JP2013248694A - System and method for multiwire electric discharge machining - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent disconnection of a wire electrode itself due to an increase in heat generation amount generated from the entire wire electrode supplied with electric power, and to protect a component that is brought into contact with the wire electrode.SOLUTION: A multiwire electric discharge machining system slicing a workpiece at intervals between wire electrodes arranged in parallel comprises: a plurality of guide rollers causing the wire electrodes arranged in parallel to travel in the same direction; an electric power supplying piece supplying machining electric power supply to the wire electrodes arranged in parallel; and a first cooling unit cooling a first part in which the wire electrodes arranged in parallel are brought into contact with the plurality of guide rollers. The first cooling unit cools the first part when the machining electric power supply supplies electric power to the wire electrodes arranged in parallel via the electric power supplying piece.

Description

  The present invention relates to a multi-wire electric discharge machining system and a multi-wire electric discharge machining method.

  A wire saw is known as an apparatus for slicing a silicon ingot into a large number of thin pieces. Recently, there is a multi-wire electric discharge machining apparatus for machining a member into a thin plate by using an electric discharge machining technique using a multi-wire.

  Among the techniques relating to the wire saw, for example, in prior art document 1, in order to improve the cooling effect of the member to be cut in the wire saw, a technique for cooling the wire by discharging a coolant from the outer peripheral portion of the roller to the wire through the nozzle. Is disclosed.

Japanese Patent Laid-Open No. 11-221748

In multi-wire electrical discharge machining, it is possible to perform electrical discharge machining with high uniformity by appropriately supplying power to all wires at appropriate positions.However, as the number of wires to be supplied increases, the wire electrode itself has electrical resistance and resistance. Therefore, in multi-wire electric discharge machining, as the number of wire electrodes to be fed increases, various problems due to an increase in the amount of heat generated from the entire wire electrode occur.
Patent Document 1 does not disclose anything about solving the problem caused by the increase in the amount of heat generated from the entire wire electrode to be fed.

  An object of the present invention is to provide a mechanism capable of preventing disconnection of the wire electrode itself due to an increase in the amount of heat generated from the entire wire electrode to be fed, and protecting a component in contact with the wire electrode.

  The present invention is a multi-wire electric discharge machining system for slicing a workpiece at an interval between parallel wire electrodes, and a plurality of guide rollers that run the parallel wire electrodes in the same direction, A first cooling unit that cools a first portion where the wire electrode and the plurality of guide rollers are in contact with each other. The unit cools the first part when the machining power is supplied to the wire electrodes arranged in parallel via the power supply.

The first cooling unit is further arranged in parallel by rotating the plurality of guide rollers when the machining power is supplied to the arranged wire electrodes via the power supply. The first portion is cooled regardless of whether the wire electrode is traveling in the same direction.
The apparatus further includes a second cooling unit that cools a second portion where the wire electrodes arranged side by side and the power supply are in contact with each other.

  The first cooling unit and the second cooling unit inject cooling water onto the surfaces of the wire electrodes arranged in parallel to cool the first part and the second part. To do.

  Moreover, the 1st setting part which sets the injection pressure of the cooling water injected toward the said 1st site | part, and the 2nd setting part which sets the injection pressure of the cooling water injected toward the said 2nd site | part. And the first setting unit and the second setting unit are set so that the injection pressure injected into the second part is lower than the injection pressure injected into the first part. It is characterized by that.

  In addition, a ratio of the ion-exchanged water controlled to a specific resistance within a predetermined range as a processing liquid to a position where the parallel wire electrode and the workpiece are close to each other and a ratio of the injected cooling water And an ion exchange resin that manages the specific resistance of the cooling water so that the resistance is substantially equal to the specific resistance of the ion exchange water.

  According to the present invention, it is possible to provide a mechanism that can prevent disconnection of the wire electrode itself due to an increase in the amount of heat generated from the entire wire electrode to be fed, and can protect components that come into contact with the wire electrode.

A multi-wire electric discharge machining system according to the present invention. A multi-wire electric discharge machining apparatus according to the present invention. Electricity supply in the present invention. The electric circuit diagram in a prior art. Multi-wire electric discharge machine in the prior art. The discharge pulse in this invention. The electric circuit diagram in this invention. A multi-wire electric discharge machining system according to the present invention. The figure which shows an example of arrangement | positioning of the electric power supply in this invention. The figure which shows an example of arrangement | positioning of the electric power supply in this invention. The figure which shows an example of arrangement | positioning of the electric power supply in this invention. The figure which shows an example of arrangement | positioning of the electric power supply in this invention. The figure which shows how the electric current flows by arrangement | positioning of the electric power supply in this invention. The figure which shows the 1st cooling unit in this invention. The figure which shows the 2nd cooling unit in this invention.

  Referring to FIG.

  FIG. 1 is an external view of a multi-wire electric discharge machine 1 according to an embodiment of the present invention as viewed from the front. The configuration of each mechanism shown in FIG. 1 is an example, and it goes without saying that there are various configuration examples depending on the purpose and application.

FIG. 1 is a diagram showing a configuration of a multi-wire electric discharge machining system according to the present invention. The multi-wire electric discharge machining system includes a multi-wire electric discharge machining device 1, a power supply device 2, and a machining fluid supply device 50.
The multi-wire electric discharge machining system can slice a workpiece into thin pieces at intervals of a plurality of wires (wire electrodes) arranged in parallel by electric discharge.

  Reference numeral 1 denotes a multi-wire electric discharge machining apparatus. In FIG. 1, a workpiece feeding device 3 driven by a servo motor is provided on the upper portion of the wire 103 and can move the workpiece 105 in the vertical direction. In the present invention, the workpiece 105 is fed downward and electric discharge machining is performed between the workpiece 105 and the wire 103. However, the workpiece feeding device 3 may be provided below the wire 103 to move the workpiece 105 upward.

  Reference numeral 2 denotes a power supply device. In FIG. 2, a discharge servo control circuit that controls the servo motor controls the discharge gap to be a constant gap in order to efficiently generate discharge according to the state of discharge. Positioning is performed and electric discharge machining proceeds.

  The machining power supply circuit (FIG. 7) supplies a discharge pulse for electric discharge machining to the wire 103, performs control adapted to a state such as a short circuit generated in the discharge gap, and discharges a discharge gap signal to the discharge servo control circuit. Supply.

  Reference numeral 50 denotes a machining liquid supply device. Reference numeral 50 denotes a machining liquid necessary for cooling the electric discharge machining portion and removing machining chips (debris) to the workpiece 105 and the wire 103 by a pump, and machining chips in the machining liquid. , Management of specific resistance or conductivity (1 μS to 250 μS) by ion exchange resin, and management of liquid temperature (around 20 ° C.). Water is mainly used as the machining fluid, but electric discharge machining oil can also be used.

  Reference numerals 8 and 9 denote main rollers. Grooves are formed on the main rollers at a predetermined pitch and number so as to be processed at a desired thickness, and two wires whose tension is controlled from the wire supply bobbin are provided. The necessary number of rolls are wound around one main roller and sent to a take-up bobbin. A wire speed of about 100 m / min to 900 m / min is used.

  As the two main rollers rotate in the same direction and at the same speed, one wire 103 sent from the wire feeding portion circulates around the outer periphery of the main rollers (two) and is arranged in parallel. A plurality of wires 103 can run in the same direction.

As shown in FIG. 8, the wire 103 is a single connected wire. The wire 103 is fed from a bobbin (not shown) and fitted into a guide groove (not shown) on the outer peripheral surface of the main roller. After being wound spirally (approximately 2000 times at the maximum), it is wound around a bobbin (not shown).
The multi-wire electric discharge machine 1 is connected to the power supply unit 2 via the electric wire 513 and is operated by electric power supplied from the power supply unit 2.

  As shown in FIG. 1, the multi-wire electric discharge machine 1 includes a block 15 that functions as a base of the multi-wire electric discharge machine 1, a block 20 that is installed in an upper portion of the block 15, and a work feeding device 3. A bonding portion 4, a silicon ingot 105, a processing tank 6, a main roller 8, a wire electrode 103, a main roller 9, a power supply unit 10, and a power supply 104.

  The processing tank 6 supplies ion-exchanged water managed with a specific resistance (electric conductivity) within a predetermined range as a processing liquid to a position (discharge point) where the wire electrode arranged in parallel and the workpiece are close to each other. .

  Reference numeral 201 denotes an upper portion (first part) of the guide roller in order to protect the guide roller 8 whose material in contact with the wire electrode is made of heat-sensitive resin from heat generated by the wire electrode when power is supplied. A pipe (first cooling unit) in which cooling water for injecting cooling water from the nozzles is dispersed throughout the guide roller 8.

  Reference numeral 202 denotes an upper portion (first portion) of the guide roller in order to protect the guide roller 9 whose material in contact with the wire electrode is made of heat-sensitive resin from heat generated when the power is supplied. A pipe (first cooling unit) in which cooling water for injecting cooling water from the nozzles is dispersed throughout the guide roller 9.

  The specific resistance of the cooling water is controlled by the ion exchange resin in the same manner as the processing liquid so that the specific resistance of the injected cooling water becomes substantially equal to the specific resistance of the ion exchange water (processing liquid). This is because even if the cooling water and the machining fluid are mixed, the discharge is not affected.

203, the material of the portion in contact with the wire electrode is made of a cemented carbide that is resistant to heat. The power supply 104 has higher heat resistance than the guide roller 9 against heat generation from the wire electrode when power is supplied. However, in addition to heat generation due to the electric resistance value of the wire electrode itself when power is supplied, the contact resistance between the wire electrode and the supply electron (frictional heat) when the wire electrode is in contact with the supply electron 104 in a running state. ) Also occurs, and the calorific value at this site further increases.
This is a pipe (second cooling unit) in which cooling water for injecting cooling water from the nozzle to the surface (second portion) of the power supply 104 is dispersed throughout the power supply 104.

Cooling water is jetted onto the surface of the power supply 104 at a lower (weaker) jet pressure than the upper part of the guide roller. This is because there is no mechanism for restraining the wire electrode on the guide roller on the surface of the power supply 104, so that the contact state between the wire electrode and the power supply is not disturbed by the injection of cooling water.
Thus, in order to set the injection pressure of the cooling water injected toward the surface (second portion) of the power supply 104, there is a second setting unit (not shown).

  The first setting unit and the first setting unit are configured so that the injection pressure injected onto the surface (second portion) of the power supply 104 is lower (weaker) than the injection pressure injected onto the upper portion (first portion) of the guide roller. The pressure of 2 setting parts is set, respectively.

  The cooling water sprayed 204 on the upper part of the guide roller 8 does not scatter to the outer periphery but flows to the lower part of the guide roller 8, so that the surface of the guide roller (wire In order to efficiently cool the entire contact surface with the electrode), the outer peripheral plate is installed so as to cover the outer periphery of the guide roller 8.

205 is configured such that the cooling water sprayed on the upper part of the guide roller 9 does not scatter to the outer periphery but flows to the lower part of the guide roller 9, so that the surface of the guide roller (wire In order to efficiently cool the entire contact surface with the electrode), the outer peripheral plate is installed so as to cover the outer periphery of the guide roller 9.
FIG. 2 will be described.
FIG. 2 is an enlarged view within a dotted line 16 frame shown in FIG.

Reference numerals 8 and 9 denote main rollers (guide rollers). A wire 103 is wound around the main roller a plurality of times, and the wires 103 are aligned at a predetermined pitch in accordance with grooves formed on the main roller.
The main roller has a structure in which metal is used in the center and the outside is covered with resin.
In order to supply a discharge pulse from a machining power source between the main guide rollers, a power supply 104 is provided to contact 10 of the wires 103 (FIG. 3).
The arrangement of the power supply 104 is provided centering on a position where the lengths of the wires are equal from both ends of the silicon ingot 105.
The power supply 104 is resistant to mechanical wear and is required to be conductive, and a cemented carbide is used.
A silicon ingot 105 is arranged at the upper part of the central portion between the main rollers, is attached to the work feeding device 3 and is moved in the vertical direction for processing.
A processing tank 6 is provided in the central portion between the main rollers, and the wire 103 and the silicon ingot 105 are immersed to cool the electric discharge processing portion and remove the processing chip.

  As shown in FIG. 3, the number of wires 103 that are in contact with ten wires 103 is shown as one, but the number of wires and the total number of electrons supplied are increased according to the required number. Needless to say.

The block 20 is joined to the work feeding device 3. The work feeding device 3 is bonded (bonded) to the silicon ingot 105 (work) and the bonding portion 4.
In this embodiment, a silicon ingot 105 will be described as an example of a processing material (workpiece).

  The bonding part 4 may be anything as long as it is for bonding (joining) the work feeding device 3 and the silicon ingot 105 (work). For example, a conductive adhesive is used.

  The work feeding device 3 is a device having a mechanism for moving the silicon ingot 105 bonded (bonded) by the bonding portion 4 in the vertical direction. When the work feeding device 3 moves in the downward direction, the silicon ingot 105 is moved. Can be brought closer to the wire 103.

  The processing tank 6 is a container for storing a processing liquid. The working fluid is, for example, deionized water having a high resistance value. By providing the machining liquid between the wire 103 and the silicon ingot 105, a discharge occurs between the wire 103 and the silicon ingot 105, and the silicon ingot 105 can be shaved.

The main rollers 8 and 9 are formed with a plurality of rows of grooves for attaching the wires 103, and the wires 103 are attached to the grooves. Then, the main roller 8, 9 rotates to the right or left, so that the wire 103 travels.
As shown in FIG. 2, the wire 103 is attached to the main rollers 8 and 9, and forms a wire row on the upper side and the lower side of the main rollers 8 and 9.

  In addition, the wire 103 is a conductor, and the supplied voltage is supplied from the power supply 104 to the wire 103 by contacting the wire 103 with the power supply 104 of the power supply unit 10 supplied with the voltage from the power supply unit 2. To be applied. (The power supply 104 applies a voltage to the wire 103.)

Then, electric discharge occurs between the wire 103 and the silicon ingot 105, and the silicon ingot 105 is shaved (electric discharge machining is performed), so that a thin plate silicon (silicon wafer) can be formed.
FIG. 3 will be described.
FIG. 3 shows an enlarged view of the power supply 104.
The power supply 104 (1 piece) is in contact with the wire 103 (10 pieces).
The distance between the wires 103 (wire pitch) is about 0.3 mm (300 μm).
FIG. 4 will be described.
FIG. 4 is a diagram showing an electric circuit 400 with individual power feeding that feeds a discharge current individually for each wire, which is a conventional method.

  Reference numeral 401 denotes a machining power source (Vm). This voltage is set to supply a current necessary for electric discharge machining. Vm can be set to any voltage between 60V and 150V.

Reference numeral 402 denotes a machining power source (Vs). It is a voltage set to induce discharge. Furthermore, it is also used for the purpose of monitoring the state of the interelectrode voltage (interelectrode current) between the wire and the workpiece. Vs can be set to any voltage between 60V and 300V. Reference numeral 403 denotes a transistor (Tr2). The processing power source Vm is switched between ON (conductive) state and OFF (non-conductive) state by switching.
Reference numeral 404 denotes a transistor (Tr1). The processing power supply Vs is switched between ON (conductive) state and OFF (non-conductive) state by switching.

  Reference numeral 405 denotes a current limiting resistor (Rm). By setting a fixed resistance value, each wire current (Iw) and discharge current (Ig) are limited. Rm can be set to an arbitrary resistance value of 1Ω to 100Ω. That is, when Vm = 60V (volt), Vg = 30V, and Rm = 10Ω, Iw (Ig) = (60V−30V) / 10Ω = 3A (ampere).

  In the above calculation formula, the voltage drop from the machining power source to the feed point is 30 V, but the voltage drop from the feed point to the discharge point due to the wire resistance (Rw) is not taken into consideration.

  That is, in the case of the individual power feeding method that is the conventional method, Iw is determined by Rm. Therefore, in order to obtain a desired wire current (Iw) and discharge current (Ig) for each wire, the wire resistance Rw is Rm. > Rw is set.

Reference numeral 406 denotes a current limiting resistor (Rs). Setting a fixed resistance value limits the current that induces the discharge. Rs can be set to an arbitrary resistance value of 1Ω to 100Ω.
Reference numeral 407 denotes an interelectrode voltage (Vg). This is a discharge voltage applied between the wire 103 and the workpiece 105 during discharge.
Reference numeral 408 denotes an interelectrode current (Ig). This is a discharge current that flows between the wire 103 and the workpiece 105 during discharge.
Reference numeral 410 denotes a wire current (Iw) supplied individually for each wire.
FIG. 5 will be described.
FIG. 5 is a diagram in which a conventional electric circuit 400 for supplying a discharge current for each wire individually supplies power to a plurality of wires.
Reference numeral 409 denotes a wire resistance (Rw) indicating the resistance of each wire.
Reference numeral 204 denotes an individual power supply. Electric discharge machining is performed by applying electric discharge pulses from two individual supply electrons provided near both ends of the silicon ingot 105.
The same number of power supply circuits 400 as the number of wires 103 to be wound are connected.

  FIG. 6 shows changes in the inter-electrode voltage (Vgn) and inter-electrode current (Ign) of the present invention, and ON / OFF operations (timing charts) of Tr1 and Tr2. The horizontal axis of the graph is time.

First, the transistor Tr1 is turned on and a voltage is applied. At this time, since the wire 103 and the workpiece 105 are insulated, almost no inter-electrode current flows. Thereafter, when the discharge is started, the voltage Vgn drops. When the discharge is detected and Tr2 is turned on, a large inter-electrode current is obtained. Tr2 is turned off after a predetermined time has elapsed. A series of operations is repeated again after a predetermined time has elapsed after turning off Tr2.
FIG. 7 will be described.

FIG. 7 is a diagram showing an electric circuit 2 with collective feeding in which a discharge current is fed collectively to a plurality of wires (10) in the present invention. A state in which a discharge current is flowing is shown.
The equivalent circuit with the electric circuit 2 shown in FIG. 8 is shown.

If the conventional electric circuit 400 shown in FIG. 4 is introduced as it is into an electric circuit for batch power feeding that feeds a discharge current to a plurality of wires (10 wires) at once, it is between the processing power source and the feeding point. In order to control the discharge current, instead of the current limiting resistor Rm405, Rm is set to 10 so that a total of (10 times) the discharge current supplied to the plurality of wires (10 wires) is supplied. What is necessary is just to install the current limiting resistor of the resistance value divided by the book (the number of times of winding the main rollers 8 and 9) between the machining power source and the feeding point.
First, a case where Rm / 10 having such a fixed resistance value is installed between the machining power supply and the power supply will be described.

  When the discharge state occurs uniformly and simultaneously between all 10 wires and the workpiece, the discharge current is evenly distributed over the 10 wires, so that the fixed resistance value (Rm / 10) Since a discharge current according to the above is supplied between each wire and the workpiece, supply of an excessive discharge current does not cause a problem.

  However, when the discharge state between all ten wires and the workpiece does not occur uniformly and simultaneously, the wire in which the discharge current corresponding to the fixed resistance value (Rm / 10 pieces) is in the discharge state Therefore, supply of excessive discharge current becomes a problem. In other words, when only one of the ten wires is in a discharge state, a discharge current that is 10 times the discharge current that should be supplied to the wire and the workpiece is The wire is broken by being supplied to the workpiece.

  The resistance value Rmn 505 of the present invention does not fix the resistance value to a predetermined value as in the current limiting resistor of the conventional method, and even when only one of the 10 is in a discharge state, A mechanism is provided that can control the resistance value to vary depending on the number of discharges.

  Furthermore, by varying the resistance value Rmn505 of the present invention in a range of resistance values sufficiently smaller than that of Rwn509, Rwn509 becomes dominant in limiting the discharge current, and the influence of Rmn505 can be almost ignored.

  That is, it is not necessary to provide a resistor that limits the lower limit of the current discharged to the workpiece 105 between the machining power supply unit 501 and the power supply 104. In other words, the resistance value may be smaller than the resistance value obtained by dividing Rmn by 10 (the number of turns around which the main rollers 8 and 9 are wound).

That is, by using the impedance which is the resistance Rwn 509 of each wire, the discharge current Ign of each wire is stably supplied, so that no concentration of the discharge current occurs.
Reference numeral 509 denotes a resistance (Rwn) for each wire.
Here, the resistance value from the power supply 104 to the discharge unit is a resistance due to a single wire that is in contact with the power supply 104 and travels.
For example, let Rw1, Rw2, and Rw10 be the wire resistances when supplying power to 10 wires (the main rollers 8 and 9 are wound 10 turns) in a lump.

  As in the conventional method, instead of Rmn, Rwn is a resistor that limits the wire current (Iw) or discharge current (Ig) for each wire, so that the wire current (Iwn) or discharge current (Ign) for each wire is reduced. Can be limited. That is, an arbitrary resistance value can be set by changing the distance (length L) between the power feeding point (power supply) and the discharge point (discharge part). That is, when Vmn = 60V, Vgn = 30V, and Rwn = 10Ω, Iwn (Ign) = (60V−30V) / 10Ω = 3A.

  In the above calculation formula, the voltage drop from the feed point to the discharge point due to the wire resistance (Rwn) is 30 V, but the feed point to the discharge point due to the resistor (Rmn) causing the voltage drop from the machining power source to the feed point. The voltage drop up to is not considered.

  In other words, in the case of the collective power supply method according to the present invention, Iwn is determined by Rmn. Therefore, in order to obtain a desired wire current (Iwn) or discharge current (Ign) for each line, the power supply point from the machining power supply. The resistance Rmn that causes a voltage drop up to is set so that Rmn <Rwn.

  The wire resistance Rwn for each wire is calculated from the following three parameters: (1) electrical resistance value ρ depending on the wire material, (2) wire cross-sectional area B, and (3) wire length L. Rwn = (ρ × B ) / L.

Reference numeral 501 denotes a machining power supply unit (Vmn). This voltage is set to supply a current necessary for electric discharge machining. Vmn can be set to an arbitrary voltage. Furthermore, since the supply amount of the discharge current is larger than that of the conventional method, a larger amount of electric power is supplied than 401.
The machining power supply unit 501 supplies machining power (Vmn) to the power supply 104.

Reference numeral 502 denotes a machining power supply unit (Vsn). It is a voltage set to induce discharge. Furthermore, it is also used for the purpose of monitoring the state of the interelectrode voltage (interelectrode current) between the wire and the workpiece. Vsn can be set to an arbitrary voltage. Furthermore, since the supply amount of the discharge current is larger than that of the conventional method, a larger amount of electric power is supplied than 402.
The machining power supply unit 502 supplies a machining power supply (Vsn) to the power supply 104.
Reference numeral 503 denotes a transistor (Tr2). The processing power supply Vmn is switched between ON (conductive) state and OFF (non-conductive) state by switching.
Reference numeral 504 denotes a transistor (Tr1). The processing power source Vsn is switched between ON (conductive) state and OFF (non-conductive) state by switching.
Reference numeral 507 denotes an interelectrode voltage (Vgn). This is a discharge voltage applied between the wire 103 and the workpiece 105 during discharge.
For example, the discharge voltages when collectively supplying power to 10 wires are Vg1, Vg2, and .about.Vg10, respectively.

A portion where an inter-electrode voltage is applied between the wire 103 and the workpiece 105 by discharge is a discharge portion. In the discharge part, the machining power supplied in a batch to the plurality of wires traveling by contact between the plurality of traveling wires and the power supply is discharged to the workpiece.
Reference numeral 508 denotes an interelectrode current (Ign). This is a discharge current that flows between the wire 103 and the workpiece 105 during discharge.
For example, the discharge currents when power is supplied to 10 wires at once are Ig1, Ig2, and .about.Ig10, respectively.

  A portion where an interelectrode current flows between the wire 103 and the workpiece 105 due to the discharge is a discharge portion. In the discharge part, the machining power supplied in a batch to the plurality of wires traveling by contact between the plurality of traveling wires and the power supply is discharged to the workpiece.

Reference numeral 510 denotes a wire current (Iwn) supplied individually for each wire. For example, each wire current when power is supplied to 10 wires at once is assumed to be Iw1, Iw2, and .about.Iw10, respectively.
Reference numeral 511 denotes a distance L from the feeding point to the discharging point, that is, the length of the wire from the feeding point to the discharging point.
FIG. 8 will be described.
FIG. 8 is a diagram in which a plurality of wires (10 wires) according to the present invention are collectively fed to a plurality of wires by an electric circuit 2 in a batch feeding that feeds a discharge current all at once.

Reference numeral 104 denotes a power supply. The power supply 104 contacts a plurality of traveling wires at once. Electric discharge machining is performed by applying an electric discharge pulse from a single supply electron 104 provided at a position facing the silicon ingot 105.
One power supply circuit 2 is connected to the number (10) of wires 103 around which the main roller is wound.
Hereinafter, description will be given with reference to the arrangement of FIG.

As shown in FIG. 8, since the current flowing from the power supply point (position where the power supply 104 and the wire 103 contact) to the discharge point (between the wire 103 and the workpiece 105) flows in two directions of the left and right main rollers, There is a wire resistance to the direction.
511L1 is the length (distance) between the power supply point and the discharge point when the current flows in the direction of the left main roller, and the wire resistance determined in the case of L1 is Rw1a.
511L2 is the length (distance) between the discharge point and the feed point when the current flows in the direction of the right main roller. The wire resistance determined in the case of L2 is Rw1b.
The length that the wire 103 winds the main rollers 8 and 9 once is set to 2 m.
Since the power supply 104 is arranged at a distance approximately half the length of one turn, the distance between the discharge point and the power supply point (the length L of the wire) is 1 m.
Therefore, the distance of the wire that travels from the power supply to the discharge unit is longer than 0.5 m.

The main component of the material of the wire 103 is iron, and the diameter of the wire is 0.12 mm (cross-sectional area 0.06 × 0.06 × πmm ² ). Since the resistance values Rw1a and Rw1b of the wires are the same length (L1 = L2 = 1 m), if each wire resistance value is about the same 20Ω, one of Rw1a and Rw1b (one main roller 8, 9 is 1). The combined wire resistance value is about 10Ω.

Here, when calculating the loss due to the resistance value of the wire electrode itself (in the case of 20Ω) per wire electrode (1 m) from the power supply (feed point) to the work (work),
Since half of Iw1 × half of Iw1 × Rw1a × DutyFactor (ratio of discharge ON time) is power loss (Ws),

  Ws = 1.5A × 1.5A × 20Ω × 0.5 = 22.5W, and heat generation corresponding to Ws = 22.5W is generated per wire electrode. That is, in proportion to the number N of wire electrodes, this Ws also becomes N times, so that cooling of the wire electrode itself and cooling of the portion in contact with the wire electrode are required.

  Therefore, in the first cooling unit, when the machining power is supplied to the wire electrodes arranged in parallel via the power supply, the wire electrodes arranged in parallel by the rotation of the plurality of guide rollers run in the same direction. The part where the surface of the guide roller is in contact with the wire electrode (the first part) needs to be cooled regardless of whether or not it is done.

  In other words, even when the wire electrodes arranged in parallel by the rotation of the plurality of guide rollers are not traveling in the same direction, the surface of the guide roller that is far from the position of the electron supply must be cooled.

Further, as shown in FIG. 8, in order to make the wire resistance value according to the lengths of L1 and L2 the same resistance value, it is preferable to arrange the power supply 104 so that the lengths of L1 and L2 are the same. There is no particular problem even if the power supply 104 is arranged so that the difference in length between L2 and L2 is about 10% (for example, L1 is 1 m and L2 is 1.1 m).
When the discharge voltages Vg1 to Vg10 are substantially equal, since Vmn is applied to each of Rw1 to Rw10, Iw1 to Iw10 are all the same wire current.
Here, Vmn is obtained from the voltage drop value (Rw1 × Iw1) due to the wire resistance and the discharge voltage (Vgn).
The voltage drop from the power supply 104 to the discharge part is a voltage drop due to the resistance of the traveling wire.
Rw1 = 10Ω (resistance value from the power supply 104 to the discharge part).

Iw1 = 3A
If Vgn = 30V, Vmn is as follows.
Vmn = 10 (Ω) × 3 (A) + 30V = 60V
Therefore, the voltage drop from the power supply to the discharge part is larger than 10V.
Therefore, the resistance value from the power supply to the discharge part is larger than 1Ω.
Note that the voltage drop value due to the wire resistance may be set by the wire parameter according to the relational expression of Rwn = (ρ × B) / L.

Therefore, when Rmn is calculated when the discharge state occurs uniformly and simultaneously between all the 10 wires and the workpiece, the discharge state occurs in all the wires, and Iw1 = 3A flows through the 10 wires. A total machining current of 10 × 3A = 30A is required between the machining power source and the feed point, and the voltage drop between this machining power source and the feed point is 1 / 100th of Vmn (0.6V). Then, Rmn in this case is as follows.
Therefore, the voltage drop from the machining power supply unit to the power supply 104 is smaller than 1V.
Therefore, the voltage drop from the machining power supply unit to the supply unit is smaller than the voltage drop from the supply unit to the discharge unit.
Rmn = 0.6V / 30A = 0.02Ω (resistance value from the processing power supply unit 501 to the power supply 104).
Therefore, the resistance value from the machining power source to the power supply is less than 0.1Ω.
Therefore, the resistance value from the machining power supply unit to the supply unit is smaller than the resistance value from the supply unit to the discharge unit.
Therefore, the ratio of the voltage drop from the machining power supply unit to the supply unit 104 and the voltage drop from the supply unit 104 to the discharge unit is 10 times or more.
Therefore, the ratio of the resistance value from the machining power supply unit to the power supply 104 and the resistance value from the power supply unit to the discharge unit is 10 times or more.
Therefore, when 10 machining currents are calculated in consideration of Rmn, (60V-30V) / ((10Ω / 10 pieces) + 0.02Ω) = 29.41A, and the machining current per wire is 2.941A.

  Moreover, even if one wire current flows when the discharge state does not occur uniformly and simultaneously between all 10 wires and the workpiece, the machining current per wire is (60V-30V) / (10Ω + 0.02Ω) = 2.994 A, so that there is no significant difference even when the discharge state occurs uniformly and simultaneously between all ten wires and the workpiece.

As a further effect, when power is supplied to a plurality of N wires (the main rollers 8 and 9 are wound N times) at one location (in a lump), power is supplied individually for each wire. The machining speed is 1 / N compared to the machining speed at that time, but according to the present invention, even when power is supplied to one wire (in a lump) to N wires, the power is supplied individually to one wire. The same processing speed can be maintained.
FIG. 9 will be described.
It is the figure which showed the case where the electric power supply which supplies electric power to 100 wires collectively is arrange | positioned.
In this case, the length of one power supply is about 30 cm.

  In the multi-wire electric discharge machining system of the present invention, the total current of machining current supplied to the wire from one machining power source and one feeder is not proportional to the number of wires in contact with the feeder, but in the discharge state. Is proportional to the number of wires that occur uniformly and simultaneously,

  As described with reference to FIG. 8, when the discharge state occurs between the 10 wires and the workpiece uniformly and simultaneously, the total machining current supplied to the 10 wires is calculated in consideration of Rmn. As a result, (60V-30V) / ((10Ω / 10 wires) + 0.02Ω) = 29.41A. At this time, the machining current flowing per wire is 2.941A.

  Therefore, when the discharge state occurs uniformly and simultaneously between all 100 wires and the workpiece, the total current (maximum) of the machining current supplied to the 100 wires is calculated in consideration of Rmn. (60V-30V) / ((10Ω / 100 wires) + 0.02Ω) = 250 A, and the machining current flowing per wire at this time is 2.5 A.

  As described above, if 100 wires are fed all at once from one processing power source and one power supply, and the discharge state occurs between the 100 wires and the workpiece uniformly and simultaneously, 60V is applied. A large machining power supply capacity of × 250 A = 15 kW is required.

In addition, if one processing power source and one power supply are used to supply power to 100 wires at once and the discharge state is uniform and occurs only between the 10 wires and the workpiece, processing is performed. The power supply capacity is 60V x 29.41A = 1.7kW, and the fluctuation range of the total current supplied to the wire where the discharge state is uniform and simultaneous between the wire and the workpiece increases, and the total current is reduced. The load of the machining power source for controlling increases.
FIG. 10 will be described.
FIG. 10 is a diagram showing a case where the power supply for supplying power is collectively arranged on 20 wires.
In this case, the length of one power supply is about 6 cm.

  At this time, if the discharge state occurs uniformly and simultaneously between all 20 wires and the workpiece, the total current (maximum) of the machining current supplied to the 100 wires is obtained in consideration of Rmn. (60V-30V) / ((10Ω / 20 wires) + 0.02Ω) = 57.69A, and the machining current flowing per wire at this time is 2.8846A.

  In this way, when 20 wires are collectively fed from one processing power source and one power supply, and the discharge state occurs uniformly and simultaneously between the 20 wires and the workpiece, 60V × 57.69 A = 3.4 kW, compared to the case of FIG. 9, a large machining power supply capability is not required, and the total current supplied to the wire in which the discharge state is uniformly and simultaneously occurring between the wire and the workpiece The variation width of the machining power is reduced, and the load of the machining power source for controlling the total current is reduced.

  In consideration of electrical protection when a short circuit occurs in a cable or the like on the load side of the machining power source, it is appropriate to set it to several tens of A per unit of the machining power source. Since the maximum value of the current flowing per wire can be limited by the resistance Rwn of each wire, assuming that the current flowing through one wire is 3A, for example, the supply current of the machining power supplied to one electron supply is 30A. If a machining power source is used, the number of wires to be collectively fed is 10 or less, or if a machining power source having a supply current of 60 A is used, if the number of wires to be fed collectively is limited to 20 or less, the machining power source Never exceed the supply capacity.

Therefore, when supplying power to 100 wires, if the machining power supply having the same supply capacity is set to 5 units or 10 units, and 5 or 10 power supply units are provided so as to correspond respectively, the machining power supply capacity Can be maintained (a machining power supply unit that individually supplies machining power for each electric power supply).
FIG. 11 will be described.
FIG. 11 is a diagram showing a case where the power supply for supplying power is collectively arranged on 20 wires.

  When the power supplies are arranged side by side as shown in FIG. 10, a gap is formed between adjacent (adjacent) power supplies. The distance (pitch) between the wires arranged in parallel according to the present invention is about 0.3 mm (300 μm), and there is a problem that power is not supplied to the wires that run through the gap between the adjacent supply electrons. Therefore, the gap problem can be solved by arranging the adjacent power supply so as not to be aligned in the direction perpendicular to the direction in which the wire travels as shown in FIG.

Further, if the set of the supply electrons that are arranged so as not to be aligned is arranged so as to be repeatedly aligned in the direction perpendicular to the direction in which the wire travels, the space width generated by spreading the supply electrons is reduced. This eliminates the need to secure the space necessary for arranging the power supply side by side on the wire surface, and allows the multi-wire electric discharge machining apparatus to be designed in a compact manner.
FIG. 12 will be described.
FIG. 12 is a diagram showing a case where the power supply for supplying power is collectively arranged on 20 wires.

  When the feeders are arranged side by side as shown in FIG. 11, high accuracy is required for the interval and position between the arranged feeders, which is very important when replacing the feeders that need to be replaced periodically due to deterioration and rearranging them. It will be a hassle.

  According to the present invention, the number of wires that are in contact with two adjacent two supply electrons may be any number, and the number of wires that are in contact with each other is not constant. There is no particular problem even if they are arranged. For example, when 100 power supply units are arranged, it is not necessary to arrange the supply units evenly with high positional accuracy, and if all the wires are arranged to overlap, it is possible to supply power to all the wires. Details of the reason will be described with reference to FIG.

In addition, a power control unit is provided for controlling the machining power to be supplied individually so that the pulses of the machining power supplied to two adjacent power supply electrons are the same. If the same pulse is not supplied, the applied pulse conditions (time, etc.) will be different between the overlapping part and the non-overlapping part, resulting in different electric discharge machining conditions. .
FIG. 13 will be described.
FIG. 13 shows a case where two adjacent supply electrons (A and B) are arranged so as to be in contact with a part of a plurality of wires in an overlapping manner.

As described above, since the maximum value of the current flowing per wire can be limited by the resistance Rwn of each wire, the combined current value of Iw8 + Iw1 ′ flowing in the overlapping wire and the non-overlapping wire Since the single current value of Iw7 flowing in the flow is substantially equal, the workpiece machining accuracy does not become uneven between the overlapping wires and the non-overlapping wires.
FIG. 14 will be described.

FIG. 14 shows all the wire electrodes and guide rollers arranged side by side so that the first cooling unit (two) sprays the cooling water on the surfaces (contact surfaces with the wire electrodes) of the guide rollers (two). It is the figure which showed the state which disperse | distributes and cools cooling water toward the bottom from the upper than (two).
FIG. 15 will be described.

  FIG. 15 shows that the second cooling unit (one) has all the wire electrodes arranged in parallel and the power supply (so that the cooling water is sprayed on the surface of the power supply (many) (contact surface with the wire electrode). Although it is the figure which showed the state which is disperse | distributing and injecting cooling water toward the upper direction from the lower than a large number), the arrangement | positioning position of a supplied electron is temporarily lower than a wire electrode, and the surface of a supplied electron (a large number) In the case where the cooling water is arranged so as to be in contact with each other, there is no problem even if the cooling water is dispersed and sprayed from the upper side to the lower side than all the wire electrodes arranged in parallel and the supply electrons (many).

  The semiconductor ingot sliced by the multi-wire electric discharge machining system of the present invention can be used as a substrate for a semiconductor device or a substrate for a solar cell.

DESCRIPTION OF SYMBOLS 1 Multi-wire electric discharge machining apparatus 2 Processing power supply apparatus 103 Wire electrode 104 Electric supply 105 Workpiece | work (silicon ingot)
201 1st cooling unit 202 1st cooling unit 203 2nd cooling unit

Claims (7)

A multi-wire electric discharge machining system for slicing a workpiece at an interval between parallel wire electrodes,
A plurality of guide rollers for running the wire electrodes arranged side by side in the same direction;
A power supply for supplying a machining power to the wire electrodes arranged in parallel;
A first cooling unit that cools a first portion where the juxtaposed wire electrodes and the plurality of guide rollers are in contact;
With
The multi-wire discharge, wherein the first cooling unit cools the first part when the machining power is supplied to the wire electrodes arranged in parallel via the power supply. Processing system.   The first cooling unit further includes the wires arranged in parallel by rotation of the plurality of guide rollers when the machining power is supplied to the wire electrodes arranged in parallel via the power supply. 2. The multi-wire electric discharge machining system according to claim 1, wherein the first portion is cooled regardless of whether the electrodes are traveling in the same direction.   3. The multi-wire electric discharge machining system according to claim 1, further comprising a second cooling unit that cools a second portion where the wire electrode arranged in parallel and the power supply are in contact with each other.   The first cooling unit and the second cooling unit inject cooling water onto the surfaces of the wire electrodes arranged in parallel to cool the first part and the second part. Item 4. The multi-wire electric discharge machining system according to item 3. A first setting unit for setting an injection pressure of cooling water injected toward the first part;
A second setting unit for setting an injection pressure of cooling water injected toward the second part;
Further comprising
The first setting unit and the second setting unit are set such that an injection pressure injected into the second part is lower than an injection pressure injected into the first part. The multi-wire electric discharge machining system according to claim 4. A processing tank for supplying ion-exchanged water managed to have a specific resistance in a predetermined range as a processing liquid to a position where the parallel wire electrode and the workpiece are close to each other,
An ion exchange resin that manages the specific resistance of the cooling water such that the specific resistance of the injected cooling water is substantially equal to the specific resistance of the ion exchange water;
The multi-wire electric discharge machining system according to claim 4 or 5, further comprising: Slice the workpiece at the interval between the wire electrodes arranged side by side,
A plurality of guide rollers for running the wire electrodes arranged side by side in the same direction;
A power supply for supplying a machining power to the wire electrodes arranged in parallel;
A first cooling unit that cools a first portion where the juxtaposed wire electrodes and the plurality of guide rollers are in contact;
A multi-wire electric discharge machining method by a multi-wire electric discharge machining system comprising:
The multi-wire discharge, wherein the first cooling unit cools the first part when the machining power is supplied to the wire electrodes arranged in parallel via the power supply. Processing method.

Images