, not only is the machining fluid not necessarily injected smoothly into the interior, but also cavitation effects occur, and machining waste is not removed sufficiently and the machining fluid is not refreshed, and the machining fluid is not sufficiently removed. The reality is that medium discharge often occurs. However, according to the present invention, auxiliary machining fluid supply nozzles 5 and 5' are provided to supply machining fluid along the wire electrode 2 near the back side of the machining gap G of the wire electrode 2. By injecting and supplying the machining fluid at a faster flow rate than the machining fluid that is injected and supplied by the nozzles 7 and 7', the easy outflow of the machining fluid injected by the machining fluid supply nozzles 7 and 7' to the machining groove 3 side can be controlled or By adjusting the machining interval, the inflow into the G and the rotation renewal are promoted, the occurrence of cavitation is suppressed, and processing products such as processing waste are appropriately removed, and the machining interval is processed in a favorable environment. Therefore, disconnection of the wire electrode 2 can be suppressed as much as possible.

Further, the auxiliary machining liquid supply nozzles 5, 5' are configured to rotate around the wire electrode 2 in accordance with the machining progress direction of the wire electrode 2 in which machining progresses along the desired machining contour shape. The machining fluid spouting ports of the auxiliary machining fluid supply nozzles 5, 5' are always located on the machined groove 3 side, in other words, above (or inside) the machining groove 3 on the back side of the wire electrode 2 with respect to the machining progress direction. It's becoming like that. Next, an example of a rotation mechanism for rotating the auxiliary machining liquid supply nozzles 5, 5' will be explained based on FIG. 3.

Fig. 3 shows an example of a mechanism for rotating the auxiliary machining liquid supply nozzles 5, 5'. Only the items shown are shown and the others are omitted. The auxiliary machining liquid supply nozzle 5 is attached to a rotation adjustment mechanism 60 via an attachment arm 51. The rotation adjustment mechanism 60 includes a cylindrical support member 61 fixedly supported by a fixed part such as an arm of the processing machine main body through which the wire electrode 2 is inserted through its axis, and a ring-shaped support member 61 at the tip of the cylindrical support member 61. Two thrust bearings 63a and 63b fixed to the protrusion 62 with a distance between them.
A gear-shaped rotating member 64 whose rotation axis is the wire electrode 2 held and provided between these thrust bearings 63a and 63b, and a gear 65 that meshes with tooth grooves on the outer periphery of this rotating member 64. , a motor 6 disposed on a fixed part that drives and controls the rotation of this gear 65.
It consists of 6. Further, a guide holder 2B that holds the die guide 2A and the machining fluid supply nozzle 7 are connected and fixed to the lower part of the cylindrical support member 61. A hole 67 is formed in the center of the rotating member 64 to be inserted into the cylindrical support member 61, and the rotating member 64 is attached to the cylindrical support member 61 so as to be rotatable about the wire electrode 2. The rotation of the rotating member 64 causes the rotating member 64 to rotate. Further, the rotating member 64 has the auxiliary machining liquid supply nozzle 5 held on the mounting arm 51 connected to the wire electrode 2.
A movement mechanism 71 is attached that causes vertical and reciprocating or vibrational movement along the axis. 72 is a drive device for the movement mechanism 71, and a control device 8 including a numerical control device.
Operation command changeover switches 73, 74 which turn on/off the movement, select various movements, switch combinations, and switch the frequency, amplitude, stroke, radius of rotation, or speed of each movement based on command signals from the
is provided.

Although not shown, a fixing table such as an xy cross table for processing to which the workpiece 1 is fixed is moved in response to a signal related to the contour shape to be processed. This signal is sent to the xy drive device of the cross table (not shown) from the numerical value 8, which processes the information of the control device including the numerical control device, such as a readout signal from paper or magnetic tape or a manual input signal, and is fixed. The workpiece 1 is machined into a desired shape by moving the table. Furthermore, the control device 8 is connected to a switch mechanism 9 that includes a drive device for the motor 66, and the switch mechanism 9 includes:
The motor 66 is turned on and off by the rotation angle of a member 64 such as a rotary encoder provided on the motor 66, or by a detection period signal 76 from a position detection device 75, which is output by the control device 8, and the motor 66 is activated and stopped. The position of the auxiliary machining fluid supply nozzle 5 is determined by the equal rotation angle depending on the machining contour shape at that point in time between the wire electrode 2 and the workpiece 1, especially the contact direction of the contour shape. 2. It is designed to be controlled so that it is located on the back side. The relative operation between the fixed base and the wire electrode 2 for moving the workpiece 1 and the operation of the motor 66, that is, the rotation of the rotating member 64, are controlled by a control device based on signal information set in a program in advance. The workpiece 1 is controlled by the output signal of 8, and the workpiece 1 is
The rotating member 64 is rotated in accordance with the movement of. By rotating the rotating member 64, the auxiliary machining fluid supply nozzle 5 is always positioned on the machining groove 3 or at a predetermined position within the groove, on the back side of the wire electrode 2 with respect to the machining progress direction. ing. Specifically, in order to process the workpiece 1 into a predetermined contour shape on the xy plane by cutting or cutting, the workpiece 1 is moved according to the shape by operating the fixing table. The operation of this fixed base is performed based on information that is programmed in advance into the control device 8, including numerical control, and the rotation angle control information of the rotation member 64 is also input in advance in this information. By placing it there, the fixed base and the rotating member 64, that is, the auxiliary machining liquid supply nozzle 5 can be interlocked.

FIG. 4 is a characteristic curve diagram of one embodiment for explaining the effects of the present invention, in which the horizontal axis represents the machining fluid ejection flow rate (m/s) of the auxiliary machining fluid supply nozzle 5, and the vertical axis represents the average machining current. This is a diagram with the scale shown in (A), and the processing conditions are as follows.

Wire electrode: 6:4 brass electrode with approximately 0.2mmφ, wire electrode feed speed: approximately 2.5m/min, wire electrode tension: approximately 1Kg, workpiece: SKD11 with plate pressure approximately 20mm,
Voltage pulse: No-load voltage approximately 130V, voltage pulse width: approximately 7μs, pause width between voltage pulses: approximately 10μs, current amplitude: approximately 15A, capacitor capacity: 1.5μF, diameter of machining fluid supply nozzle 7, 7': approximately 0.6 mmφ, machining fluid jet flow rate: approximately 0.6 m/s, auxiliary machining fluid supply nozzle 5,
5' diameter: approx. 0.23mmφ.

In FIG. 4, curve 20 shows the experimental results of the conventional method using only machining fluid supply nozzles 7 and 7'. At a flow rate of , the average machining current cannot be increased that much. curve 2
1 shows experimental results according to the present invention,
The auxiliary machining liquid supply nozzles 5 and 5' are attached with the ejection flow velocity from the nozzle 7 being constant at about 0.6 m/s, and their positions are on the back side of the wire electrode 2 with respect to the machining progress direction. When the rotational position is controlled, the average machining current can be increased while the machining fluid jet flow velocity from the nozzles 5 and 5' is relatively free from wire electrode 2 breakage. , 7', the increase in machining current is saturated at approximately twice the jet flow velocity of nozzle 7. From this experimental result, according to the method of the present invention, the average machining current can be increased to approximately 1.6 without increasing the jet pressure from nozzle 7. It turns out that it can be increased by a factor of two. In the case of this experimental example, the jet flow velocity of each of the machining fluid supply nozzles 7 and 7' was set to be the same.
It is preferable to adjust the jet flow speed of the corresponding auxiliary nozzles 5, 5' according to the jet flow speed of the respective nozzles 7, 7', and when the jet flow speed of the nozzles 7, 7' is higher, the jet flow speed of the auxiliary nozzles 5, 5 is adjusted. It seems possible to increase the ejection flow velocity of ' by more than twice or several times, and the ejection flow velocity of the lower nozzle 7' of the workpiece 1 is usually set higher than that of the nozzle 7 on the upper side of the workpiece 1. The ejection flow speeds of the nozzles 5 and 5' may be set in the opposite relationship,
In this case, it is possible to increase the machining current to a greater extent and improve machining performance.

In this way, the reason why the wire electrode does not break even when the average machining current is increased is that the cooling effect on the wire electrode in the machining section is improved and the time between machining is
This is because machining debris can be removed reasonably well from the auxiliary nozzle 5, but the machining fluid spouted from the auxiliary nozzle 5 is applied to the wire electrode approximately 1 mm from the back side of the wire electrode in the direction of machining progress. Since the machining liquid is jetted along the auxiliary nozzle 5, the machining liquid jetted from the auxiliary nozzle 5 is only slightly supplied during machining, if at all.
As much as the above effect can be achieved, it does not contribute to an increase in the amount of machining fluid supplied to the machining chamber, and the above effect according to the present invention can be explained as follows. That is, the ejected liquid flow from the auxiliary nozzle 5 which is jetted in parallel to the wire electrode near the back side of the wire electrode acts to partition the machined groove, and by forming a partition wall, the machining time is reduced. A columnar flow path is formed around the wire electrode, and the machining fluid jetted from the nozzle 7 flows through this flow path in a convergent state without jetting in the direction of the machined groove. This is thought to be due to the fact that the machining fluid ejected from the wafer is efficiently supplied to the machining section, and the amount of machining fluid supplied to the machining section substantially increases. From the experimental results shown in Fig. 4, the above-mentioned partitioning effect clearly appears when the machining fluid is jetted from the auxiliary nozzle 5 at a flow rate higher than that of the machining fluid jetted from the nozzle 7. It increases as the flow rate of the liquid flow increases, and by increasing the flow rate, the machining liquid ejected from the nozzle 7 is prevented from flowing out in the direction of the machining groove, so that the machining liquid is efficiently supplied to the machining part. It is understood that when the flow velocity from the auxiliary nozzle 5 becomes approximately twice the flow velocity from the nozzle 7, the increase in this partitioning effect reaches its limit.

Therefore, according to the present invention, a sufficient amount of machining fluid can be substantially supplied to the machining section without increasing the ejection pressure from the nozzle 7 for supplying machining fluid to the machining section, thereby achieving a cooling effect on the wire electrode. In addition to being able to effectively remove machining debris from the machining gap, it is possible to prevent overheating of the wire electrode, wire breakage due to abnormal discharge, and deterioration of machining accuracy due to abnormal discharge. In addition, sufficient supply of machining fluid to the machining section is achieved by jetting the machining fluid from both the nozzle 7 and the auxiliary nozzle 5 parallel to the wire electrode in a low-pressure supply state. It is less likely that irregular and unnecessary vibrations will be generated in the wire electrode, and from this point of view as well, it is effective in preventing deterioration of processing accuracy. In addition, since a low-pressure supply of machining fluid is sufficient, it is possible to prevent the machining fluid from scattering. In No. 5, the opening diameter is the same as or smaller than the width of the machining groove, so the jetted machining liquid is injected into the machining groove and does not collide with the surface of the workpiece and be violently scattered.

In addition, it seems that the linearity of the machining part of the wire electrode 2 is improved by the addition of the auxiliary machining fluid supply nozzles 5 and 5', especially when the machining fluid jet flow velocity is set high, such as around several m/s. , the machining accuracy of the corners of the machining contour shape is significantly improved.

The embodiment of the present invention described above with reference to the drawings has been described with reference to the case where the auxiliary machining liquid supply nozzles 5, 5' are attached to both the upper side and the lower side of the workpiece 1, but the present invention is applicable to the above-mentioned embodiment. Auxiliary processing liquid nozzle,
As explained above, the objects and effects of the present invention can be achieved even when the machining fluid supply nozzle 7 or 7', which supplies and spouts machining fluid, is provided on either the upper side or the lower side. It is clear from the above that the present invention also includes such embodiments.

As detailed above, according to the present invention, machining fluid can be sufficiently supplied to the machining part under relatively low pressure, so that it is possible to prevent the machining fluid from scattering around the wire electrode. Cutting accidents can be prevented, machining performance and machining speed can be improved, and machining accuracy can also be improved.

[Brief explanation of drawings]

Fig. 1 is a partially enlarged perspective view of a wire-cut electric discharge machining apparatus showing an embodiment of the present invention, Fig. 2 is a cross-sectional view showing the machining state, and Fig. 3 is an example of the rotation mechanism of the auxiliary machining fluid supply nozzle of the present invention. FIG. 4 is a diagram showing processing characteristics by the conventional method and the method of the present invention. DESCRIPTION OF SYMBOLS 1...Workpiece, 2...Wire electrode, 3...Machining groove, 4...Conventional machining fluid, 5...Auxiliary machining fluid supply nozzle.

Claims (1)

[Claims] 1. A wire electrode that is given a renewed feed in the axial direction and a workpiece are placed facing each other with a small gap between them, and voltage pulses are applied with machining fluid interposed between the two to generate intermittent electrical discharge. In the wire cut electrical discharge machining method, which cuts out a desired contour shape by applying a relative machining feed between the two in a plane direction substantially orthogonal to the axis of the wire electrode, the machining fluid is mixed with the wire electrode. It has a machining fluid supply nozzle that sprays coaxially, an opening diameter that is the same as or smaller than the width of the machining groove, and the opening is placed a minute distance away from the wire electrode, and the machining fluid is machined approximately parallel to the wire electrode. An auxiliary machining liquid supply nozzle that sprays a liquid, a rotation mechanism that rotates the auxiliary machining liquid supply nozzle around a wire electrode, and a control device that controls the operation of the rotation mechanism are provided. The rotation mechanism is controlled so that the opening of the supply nozzle is always located on the back side of the wire electrode with respect to the machining progress direction, and the auxiliary machining liquid is supplied at a flow rate higher than that of the machining liquid injected from the machining liquid supply nozzle. A wire cut electric discharge machining method characterized in that machining is performed while jetting machining fluid from a supply nozzle.