Method for cutting a plurality of slices from a workpiece by means of a wire saw during a series of cutting operations

Abstract

The invention relates to a method for cutting a plurality of slices by means of a wire saw, wherein a wire array (2) is tensioned in the plane between two wire guide rollers (1), wherein each of the two wire guide rollers (1) is mounted between a fixed bearing (5) and a floating bearing (6) and comprises at least one chamber (18) and a housing portion (8). The method comprises conveying a workpiece (4) via the wire array (2), while at the same time changing the length of the housing portions (8) of the two wire guide rollers (1) by controlling the temperature of the chambers (18) of the wire guide rollers (1) with a first cooling fluid according to a specification of a first temperature profile, and while at the same time axially moving the floating bearings (6) of the two wire guide rollers (1) by controlling the temperature of the fixed bearings (5) of the wire guide rollers (1) with a second cooling fluid according to a specification of a second temperature profile.

Description

TECHNICAL FIELD

[0001] The invention relates to a method for cutting out a plurality of slices from a workpiece during a series of parting (dicing) operations by means of a wire saw, wherein the wire saw comprises a wire array consisting of moving wire sections of a sawing wire and an actuating device, and the wire array is tensioned in a plane between two wire guide rollers, and wherein each of the two wire guide rollers is supported between a fixed bearing and a floating bearing and comprises at least one chamber and a housing part, which encloses a core part of the wire guide roller and is configured with a guide groove for the wire sections. During each of the parting operations, in the presence of a hard material and a working fluid that act abrasively on the workpiece, a respective workpiece is fed through the wire array by means of the actuating device along a feed direction that is perpendicular to the workpiece axis and to the plane of the wire array. BACKGROUND

[0002] This method for cutting out a plurality of slices can be implemented by means of a kiss-cutting slice or a grinding slice.

[0003] In the case of a kiss-cutting slice, a working fluid in the form of a slurry consisting of a hard material in a liquid carrier medium is fed to a working space formed between the wire surface and the workpiece. In the case of a kiss-cutting slice, the material is removed by means of a three-body interaction involving the tool carrier (sawing wire), the tool (abrasive) and the workpiece.

[0004] In the case of a grinding slice, a sawing wire with a hard material firmly bonded in its surface is used, and a working fluid is supplied, which itself contains no grinding material and serves as a cooling lubricant. In the case of a grinding slice, the material is removed by means of a two-body interaction involving the diamond-coated sawing wire as a tool and the workpiece.

[0005] In the case of a conventional wire saw, each of the wire guide rollers is provided near one of its end faces with a bearing that is connected in a fixed manner to the machine frame and is referred to as a fixed bearing, and near the opposite end face with a bearing that is movable relative to the machine frame in the axial direction of the wire guide roller and is referred to as a floating bearing.

[0006] The wire guide rollers of the wire array usually comprise a core part made of metal, which is usually surrounded (clad) by a housing part made of, for example, polyurethane. The housing part has a plurality of grooves for guiding the sawing wire of the wire array forming the wire saw. The housing part is usually fastened to the core part of the respective wire guide roller of the wire array so that it can expand or contract axially unhindered at both ends when there are temperature changes. Nevertheless, the housing part can be fixed to one or both sides of the wire guide roller respectively by one or two clamping rings.

[0007] There are known measures which aim to counteract changes in the arrangement of the wire array and the workpiece relative to each other during the cutting-off operation in order to improve the planar parallelism of the main surface of the slice to be cut off.

[0008] US 2002 / 0 174 861 A1 describes a method which envisages controlling the temperature of the workpiece in order to limit the warping of the slice to be cut off.

[0009] In US 2015 / 0 158 203 A1 it is proposed to selectively cause a length change of the housing portion by a temperature change in the core portion of the wire guide roller in order to improve the flatness of the cut-off slice.

[0010] US 2012 / 0 240 915 A1 describes a method which provides for independent cooling of the wire guide roller and its fixed bearings in order to reduce the relative axial movement of the wire section and the workpiece caused by temperature changes.

[0011] US 5 377 568 discloses a method in which the position of a reference surface located on the outside of the wire guide roller relative to the machine frame is measured and a thermal length increase or length decrease of the wire guide roller is achieved by adjusting the temperature inside the wire guide roller until the measured position change of the reference surface has been compensated for again.

[0012] WO 2013 / 079683 A1 discloses a method in which firstly the slice shapes obtained at different temperatures of the wire guide roller bearings are measured and each of these shapes is stored together with the corresponding associated bearing temperature, and then in a subsequent cut, the bearing temperature is selected which best matches the desired target shape.

[0013] US 5 875 770 discloses a method in which the shape of a slice from a cut is measured, a correction curve in relation to the cutting depth is calculated by forming a difference relative to a desired ideal shape of the slice, and in a subsequent cut the workpiece is moved relative to the wire array in the axial direction during the cutting-off operation in accordance with the correction curve.

[0014] Despite these measures, there is still a need for improvement, on the one hand because these measures only have a limited effect and on the other hand because the requirements for the flatness and planar parallelism of the slice are increasing, particularly in the semiconductor industry. SUMMARY

[0015] It is an object of the present application to produce a usable slice whose shape matches the target shape as closely as possible.

[0016] The object of the present invention is achieved by a method for cutting out a plurality of slices from a workpiece by means of a wire saw during a series of cutting-off operations divided into an initial cut and subsequent cuts, wherein the wire saw comprises a wire array consisting of moving wire segments of a sawing wire and an actuating device, and the wire array is tensioned in a plane between two wire guide rollers, wherein each of the two wire guide rollers is supported between a fixed bearing and a floating bearing and comprises at least one chamber and a housing portion, which encloses a core portion of the wire guide roller and is configured with a guide groove for the wire segments, the method comprising

[0017] During each of the cutting-off operations, in the presence of hard material and working fluid acting abrasively on the workpiece, a respective workpiece is fed through the wire array by means of the actuating device along a feed direction perpendicular to the workpiece axis and to the plane of the wire array, which comprises

[0018] During each of the cutting-off operations, the workpiece is fed through the wire array, while at the same time the length of the housing portions of the two wire guide rollers is simultaneously changed by regulating the temperature of the chambers of the wire guide rollers with a first cooling fluid according to a specification of a first temperature profile, which specifies the temperature of the first cooling fluid as a function of the cutting depth and is related to a first correction profile, which specifies the length variation of the housing portions as a function of the cutting depth; and

[0019] at the same time the floating bearings of the two wire guide rollers are simultaneously axially moved by regulating the temperature of the fixed bearings of the wire guide rollers with a second cooling fluid according to a specification of a second temperature profile, which specifies the temperature of the second cooling fluid as a function of the cutting depth and is related to a second correction profile, which specifies the stroke of the floating bearings as a function of the cutting depth, wherein the first and second correction profiles counteract (suppress) a shape deviation; and

[0020] The shape deviation is determined before each of the cutting-off operations.

[0021] The method can be configured to lap slices or ground slices. The cutting depth (doc) represents the length extending from a first point of contact of the wire array with the workpiece and during the ongoing cut opposite to the feed direction to the instantaneous position of the wire array in the workpiece.

[0022] For example, the changing of the axial length of the housing part and the line guide roller tensioning the line array of the line guide roller by adjusting the temperature of the chamber of the line guide roller (hereinafter referred to as line guide heat control, WGHC) can be implemented in the manner proposed in US 2015 / 0 158 203 A1. Furthermore, a first cooling fluid is passed through the chamber of the respective line guide roller according to the specification of a first temperature profile, wherein the temperature of the chamber of the line guide roller is adjusted with the first cooling fluid, the first temperature profile specifying the temperature of the first cooling fluid as a function of the cutting depth. The first temperature profile is related to a first correction profile, the first correction profile specifying the length change (via thermal expansion or contraction) of the respective housing part of the line guide roller as a function of the cutting depth. In advance, the temperature change of the first coolant required to cause the specified length change of the housing part of the respective line guide roller is determined experimentally. The first correction profile is inversely proportional to the shape deviation determined before each of the cutting operations.

[0023] More than one (one over) chamber can be provided in the core part of the line guide roller and the cooling fluid is supplied to each chamber independently, in any case the temperature of each chamber following its own temperature profile. In this case, these temperature profiles jointly cause the length change of the housing part of the respective line guide roller required by the first correction profile.

[0024] Adjusting the temperature of the fixed bearing (hereinafter referred to as line guide temperature control, WGTC) causes the position of the line guide roller and thus the position of the line array relative to the position of the workpiece (rod, ingot) to change via thermal expansion or contraction of the fixed bearing, since this causes the floating bearing and the line guide roller to move relative to the reference system common to the workpiece and the line guide roller (for example, the machine frame) in the direction of the rotational axis of the line guide roller. The method according to the invention envisages the use of WGTC in addition to WGHC, i.e. during each of the cutting operations, the workpiece is fed through the line array, at the same time the floating bearings of the two line guide rollers are simultaneously moved axially by adjusting the temperature of the fixed bearings of the line guide rollers with a second cooling fluid according to the specification of a second temperature profile, wherein the second temperature profile specifies the temperature of the second cooling fluid as a function of the cutting depth and is related to a second correction profile, the second correction profile specifying the stroke of the floating bearing as a function of the cutting depth. In advance, the temperature change of the second coolant required to cause the specified stroke of the floating bearing of the respective line guide roller is determined experimentally. The second correction profile is likewise inversely proportional to the shape deviation determined before each of the cutting operations.

[0025] The first correction profile and the second correction profile together form a total correction profile that minimizes the shape deviation.

[0026] The total correction curve preferably comprises a third correction curve which specifies a travel of the workpiece along the workpiece axis in dependence on the cutting depth and likewise counteracts the shape deviation. Thus, during each of the severing operations, preferably together with the WGHC and the WGCT, the following procedure is carried out, namely the workpiece is fed through the wire array, at the same time the workpiece is moved along the workpiece axis according to the specification of the third correction curve by means of an actuating element (hereinafter referred to as ingot positioning control, IPC). The actuating element is preferably a piezoelectric actuator.

[0027] There are specific advantages associated with the combination of WGHC, WGTC and IPC. If these three measures are used in combination, a greater amplitude of movement (travel amount) of the wire guide roller relative to the workpiece can be achieved than when only one of these measures is used. The range in which the movement of the floating bearing and the workpiece is linearly dependent on the variable which causes the movement is wider than the corresponding range which can be achieved when only one of the measures is used. Due to the thermal inertia of the masses involved, the response time from changing the variable which causes the movement to the actual occurrence of the movement is significantly longer in the case of WGHC and WGTC than in the case of IPC, in particular if the actuating element is a piezoelectric actuator which reacts almost instantaneously. The WGHC and WGTC measures on the one hand and the IPC measure on the other hand thus have different control bandwidths. It is therefore advantageous to counteract (suppress) shape deviations which are relatively high in frequency, i.e. shape deviations which change with a relatively large gradient in dependence on the cutting depth, by means of IPC and to counteract shape deviations which are relatively low in frequency by means of WGHC and WGTC.

[0028] The shape deviation is determined before the severing operation and refers to the deviation of the shape curve of the slice or the average shape curve of the slices from a reference shape curve.

[0029] The determination of the shape deviation is preferably based on a comparison of the average shape curve of the slices which have already been cut off with the reference shape curve. This comparison provides a total correction curve which determines even before the severing operation the length change of the housing part of the wire guide roller (by means of WGHC), the travel of the wire guide roller (by means of WGTC) and, if applicable, the travel of the workpiece (by means of IPC) which are required in order to avoid the shape deviation which would be expected without the use of these countermeasures in dependence on the cutting depth (as a function of the cutting depth). The total correction curve is divided into a first correction curve and a second correction curve and, if applicable, a third correction curve, and this determines the proportions of the length change or the travel which are to be carried out by means of WGHC and WGTC and, if applicable, by means of IPC. The proportions can be divided equally or differently.

[0030] The surface of the slice consists of the main surface and the edge surface. The main surface comprises the front side and the back side of the slice. As is common in the case of warpage measurements, the slice can be measured by being arranged between a pair of sensors. Each of the sensors measures the distance of the slice facing the main surface at a measurement point. The measurement points can be distributed over the main surface or can be positioned along the diameter of the slice. The measurement points are preferably located at positions i along the diameter of the slice, in particular opposite the feed direction, and thus each measurement point is associated with a specific cutting depth. The density of the measurement points is preferably not less than 1 per cm, and the distance between one measurement point and the nearest adjacent point is preferably the same for all measurement points.

[0031] The shape curve of the slice is the line connecting the measurement points si, which are calculated at positions i according to the rule si = ½ [D - (FDi - BDi)], wherein D is the distance between the sensors, FDi is the distance between the upper sensor and the respective measurement point on the front side of the slice, and BDi is the distance between the lower sensor and the respective measurement point on the back side of the slice. It should be noted that the present invention can also be implemented using an alternative definition of the shape curve, as long as this alternative definition encodes the shape of the slice as a function of the slice depth (as a function of the cutting depth).

[0032] The average shape curve of the slice is a shape curve obtained by averaging the shape curves of a plurality of slices. The reference shape curve is a desired (ideal) shape curve, preferably the shape curve of a slice having perfectly flat and mutually parallel main surfaces. The average shape curve is determined for slices resulting from preferably 1 to 5 (sets of) dicing operations by means of the same wire saw, wherein these dicing operations are (already) performed immediately prior to the dicing operation to be implemented by the wire saw. The selection of the slices for the creation of the average shape curve can be slice-based or cutting-based, or can include both. In case of a slice-based selection, certain slices from each dicing operation are used to determine the respective average shape curve by averaging, while other slices are excluded. For example, only those slices having a specific position in the workpiece are considered in the averaging process, for example only every 15th to 25th slice along the workpiece axis. Another possibility for a slice-based selection is to exclude the slices having the largest and smallest shape curve deviation with respect to the average shape curve of all slices in the dicing operation (so-called trimmed mean). Alternatively, slices whose shape curve deviates more than 1 to 2 sigma (sigma) from the average shape curve of all slices in the dicing operation can be excluded from the averaging slices. In a cutting-based selection, all slices from at least one dicing operation are used to determine the average shape curve, and all slices from at least one other dicing operation are excluded therefrom.

[0033] The average shape profile of the slices in the cutting operation changes over the course of a series of cutting operations. The changes are preferably used to assess the performance of the wire saw. They can indicate wear of the saw wire and / or of the housing of the wire guide rollers or of some other component of the wire saw that is subject to wear. Therefore, preferably, a threshold value of the shape deviation is defined, when this threshold value is reached or exceeded, a maintenance activity (predictive maintenance activity) is initiated instead of another cutting operation. Even before such a threshold value is reached, the changes can be used as a reason to take measures to counteract a deterioration of the work result due to wear. For example, such measures can be a change of the composition and / or temperature of the working fluid and / or a change of the saw wire speed and / or other process-specific parameters.

[0034] The cutting operation that is carried out after a change in the saw system represents a special case. Such a change in the saw system occurs, for example, when there is a change in the wire guide rollers, a mechanical adjustment of the wire saw or a change in the physical or chemical properties of the working fluid. The first or initial cutting operation after a change in the saw system, the so-called initial cut, preferably consists of 1 to 5 cutting operations. For the initial cut, the shape deviation is preferably determined by comparing the average shape profile of the slices with a reference shape profile, wherein the average shape profile of the slices produced by the same wire saw in the course of one or more initial cuts before the saw system was changed is used.

[0035] In addition, preferably, during each of the cutting operations, instead of the IPC or as a fourth measure in addition to the WGHC, the WGTC and the IPC, control of the temperature of the workpiece is provided (ingot cooling, IC), more particularly by wetting the workpiece with a cooling medium by means of a closed control loop, wherein the temperature of the workpiece forms the controlled variable and the temperature of the cooling medium forms the manipulated variable of the control loop. The reference variable of the control loop is preferably a constant temperature. The cooling medium is preferably a fluid or the working fluid used in the overlap slices or the ground slices. By controlling the temperature of the workpiece, additionally, the shape deviation of the slices caused by thermal expansion of the workpiece can be limited. The control loop can be implemented, for example, as described in US 2002 / 0 174 861 Al. In principle, it is also possible to implement the method which envisages the combination of the WGHC and the IC as measures only.

[0036] The wire saw used according to the application comprises two or more wire guide rollers, for example three or four wire guide rollers. The temperature regulation of the chambers and the fixed bearings of the wire guide rollers can be limited to the two wire guide rollers between which the wire array is tensioned and by means of which the workpiece is fed (fed in).

[0037] The workpiece is preferably composed of a semiconductor material, such as silicon, in polycrystalline or single-crystalline state. The cross-section of the workpiece is square, rectangular or circular. In the case of a cylindrical workpiece, the workpiece axis extends through the center of the cylinder. The method according to the application is particularly suitable for producing circular semiconductor wafers composed of single-crystalline silicon, having a diameter of at least 200 mm, in particular at least 300 mm.

[0038] Details of the application are described below with reference to the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 Features of the wire saw that play a role in the use of the application are shown schematically.

[0040] Figure 2 Details of these features are shown.

[0041] Figure 3 Further details of these features are shown.

[0042] Figure 4 The arrangement of the slice between the two sensors for determining the shape deviation of the slice before the cutting operation is shown.

[0043] Figure 5 Details of features related to the use of the preferred exemplary embodiment of the WGHC and the WGTC are shown.

[0044] Figure 6 Details of features related to the use of another preferred exemplary embodiment of the WGHC and the WGTC are shown.

[0045] LIST OF USED REFERENCE SIGNS

[0046] 1 wire guide roller (wire guide roll)

[0047] 2 wire array

[0048] 3 sawing wire

[0049] 4 workpiece

[0050] 5 fixed bearing

[0051] 6 floating bearing

[0052] 7 machine frame

[0053] 8 housing part

[0054] 9 space for internal temperature regulation of the fixed bearing for the WGTC

[0055] 9a space for external temperature regulation of the fixed bearing for the WGTC

[0056] 10 direction arrow

[0057] 11 directional arrow

[0058] 12 actuating device

[0059] 13 control unit for WGHC

[0060] 14 data processing unit

[0061] 15 control unit for IPC

[0062] 16 control unit for WGTC

[0063] 17 core portion

[0064] 18 cavity

[0065] 19 upper sensor

[0066] 20 lower sensor

[0067] 21 slice

[0068] 22 device for adjusting the temperature of the workpiece

[0069] 23 axis of rotation

[0070] 24 screw

[0071] 25 flow direction

[0072] 26 directional arrow DETAILED DESCRIPTION

[0073] Figure 1Features of a wire saw suitable for implementing the method according to the present application are shown. The wire saw comprises a wire array 2 consisting of moving line sections of a sawing wire 3, which is tensioned in a plane between two wire guide rollers 1. During a cutting operation, a workpiece 4 is fed through the wire array 2 along a feed direction perpendicular to the workpiece axis and to the plane of the wire array 2 by means of an actuating device 12. During said operation, the length of the wire guide rollers 1 (and thus the length of their housing parts 8) tensioning the wire array 2 is changed in the direction corresponding to the direction arrow 10 according to a first correction curve, and the floating bearings 6 of the respective wire guide rollers (and the respective wire guide rollers themselves) are moved in the direction corresponding to the direction arrow 10 according to a second correction curve. Furthermore, the workpiece 4 can be moved simultaneously in the direction of the workpiece axis corresponding to the direction arrow 11 according to a third correction curve, and / or the temperature of the workpiece 4 can be controlled by wetting the workpiece 4 with a cooling medium by means of a closed control loop, wherein the temperature of the workpiece 4 forms the controlled variable and the temperature of the cooling medium forms the manipulated variable of the control loop. The first and second correction curves and, if applicable, the third correction curve are designed to counteract (suppress) the shape deviations determined before each of said cutting operations. The first and second correction curves and, if applicable, the third correction curve are stored in a data processing unit 14. First and second control units 13, 16 for implementing the WGHC and the WGTC and, if applicable, a third control unit 15 for implementing the IPC control heat exchangers for adjusting the temperature of the cavities of the wire guide rollers and of the fixed bearings and, if applicable, actuating elements that initiate (cause) the movement of the workpiece 4 in the direction along the workpiece axis (indicated by the direction arrow 11) depending on the cutting depth according to the third correction curve. If the use of an IC is envisaged, the wire saw also comprises a device 22 for adjusting the temperature of the workpiece 4. By means of this device 22, during each of said cutting operations, the workpiece 4 is fed through the wire array 2, while the temperature of the workpiece 4 is controlled by wetting the workpiece 4 with a cooling medium by means of a closed control loop, wherein the temperature of the workpiece 4 forms the controlled variable and the temperature of the cooling medium forms the manipulated variable of the control loop.

[0074] As Figure 2As shown, the wire guide roller 1 is mounted between a fixed bearing 5 and a floating bearing 6. The fixed bearing 5 and the floating bearing 6 are supported on a frame 7. The core part 17 of the wire guide roller 1 is surrounded by a housing part 8, which is provided with a groove in which the saw wire 3 runs. The fixed bearing 5 comprises a space 9 for internal temperature regulation and / or a space 9a for external temperature regulation, through which a second cooling fluid passes in order to regulate the temperature of the fixed bearing 5. If the temperature of the second cooling fluid is increased, the thermal expansion of the fixed bearing 5 causes an axial movement of the wire guide roller 1 in the direction of the floating bearing 6, and the floating bearing 6 moves outwardly in relation to the frame 7 in the direction indicated by the directional arrow 10. If the temperature of the second cooling fluid is decreased, a movement of the wire guide roller 1 and the floating bearing 6 in the opposite direction is caused. The temperature of the second cooling fluid is specified by a second temperature profile, which is dependent on the cutting depth, in relation to a second correction profile. A control unit 16, which is connected to a heat exchanger and a pump, ensures that the second cooling fluid, which passes through the fixed bearing 5, has the temperature specified by the second temperature profile when a certain cutting depth is reached. The data processing unit 14 transmits the second temperature profile to the control unit 16, which causes a movement of the floating bearing in accordance with the second correction profile.

[0075] Figure 3 Two cavities in the core part 17 of the wire guide roller are shown, which form two chambers 18, through which a first cooling fluid passes in order to regulate the temperature of the chambers 18 in order to change the length of the housing part 8 of the respective wire guide roller in the direction corresponding to the directional arrow 10 in accordance with the specification of the first correction profile (technical parameters or content). The bolt 24 coaxially connects the fixed bearing 5 and the floating bearing 6.

[0076] Figure 4 An arrangement of the cut piece 21 between two sensors 19, 20 for determining the shape deviation before the cutting operation is shown. The sensors 19, 20 measure the distance FD1 of the sensor 19 from the front side of the cut piece 21 and the distance BD1 of the lower sensor 20 from the back side of the cut piece 21 at a certain position i along the diameter of the cut piece 21 in the feed direction according to a certain cutting depth. The shape curve of the cut piece is a line connecting the measured values si calculated according to the rule si = ½ [D - (FD1 - BD1)], wherein D denotes the distance between the sensors. The shape deviation of the cut piece is obtained by comparing the shape curve of the cut piece with a reference shape curve. The deviation in relation to the reference shape curve dependent on the cutting depth corresponds to the total correction profile, which is divided between the WGHC and the WGTC and, if applicable, the IPC, in the form of the first correction profile and the second correction profile and, if applicable, the third correction profile.

[0077] Figure 5Details of the features of a preferred exemplary embodiment using WGHC and WGTC are shown.

[0078] The control unit 13 for WGHC (length variation of the outer shell portion 8 of the line guide roller 1 in a direction 10 parallel to its axis of rotation 23) regulates the temperature of the first cooling fluid, which, after being distributed in parallel, first passes through the chamber 18 spanning the two upper line guide rollers of the line array. The first cooling fluid is then recombined and returned to the control unit 13.

[0079] The control unit 16 for WGTC (movement of the line guide roller 1 in direction 26 parallel to its axis of rotation 23) regulates the temperature of the second cooling fluid, which, after being distributed in parallel, first passes through the internal temperature regulation space 9 of the fixed bearing 5 for the two upper line guide rollers spanning the line array. Then, the second cooling fluid is used to regulate the temperature of the two lower line guide rollers before they are recombined and return to the control unit 16. Temperature regulation of the lower line guide rollers is not absolutely necessary, but rather to dissipate frictional heat generated here, for example, as a result of bearing friction during the rotation of the line guide rollers. The flow directions of the first and second cooling fluids are indicated by arrow 25. The first and second cooling fluids are supplied to and discharged from the rotating line guide rollers via a rotating fluid supply passage. A coaxial dual rotating supply passage is used.

[0080] exist Figure 5 In the exemplary embodiment shown, WGTC is therefore used by means of internal temperature regulation of the fixed bearing and the supply and discharge of a second cooling fluid via a coaxial dual-rotation supply passage. The second cooling fluid is supplied in and out (input and output) via a rotational supply passage mounted on the fixed bearing side, and the first cooling fluid is supplied in and out via a rotational supply passage mounted on the floating bearing side. The temperature regulation circuit for WGTC passes through the upper and lower guide rollers, while the temperature regulation circuit for WGHC passes only through the upper guide roller.

[0081] Figure 6 Details of features of another preferred exemplary embodiment using WGHC and WGTC are shown.

[0082] The control unit 13 for WGHC (length variation of the outer shell portion 8 of the line guide roller 1 in a direction 10 parallel to its axis of rotation 23) regulates the temperature of a first cooling fluid, which, after being distributed in parallel, first passes through chambers 18 spanning the two upper line guide rollers of the line array. The first cooling fluid is then used to regulate the temperature of the two lower line guide rollers before they are recombined and return to the control unit 13.

[0083] The control unit 16 for the WGTC (movement of the wire guide rollers 1 in the direction 26 parallel to their rotation axis 23) regulates the temperature of the second cooling fluid which, after being split in parallel, first passes through the externally temperature-regulated space 9a for the stationary bearings 5 of the two upper wire guide rollers across the wire array, and then is used to regulate the temperature of the two lower wire guide rollers before being reunited again and returned to the control unit 16.

[0084] Therefore, in Figure 6 In the exemplary embodiment shown, WGTC by means of external temperature regulation of the stationary bearings is used. The first cooling fluid is supplied and discharged via rotating supply channels mounted on the stationary bearing side. The supply and discharge of the second cooling fluid is carried out via stationary threaded fasteners at the outer bushings of the stationary bearings.

[0085] The above description of illustrative embodiments should be understood not to limit the application in any way. The disclosure made thereby enables a person skilled in the art to understand the application and the advantages associated therewith, on the one hand, and also includes variations (changes) and modifications of the described structures and methods within the understanding of a person skilled in the art, on the other hand.

Claims

1. A method for cutting multiple slices from a workpiece using a wire saw during a series of cutting operations divided into an initial cut and subsequent cuts, wherein, The wire saw includes a wire array consisting of moving wire segments and an actuation device, wherein the wire array is tensioned in a plane between two wire guide rollers, each of which is supported between a fixed bearing and a floating bearing and includes at least one chamber and a housing portion, the housing portion surrounding the core portion of the wire guide roller and being configured with guide grooves for the wire segments, the method comprising During each of the cutting operations, in the presence of abrasive hard material and working fluid acting on the workpiece, the corresponding workpiece is fed through the linear array by means of the actuating device along a supply direction perpendicular to the workpiece axis and perpendicular to the plane of the linear array, which includes During each of the cutting operations, the workpiece is fed through the linear array, while simultaneously changing the length of the outer shell of the two linear guide rollers by adjusting the temperature of the chambers of the linear guide rollers using a first cooling fluid according to a first temperature profile, the first temperature profile specifying the temperature of the first cooling fluid based on the cutting depth and related to a first correction curve, the first correction curve specifying the change in the length of the outer shell based on the cutting depth; and At the same time, the floating bearings of the two line guide rollers are moved axially simultaneously by adjusting the temperature of the fixed bearing of the line guide roller according to the specification of the second temperature curve using the second cooling fluid. The second temperature curve depends on the cutting depth to specify the temperature of the second cooling fluid and is related to the second correction curve. The second correction curve depends on the cutting depth to specify the stroke of the floating bearing. The first correction curve and the second correction curve are opposite to the shape deviation. as well as The shape deviation is determined before each of the cutting operations, wherein the shape deviation is determined by comparing the average shape curve of the cut slice with a reference shape curve.

2. The method as described in claim 1, wherein, The average shape curve is determined by averaging the shape curves of the selected slices, wherein the selection is based on slices, based on cuts, or based on both slices and cuts.

3. The method as described in claim 1 or 2, wherein, The cut slices are derived from at least 1 to 5 cutting operations that immediately precede the corresponding cutting operation.

4. The method as described in any one of claims 1 to 3, wherein, The method includes feeding the workpiece through the linear array while simultaneously moving the workpiece along the workpiece axis using an actuating element according to a third correction curve, wherein the third correction curve specifies the stroke of the workpiece, and wherein the third correction curve is opposite to the shape deviation.

5. The method according to any one of claims 1 to 4, wherein, During each of the cutting operations, the temperature of the workpiece is controlled by means of a closed control loop by wetting the workpiece with a cooling medium, wherein the temperature of the workpiece forms a controlled variable and the temperature of the cooling medium forms a manipulated variable of the control loop.

6. The method of claim 5, wherein, The constant temperature is designated as the reference variable for the control loop.

7. The method according to any one of claims 1 to 6, wherein If the shape deviation determined before the corresponding cutting operation reaches or exceeds a given threshold, maintenance measures are initiated instead of the corresponding cutting operation.

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