DE102015204275B3 - Method for resuming a wire-cutting operation with structured saw wire after interruption - Google Patents

Abstract

The present invention relates to a method of resuming a wire-cut wire lapping process of a cylindrical workpiece into a plurality of disks after breaking and removing the saw wire from the workpiece, including re-inserting a saw wire into the formed separation gap and moving saw wire until uniform at the location of the cut interruption without damaging the separating column.

Description

The present invention relates to a method according to the preamble of claims 1, 9 and 13 for resuming wire-cut lapping of a cylindrical workpiece into a plurality of disks after breaking and removing the saw wire from the workpiece, including re-inserting a saw wire in the formed separating gaps and a uniform movement of the saw wire up to the location of the cut interruption without damaging the separating column.

For many applications, a variety of similar slices of certain starting materials is required, for example, glass sheets as substrates for the production of magnetic storage disks, discs of sapphire or silicon carbide as a base for the production of optoelectronic components or semiconductor wafers for the production of photovoltaic cells ("solar cells") or as substrates for structuring electronic , microelectronic or microelectromechanical components. Washers as substrates for electronic components or photovoltaic cells are also referred to as wafers.

The distance from the front and back of a disc to each other is referred to as the thickness of the disc and the curvature of the central surface between the front and back as a shape of the disc. Thickness and shape together form the geometry of the disk, with a particularly uniform thickness and a low curvature shape corresponding to good geometry and a nonuniform thickness and strongly curved shape to a poor geometry. For demanding applications, discs must have a particularly good geometry.

The starting material from which the discs are separated is usually in the form of a cylindrical rod (workpiece). A cylinder is limited by a flat base, a top surface and a lateral surface. Base and top surfaces are also referred to as end surfaces.

The separation of slices from a workpiece is done by canceling the material cohesion along separating surfaces. For a plurality of uniform planar discs, the parting surfaces must be flat, perpendicular to the workpiece axis, and adjacent parting planes must be equidistant from one another. The dissolution of the material cohesion is usually done by chip-removing process. The term span refers to a particle released from the workpiece. The volume of material removed along a parting plane by chip removal is referred to as a separation nip. For certain applications, the separating gaps may also deviate from the perpendicular to the workpiece axis by small angles, for example up to 2 °.

Under the chip-removing method for cutting a workpiece into a plurality of similar, thin slices with a particularly uniform thickness and particularly low curvature of their shape, the Drahttrennläppen (wire saws) has special significance.

The saw wire used to sever a rod consists, for example, of hardened steel (piano wire), plastics, carbon fibers or metal alloys. The wire may comprise one element (monofilament wire) or may be stranded from multiple elements, which may also comprise different materials. Saw wires for use in wire saws are for example in EP0 799 655A1 . US 6,194,068 B1 or DE 10 2012 007 815 A1 disclosed.

In addition to the disclosed in the above-mentioned documents smooth wire, so a circular cylinder of very high height, so-called structured wire can be used for Drahttrennläppen of workpieces.

A structured wire comprises a straight, straight wire which is provided over its entire run length continuously or at regular intervals with zigzag sequences of protuberances and indentations in the form of waves, creases or bumps produced by plastic deformation of the smooth-wire. These deformations are often commonly referred to by the English words "kinks" or "crimps" and may extend in one, two orthogonal or arbitrary planes containing the central wire longitudinal direction.

The surface of a structured wire thus has recesses and elevations in which slurry can attach to the wire without being stripped by the separation gap upon entry of the wire into the separation gap or in the further wire path. This additional slurry supply in the pockets of the depressions causes the structured wire to introduce more slurry into the separating gap than a smooth wire of comparable diameter.

As a result, wire stripping with structured wire can achieve, among other things, higher chip removal rates and better geometry disks than a comparative cut with a smooth wire of a diameter equal to the effective diameter of the patterned wire.

The material removal rate is the volume of material removed by the separation process per unit of time in the form of chips from the workpiece.

Examples of patterned wire suitable for wire-severing lapping are described, for example, in US Pat EP 1 827 745 B1 . US 2,860,862 A . JP 4 057 666 A2 . WO 12 069 314 A1 and WO 14 036 714 A1 ,

During a wire-cutting operation, the saw wire occasionally ruptures. For example, a wire tear may be caused by excessive wire friction in the separation gap and thereby excessive wire tension between the wire guide rollers, or by defects in the wire itself, for example, in the form of inclusions or excessive wear.

A wire tear will interrupt the separation lapping process. In most cases, in order to be able to repair the broken wire, the partially sawed-in workpiece must be moved out of the wire gate completely. After repair of the wire gate, the workpiece must then first be driven back into the wire gate, that in each separation gap exactly one wire section comes to rest, and then be delivered exactly perpendicular to the wire gate plane and without displacement of the wire gate in the direction of the workpiece axis until the Wire gate again came to rest at the site of the cut interruption in the workpiece.

The threading and advancement of the rod down to the cutting depth of the cut interruption is also called repositioning.

If the separation of slices from a workpiece is interrupted unscheduled, for example by a wire tear (wire break), the saw wire, the wire guide rollers and the workpiece cool again, and it can lead to a contraction of the guide rollers and the workpiece (thermally induced change in length). These contractions are usually different, so that there may be variations in thickness of the obtained after complete separation from the workpiece slices. Local thickness variations of the discs are also referred to as sawing depths.

However, particularly troublesome are disturbances of the flatness of the surfaces of the slices obtained after complete separation from the workpiece. This is called curvature, warping or waviness (warp).

In order to avoid a deterioration of the thickness uniformity of the discs or the flatness of the disc surfaces in the resumption of the Trennläppvorgangs, discloses the document DE 11 2009 001 747 T5 a method for resuming a wire sawing process, wherein after an unscheduled stop and before the resumption of the wire sawing process, the temperature of the workpiece and the relevant parts of the wire saw (saw wire and guide rollers) is ensured by a temperature-adjusting medium to the temperature before the interruption.

According to DE 10 2012 221 904 A1 For the resumption of an interrupted separation lapping process, a special pilgrim step method is preferred in which, at the beginning of the continuation of the separation process, the saw wire is first moved by a first length in a first direction and then by a second length in a second direction opposite to the first direction, wherein the second length is shorter than the first length. Per cycle, ie moving the wire in the first and in the second direction, the first length is increased while the second length remains constant until, after a suitable selected number of pilgrim steps, the first length is so long that they are exactly the same an uninterrupted separation process at the respective depth of cut is equal. By this method, it can be avoided that at the location of the cut interruption a thickness jump ("step") is formed in the already sawn slices.

It has now been found that the methods known in the state of the art for cutting continuation after interruption while moving the workpiece out of the wire gate are unsuitable for structured wires, since the surfaces of the slices which have already been partly separated from a workpiece by a pilgrim step method have unevennesses. These irregularities result from the constant reversal of direction from left to right and right again from the left to the next moment in the separating gap, whereby the walls of a separating gap produced by pilgrimage processes (ie the subsequent wafer surfaces) are irregular (grooves) perpendicular to the feed direction of the workpiece. exhibit. These bumps can, for example, cause snagging or increased friction on the surfaces of individual wire sections when reintroducing the wire gate in the existing Sägespalte.

The snagging of individual wire sections of the wire gate can, due to the slippage on the wire guide rollers, lead to a disadvantageous change in the wire tension of adjacent wire sections in the wire gate up to the renewed rupture of the wire.

The increased friction of the saw wire in reintroducing the wire gate into the existing kerf may result in deterioration of the nanotopology to irreparable grooves in the surfaces of the slices already partially separated from the workpiece. The term nanotopology refers to the local local unevenness, ie the deviations from the mean level of compensation within certain measuring windows, which are related to the later front (components-carrying side) of the received wafers. A good nanotopology (low height fluctuations of the wafer front side) is particularly important for the later production of highly integrated, in particular multilayer, microelectronic components.

It is an object of the present invention to provide a method of resuming wire-cut wire cutting lapping of a cylindrical workpiece into a plurality of disks after breaking and removing the separator wire from the workpiece, reintroducing a saw wire into the formed separation gap, and smoothly moving the saw wire up to the site of the cut interruption while avoiding economically unreasonable or irreparable damage to the separating gaps bounding surfaces allows.

• a) das Entfernen des ersten Drahtgatters aus den im Werkstück 1 durch das erste Drahtgatter gebildeten Trennspalten 4b
• b) das Wiedereinführen eines durch mindestens zwei Drahtführungsrollen 6 mit einer zweiten Drahtspannung aus einem strukturierten Draht 5 aufgespannten Drahtgatters in die Trennspalte 4,

und die strukturierten Drähte 5 im ersten und im zweiten Drahtgatter im Neuzustand bei der gleichen Drahtspannung den gleichen Wirkdurchmesser 9 haben, dadurch gekennzeichnet, dass vor dem Einführen der Drahtabschnitte des zweiten Drahtgatters in die vorhandenen Trennspalte 4 die zweite Drahtspannung größer ist als die erste Drahtspannung.The object is achieved by a first method according to claim 1 for resuming an incomplete separation of a workpiece 1 in a variety of slices with a textured wire 5 passing through at least two wire guide rollers 6 to a first wire gate comprising a plurality of parallel wire sections having a first wire tension and having a first effective diameter 9 spanned, comprehensively

• a) the removal of the first wire gate from the in the workpiece 1 separating gaps formed by the first wire gate 4b
• b) the reintroduction of one by at least two wire guide rollers 6 with a second wire tension of a structured wire 5 spanned wire gate in the separating column 4 .

and the structured wires 5 in the first and in the second wire gate in new condition at the same wire tension the same effective diameter 9 have, characterized in that prior to the insertion of the wire sections of the second wire gate in the existing separation gaps 4 the second wire voltage is greater than the first wire voltage.

• a) das Entfernen des ersten Drahtgatters aus den im Werkstück 1 durch das erste Drahtgatter gebildeten Trennspalten 4b
• b) das Wiedereinführen eines durch mindestens zwei Drahtführungsrollen 6 mit einer zweiten Drahtspannung aus einem strukturierten Draht 5 aufgespannten Drahtgatters in die Trennspalte 4,

und die strukturierten Drähte 5 im ersten und im zweiten Drahtgatter im Neuzustand bei der gleichen Drahtspannung den gleichen Wirkdurchmesser 9 haben, dadurch gekennzeichnet, dass jeweils zwischen dem Werkstück 1 und den zwei zum Werkstück benachbarten Drahtführungsrollen 6 jeweils mindestens eine Stützrolle 25 so angeordnet ist, dass die mindestens eine Stützrolle 25 ein Durchbiegen 12 der Drahtabschnitte im zweiten Drahtgatter in Richtung der Werkstückzustellung begrenzt.The object is also achieved by a second method according to claim 9 for resuming an incomplete separation of a workpiece 1 in a variety of slices with a textured wire 5 passing through at least two wire guide rollers 6 to a first wire gate comprising a plurality of parallel wire sections having a first wire tension and having a first effective diameter 9 spanned, comprehensively

• a) the removal of the first wire gate from the in the workpiece 1 separating gaps formed by the first wire gate 4b
• b) the reintroduction of one by at least two wire guide rollers 6 with a second wire tension of a structured wire 5 spanned wire gate in the separating column 4 .

and the structured wires 5 in the first and in the second wire gate in new condition at the same wire tension the same effective diameter 9 have, characterized in that in each case between the workpiece 1 and the two wire guide rollers adjacent to the workpiece 6 in each case at least one support roller 25 is arranged so that the at least one support roller 25 a bending 12 limits the wire sections in the second wire gate in the direction of the workpiece delivery.

• a) das Entfernen des ersten Drahtgatters aus den im Werkstück 1 durch das erste Drahtgatter gebildeten Trennspalten 4
• b) das Wiedereinführen eines durch mindestens zwei Drahtführungsrollen 6 mit einer zweiten Drahtspannung aufgespannten zweiten Drahtgatters in die Trennspalte 4, dadurch gekennzeichnet, dass bei gleicher Drahtspannung im ersten und im zweiten Drahtgatter der Wirkdurchmesser 9 des ersten Drahtes 5 größer ist als der Wirkdurchmesser des zweiten Drahtes.

The object is also achieved by a third method according to claim 13 for resuming an incomplete separation of a workpiece 1 in a variety of slices with a textured wire 5 passing through at least two wire guide rollers 6 to a first wire gate comprising a plurality of parallel wire sections having a first wire tension and having a first effective diameter 9 spanned, comprehensively

• a) the removal of the first wire gate from the in the workpiece 1 separating gaps formed by the first wire gate 4
• b) the reintroduction of one by at least two wire guide rollers 6 with a second wire tension spanned second wire gate in the separation column 4 , characterized in that at the same wire tension in the first and in the second wire gate of the effective diameter 9 of the first wire 5 greater than the effective diameter of the second wire.

The three methods according to claims 1, 9 and 13 according to the invention will become apparent after the presentation of essential aspects relevant to the method according to the invention, with reference to FIGS 1 to 3 described in detail.

Brief description of the figures:

1 : Repositioning of a structured wire in the separating gap after interruption of cut with a method not according to the invention.

2 : Repositioning a structured wire in the separation gap after interruption of cut according to the first method of the invention.

3 : Repositioning a structured wire in the separating gap after interruption of cut according to the second method of the invention.

4 : Relationship between effective diameter of a sawing wire and the width of a separating gap.

LIST OF REFERENCE NUMBERS

1

workpiece

2

Axis of the workpiece

3

Separation gap reason (location of cut interruption)

4

separating gap

5

structured wire

6

Wire feed roll

7

Axle of wire guide roller

8th

Core diameter of the wire

9

Effective diameter of the wire

10

smooth (straight) wire

12

Wire deflection

13

Exit nozzle for liquid cutting agent

14

Liquid cutting agent

15

unidirectional wire longitudinal movement

16

groove

17

Rotation of the wire guide roller

18

jerky movement (relaxation) of the structured wire 5

19

pinch

20

Axle of the pressure roller

21

Rotation of the pressure roller

22

uniform wire movement through the separating gap

23

Feed movement of the workpiece

25

supporting role

26

Axle of the support roller

27

Rotation of the support roller

28

wear-resistant coating

29

Envelope of the workpiece when fed through the wire gate

30

Feed movement of the pressure roller

31

Height adjustment of the support rollers

A

Amplitude of the zigzag-shaped protuberances and indentations in the transverse direction of a structured wire

D

Diameter or effective diameter of a smooth wire

DL

Wire longitudinally

DW

Effective diameter of a structured wire

D90

Diameter for which 90% of the grains of a distribution have a smaller diameter

k

dimensionless constant

k _E

Spring stiffness of the smooth wire

k _W

Spring stiffness of the structuring

₁

first length of the wire longitudinal movement of a pilgrim step

l ₂

second length of the wire longitudinal movement of a pilgrim step

v ₁

first speed of the wire longitudinal movement of a pilgrim step

v ₂

second speed of the wire longitudinal movement of a pilgrim step

v _eff

Speed of net movement of the wire during a pilgrim step

WT

Expansion of the separation column in the axial direction of the workpiece

An apparatus for wire-cutting (sawing) a workpiece into a plurality of disks is generally referred to as a wire saw. In the DE 195 17 107 C2 as well as the US 5,771,876 are described the functional principle of a wire saw, which is suitable for the production of semiconductor wafers.

Among the essential components of these wire saws include a machine frame, a feed device and a sawing tool, which consists of a gate ("wire web") of parallel wire sections. The spacing of the wires in the wire gate depends on the desired target thicknesses of the slices to be separated and is, for example, 100 to 1000 μm for slices of semiconductor material.

The saw wire used to sever a rod consists for example of a smooth wire such as in EP 0 799 655A1 . US 6,194,068 B1 or DE 10 2012 007 815 A1 disclosed or made of a structured wire, such as in EP 1 827 745 B1 . US 2,860,862 A . WO 12 069 314 A1 and WO 14 036 714 A1 disclosed.

A smooth wire has the shape of a circular cylinder of very high height.

A structured wire comprises a straight, straight wire which, over its entire run length, is referred to as "kinks" or "crimps" continuously or at regular or irregular intervals with zigzagged successions of protuberances and indentations (undulations) in the form of waves, kinks , is provided. These deformations of the patterned wire may extend in one, two orthogonal or arbitrary planes containing the central wire longitudinal direction.

The deformations of the patterned wire may have one or more periodicity lengths (wavelengths) in the wire longitudinal direction and one or more amplitudes (wave heights) in the wire transverse direction. They can each refer to the said Restrict levels or change the levels and, for example helically around the wire longitudinal direction to run (helix).

In general, the wire gate is formed by a plurality of parallel, lying in a plane wire sections, which are spanned between at least two wire guide rollers, wherein the wire guide rollers are rotatably mounted and of which at least one is driven.

The wire sections may belong to a single, finite wire spirally guided around the roller system and unwound from a supply reel (donor coil) to a take-up reel (take-up reel), or, as shown in FIG EP 522 542 A1 Known to run in a variety of endless wire loops around the roller system. The wire sections of the wire gate generally have a defined basic voltage, which can be adjusted by corresponding devices in the wire saw. By this basic voltage or wire tension, it is ensured that the wire sections of the wire gate span without bending the wire gate.

During the separation process, the workpiece is penetrated by the wire gate. The penetration is effected with a feed device which guides the workpiece against the wire gate, the wire gate against the workpiece or the workpiece and the wire gate against each other.

Upon penetration of the wire gate in the workpiece, the saw wire according to the prior art in a defined time at a certain speed for a defined length forward (wire forward) and a further defined length rewound (wire backward), the return length is usually shorter as the lead length. This sawing process is also referred to as pilgrim stepping (or reciprocating movement) and is for example in DE 39 40 691 A1 as in US 2010 1630 10 A2 disclosed. The difference between the lengths of forward movement and the backward movement of the wire over a complete cycle of the pilgrim is also referred to as the length of net movement of the wire over a complete cycle of pilgrimage.

The separation of a workpiece with a wire saw in many slices takes place in the presence of a liquid cutting means, the u. a. provides for the removal of the material removed from the sawing wire from the Sägespalte and preferably applied according to the prior art on the saw wire. The liquid cutting agent preferably contains loose cutting grain (abrasive) that aids in the machining process. Loose abrasive liquid abrasives are also referred to as sawing slurry, sawing slurry, or slurry. In the process according to the invention, the use of liquid cutting agents containing loose abrasives is preferred.

The sawing wire has an effective diameter which determines the width WT of the cutting gap (saw gap) produced by machining the workpiece at the point of contact with the saw wire. The effective diameter of a wire corresponds to the diameter of the projection of the wire along its central longitudinal direction to a plane perpendicular to this central wire longitudinal direction. The shortest closed curve that completely outlines this projection is hereafter called the envelope.

In a smooth wire, which contains no firmly bound cutting means, the effective diameter of the wire diameter D is identical and its envelope runs completely in its lateral surface.

In the case of a smooth wire whose surface is covered with cutting grain or in the case of a structured wire, the effective diameter corresponds to the diameter of the envelope of this wire. The diameter of the envelope is given by the diameter of the wire (core diameter) plus the largest height of the cutting grain or the greatest height of the deformations of the structured wire. The diameter of the envelope is thus the diameter in the plane perpendicular to the wire longitudinal direction, which circumscribes all the tips of the protruding beyond the core diameter protuberances.

If there is a rupture of the saw wire during wire cutting, the cutting of the workpiece can not be completed. To continue the Drahttrennläppens until complete separation of the workpiece in a plurality of discs usually the wire gate must be removed for repair from the workpiece. This is particularly necessary when sawing with the pilgrim step method, since in this case the wire gate is largely destroyed in a wire tear as a result of the continuous reversal of direction of the wire longitudinal movement and usually has to be completely rebuilt. When sawing with unidirectional longitudinal wire movement, the wire tends to rupture on the wire exit side of the workpiece as it is thinner there due to wear and tear and therefore has reduced tear strength. In this case, it is often sufficient to knot or weld the torn wire ends, since often only a single or a few wire sections are torn, and a possibly destroyed area simply "skip" the wire gate until completion of the separation process, i. H. to exclude from the further separation process.

If, after a wire tear, the wire gate has been destroyed so far that it has to be completely rebuilt, the workpiece must first be removed from the wire gate or the wire gate must be removed from the workpiece. After repair of the wire gate, the workpiece must then be moved back into the repaired gate to continue the Drahttrennläppens in such a way that first in the separating column, which has formed the wire to the cut interruption again exactly each wire section of the repaired wire gate is threaded and then the workpiece is continued to be delivered to the wire gate until the wire gate comes to rest at the location (separation gap bottom) of the cut interruption. This process is called repositioning.

In particular, the repositioning of the wire gate, with slight further delivery of the workpiece perpendicular to the wire gate to, includes threading each wire section into the respective separation gap, to which the wire section is exactly in line, so that in addition to the existing base voltage further low voltage in the Wire sections of the gate is constructed, which can slide the wire sections into the respective separating column and prevents re-slipping, and a slow continuous advancing the workpiece perpendicular to the wire gate, wherein the wire is continuously unidirectionally moved from the donor to the Nehmererspule and liquid cutting means is supplied to the wire until the wire portions have come into contact with the separation gap bottom. The continuous unidirectional longitudinal movement of the wire sections of the wire gate is required to carry the liquid cutting agent in the separation column, which acts as a sliding lubricant and supports a uniform, interruption and jerk-free further immersion of the workpiece in the wire gate until the wire gate finally on Location of cut interruption in the workpiece comes to rest.

The threading of a wire section into the respective separating gap can take place, for example, by blowing the edges of the partially separated disks at the level of the wire gate with compressed air. In this case, the partially separated slices are set in vibration in the direction of the workpiece axis, whereby the separating gaps are alternately farther and narrower and gradually submerge the wire sections located under slight tension in the feed direction of the workpiece into the separating gaps.

Structured wire is often very difficult to reposition after interruption of cut and removal from the release gaps and at the cost of preserving the formed release gaps. The inventors have found that when moving the wire gate made of structured wire through the separating gaps to the place of interruption cut in the workpiece again and again individual wire sections at certain cutting depths remain (jam or jam) and are deflected by the further zuzulierte workpiece more and more. Upon further infeed of the workpiece, the jammed wire section may rupture again or create a score in the surfaces of the slices obtained after complete severing of the workpiece by additional material removal as a result of being stuck at the relevant position in the separation gap with continued wire movement in the wire longitudinal direction and thus continued material removal.

Also, the friction between patterned wire and the walls of the separation column can not be reduced by dispensing with the wire longitudinal movement and instead continuing to inject pressurized air on the wire exit side of the workpiece along the line of contact of the workpiece and wire sections of the wire gate in the hope that one over the threading process with resting wire gate continued continued vibration of teilabgetrennten slices prevents jamming of the wire. Although the separation gaps between the partially separated slices become narrower and wider in rapid succession due to the vibration of the partially separated slices, which would promote further uniform, smooth immersion of the workpiece into the wire gate, blowing air into the separating slit also increases the volume from the wire longitudinal movement in the separation gap registered liquid cutting means, which should act to reduce friction, expelled again from the separation gap.

Even by varying the speeds (slowing or increasing) of the longitudinal wire movement and the delivery of the workpiece on the gate, a uniform sliding of the wire sections into the separating gaps can not be achieved with a structured wire.

The width of the separating gaps, which are created by the sawing of a wire gate into a workpiece, is determined both by the effective diameter of the saw wire and - when using a saw wire without firmly bound cutting grain - by the particle size distribution in the liquid cutting means ( 4 ).

4 (A) shows a wire 5 with structuring in that of him in the workpiece 1 formed separating gap 4 , The structure wire 5 comprises a straight wire (smooth wire), which is provided during manufacture by plastic deformation with protuberances and recesses alternately so that it has a Wavy structure in the wire longitudinal direction DL has.

A smooth wire 10 ( 4 (B) ) has the shape of a right circular cylinder of very high height. The diameter D of the smooth wire is the diameter of the base of this cylinder. The diameter is perpendicular to the lateral surface of this cylinder.

After attaching the protuberances and indentations, the structured wire formed from a smooth wire 5 no cylindrical shape. The structure wire 5 but runs within an envelope 9 , The envelope 9 is the cylinder with the smallest footprint, the structured wire 5 completely contains. In the special case, that the protuberances and indentations on average evenly in all wire transverse directions and not only, as in 4 (A) shown within the drawing plane of 4 (A) are formed, the base of the cylinder, which is the envelope 9 forms a circle. The diameter of the base of the cylinder forms the effective diameter DW of the structure wire 5 , In the case of a structure wire, the mean wire longitudinal direction DL denotes the direction of the axis of the cylinder, the lateral surface of which is the envelope 9 forms. The structure wire 5 is in the separation gap 4 surrounded by a film of a liquid cutting agent (slurry), so that the width WT of the separating gap 4 in the direction of the axis of the workpiece 1 greater than the effective diameter DW of the structure wire 5 , WT> DW.

4 (B) shows a wire 10 without structuring (smooth wire) in the workpiece in the workpiece 1 formed separating gap 4 , Because a smooth wire 10 have no protuberances and indentations in the wire transverse direction, wire diameter D and effective diameter DW are identical, D = DW. The smooth wire 10 has the shape of an elongated cylinder. Therefore, the envelope is 9 of the smooth-wire identical to the lateral surface of the (cylindrical) smooth-wire. The smooth wire is in the separation gap 4 also surrounded by a film of a liquid cutting agent (slurry), so that the width WT of the separating gap 4 in the direction of the axis of the workpiece 1 larger than the diameter D of the smooth wire 10 , WT> DW.

The so-called D90 value is decisive for the particle size distribution in the liquid cutting agent. D90 denotes the diameter of a distribution of grain sizes, for which 90% of all grains of the distribution have a smaller or the same maximum diameter. The D90 value thus corresponds to the diameter of the largest grain, which is found in a distribution in not insignificant number.

Experiments of the inventors have revealed that the width WT of the separation gaps created by a smooth wire with a diameter or a wire thickness D in the presence of a sawing suspension (loose abrasives) is given by equation (1), WT = D + 2 × D90 (1), can be described because the wire is surrounded with a cutting agent film in a thickness corresponding to the D90 value of the grain size distribution of the hard materials in the liquid cutting means.

Since, in a single, finite wire, the wire is continuously thinner as it passes through the workpiece from the beginning of the workpiece to the end of the workpiece, the thickness WT of the separating column also changes from the start of the workpiece to the end of the workpiece. This change is also represented by equation (1).

In a test with a smooth wire with the wire thickness D = 175 microns of the fresh wire, D = 163 microns of the old wire (after passing through a circular cylindrical workpiece made of silicon with a length of 375 mm and a diameter of 300 mm) and D90 = 22.3 microns results according to equation (1) for the rod beginning a width WT of the separation gap of WT = 175 microns + 2 × 22.3 microns = 219.6 microns and for the rod end width WT of the separation gap of WT = 163 microns + 2 × 22 , 3 μm = 207.6 μm. In the given example, these calculated values correspond to 0.05% with the actually measured separation gap widths WT. The model assumption WT = D + 2 × D90 thus gives the actual width of the separating gap for a smooth wire of a diameter D and a hard material with the largest grain size D90 very accurately.

Equation (1) can be used to calculate the width of a separation gap created by a structured wire ( 4a ) Not used. A structured wire has a core diameter D (corresponding to the wire thickness D of a smooth wire) and an effective diameter DW, which is due to the structure of the wire with its protuberances. The effective diameter of a structure wire is given by equation (2), DW = D + 2 × A (2), wherein the term 2 × A corresponds to a double amplitude (peak to peak) of the wave-shaped protuberances. A structured wire can not be considered to have a uniform thickness of the cutting medium film surrounding the wire.

Experiments of the inventors have revealed that the width WT of the separation gaps created by a patterned wire is given by Equation (3), WT = DW + k × D90 (3), can be calculated, where k is a dimensionless proportionality constant.

For the cutting of a circular cylindrical workpiece of silicon with a length of 375 mm and a diameter of 300 mm, for example, for a structure wire with a core diameter D = 175 microns, a double amplitude 2 × A = 23.5 microns and thus a working diameter DW of 198.5 μm (calculated using Equation (2)), the value for the dimensionless proportionality constant k is determined to be 1.5 using the equation (3).

The film of liquid cutting means surrounding the effective diameter DW of the structured wire is substantially thinner on average than the film which surrounds a smooth wire of the same diameter D in the separating gap. The structured wire "fills" the separating gap created by it better than a comparable smooth wire, since the structure wire takes the liquid cutting agent mainly in the "pockets" of its indentations ( 4a ), and thus the grain size of the cutting means only partially determines the resulting diameter of the separation gap.

The better supply of the separating gap with liquid cutting means when using a structured wire stems from the fact that the medium thinner, the effective diameter surrounding liquid cutting agent film constantly very effectively fed from these supplies.

Due to the beginning of the workpiece to the end of the work in a single, finite structured wire increasing wire wear in the wire gate, the width of the individual separation column in the workpiece changes to the effect that the width of the separation column decreases from the workpiece beginning to the end of the workpiece.

For the cutting of a circular cylindrical workpiece of silicon with a length of 375 mm and a diameter of 300 mm, for example, for a structure wire with a core diameter D = 175 microns, a double amplitude 2 × A = 23.5 microns and thus a working diameter DW of 198.5 .mu.m at the workpiece beginning a gap width WT of 219.5 microns and measured at the workpiece end a gap width WT of 207.5 microns. Thus, the structure wire at the workpiece end up to 60% less clearance in the separating gap than the comparable smooth wire. After cut interruption, repair and equipment of the wire gate with fresh wire, a structure wire therefore tends much more to jamming in the separating gap than a smooth wire of the same core diameter.

The wire sections in the sawing gate of a wire separating device experience through the additional frictional forces between the workpiece and saw wire during the separation process, a resilient deflection in the direction of the delivery of the workpiece to the wire gate and through it. Restoring forces counter to the feed direction generate the contact pressure of the wire to the separating gap, which is required so that by relative movement of the wire and workpiece, the material-removing effect can be deployed.

Due to the elastic deflection of the wire sections in the wire gate during the separation process, the tensile force and thus the wire tension increases in the wire longitudinal direction DL, with which the wire is wound in the wire gate around the wire guide rollers.

For a wire tension in the wire gate of 30 N and an elastic deflection of 8 mm results for a smooth wire of steel with a diameter D of 175 microns and a modulus of about 210 GPa on a free length of 510 mm, a wire transverse force of well 2 N and an increase in the wire longitudinal force by just under 2.5 N. The wire is thereby elastically stretched by about 0.05% in the longitudinal direction. The transverse contraction experienced by the smooth-wire leads to a decrease in its diameter of just over 40 nm (nanometers), which can be neglected.

When separating a workpiece with structure wire with 175 micron core and 199 micron effective diameter of the fresh wire, the inventors have observed slightly larger wire deflections, which should lead at least to the determined for the smooth wire Drahtlängsund- transverse forces. The somewhat larger wire deflections can be explained in a first approximation by the fact that the stiffness k _{E of} the smooth wire given by the modulus of elasticity and the wire cross-section, in the structure wire parallel another stiffness k _W resulting from stiffness of the wavy structure of the structured wire , so that the resulting overall stiffness k _strukt of the structured wire is less than that of a smooth wire of the same core diameter: 1 / k _strukt = 1 / k _e + 1 / k _W> 1 / k _e, so k _strukt <k _e. The stiffness k is also called the spring constant and is expressed in N / m.

Measurements of the effective diameter DW of the fresh structural wire at different wire-length stresses have each yielded an effective diameter of 200.6 μm at 25 N and 196.4 μm at 35 N. Thus, even with slight changes in the wire longitudinal force, the structured wire undergoes a clear change in its diameter, namely a reduction in diameter by a good 1 μm given an increase in the longitudinal force of the wire by 2.5 N. The effective diameter of the structural wire specified in the example is thus reduced by more than 50 times as much as the diameter of the smooth-wire element in the example given the same longitudinal stress under longitudinal tension of the wire.

This results in a compliance (elasticity) of the structure wire in the transverse direction with tension in the longitudinal direction of -0.42 microns / N. The compliance is the reciprocal of the stiffness or spring constant and is given in m / N.

However, because the liquid cutting agent has a certain viscosity, due to the high frictional forces in the movement of the structural wire through the viscous liquid cutting means and the cutting work done on the separating gap bottom, the forces actually acting on the structure wire and the resulting reductions in effective diameter DW are significantly greater than those determined by the above simple considerations.

In the structure wire arrive during the separation process only the protuberances of the zigzag deformations under pressure and relative movement in contact with the hard materials of the liquid cutting means and the walls of the separation column. The structure wire is therefore subject to a locally very non-uniform wear.

The compliance in the transverse direction with tension in the longitudinal direction of a structure wire and thus its resulting cross section, the effective diameter DW, increases strongly with the wear of the structured wire, since the rigidity imparting cross section by selective wear on the contact surfaces ("tips") of the protuberances strong decreases. This does not apply to the smooth wire, since it comes with all points of its surface equally under pressure and relative movement in contact with hard materials and Trennspaltwänden and thus subject to a very uniform wear.

The methods according to the invention are described below in detail individually and with reference to figures. The wire gate before the cut interruption is referred to in the context of this invention as the first wire gate. The wire gate used for repositioning is also referred to as a second wire gate in the context of this invention.

The start of cutting, ie the beginning of the cutting of a workpiece 1 in a plurality of slices to the interruption, takes place in the inventive method with a first structured wire 5 , This first structured wire 5 is passed through at least two wire guide rollers 6 spanned to a lying in a plane and consisting of parallel wire sections wire gate, the wire sections before contact with the workpiece have a base voltage or first wire tension, which prevents "sagging" of the individual wire sections. The first structured wire has an effective diameter below the base tension in the wire gate 9 ,

The methods according to the invention are preferably used when the cutting interruption has occurred at a separation gap depth of about two-thirds or more of the workpiece diameter, since repositioning of the second wire gate without formation of grooves in the separation gap walls has proven particularly difficult in this case.

First procedure

For a description of the first method (claim 1) shows 1 first, as a comparative example, the process of repositioning a patterned wire after cutting interruption and removing the wire 5 from the workpiece 1 in a previously structured wire 5 created separation gap 4 with a method not according to the invention.

1 (A) shows the workpiece 1 with an axis 2 , in the previously by delivery 23 of the rod on a gate made of sections of a structured wire 5 separation column 4 to a depth 3 (Trennspaltgrund) have been generated after cutting interruption and removal of the workpiece 1 from the wire gate. The workpiece 1 will be delivered to the wire gate so far ( 23 ) that it is in contact with the wire gate, but still no wire deflection 10 of the wire gate is generated. The structured wire 5 therefore has the large effective diameter 9 a structural wire not additionally loaded by wire deflection 5 on. This effective diameter 9 is much larger than the core diameter 8th of the textured wire 5 , At this point, the wire becomes 5 not yet moved in the wire longitudinal direction and the wire gate no liquid cutting means from the outlet nozzle for liquid cutting agent (Slurrydüse) 13 fed.

1 (B) shows the workpiece 1 , which continues on the gate of sections of the structured wire 5 has been delivered, so that the wire gate a deflection by one to two millimeters in the feed direction 23 and the individual wire sections of the gate in the separation column 4 through the same direction of rotation 17 the wire guide rollers 6 around their axes 7 unidirectional ( 15 ) in the wire longitudinal direction with the addition of liquid cutting agent 14 have been threaded, and with simultaneous further delivery of the workpiece 1 towards the wire gate, this towards the place 3 the cut interruption in the workpiece is moved. Since the Slurrydüse 13 in the direction of unidirectional wire longitudinal movement 15 seen in front of the workpiece 1 is located, the wire pulls 5 while liquid cutting agent 14 in the separation column 4 which acts as a lubricant or lubricant and supports a uniform wire movement through the separating gaps.

As the structure wire 5 First, the large effective diameter 9 out 1 (A) he jammed in 1 (B) in the separating gap 4 and will be on further delivery 23 of the workpiece 1 from the plane of the unloaded wire gate on the wire gate in the feed direction of the workpiece 1 deflected.

2 B) shows a structure wire 5 , which is already so strongly deflected in rod feed direction (high wire deflection 12 ), that by longitudinal expansion and transverse contraction its effective diameter 9 has become much smaller than it is in the wire not additionally stretched by wire deflection 5 of the unloaded gate in 1 (A) is.

After the effective diameter 9 of the textured wire 5 now by strong wire deflection 12 ( 1 (B) ) has become so thin that it is no longer in the separation gap 4 jammed, shows 1 (C) the re-released wire 5 after a jerky, relieving jump movement 18 towards the place 3 the cut interruption too. By the discharge 18 takes the structured wire 5 again the big effective diameter 9 of the unbent wire 5 , causing him again in the separation gap 4 jammed and initially no further towards the place 3 the cut interruption in the bar can slide.

By jamming the wire 5 is due to continued wire longitudinal movement 15 with the addition of liquid cutting agent 14 An additional material removal occurred after the complete separation of the workpiece 1 as a local rejuvenation 16 (Riefen) in the surface of the resulting discs expresses. 1 (C) shows the situation in view along the workpiece axis 2 (left part of the picture) and in view across the workpiece axis 2 (right part of picture).

By taking place during repositioning further delivery of the rod to the wire gate to repeat the interplay of jamming and jumping of the structured wire with a method not according to the invention as it moves through the separation gap 4 on the place of the cut interruption 3 to, and it arises contrary to the feed direction of the workpiece 1 an approximately regular sequence of more or less parallel grooves 16 with longitudinal extent in the wire running direction.

In the first method according to the invention (claim 1) is a new wire for the repositioning of the second wire gate structured wire 5 used at the same wire tension (wire longitudinal tension) in the wire gate the same effective diameter 9 like the first structured wire 5 (in each case based on the respective new state of the wire).

The first method according to the invention avoids the jamming of the (new) structured wire 5 during repositioning in the separating gap 4 in that the structured wire 5 preferably during the Repositioningiervorgangs, but at least when threading the wire sections of the second wire gate in the existing (generated by the first wire gate) separating gaps 4 , is applied with a higher second wire tension than the base tension or first wire tension before the cut interruption and its effective diameter DW thus in comparison with the effective diameter DW of the structured wire 5 is reduced before the cut interruption.

In a first embodiment of the first method, the increase in the second wire tension in the second wire gate is achieved by re-inserting the wire sections of the second wire gate into the existing separation gaps 4 structured wire 5 supplied with a higher wire tension from a wire supply than before the cut interruption. The wire sections of the first wire gate with which before the cut interruption, the separation column 4 in the workpiece 1 have been correspondingly exhibited a lower first wire tension.

First, after a cut interruption, the workpiece 1 reversed to the feed direction out of the first wire gate and away from it. If a wire tear is the cause of the cut interruption, which is a retraction of the workpiece 1 made from the first gate, all wire remains from the already created separation columns 4 and removed from the wire saw.

An essential feature of the first method according to the invention is that the repositioning of the structured wire 5 existing second wire gate with a higher second wire ground voltage than that first wire ground voltage in the first wire gate, with the separating gaps in the workpiece 1 were formed before the cut interruption.

Since at the cut interrupt preceding formation of the separation column 4 the wire at the workpiece end, on which the wire as it moves around the second length in the second direction a pilgrim step cycle 'the last separation gap 4 leaves because of wear one opposite to the opposite end of the workpiece, where the wire has previously entered as a fresh wire, reduced diameter, is at the former end of the workpiece separation gap 4 much narrower than the latter.

For complete assignment of all turns in the second wire gate with wire 5 after the repair becomes fresh (new) structured wire 5 pulled from the existing wire supply. After repair of the wire gate is thus inevitably always fresh wire 5 in the second wire gate.

This fresh wire 5 has an effective diameter under the second base voltage applied in the second wire gate 9 on, which is significantly larger than the mean effective diameter 9 the partially worn wire 5 , with the previously the separation column 4 have been formed. In the area of the particularly narrow separation gaps 4 at the old wire exit end of the workpiece 1 can the fresh wire 5 even an effective diameter 9 have, which is greater than the existing in this region of the workpiece separation gap width WT.

This is especially true when the separation column 4 before the cut interruption with a textured wire 5 and after repair of the wire gate fresh structured wire 5 the second wire gate forms, in addition to the wire wear, the decrease of the effective diameter 9 of the textured wire 5 resulting from the additional wire deflection (corresponding to an additional wire tension in the wire longitudinal direction DL) during the separation process. Thus, in comparison to the present in the repositioning with basic voltage in the repaired second wire gate fresh wire 5 hence the separation column 4 especially tight.

The basic voltage (rated voltage) is the tension of the wire in the wire longitudinal direction DL in the unloaded (not in engagement with the workpiece) wire gate and thus corresponds to the amount of wire longitudinal tension, with which the wire is supplied to the wire gate from the Frischdrahtvorrat during the separation process. In the case of a structured wire with a core diameter of, for example, 175 μm, the base stress is preferably between 20 and 45 N and particularly preferably 30 N.

This basic stress requires a resulting effective effective diameter 9 of the textured wire 5 , The stronger the structured wire 5 is biased, the more decreases its effective effective diameter 9 from.

If the structured wire 5 Chip work on the workpiece 1 performed, an additional force in the wire transverse direction acts on the wire 5 , which is proportional to the chip removal volume, ie the more volume of material per unit time is machined, the greater the force in the wire transverse direction. The material removal rate is determined by the speed of workpiece delivery. This wire transverse force leads to a wire deflection. With the increase in the wire lateral force (wire deflection) is always accompanied by an increase in the force in the wire longitudinal direction DL, so an additional voltage. This in addition to the basic voltage on the structured wire 5 In the wire longitudinal direction DL acting tension "stretches" the structure wire and thus makes it "slimmer", ie the resulting effective diameter 9 of the textured wire 5 is thus less than the effective diameter 9 of the textured wire 5 under ground voltage.

As the chip removal rate (table feed rate) increases, the wire deflection increases and the effective effective diameter increases 9 of the textured wire 5 from. With decreasing effective effective diameter 9 of the textured wire 5 also takes the width WT of the formed separation gap 4 from. A separating gap formed by rapid sawing 4 is with a structure wire 5 always narrower than one formed by slow sawing, and therefore rather narrower than the separating gap 4 which would correspond to an unloaded structured wire.

For a smooth wire 10 There is no such mechanism of wire loading decreasing wire diameter, since the decrease in effective diameter DW (corresponding to the diameter D) of the plain wire 10 when increasing the wire tension in the wire longitudinal direction DL is negligible. For a smooth wire 10 is a split gap created with fast cutting 4 as far as a dividing gap formed by slow cutting 4 , Only at extremely slow delivery of the workpiece on the wire gate and the gap produced by a smooth wire is something further, as each moving wire performs, for example, by vibration and some self-motion in the wire transverse direction perpendicular to the feed direction and therefore slowly expands the separation gap. In the case of stopping the workpiece feed with continued wire longitudinal movement, even a notch may be created in the walls of the separation gap.

According to the second wire gate is structured wire after repair of the wire gate from the fresh wire supply 5 of at least the length corresponding to the length of the wire contained in all turns of the wire in the wire gate. The value of increasing the wire tension in the second wire gate prior to repositioning, which provides jam-free smooth sliding of the wire wire 5 Safely guaranteed during repositioning depends on a structured wire 5 both from the respective wire core diameter 8th as well as the design of the structuring (eg wavelength and amplitude of the zigzag-shaped protuberances and indentations, choice of the transversal planes in which they run).

The increase in the wire tension in the second wire gate can not be arbitrary, since each wire has a maximum by the material and by the material thickness (wire diameter) determined maximum ultimate tensile strength (or tensile strength), ie a voltage at the wire breaks.

For example, if a 0.9% carbon steel tempered steel wire having a core diameter of 175 μm has a maximum breaking stress of 85 N, a wire of the same material having a core diameter of 140 μm has a breaking stress of 58 N.

In the first method according to the invention, the wire tension in the second wire gate is at least at the beginning of repositioning, ie before the threading of the wire sections of the wire gate into the existing separation gaps 4 , chosen so that the wire longitudinal tension (wire tension, basic tension) in the wire gate is greater than the wire longitudinal tension in the first wire gate before the cut interruption.

For the first method of the invention, increasing the wire tension at least at the beginning of repositioning to up to 75% of the breaking stress is preferred over the patterned wire 5 evenly through a separating gap previously formed by him 4 to move. Particularly preferred is an increase in the wire tension at least at the beginning of the repositioning to up to 60% of the breaking stress.

Examples of the consequent reductions in the effective diameter 11 are mentioned in the description of the first embodiment of the first method. The base voltage refers to the amount of wire longitudinal tension with which the wire is fed during the separation process, the wire gate from the fresh wire supply.

Since during Repositionierens, in contrast to the separation process, no Spankräfte (force in the wire transverse direction) act on the wire sections of the second wire gate and the wire 5 There is no risk of breakage of the wire due to the increased wire tension in comparison to the cutting process 5 ,

The implementation of the first method according to the invention can be carried out with any wire-cutting apparatus according to the prior art.

After feeding new (fresh or unworn) structured wire 5 with an increased voltage to the second wire gate compared to before the cut interruption, in the first method, the second wire gate in the direction of the delivery of the workpiece 1 on the second wire gate to coincide with the separating gaps 4 in the workpiece 1 brought so that to each separation gap 4 exactly one wire section of the second wire gate is in cover. Subsequently, the workpiece becomes 1 further delivered until the workpiece 1 touches the second wire gate and the wire sections are deflected by about 1 to 2 mm in the feed direction. The further increase in the wire tension associated with this small wire deflection is small compared with the increased wire tension carried out according to the first method according to the invention and therefore does not increase the risk of wire breakage.

Do not immerse the wire sections automatically in the separation column 4 For example, by blowing the edges of the partially separated disks at the level of the wire gate with compressed air, the partially separated disks vibrate in the direction of the workpiece axis 2 be offset, causing the separation column 4 alternately further and narrower and under slight tension in the feed direction of the workpiece 1 gradually located wire sections in the separation column 4 plunge.

Once all the wire sections in the separation column 4 immersed, the second wire gate is liquid cutting means 14 over the nozzles 13 supplied and by preferably unidirectional rotation 21 the wire guide rollers 6 the wire 5 moved at a first speed in the wire longitudinal direction, while at the same time the workpiece 1 continue with a first speed continuously on the wire gate or the wire gate on the workpiece 1 is delivered.

The preferred first speed with which the workpiece 1 during Repositionierens on the wire gate or the wire gate on the workpiece 1 is delivered, is 25 to 500 mm / min. The preferred first speed at which the wire is moved in the wire longitudinal direction during repositioning is 0.25 to 5 m / s.

Both the feed rate of the workpiece to the wire gate and the wire speed in the longitudinal direction during repositioning depending on the position of the wire gate in the workpiece are preferred 1 changed from a first speed to a second speed, wherein the position of the wire gate in the workpiece 1 during the change of the wire speed in the wire longitudinal direction preferably between 0% and 33% of the diameter of the workpiece 1 lies. 0% corresponds to the position of the wire section at the beginning of the separation gap.

In addition, the first feed rate of the workpiece to the wire gate or the wire gate on the workpiece and the first wire speed, so the unidirectional movement of the wire in the wire longitudinal direction, the same or different. Also, the second feed speed and the second wire speed may be the same or different.

Before the structure wire 5 receives additional load by friction and chip work in the continuation of the separation process is preferably already begun during repositioning, the existing wire in the second wire length 5 with increased tension against wire 5 replace with reduced voltage. This will until reaching the location of the cut interruption 3 the wire 5 not overloaded in the second wire gate and avoided the risk of wire breakage.

Different wire tensions in a wire gate, that of at least two wire guide rollers 6 Although is spanned, are partially due to wire slip due to the sliding lubricant effect of the liquid cutting agent 14 balanced, this compensation of the wire longitudinal stresses but affects only a few adjacent turns in the wire gate.

The reduced voltage in the second wire gate set at the end of the repositioning operation is preferably selected such that the reduced wire tension corresponds to the wire tension with the separation gap before the cut interruption 4 were formed and with after reaching the place of cut interruption 3 the workpiece 1 until complete separation into a plurality of uniform slices of the separation process is to be terminated.

Preferably, the reduction of the wire tension in the second wire gate in the first method according to the invention takes place when the workpiece 1 when repositioning by one third (33%) of its diameter is immersed in the wire gate.

Also preferably, the reduction of the wire tension in the second wire gate in the first method according to the invention, regardless of the position of the cut interruption in the workpiece 1 when the second wire gate when re-entering the separation column 4 immersed by a third (33%) based on the separation gap depth.

After reinserting the wire sections of the second wire gate into the separation gaps 4 of the workpiece 1 Preferably, the reduction of the wire tension in the second wire gate during repositioning is performed simultaneously with the selection of a second speed of the unidirectional movement of the wire in the wire longitudinal direction and the workpiece 1 and the choice of a second speed of further delivery of the workpiece 1 to the wire gate, while the wire sections at cutting depths of greater than 0 to 33% based on the diameter of the workpiece 1 or if the wire sections are at cutting depths of greater than 0 to 33% based on the separation gap depth.

More preferably, the second speed of the unidirectional movement of the wire in the wire longitudinal direction is selected to be greater than the first speed of the unidirectional movement of the wire in the wire longitudinal direction.

Particularly preferably, the second speed of the unidirectional movement of the wire in the wire longitudinal direction is selected so high that until reaching the location of the interruption cut the wire gate wire of a length is supplied, which corresponds to the length of the wire contained in the wire gate. However, at least this second speed is 50% higher than the first speed of the unidirectional movement of the wire in the wire longitudinal direction.

Also particularly preferred is the second speed of the further delivery of the workpiece 1 on the wire gate chosen to be smaller than the first speed of further delivery of the workpiece 1 towards the wire gate.

Particularly preferred is the second speed of the further delivery of the workpiece 1 chosen so low on the wire gate, that until reaching the location of the interruption cut the wire gate wire of a length is supplied, which corresponds to the length of the wire contained in the wire gate. However, at least this second speed is compared to the first speed of the further delivery of the workpiece 1 halved on the wire gate.

The following is an example of the first embodiment of the first method:
A straight cylindrical silicon rod with a diameter of 300 mm was parted by means of a structure wire with 175 μm core diameter and 199.5 μm effective diameter of the fresh wire under 30 N wire longitudinal stress in the pilgrim step method. The separation process was at 225 mm cutting depth, corresponding to 75% The total depth of cut of 300 mm, interrupted and the rod under slow unidirectional wire longitudinal movement and supply of slurry again moved out of the wire gate.

The wire gate was then first fresh wire according to the first embodiment of the first method 5 supplied from the wire supply (donor coil) under a wire longitudinal tension of 50 N, corresponding to a voltage of almost 60% of the breaking tension of the wire 5 of 85 N. Then, the wire portions of the wire gate in the feed direction of the rod toward the wire gate became coincident with the resulting separation gaps 4 and the wire gate brought by contact of the rod in contact with the rod. Further infeed, the wire gate was deflected by about 2 mm and, by blowing the separation gaps along the line of contact of the rod with the wire gate, the wires engaged the separation gaps 4 brought.

Subsequently, the wire gate according to the first embodiment of the first method for resuming the separation lapping after interruption with a unidirectional wire longitudinal movement with the supply of slurry through the separation gaps 4 guided (repositioning), wherein the wire longitudinal tension of the wire gate from the wire supply (donor coil) supplied wire was still 50 N. After the wire gate had reached a cutting depth of 100 mm, corresponding to one third (33%) of the total cutting depth of 300 mm, the longitudinal tension of the wire fed from the supply was reduced to 30 N, the speed of the wire longitudinal movement increased and the speed of the bar delivery reduced.

When reaching the Trennspaltgrunds 3 in 225 mm depth of cut unidirectional wire movement, rod delivery and slurry feed were stopped and the separation process continued with the same control variables (including wire speed, wire tension, feed rate, slurry feed to the wire gate) as before the cut interruption until complete separation of the rod in the pilgrim step method.

Since the gate during repositioning fresh wire 5 is fed, which was not subject to wear and thus has a greater tensile strength than the teilverschlissene wire 5 , which is always in the wire gate during the Trennläppens on average, it is preferred if only a part of the wire gate with wire 5 the reduced voltage of for example 30 N is filled and a part still with wire 5 the increased voltage of, for example, 50 N when the wire 5 in the continued Trennläppen the full load by material removal and friction absorbs. Since, as already explained, the risk of jamming of the wire 5 during repositioning into the separation gaps created before the wire tear 4 at the Altdraht exit end of the workpiece 1 is greatest, supports a preferred when reaching the place 3 the cut interruption only partially with wire 5 in basic tension filled wire gate a uniform, jam-free sliding of the wire 5 There most, where it is most needed, because then the remaining wire in the wire portion with higher voltage than the base voltage is also present in the vicinity of the old-wire outlet end.

In the following, a second embodiment of the first method will be described, in which the increase of the wire tension of the wire present in the wire gate 5 before threading the wire sections into the existing separation gaps 4 by means of a pre-stretching, for example by a pressure roller 19 , is made.

2 shows the second embodiment of the first method according to the invention schematically. In the second embodiment, the increase of the longitudinal tension of the structured wire essential to the invention for the first method becomes 5 at least at the beginning of Repositioningierens, so before threading the wire sections of the wire gate in the existing separation column 4 , after cutting interruption thereby causing at least one rotatable about its axis 20 mounted pinch roller 19 by means of a delivery movement 30 is pressed against the wire gate. This will change the length of each turn of the wire 5 around the wire guide rollers 6 enlarged and the structured wire 5 consequently stretched elastically in the wire longitudinal direction. This stretching leads to a reduction in the effective diameter 11 of the textured wire 5 This makes it easy to reposition through the separation column 4 can slide.

After interruption of wire-cutting lapping with structured wire 5 a first tension at a depth of cut 3 becomes the workpiece 1 pulled out of the wire gate. If the reason for the cut interruption was a wire break, the wire gate is repaired. Subsequently, the pinch roller 19 whose axis of rotation 20 parallel to the axes 7 the wire guide rollers 6 and the axis 2 of the workpiece 1 is arranged and which extends over the entire length of the wire gate, by means of a feed movement 30 so pressed against the wire gate that every wire turn a deflection 12 in wire transverse direction experiences (wire deflection 12 ) and the length of each winding of the wire 5 around the wire guide rollers 6 increased. This will make every turn of the wire 5 and thus each section of the wire gate is stretched elastically in the wire longitudinal direction, and it is over the entire length of the wire 5 to a reduction of the effective diameter 11 ,

The repositioning of the by the pressure roller 19 additionally tensioned wire gate takes place as already described above.

Once the wire gate the place 3 the cut interruption has reached, the pinch roller 19 opposite to the delivery movement 30 moved and brought out of engagement with the wire gate and the separation process by wire longitudinal movement, further delivery of the workpiece 1 on the wire gate and adding liquid cutting agent 14 continued until the workpiece is completely separated into a plurality of uniform slices.

In addition to the use of a pressure roller 19 is also the use of several pinch rollers 19 for the initial increase of the wire longitudinal stress in the wire gate preferred.

Be several pinch rollers 19 Preferably, these are each one between each pair of opposing wire guide rollers 6 positioned. This distributes the increased wire tension more uniformly over the entire circumference of all wire turns. Even when using only one pinch roller 19 However, in the course of the continuous longitudinal movement of the wire, the wire tension is distributed very evenly over the entire turn, since the wire 5 on the wire guide rollers 6 due to the liquid cutting agent 14 is subject to a slip.

The pressure roller is preferred 19 already brought back out of engagement with the wire gate when the workpiece 1 by one-third (33%) or more of the total depth of cut required to completely separate slices was reintroduced into the wire gate.

The velocities of the wire longitudinal movement and the delivery of the rod can during the Repositionierens over to the place 3 the cutting interruption remaining depth of cut from one first to one second speed to be changed again.

So that the structured wire 5 not material removing in the pressure roller 19 incorporated, it is preferred, the lateral surface of the pressure roller 19 with a wear-resistant material 28 to coat, for example, a polyurethane.

In a third embodiment of the first method, the increase in the wire tension of the wire present in the wire gate 5 before threading the wire sections into the existing separation gaps 4 by increasing the pitch of the axes 7 at least two adjacent wire guide rollers 6 (compared to the distance axes 7 before the cut interruption) realized.

Second procedure

In the following, the second method (claim 9) based on 3 described.

3 (A) shows the initial situation after cutting interruption at cutting depth 3 and removing the partially severed workpiece 1 from the first wire gate. The partially severed workpiece 1 is made of textured wire 5 existing, by at least two wire guide rollers 6 spanned second wire gate in delivery direction 23 delivered to the wire gate; This is followed by bringing the existing separation gaps into line 4 and the wire sections of the second wire gate after feeding the workpiece 1 until the touch of the second wire gate. The structured wire 5 is under basic tension, but is not bent and has an effective diameter 9 ,

Characteristic of the second method according to the invention is that the wire sections in the freshly structured wire 5 provided second wire gate having a base voltage. The basic voltage of the second wire gate may be smaller, equal to or greater than the base voltage in the first wire gate. For a structured wire with a core diameter of, for example, 175 μm, the base stress is preferably 30 N.

According to the second method of the invention (claim 9) now at least two additional support rollers 25 left and right of the workpiece 1 arranged so that the workpiece 1 when fully passing through the wire gate, the support rollers 25 can happen. For more than two wire guide rollers 6 are the at least two support rollers 25 between the workpiece 1 and each to the workpiece 1 adjacent wire guide rollers ( 3 ).

The envelope 29 limits the space that the workpiece 1 sweeps over the gate passage. The support rollers 25 have a circular cylindrical shape with two side surfaces and a lateral surface, are freely rotatable about the axes 26 are stored and are, based on the workpiece 1 , below the second wire gate of the structured wire 5 and laterally of the at least two wire guide rollers 6 , which span the second wire gate, arranged. The axes 26 the support rollers 25 run parallel to the axes 7 the wire guide rollers 6 and the axis 2 of the workpiece 1 , and every supporting role 25 extends over all wire sections of the wire gate.

The support rollers are preferred 25 with a height adjustment 31 provided with the distance the support rollers 25 can be adjusted to the bottom of the wire gate.

The attached below the wire gate support rollers 25 may be prior to inserting the wire sections of the second wire gate in the existing separation column 4 a distance to the non-deflected wire gate (wire sections in basic voltage), which is dimensioned such that when repositioning the wire gate in the separating gaps of the workpiece 1 occurring low deflection 12 the wire sections cause all wire sections in contact with the support rollers 25 reach. In this embodiment, the lateral surfaces of the support rollers 25 not in contact with the under wire tension wire sections in the wire gate.

The support rollers 25 may also be prior to inserting the wire sections of the second wire gate into the existing separation gaps 4 be positioned below the wire gate so that they just touch all the wire sections of the unbent wire gate (wire sections in basic voltage) just the outer surface, without the wire sections against the direction of the delivery of the workpiece 1 deflect.

Preferably, the distance between the lateral surface of the support roller 25 and the under wire tension wire sections of the wire gate between 0 mm and 2 mm are adjusted.

Finally, the support rollers 25 prior to inserting the wire sections of the second wire gate into the existing separation gaps 4 Also be arranged below the wire gate, that they the wire gate by a few millimeters counter to the direction of the delivery of the workpiece 1 bend on the wire gate.

Preferably, the wire deflection is 12 against the direction of the delivery of the workpiece 1 mm to 10 mm.

This latter embodiment is particularly preferred because in addition to the deflection of the wire sections by supporting limiting effect of the support rollers 25 the longitudinal stress of the wire sections is increased by longitudinal expansion beyond the basic stress and the effective diameter 9 As a result, the wire sections are additionally reduced as a result of simultaneous transverse contraction, which additionally supports a uniform, jam-free sliding of the wire sections through the separating gaps during repositioning.

The support rollers 25 have in the second method according to the invention on a rigidity, which is a bending of the support rollers 25 safely prevented over the entire gate length in Werkstückachsrichtung under the load of all wire sections.

The movement of the wire 5 in wire longitudinal direction DL displaces the support rollers 25 by touching with the wire 5 during repositioning into a rotation 27 , So that the wire 5 not in the support rollers 25 incorporated, are the support rollers 25 preferably with a coating 28 made of a wear-resistant material, such as a polyurethane.

To resume cutting after interruption and removal of the workpiece 1 from the first wire gate are after mounting the support rollers 25 those in the workpiece 1 formed separating column again in the direction of the delivery of the workpiece 1 brought to the second wire gate to coincide with the wire portions of the second wire gate, the workpiece 1 delivered to the second wire gate until it bends the second wire gate one to two millimeters in the feed direction.

The wire sections are formed, for example, by blowing the contact line of the workpiece 1 and the wire sections in engagement with the separation gaps 4 brought. By rotation 17 the wire guide rollers 6 with the same peripheral speed around their axes 7 becomes the structured wire 5 unidirectionally moved in the wire longitudinal direction and under supply of liquid cutting agent 14 and with simultaneous delivery of the workpiece 1 moved to the second wire gate and through this until the second wire gate the place 3 cutting interruption in the workpiece 1 reached.

3 (B) shows the situation while moving the of the support rollers 25 supported second wire gate through the separation column 4 in the workpiece 1 , Because the structured wire 5 at the wire gate in basic tension not or only just just touching support rollers 25 has, has the wire 5 an effective diameter 9 which is larger than the effective diameter 9 that the wire had during the separation process. During the separation process, the wire experiences 5 due to the cutting pressure, a deflection 12 and thus a transverse contraction, ie a reduction of the effective diameter 9 , upon delivery 23 of the workpiece 1 in the separating gap 4 Consequently, the wire sections will first jam in the separating gaps and thus in the feed direction 23 be deflected and bent.

The points of contact of the wire 5 with the support rollers 25 shorten the free length of the wire 5 on which he can be bent further. The spring constant of the wire 5 relative to lateral deflection increases approximately inversely proportional to the ratio of the shortening of free wire length between the wire guide rollers spanning the second wire gate 6 and between the support rollers 25 ,

Within the workpiece 1 works on the wire 5 however, approximately an equally distributed along the engagement length force on the wire, resulting within the workpiece 1 a parabolic profile of the wire deflection results. The arc length of a parabola (evenly distributed wire load) is greater than that of two sections with an angle (center point load of the wire) of the same deflection at the respective vertex. The wire 5 Thus, in fact, it is stretched more in the longitudinal direction, ie behaves stiffer, and the deflection within the workpiece 1 is therefore less than that at a point load with equally distributed wire load.

Example: For 0.2 mm distance of the support rollers 25 to the wire gate results in a change .DELTA.l the wire length l = 510 mm between the wire guide rollers 6 by Δl ≈ 1.3 μm until the wire sections form the support rollers 25 touch. This increases the voltage F _|| in the wire longitudinal direction by ΔF _|| ≈ 0.013 N, and on the deflected wire sections acts a restoring force F _⊥ counter to the workpiece _delivery direction of F _⊥ ≈ 0.05 N. A wire _{transverse force} of F _⊥ = 2.5 N, the free length of the wire sections of 510 mm to a wire deflection in Feed direction of 8 mm would result when using the support rollers 25 with a reduced to 333 mm free length of the wire sections only a small wire deflection 24 in the feed direction of 5 mm. For accurate calculation with parabolic wire deflection within the workpiece 1 results in a maximum deflection in the feed direction of less than 4 mm.

The deflection 12 is in the example given by support rollers 25 So compared to a wire saw without support rollers 25 more than halved. If during movement of the wire sections of the wire gate through the separation gaps 4 during repositioning, a wire section in the separation gap 4 "Stuck", then halved by half the free wire length and the way to halve the workpiece 1 continues on the wire gate is delivered until the restoring force due to the deflection 12 of the stuck wire section has become so large that the wire 5 is released again and in the separation gap 4 "Jumps". This also halves the dwell time of the stuck wire 5 at one point in the separating gap 4 and thus the depth of the notch or groove created by the continuous wire longitudinal movement and slurry feed. The shortening of the free wire length by the support roller 25 thus counteracts the formation of deeper and harmful grooves or notches according to the invention.

Once the second wire gate the place 3 has reached the cut interruption, are wire longitudinal movement, workpiece delivery and supply of liquid cutting agent 14 stopped and the support rollers 25 preferably removed from the device before continuing the separation process.

Depending on the details of the construction of the wire saw used and the depth of cut at which the cutting interruption occurred, removal of the support rollers is 25 when lowered into the wire gate workpiece 1 may not be possible because now the workpiece 1 easy access to the support rollers 25 partially locked. In this case, the support rollers 25 remain in the wire saw until the end of the separation process. The separation process will now take until complete removal of a plurality of slices from the workpiece 1 continued.

When the support rollers 25 can not be removed from the wire saw after completion of the repositioning, is the distance of the support rollers at the end of Repositioningierens 25 to the wire gate by means of the height adjustment 31 preferably enlarged so that the support rollers 25 no longer come into contact with the second wire gate during the continuous separation process bent second wire gate. Otherwise they would because of the then very high speed of the wire 5 in the wire longitudinal direction (for example 10 m / s) rotate very fast due to their small diameter ( 27 ), which is detrimental to the bearing of the rotary axes 26 and would also lead to premature incorporation of the wire sections in the coating of the support rollers, making them prematurely unusable.

Third procedure

The third method according to the invention (claim 13) is characterized in that the first structured wire 5 started separation process after a cut interruption with a second wire is terminated until complete separation of the discs, wherein the effective diameter 9 of the second wire is smaller than the effective diameter 9 of the first wire 5 , each related to the same basic voltage.

The second wire is preferably a smooth wire 10 , With a smooth wire 10 are effective diameters 9 and diameter D are identical. In this embodiment, the diameter D of the smooth second wire becomes 10 smaller than the effective diameter 9 of the structured first wire 5 selected.

Also preferably, the second wire is a structure wire 5 , In a structured wire (structure wire), the effective diameter DW is greater than the wire diameter D. In this embodiment the effective diameter 9 of the structured second wire 5 smaller than the effective diameter 9 of the structured first wire 5 , in each case based on the same basic voltage acting in the wire longitudinal direction DL, selected.

The third method according to the invention (claim 13) for repositioning the second wire gate after a cut is described in detail below.

The start of cutting, ie the cutting of a workpiece 1 into a plurality of disks, as in the other methods according to the invention with a through at least two wire guide rollers 6 spanned with a first wire tension, from parallel wire sections of a structured wire 5 with an effective diameter 9 existing first wire gate.

After cutting interruption, the workpiece becomes 1 moved out of the first wire gate and the first structured wire 5 , with which the separation process was carried out until the cutting interruption, is against the second structured wire 5 or smooth wire 10 exchanged, with the second wire 5 respectively. 10 a smaller effective diameter 9 has as the first structured wire 5 , in each case based on the same basic voltage acting in the wire longitudinal direction DL.

The wire exchange can take place, for example, in that the second structured wire 5 or smooth wire 10 to the first structured wire 5 knotted and by rotation 17 the wire guide rollers 6 is pulled from the wire supply over the entire wire gate and to the Nehmererspule.

The wire voltage in the second wire gate preferably corresponds to the wire base voltage (wire voltage, wire longitudinal voltage) in the first wire gate. Also preferred is a higher or lower wire tension in the second wire gate compared to the wire tension in the first wire gate.

Subsequently, the wire portions of the second wire gate are made of the second wire 5 respectively. 10 in the feed direction of the workpiece 1 in coincidence with the already created separating gaps 4 brought and into the respective separation column 4 of the workpiece 1 threaded.

The threading of the second structured wire 5 or smooth wire 10 formed wire sections in the separation column 4 takes place under wire longitudinal movement of the second wire 5 respectively. 10 through the same direction of rotation 17 the wire guide rollers 6 at the same peripheral speeds, adding liquid cutting agent 14 and with continued delivery of the workpiece 1 towards the second wire gate. At the same time the wire sections are finally up to the place 3 the cut interruption by the separating column 4 guided.

Because the second structured wire 5 or smooth wire 10 a, based on the same in the wire longitudinal direction DL acting base tension, lower effective diameter 9 as the first structured wire 5 who has the separation column 4 before the cut interruption has formed, jammed the second wire 5 respectively. 10 while moving through the separation column 4 to the place 3 the cut interruption not ( 3b ).

The separation process is then completed with the second structured wire 5 or smooth wire 10 until complete separation of a plurality of slices from the workpiece 1 continued. Preferably, the separation process with the same settings of the separation process (feed rate, type and speed of longitudinal wire movement unidirectional or bidirectional, for example after the pilgrim step method, etc.) ended, with which the separation process was performed until the cut interruption.

Also preferably, other settings for the resumption of the separation process are selected, for example those that the reduced effective diameter 9 of the second wire 5 respectively. 10 or whose type of wire (smooth or structured wire) take specific account.

Is the second wire 5 respectively. 10 for example due to its lower effective diameter 9 susceptible to cracking, so sawn more slowly or a larger wire length can be used. With a larger wire length, the wear volume of wire corresponding to the machined workpiece volume is distributed 5 respectively. 10 on a larger wire length. The thickness decrease of the wire 5 respectively. 10 due to wear is thus less than the separation with short wire length. The worn wire 5 respectively. 10 leaves the workpiece with a remaining greater residual thickness than in the comparison case of the separation with short wire length. An increased residual thickness increases the tear strength of the worn wire 5 respectively. 10 and thus acts on wire tears when Trennläppen with thin (fresh) wire.

In one embodiment of the third method according to the invention, a wire saw with a diameter of 195 mm and a spacing of 510 mm is used for the wire guide rollers spanning the wire gate 6 used and a 300 mm silicon rod with a structured first wire 5 Below 30 N wire tension (base tension), a core diameter of 175 microns and a working diameter of the fresh wire of 198.5 microns at 30 N in the pilgrim step process to a depth of 225 mm cut. The cutting depth for the interruption is chosen to be 225 mm (75% of the total depth of cut), because repositioning at cut interruptions from 50% of the total depth of cut is susceptible to non-inventive methods and from 75% even more susceptible to wire breaks or the formation of grooves in the surface Slices obtained after complete separation and thus represents a good test case for the effectiveness of the third method according to the invention.

The second wire is a smooth wire 10 chosen with 175 μm core diameter. Since a smooth-wire core and effective diameter are identical, the second wire is identical 10 thinner than the first wire 5 with an effective diameter 9 of 198.5 μm.

To change the wire after the cut interruption is the structured first wire 5 - in the direction of the net movement of the wire 5 seen - severed before the first wire gate, the smooth second wire 10 to the wire gate end of the first wire 5 knotted, the encoder coil with structured first wire 5 in the wire saw against the donor coil with a smooth second wire 10 replaced and the node by the same direction rotation 17 the wire guide rollers 6 with the same peripheral speed as long as the second wire gate moves to the Nehmererspule until the first wire 5 is buried under some wire windings on the Nehmererspule.

Subsequently, the wire sections of the second wire gate in the feed direction of the silicon rod to the wire gate to coincide with the separating gaps 4 placed in the rod, the rod is delivered to the wire gate until the second wire gate is deflected by one to two millimeters in the feed direction, and by blowing the contact line of rod and wire sections, the wire sections are engaged with the separation gaps 4 brought.

By the same direction rotation 17 the wire guide rollers 6 at the same peripheral speed becomes the second wire 10 unidirectional from the donor to slave coil with simultaneous delivery of the rod further to the second wire gate and addition of liquid cutting means 14 moved on until the wire gate is in place 3 the cut interruption has arrived.

The separation process is then pilgrim-paced with the smooth second wire 10 and terminated until complete separation of a plurality of uniform slices from the rod.

For cutting up to cutting interruption with the structured first wire 5 At 10 m / s, the wire is moved 320 m forward and backward by 220 m for each pilgrim step. The average table delivery speed of 0.47 mm / min is chosen so that a complete, uninterrupted separation process through the entire cross-section of the rod with the structured first wire 5 10.6 hours, winding a total wire length of 72 km with an effective speed of net wire movement of 1.85 m / s from the donor to slave coil.

For post-pilgrim separation after repositioning, the smooth second wire is used 10 also traveling at 10 m / s for each pilgrim step by 320 m, but moving back 247 m, with the tabletop delivery speed of 0.39 mm / min being chosen so that a complete, uninterrupted separation process through the entire cross section of the bar with the smooth second wire 10 (see. 4 (B) ) Would have taken 12.9 hours and thereby a total wire length of 60 km from the donor to Nehmererspule would have been rewound. Because a smooth wire 10 with a diameter D, the liquid cutting agent 14 less well transported in the separating gap than a structure wire 5 identical core diameter D but a larger effective diameter 9 , must finish the separation process with the smooth wire 10 at slower delivery of the workpiece 1 on the wire gate to (less Zeitspanvolumen) are performed as the separation process with the structure wire 5 (higher time-wasting volume).

Locally 3 the cut interruption results from the fact that the separation process with a structure wire 5 or a smooth wire 10 with a smaller effective diameter 9 as the first wire 5 , which was used until the cut interruption, is completed, a sudden increase in the thickness of the slices obtained after complete slicing.

In the specified embodiment, a structure wire used until the cut interruption 5 with an effective diameter 9 the fresh wire of 198.5 microns and a plain wire used from the cut interruption 10 with a diameter D of the fresh wire 10 of 175 microns is the thickness of the slices to the interruption of cut average over the entire rod 899.0 microns and from the interruption of cut average over the entire rod 907.5 microns.

Thus, at the site of the cut interruption, a step in the thickness profile of the resulting slices of an average of 8.5 μm in height arises. However, this step occurs in each case half on the front and back of the discs obtained, thus affecting only the thickness of the discs, but not their shape and therefore can be effectively and completely removed by the subsequent steps of the processing of the disc.

Claims (18)

Method for resuming an incomplete parting of a workpiece 1 in a variety of slices with a textured wire 5 passing through at least two wire guide rollers 6 to a first wire gate comprising a plurality of parallel wire sections having a first wire tension and having a first effective diameter 9 is clamped, comprising a) removing the first wire gate from the in the workpiece 1 separating gaps formed by the first wire gate 4b b) the reintroduction of one by at least two wire guide rollers 6 with a second wire tension of a structured wire 5 spanned wire gate in the separating column 4 , and the patterned wires 5 in the first and in the second wire gate in the new state at the same wire tension the same effective diameter 9 have, characterized in that prior to the insertion of the wire sections of the second wire gate in the existing separation gaps 4 the second wire voltage is greater than the first wire voltage. A method according to claim 1, characterized in that the second wire tension in the second wire gate by the supply of the structured wire 5 is achieved with a higher wire tension than the first wire gate. A method according to claim 1, characterized in that the second wire tension in the second wire gate by at least one rotatable about its axis 20 mounted pinch roller 19 that by means of a delivery movement 30 is pressed against the wire gate is reached. A method according to claim 1, characterized in that the second wire tension in the second wire gate is increased by increasing the pitch of the axes 7 at least two adjacent wire guide rollers 6 is effected to each other. Method according to one of claims 1 to 4, characterized in that the second wire voltage before inserting the wire sections of the second wire gate in the existing separation gaps 4 up to 75% of the breaking stress of the wire 5 is. Method according to one of claims 1 to 5, characterized in that the second wire tension after the insertion of the wire sections of the second wire gate in the existing separation gaps 4 and before resuming cutting a workpiece 1 is reduced again in a variety of slices. A method according to claim 6, characterized in that the reduction of the second wire tension in the second wire gate begins when the second wire gate upon insertion into the separation gaps 4 of the workpiece 1 by one third of the total depth of cut into the depth of the separation column 4 is immersed. Method according to one of claims 6 or 7, characterized in that the second wire tension in the second wire gate is reduced to the first wire tension in the first wire gate before the cut interruption. Method for resuming an incomplete parting of a workpiece 1 in a variety of slices with a textured wire 5 passing through at least two wire guide rollers 6 to a first wire gate comprising a plurality of parallel wire sections having a first wire tension and having a first effective diameter 9 is clamped, comprising a) removing the first wire gate from the in the workpiece 1 separating gaps formed by the first wire gate 4b b) the reintroduction of one by at least two wire guide rollers 6 with a second wire tension of a structured wire 5 spanned wire gate in the separating column 4 , and the structured wires 5 in the first and in the second wire gate in new condition at the same wire tension the same effective diameter 9 have, characterized in that in each case between the workpiece 1 and the two wire guide rollers adjacent to the workpiece 6 in each case at least one support roller 25 is arranged so that the at least one support roller 25 a bending 12 limits the wire sections in the second wire gate in the direction of the workpiece delivery. A method according to claim 9, characterized in that the support rollers 25 at the second wire tension prior to insertion of the wire sections of the second wire gate into the existing separation gaps 4 have no contact with the wire sections of the second wire gate. A method according to claim 9, characterized in that the support rollers 25 before inserting the wire sections of the second wire gate into the existing separation column 4 at the second wire tension in contact with the wire sections of the second wire gate, without causing a deflection of the wire gate. A method according to claim 9, characterized in that the support rollers 25 prior to inserting the wire sections of the second wire gate into the existing separation gaps 4 at the second wire tension are in contact with the wire sections of the second wire gate, thereby causing a deflection of the wire gate. Method for resuming an incomplete parting of a workpiece 1 in a variety of slices with a textured wire 5 passing through at least two wire guide rollers 6 to a first wire gate comprising a plurality of parallel wire sections having a first wire tension and having a first effective diameter 9 is clamped, comprising a) removing the first wire gate from the in the workpiece 1 separating gaps formed by the first wire gate 4b b) the reintroduction of one by at least two wire guide rollers 6 with a second wire tension spanned second wire gate in the separation column 4 , characterized in that at the same wire tension in the first and in the second wire gate of the effective diameter 9 of the first wire 5 greater than the effective diameter of the second wire. A method according to claim 13, characterized in that the second wire is a structured wire 5 is. A method according to claim 13, characterized in that the second wire is a smooth wire 10 is. The method of any one of claims 1 to 15, wherein after dipping the second wire gate into the separation gap 4 at the simultaneous further delivery of the workpiece 1 on the wire gate or the wire gate on the workpiece 1 at a first speed to a) a first speed of unidirectional movement of the wire in the wire longitudinal direction is selected, the wire sections at cutting depths between greater than 0% and 33%, based on the diameter of the workpiece 1 or based on the separation gap depth, and b) before the wire gate reaches the Trennspaltgrund, a second feed rate of the workpiece 1 on the wire gate to the wire gate or on the workpiece 1 to and a second speed of the unidirectional movement of the wire in the wire longitudinal direction can be selected. The method of claim 16, wherein the second rate of concurrent further delivery of the rod to the wire gate is less than the first rate of simultaneous further delivery of the rod to the wire gate. The method of claim 16 or 17, wherein the second speed of the unidirectional movement of the wire in the wire longitudinal direction is greater than the first speed of the unidirectional movement of the wire in the wire longitudinal direction.

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