Machine tool and method for controlling machine tool

Abstract

The present invention provides a machine tool and a method for controlling a machine tool which make it possible to quickly select an operation after removing burrs. Provided is a machine tool (illustrated as an automatic lathe 1) provided with: a first main shaft 10 for rotatably holding a first work (illustrated as a work W1); a tool table 31 on which a tool 30 that cuts the first work is mounted; a control unit 40a for cutting, by the tool, a burr B generated on a joined portion of the first work and a second work (illustrated as a work residual material W2) that has the same diameter as the first work and is integrally joined with the first work. On the basis of a cutting resistance generated at a time when cutting is performed continuously from one of the first work and the second work to the other by the tool 30, the control unit calculates a core deviation amount s of the second work with respect to the integrally joined first work.

Description

[Technical field]

[0001] The present invention relates to a machine tool that uses a tool to remove burrs generated at a joint between a first workpiece and a second workpiece, and a method for controlling the machine tool. [Background technology]

[0002] In machine tools, there are cases where materials are left over without being processed. When materials are left over, it becomes difficult to reduce material costs and also makes it difficult to contribute to environmental conservation. Therefore, it is considered to make the most effective use of materials by frictionally joining a specified workpiece with the remaining workpiece material. When a workpiece and a residual workpiece are friction-welded, it is often impossible to determine the misalignment between the workpiece and the residual workpiece by appearance. For this reason, for example, Patent Document 1 discloses a technique for detecting data from before the start of welding to the end of welding to determine whether or not there is misalignment. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 7-195183 Summary of the Invention [Problem to be solved by the invention]

[0004] However, burrs are often generated at the joint between the friction-welded workpiece and the remaining workpiece, and therefore a task of removing the burrs (deburring) is required. Meanwhile, depending on the degree of misalignment between the workpiece and the remaining workpiece, separate tasks such as cutting into a desired product, redoing the deburring, and redoing the joining of the workpiece and the remaining workpiece are required. In order to be able to quickly select an appropriate task from among these separate tasks, it is desirable to know the degree of misalignment between the workpiece and the remaining workpiece when deburring is performed. However, the technology described in the above Patent Document 1 can detect the presence or absence of misalignment between the workpiece and the remaining workpiece during joining, but it cannot tell the degree of misalignment after joining.

[0005] The present invention has been made in consideration of the above-mentioned circumstances, and has an object to provide a machine tool and a method for controlling the machine tool that enable prompt selection of an operation to be performed after deburring has been performed. [Means for solving the problem]

[0006] First, the present invention is a machine tool comprising a first spindle that rotatably holds a first workpiece, a tool table that mounts a tool for cutting the first workpiece, and a control unit that causes the tool to remove burrs generated at the joint between the first workpiece and a second workpiece that has the same diameter as the first workpiece and is integrally joined to the first workpiece, wherein the control unit calculates an amount of misalignment of the second workpiece relative to the integrally joined first workpiece based on cutting resistance generated when the tool cuts continuously from one of the first workpiece and the second workpiece to the other.

[0007] Secondly, the amount of misalignment of the second workpiece relative to the first workpiece joined together is calculated based on the cutting resistance generated when cutting the second workpiece and the cutting resistance generated when cutting the first workpiece.

[0008] Thirdly, the control unit detects the cutting resistance based on the load applied to the tool that cuts continuously from one of the first workpiece and the second workpiece to the other.

[0009] Fourthly, the control unit determines the cutting resistance based on a load applied to a motor that drives the first spindle.

[0010] Fifth, the machine further comprises a second spindle arranged opposite the first spindle to rotatably hold the second workpiece, and a guide bush arranged between the first spindle and the second spindle and concentric with the first spindle.

[0011] Sixth, the control unit controls the movement of at least one of the first spindle or the second spindle so that the first spindle and the second spindle move closer to each other while rotating a first workpiece held by the first spindle and a second workpiece held by the second spindle, and presses a rear end portion of the second workpiece against a front end portion of the first workpiece to frictionally join them.

[0012] Seventh, a control method for a machine tool including a first spindle that rotatably holds a first workpiece, a tool table on which a tool for cutting the first workpiece is mounted, a second spindle that is disposed opposite the first spindle and rotatably holds a second workpiece having the same diameter as the first workpiece transferred from the first spindle, and a control unit that controls operations of the first spindle, the second spindle, and the tool table, the control method comprising the steps of: moving the first spindle and the second spindle relatively so as to approach each other while rotating the first spindle and the second spindle, respectively, to press a rear end portion of the second workpiece against a front end portion of a newly supplied first workpiece to frictionally join them; removing burrs generated at a joint between the second workpiece and the newly supplied first workpiece by the tool; calculating an amount of misalignment of the second workpiece with respect to the first workpiece that is joined together, based on cutting resistance generated when the tool cuts the first workpiece or the second workpiece from one to the other in succession; and causing the machine tool to perform an operation corresponding to the calculated amount of misalignment, by the control unit. Effect of the Invention

[0013] The present invention can achieve the following effects. The control unit calculates the amount of misalignment of the second workpiece relative to the first workpiece when removing burrs that have occurred at the joint, so the degree of misalignment between the first workpiece and the second workpiece can be known during the deburring process. This makes it possible to quickly select an appropriate operation to be performed after the deburring process, thereby reducing the manufacturing cost of the product and stabilizing the quality. [Brief description of the drawings]

[0014] [Figure 1] 1 is a schematic configuration diagram of an automatic lathe as an example of a machine tool according to the present invention; [Diagram 2] 13 is an operational flowchart including a joining determination. [Figure 3A] 13A and 13B are diagrams illustrating operations for holding a remaining workpiece and a newly supplied workpiece. [Figure 3B] 13A and 13B are diagrams illustrating a joining operation of a remaining workpiece and a newly supplied workpiece. [Figure 3C] 13A and 13B are diagrams showing the holding operation of the workpiece and the integrally joined workpiece remainder. [Figure 3D] 11A and 11B are diagrams illustrating a deburring operation of a joint portion between a workpiece remaining material and the workpiece. [Figure 3E] 13A and 13B are diagrams illustrating the positioning operation of the integrally joined workpiece remainder and the workpiece. [Figure 3F] 11A and 11B are diagrams showing a cutting operation performed on the integrally joined workpiece remainder. [Figure 4A] 1A to 1C are diagrams illustrating cutting resistance generated during a deburring operation. [Figure 4B] 1A to 1C are diagrams illustrating cutting resistance generated during cutting of a workpiece residue. [Figure 4C] 1A and 1B are diagrams illustrating cutting resistance generated during cutting of a workpiece. [Diagram 5] 11A and 11B are diagrams illustrating the amount of misalignment and the amount of cutting in of the joined workpiece remainder and the workpiece. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, a machine tool and a method for controlling the machine tool according to the present invention will be described with reference to the drawings. As shown in Fig. 1, an automatic lathe (machine tool) 1 includes a first spindle 10 and a tool table 31. The first spindle 10 can grip (hold) a workpiece W1 via a first chuck 11 shown in Fig. 3A etc. The first chuck 11 is configured concentrically with the first spindle 10 and can rotate freely together with the first spindle 10.

[0016] The workpiece W1 is a long, round bar material, and is fed from the rear end of the first spindle 10 by using a pushing arrow of a bar feeder. A finger chuck 16 shown in Fig. 3A is provided at the tip of the pushing arrow, and the finger chuck 16 grips the rear end of the workpiece W1. The first spindle 10 is rotatably supported by a headstock 12 with its axis in the Z1-axis direction shown in Fig. 1 as its axis, and is rotationally driven by the power of a spindle motor 13 provided on the headstock 12. The headstock 12 is mounted on a Z1-axis feed mechanism 14 and is movable in the Z1-axis direction.

[0017] The Z1-axis feed mechanism 14 is fixed to the bed 1a and has a Z1-axis rail 14a extending in the Z1-axis direction. A Z1-axis slider 14b that slides along the Z1-axis direction by a Z1-axis motor 14c is attached to the Z1-axis rail 14a. The headstock 12 is installed on the Z1-axis slider 14b.

[0018] A guide bush 18 that maintains the cutting position is provided in front of the headstock 12. The guide bush 18 is supported by a support table 17, which is fixed to the bed 1a. The workpiece W1 is supported by the guide bush 18 so as to be rotatable around the Z1 axis, and is sent to the front side of the support table 17. In this way, when the guide bush 18 is provided in front of the first spindle 10, the material from the first chuck 11 to the guide bush 18 becomes workpiece waste W2 that cannot be cut. However, by joining this workpiece waste W2 to a newly supplied workpiece W1, the material can be utilized effectively, thereby reducing material costs.

[0019] A movable table 32 is provided on the front side of the support table 17. The movable table 32 moves the tool table 31 in the X1-axis direction perpendicular to the Z1-axis direction and in the Y1-axis direction perpendicular to the Z1-axis and X1-axis directions. A tool 30 with its tip facing in the X1-axis direction is attached to the tool table 31. The workpiece W1 can be machined with the tool 30 by moving the first spindle 10 in the Z1-axis direction and moving the tool table 31 in the X1-axis direction or the Y1-axis direction.

[0020] The automatic lathe 1 is equipped with a second spindle 20 at a position facing the first spindle 10. The second spindle 20 can grip (hold) the workpiece residue W2 via a second chuck 21 shown in FIG. 3A etc. The second chuck 21 is configured concentrically with the second spindle 20 and can rotate freely together with the second spindle 20. The workpiece residue W2 is, for example, a round bar having the same diameter as the workpiece W1, and is a remaining material that cannot be machined by the first spindle 10. The workpiece residue W2 is, for example, transferred from the first spindle 10 to the second spindle 20 and held by the second spindle 20 via the second chuck 21.

[0021] The second spindle 20 is rotatably supported by a headstock 22 with its axis in the Z2-axis direction parallel to the Z1-axis direction, and is rotationally driven by the power of a spindle motor 23 provided on the headstock 22. The headstock 22 is mounted on a Z2-axis direction feed mechanism 24 and an X2-axis direction feed mechanism 25, and is movable in the Z2-axis direction and the X2-axis direction. The Z2-axis feed mechanism 24 is, for example, disposed on the X2-axis feed mechanism 25 and has a Z2-axis rail 24a extending in the Z2-axis direction. A Z2-axis slider 24b that slides along the Z2-axis direction by a Z2-axis motor 24c is attached to the Z2-axis rail 24a. The headstock 22 is installed on the Z2-axis slider 24b.

[0022] The X2-axis feed mechanism 25 is fixed to, for example, the bed 1a and has an X2-axis rail 25a parallel to the X1-axis direction. An X2-axis slider 25b that slides along the X2-axis direction by an X2-axis motor 25c is attached to the X2-axis rail 25a. The Z2-axis rail 24a of the Z2-axis feed mechanism 24 is provided on the X2-axis slider 25b.

[0023] The rotation of the first spindle 10 and the second spindle 20, and the movements of the first spindle 10, the second spindle 20, and the moving table 32 are controlled by a control device 40. The control device 40 has a control unit 40a and an input unit 40b, which are connected via a bus. The control unit 40a is made up of a CPU, a memory, etc., and loads various programs and data stored in, for example, a ROM into a RAM and executes the programs, thereby controlling the operation of the automatic lathe 1 based on the programs.

[0024] The rotation of the first spindle 10 and the second spindle 20, the movements of the first spindle 10, the second spindle 20 and the moving table 32, etc. can be set by a program or by inputting to the input section 40b. The control unit 40a also includes a calculation unit 40c, a comparison unit 40d, and a determination unit 40e. The calculation unit 40c calculates the amount of misalignment s of the workpiece remainder W2 relative to the integrally joined workpiece W1 based on, for example, the cutting resistance generated when a burr B generated at a joint between the workpiece remainder W2 and the workpiece W1 is cut by the tool 30.

[0025] The comparison unit 40d compares the misalignment amount s calculated by the calculation unit 40c with a first threshold value α and a second threshold value β that are preset to select a subsequent operation. The determination unit 40e receives the comparison result of the comparison unit 40d and determines whether the calculated misalignment amount s exceeds the first threshold value α, or whether the calculated misalignment amount s is equal to or less than the first threshold value α but exceeds the second threshold value β, or whether the calculated misalignment amount s is equal to or less than the second threshold value β. A plurality of operation contents corresponding to the misalignment amount s are stored in advance in the memory of the control unit 40a.

[0026] FIG. 2 is an operational flowchart including the joining determination, and FIGS. 3A to 3F are diagrams showing operations relating to the joining determination. In an automatic lathe 1 as shown in Fig. 1, the length of the workpiece W1 shortens with each cut-off. As machining of the workpiece W1 progresses, when the total length of the workpiece W1 held by the first spindle 10 shortens to about the length from the first chuck 11 to the guide bush 18, this shortened portion becomes a workpiece residue that cannot be cut. In order to make effective use of this workpiece residue, the automatic lathe 1 transfers the short workpiece held by the first spindle 10 to the second spindle 20.

[0027] In detail, first, the axis of the first spindle 10 and the axis of the second spindle 20 are arranged concentrically, and, for example, the second spindle 20 is brought close to the first spindle 10. Next, the first chuck 11 is opened, and a new workpiece W1 is supplied from the rear of the first spindle 10. Then, the first chuck 11 is closed, and the newly supplied workpiece W1 is held by the first spindle 10 (step S10 in FIG. 2, FIG. 3A). When the new workpiece W1 is supplied to the first spindle 10, the short workpiece (which will eventually become the workpiece residue W2) held by the first spindle 10 is pushed out from the guide bush 18 to the front side of the support table 17. Then, the second chuck 21 is closed, and the workpiece residue W2 is held by the second spindle 20 (step S10 in FIG. 2).

[0028] Next, while rotating the first spindle 10 and the second spindle 20 at different rotation speeds, for example, as shown by a right-facing arrow in FIG. 3B, the second spindle 20 is brought close to the first spindle 10, and the rear end portion of the workpiece residue W2 is pressed against the front end portion of the new workpiece W1 to be friction-welded (step S11 in FIG. 2). As a result, frictional heat is generated at the rear end portion of the workpiece residue W2 and the front end portion of the workpiece W1 due to the speed difference between the rotation speed of the first spindle 10 and the rotation speed of the second spindle 20, causing softening, and the rear end portion of the workpiece residue W2 is pressed against the front end portion of the workpiece W1 to be welded, and the workpiece residue W2 and the workpiece W1 are integrated. Note that, in FIG. 3B, the rotation directions of the first spindle 10 and the second spindle 20 are both shown in the same direction, but since the first spindle 10 and the second spindle 20 only need to rotate with a speed difference, the first spindle 10 may be rotated in the opposite direction to the rotation direction of the second spindle 20. Alternatively, only either the first main shaft 10 or the second main shaft 20 may be rotated.

[0029] Next, the second chuck 21 is opened to release the retained workpiece W2 (step S12 in FIG. 2), and the second spindle 20 is moved away from the first spindle 10 as shown by the leftward arrow in FIG. 3C. As a result, the workpiece W1 of the joined workpiece W2 and the workpiece W1 is held by the first spindle 10, and the tip of the workpiece W2 becomes a free end. Next, burrs B generated at the joint between the workpiece residual material W2 and the workpiece W1 are cut (removed) by the tool 30 (step S13 in FIG. 2).

[0030] 3D, the tool 30 is placed, for example, at a position closer to the second chuck 21 than the joint portion of the workpiece remainder W2 and the workpiece W1. Then, a predetermined cutting depth is set, and the tool 30 is moved to a position closer to the first chuck 11 than the joint portion of the workpiece W1 and the workpiece remainder W2 while rotating the first spindle 10. As a result, the tool 30 processes the workpiece remainder W2, the joint portion of the workpiece remainder W2 and the workpiece W1, and the workpiece W1 in that order.

[0031] In the deburring process of step S13, the control unit 40a detects the cutting resistance generated when the burr B is cut by the tool 30, for example, from the load of the tool 30. Then, the calculation unit 40c calculates the amount of misalignment s of the workpiece remainder W2 relative to the joined workpiece W1 (the distance between the axis of the workpiece W1 and the axis of the workpiece remainder W2) based on the detected cutting resistance (step S14 in FIG. 2).

[0032] Specifically, when the tool 30 processes the workpiece residue W2, the junction between the workpiece residue W2 and the workpiece W1, and the workpiece W1 in that order as described above, as shown in the graph of cutting resistance (vertical axis) and time (horizontal axis) in Figure 4A, the period up to time T1 corresponds to the machining time of the workpiece residue W2, the period from time T1 to time T2 corresponds to the machining time of the junction between the workpiece residue W2 and the workpiece W1, and the period from time T2 onwards corresponds to the machining time of the workpiece W1.

[0033] Since the workpiece W1 is held by the first spindle 10, if there is misalignment, this misalignment appears in the remaining workpiece W2. The cutting resistance is greater during the machining time of the remaining workpiece W2 (up to time T1 in FIG. 4A) than during the machining time of the workpiece W1 (after time T2). More specifically, as shown in Fig. 5, which shows the process of machining the workpiece remainder W2, the misalignment amount of the workpiece remainder W2 relative to the joined workpiece W1 is s, and the cutting depth into the workpiece W1 for deburring is ap. In the range where the side surface of the workpiece remainder W2 protrudes from the side surface of the workpiece W1 (the upper side of the workpiece remainder W2 in Fig. 5), the cutting depth is greater than the cutting depth ap by the amount of misalignment amount s added. In contrast, in the range where the side surface of the workpiece remainder W2 is recessed from the side surface of the workpiece W1 (the lower side of the workpiece remainder W2 in Fig. 5), the cutting depth is shallower so that the cutting depth ap is less than the misalignment amount s.

[0034] For this reason, as shown in Fig. 4B, which shows an enlarged view of the machining time of the workpiece residue W2 (up to time T1), the cutting resistance is small (minimum) in the range where the side surface of the workpiece residue W2 is recessed from the side surface of the workpiece W1, and is large (maximum) in the range where the side surface of the workpiece residue W2 protrudes from the side surface of the workpiece W1, and these minimum and maximum values ​​are repeated as the workpiece residue W2 rotates. And, during the machining time of this workpiece residue W2 (up to time T1), the difference between the minimum and maximum values ​​of the cutting resistance becomes very large.

[0035] On the other hand, since the workpiece W1 is held by the first spindle 10, the workpiece W1 is cut evenly around the entire circumference with a cutting depth ap. As shown in Fig. 4C, which shows an enlarged view of the machining time of the workpiece W1 (after time T2), the difference between the minimum and maximum cutting resistance is smaller than that in Fig. 4B. The amount of misalignment of the workpiece residue W2 is s [mm] and the cutting depth is ap [mm]. The specific cutting resistance of the workpiece W1 and the workpiece residue W2 is Ks [N / mm 2 ] and the feed rate of the tool 30 is f [mm / rev], then on the workpiece remainder W2 side (FIG. 4B), for example, the maximum cutting resistance Fmax = Ks × f × (s + ap) In other words, the amount of misalignment s of the workpiece remainder W2 and the amount of cut ap of the tool 30 are in a proportional relationship with the maximum cutting resistance Fmax.

[0036] In contrast, since the workpiece W1 is held by the first spindle 10 and theoretically there is no misalignment, the cutting resistance on the workpiece W1 side (FIG. 4C) is a constant value of Ks×f×ap, and can be expressed as, for example, an average value Fave (which may also be expressed as a maximum value F'max, since it is a constant value). This average value Fave of the cutting resistance is smaller than the maximum value Fmax of the cutting resistance on the workpiece remainder W2 side. By eliminating Ks×f from these two equations, the amount of misalignment s can be calculated as shown in equation 1.

[0037]

number

[0038] In other words, since the cutting depth ap of the tool 30 is a known value set by the input section 40b, etc., the amount of misalignment s of the workpiece remainder W2 relative to the workpiece W1 can be easily determined from the difference between the maximum value Fmax of the cutting resistance on the workpiece remainder W2 side and the average value Fave of the cutting resistance on the workpiece W1 side. In addition, the maximum value Fmax of the cutting resistance on the workpiece remainder W2 side occurs at approximately the same position during one rotation of the workpiece remainder W2. Therefore, by checking against the rotation phase of the first main spindle 10, the misalignment direction of the workpiece remainder W2 relative to the workpiece W1 can be determined.

[0039] The load on the tool 30 can be detected by, for example, a dynamometer installed on the tool table 31. By using the load on the tool 30, the cutting resistance can be easily and accurately calculated. In this embodiment, an example has been described in which the cutting resistance is calculated from the load on the tool 30, but the present invention is not limited to this example. For example, the cutting resistance may be calculated from the current value of the spindle motor 13 that drives the first spindle 10 that holds the workpiece W1. Since the load on the spindle motor 13 can be determined by using the current value of the spindle motor 13, the cutting resistance can be calculated using existing equipment, and dedicated equipment for detecting the cutting resistance is not required.

[0040] In this way, the calculation unit 40c calculates the amount of misalignment s of the workpiece remaining material W2 relative to the workpiece W1 when removing burrs generated at the joint, so the degree of misalignment can be known during the deburring process. Therefore, an appropriate operation can be quickly selected after the deburring process, which can reduce the manufacturing cost of the product and stabilize the product quality.

[0041] Specifically, the comparison unit 40d compares the calculated misalignment amount s with the first threshold value α (step S15 in FIG. 2). When the determination unit 40e determines that the calculated misalignment amount s exceeds the first threshold value α (YES in step S15), the misalignment amount s is larger than expected, and the control unit 40a calls, for example, a program of the operation content "redoing the frictional joining between the workpiece and the workpiece residue" from the memory. As a result, the control unit 40a, for example, moves the second spindle 20 closer to the first spindle 10. Next, the second spindle 20 holds the workpiece residue W2, the first spindle 10 holds the workpiece W1, and cuts off the joint portion between the workpiece W1 and the workpiece residue W2 (step S20). After that, the process returns to step S11, and the rear end portion of the workpiece residue W2 is pressed against the front end portion of the workpiece W1 to perform frictional joining. If the amount of misalignment s exceeds the first threshold value α, the driving of the first spindle 10 and the like may be stopped, and a lamp may be turned on or a buzzer may be sounded to notify the operator, and the series of routines may be terminated.

[0042] On the other hand, in step S15, if the determining unit 40e determines that the calculated misalignment amount s is equal to or less than the first threshold value α (NO in step S15), the process proceeds to step S16, where the comparing unit 40d compares the calculated misalignment amount s with the second threshold value β. If the determining unit 40e determines that the calculated misalignment amount s exceeds the second threshold value β (YES in step S16), the misalignment amount s is only slightly larger than expected. Therefore, the control unit 40a calls up a program for another operation content "redoing deburring" from the memory. As a result, the control unit 40a sets the cutting depth of the tool 30 to a value larger than the previous time (step S21), returns to step S13, and performs deburring again with the tool 30.

[0043] On the other hand, in step S16, when the determining unit 40e determines that the calculated misalignment amount s is equal to or less than the second threshold value β (NO in step S16), the misalignment amount s is small as expected. Therefore, the control unit 40a calls a program for another operation content "Start cutting processing of a predetermined shape" from the memory. As a result, the control unit 40a first opens the first chuck 11 (step S17).

[0044] Next, the control unit 40a moves the pushing arrow backward, and as shown by the right-pointing arrow in Fig. 3E, the integrally joined workpiece W1 and the remaining workpiece W2 are temporarily pulled toward the guide bush 18. After that, the pushing arrow is moved forward, and as shown by the left-pointing arrow in Fig. 3E, the remaining workpiece W2 is protruded by a predetermined length from the guide bush 18, and the remaining workpiece W2 is positioned (step S18 in Fig. 2).

[0045] After the workpiece remainder W2 is positioned, the control unit 40a performs cutting processing of a predetermined shape on, for example, a portion of the workpiece remainder W2 using the tool 30 (step S19, FIG. 3F). In this way, the tip portion of the workpiece W1 and the rear end portion of the remaining workpiece W2 are friction-joined using the first spindle 10 and the second spindle 20 arranged opposite each other, and the automatic lathe 1 which combines cutting and joining (integrates the cutting process and the joining process) can reduce the manufacturing costs of the product.

[0046] In the above embodiment, an example in which the guide bush 18 is provided between the first spindle 10 and the second spindle 20 has been described. However, in the present invention, the workpiece W1 is held by the first spindle 10, and the misalignment amount s can be calculated during deburring by the tool 30, so the second spindle 20 and the guide bush 18 can be omitted. The present invention can also be applied to a structure in which only the openable and closable second chuck 21 is disposed in front of the first spindle 10. The workpiece W1 may be made of a material different from the workpiece residue W2. This is because the specific cutting resistance Ks is a fixed value determined according to the feed rate f, although it differs for each material. In the above embodiment, the workpiece residue W2 and the workpiece W1 are frictionally joined, but the present invention can also be applied to the case where the workpiece residue W2 and the workpiece W1 are joined by laser or heat welding. Furthermore, the present invention is not limited to the example of joining the workpiece residue W2, but can also be applied to the case where new materials or parts (for example, parts processed into a solid or hollow shape) are joined. When parts are joined, it is also possible to determine whether the amount of misalignment between the parts calculated by the machine tool in the above embodiment is within the tolerance (for example, coaxiality) of the product obtained by joining the parts. In the above embodiment, the tool 30 processes the workpiece residue W2, the joint between the workpiece residue W2 and the workpiece W1, and the workpiece W1 in that order, i.e., the tool 30 cuts from the workpiece residue W2 toward the workpiece W1, but the present invention can also be applied to a case where the tool 30 processes the workpiece W1, the joint between the workpiece W1 and the workpiece residue W2, and the workpiece residue W2 in that order, i.e., the tool 30 cuts from the workpiece W1 toward the workpiece residue W2. Note that the calculation of the amount of misalignment and specific processing according to the degree of misalignment when cutting from the workpiece W1 toward the workpiece residue W2 by the tool 30 overlaps with the case where the tool 30 cuts from the workpiece residue W2 toward the workpiece W1, and therefore will not be described here. [Explanation of symbols]

[0047] 1 Automatic lathe (machine tool) 1a Bed 10... 1st spindle 11 First chuck 12 ... Headstock 13 Spindle motor (motor) 14 Z1 axial feed mechanism 14a Z1 axis rail 14b Z1 axis slider 14c Z1 axis motor 16 ··· Finger chuck for push arrow 17... Support stand 18 Guide bush 20 ... 2nd spindle 21 Second chuck 22 ... Headstock 23 Spindle motor 24 Z2 axial feed mechanism 24a Z2 axis rail 24b Z2 axis slider 24c ··· Z2 axis motor 25 ··· X2 axial feed mechanism 25a ··· X2 axis rail 25b X2 axis slider 25c ··· X2 axis motor 30... tools 31 ... tool stand 32 Mobile stand 40 Control device 40a... Control section 40b Input section 40c... Calculation part 40d... Comparison section 40e: Judgment section W1: Work (first work) W2: Remaining workpiece (second workpiece) B Bali T1: Time T2: Time s: Misalignment amount ap: cutting depth

Claims

1. A machine tool including a first spindle that rotatably holds a first workpiece, a tool table that mounts a tool for cutting the first workpiece, and a control unit that causes a burr generated at a joint between the first workpiece and a second workpiece that has the same diameter as the first workpiece and is integrally joined to the first workpiece to be removed by the tool, The control unit calculates the amount of misalignment of the second workpiece relative to the first workpiece that is joined together, based on the cutting resistance generated when the tool continuously cuts from one of the first workpiece and the second workpiece to the other.

2. 2. The machine tool according to claim 1, wherein the amount of misalignment of the second workpiece relative to the first workpiece joined together is calculated based on the cutting resistance generated when cutting the second workpiece and the cutting resistance generated when cutting the first workpiece.

3. The machine tool according to claim 1 or 2, wherein the control unit detects the cutting resistance based on a load acting on the tool that cuts continuously from one of the first workpiece and the second workpiece to the other.

4. The machine tool according to claim 1 or 2, wherein the control unit determines the cutting resistance based on a load applied to a motor that drives the first spindle.

5. 5. The machine tool according to claim 1, further comprising: a second spindle arranged opposite to the first spindle and rotatably holding the second workpiece; and a guide bush arranged between the first spindle and the second spindle and concentric with the first spindle.

6. 6. The machine tool according to claim 5, wherein the control unit controls movement of at least one of the first spindle or the second spindle so that the first spindle and the second spindle move relatively closer to each other while rotating a first workpiece held by the first spindle and a second workpiece held by the second spindle, and presses a rear end portion of the second workpiece against a front end portion of the first workpiece to frictionally join them.

7. A method for controlling a machine tool including a first spindle that rotatably holds a first workpiece, a tool table on which a tool for cutting the first workpiece is mounted, a second spindle that is disposed opposite to the first spindle and rotatably holds a second workpiece having the same diameter as the first workpiece transferred from the first spindle, and a control unit that controls operations of the first spindle, the second spindle, and the tool table, a step of relatively moving the first spindle and the second spindle so as to approach each other while rotating the first spindle and the second spindle, and pressing a rear end portion of the second workpiece against a front end portion of a newly supplied first workpiece to perform friction welding; removing burrs generated at a joint portion between the second workpiece and the newly supplied first workpiece by the tool; calculating an amount of misalignment of the second workpiece relative to the first workpiece, which are joined together, based on a cutting resistance generated when the tool cuts the first workpiece or the second workpiece continuously from one to the other; a step of causing the control unit to cause the machine tool to perform an operation corresponding to the calculated amount of misalignment; A method for controlling a machine tool, comprising:

Images