Cylindrical grinding machine and cylindrical grinding method

Abstract

To provide a cylinder grinder and a cylinder grinding method capable of performing a grinding process with stable quality by preventing position shifting or breaking of a crystal rod efficiently at low cost in traverse grinding of the crystal rod.SOLUTION: This cylinder grinder comprises: a discrimination device capable of supporting a crystal rod irrespective of the presence of a conical cone and a tail at both ends of the crystal rod and automatically discriminating the presence of the cone or the like; and a controller in which a setting value is set for each presence of the cone or the like for a force of holding the crystal rod between a pair of support units and a maximum grinding margin per operation of a grinding unit in traverse grinding. A grinding receipt having a holding force corresponding to the presence of he cone or the like automatically discriminated by the discrimination device and a setting value of a maximum grinding margin per operation is automatically selected by the controller, and the traverse grinding can be performed on the basis of the grinding receipt.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a cylindrical grinding machine and a cylindrical grinding method having a support unit that sandwiches a crystal bar (such as a silicon single crystal ingot) in the axial direction between a main shaft and a sub-shaft to which a support device is attached and supports (fixes) it so that it can rotate around the axis, and a grinding unit that traverses and grinds the outer circumference of the crystal bar while moving along the axial direction of the crystal bar.

Background Art

[0002] In recent years, due to the improvement of the performance and the reduction of the manufacturing cost of semiconductor devices, the diameter of wafers used in semiconductor device manufacturing has been increasing. The wafers used in semiconductor device manufacturing are produced by preparing a crystal bar having conical cone portions and tail portions before and after a cylindrical straight body portion by the Czochralski method or the like, and after cylindrically grinding the outer circumference of the crystal bar with a cylindrical grinding machine, slicing it perpendicularly to the axial direction to cut it into a plate shape, and manufacturing it through a polishing process. In recent years, with the increase in the number of wafers obtained from one crystal bar and the increase in the diameter of wafers, the produced crystal bars have also become longer, larger in diameter, and heavier.

[0003] When such a crystal bar is cylindrically ground, a cylindrical grinding machine <101> as shown in FIG. 5 is used. A general conventional cylindrical grinding machine <101> is composed of a transfer unit <116> for transferring the crystal bar <7> inside and outside the machine, a pair of support units <104> for holding the crystal bar <7>, and a grinding unit <105> for traversing and grinding the outer circumference of the crystal bar <7>. The pair of support units <104> have a main shaft <103a> and a sub-shaft <103b> to which support devices are attached to the respective tips, and can sandwich the crystal bar <7> in the axial direction and make it rotatable around the axis.

[0004] Here, an example of the form of the crystal bar <7> (7a to 7d) to be cylindrically ground will be described using FIGS. 6 to 9. FIG. 6 shows a crystal bar <7a> of a dislocation-free crystal, and the shapes of the cone portions <9> and the tail portions <10> at both ends (both sides of the straight body portion <8>) of the crystal bar <7a> are conical. Furthermore, in the case of the crystal rod 7b shown in Figure 7, which has developed dislocations during growth, there is a problem that if this crystal rod 7b is fixed by clamping it axially with the support devices 102a and 102b at the tips of the main axis 103a and sub-axis 103b in Figure 5, the dislocation portion D collapses, and it cannot be fixed properly. Therefore, as a pretreatment, the dislocation portion D is cut perpendicular to the crystal axis direction using a band saw or the like. Figure 8 shows the crystal rod 7c in the form in which the dislocation portion D has been cut in this way. Furthermore, for some reason, a cylindrical crystal rod 7d, as shown in Figure 9, which has been cut from a dislocation-free crystal rod 7a or a dislocation-containing crystal rod 7b, may be traverse-ground using a cylindrical grinding machine.

[0005] In the following, for convenience, the conical cone section may be referred to as "with cone 9a," the conical tail section as "with tail 10a," the flat surface obtained by vertically (flatly) cutting the cone section as "without cone 9b," and the flat surface obtained by vertically (flatly) cutting the tail section as "without tail 10b."

[0006] In the preparation process (loading process) for traverse grinding using a cylindrical grinding machine, the crystal rod is transported into the cylindrical grinding machine by a transport unit, and the crystal rod is clamped in the direction of the crystal axis by a support unit. Incidentally, the support device consists of a fixed support part 114 having a conical hole as shown in Figures 10 and 11, as in Patent Document 1, and a floating support part 115 that supports the vertically cut end face. The cone-equipped 9a and tail-equipped 10a are supported by a fixed support portion 114 provided with a conical hole, as shown in Figure 10. On the other hand, the cone-less 9b and tail-less 10b are supported by the floating support portion 115 at the vertically cut surface, as shown in Figure 11. The floating support portion 115 has a slightly movable structure. When cutting perpendicular to the crystal axis as a pretreatment, it is difficult to cut precisely perpendicularly due to the irregularities on the outer circumference of the cylinder, but even crystal rods with such cut surfaces can be held by the movable floating support portion 115 as shown in Figure 11. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 11-207505 [Overview of the project] [Problems that the invention aims to solve]

[0008] In the preparation process (loading process), the crystal rods 7, which have been transported and supported in the cylindrical grinding machine 101, undergo diameter measurement and other procedures before cylindrical grinding. Figure 12 shows the process of cylindrical grinding of a crystal rod with a cone (tail). Figure 13 shows the case of a crystal rod without a cone (tail). The outer circumference of the crystal rod 7 is cylindrically ground by the grinding wheel 106 of the grinding unit 105. If the amount of material removed SR when grinding the crystal rod to the finished diameter (final target diameter) exceeds the maximum amount of material removed SRm per pass, the cylindrical grinding is performed in multiple passes. During cylindrical grinding, an external force EF acts in the opposite direction to the grinding wheel 106 due to the grinding load on the grinding wheel 106. In the case of the cone-less 9b and tail-less 10b shown in Figure 13, if the external force EF (or grinding load, maximum cutting allowance SRm per pass) becomes greater than the frictional force (also called support friction) generated between the vertically cut surface and the floating support part 115, the crystal rod 7 will move during cylindrical grinding (misalignment of the crystal rod), resulting in poor grinding of the cylindrical grinding surface and poor diameter accuracy. On the other hand, in the case of the cone-included 9a and tail-included 10a shown in Figure 12, the cone part 9 and tail part 10 are held in a state where they fit inside the conical hole, so the crystal rod 7 does not move during cylindrical grinding.

[0009] The frictional force that clamps and supports the crystal rod 7 in the direction of the crystal axis is obtained by moving a pair of support units 104 in the direction of the crystal axis and applying a clamping force CF (also called a pressing force) to the crystal rod 7. Generally, the clamping force is increased when there is no cone (tail) to prevent the crystal rod 7 from moving during cylindrical grinding. However, if the same clamping force is used to support the cone (tail) portion, the cone portion 9 (tail portion 10) may break near the contact point with the conical hole, resulting in poor grinding of the cylindrical grinding surface or inaccuracies in diameter. Also, depending on the conical shape of the cone portion 9 and tail portion 10, the tail side, which is generally thinner, was more prone to breaking.

[0010] One possible approach is to prepare separate cylindrical grinding machines with and without cones (tails), but this is not practical because an imbalance between the number of crystal rods to be processed and the number of machines would reduce the machine utilization rate. Another method involves manually changing the grinding recipe to the optimal setting each time, depending on whether a cone (tail) is present or not. However, this requires operator intervention each time, increasing labor costs.

[0011] The present invention was made to solve the above problems, and aims to provide a cylindrical grinding machine and cylindrical grinding method that can perform traverse grinding of crystal rods efficiently, at low cost, and with stable quality by preventing misalignment and breakage of the crystal rods. [Means for solving the problem]

[0012] To achieve the above objective, the present invention provides a cylindrical grinding machine comprising: a pair of support units that axially clamp a crystal rod and make it rotatable around an axis by a main shaft and a sub-shaft, each of which has a support device attached to the tip of the end of the crystal rod; and a grinding unit that traverse grinds the outer circumference of the crystal rod while moving along the axial direction of the crystal rod supported by the pair of support units, The support device has a concave first support portion capable of supporting a conical crystal end and a second support portion capable of supporting a flat crystal end, and is capable of supporting the crystal rod regardless of whether or not there are conical cone portions and tail portions at both ends of the crystal rod. Furthermore, a discriminator capable of automatically determining the presence or absence of the cone portion and tail portion, The system has a controller in which set values ​​are registered for the clamping force applied by the pair of support units to the crystal rod during the traverse grinding process, and for the maximum amount of material removed per pass by the grinding unit, separately for the presence or absence of the cone portion and the tail portion. The present invention provides a cylindrical grinding machine in which a grinding recipe having the gripping force corresponding to the presence or absence of the cone portion and tail portion, which are automatically determined by the discriminator, and the set value of the maximum grinding allowance per pass is automatically selected by the controller, and traverse grinding can be automatically performed based on the grinding recipe.

[0013] The cylindrical grinding machine of the present invention supports and fixes the crystal rod with a clamping force of a registered set value corresponding to the presence or absence of a cone portion and a tail portion (hereinafter also referred to as the cone portion, etc.), and is capable of traverse grinding with a maximum cutting depth per pass of the same set value. Appropriate set values ​​can be set for the clamping force and the maximum cutting depth per pass depending on the presence or absence of the cone portion, etc. This prevents the cone portion, etc. from breaking due to excessive clamping force, and prevents the crystal rod from shifting position due to the maximum cutting depth per pass being too large compared to the support friction force when the cone portion, etc. is absent. As a result, grinding can be performed with stable quality without grinding defects or diameter accuracy defects on the cylindrical grinding surface.

[0014] Furthermore, because the detection of the presence or absence of cone sections, selection of grinding recipes, and traverse grinding are all automated, there is no need for an operator, resulting in low-cost grinding. Furthermore, since it supports both patterns with and without the cone section, grinding can be performed efficiently, and the decrease in operating rate that occurs with conventional machines that are dedicated to either having or not having the cone section can be prevented.

[0015] The present invention also relates to a method for cylindrical grinding a crystal rod, using a cylindrical grinding machine having a pair of support units that axially clamp the crystal rod and make it rotatable around an axis by a main shaft and a sub-shaft, each of which has a support device attached to the tip of the crystal rod's end, and a grinding unit that traverse grinds the outer circumference of the crystal rod while moving along the axial direction of the crystal rod supported by the pair of support units, The support device has a concave first support portion capable of supporting a conical crystal end and a second support portion capable of supporting a flat crystal end, and is capable of supporting the crystal rod regardless of whether or not there are conical cone portions and tail portions at both ends of the crystal rod. Furthermore, a discriminator capable of automatically determining the presence or absence of the cone portion and tail portion, A controller is provided in which set values ​​are registered for the clamping force of the pair of support units that hold the crystal rod in the traverse grinding, and for the maximum amount of material removed per pass by the grinding unit, separately for the presence or absence of the cone portion and the tail portion. The present invention provides a cylindrical grinding method characterized by the following: when the crystal rod is clamped and fixed by the pair of support units, the presence or absence of the cone portion and tail portion of the crystal rod is automatically determined by the discriminator, the clamping force corresponding to the presence or absence of the cone portion and tail portion determined by the automatic discriminator and the setting value of the maximum cutting allowance per pass are automatically selected by the controller, and traverse grinding is automatically performed based on the grinding recipe.

[0016] With this cylindrical grinding method of the present invention, it is possible to prevent breakage of the cone portion and other parts, as well as displacement of the crystal rods, caused by excessive clamping force or the maximum cutting allowance per pass, and grinding can be performed with stable quality. Furthermore, by automatically determining the presence or absence of cone sections, human intervention is unnecessary, thus reducing costs. Moreover, since it supports both patterns with and without cone sections, grinding can be performed efficiently. [Effects of the Invention]

[0017] In the cylindrical grinding machine and the cylindrical grinding method of the present invention, it is possible to prevent the occurrence of breakage in the cone portion or the like and the positional deviation of the crystal bar, and perform traverse grinding of the crystal bar with stable quality. At the same time, cost reduction can be achieved by various automations, and efficiency can be improved by corresponding to both the presence and absence of the cone portion or the like.

Brief Description of the Drawings

[0018] [Figure 1] It is an explanatory diagram showing an example of the cylindrical grinding machine of the present invention. [Figure 2] It is an explanatory diagram showing an example of the support device in the present invention. [Figure 3] It is an explanatory diagram showing an example of a discriminator (contact type). [Figure 4] It is an explanatory diagram showing an example of a discriminator (non-contact type). [Figure 5] It is an explanatory diagram showing an example of a conventional cylindrical grinding machine. [Figure 6] It is an explanatory diagram showing an example of a crystal bar of a dislocation-free crystal. [Figure 7] It is an explanatory diagram showing an example of a crystal bar with dislocation. [Figure 8] It is an explanatory diagram showing an example of a crystal bar with a dislocated portion cut off. [Figure 9] It is an explanatory diagram showing an example of a crystal bar having a cylindrical shape. [Figure 10] It is an explanatory diagram showing an example of holding a crystal bar with a cone (tail) by a support device. [Figure 11] It is an explanatory diagram showing an example of holding a crystal bar without a cone (tail) by a support device. [Figure 12] It is an explanatory diagram showing an example of the state during cylindrical grinding of a crystal bar with a cone (tail). [Figure 13] It is an explanatory diagram showing an example of the state during cylindrical grinding of a crystal bar without a cone (tail).

Best Mode for Carrying Out the Invention

[0019] Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited thereto. Figure 1 shows an overall view of the cylindrical grinding machine 1 of the present invention for traverse grinding a crystal rod 7. As shown in Figure 1, the cylindrical grinding machine 1 first has a transport unit 16, a pair of support units 4, and a grinding unit 5. Furthermore, it has a discriminator 11 and a controller 12. First, the transport unit 16 only needs to be capable of holding and transporting the crystal rod 7. The grinding unit 5 has a grinding wheel 6 and only needs to be capable of traversing and grinding the outer circumference of the crystal rod 7 while moving along the axial direction of the crystal rod 7 supported by a pair of support units 4. These transport unit 16 and grinding unit 5 are equipped with a drive mechanism (not shown) and are movable, and can be, for example, the same as conventional ones.

[0020] Next, the pair of support units 4 will be described. The pair of support units 4 are designed to hold the crystal rod 7, which has been transported by the transport unit 16, in the axial direction and allow it to rotate around the axis, and consist of a first support unit 4a and a second support unit 4b. The first support unit 4a has a main axis 3a, and the second support unit 4b has a sub-axis 3b. The main axis 3a has a support device 2a at its tip, and the sub-axis 3b has a support device 2b at its tip. Therefore, the crystal rod 7 is held and supported between the support device 2a of the main axis 3a and the support device 2b of the sub-axis 3b. Here, we show an example where the tail portion 10 of the crystal rod 7 is supported on the sub-axis 3b side and the cone portion 9 is supported on the main axis 3a side, but this is not the only option, and the orientation of the crystal rod 7 may be reversed.

[0021] Examples of support devices 2a and 2b are shown in Figure 2. Support devices 2a and 2b have a concave first support part 14 with a conical hole capable of supporting the conical crystal ends (cone part 9 and tail part 10) of the crystal part 7, and a second support part 15 capable of supporting the flat crystal ends. The first support part 14 and the second support part 15 can be similar to, for example, the fixed support part 114 and the floating support part 115 in Figure 10. Therefore, both support devices 2a and 2b can support the crystal rod 7 regardless of the presence or absence of the conical cone portion 9 and tail portion 10 at both ends of the crystal rod 7.

[0022] Furthermore, the pair of support units 4 have a drive mechanism 13. This drive mechanism 13 has, for example, a motor (servo motor, etc.) and can move the second support unit 4b toward the first support unit 4a. Of course, it can also be moved in the opposite direction to the first support unit 4a. By adjusting the rotation speed and direction of the motor, the movement speed and direction of the second support unit 4b can be freely changed and adjusted.

[0023] Next, the discriminator 11 will be described. The discriminator 11 is a means capable of automatically determining the presence or absence of the cone portion 9 and the tail portion 10, and can be a contact type that contacts the cone portion 9, etc., or a non-contact type. Below, a specific example of the configuration of the discriminator 11 and an example of the mechanism for determination in the preparation process (hereinafter sometimes referred to as the loading process) will be described, but the configuration and mechanism are not limited to the following example and can be determined as appropriate. In addition, the explanation will be given using the support device 2b side (tail portion 10 side) as an example, but the same can be done on the support device 2a side (cone portion 9 side).

[0024] Figure 3 shows a contact-type discriminator 11. As shown in the upper part of Figure 3, this type includes an ingot detection rod 20, a sliding part 21, a detection dog 22, a first sensor 23a, a second sensor 23b, and an ingot detection rod movable device 24. The ingot detection rod 20 is held by the sliding part 21 through a conical hole in the first support part of the support device 2b and is slidable in the axial direction by the ingot detection rod movable device 24. The first sensor 23a and the second sensor 23b are for detecting the detection dog 22 provided on the ingot detection rod 20.

[0025] During the loading process, when the crystal rod 7 is supported and fixed in the axial direction by the sub-shaft 3b to which the support device 2b is attached at its tip, the tail portion 10 comes into direct contact with the ingot detection rod 20. The ingot detection rod 20 moves along the sliding portion 21, and the detection dog 22 installed on the ingot detection rod 20 moves simultaneously. Here, if the first sensor 23a is initially positioned to detect the detection dog 22 (before loading), and the second sensor 23b is positioned to detect the detection dog 22 when the crystal rod 7 (tailless 10b) is supported by the support device 2b (after loading), the presence or absence of the tail can be easily detected. In other words, in the case of tailed 10a, as shown in the middle of Figure 3, neither the first sensor 23a nor the second sensor 23b detects the detection dog 22. On the other hand, in the case of tailless 10b, as shown in the lower part of Figure 3, the first sensor 23a does not detect the detection dog 22, but the second sensor 23b detects the detection dog 22. This mechanism enables automatic detection of the presence or absence of the tail section 10 (and cone section 9). Table 1 shows the relationship between the presence or absence of the cone section, etc., and detection by the first and second sensors.

[0026] [Table 1]

[0027] Figure 4 shows a non-contact type discriminator 11. As shown in the upper part of Figure 4, a sensor mounting hole 30 is provided in the support device 2b, and a cone detection sensor 31 is placed inside it, and a detection line 32 is provided by the cone detection sensor 31. Similar to the contact type described above, when supporting and fixing the crystal rod 7 in the axial direction during the loading process, as shown in the middle of Figure 4, if there is a tail 10a, the detection line 32 of the cone detection sensor 31 provided in the sensor mounting hole 30 of the support device 2b is blocked, making detection possible. On the other hand, as shown in the lower part of Figure 4, if there is no tail 10b, even if the crystal rod 7 is fixed in the axial direction, the detection line 32 of the cone detection sensor 31 is not blocked, and therefore no detection occurs. The presence or absence of the tail 10 can be automatically determined based on whether or not detection occurs. In recent years, image sensors have become more sophisticated, making it easier to detect the cone-shaped tail portion 10 (cone portion 9) in images. Therefore, they can be used for automatic, non-contact detection of the presence or absence of the tail portion 10 (cone portion 9).

[0028] Next, the controller 12 will be described. The controller 12 can be, for example, a computer. This controller 12 has set values ​​registered for the clamping force CF that the pair of support units 4 use to hold the crystal rod 7 during traverse grinding, and the maximum cutting amount SRm (maximum cutting amount per grind) by the grinding unit 5, separately for the presence or absence of the cone portion 9 and the tail portion 10. These settings are not particularly limited and can be appropriately determined according to various conditions such as the type, length, and diameter of the crystal rod 7, or the length of the cone portion 9 and tail portion 10.

[0029] In particular, for the cone-less 9b and tail-less 10b models, it is preferable to set the clamping force CF (pressing force) to a relatively strong value so that a large frictional force is generated between the vertically (flat) cut surface and the second support part 15. On the other hand, for the cone-included 9a and tail-included 10a models, it is preferable to set the clamping force CF to a relatively weak value in order to prevent breakage from occurring near the contact point between the cone part 9 or tail part 10 and the first support part 14. Furthermore, the maximum cutting depth SRm (external force EF) per pass is preferably set to a relatively smaller value compared to the cases with a cone (9a) and a tail (10b) in the case of the cone-less 9b and tail-less 10b, in order to suppress the movement of the crystal rod 7 during cylindrical grinding.

[0030] The controller 12 is also connected to a pair of support units 4 (such as the drive mechanism 13), a grinding unit 5, a discriminator 11, a transport unit 16, etc., enabling automatic operation of these components. In addition, the controller 12 is programmed to automatically select a grinding recipe that has registered values ​​for the clamping force CF and the maximum grinding allowance SRm per pass, for example, as described above, in response to the presence or absence of the cone section 9 etc., which is automatically detected by the discriminator 11. The controller 12 is programmed to automatically perform traverse grinding based on the automatically selected appropriate grinding recipe.

[0031] As described above, the cylindrical grinding machine 1 of the present invention allows for traverse grinding with an appropriate clamping force CF and a maximum cutting allowance SRm per pass, depending on the presence or absence of the cone portion 9. Therefore, it is possible to suppress the occurrence of breakage of the cone portion 9 and other components, and displacement of the crystal rod 7, which were problems in the past. Consequently, it is possible to prevent defects in the cylindrical ground surface and diameter accuracy, and to provide a crystal rod with stable quality after cylindrical grinding. Moreover, since the series of traverse grinding processes, including the determination of the presence or absence of the cone portion 9, can be performed automatically regardless of the presence or absence of the cone portion 9, the crystal rod can be ground very efficiently and at low cost.

[0032] Next, the cylindrical grinding method of the present invention will be described. First, prepare the cylindrical grinding machine 1 of the present invention (a pair of support units 4, a grinding unit 5, a discriminator 11, a controller 12, a transport unit 16, etc.) and the crystal rod 7 to be ground, as shown in Figure 1, etc.

[0033] Then, in the preparation process (loading process), the crystal rod 7 is first moved using the transport unit 16 to align the crystal axis center with the rotation centers of the main axis 3a and the sub-axis 3b. Next, in order to sandwich the crystal rod 7 between the first support unit 4a and the second support unit 4b, the second support unit 4b is moved toward the first support unit 4a by the drive mechanism 13. The crystal rod 7 is then sandwiched and supported by this pair of support units 4.

[0034] At this time, the presence or absence of the cone portion 9 of the crystal rod 7 is automatically determined by the discriminator 11. A contact type as shown in Figure 3 may be used, or a non-contact type as shown in Figure 4 may be used. In the controller 12, pre-set values ​​(set value for clamping force CF, set value for maximum cutting amount SRm per pass) are registered for both cases: when the cone portion 9 etc. is present and when it is not. Therefore, based on the result of the automatic determination by the discriminator 11, a grinding recipe including the appropriate set value is automatically selected. After the crystal rod 7 is held in the crystal axis direction by the pair of support units 4, the transport unit 16 releases the crystal rod 7 and retracts.

[0035] Then, traverse grinding is automatically performed based on the automatically selected grinding recipe described above. That is, while the crystal rod 7 is held and supported by the automatically selected clamping force CF and rotated around its axis, the grinding wheel 6 of the grinding unit 5 is used to grind the crystal rod to the finished diameter (final target diameter). If the amount of material removed SR when grinding the crystal rod to the finished diameter (final target diameter) exceeds the maximum amount of material removed SRm per pass, the outer circumference of the crystal rod 7 is automatically ground while applying a grinding load so that the amount of material removed becomes SRm. If the remaining material to be removed to reach the final target diameter does not exceed SRm, the system automatically performs a final grind to remove only the remaining material and then terminates. The remaining material to be removed can be calculated by subtracting SRm from SR by the number of grinding cycles, and this can be automatically calculated by, for example, the controller 12. [Examples]

[0036] The present invention will be described more specifically below with reference to examples and comparative examples, but the present invention is not limited to these examples. First, 50 crystal rods were prepared, each with a diameter of 200 mm, a cone length of 150 mm, a tail length of 250 mm, and a straight body length of 1,000 mm. Of these, 25 were kept as crystal rods with both a cone and a tail (Set A). The remaining 25 were cut perpendicular to the crystal axis to create flat ends, resulting in crystal rods without a cone and without a tail (Set B). Then, we prepared four sets of these 50-piece crystal rods.

[0037] (Examples) A cylindrical grinding machine 1 of the present invention, as shown in Figure 1, was prepared, and one of the four sets of crystal rods described above was subjected to the cylindrical grinding method of the present invention, which automatically determined the presence and absence of the cone and tail portions, automatically selected a grinding recipe according to the automatic determination, and automatically performed traverse grinding based on the automatically selected grinding recipe. The presence or absence of the cone and tail portions was automatically determined using the non-contact type discriminator shown in Figure 4. The clamping force exerted by the drive mechanism of the support unit of the cylindrical grinding machine used was 16kN at 100% output, as measured by a load cell.

[0038] The relationship between the presence or absence of the cone and tail sections registered in the controller and the grinding recipe (setting value of clamping force (pressing force) CF and setting value of maximum cutting amount SRm per pass) is as follows. [Selective grinding recipe for cases with both a cone and a tail] CF: Output 90% SRm: 10mm [Selective grinding recipe without cone and tail] CF: Output 98% SRm: 6mm

[0039] We then investigated the occurrence of quality defects due to breakage of the cone or tail portion in Set A (25 pieces) and the occurrence of quality defects due to misalignment of the crystal rods during cylindrical grinding in Set B (25 pieces), and the results were as follows. Number of defective items (broken) in Set A: 0 (Defective item rate: 0%) Quality defects in Set B (misalignment): 0 units (Quality defect rate: 0%)

[0040] (Comparative Examples 1-3) Unlike the embodiment, a cylindrical grinding machine was prepared that lacks the functions of automatic identification of the cone and tail sections, automatic selection of a grinding recipe according to the automatic identification, and automatic execution of traverse grinding based on the automatically selected grinding recipe. This cylindrical grinding machine does not have the discriminator or controller of the cylindrical grinding machine 1 of the present invention shown in Figure 1, and is always configured to execute only a fixed grinding recipe (fixed CF, fixed SRm) that has been manually adjusted in advance by the operator. Otherwise, it is the same as the cylindrical grinding machine 1 of the embodiment, and the maximum output of the drive mechanism of the support unit is also the same. Using this cylindrical grinding machine, traverse grinding was performed on three of the four sets of crystal rods mentioned above, always using a consistent grinding recipe.

[0041] The grinding recipes for Comparative Examples 1-3 are as follows. [Grinding recipe for Comparative Example 1] CF: Always 90% output SRm: Always 10mm [Grinding recipe for Comparative Example 2] CF: Always 98% output SRm: Always 10mm [Grinding recipe for Comparative Example 3] CF: Always 98% output SRm: Always 6mm

[0042] Then, similar to the examples, we investigated the occurrence of quality defects due to breakage of the cone and tail portions in Set A (25 pieces), and the occurrence of quality defects due to misalignment of the crystal rods during cylindrical grinding in Set B (25 pieces). The results were as follows. Furthermore, all the breaks that occurred in Set A were related to the tail section; no breaks occurred in the cone section. [Results of Comparative Example 1] Number of defective items (broken) in Set A: 0 (Defective item rate: 0%) Quality defects in Set B (misalignment): 5 units (Quality defect rate: 20%) [Results of Comparative Example 2] Quality defects (breakage) in Set A: 3 pieces (Quality defect rate: 12%) Quality defects in Set B (misalignment): 2 units (Quality defect rate: 8%) [Results of Comparative Example 3] Quality defects (breakage) in Set A: 3 pieces (Quality defect rate: 12%) Quality defects in Set B (misalignment): 0 units (Quality defect rate: 0%)

[0043] As can be seen from the results of the Examples and Comparative Examples 2 and 3, the rate of quality defects due to breakage could be reduced by up to 12%. Furthermore, as can be seen from the results of the Examples and Comparative Example 1, the rate of quality defects due to misalignment could be reduced by up to 20%. Only the Examples were able to reduce both quality defect rates to 0%. Thus, with this invention, cylindrical grinding can be performed efficiently with low cost and stable quality without the need to prepare separate cylindrical grinding machines adjusted for the presence or absence of cones (tails), and without the operator having to manually set the optimal recipe each time depending on whether or not there are cones (tails).

[0044] It should be noted that the present invention is not limited to the embodiments described above. The embodiments described above are illustrative, and any configuration that is substantially identical to the technical idea described in the claims of the present invention and achieves similar effects is included within the technical scope of the present invention. [Explanation of Symbols]

[0045] 1...Cylindrical grinding machine of the present invention, 2a, 2b...Support device, 3a...Main spindle, 3b...Sub-spindle, 4...a pair of support units, 4a...first support unit, 4b...second support unit, 5…Grinding unit, 6…Grinding wheel, 7...Crystal rod, 7a...Dislocation-free crystal rod, 7b...Dislocation-treated crystal rod 7c...Crystal rod with dislocations cut, 7d...Cut-out crystal rod, 8...Straight body section, 9, 9a...Cone section, 9b...Flat surface where the cone section has been cut off. 10, 10a...Tail section, 10b...Flat surface after the tail section has been cut off. 11…Discriminator, 12…Controller 13…Drive mechanism, 14…First support part, 15…Second support part, 16…Transport unit, 20...Ingot detection rod, 21...Sliding part, 22...Detection dog, 23a...First sensor, 23b...Second sensor, 24...Ingot detection rod movable device, 30...Sensor mounting hole, 31...Conical part detection sensor, 32...Detection line, D...Dislocated part, CF...Pinching force, EF...External force, SR... Machining allowance, SRm... Maximum machining allowance per pass.

Claims

1. A cylindrical grinding machine comprising a pair of support units that axially clamp the crystal rod and make it rotatable around its axis by a main shaft and a sub-shaft, each of which has a support device attached to its tip to support the end of the crystal rod, and a grinding unit that traverses grinds the outer circumference of the crystal rod while moving along the axial direction of the crystal rod supported by the pair of support units, The support device has a concave first support portion capable of supporting a conical crystal end and a second support portion capable of supporting a flat crystal end, and is capable of supporting the crystal rod regardless of whether or not there are conical cone portions and tail portions at both ends of the crystal rod. Furthermore, a discriminator capable of automatically determining the presence or absence of the cone portion and tail portion, The system includes a controller that stores set values ​​for the clamping force applied by the pair of support units to the crystal rod during the traverse grinding process, and for the maximum amount of material removed per pass by the grinding unit, separately for the presence or absence of the cone portion and the tail portion. A cylindrical grinding machine characterized in that a grinding recipe having the gripping force corresponding to the presence or absence of the cone portion and tail portion, which are automatically determined by the discriminator, and the set value of the maximum grinding allowance per pass is automatically selected by the controller, and traverse grinding can be automatically performed based on the grinding recipe.

2. A method for cylindrical grinding a crystal rod, using a cylindrical grinding machine having a pair of support units that axially clamp the crystal rod and make it rotatable around an axis by a main shaft and a sub-shaft, each of which has a support device attached to the tip of the crystal rod's end, and a grinding unit that traverse grinds the outer circumference of the crystal rod while moving along the axial direction of the crystal rod supported by the pair of support units, The support device has a concave first support portion capable of supporting a conical crystal end and a second support portion capable of supporting a flat crystal end, and is capable of supporting the crystal rod regardless of whether or not there are conical cone portions and tail portions at both ends of the crystal rod. Furthermore, a discriminator capable of automatically determining the presence or absence of the cone portion and tail portion, A controller is provided in which set values ​​are registered for the clamping force applied by the pair of support units to the crystal rod during the traverse grinding process, and for the maximum amount of material removed per pass by the grinding unit, separately for the presence or absence of the cone portion and the tail portion. A cylindrical grinding method characterized by the following: when the crystal rod is clamped and fixed by the pair of support units, the presence or absence of the cone portion and tail portion of the crystal rod is automatically determined by the discriminator, the clamping force corresponding to the presence or absence of the cone portion and tail portion determined by the controller and the set value of the maximum cutting allowance per pass are automatically selected, and traverse grinding is automatically performed based on the grinding recipe.

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