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 separating a plurality of slices from a workpiece (4) by means of a wire saw, wherein a wire grid (2) is tensioned in the plane between two wire guide rollers (1), and wherein each of the two wire guide rollers (1) is mounted between a fixed bearing (5) and a floating bearing (6). The method comprises transporting the workpiece (4) through the wire grid (2) by controlling the temperature of the fixed bearing (5) with a cooling fluid according to a specification of a first temperature profile while moving the floating bearing (6) axially, and moving the workpiece (4) along the workpiece axis simultaneously by means of a control element according to a specification of a second correction profile, determining a shape deviation, and adjusting operating parameters depending on the cutting depth.

Description

Technical Field

[0001] This invention relates to a method for cutting multiple slices from a workpiece using a wire saw during a series of cutting operations. The wire saw comprises an array of moving wire segments and an actuating device. 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. During each cutting operation, in the presence of a working fluid and a hard material, the corresponding workpiece is fed through the wire array via the actuating device in a feed direction perpendicular to the workpiece axis and perpendicular to the plane of the wire array, the hard material acting abrasively on the workpiece.

[0002] Existing technology / problems

[0003] This method of cutting multiple slices can be achieved by overlapping or grinding the slices.

[0004] In the case of overlapping cuts, the working fluid is supplied in the form of a slurry composed of hard materials in a liquid carrier medium to the working space formed between the cutter surface and the workpiece. In the case of overlapping cuts, material is removed by means of the three-body interaction involving the tool carrier (cutting line), the tool (abrasive), and the workpiece.

[0005] In the case of abrasive cutting, a saw filament with a hard surface material is used, and a working fluid that does not contain abrasive material itself and serves as a cooling lubricant is provided. In the case of abrasive cutting, the material is removed by means of a two-body interaction involving the diamond-coated saw filament as a tool and the workpiece.

[0006] In the case of a conventional wire saw, each wire guide roller has a bearing near each of its end faces, which is fixedly connected to the machine frame and is called a fixed bearing, and a bearing near the opposite end face, which can move relative to the machine frame in the axial direction of the wire guide roller and is called a floating bearing.

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

[0008] US 5,377,568 discloses a method in which the position of a reference surface located on the outside of a line guide roller relative to a machine frame is measured, and an increase or decrease in thermal length in the line guide roller is caused by adjusting the temperature inside the line guide roller until the change in the measured position of the reference surface is compensated again.

[0009] WO 2013 / 079683 A1 discloses a method in which the slice shapes obtained at different temperatures of an online guide roller bearing are first measured and each of these shapes is stored together with its respective associated bearing temperature, and then the bearing temperature that best matches the desired target shape is selected in subsequent cutting.

[0010] US 5,875,770 discloses a method in which the shape of a cut slice is measured, a correction curve dependent on the cutting depth is calculated by forming a difference from the ideal shape of the slice relative to the desired slice, and in a subsequent cut, during the cutting operation, the workpiece is moved in an axial direction relative to the linear array according to the correction curve.

[0011] US2002 / 0 174 861A1 describes a method that envisions controlling the temperature of a workpiece to limit warping of cut slices.

[0012] Despite these measures, continuous improvement is still needed, partly because these measures have only limited effectiveness, and partly because the requirements for the flatness and parallelism of the slices are becoming increasingly stringent, especially in the semiconductor industry. Summary of the Invention

[0013] The purpose of this invention is to provide slices whose shape matches the target shape as closely as possible.

[0014] According to a first embodiment, the object of the present invention is achieved by 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. The wire saw comprises a wire array formed by moving segments of sawing wires and an actuating device, and 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. The method includes, during each cutting operation, in the presence of working fluid and hard material, feeding the corresponding workpiece through the wire array at a feed rate along a feed direction perpendicular to the workpiece axis and perpendicular to the plane of the wire array by means of the actuating device. The hard material abrades the workpiece. On the workpiece, this includes, during each cutting operation, feeding the workpiece through the linear array by adjusting the temperature of the fixed bearing with cooling fluid according to a first temperature profile specified by a first temperature profile, which depends on the cutting depth, specifies the temperature of the cooling fluid, and is related to a first correction profile, which depends on the cutting depth, specifies the stroke of the floating bearing; determining the shape deviation during and / or before each cutting operation; and setting operating parameters depending on the cutting depth, which include at least one of feed rate, amount of working fluid supplied to the linear array per unit time, temperature of the working fluid, linear velocity, linear consumption per cutting operation, and linear tension.

[0015] According to a second embodiment, the object of the present invention is achieved by 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. The wire saw comprises a wire array formed by moving segments of a sawing wire and an actuating device, and 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. The method includes, during each cutting operation, in the presence of working fluid and hard material, using the actuating device to feed at a feed rate along a feed direction perpendicular to the workpiece axis and perpendicular to the plane of the wire array. The corresponding workpiece is fed through a linear array, where the hard material abrades the workpiece. This includes feeding the workpiece through the linear array while simultaneously moving the workpiece along the workpiece axis by means of an actuating element according to a second correction curve that specifies the workpiece's stroke, wherein the second correction curve is opposite to the shape deviation; determining the shape deviation during and / or before each cutting operation; and setting operating parameters depending on the cutting depth, which include at least one of feed rate, the amount of working fluid supplied to the linear array per unit time, the temperature of the working fluid, linear velocity, linear consumption per cutting operation, and linear tension.

[0016] According to a third embodiment, the object of the present invention is achieved by 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. The wire saw comprises a wire array formed by moving segments of a sawing wire and an actuating device, and 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. The method includes, during each cutting operation, feeding the corresponding workpiece through the wire array at a feed rate along a feed direction perpendicular to the workpiece axis and perpendicular to the plane of the wire array, in the presence of a working fluid and a hard material, by means of the actuating device, in the presence of a working fluid and a hard material, the hard material acting abrasively on the workpiece. This includes, during each cutting operation, adjusting the hard material with a cooling fluid according to a first temperature profile. The process involves: determining the temperature of a fixed bearing; feeding a workpiece through a linear array using simultaneous axial movement of a floating bearing; a first temperature profile, which depends on the cutting depth and specifies the temperature of the cooling fluid, and is correlated with a first correction profile, which depends on the cutting depth and specifies the stroke of the floating bearing; feeding the workpiece through the linear array while simultaneously moving the workpiece along its axis by means of an actuating element according to a second correction profile, which specifies the stroke of the workpiece, wherein the first and second correction profiles are opposite to shape deviations; determining the shape deviation during and / or before each cutting operation; and setting operating parameters, depending on the cutting depth, including at least one of feed rate, amount of working fluid supplied to the linear array per unit time, working fluid temperature, linear velocity, linear consumption per cutting operation, and linear tension.

[0017] The methods according to the first, second, and third embodiments can be configured to overlap or grind slices. The cutting depth (doc) refers to the length in the region from the entry cut into the workpiece to the exit cut out of the workpiece, opposite to the feed direction.

[0018] It has been found that a combination of changing the relative position of the workpiece and the line segments of the line array according to the first and / or second calibration curves and setting operating parameters such as feed rate, amount of working fluid supplied to the line array per unit time, temperature of the working fluid, line velocity, line consumption per cut operation, and line tension is particularly suitable for achieving this purpose, provided that the operating parameters are matched to these applications.

[0019] It is further advantageous to feed the workpiece through the linear array during each cutting operation, while controlling the workpiece temperature by wetting the workpiece with a cooling medium, regardless of whether it is operated according to the first, second or third embodiment.

[0020] Adjusting the temperature of the fixed bearing (hereinafter referred to as line guide temperature control, WGTC) will cause the fixed bearing and therefore its components to contract or expand in the axial direction of the line guide roller, thereby causing axial movement of the floating bearing and thus movement of the line guide roller relative to the workpiece.

[0021] Regulating the temperature of the fixed bearing has the same qualitative effect as moving the workpiece along its axis by means of an actuating element (hereinafter referred to as ingot positioning control, IPC). The actuating element is preferably a piezoelectric actuator. Therefore, the variable that causes the corresponding stroke is the temperature of the cooling fluid in the case of WGTC, and the signal used to drive the actuating element in the case of IPC.

[0022] Wetting the workpiece with a cooling medium (ingot cooling, IC) can cause a change in the workpiece length, which in turn will cause relative movement between the workpiece and the line segments of the linear array.

[0023] According to a first embodiment of the invention, WGTC is executed with operating parameters matching it; according to a second embodiment, IPC is executed with operating parameters matching it; and according to a third embodiment, both WGTC and IPC are executed with operating parameters matching them.

[0024] Regardless of which of the three embodiments is used, the matching operation parameters are as follows:

[0025] The feed rate of the workpiece through the linear array is preferably not less than 2.6 mm / min and not more than 4.25 mm / min, and particularly preferably not less than 2.6 mm / min and not more than 3.4 mm / min.

[0026] The amount of working fluid supplied to the linear array per unit time is preferably not less than 15 kg / min and not more than 42 kg / min, and particularly preferably not less than 34 kg / min and not more than 42 kg / min.

[0027] The temperature of the working fluid is preferably not less than 20°C and not more than 34°C, and particularly preferably not less than 28°C and not more than 34°C.

[0028] The linear velocity at which the line segment is moved is preferably not less than 6 m / s and not more than 14 m / s, and particularly preferably not less than 6 m / s and not more than 10 m / s.

[0029] The line tension is preferably not less than 25N and not more than 35N.

[0030] The line consumption for each cutting operation is preferably not less than 50km and not more than 72km, and particularly preferably not less than 50km and not more than 70km.

[0031] The third embodiment is particularly preferred because it provides the use of WGTC and IPC in combination with matched operating parameters to minimize any possible shape deviations. This method has particular advantages. When WGTC and IPC are used in combination, the magnitude (stroke) of the line guide roller's movement relative to the workpiece can be achieved, which is greater than that possible when only one of the measures is used. The range of movement of the floating bearing and the workpiece, which linearly depends on the variable causing the movement, is wider than the corresponding range available when only one measure is used. From the change of the variable causing the movement to the actual occurrence of the movement, a significantly longer response time is required in the case of WGTC than in the case of IPC, especially if the actuating element is a piezoelectric actuator. Therefore, the two measures have different control bandwidths. Thus, it is advantageous to combat relatively high-frequency shape deviations, i.e., shape deviations that vary with a relatively large gradient according to the cutting depth, by means of IPC, and relatively low-frequency shape deviations by means of WGTC. Due to the different response times, control by IPC can be used to suppress overshoot by control by WGTC. Furthermore, the control bandwidth of the combination of IPC and WGTC is greater than the control bandwidth of either IPC or WGTC alone. The combination of the two measures makes it possible to achieve a greater stroke per unit time, because the movement of the floating bearing and the workpiece is performed by two independent actuators.

[0032] If shape deviation is determined before the cutting operation, the term shape deviation refers to the deviation of the slice's shape curve or the average shape curve of the slice from a reference shape curve.

[0033] If shape deviation is determined during the cutting operation, the term shape deviation refers to the deviation of the position of a line passing through the center of the observed cut, or the deviation of the position of the average of multiple such lines from the position of a reference trajectory. If the cutting operation is completely fault-free, i.e., there is no unexpected axial movement of the line guide rollers and / or axial movement of the workpiece, then the line and the reference trajectory have the same position with respect to a common reference. The common reference is a position that remains stationary in space, such as a position on the frame. If multiple cuts are observed, the positions of the lines passing through the center of the cuts are averaged to give the position of the average line. A point at the same height as the line or average line and the reference trajectory represents a specific cutting depth. Therefore, the distance of such a point on the line or average line to the corresponding point on the reference trajectory indicates the shape deviation at the cutting depth represented by that point.

[0034] Observation of one or more incisions is preferably performed by irradiation with light, IR, X-rays, or gamma rays. Additionally, mechanical scanning of the incisions or measurement of their inductance or capacitance may also be considered.

[0035] Determine shape deviations during and / or before each cutting operation.

[0036] According to a variation of the third embodiment, the determination of shape deviation is based on observing one or more cuts during the cutting operation and establishing two closed control loops. The first control loop responds to control errors, i.e., to the determined shape deviation, by means of a WGTC (WGee Controlled Tunneling Control), and the second control loop responds by means of an IPC (Integrated Circuit Control), wherein the movement of the floating bearing and the workpiece to correct the shape deviation is performed using work distributed between the loops. The floating bearing is moved by means of a WGTC according to a first correction curve, which determines the stroke of the floating bearing based on the cutting depth. A first temperature curve, which specifies the coolant temperature based on the cutting depth, is correlated with the first correction curve. The required temperature change of the cooling fluid to cause the specified stroke of the floating bearing of the corresponding guide roller is determined beforehand through experiments. The first correction curve determines the proportion of stroke performed by the floating bearing based on the cutting depth to reduce the shape deviation. The workpiece is moved by means of an IPC according to a second correction curve. The second correction curve determines the proportion of stroke performed by the workpiece based on the cutting depth to reduce the shape deviation. The sum of the two proportions corresponds to the stroke required to reduce the determined shape deviation. The stroke proportions can be allocated equally or differently. Preferably, another proportional relative movement between the workpiece and the line segments of the line array is considered in the form of a third correction curve, which specifies that the length of the workpiece depends on the change in cutting depth. The change in length is achieved by wetting the workpiece with a cooling medium (ingot cooling, IC).

[0037] According to a further variation of the third embodiment, the determination of shape deviation is based on a comparison of the average shape curve of the cut slices with a reference shape curve. This comparison provides a basis for determining the required stroke, dependent on the cutting depth, even before the cutting operation, to avoid shape deviation, which is expected in the absence of countermeasures, given this comparison. The entire correction curve is divided into first and second correction curves and, where applicable, a third correction curve. This determines the stroke ratio to be performed by means of WGTC and IPC, and, where applicable, the workpiece length variation by means of IC. In this case, the stroke and length variation ratios of the workpiece can also be divided equally or in other proportions.

[0038] According to a further variation of the third embodiment, WGTC and IPC are used to offset shape deviations, the determination of which is performed during each cutting operation, and IC is used to offset shape deviations determined before each cutting operation, and vice versa.

[0039] According to a further variation of the third embodiment, WGTC and IC are used to offset shape deviations, the determination of which is performed during each cutting operation, and IPC is used to offset shape deviations determined before each cutting operation, and vice versa.

[0040] According to a further variation of the third embodiment, IPC and IC are used to offset shape deviations, the determination of which is performed during each cutting operation, and WGTC is used to offset shape deviations determined before each cutting operation, and vice versa.

[0041] The surface of the slice consists of a main surface and edge surfaces. The main surface includes the front and back sides of the slice. The slice can be measured by being arranged between a pair of sensors, which is common in the case of warped measurements. Each sensor measures the distance to the main surface facing the slice at a measurement point. The measurement points can be distributed on the main surface or located on the slice diameter at a deviation of no more than ±20° from the feed direction. The measurement points are preferably located at position i along the diameter of the slice, specifically opposite to the feed direction, and thus each measurement point is associated with a specific cutting depth. The density of measurement points is preferably not less than one per centimeter, and the distance between a measurement point and its nearest neighbor is preferably the same for all measurement points.

[0042] The shape curve of the slice is the line connecting measurement points si, which are calculated at position i according to the rule si = D - (FDi - BDi), where D is the distance between the sensors, FDi is the distance between the upper sensor and the corresponding measurement point on the front side of the slice, and BDi is the distance between the lower sensor and the corresponding measurement point on the rear side of the slice. It should be noted that alternative definitions of the shape curve can also be used to implement this invention, provided that such alternative definitions encode the shape of the slice based on the cutting depth.

[0043] The average shape curve of a slice is a shape curve obtained by averaging the shape curves of multiple slices. The reference shape curve is the desired shape curve, preferably the shape curve of a slice with perfectly flat and mutually parallel main surfaces. The average shape curve of the slices is determined, preferably derived from at least 1 to 5 cutting operations performed by the same wire saw, where these cutting operations immediately precede those performed by the wire saw. The selection of slices for generating the average shape curve can be based on slices or cuts, or may include both. In the case of slice-based selection, certain slices from the cutting operations are used to determine the corresponding average shape curve by averaging, while others are excluded. For example, only slices with specific positions in the workpiece are considered during the averaging process, such as only every 15th to 25th slices along the workpiece axis. Another possibility based on slice selection is to exclude some slices from all the slices in the cutting operations that have shape curves with the largest and smallest deviations from the average shape curve of all slices (so-called trimmed average). Alternatively, slices whose shape curves deviate from the average shape curve of all slices in the cutting operations by more than 1 to 2 sigma can be excluded from the average slices. In the cut-based selection, all slices from at least one cut operation are used to determine the average shape curve and all slices from at least one other cut operation are excluded.

[0044] During a series of cutting operations, the average shape profile of the slices changes. These changes are preferably used to evaluate the performance of the wire saw. They can indicate wear on the surface layer of the sawing wire and / or the wire guide roller, or on any other wear-affected component of the wire saw. Therefore, preferably, a threshold for shape deviation is defined, and when this threshold is reached or exceeded, maintenance activities (predictive maintenance activities) are initiated instead of further cutting operations. Even before such a threshold is reached, such changes can be used as an opportunity to take adjustment measures to counteract the deterioration of work results due to wear. Such adjustment measures can be, for example, changing the composition and / or temperature of the working fluid and / or changing the linear speed and / or other process-specific parameters.

[0045] The cutting operation that occurs after a change in the saw system represents a special case. This change occurs, for example, when there is a change in the wire guide roller, a mechanical adjustment to the wire saw, or a change in the physical or chemical properties of the working fluid. The first cutting operation after changing the saw system, the so-called initial cut, preferably comprises 1 to 5 cutting operations. For the initial cut, the shape deviation is preferably determined by comparing the average shape curve of the slice with a reference shape curve, wherein the average shape curve of the slice produced by the same wire saw during one or more initial cutting processes performed before changing the saw system is used.

[0046] A preferred suggestion is to additionally control the workpiece temperature during each cutting operation, more specifically by wetting the workpiece with a cooling medium (spool cooling, IC). According to variations of the first, second, and third embodiments, control is performed by means of a closed control loop, wherein the workpiece temperature forms the control variable and the cooling medium temperature 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 working fluid used for overlapping or grinding slices. By controlling the workpiece temperature, shape deviations of the slices caused by thermal expansion of the workpiece can be limited. The control loop can be implemented, for example, as described in US2002 / 0174861A1.

[0047] According to preferred variations of the first, second, and third embodiments, the workpiece temperature is controlled according to a second temperature profile, which depends on the temperature of the cooling medium specified by the cutting depth. The second temperature profile is correlated with a third correction profile, which is opposite to the shape deviation. The temperature of the cooling medium affects the elongation of the workpiece and thus the relative position of the workpiece to the line segments of the line array. The change in workpiece length is intentionally induced by controlling the workpiece temperature to reduce shape deviations associated with the movement of the floating bearing and the workpiece.

[0048] The wire saw used according to the invention comprises two or more wire guide rollers. The temperature adjustment of the fixed bearings of the wire guide rollers can be limited to two wire guide rollers, the wire array being tensioned between the two wire guide rollers, by means of which the workpiece is fed.

[0049] The workpiece is preferably made of a semiconductor material, such as silicon, in a polycrystalline or monocrystalline state. The outer perimeter of the workpiece's cross-section 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 invention is particularly suitable for producing circular semiconductor wafers made of monocrystalline silicon with a diameter of at least 200 mm, and particularly at least 300 mm.

[0050] For the production of semiconductor wafers from single-crystal silicon with a diameter of 300 mm, whether operating according to the first, second, or third embodiment or any variation thereof, the following matching operating parameters have proven particularly suitable:

[0051] Feed rate: 2.83 mm / min

[0052] Working fluid supply: 38 kg / min

[0053] Working fluid temperature: 31℃

[0054] Linear speed: 8m / s

[0055] Line consumption: 58.3km

[0056] Line tension: 34N

[0057] The details of the present invention are described below with reference to the accompanying drawings.

[0058] Brief description of the attached figures

[0059] Figure 1 The features of a wire saw that functions in the use of this invention are schematically shown.

[0060] Figure 2 More details of the wire saw are shown.

[0061] Figure 3 The path of the cut through the workpiece is shown, as well as the envisioned path represented by the reference trajectory.

[0062] Figure 4 The arrangement of slices between two sensors is shown to determine their shape deviations before the cutting operation.

[0063] Figure 5 This demonstrates the advantages gained when adding the magnitudes of WGTC and IPC.

[0064] Figure 6 The range is displayed, within which the magnitude of the movement is shown. It depends linearly on the variable that causes the shift.

[0065] Figure 7 This demonstrates the favorable division of the overall correction curves between WGTC and IPC.

[0066] Figure 8 The results show that combining WGTC and IPC can result in greater travel per unit time.

[0067] Figure 9 The diagram shows how the favorable division of the overall correction curves between WGTC and IPC suppresses amplitude overshoot, which would be observed if WGTC were used as the sole measurement.

[0068] Figures 10 to 12 The curve of the cut is displayed qualitatively.

[0069] List of reference numerals

[0070] Line guide roller

[0071] 2-line array

[0072] 3 sawing lines

[0073] 4 workpieces

[0074] 5 Fixed supports

[0075] 6 floating bearings

[0076] 7 racks

[0077] 8-sided layer

[0078] 9 channels

[0079] 10 directional arrows

[0080] 11 directional arrows

[0081] 12 Actuating Devices

[0082] 13-cut detector

[0083] 14 Data Processing Units

[0084] 15 Actuating Elements

[0085] 16 control units

[0086] 17 incisions

[0087] 18 Reference Trajectories

[0088] 19 Upper Sensor

[0089] 20 Lower Sensors

[0090] 21 slices

[0091] 22. Equipment for regulating the temperature of workpieces

[0092] Detailed description of exemplary embodiments according to the present invention

[0093] A wire saw suitable for performing the method according to the invention comprises a wire array 2 consisting of moving wire segments of a cutting wire 3, the wire array 2 being tensioned in a plane between two wire guide rollers 1. During the cutting operation, a workpiece 4 is fed through the wire array 2 in a feed direction perpendicular to the workpiece axis and perpendicular to the plane of the wire array 2 by means of an actuation device 12. During this operation, each of the wire guide rollers 1 and the workpiece 4, which are tensioned in the wire array 2, is moved in the axial direction according to direction arrows 10 and 11, depending on first and second correction curves. The first and second correction curves cancel out shape deviations determined before or during the cutting operation. A cut detector 13 is provided for observing the cut to determine the shape deviations during the cutting operation. Furthermore, a data processing unit 14 is provided for generating first, second, and (where applicable) third correction curves. The data processing unit 14 transmits a control signal to an actuation element 15, which, depending on the cutting depth, causes the workpiece 4 to move in the direction of the workpiece axis indicated by direction arrow 11 according to the second correction curve. Furthermore, a device 22 is provided for regulating the temperature of the workpiece 4. If the shape deviation is determined before each cutting operation, the data processing unit 14 transmits a second temperature curve to the device 22, which causes a change in workpiece length based on a third correction curve.

[0094] like Figure 2 As shown, a 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 wire guide roller 1 has a surface layer 8 with grooves in which the cutting line 3 travels. The fixed bearing 5 includes a channel 9 through which cooling fluid for regulating the temperature of the fixed bearing 5 passes. If the temperature of the fluid increases, the thermal expansion of the fixed bearing 5 causes the wire guide roller 1 to move axially in the direction of the floating bearing 6, and the floating bearing 6 to move outward relative to the frame 7 in the direction of the axis of the wire guide roller 1 indicated by the directional arrow 10. If the temperature of the cooling fluid decreases, it causes the wire guide roller 1 and the floating bearing 6 to move in opposite directions. The temperature of the cooling fluid is defined by a first temperature profile dependent on the cutting depth, which is related to a first correction profile. A control unit 16 connected to a heat exchanger and a pump ensures that the fluid passing through the fixed bearing 5 has the temperature required by the corresponding first temperature profile when a specific cutting depth is reached. A data processing unit 14 transmits the first temperature profile to the control unit 16, which causes the floating bearing to move according to the first correction profile.

[0095] Figure 3 The path through the cut 17 of workpiece 4 and the envisioned path represented by reference trajectory 18 are shown. The corresponding deviation of the line through the center of the cut from the reference trajectory corresponds to an overall correction curve, which can be divided into first, second, and (where applicable) third correction curves.

[0096] Figure 4 The arrangement of a slice between two sensors 19 and 20 is shown for determining its shape deviation prior to the cutting operation. Sensors 19 and 20 measure the distance FDi from the front side of the upper sensor 19 to the front side of the slice 21 and the distance BDi from the rear side of the slice 21 to the lower sensor 20 at specific positions i along the diameter of the slice 21 in the feed direction, according to a specific cutting depth. The slice shape curve is a line connecting the measured values ​​si calculated according to the rule si = D - (FDi - BDi), where D represents the distance between the sensors. The slice shape deviation is obtained by comparing the slice shape curve with a reference shape curve. The deviation from the reference shape curve, dependent on the cutting depth, corresponds to an overall correction curve, which is divided between WGTC and IPC in the form of first and second correction curves.

[0097] Figure 5 This demonstrates the advantages gained when adding the amplitudes of WGTC and IPC. If the entire calibration curve requires a stroke of amplitude A on the order of the dashed line, this stroke cannot be accomplished by WGTC or IPC alone, as the achievable stroke using the respective individual measurements is insufficient. Only the combination of WGTC and IPC makes this possible.

[0098] Figure 6 The results show that within a range B2 with a rest position B1, the magnitude of the movement A is linearly dependent on the variable causing the movement (input, I). Beyond this range, deviations from linear behavior occur, resulting in a Δ error. By combining WGTC and IPC, the range B2 of the overall system's linear response is increased.

[0099] Figure 7 This demonstrates a favorable division of the overall correction curves between WGTC and IPC, which includes compensating for low-frequency shape deviations using WGTC and the first correction curve, and compensating for high-frequency shape deviations using IPC and the second correction curve. For this purpose, a crossover is preferably used, which, with the aid of a low-pass filter (LP) and a high-pass filter (HP), allocates the low-frequency portion of the shape deviation to correction using WGTC and the high-frequency portion to correction using IPC.

[0100] Figure 8 The results show that by using a combination of WGTC and IPC, a larger total amplitude A2+A1 can be achieved per unit time Δ because the movement of the floating bearing and the workpiece is performed by two independent actuators. When using WGTC or IPC alone, only one amplitude of A1 and A2, respectively, is possible within that time unit.

[0101] Figure 9 The diagram shows how the favorable division of the overall correction curves between WGTC and IPC suppresses the overshoot of amplitude A over time t (right-hand plot), which would be observed if WGTC were used as the sole measurement (left-hand plot).

[0102] Figure 10 The path of the cut along the workpiece length WL is qualitatively shown. Such a path can be expected if the cutting operation is performed without using WGTC, IPC, and IC, and the operating parameters can then be optimized to obtain a particularly flat slice. Nevertheless, the slice is relatively non-uniform, and the form of this non-uniformity is particularly dependent on the location of the corresponding slice within the workpiece.

[0103] Figure 11 The qualitative analysis showed the corresponding cut paths that could be expected when performing a cutting operation without using WGTC, IPC, and IC. The operating parameters were then adjusted to be used in conjunction with WGTC and / or IPC and (if applicable) IC, thus deviating from the expected path. Figure 10 The procedure. Although these slices are less flat, the obvious dependence of the shape of each slice on its position in the workpiece is no longer observed.

[0104] Figure 12The study qualitatively demonstrates the corresponding cut paths that can be anticipated when performing a cutting operation according to the invention, i.e., performing WGTC with matching operating parameters, performing IPC with matching operating parameters, or performing both WGTC and IPC with matching operating parameters, preferably in combination with IC in each case. The resulting slices are remarkably flat regardless of the slice's position within the workpiece.

[0105] The above description of the illustrative embodiments should be understood as exemplary. This disclosure enables those skilled in the art to understand the invention and its related advantages, while also encompassing changes and modifications to the described structures and methods that are readily apparent to those skilled in the art.

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 formed by moving wire segments of a sawing wire 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. The method includes, during each cutting operation, in the presence of working fluid and hard material, feeding the corresponding workpiece through the wire array at a feed rate along a feed direction perpendicular to the workpiece axis and perpendicular to the plane of the wire array by means of the actuation device, wherein the hard material abrasively acts on the workpiece. This includes, during each cutting operation, cooling the workpiece with a cooling flow according to a first temperature profile. The system adjusts the temperature of the fixed bearing, feeds the workpiece through the linear array by axial movement of the floating bearing, the first temperature profile being dependent on the cutting depth and defining the temperature of the cooling fluid and related to a first correction profile being dependent on the cutting depth and defining the stroke of the floating bearing; determines the shape deviation during and / or before each cutting operation; and sets operating parameters dependent on the cutting depth, the operating parameters including at least one of feed rate, amount of working fluid supplied to the linear array per unit time, temperature of the working fluid, linear velocity, linear consumption per cutting operation, and linear tension.

2. 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 formed by moving wire segments of a sawing wire 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. The method includes, during each cutting operation, in the presence of working fluid and hard material, feeding the corresponding workpiece through the wire array at a feed rate along a feed direction perpendicular to the workpiece axis and perpendicular to the plane of the wire array by means of the actuation device, wherein the hard material abrasively acts on the workpiece. This includes feeding the workpiece through the wire array while simultaneously moving the workpiece along the workpiece axis by means of an actuation element according to a second correction curve, which specifies the workpiece's travel, wherein the second correction curve is opposite to the shape deviation; determining the shape deviation during and / or before each cutting operation; and setting operating parameters, depending on the cutting depth, including at least one of the following: feed rate, amount of working fluid supplied to the wire array per unit time, temperature of the working fluid, wire speed, wire consumption per cutting operation, and wire tension.

3. 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 formed by moving wire segments of a sawing wire 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. The method includes, during each cutting operation, in the presence of working fluid and hard material, feeding the corresponding workpiece through the wire array at a feed rate along a feed direction perpendicular to the workpiece axis and perpendicular to the plane of the wire array by means of the actuation device, wherein the hard material abrasively acts on the workpiece. This includes, during each cutting operation, feeding the workpiece through the wire array by adjusting the temperature of the fixed bearing with cooling fluid according to a first temperature profile, utilizing the simultaneous axial movement of the floating bearing, wherein the first temperature profile... The specifications depend on the cutting depth to define the temperature of the cooling fluid and are related to a first calibration curve, which depends on the cutting depth to define the stroke of the floating bearing; the workpiece is fed through the linear array while simultaneously moving the workpiece along its axis by means of an actuating element according to a second calibration curve, which defines the stroke of the workpiece, wherein the first and second calibration curves are opposite to the shape deviation; the shape deviation is determined during and / or before each cutting operation; and operating parameters are set depending on the cutting depth, including at least one of feed rate, amount of working fluid supplied to the linear array per unit time, temperature of the working fluid, linear velocity, linear consumption per cutting operation, and linear tension.

4. The method of any one of claims 1 to 3, comprising feeding the workpiece through the linear array during each cutting operation while controlling the temperature of the workpiece by wetting the workpiece with a cooling medium.

5. The method according to any one of claims 1 to 4, wherein the feed rate is not less than 2.6 mm / min and not greater than 4.25 mm / min.

6. The method according to any one of claims 1 to 4, wherein the amount of working fluid supplied to the linear array per unit time is not less than 15 kg / min and not more than 42 kg / min.

7. The method according to any one of claims 1 to 4, wherein the temperature of the working fluid is not less than 20°C and not greater than 34°C.

8. The method according to any one of claims 1 to 4, wherein the linear velocity is not less than 6 m / s and not greater than 14 m / s.

9. The method according to any one of claims 1 to 4, wherein the line consumption of each cutting operation is not less than 50 km and not more than 72 km.

10. The method according to any one of claims 1 to 4, wherein the line tension is not less than 25N and not greater than 35N.

11. The method of any one of claims 1 to 10, wherein the shape deviation is measured during each cutting operation by comparing the position of a line passing through the center of at least one cut with the position of a reference trajectory.

12. The method of any one of claims 1 to 11, wherein if the shape deviation determined prior to the corresponding cutting operation reaches or exceeds a defined threshold, maintenance measures are initiated instead of the corresponding cutting operation.

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