Machine tool and machine tool control method

Abstract

To provide a machine tool and a control method of the machine tool, which automatically adjust a gap between a rotary guide bush and a bar material in the case of a structure in which an opening of the rotary guide bush is adjusted by an adjusting nut and the rotary guide bush synchronously rotates with a front face main spindle.SOLUTION: A rotary guide bush 140 includes an adjusting nut 145 which adjusts a size of a gap by rotating a guide bush body 144 when adjusting a gap between a bar material W and the guide bush body 144 and is screwed with the guide bush body 144. A control device 180 includes a guide bush opening determination section 181b which determines adjustment amount of the gap on the basis of a rotation angle of a front face main spindle 120 when rotating a back face main spindle 160 in a state that the back face main spindle 160 is held by the bar material W and a front face main spindle driving motor 123 is not excited.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a machine tool that adjusts the gap between a bar and a rotary guide bush, and a method for controlling the machine tool. [Background technology]

[0002] 2. Description of the Related Art Conventionally, machine tools have been known that include a guide bush that is disposed in front of a spindle and that supports and guides a bar held by the spindle. In order to process the bar material stably and with high processing accuracy, it is necessary to adjust the size of the gap between the bar material and the guide bush (also known as adjusting the opening of the guide bush), and there is known technology for automatically adjusting the opening of the guide bush (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 7-328804 Summary of the Invention [Problem to be solved by the invention]

[0004] The machine tool described in Patent Document 1 uses an adjustment nut (also called a draw bar) that is screwed onto the guide bush when adjusting the opening of the guide bush. In Patent Document 1, the guide bush does not rotate synchronously with the spindle. However, even in the case of a rotary guide bush in which the guide bush rotates synchronously with the spindle to avoid the bar material seizing on the guide bush and to prevent deterioration of the surface quality of the bar material, it is desirable to automatically adjust the gap between the rotary guide bush and the bar material in order to process the bar material stably and with high processing accuracy.

[0005] Therefore, the present invention solves the problems of the prior art as described above. Specifically, the object of the present invention is to provide a machine tool and a method for controlling the machine tool that automatically adjusts the gap between the rotary guide bush and the bar material when the opening of the rotary guide bush is adjusted by an adjusting nut and the rotary guide bush rotates synchronously with the front spindle. [Means for solving the problem]

[0006] The invention according to claim 1 comprises a front spindle that rotatably holds a bar material, a front spindle drive motor that rotationally drives the front spindle, an encoder that detects the rotation angle of the front spindle drive motor, a rotary guide bush that is installed on a guide bush support base in front of the front spindle and that supports the bar material that has advanced from the front spindle by allowing it to rotate about the rotation axis and move in the rotation axis direction, and that rotates synchronously with the front spindle, a back spindle that is disposed opposite the front spindle and that rotatably holds the bar material, a back spindle drive motor that rotationally drives the back spindle, and a control device that controls the operations of the front spindle and the back spindle. a guide bush body that supports the bar while allowing rotation about the rotation axis of the bar and movement in the direction of the rotation axis and is rotatable relative to the guide bush holder; and an adjustment nut that rotates the guide bush body to adjust the size of the gap when adjusting a gap between the bar and the guide bush body and that screws into the guide bush body, and the control device controls the front spindle when the back spindle holds the bar and rotates the back spindle in a state where the front spindle drive motor is not excited. Drive motor The above-mentioned problem is solved by providing a guide bush opening degree determining unit that determines the amount of adjustment of the gap based on the rotation angle of the guide bush.

[0007] The invention of claim 2 solves the above-mentioned problem by, in addition to the configuration of the machine tool described in claim 1, allowing the back spindle to detachably mount a holding jig that holds the bar stock.

[0008] The invention of claim 3 further solves the above-mentioned problem by, in addition to the configuration of the machine tool described in claim 1 or claim 2, attaching a rotating jig to the bar between the front spindle and the rotary guide bush, which engages with the adjusting nut of the rotary guide bush facing the front spindle and rotates the adjusting nut.

[0009] The invention according to claim 4 provides a machine tool comprising: a front spindle that rotatably holds a bar material; a front spindle drive motor that rotationally drives the front spindle; an encoder that detects the rotation angle of the front spindle drive motor; a rotary guide bush that is installed on a guide bush support base in front of the front spindle and supports the bar material that has advanced from the front spindle by allowing it to rotate about the rotation axis and move in the direction of the rotation axis and rotates synchronously with the front spindle; a back spindle that is arranged opposite the front spindle and rotatably holds the bar material; a back spindle drive motor that rotationally drives the back spindle; and a control device that controls the operations of the front spindle and the back spindle, wherein the rotary guide bush comprises a guide bush holder fixed to the guide bush support base; a guide bush main body that rotatably supports the bar material relative to the guide bush holder by allowing it to rotate about the rotation axis and move in the direction of the rotation axis; and an adjustment nut that rotates the guide bush main body to adjust the size of the gap when adjusting a gap between the bar material and the guide bush main body and that screws into the guide bush main body. A rotating jig that engages with the adjusting nut of the rotary guide bush facing the front main shaft and rotates the adjusting nut is attached to the bar material between the front main shaft and the rotary guide bush. A method for controlling a machine tool, comprising the steps of: holding the bar material with the back spindle; rotating the back spindle around a rotation axis; measuring, with the encoder, a rotation angle of the front spindle drive motor generated by rotating the back spindle; and rotating the front spindle measured by the encoder. Drive motor determining an adjustment amount of the gap based on the rotation angle; and rotating the back main shaft around a rotation axis so as to achieve the determined adjustment amount of the gap. The adjusting nut is rotated via a rotating jig attached to the bar. The aforementioned Guide bush body The above-mentioned problem is solved by including a step of rotating the image relative to the object. [Effects of the Invention]

[0010] According to the machine tool of the invention of claim 1, the control device controls the front spindle when the back spindle is rotated while holding the bar material with the back spindle and not exciting the front spindle drive motor. Drive motor Since the rotary guide bush has a guide bush opening determination unit that determines the amount of adjustment of the gap based on the rotation angle of the front spindle, fluctuations in the rotation angle of the front spindle, which is free to rotate when the back spindle holding the bar is driven to rotate, are based only on the rotation of the bar that accompanies the rotation of the back spindle, thereby increasing the signal-to-noise ratio compared to when the size of the gap between the rotary guide bush and the bar is adjusted based on the load on the back spindle drive motor when the back spindle holding the bar is driven to rotate by the back spindle drive motor, and in a structure in which the opening of the rotary guide bush is adjusted by an adjustment nut and the rotary guide bush rotates synchronously with the front spindle, the gap between the rotary guide bush and the bar can be automatically adjusted with high precision.

[0011] According to the machine tool of the invention of claim 2, in addition to the effects achieved by the machine tool of the invention of claim 1, the back spindle can freely attach and detach the holding jig that holds the bar stock, so the holding jig attached to the back spindle holds the bar stock.Therefore, even if the back spindle cannot directly hold the bar stock, the bar stock can be indirectly held by the back spindle by selecting a holding jig that corresponds to the bar stock.

[0012] According to the machine tool of the invention defined in claim 3, in addition to the effects achieved by the machine tool of the invention defined in claim 1 or claim 2, a rotating jig that engages with the adjusting nut of the rotary guide bush facing the front spindle and rotates this adjusting nut is attached to the bar material between the front spindle and the rotary guide bush, so that when the bar material is held by the back spindle and the rotating jig is engaged with the adjusting nut, the back spindle rotates the bar material, causing the adjusting nut of the rotary guide bush to rotate, and therefore the gap between the rotary guide bush and the bar material can be automatically adjusted with high precision.

[0013] According to the control method for a machine tool of the invention of claim 4, there are provided a step of measuring, by an encoder, the rotation angle of the front spindle drive motor generated by rotating the back spindle, and a step of measuring, by an encoder, the rotation angle of the front spindle drive motor generated by rotating the back spindle. Drive motor determining an adjustment amount of the gap based on the rotation angle; and rotating the rear main shaft around the rotation axis so as to achieve the determined adjustment amount of the gap. The adjusting nut is attached to the guide bush body via a rotating jig attached to the bar material. By including the step of rotating the rotary guide bush relative to the front spindle, fluctuations in the rotation angle of the front spindle, which is free to rotate when the back spindle holding the bar stock is driven to rotate, are based only on the rotation of the bar stock that accompanies the rotation of the back spindle, and therefore the signal-to-noise ratio is increased compared to when the size of the gap between the rotary guide bush and the bar stock is adjusted based on the load on the back spindle drive motor when the back spindle holding the bar stock is driven to rotate by the back spindle drive motor, and in the case of a structure in which the opening of the rotary guide bush is adjusted by an adjustment nut and the rotary guide bush rotates synchronously with the front spindle, the gap between the rotary guide bush and the bar stock can be automatically adjusted with high precision. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a schematic configuration diagram of an automatic lathe which is an embodiment of a machine tool according to the present invention; [Figure 2] FIG. 2 is a configuration diagram of a rotary guide bush, a front main spindle, and a rear main spindle. [Figure 3] FIG. 3 is a perspective view of the adjusting nut shown in FIG. 2. [Figure 4] FIG. 3 is a perspective view of the holding jig shown in FIG. 2. [Figure 5] FIG. 3 is a perspective view of the rotating jig shown in FIG. 2. [Figure 6A] 10 is a flowchart showing a procedure for adjusting the size of the gap between the bar and the rotary guide bush. [Figure 6B] 6B is a flowchart showing the preparation steps shown in FIG. 6A. [Figure 6C] 6B is a flowchart showing the gap adjusting process shown in FIG. 6A. [Figure 7A] Schematic diagram showing the bar inserted into the front spindle. [Figure 7B] Schematic diagram showing the state in which the bar material has been inserted up to the rotary guide bush. [Figure 7C] FIG. 10 is a schematic diagram showing a state in which the front spindle is advanced to engage the rotating jig with the adjusting nut. [Figure 8] FIG. 10 is a schematic diagram showing a state in which the rotation jig and the adjusting nut are disengaged from each other. [Figure 9] FIG. 9 is a schematic diagram of the rotating jig and the bar shown in FIG. 8 as seen from behind. [Figure 10A] FIG. 10 is a schematic diagram showing a state in which the rear spindle is retracted and the rotation jig and the adjustment nut are engaged with each other. [Figure 10B] 10 is a schematic diagram illustrating a process of adjusting the size of the gap between the bar material and the guide bush body by rotating the back main shaft. FIG. [Figure 11] FIG. 10 is a schematic configuration diagram of an automatic lathe which is a modified example of the machine tool according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] The present invention includes a front spindle that rotatably holds a bar material, a front spindle drive motor that rotationally drives the front spindle, an encoder that detects the rotation angle of the front spindle drive motor, a rotary guide bush that is installed on a guide bush support base in front of the front spindle and that supports the bar material that has advanced from the front spindle by allowing it to rotate around the rotation axis and move in the direction of the rotation axis, and that rotates synchronously with the front spindle, a back spindle that is arranged opposite the front spindle and that rotatably holds the bar material, a back spindle drive motor that rotationally drives the back spindle, and a control device that controls the operation of the front spindle and the back spindle. a rotary guide bush having a guide bush holder fixed to a guide bush support base, a guide bush body that is rotatable relative to the guide bush holder and supports the bar while allowing rotation about the rotation axis of the bar and movement in the direction of the rotation axis, and an adjustment nut that rotates the guide bush body to adjust the size of the gap when adjusting the gap between the bar and the guide bush body and that screws into the guide bush body, and wherein the control device controls the front spindle when the back spindle is rotated while holding the bar and the front spindle drive motor is not excited Drive motor The specific embodiment may be any as long as it has a guide bush opening determination unit that determines the amount of gap adjustment based on the rotation angle of the rotary guide bush and automatically adjusts the gap between the rotary guide bush and the rod.

[0016] The rotary guide bush includes a front spindle that rotatably holds the bar material, a front spindle drive motor that rotates and drives the front spindle, an encoder that detects the rotation angle of the front spindle drive motor, a rotary guide bush that is installed on a guide bush support base in front of the front spindle and that supports the bar material that has advanced from the front spindle by allowing it to rotate around the rotation axis and move in the direction of the rotation axis and that rotates synchronously with the front spindle, a back spindle that is arranged opposite the front spindle and that rotatably holds the bar material, a back spindle drive motor that rotates and drives the back spindle, and a control device that controls the operation of the front spindle and the back spindle, and the rotary guide bush includes a guide bush holder fixed to the guide bush support base, a guide bush main body that rotatably supports the bar material relative to the guide bush holder by allowing it to rotate around the rotation axis and move in the direction of the rotation axis, and an adjustment nut that screws into the guide bush main body and that adjusts the size of the gap when adjusting the gap between the bar material and the guide bush main body. A rotating jig that engages with the adjusting nut of the rotary guide bush facing the front spindle and rotates the adjusting nut is attached to the bar material between the front spindle and the rotary guide bush. A method for controlling a machine tool, comprising the steps of: holding a bar material with a back spindle; rotating the back spindle around a rotation axis; measuring the rotation angle of a front spindle drive motor generated by rotating the back spindle with an encoder; and rotating the front spindle measured by the encoder. Drive motor determining an adjustment amount of the gap based on the rotation angle; and rotating the rear main shaft around the rotation axis so as to achieve the determined adjustment amount of the gap. The adjusting nut is attached to the guide bush body via a rotating jig attached to the bar material. and rotating the rotary guide bush relative to the rod, thereby automatically adjusting the gap between the rotary guide bush and the rod material. [Example]

[0017] A machine tool 100 according to one embodiment of the present invention will now be described with reference to FIGS. 1 to 10B.

[0018] <1. Machine Tool Overview> First, an overview of a machine tool 100 will be described with reference to FIGS. FIG. 1 is a schematic diagram of an automatic lathe, which is an embodiment of a machine tool according to the present invention.

[0019] The machine tool 100 is an automatic lathe, and as shown in FIG. 1, is provided with a bed 110 that is placed on a floor F and has a rectangular shape in a plan view. Hereinafter, the direction perpendicular to the bed 110 is referred to as the "Y direction," the longitudinal direction of the bed 110 in plan view is referred to as the "Z direction," and the lateral direction of the bed 110 in plan view is referred to as the "X direction."

[0020] On the bed 110 are placed a front spindle 120 that rotatably holds the bar W, a front spindle feed mechanism 130 that feeds the front spindle 120 in a Z1 direction parallel to the Z direction, a rotary guide bush 140 that supports the bar W that has advanced from the front spindle 120 and allows it to rotate about the rotation axis L and move in the direction of the rotation axis L, a guide bush support base 150 that is installed in front of the front spindle 120 and supports the rotary guide bush 140, a back spindle 160 that is arranged opposite the front spindle 120 and the rotary guide bush 140 and rotatably holds the bar W, and a back spindle feed mechanism 170 that feeds the back spindle 160 in a Z2 direction parallel to the Z direction and an X2 direction parallel to the X direction.

[0021] Here, the front spindle 120 and the bar W can freely move forward and backward in the Z1 direction, and the "forward" of the front spindle 120 and the bar W means the direction in which the front spindle 120 and the bar W approach the back spindle 160, and the "rear" of the front spindle 120 and the bar W means the direction in which the front spindle 120 and the bar W move away from the back spindle 160. Furthermore, "forward" of the rotary guide bush 140 means the direction in which the rotary guide bush 140 approaches the rear main shaft 160, and "rear" of the rotary guide bush 140 means the direction in which the rotary guide bush 140 moves away from the rear main shaft 160. The rear main shaft 160 is freely movable forward and backward in the X2 direction as well as in the Z2 direction, and the "forward" of the rear main shaft 160 means the direction in which the rear main shaft 160 approaches the front main shaft 120, and the "rear" of the rear main shaft 160 means the direction in which the rear main shaft 160 moves away from the front main shaft 120.

[0022] The bar material W to be machined by the machine tool 100 is a long, round workpiece, which is supplied from the rear end of the front spindle 120 using a push rod of a bar feeder (not shown), and is supported by a rotary guide bush 140 via the front spindle 120 so as to be rotatable around the rotation axis L, and is sent toward the back spindle 160. A finger chuck for gripping the rear end of the bar W is provided at the tip of the pushing arrow of the bar feeder.

[0023] The machine tool 100 also includes a control device 180 that controls the operations of the front spindle 120 and the back spindle 160 .

[0024] <2. Components of machine tools> Next, each of the components of the machine tool 100 described above will be described in detail with reference to FIGS. 2 is a configuration diagram of the rotary guide bush, the front spindle, and the rear spindle, FIG. 3 is a perspective view of the adjusting nut shown in FIG. 2, FIG. 4 is a perspective view of the holding jig shown in FIG. 2, and FIG. 5 is a perspective view of the rotating jig shown in FIG. 2.

[0025] <2.1. Front spindle> As shown in FIG. 1, the front spindle 120 has a headstock 121 that is mounted on the front spindle feed mechanism 130 and is movable in the Z1 direction, a front spindle main body 122 that is rotatably supported by the headstock 121, a front spindle drive motor 123 that drives and rotates the front spindle main body 122, and an encoder 124 that detects the rotation angle of the front spindle drive motor 123.

[0026] The front spindle body 122 is supported by the headstock 121 with its axis in the Z1 direction shown in FIG. 1, and as shown in FIG. 2, can rotatably grip (hold) the bar W around the rotation axis L via the chuck 122a. The chuck 122 a is arranged concentrically with the front spindle body 122 and rotates integrally with the front spindle body 122 . That is, the rotation axis L of the bar W coincides with the rotation center of the front spindle 120 .

[0027] 1, a timing pulley 122b around which a timing belt V1 is wound is provided at the front end portion of the front main shaft body 122.

[0028] The front spindle drive motor 123 is a so-called "electric motor" that has a stator and a rotor, and generates a magnetic field when either one changes rotation, and generates driving force through the change in the magnetic field.

[0029] <2.2. Front spindle feed mechanism> The front spindle feed mechanism 130 has a Z1 rail 131 fixed to the bed 110 and extending in the Z1 direction, a Z1 slider 132 attached to the Z1 rail 131 and slidable along the Z1 direction, and a Z1 motor 133 that slides the Z1 slider 132. The headstock 121 of the front spindle 120 is installed on the Z1 slider 132.

[0030] The front spindle feed mechanism 130 is provided with a counter shaft 134 that is rotatable. The counter shaft 134 is fitted with a main shaft-side timing pulley 134a around which the timing belt V1 is wound, and a rotary guide bush-side timing pulley 134b around which the timing belt V2 is wound. Therefore, when the front spindle body 122 is rotationally driven by the front spindle drive motor 123, the counter shaft 134 rotates via the timing belt V1.

[0031] <2.3. Rotary guide bush> As shown in FIG. 1, the rotary guide bush 140 is inserted into a guide bush support base 150 having a rotary guide bush insertion hole 150 a concentric with the front main shaft 120 .

[0032] As shown in FIG. 2, the rotary guide bush 140 includes a hollow cylindrical guide bush holder 141 that is inserted into and fixed to a rotary guide bush insertion hole 150a of the guide bush support base 150, a guide bush sleeve 142 that is inserted into the guide bush holder 141, a bearing 143 that is disposed between the guide bush holder 141 and the guide bush sleeve 142 and supports the guide bush sleeve 142 rotatably relative to the guide bush holder 141, and a bearing 143 that is disposed between the guide bush holder 141 and the guide bush sleeve 142 and supports the guide bush sleeve 142 rotatably relative to the guide bush holder 141. The guide bush holder 141 has a cylindrical guide bush body 144 that is inserted inside, an adjustment nut 145 that screws into a male thread 144a formed on the rear end portion of the guide bush body 144, a timing pulley 146 that is inserted into the rear end side of the guide bush holder 141 and is rotatable relative to the guide bush holder 141, a retaining nut 147 that engages with the guide bush sleeve 142 to prevent the timing pulley 146 from coming off, and a flange 148 that is fixed to the guide bush support base 150 and prevents the timing pulley 146 from coming off.

[0033] The guide bush holder 141 has a hollow cylindrical guide bush holder main body 141a that is inserted into the rotary guide bush insertion hole 150a of the guide bush support base 150, and an annular bearing retainer 141b that is attached to the rear end side of the guide bush holder main body 141a and, together with the guide bush holder main body 141a, positions the bearing 143 in the front-to-rear direction.

[0034] The guide bush sleeve 142 has a front end portion formed on its inner periphery with a taper 142a whose inner diameter gradually decreases toward the rear. The guide bush sleeve 142 is also formed with a through-hole 142c in the radial direction, into which a setscrew 142b is threaded. Furthermore, a key 142d that engages with a timing pulley 146 is embedded in the outer periphery of the rear end portion of the guide bush sleeve 142.

[0035] As shown in FIG. 2, the guide bush body 144 supports and guides the bar W held by the front spindle 120 so as to allow rotation about the rotation axis L and movement in the direction of the rotation axis L. The guide bush body 144 has a front end portion formed with a slit 144b extending in the Z direction.

[0036] Further, on the outer periphery of the front end portion of this guide bush body 144, a taper 144c is formed, the outer diameter of which gradually decreases toward the rear, corresponding to the taper angle of the taper 142a of the guide bush sleeve 142. Behind this taper 144c, a groove 144d is formed extending rearward. The groove 144d is formed so as to gradually become deeper toward the rear, and extends until it reaches the male thread 144a.

[0037] Furthermore, a setscrew 142b threaded into a threaded through-hole 142c of the guide bush sleeve 142 is inserted into this groove 144d. Therefore, the setscrew 142b and the groove 144d engage, allowing the guide bush body 144 to move back and forth relative to the guide bush sleeve 142 only in the Z direction, and the guide bush body 144 can rotate together with the guide bush sleeve 142 around the rotation axis L. That is, the guide bush main body 144 becomes rotatable relative to the guide bush holder 141 when the setscrew 142b and the groove 144d are engaged with each other.

[0038] The adjusting nut 145 (also called a draw bar) is hollow and cylindrical, and is provided behind the guide bush main body 144 , and is rotatable relative to the guide bush sleeve 142 . As shown in FIG. 2, a female thread 145a of a predetermined pitch is formed on the inner periphery of the front end portion of this adjustment nut 145, and this female thread 145a is threadedly engaged with a male thread 144a formed on the rear end portion of the guide bush main body 144.

[0039] Therefore, by rotating the adjustment nut 145 around the rotation axis L, the main body of the guide bush main body 144 advances and retreats relative to the guide bush sleeve 142. When the guide bush body 144 retreats relative to the guide bush sleeve 142, the taper 144c is pushed by the taper 142a, and the front end portion of the guide bush body 144 is bent toward the bar W side by the slot 144b, thereby reducing the opening of the front end portion of the guide bush body 144. On the other hand, when the guide bush body 144 advances relative to the guide bush sleeve 142, the pressure from the taper 142a is released and the front end portion of the guide bush body 144 expands outward, increasing the opening of the front end portion of the guide bush body 144.

[0040] That is, the displacement amount of the guide bush main body 144 in this embodiment (the opening degree of the rotary guide bush 140, which is the same as the opening degree of the front end portion of the guide bush main body 144) is determined by the rotation amount of the adjusting nut 145. In other words, when adjusting the gap between the bar W and the guide bush main body 144, the adjusting nut 145 can rotate the guide bush main body 144 to adjust the size of the gap.

[0041] As shown in FIG. 3, the rear surface 145b of the adjusting nut 145 is formed with a plurality of (for example, three) engagement holes 145b1.

[0042] The timing pulley 146 is cylindrical and, as shown in FIG. 2, is rotatably inserted into the rear end side of the bearing holder 141b of the guide bush holder 141.

[0043] A key groove 146 a that engages with the key 142 d of the guide bush sleeve 142 is formed on the inner periphery of the front end portion of the timing pulley 146 . A belt positioning groove 146b is formed on the outer periphery of the timing pulley 146, and a timing belt V2 is looped around this belt positioning groove 146b.

[0044] Therefore, when the front main shaft body 122 rotates, the counter shaft 134 also rotates due to the timing belt V1, and the rotary guide bush side timing pulley 134b also rotates, so that the timing pulley 146 of the rotary guide bush 140 rotates via the timing belt V2, the guide bush sleeve 142 rotates via the key 142d, and the guide bush body 144 rotates via the set screw 142b. That is, the guide bush main body 144 rotates synchronously with the front main shaft 120 , that is, rotates around the rotation axis L at the same rotation speed as the front main shaft 120 .

[0045] The female thread formed on the inner periphery of the retaining nut 147 is threadedly engaged with the male thread formed on the outer periphery of the rear end portion of the guide bush sleeve 142 . The female thread of the retaining nut 147 and the male thread of the guide bush sleeve 142 are threadedly engaged to prevent the timing pulley 146 from slipping out rearward, as shown in FIG.

[0046] The flange 148 is an annular member, and is fixed to the guide bush support base 150 by a fixing bolt B, as shown in FIG.

[0047] <2.4. Guide bush support> The guide bush support base 150 is fixed to the bed 110 . As shown in FIG. 1, the guide bush support base 150 accommodates therein a rotary guide bush side timing pulley 134b attached to the tip of the counter shaft 134 of the front spindle feed mechanism 130.

[0048] Further, on the back spindle 160 side of the guide bush support base 150, a tool rest moving mechanism 151 on which a tool rest 152 is placed is provided. The tool rest moving mechanism 151 is capable of moving the tool rest 152 in the X direction and the Y direction. A blade 152a with its tip pointing toward the rotation axis L is attached to the blade rest 152. Therefore, by moving the front spindle 120 in the direction of the rotation axis L and moving the tool rest 152 in the X or Y direction, the bar W can be machined by the blade 152a.

[0049] <2.5. Back main axis> As shown in FIG. 1, the back spindle 160 has a headstock 161 that is mounted on the back spindle feed mechanism 170 and is movable in the Z2 and X2 directions, a back spindle main body 162 that is rotatably supported by the headstock 161, and a back spindle drive motor 163 that rotates and drives the back spindle main body 162.

[0050] The back spindle body 162 is supported by the spindle head 161 with its axis in the Z2 direction parallel to the Z1 direction shown in FIG. 1, and as shown in FIG. 2, is capable of rotatably gripping (holding) the bar W via a chuck 162a. The chuck 162 a is configured concentrically with the back spindle body 162 and is rotatable integrally with the back spindle body 162 .

[0051] As shown in FIG. 2, a holding jig 164 for holding the bar W is detachably attached to the chuck 162a. As shown in FIGS. 2 and 4, this holding jig 164 is made up of a C-shaped annular spindle mounting fixture 164a attached to the rear spindle body 162, a C-shaped annular bar holder 164b for holding the bar W, and a connecting bolt 164c for connecting the spindle mounting fixture 164a and the bar holder 164b, and is a C-shaped member when viewed from the front spindle 120 side.

[0052] As shown in FIG. 2, the spindle mounting fixture 164a has an inner diameter that is approximately equal to the outer diameter of the rear spindle body 162. As shown in FIG. 4, the spindle mounting fixture 164a is fastened to the rear spindle body 162 by inserting a fastening bolt 164d into a through hole formed in a direction perpendicular to the circumferential direction of the spindle mounting fixture 164a and screwing it into a screw hole facing the through hole. As a result, the spindle mounting fixture 164a rotates integrally with the rear spindle body 162.

[0053] The bar holder 164b has a through hole extending in the Z2 direction. A coupling bolt 164c is inserted into this through hole and threadedly engages with a screw hole formed in a front surface 164a1 of the spindle mounting fixture 164a, thereby forming the bar holder 164b integral with the spindle mounting fixture 164a. Furthermore, since the bar holder 164b is a C-ring, the inner diameter φ of the bar holder 164b is variable, as shown in FIG. The inner diameter of this bar holder 164b is adjusted by inserting an adjustment bolt 164e into a through hole formed in a direction perpendicular to the circumferential direction of the bar holder 164b and screwing it into a screw hole 164b1 facing this through hole.

[0054] <2.6. Back spindle feed mechanism> The back spindle feed mechanism 170 is made up of an X2 direction feed structure 171 placed on the bed 110 and a Z2 direction feed structure 172 placed on the X2 direction feed structure 171, as shown in FIG.

[0055] The X2 direction feed structure 171 is fixed to the bed 110 and extends in the X2 direction. a And this X2 Rail 171 a X2 slider 17 is attached to the X2 axis and slides freely along the X2 direction. 1b And this X2 Slider 17 1b Sliding X2 Motor 17 1c It has the following features.

[0056] The Z2 direction feed structure 172 is connected to the X2 slider 17 1b Z2 rail 17 is fixed to the 2aAnd this Z2 Rail 17 2a Z2 slider 172 is attached to the b And this Z2 slider 172 b Slide Z2 motor 17 2c It has the following features. Z2 Slider 172 b Above it, a headstock 161 of the back spindle 160 is installed.

[0057] 2.7. Control Devices The rotation of the front spindle 120 and the back spindle 160 and the movement of the front spindle feed mechanism 130 and the back spindle feed mechanism 170 are controlled by a control device 180. The control device 180 includes a control unit 181 and an input unit 182, which are connected via a bus.

[0058] The control unit 181 comprises a CPU, memory, etc., and loads various programs and data stored in, for example, a ROM into a RAM and executes the programs. That is, the operation of machine tool 100 is controlled by a program loaded into control unit 181. The rotation of the front spindle 120 and the back spindle 160, the movement of the front spindle feed mechanism 130 and the back spindle feed mechanism 170, etc. can be set by a program or by input to the input unit 182.

[0059] The control unit 181 also includes a motor control section 181a, a guide bush opening degree determination section 181b, and a data table 181c. The motor control unit 181a controls the operation of the front spindle drive motor 123, the back spindle drive motor 163, and the Z2 motor 172c, for example, when adjusting the gap between the bar W and the rotary guide bush 140 (i.e., the guide bush main body 144). The guide bush opening degree determination unit 181b determines the adjustment amount of the gap between the bar W and the guide bush main body 144 based on the rotation angle of the front spindle drive motor 123 measured by the encoder 124 and by referring to the data table 181c. More specifically, the guide bush opening determination unit 181b estimates the size of the gap between the bar W and the guide bush main body 144 based on the rotation angle of the front main shaft drive motor 123, calculates the difference between this estimated gap size and the optimal gap size, and determines the amount of rotation of the back main shaft 160 based on this difference, i.e., the adjustment amount of the gap between the bar W and the guide bush main body 144. The data table 181c stores data relating to the rotation angle of the front spindle drive motor 123 and the size of the gap between the bar W and the guide bush main body 144, depending on the material, diameter, etc. of the bar W.

[0060] <2.8. Rotating Jig> As shown in FIG. 2, the machine tool 100 is provided with a rotating jig 190 that rotates an adjusting nut 145 that adjusts the size of the gap between the bar W and the guide bush main body 144.

[0061] The rotating jig 190 has a C-shaped ring shape as shown in FIG. 5, and the bar material W is inserted therein as shown in FIG. The rotating jig 190 has a variable inner diameter, similar to the bar holder 164b. The inner diameter of the rotating jig 190 is adjusted by inserting a tightening bolt 191 into a through hole formed in a direction perpendicular to the circumferential direction of the rotating jig 190 and screwing it into a screw hole 190a facing the through hole.

[0062] Further, an engagement pin 192 that engages with an engagement hole 145b1 of the adjustment nut 145 of the rotary guide bush 140 is disposed on a front surface 190b of the rotation jig 190.

[0063] <3. Gap adjustment procedure> Next, based on Figures 1 to 10B, an example of a procedure for adjusting the size of the gap between the bar W and the rotary guide bush 140, i.e., the gap between the bar W and the guide bush main body 144, using a machine tool 100 which is one embodiment of the present invention will be described. 6A is a flowchart showing the procedure for adjusting the size of the gap between the bar and the rotary guide bush, FIG. 6B is a flowchart showing the preparation process shown in FIG. 6A, FIG. 6C is a flowchart showing the gap adjustment process shown in FIG. 6A, FIG. 7A is a schematic diagram showing the state in which the bar has been inserted into the front spindle, FIG. 7B is a schematic diagram showing the state in which the bar has been inserted up to the rotary guide bush, FIG. 7C is a schematic diagram showing the state in which the front spindle has been advanced to engage the rotating jig with the adjusting nut, FIG. 8 is a schematic diagram showing the state in which the engagement between the rotating jig and the adjusting nut has been released, FIG. 9 is a schematic diagram of the rotating jig and bar shown in FIG. 8 as seen from the rear, FIG. 10A is a schematic diagram showing the state in which the rear spindle has been retreated to engage the rotating jig with the adjusting nut, and FIG. 10B is a schematic diagram explaining the process of adjusting the size of the gap between the bar and the guide bush main body by rotating the rear spindle. The procedure described below is merely an example, and the adjustment of the size of the gap between the bar W and the guide bush main body 144 is not limited to the following procedure.

[0064] <3.1. Preparation process> (Step S10) First, machine tool 100 performs the preparation step shown in FIG. 6B.

[0065] (Step S11) In the preparation step, the bar W is inserted from the rear end of the front spindle 120 using a push arrow of a bar feeder (not shown) (see FIG. 7A), and is then inserted through the rotating jig 190 and the rotary guide bush 140 in that order. At this time, the rotation center of the back main shaft 160 is aligned with the rotation center of the front main shaft 120 and the rotation center of the rotary guide bush 140 .

[0066] (Step S12) Next, as shown in FIG. 7B, the rotating jig 190 is fastened and fixed to the bar W, and the rotating jig 190 and the bar W are rotated around the rotation axis L as a unit. When the rotating jig 190 is fixed to the bar W, the distance D1 from the rotating jig 190 to the adjusting nut 145 of the rotary guide bush 140 is longer than the distance D2 from the bar W to the holding jig 164 of the back spindle 160. long It has become.

[0067] (Step S13) Next, the bar W is pushed out until the engaging pin 192 of the rotating jig 190 is inserted into the engaging hole 145 b 1 of the adjusting nut 145 of the rotary guide bush 140 . When the engagement pin 192 of the rotation jig 190 is inserted into the engagement hole 145b1 of the adjustment nut 145 of the rotary guide bush 140, the orientation of the adjustment nut 145, that is, the orientation of the guide bush main body 144, is set to a predetermined orientation. Furthermore, when the engagement pin 192 of the rotating jig 190 is inserted into the engagement hole 145b1 of the adjusting nut 145 of the rotary guide bush 140, the distance D1 from the rotating jig 190 to the adjusting nut 145 of the rotary guide bush 140 becomes shorter than the distance D2 from the bar W to the holding jig 164 of the back spindle 160. long Therefore, if the inner diameter φ of the holding jig 164 of the back spindle 160 is made sufficiently large, the bar W will be inserted into the holding jig 164 of the back spindle 160 as shown in FIG. 7C.

[0068] When pushing out the bar W, if the positions of the engagement hole 145b1 of the adjusting nut 145 and the engagement pin 192 of the rotating jig 190 are misaligned in the rotational direction, the bar W (i.e., the front spindle 120 holding the bar W) is rotated until the engagement hole 145b1 of the adjusting nut 145 and the engagement pin 192 of the rotating jig 190 are directly facing each other.

[0069] (Step S14) Next, in this state, the holding jig 164 is fastened to the bar W by the adjustment bolt 164e of the holding jig 164 of the back spindle 160, and the bar W is gripped (held) by the back spindle 160.

[0070] (Step S15) Next, the front spindle drive motor 123 of the front spindle 120, which is an electric motor, is turned off, and the back spindle 160 is advanced toward the rotary guide bush 140 until the rotating jig 190 is released from the adjusting nut 145, resulting in the state shown in Figure 8.

[0071] <3.2. Inspection process> (Step S20) Next, in this state, the rear main shaft 160 is rotated in a predetermined direction by a predetermined angle. That is, as shown in FIG. 9, the back main shaft 160 is rotated to rotate the bar W by a predetermined angle θ from the reference angular position P to an angular position P1.

[0072] (Step S21) Here, when the excitation of the front spindle drive motor 123 is turned off, the rotation of the timing pulley 146 of the rotary guide bush 140 can rotate the front spindle drive motor 123 of the front spindle 120 via the timing belts V1 and V2.

[0073] Therefore, as described above, if the gap between the bar W and the guide bush main body 144 is narrow when the bar W rotates by a predetermined angle θ from the reference angular position P to the angular position P1, the bar W may come into contact with the guide bush main body 144, and this contact with the bar W may cause the guide bush main body 144 to rotate together with the bar W. As the guide bush body 144 rotates, the guide bush sleeve 142, which is integrated with the guide bush body 144 by a set screw 142b, rotates, and the timing pulley 146, which engages with a key 142d embedded in the guide bush sleeve 142, rotates. The rotation of this timing pulley 146 is transmitted from the timing belt V2 to the counter shaft 134, from the counter shaft 134 to the timing belt V1, from the timing belt V1 to the front main shaft body 122 of the front main shaft 120, and from the front main shaft body 122 to the front main shaft drive motor 123, causing the front main shaft drive motor 123 to rotate.

[0074] Conversely, if the gap between the rod W and the guide bush main body 144 is too large when the rod W rotates by a predetermined angle θ from the reference angle position P to the angle position P1, the rod W and the guide bush main body 144 may not come into contact with each other, and the guide bush main body 144 may not rotate.

[0075] Therefore, in step S21, it is determined whether the rotation angle of the front spindle drive motor 123 is within a predetermined angle range.

[0076] If the rotation angle of the front spindle drive motor 123 is within a predetermined angle range, the size of the gap between the bar W and the guide bush main body 144 is determined to be the optimal gap size, and adjustment of the size of the gap between the bar W and the guide bush main body 144 is terminated.

[0077] On the other hand, if the rotation angle of the front spindle drive motor 123 is below the lower limit of the specified angle range, the size of the gap between the bar W and the guide bush main body 144 is too large, so it is necessary to adjust the size of the gap between the bar W and the guide bush main body 144, and proceed to step S22, where the size of the gap between the bar W and the guide bush main body 144 is adjusted. Furthermore, if the rotation angle of the front spindle drive motor 123 exceeds the upper limit of the specified angle range, the size of the gap between the bar W and the guide bush main body 144 is too small, so it is necessary to adjust the size of the gap between the bar W and the guide bush main body 144, and the process proceeds to step S22, where the size of the gap between the bar W and the guide bush main body 144 is adjusted.

[0078] (Step S22) First, the back spindle 160 is rotated to rotate the bar W from the angular position P1 back to the reference angular position P (that is, the rotation is reverse to that in step S20). Thereafter, the process proceeds to step S30, where the size of the gap between the bar W and the guide bush main body 144 is adjusted.

[0079] <3.3. Gap adjustment process> (Step S30) Next, the steps of the gap adjusting process shown in FIG. 6C are carried out.

[0080] (Step S31) First, the rear main shaft 160 is moved backward until the rotating jig 190 is inserted into the adjusting nut 145 of the rotary guide bush 140, as shown in FIG. 10A.

[0081] (Step S32) Next, the front spindle drive motor 123 is excited. As a result, a holding torque acts on the front spindle drive motor 123, and the effect of this holding torque is exerted on the timing pulley 146 of the rotary guide bush 140, so that even if an attempt is made to rotate the timing pulley 146, it will not rotate.

[0082] (Step S33) In this state, as shown in FIG. 10B, with the bar W held by the back spindle 160, the back spindle 160 is rotated by a predetermined amount in a predetermined direction based on the output result from the guide bush opening degree determination unit 181b. The rotation of the back spindle 160 rotates the bar W, and the rotation jig 190 fixed to the bar W rotates in a predetermined direction by a predetermined amount.

[0083] Here, since the timing pulley 146 does not rotate, the guide bush sleeve 142 engaged with the timing pulley 146 by the key 142d and the guide bush body 144 engaged with the guide bush sleeve 142 by the set screw 142b do not rotate either. However, when the rotating jig 190 rotates, the adjusting nut 145 engaged with the rotating jig 190 rotates, and since the adjusting nut 145 cannot move in the Z direction due to the guide bush sleeve 142 and the rotating jig 190, the guide bush main body 144 threadedly engaged with this adjusting nut 145 moves back and forth in the Z direction relative to the guide bush sleeve 142 and the adjusting nut 145 in accordance with the rotation direction of the adjusting nut 145, and the size of the gap between the bar W and the guide bush main body 144 is adjusted.

[0084] (Step S34) After the size of the gap between the bar W and the guide bush body 144 has changed by a predetermined amount, the back spindle 160 is advanced to disengage the rotating jig 190 from the adjustment nut 145 of the rotary guide bush 140, and the process returns to step S20.

[0085] Thereafter, the above steps are repeated as appropriate until the rotation angle of the front spindle drive motor 123 falls within a predetermined angle range.

[0086] <4. Effects of Machine Tool 100> According to the machine tool 100 described above, when the back spindle 160 holding the bar W is driven to rotate, the fluctuation in the rotation angle of the front spindle 120, which is freely rotatable, is based only on the rotation of the bar W that accompanies the rotation of the back spindle 160. Therefore, the signal-to-noise ratio is increased compared to when the size of the gap between the rotary guide bush and the bar is adjusted based on the load on the back spindle drive motor when the back spindle holding the bar is driven to rotate by the back spindle drive motor. In addition, when the opening of the rotary guide bush 140 is adjusted by the adjustment nut 145 and the rotary guide bush 140 rotates synchronously with the front spindle 120, the gap between the rotary guide bush 140 and the bar W can be automatically adjusted with high precision.

[0087] Furthermore, since the rear spindle 160 can detachably mount the holding jig 164 that holds the bar W, the holding jig 164 attached to the rear spindle 160 holds the bar W. Therefore, even if the rear spindle 160 cannot directly hold the bar W, the bar W can be indirectly held by the rear spindle 160 by selecting the holding jig 164 that corresponds to the bar W.

[0088] Furthermore, a rotating jig 190 that engages with the adjusting nut 145 of the rotary guide bush 140 facing the front main shaft 120 and rotates this adjusting nut 145 is attached to the bar W between the front main shaft 120 and the rotary guide bush 140.With the bar W held by the back main shaft 160 and the rotating jig 190 engaged with the adjusting nut 145, the back main shaft 160 rotates the bar W, causing the adjusting nut 145 of the rotary guide bush 140 to rotate, and therefore the gap between the rotary guide bush 140 and the bar W can be automatically adjusted with high precision.

[0089] <Modification> Although the machine tool according to one embodiment of the present invention has been described above, the machine tool according to the present invention is not limited to the machine tool according to the above-described embodiment.

[0090] For example, in the above-described embodiment, the front spindle drive motor 123 is mounted on the headstock 121, but the front spindle drive motor does not have to be provided on the headstock, and may be mounted on a bed, for example, and the front spindle main body may be driven to rotate via a transmission mechanism. The same applies to the rear spindle drive motor.

[0091] For example, in the above-described embodiment, an example was given in which a timing belt was used to synchronize the rotation of the front main shaft 120 and the rotary guide bush 140, but the present invention is not limited to this example, and any method may be used as long as the front main shaft 120 and the rotary guide bush 140 are structurally connected to each other and rotate synchronously.

[0092] Furthermore, as described below, the front main shaft 120 and the rotary guide bush 140 may be electrically connected to each other so that the front main shaft 120 and the rotary guide bush 140 rotate synchronously.

[0093] That is, as shown in FIG. 11, which is a schematic diagram of an automatic lathe that is a modified example of the machine tool according to the present invention, machine tool 100A, which is a modified example of the present invention, does not have encoder 124 and counter shaft 134 as in machine tool 100 described above, but instead has rotary guide bush drive motor 149 on bed 110 for rotating guide bush main body 144 of rotary guide bush 140, and timing belt V2 is wound around a timing pulley provided at the tip of this rotary guide bush drive motor 149. The rotary guide bush drive motor 149 is an electric motor similar to the front spindle drive motor 123, and has an encoder 149a that detects the rotation angle of the rotary guide bush drive motor 149.

[0094] Furthermore, the motor control section 181 a of the control device 180 controls not only the operation of the front spindle drive motor 123 but also the operation of the rotary guide bush drive motor 149 . In this modified example, the motor control unit 181a synchronizes the rotational drive of the front spindle drive motor 123 and the rotational drive of the rotary guide bush drive motor 149.

[0095] In this machine tool 100A, the size of the gap between the bar W and the rotary guide bush 140 is adjusted by detecting the rotation angle of the rotary guide bush drive motor 149 rather than the front spindle drive motor 123. The procedure for adjusting the size of the gap between the bar material W and the rotary guide bush 140 is the same as the procedure for adjusting the size of the gap between the bar material W and the rotary guide bush 140 by the machine tool 100 described above, except that the object to be detected is the rotation angle of the rotary guide bush drive motor 149, and the object to be excited in step S32 is the rotary guide bush drive motor 149.

[0096] According to the machine tool 100A configured in this manner, the back spindle 160 holds the bar material W, and the back spindle 160 is rotated in a state where the rotary guide bush drive motor 149 and the front spindle drive motor 123 are not excited. This includes the guide bush opening degree determination unit 181b, which determines the amount of gap adjustment based on the rotation angle of the rotary guide bush drive motor 149. When the back spindle 160 holding the bar material W is rotated, the fluctuation in the rotation angle of the rotary guide bush drive motor 149, which is rotatable, is adjusted based on the amount of gap adjustment of the back spindle 160. Since this is based solely on the rotation of the bar W accompanying the rotational drive, the signal-to-noise ratio is higher than when the size of the gap between the rotary guide bush and the bar is adjusted based on the load on the back spindle drive motor when the back spindle holding the bar W is rotated by the back spindle drive motor, and in the case of a structure in which the opening of the rotary guide bush 140 is adjusted by the adjustment nut 145 and the rotary guide bush 140 rotates synchronously with the front spindle 120, the gap between the rotary guide bush 140 and the bar W can be automatically adjusted with high precision using a simple structure. [Explanation of symbols]

[0097] 100... Machine tools 100A... Machine tool 110 Bed 120...Front spindle 121 ... Headstock 122...Front spindle body 122a ··· Chuck 122b Timing pulley 123 Front spindle drive motor 124 ··· Encoder 130 Front spindle feed mechanism 131 Z1 rail 132 ··· Z1 Slider 133 Z1 motor 134 Counter shaft 134a ··· Main shaft timing pulley 134b Rotary guide bush side timing pulley 140 Rotary guide bush 141 Guide bush holder 141a Guide bush holder body 141b Bearing holder 142 Guide bush sleeve 142a ··· Tapered 142b Set screw 142c ··· Through-hole screw hole 142d ··· Key 143 Bearing 144 Guide bush body 144a Male thread 144b ··· Sliding 144c ··· Tapered 144d...groove 145 Adjustment nut 145a Female thread 145b... Rear 145b1... Engagement hole 146 Timing pulley 146a Keyway 146b Belt positioning groove 147 Locking nut 148 ··· flange 149 Rotary guide bush drive motor 149a Encoder 150 Guide bush support base 150a Rotary guide bush insertion hole 151 Tool post moving mechanism 152 Tool rest 152a ··· Blade 160... Rear spindle 161 ... Headstock 162... Rear spindle body 162a ··· Chuck 163 Rear spindle drive motor 164 ··· Holding jig 164a... Spindle attachment 164a1... Front 164b ··· Material holder 164b1··· Screw hole 164c ··· Connecting bolt 164d ··· Fastening bolt 164e Adjustment bolt 170 Back spindle feed mechanism 171 ··· X2 direction feed structure 171a ··· X2 rail 171b ··· X2 slider 171c ··· X2 motor 172 ··· Z2 direction feed structure 172a Z2 rail 172b ··· Z2 slider 172c Z2 motor 180 Control device 181 Control Unit 181a Motor control unit 181b Guide bush opening determination section 181c Data Table 182 Input Unit 190 Rotating jig 190a ··· Screw hole 190b...Front 191 ··· Tightening bolt 192 Engagement pin W ··· Bar material F...Floor surface L Rotation axis φ: Inner diameter of the bar holder V1, V2... timing belt D1: Distance from the rotating jig to the adjusting nut D2: Distance from the bar to the holding jig B Fixing bolt P... Reference angle position

Claims

1. a front spindle that rotatably holds the bar material; a front spindle drive motor that rotates the front spindle; an encoder for detecting the rotation angle of the front spindle drive motor; a rotary guide bush that is installed on a guide bush support base in front of the front spindle, supports the bar material that has advanced from the front spindle by allowing the bar material to rotate about the rotation axis and move in the rotation axis direction, and rotates synchronously with the front spindle; a back spindle disposed opposite the front spindle and rotatably holding the bar; a back spindle drive motor that rotates the back spindle; A machine tool including a control device that controls operations of the front spindle and the back spindle, the rotary guide bush comprises a guide bush holder fixed to the guide bush support base, a guide bush body that is rotatable relative to the guide bush holder and supports the rod while allowing the rod to rotate about the rotation axis and move in the direction of the rotation axis, and an adjustment nut that rotates the guide bush body to adjust the size of the gap when adjusting a gap between the rod and the guide bush body and that screws into the guide bush body, the control device has a guide bush opening determination unit that determines an adjustment amount of the gap based on a rotation angle of the front spindle drive motor when the back spindle holds the bar and rotates in a state where the front spindle drive motor is not excited.

2. 2. The machine tool according to claim 1, wherein a holding jig for holding the bar material is detachably attached to the back spindle.

3. 3. The machine tool according to claim 1, wherein a rotating jig that engages with an adjusting nut of the rotary guide bush facing the front spindle to rotate the adjusting nut is attached to the bar between the front spindle and the rotary guide bush.

4. the machine includes a front spindle that rotatably holds a bar material, a front spindle drive motor that rotationally drives the front spindle, an encoder that detects the rotation angle of the front spindle drive motor, a rotary guide bush that is installed on a guide bush support base in front of the front spindle, that supports the bar material that has advanced from the front spindle by allowing it to rotate about the rotation axis and move in the direction of the rotation axis, and that rotates synchronously with the front spindle, a back spindle that is disposed opposite the front spindle and rotatably holds the bar material, a back spindle drive motor that rotationally drives the back spindle, and a control device that controls the operations of the front spindle and the back spindle, the rotary guide bush comprises a guide bush holder fixed to the guide bush support base, a guide bush body that is rotatable relative to the guide bush holder and supports the rod while allowing the rod to rotate about the rotation axis and move in the direction of the rotation axis, and an adjustment nut that rotates the guide bush body to adjust the size of the gap when adjusting a gap between the rod and the guide bush body and that screws into the guide bush body, A method for controlling a machine tool in which a rotating jig that engages with an adjusting nut of the rotary guide bush facing the front spindle and rotates the adjusting nut is attached to the bar material between the front spindle and the rotary guide bush, holding the bar material with the back spindle; rotating the back spindle around a rotation axis; measuring a rotation angle of the front spindle drive motor generated by rotating the back spindle with the encoder; determining an adjustment amount of the gap based on a rotation angle of the front spindle drive motor measured by the encoder; a step of rotating the rear spindle around a rotation axis to rotate the adjustment nut relative to the guide bush body via a rotation jig attached to the bar material so as to achieve the determined adjustment amount of the gap; A method for controlling a machine tool, comprising:

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