FIELD OF THE INVENTION

[0001] Embodiments of the present invention relate to a wire saw device, a method for operating such a wire saw device, and a respective computer program product. More particularly, they relate to a wire saw device and its operation for cutting or sawing hard materials such as blocks of silicon or quartz, e.g., for cutting silicon wafers, for a squarer, for a cropper or the like.

BACKGROUND OF THE INVENTION

[0002] Wire saw devices exist for cutting blocks or bricks, thin slices, e.g., semiconductor wafers, from a piece of hard material such as silicon. In such devices, a stretched wire is fed from a spool and is both guided and tensioned by wire guide cylinders. The wire that is used for sawing is generally provided with an abrasive material. As one option, the abrasive material can be provided as slurry. This may be done shortly before the wire touches the material to be cut. Thereby, the abrasive is carried to the cutting position by the wire for cutting the material. As another option, the abrasive can be provided on the wire with a coating. For example, diamond particles can be provided on a metal wire with a coating, wherein the diamond particles are imbedded in the coating of the wire. Thereby, the abrasive is firmly connected with the wire.

[0003] The stretched wire is both guided and tensioned by wire guides. These wire guides are generally covered with a layer of synthetic resin and are scored with grooves having very precise geometry and size. The wire is wound around the wire guides forms a web or wire web. During the sawing process, the wire is moved with considerable speed. The web generates a force perpendicular to the advance of a support beam or support holding the piece to be sawed. During sawing, the piece to be sawed is moved through the wire web wherein the speed of this movement determines the cutting speed and/or the effective cutting area that can be sawed within a given amount of time, e.g., within an hour.

[0004] Generally, there is a tendency to use thinner wires in order to reduce the thickness of the cut and, thereby, to decrease the material wasted. There is also a desire to use diamond wires. These thinner wires and diamond wires are generally more susceptible to damage and, under high strain, the wires may break more easily. Further, there is a desire to increase the cutting speed for improving the throughput of wire saw devices. The maximum speed for moving the piece through the web, and also the maximum effective cutting area within a given amount of time is limited by several factors including wire speed, hardness of the material to be sawed, disturbing influences, desired precision, and the like. When the speed is increased, the strain on the wire is generally increased as well. Hence, the above-mentioned problems of avoiding damage or breakage of the wire are even more critical at higher sawing speeds. Also, due to the higher cost of diamond wire, there is a tendency to a manner of operating a sawing machine which provides for constant wear of the wire in order to achieve an extended lifetime of the wire.

[0005] The advantages of diamond wire, such as a higher achievable sawing speed, are accompanied by aspects such as a lower resistance to breaking and a higher price per length. When employing diamond wire, measures can be taken to assure that the higher tendency to breaking does not lead to loss in production due to downtimes, whereas the higher price can be taken into account by measures that provide for a more economical handling of the wire supply.

SUMMARY

[0006] In view of the above, a method of operating a wire saw device according to independent claim 1, a computer program product according to independent claim 18, and a wire saw device according to independent claim 20 are provided. Further advantages, features, aspects and details are apparent from the dependent claims, the description and the drawings.

[0007] According to one embodiment, a method of operating a wire saw device is provided. The method includes a wire use cycle, which includes in the following order: a) accelerating the wire to a first moving speed in a first movement direction and moving the wire for a first distance of at least 50 m, b) stopping the wire movement, c) accelerating the wire to a second moving speed in a second movement direction opposite to the first movement direction and moving the wire for a second distance wherein one of the first distance and the second distance is 20 % or less greater than the other distance, d) stopping the wire movement. The method further includes repeating the complete wire use cycle until the objective of the sawing process is met. [0008] According to a further embodiment, a computer program product loadable into the memory of a computer is provided. It includes software code portions for performing a method including a wire use cycle, which includes in the following order: a) accelerating the wire to a first moving speed in a first movement direction and moving the wire for a first distance of at least 50 m, b) stopping the wire movement, c) accelerating the wire to a second moving speed in a second movement direction opposite to the first movement direction and moving the wire for a second distance wherein one of the first distance and the second distance is 20 % or less greater than the other distance, d) stopping the wire movement. The method further includes repeating the complete wire use cycle until the objective of the sawing process is met.

[0009] Embodiments are also directed at apparatuses for carrying out the disclosed methods and include apparatus parts for performing each described method step. These method steps may be performed by way of hardware components, a computer programmed by appropriate software, by any combination of the two or in any other manner. Furthermore, embodiments according to the invention are also directed at methods by which the described apparatus operates. It includes method steps for carrying out every function of the apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments. The accompanying drawings relate to embodiments of the invention and are described in the following:

FIG. 1 shows a perspective view of a wire saw device according to an embodiment

FIG. 2 shows a perspective view of a wire handling unit according to a further embodiment

FIG. 3 shows a schematic view of a method for operating a wire saw device according to an embodiment

FIG. 4 shows a schematic view of a method for operating a wire saw device according to a further embodiment FIG. 5 shows a schematic view of a method for operating a wire saw device according to another embodiment

DETAILED DESCRIPTION OF THE INVENTION

[0011] Reference will now be made in detail to the various embodiments of the invention, one or more examples of which are illustrated in the figures. Within the following description of the drawings, the same reference numbers refer to same components. Generally, only the differences with respect to individual embodiments are described. Each example is provided by way of explanation of the invention and is not meant as a limitation of the invention. Further, features illustrated or described as part of one embodiment can be used on or in conjunction with other embodiments to yield yet a further embodiment. It is intended that the description includes such modifications and variations.

[0012] Furthermore, in the following description, a control unit may be understood as a device electronically controlling substantially all functions of a wire saw device, e.g., a cropper, a squarer, or a wafer cutting wire saw. Typically, the control unit is connected to sensors in order to monitor parameters of the machine operation and the sawing process. It is also connected to actuators and devices to steer the electric motors which move the wire. It also includes devices for interaction with an individual in order to receive commands and to report the status of the sawing process. A control unit may also be connected in some embodiments to a computer network to be controlled directly or remotely by an individual or an automated system such as a computer.

[0013] According to embodiments described herein, the methods of operating a wire saw device can be conducted by means of computer programs, software, computer software products and the interrelated controllers, which can typically have a CPU, a memory, a user interface, and input and output means being in communication with the corresponding components of the wire saw device. These components can be one or more of the components: motors, wire break detection units, wire tracking devices, and the like, which will be described in more detail below.

[0014] Furthermore, in the following description, a wire management unit will be understood as a device handling the supply of wire to a cutting area or working area of a wire saw device, such as a cropper, a squarer, or a wafer cutting wire saw. Typically, the wire saw includes a wire guide for transporting and guiding the wire in a wire moving direction while the wire management unit provides control of the wire tension. Furthermore, the wire provided by the wire management unit forms a wire web in the cutting area. Often, a wire web will be considered as the web formed by a single wire management unit. It should be understood that a wire web may contain more than one working area which is defined as an area in which a sawing process is performed. Thus, according to some embodiments described herein, a wire web can have multiple areas that are formed by a wire from different wire management units.

[0015] For modern wire saw devices like croppers, squarers, or wire saws, there is the desire to cut the hard material such as semiconductor material, for example, silicon, quartz, or the like at high speed. The wire speed, that is the speed of the wire moving through the wire saw device, the wire management unit and the material to be sawed, respectively, can be, for example, 10 m/s or higher. Typically, the wire speed can be in a range of 15 to 20 m/s. However, higher wire speeds of 25 m/s or 30 m/s can also be desirable and could be realized under certain conditions.

[0016] For unwinding the wire at the desired wire speed, the spool rotates with a rotation speed of up to several thousands rotations per minute. For example, 1000 to 2000 rpm can be provided for unwinding the wire.

[0017] The described embodiments are particularly useful wires with a coating, e.g., a diamond coating, are used. Accordingly, in embodiments, which can be combined with other embodiments described herein, such wires may typically have a diameter of about 300 μιη to about 400 μιη, e.g., 310 μιη to 340 μιη. For those wires, a twisting of the wire might increase the risk of breaking of the wire or of damaging the coating, so that a twist-free operation is advantageous. By using diamond wire, the throughput may be increased by a factor of 2 or even more. In comparison to conventional steel wire, the increasingly used diamond wire has some advantages such as higher achievable sawing speed. The speed with which the material to be sawed is moved relatively to the moving wire may be referred to as the material feed rate. The material feed rate in the embodiments described herein may be in the range of 2 μΓη/s to 12 μητ/s, typically about 5 μητ/s to 7 μητ/s.

[0018] The wording "first/second" and "forward/backward" as a description of the distances, directions and movements herein is only a matter of nomenclature for the purpose of distinguishing the directions and is not intended to specify or delimit specific directions with respect to certain parts of the machine or the order of process steps. The skilled person knows that these terms may be interchangeable depending on the specific setup of an apparatus or the respective method of operation.

[0019] FIG. 1 shows an embodiment of a wire saw device 100. As can be seen from the pattern of the wire 10 forming the wire web in the wire web compartment 110, the example shown illustrates a squarer, intended to saw an object to be sawed into blocks of a square shape. In FIG. 1, the object to be sawed should be imagined to move in a direction perpendicular to the plane of projection during sawing. The housing of the wire saw device is separated into different areas as indicated by the dotted line. The wire web is formed in the wire web compartment 110. Further, a housing portion 111, which houses further components and equipment of the wire saw device 100 is provided. For example, a wire handling device compartment 112 and an electrical cabinet 114 can be provided. Within the further housing portion 111, tanks 120 and 124, as well as respective pumps 121 and 125, can also be provided. Further, the device may include an electronic control unit for controlling the operation of the device, which is not shown.

[0020] According to some embodiments, which can be combined with other embodiments described herein, the first tank 120 can be used for unused cooling fluid, e.g., in the case where the wire saw device is operated with diamond wire, or can be used e.g., for unused (fresh) slurry, in the case where the wire saw device 100 is operated with a wire requiring additional abrasive. The pump 121 pumps the cooling fluid (or slurry, respectively) towards the desired position in the cutting area. This is indicated in FIG. 1 by conduit 122. The used cooling fluid (or slurry) may flow back through conduit 126 and is pumped by pump 125 into the second tank 124. In those cases where cooling fluid or slurry is used, a portion of the used consumable fluid can be re-used if it is reinserted into the tank 120. Thus, according to different embodiments, only a portion of the consumable fluid, all of the consumable fluid or none of the consumable fluid may be reused and, thus, be reinserted in tank 120. As one example, an additional valve might be provided in conduit 126 for selectively choosing the tank into which the used fluid is pumped. According to yet another example, a fluid connection between the tanks 124 and 120 can be provided in order to reinsert a portion of the used fluid into tank 120. According to different embodiments, as already described above, the consumable fluid can be cooling fluid or slurry. Generally, if slurry is used, the slurry also takes over the function of cooling the position at which the wire cuts the material.

[0021] In the wire handling compartment 112, two handling sections for delivering the wire 10 to the cutting area and receiving the wire from the cutting area, respectively, are provided. According to some embodiments, which can be combined with other embodiments described herein, the wire is provided on a spool 132 rotating around the spool axes 132a. The wire is guided over a plurality of rollers 134 into the wire web compartment 110. Further pulleys 134 and 136 guide the wire 10 in the cutting area to form the wire web. Thereby, further pulleys (not shown) are required to guide the wire 10 from one pulley 136 to a further pulley 136. In order to avoid unnecessary complexity, these further pulleys are not shown in figure 1. After cutting, the wire is guided by a further pulley 134 towards the wire handling compartment 112 and is therein provided over pulleys 134 on the spool 130 rotating around the spool axes 130a. The spools 132 and 130 are driven by motors, preferably electrical motors, which are not shown.

[0022] According to yet further embodiments, which can be combined with other embodiments described herein, the wire handling system can be adapted for bi-directional use, such that in one direction the wire is fed from spool 132 to spool 130 and in a further direction, the wire is fed from spool 130 to spool 132. Thereby, according to typical implementations, the two units corresponding to spools 130 and 132 include similar components such as pulleys or the like to have a corresponding wire handling in both sawing directions. The bi-directional use of the wire saw device may be of particular interest if diamond wire is used.

[0023] Typically, the wire is guided from the wire handling compartment to the wire cutting area and back with a wire speed of 10 m/s or higher, typically in a range of 15 to 20 m/s or even up to 25 m/s or 30 m/s. The material to be cut is positioned on the support 140. The support 140 and the wire web defined by pulleys 136 can be moved relative to each other such that cutting of the material can be conducted. According to one embodiment, the pulleys 136 maintain in a fixed position and the support 114 moves the material to be cut through the wire web while the wire is at a speed of about 10 m/s or higher. For easier understanding, this movement of the support 140 would in figure 1 be perpendicular to the plane of the drawing. According to another embodiment, the pulleys 136 and, thus, the web generated by wire 10 are moved relative to the support 140 to cut the wire through the material. According to yet further embodiments, both the support 140 and the wire web can be both moved with respect to each other.

[0024] As indicated by the dotted lines in figure 1, the electrical cabinet 114 may serve to control the operation of the different components. For example, movement of the support 140, operation of the pumps 121 and 125, rotation of the spools 130 and 132 can be controlled. Further, additionally or optionally, the filling level of the tanks 120 and 124 can be measured and respective signals can be fed to the control unit. According to yet further embodiments, other control signals and monitoring signals can be fed to and from the electrical cabinet 114. For example, signals from the motors driving the spools, from a wire tensioner, to a wire tensioner, pressure signals for feeding the consumable fluids like slurry or cooling fluid, or a wire break detection signal can be fed to and from the electrical cabinet. Even though an electrical cabinet 114 integrated in a wire saw device 100 is shown in figure 1, it is apparent to a person skilled in the art that an electrical cabinet or a control unit in general can be provided at a different location in the wire saw device, e.g., also external of the wire device, and corresponding control signals from and to the control unit can be provided accordingly.

[0025] FIG. 2 shows a perspective view of a wire management unit according to some embodiments, which can be combined with other embodiments described herein. The embodiment of FIG. 2 includes a spool 312, mounted on spool shaft 310, and the pulleys 320, 330 and 340 are arranged to guide the wire, particularly with a wire tracking system. Examples of a wire tracking system are described in European patent application No. 09153051.9, entitled "Wire saw device and method for operating same" filed February 17, 2009, which is incorporated herein by reference to the extent the applications are not inconsistent with this disclosure. Additionally, a recess 316 can be seen. The recess 316 is provided in the main frame portion. The recess is dimensioned and arranged for accommodating at least partially the first pulley 320. This recess allows the first pulley 320 and, hence, the spool 312 to be arranged closer to the main frame portion while still allowing the first pulley 320 motion track to cover most or all of the wire carrying area of spool 312. Further, the pulley carrying unit 324 is provided as a retractable or telescopic bar. The retractable or telescopic bar is longitudinally movable along a bar axis parallel to the spool axis. The bar is longitudinally movably mounted to a wall portion of the main frame portion, e.g., of a wall portion of the recess 316.

[0026] Further, in the embodiment of FIG. 2, the main frame portion includes a mounting member 314, to which the second and third pulley 330, 340 are mounted. The mounting member 314, being part of the main frame portion, is rigidly connected to the chassis of the wire saw device. As shown in Fig. 2, the first and secondary first pulleys 320/320b are rotatably mounted to a first and secondary pulley carrying unit 3247324b for rotation around a first and secondary first pulley axis, the first and secondary pulley carrying unit being longitudinally movable along a secondary pulley motion track.

[0027] In light of the above, according to yet further embodiments, which can be combined with any of the other embodiments described herein, the tracking motion at the spool side, at which the wire is wound onto the spool is controlled using the respective pulley carrying unit such that the wire is wound on the spool in a regular pattern. This allows the wire to have an improved alignment with the pulley controlling the winding pitch and thereby reduces vibrations, accelerated tire wire and wire breakage.

[0028] Further, a fourth pulley 350 is shown. The fourth pulley 350 receives the wire from the third pulley and redirects the wire by a fourth redirection angle. The fourth pulley 350 is rotatably mounted to the frame for rotation around a fourth pulley axis. Here, the fourth redirection angle is about 90°. In other embodiments, the fourth redirection angle may be from 60° to 120°. The fourth pulley axis is essentially parallel to the spool axis. Further, the fourth pulley axis is essentially perpendicular to the first pulley axis, the second pulley axis, and the third pulley axis. In other embodiments, the fourth pulley axis may be essentially parallel to at least one of these axes.

[0029] The embodiment of FIG. 2 further includes a wire tensioner for controlling the tension of the wire. The wire tensioner includes a fifth pulley 360 rotatably mounted to the frame for rotation around a fifth pulley axis 362 and a sixth pulley 370 rotatably mounted to a movable element 374 for rotation around a sixth pulley axis 372. The movable element 374 is movably mounted on the main frame portion. The movement of the movable element 374 may be controlled by a motor, or the movable element 374 may be pre-biased, e.g., by a spring, for controlling the wire tension.

[0030] According to an embodiment schematically depicted in FIG. 3, during a sawing process, the wire is accelerated in a first (or forward) direction to a first moving speed, and then moved for a predefined time or distance, or substantially the entire length provided on a supply spool. In the next step, the wire movement is stopped, and the wire is accelerated in the opposite, i.e., second or backward direction to a second moving speed, which is in some embodiments identical to the first moving speed. After moving it in this direction for a time and length which are substantially identical or similar to the respective ones at forward motion, it is stopped again. The process is then repeated from the beginning, i.e., from the acceleration in the forward direction. Between the stops and the changes of direction, the wire runs in one direction for a predefined time and thus a certain distance or length, which may be 50 m or greater, e.g., from 0.05 to 20 kilometers.

[0031] The objective of the sawing process is regarded to be met in the embodiments herein, when the wire or the wire web has passed the complete cross section of the object to be sawed and the object is separated into parts or a slice is completely sawed off the object. According to the embodiment, the process above is then continued until the wire has reached the end of the second moving direction. In this manner, it may be assured that the next sawing process starts using a section of the wire that was already, or at least partly, used for sawing in the previous sawing process, and the wire may be used for an amount of time which is close to its maximum usable lifetime. If the wire would stop at the end of the forward motion when the objective is met, as is conventional, the next sawing process with a new sawing object would start employing an unused section of the wire for sawing. The wire section used in the previous process would then not be used until its maximum usable lifetime.

[0032] At the time when the wire is stopped and then accelerated in the opposite direction, the passage of the wire which is between the spools at this moment is subject to increased stress. During operation of the wire saw device, the wire may run up to hundreds or even thousand times in each direction, which means that the wire is also stopped and accelerated hundreds or even thousands times. Conventionally, the reversal process is carried out at the same position of the wire each time, as the distance the wire is covering in each direction during the forward and backward movements is identical. This may lead to the fact that the particular passage is subject of particular stress and thus, develops a tendency for premature breakage.

[0033] In order to avoid this, in an embodiment the distances covered during the forward and backward movements may be chosen to be different. As an example, a first or forward distance is 0.5 m to 30 m greater than the second or backward distance. More preferable, the first distance is 2 m to 10 m greater than the second distance. Expressed in relative terms, one of the distances, e.g., the first distance, may be 0.05 % to 5 % greater than the distance in the other direction. In absolute terms, one of the distances, e.g., the first distance, may be from 0,1 km to 20 km in length, more preferably from 0,5 km to 10 km.

[0034] As a nonlimiting example, a forward distance which the wire covers during its movement is 1000 m or 1 km. After stopping and reversing the direction, the wire is moved back in the second direction for 994 m before being stopped again. Hence, this stopping position is 6 m away from the previous position in this example. The wire is then again moved for 1000 m in the first direction, stopped and moved 994 m backwards. Now, the stopping position is again 6 m advanced from the previous stopping position, which adds to 12 m. In this manner, it may be assured that the wire is not subject to enhanced stress at a particular position or passage on its length for a plurality of times, but that the stopping and acceleration stress is distributed on consecutive different parts of the wire. With every forward and backward cycle, the stopping and reversal positions at both ends of the movement advance for 6 m in this example, adding up with each cycle. Thus, when the wire has run forth and back a hundred times, the 1 km long segment of the wire used for sawing is relocated for 600 meters with respect to the segment used in the beginning of the process. This is obviously only possible if the entire length of the wire is long enough to provide enough extra length for the described relocation or shift of the sawing segment. In the embodiments described herein, the entire length of the wire may be from 1 km to 30 km, preferably from 5 km to 20 km.

[0035] Conventionally, after a sawing process was interrupted or temporarily halted, e.g., in case of failure, malfunction or manual interaction, the wire starts again in a specified direction predefined in the machine's control unit or software. The halt may be due to an interaction of an individual with the control unit or may automatically be triggered by the control unit, e.g., in the case of a malfunction of the device, or in any other manner.

[0036] If this would happen in the above embodiment, there may be some undesirable consequences. In an example, the machine is in backward motion and the wire has just moved 20 m after the stop and reversal of direction. The machine stops due to an unplanned event, and after, e.g., a repair then starts again in the predefined forward motion. In this case, the previous entire wire length of the forward motion minus 20 m would be wasted - as the machine would now perform a complete forward cycle with, e.g., 1000 m covered distance until the next reverse, instead of incrementally advancing the stopping positions as described above. With the costs of conventional steel wire this was not much of an issue, whereas it is undesirable when using the more expensive diamond wire, as it is desirable to use every segment of the entire wire length with an even wear in order to allow for optimum lifetime.

[0037] According to an embodiment schematically depicted in FIG. 4, this can be met by providing that the wire starts again after a halt in the same direction in that it was moving previously to the halt. In the figure, the unplanned halt is depicted between a) and b). This is a non-limiting example; the halt may, of course also happen between c) and d). Thereby, the continuing movement would be conducted in the second direction. [0038] When using diamond wire, care should be taken in order not to exceed too much force on the wire to avoid wire break due to the higher susceptibility to breaking. In the above described sawing process, wherein the wire is accelerated, moved for a certain time and distance, stopped, and accelerated and moved in the opposite direction, a problem may occur which leads to a higher tendency to break. During the frequent stops of the wire, the sawing process is shortly interrupted. Yet conventionally, the support supporting the object to be sawed, e.g., a silicon ingot, is moving with a relatively slow and constant speed of 2 μιη/s to 12 μητ/s, typically about 5 μητ/s to 7 μητ/s. During the period of standstill of the wire, before it is accelerated into the other direction, this movement may conventionally continue. Due to the stop of the sawing process, but the continuous movement of the object, there may be the tendency of wire breakage. This is even more relevant as diamond wire is coated with small particles of diamond, which, under certain conditions, may tend to get stuck or jam with the object to be sawed. This is particularly relevant in the case that the wire is stopped but the object to be sawed moves on.

[0039] According to an embodiment depicted in FIG. 5, the support supporting the object to be sawed is stopped at substantially the same time that the wire is stopped before being accelerated in the opposite direction. According to yet further embodiments, which can be combined with other embodiments described herein, the support may be stopped shortly before the wire movement is stopped. Hence, the above-mentioned problem of the possible jamming of the diamond wire with the object is overcome, and a source for potential wire breakage eliminated. Thereby, the acceleration profile and deceleration profile are defined as the timely evolution of the speed of the wire respectively the support, i.e., the physical acceleration measured in m/s . Herein, two acceleration profiles are regarded as being identical in this respect if the graphical representation of the first deviation of the acceleration has substantially the same shape for both movements. In an embodiment, the deceleration profile of the support during the stopping process is substantially identical to the deceleration profile of the wire, and optionally the acceleration profile of the support is substantially identical to the acceleration profile of the wire as well.

[0040] In an embodiment, the control unit stops the movement of the support supporting the object to be sawed such that the support is at a standstill before the wire is at a standstill, e.g., the support is at a standstill 0.05 to 5 seconds before the wire is at a standstill. This may provide a maximum safety limit with respect to possible wire breakage during the wire stopping and reversal process. This may also be applied when the wire stops due to an unscheduled event such as an alarm, etc., as described above.

[0041] Typically, a plurality of motors are used in a wire saw device in order to move the wire, i.e., to accelerate it, move it and stop it as described hereinbefore. At least one motor is driving the supply spool for the wire and one motor is driving the take up spool. Further motors may be employed to more precisely carry out the wire handling process. Typically, according to embodiments described herein, motors are used for rotating the wire guides, e.g., the four wire guides, and thereby move the wire in the web region. Conventionally, one of the motors is configured to act as a leading motor, that is, during acceleration of the wire this motor starts to pull, and the other motors start pulling depending on the torque of the first motor. Yet this may lead to increased tension in the portion of the wire which is driven by the first motor, which may lead to an increased tendency to wire breakage when using diamond wire. In an embodiment, this is met by a method of steering the torque of the motors such that each motor exerts a force on the wire from the beginning of the acceleration. Preferably, the forces exerted by the motors on the respective parts of the wire are substantially identical. Optionally, the torque of one motor may be greater than the torque of the other motors during acceleration, and thus the exerted force on the wire by this motor may also be greater.

[0042] According to yet further embodiments, which can be combined with other embodiments, described herein, the methods and the respective computer program allows a further additional or alternative implementation that essentially the entire spool length can be used in back and forth mode in order to use long back and forth distances, i.e., long first and second distances as described herein.

[0043] For some embodiments, which can be combined with other embodiments described herein, a wire saw device and/or a pulley for a wire saw device can be adapted for diamond wire, and methods of operating can be performed with diamond wire. This can, for example, be done by adapting the groove structure with an appropriate pitch of grooves, a different depth of grooves and/or a different shape of grooves. By using diamond wire, typically the cutting speed can be increased, e.g., by a factor of 2, the energy consumption of the wire saw device can be reduced and, further, as yet another example, the costs of squaring silicon ingots or wafering silicon can be significantly reduced. [0044] In the following, some general aspects of the embodiments described herein will be summarized. Each of these general aspects can be combined with any other general aspect, within any embodiment described herein, to generate yet another embodiment.

[0045] According to one embodiment, a method of operating a wire saw device is provided. The method includes a wire use cycle, which includes in the following order: a) accelerating the wire to a first moving speed in a first movement direction and moving the wire for a first distance of at least 20 m or at least 50m, b) stopping the wire movement, c) accelerating the wire to a second moving speed in a second movement direction opposite to the first movement direction and moving the wire for a second distance wherein one of the first distance and the second distance is 20 % or less greater than the other distance, d) stopping the wire movement. The method further includes repeating the complete wire use cycle until the objective of the sawing process is met. Here, one distance being greater than the other distance excludes the case that both distances are equal. According to embodiments which can be combined with any other embodiment described herein, the one distance is by at least 10 cm greater, or by at least 50 cm greater, or even by at least 5 m greater than the other distance.

[0046] According to one optional aspect, which can be provided for a method of operating a wire saw device, one of the first distance and the second distance can be from 0.5 to 30 meters greater than the other distance, more typically from 2 to 10 meters greater than the other distance. Accordingly, as a further alternative or optional aspect, one of the first distance and the second distance can be from 0.05 % to 5 % greater than the other distance, and the first distance can typically be from 0.05 to 20 kilometers, more typically from 0.5 to 10 kilometers.

[0047] Accordingly, as a further alternative or optional, after the wire has been stopped during the sawing process due to an unplanned event, the wire can start again in the same direction in that it was moving previously to the event leading to the stop, and the event can be chosen from the group consisting of a manual interaction, a stop triggered by the control unit of the device, and a stop triggered from a remote location.

[0048] Accordingly, as a further alternative or optional, a) can further comprise accelerating a support supporting the object to be sawed to a predefined speed, and b) can further comprise stopping the movement of the support, and c) can further comprise accelerating the support to a predefined speed, and d) can further comprise stopping the movement of the support, and stopping the movement of the support may be carried out substantially synchronously with stopping the movement of the wire, and the stopping profile of the support can substantially be identical to the stopping profile of the wire. As an alternative or optional, the support can stop before the wire is at standstill and/or the support can be at standstill 0.01 seconds to 5 seconds before the wire is at standstill.

[0049] According to yet further optional aspects, which can be combined with embodiments described herein, a plurality of motors can be used for moving the wire, and the motors can each exert a force on the wire during acceleration of the wire, wherein the torque of the motors may be substantially identical during acceleration, or optionally, during acceleration, the torque of one motor can be greater than the torque of the other motors.

[0050] According to a further embodiment, a computer program product loadable into the memory of a computer is provided. It includes software code portions for performing a method including a wire use cycle, which includes in the following order: a) accelerating the wire to a first moving speed in a first movement direction and moving the wire for a first distance of at least 50 m, b) stopping the wire movement, c) accelerating the wire to a second moving speed in a second movement direction opposite to the first movement direction and moving the wire for a second distance wherein one of the first distance and the second distance is 20 % or less greater than the other distance, d) stopping the wire movement. The method further includes repeating the complete wire use cycle until the objective of the sawing process is met. According to yet a further alternative or additional implementation, the steps can be performed in an automated system.

[0051] While the foregoing is directed to embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.