JP2014117785A - Machine tool and machine tool control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mechanism for preventing a machining failure and a damage to a tool due to a difference between an actual size of a workpiece and a size assumed in a machining program by appropriately grasping the size of the workpiece in a state of attaching the workpiece on a workbench.SOLUTION: A machine tool: acquires a size of a workpiece mounted on a table; drives a main shaft to be closer to the workpiece mounted on the table according to the acquired size of the workpiece; controls machining of the workpiece by determining that an actual size of the workpiece is larger than the acquired size of the workpiece in a case of step-out of drive means; and controls the machining to the workpiece by determining that the actual size of the workpiece is equal to or smaller than the acquired size of the workpiece in a case of no step-out of the drive means.

Description

  The present invention relates to a machine tool for detecting a workpiece size and a control method thereof.

  In machining a workpiece by a machine tool, for example, machining a curved mold surface having a three-dimensional shape, the workpiece machining state is detected by measuring the three-dimensional shape dimension of the workpiece during the workpiece machining process, It is known to grasp the processing progress and processing accuracy up to the shape dimension. In the measurement of the three-dimensional shape and dimension of the work in this case, the work is carried into the three-dimensional measuring machine outside the machine tool and measured. This complicates the setting of the workpiece on the measuring machine, and when machining the workpiece again after the measurement, there is a disadvantage that it takes time to reset the workpiece on the machine tool. Therefore, a work head that is still mounted on the table of the machine tool is mounted with a tool changer or the like on the spindle of the machine tool with a tool for replacing the tool. It has also been proposed as an efficient method to directly measure the shape and dimension of the workpiece as it is mounted on it.

  For example, Patent Document 1 proposes a method that uses a position detection sensor to detect a machining position and machining accuracy of a workpiece. The position detection sensor includes a rod-shaped contact probe. When the contact probe that contacts the object to be measured is displaced in the X direction, the Y direction, the Z direction, or the direction in which they are combined, the rear end of the contact probe is It is displaced in the Z direction and the switch is pressed. Thereby, it is detected that the object to be measured exists at the contacted position.

  Further, Patent Document 2 has a spindle head that rotatably supports the spindle in a non-contact manner. A contact attached to the spindle is brought into contact with the workpiece, and the spindle head is relatively moved along the shape of the workpiece. Techniques to make it have been proposed. Specifically, since the spindle is supported in a non-contact manner, the spindle moves relative to the spindle head, and the displacement of the spindle can be detected to measure the shape of the workpiece.

JP 09-264705 A JP 2000-176793 A

  However, the above prior art has the following problems. For example, there are problems that the position detection sensor is expensive and that the use of the contact probe described above requires setup time in order to hold the contact probe on the main shaft. In addition, the spindle head that supports the spindle in a non-contact and rotatable manner requires a special mechanical structure such as a sliding bearing, a hydrostatic bearing, and a magnetic bearing, and a contact is required to contact the workpiece. There is a problem of becoming.

  The present invention has been made in view of the above-mentioned problems, and by properly grasping the size of a work in a state where it is mounted on a workbench, a machining failure or tool due to a difference from the size assumed in the machining program. The purpose is to provide a mechanism to prevent the damage of the machine.

  In order to achieve the above object, the present invention provides a machine tool, a spindle for rotating an attached tool, a table for attaching a workpiece to be machined by a tool attached to the spindle, and a table mounted on the table. An acquisition means for acquiring the size of the workpiece placed; a driving means for driving the spindle in the vicinity of the workpiece placed on the table according to the size of the workpiece acquired by the acquisition means; and If the actual size of the workpiece is larger than the size of the workpiece acquired by the acquisition means, the work on the workpiece is controlled, and if the drive means does not step out, Control the work on the workpiece as if the actual size of the workpiece is less than or equal to the size of the workpiece acquired by the acquisition means Characterized in that it comprises a that control means.

  Further, the present invention is a machine tool, wherein a spindle that rotates an attached tool, a table that attaches a workpiece to be machined by the tool attached to the spindle, and a size of the workpiece placed on the table Acquisition means for acquiring the driving means, driving means for driving the table according to the size of the work acquired by the acquisition means, and moving the work placed on the table in the vicinity of the spindle, and the driving means In the case of step out, when the actual size of the work is larger than the size of the work acquired by the acquisition means, the work on the work is controlled, and when the drive means does not step out, When the actual size of the workpiece is equal to or smaller than the size of the workpiece acquired by the acquisition means, Characterized in that it comprises a Gosuru control means.

  Further, the present invention is a method for controlling a machine tool comprising: a spindle that rotates an attached tool; and a table that attaches a workpiece to be machined by the tool attached to the spindle, and is placed on the table An acquisition step of acquiring a size of the workpiece to be performed, a driving step of driving the spindle in the vicinity of the workpiece placed on the table according to the size of the workpiece acquired in the acquisition step, and a step-out in the driving step If the actual size of the workpiece is larger than the size of the workpiece acquired in the acquisition step, the work on the workpiece is controlled and no step-out occurs in the driving step. The actual size of the workpiece is the size of the workpiece obtained in the obtaining step. And executes a control step of controlling the machine tool relative to the workpiece as if it is less.

  Further, the present invention is a method for controlling a machine tool comprising: a spindle that rotates an attached tool; and a table that attaches a workpiece to be machined by the tool attached to the spindle, and is placed on the table An acquisition step of acquiring a size of the workpiece to be performed; a driving step of driving the table according to the size of the workpiece acquired in the acquisition step and moving the workpiece placed on the table in the vicinity of the spindle; If a step-out occurs in the driving step, the work on the workpiece is controlled as if the actual size of the workpiece is larger than the size of the workpiece acquired in the acquiring step, and the step-out occurs in the driving step. In the case where no occurrence occurred, the actual size of the workpiece is And executes a control step of controlling the machine tool relative to the workpiece as if obtained is equal to or less than the size of the workpiece.

  ADVANTAGE OF THE INVENTION According to this invention, the mechanism which prevents the failure of the process and the failure | damage of a tool by differing from the size assumed by the process program can be provided by grasping | ascertaining the size of a workpiece | work suitably in the state with which it mounted on the work bench | platform.

The perspective view of the machine tool which concerns on this embodiment. The figure which shows an example of the control structure of the machine tool which concerns on this embodiment. The flowchart which detects the workpiece | work size (height direction) which concerns on this embodiment. The flowchart which detects the workpiece | work size when the height which concerns on this embodiment differs in some places. The flowchart which detects the workpiece | work size (width direction) which concerns on this embodiment. The flowchart which detects the workpiece | work size (depth direction) which concerns on this embodiment.

  An embodiment of the present invention is shown below. The individual embodiments described below will help to understand various concepts, such as superordinate concepts, intermediate concepts and subordinate concepts of the present invention. Further, the technical scope of the present invention is determined by the scope of the claims, and is not limited by the following individual embodiments.

<Configuration of machine tool>
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. First, with reference to FIG. 1, the structure of the machine tool 1 which concerns on embodiment of this invention is demonstrated. FIG. 1 shows a state where no tool is provided. The machine tool 1 according to this embodiment includes a frame body 11 and a pair of two X-axis shafts 22 bridged by a pair of side walls provided perpendicular to the mounting surface constituting the frame body 11. The X-axis shaft 22 guides the main shaft 50 in the horizontal direction with respect to the mounting surface of the machine tool 1. The spindle 50 rotates the attached tool to perform a work on the workpiece.

  The direction parallel to the X-axis shaft 22 is defined as the X-axis in the embodiment of the present invention, the horizontal direction with respect to the mounting surface of the machine tool 1, and the direction perpendicular to the X-axis with respect to the Y-axis, X-axis, and Y-axis. The perpendicular direction is called the Z axis. An X-axis drive motor (not shown) drives an X-axis drive shaft 23 provided parallel to the X-axis shaft 22, and the X-axis slider 20 assembled to the pair of X-axis shaft 22 and the X-axis drive shaft 23 moves. To do. As the X-axis slider 20 moves, the main shaft 50 assembled to the X-axis slider 20 moves in the horizontal direction with respect to the mounting surface of the machine tool 1.

  The Y-axis shaft 27 is provided perpendicular to the X-axis, and a Y-axis drive motor (not shown) drives a Y-axis drive shaft 29 provided in parallel to the Y-axis shaft 27. As a result, the Y-axis slider 25 assembled to the pair of Y-axis shaft 27 and the Y-axis drive shaft 29 moves. A pair of magazine shafts 67 are provided in parallel with the Y-axis shaft 27, a magazine holding member 69 is assembled to the magazine shaft 67, is connected to the Y-axis slider 25, and moves as the Y-axis moves. By connecting the magazine holding member to the Y-axis slider, unnecessary driving means is eliminated.

  The tool magazine 30 is assembled to the magazine holding member 69. It is preferable that the tool magazine 30 prevents the chips of the work resulting from the processing of the tool 10 from entering by the partition walls. A plurality of tools 10 are installed in the tool magazine 30 for processing while exchanging.

  A driving force of a Z-axis drive motor (not shown) is transmitted by the drive shaft and the connecting portion, and the main shaft 50 moves along the Z-axis slider 24 in a direction perpendicular to the mounting surface of the machine tool 1. The X-axis drive motor and the Z-axis drive motor function as moving means for moving the main shaft 50 by a member connected to the main shaft 50 by a driving force. As a result, the main shaft can be moved in the three-dimensional two-axis direction.

  The frame body 11 is provided with a plurality of leg portions 5 that protrude downward from the bottom and come into contact with the floor surface. At the place of placement, the machine tool 1 has a stable work operation with respect to a work table (table) 2 assembled to the bottom of the frame 11 by these legs 5 and a work to be fixed to the work table 2. Get.

  A collision target member 57 is provided on the movement path of the tool magazine 30 of the machine tool 1. The machine tool 1 is provided with an up-and-down moving member 62 that moves up and down by contacting the tip holding member 40 and an up-and-down driving means 64 that moves up and down.

<Control configuration>
Next, a control configuration of the machine tool 1 according to the first embodiment will be described with reference to FIG. The tool storage device includes a control unit 201 as a control configuration. The control unit 201 includes a CPU 14, a motor driver 16, and a data storage unit 17.

  The CPU 14 comprehensively controls the machine tool 1 by reading and executing a control program or the like stored in the data storage unit 17. The CPU 14 performs various calculations based on the input data and signals. The motor driver 16 drives the motor 12 that functions as a driving unit based on an instruction from the CPU 14. The main shaft 50 is driven by the drive of the motor 12, and the CPU 14 detects the position of the main shaft by the output from the encoder 13. The position of the workpiece and the size in the height direction can be detected by detecting the amount (actual position) that the spindle 50 has actually moved by driving the motor 12.

  In addition to the control program, the data storage unit 17 stores drive parameters for driving the motor 12, information for associating the output from the encoder 13 and the position of the spindle, and the like. The CPU 14 performs various calculations based on the data stored in the data storage unit 17 and detects the position of the workpiece based on the position read by the encoder 13.

<Work>
In the present invention, since the spindle 50 is moved to the vicinity of the workpiece, it is necessary to know the workpiece size in advance. Therefore, in the present embodiment, several types of standard work sizes are prepared, and the user is allowed to select from them. For example, the following three types of standard workpiece sizes are prepared.
Type 1: Width 100mm, Depth 80mm, Height 15mm
Type 2: Width 100mm, Depth 80mm, Height 50mm
Type 3: Width 100mm, Depth 80mm, Height 100mm
As a method for the user to select these work sizes, they may be input as needed, or may be designated by an NC code in the NC program.

Therefore, it is assumed that a special NC code is prepared, and for example, the function of the NC code is assigned as follows.
M201 ... Machining using type 1 workpiece.
M202 ... Machining using type 2 workpiece.
M203 ... Machining using type 3 workpiece.
At this time, if a code M201 appears in the NC program, this NC program means that machining is performed with a work size of type 1 (width 100 mm, depth 80 mm, height 15 mm). In this way, since the necessary work size is known, the spindle 50 can be moved to the vicinity of the work.

<Height direction detection (constant workpiece height)>
Next, a procedure for detecting the workpiece size (height direction) when the height of the workpiece placed on the work table 2 is constant will be described with reference to FIG. The process described below is realized by the CPU 14 reading and executing a control program stored in the data storage unit 17. Here, processing when a stepping motor is used for the drive unit will be described.

  In S <b> 101, the CPU 14 positions the spindle 50 above the workpiece via the motor driver 16. At this position, the spindle 50 does not contact the workpiece and no step-out occurs. Step-out means, for example, a phenomenon in which the motor cannot follow the pulse signal input to the motor driver 16. When the step-out occurs, a difference between the actual movement position and the commanded predetermined movement position occurs. This difference is hereinafter referred to as position deviation. A range in which the position deviation is allowed is set in advance, and normally it is within the allowable range. However, if this range is exceeded, it is determined that there is an abnormality and the operation is stopped.

  In S102, the CPU 14 reduces the drive torque of the Z axis and further narrows the range that allows the position deviation of the Z axis. The reason for reducing the drive torque is to minimize damage to the mechanical mechanism such as the main shaft 50 or work when the main shaft 50 comes into contact with the work. Similarly, in order to suppress damage such as breakage, the range in which the position deviation is allowed is narrowed, and if any step-out occurs, it is detected as an abnormality and the operation can be stopped. For example, the encoder 13 is used to detect the position. For example, if it is determined that there is an abnormality when the position deviation is shifted by 100 pulses or more, this value is set to 10 pulses, and as soon as the position deviation exceeds 10 pulses, an abnormality is detected and the operation is stopped. Can prevent damage such as breakage.

  In S103, the CPU 14 acquires the height of the workpiece. As this value, a predetermined value may be set in advance, or a value may be input at any time. Alternatively, as described above, a special NC code may be prepared so that the work size can be designated by the NC code on the NC program.

  In S <b> 104, the CPU 14 moves the Z axis and lowers the spindle 50 to the very upper surface of the workpiece. For this purpose, it is necessary to know how far the Z-axis origin should be moved. This position may be a predetermined value according to the height of the workpiece acquired in S103. Or CPU14 may calculate at any time. In the case of calculation, the value obtained by subtracting the height of the workpiece acquired in S103 from the Z-axis position when the spindle 50 is at the position just above the upper surface of the work table 2 on which the workpiece is placed is the calculated value. You may correct | amend this calculation result based on experiment and experience. In addition, by lowering the descending speed of the main shaft 50, when the main shaft 50 comes into contact with the workpiece, damage to the mechanical mechanism such as the main shaft 50 or work is minimized.

  In S105, the CPU 14 determines whether or not a step-out has occurred in the Z axis. That is, it is determined whether or not the positioning of the spindle 50 to the upper surface position of the workpiece performed in S104 has been completed at a predetermined position. The position is detected using the encoder 13. If a step-out occurs, the process proceeds to S106, and the CPU 14 determines that the work is larger than the size set in S103, and proceeds to S108. On the other hand, if no step-out occurs, the process proceeds to S107, and the CPU 14 determines that the work is the size set in S103 or smaller than that, and proceeds to S108. Thereafter, in S108, the CPU 14 restores the driving torque lowered in S102, restores the range allowing the position deviation, and ends the process. Thereafter, the CPU 14 controls the work on the workpiece according to the size of the workpiece determined in S106 or S107.

<Height direction detection (work height indefinite)>
Next, with reference to FIG. 4, the detection procedure for detecting the workpiece size when the workpiece height is not constant and varies in some places will be described. That is, there are a plurality of workpiece height measurement points. The process described below is realized by the CPU 14 reading and executing a control program stored in the data storage unit 17. Here, processing when a stepping motor is used for the drive unit will be described.

  In S201, the CPU 14 stores the number of measurement points in the variable n. Then, the counter variable i is initialized. This variable i is used to refer to the measurement point number. Subsequently, in S202, the CPU 14 increments the variable i. In S203, the CPU 14 acquires the XY position and the workpiece height at the i-th point. These values may be input in advance, or may be input as needed.

  In S204, the CPU 14 moves the spindle 50 to the XY position acquired in S203. The position in the Z direction at this time is assumed to escape upward so as not to contact the workpiece. In S205, the CPU 14 executes the work size detection process described using the flowchart of FIG. However, the workpiece height used in S103 uses the value acquired in S203.

  In S206, if the result of S205 determines that the work size is larger than the predetermined size, the CPU 14 proceeds to S207, and the CPU 14 determines that the work size is larger than the predetermined size, and ends the process. . On the other hand, if the result of S205 determines that the workpiece is a predetermined size or smaller than the predetermined size, the process proceeds to S208. In S208, the CPU 14 determines whether or not the variable i referring to the measurement point number exceeds the number of measurement points (n <i). If n <i, the process proceeds to S209, and the CPU 14 determines that the work is a predetermined size or smaller than the predetermined size, and ends the process. If n <i is not satisfied, it is determined that there is a measurement point that has not been measured yet, and the process returns to S202.

  As described above, when the workpiece height is indefinite and there are a plurality of measurement points, the detection process described with reference to FIG. 3 is executed at each measurement point. If it is determined that the workpiece size is larger than the predetermined size, the measurement is stopped even if there is a point that has not been measured at that time, and it is determined in S207 that the workpiece is larger than the predetermined size. On the other hand, when it is determined in S209 that the workpiece is not larger than the predetermined size, such a result is obtained at all measurement points. Thereafter, the CPU 14 controls the work on the workpiece according to the size of the workpiece determined in S207 or S209.

<Width direction detection (constant workpiece width)>
Next, a detection procedure for detecting the workpiece size (width direction) when the workpiece width is constant will be described with reference to FIG. The process described below is realized by the CPU 14 reading and executing a control program stored in the data storage unit 17. Here, processing when a stepping motor is used for the drive unit will be described.

  In S301, the CPU 14 positions the spindle 50 on the right side of the workpiece. Here, it is on the right side, but may be on the left side. The position in the Z direction is set so that the position of the tip of the spindle 50 is close to the upper surface of the plate on which the workpiece is placed. This position is a state in which the main shaft 50 does not contact the work and no step-out occurs.

  In S <b> 302, the CPU 14 reduces the drive torque of the X axis and further narrows the range that allows the positional deviation of the X axis. Subsequently, in S303, the CPU 14 acquires the width of the work. As this value, a predetermined value may be set in advance, or a value may be input at any time. Alternatively, as described above, a special NC code may be prepared so that the work size can be designated by the NC code on the NC program.

  In S <b> 304, the CPU 14 drives the X axis and moves the spindle 50 to the very right side of the workpiece. The position on the right side of the workpiece is set in advance according to the width of the workpiece, or may be input at any time. In addition, by reducing the moving speed of the main shaft 50, when the main shaft 50 comes into contact with the work, damage to the mechanical mechanism such as the main shaft 50 or work is minimized.

  In S305, the CPU 14 determines whether or not a step-out has occurred on the X axis. That is, it is determined whether or not the operation for moving the spindle 50 to the right surface position of the work performed in S304 has been completed at a predetermined position. For example, the encoder 13 is used to detect the position. If a step-out occurs, the process proceeds to S306, and the CPU 14 determines that the work is larger than the size (predetermined size) set in S303, and proceeds to S308. If no step-out occurs, the process proceeds to S307, and the CPU 14 determines that the work is the size set in S303 or smaller than that, and proceeds to S308. In S308, the CPU 14 restores the driving torque lowered in S302, restores the range allowing the position deviation, and ends the process. Thereafter, the CPU 14 controls the work on the workpiece according to the size of the workpiece determined in S306 or S307. Although the case where there is one measurement point has been described here, when there are a plurality of measurement points in the width direction, the measurement is performed at each point as in FIG.

<Depth direction detection (constant workpiece depth)>
Next, a detection procedure for detecting the workpiece size (depth direction) when the workpiece depth is constant will be described with reference to FIG. The process described below is realized by the CPU 14 reading and executing a control program stored in the data storage unit 17. Here, processing when a stepping motor is used for the drive unit will be described.

  In S401, the CPU 14 positions the spindle 50 before the work. Here, although it is on the near side, the back side of the workpiece may be used. The position in the Z direction is set so that the position of the tip of the spindle 50 is close to the surface on the plate on which the workpiece is placed. This position is a state in which the main shaft 50 does not contact the work and no step-out occurs.

  In S <b> 402, the CPU 14 reduces the drive torque of the Y axis and narrows the range that allows the positional deviation of the Y axis. Subsequently, in S403, the CPU 14 acquires the depth of the work. As this value, a predetermined value may be set in advance, or a value may be input at any time. Alternatively, as described above, a special NC code may be prepared so that the work size can be designated by the NC code on the NC program.

  In S <b> 404, the CPU 14 drives the Y axis to move the workpiece so that the main shaft 50 is positioned at a position just near the front surface of the workpiece. The position near the front of the workpiece hand may be preset according to the depth of the workpiece, or may be input at any time. In addition, by reducing the moving speed of the main shaft 50, when the main shaft 50 comes into contact with the work, damage to the mechanical mechanism such as the main shaft 50 or work is minimized.

  In S405, the CPU 14 determines whether or not a step-out has occurred on the Y axis. That is, it is determined whether or not the positioning to the predetermined position has been completed with respect to the operation performed in S <b> 404 to move the workpiece so that the main shaft 50 is positioned just near the front surface position of the workpiece. For example, the encoder 13 is used to detect the position. If a step-out occurs, the process proceeds to S406, and the CPU 14 determines that the work is larger than the size set in S403. On the other hand, if the step-out does not occur, the process proceeds to S407, and the CPU 14 determines that the work is the size set in S403 or smaller. Thereafter, the process proceeds to S408, where the CPU 14 restores the driving torque lowered in S402, restores the range in which the position deviation is allowed, and ends the process. Although the case where there is one measurement point has been described here, when there are a plurality of measurement points in the depth direction, the measurement is performed at each point as in FIG.

  As described above, in the machine tool 1 according to this embodiment, the size (height direction, width direction, depth direction) of the workpiece placed on the work table 2 is input by a predetermined size, for example, an operator. It is determined whether the size is larger than (selected) or smaller than the size. Specifically, the machine tool 1 drives the spindle 50 in the workpiece direction in consideration of a predetermined size using the spindle 50 to which a tool is attached in order to machine the workpiece, and steps out to the motor 12 that drives the spindle. The size of the workpiece is determined by detecting whether or not the occurrence of the workpiece occurs. When the spindle 50 is driven in the workpiece direction, control is performed so that the workpiece is not damaged by reducing the driving torque. As a result, the machine tool 1 according to the present embodiment can determine the workpiece size while the workpiece is mounted on the work table 2, and can prevent machining failure and tool breakage due to the workpiece size difference at low cost. Thereafter, the CPU 14 controls the work on the workpiece according to the size of the workpiece determined in S406 or S407.

  The present invention is not limited to the above embodiment, and various modifications can be made. For example, in the above embodiment, the size of the workpiece is determined by driving the spindle toward the workpiece placed on the work table 2. However, the workpiece is determined by fixing the spindle and driving the work table 2. The size of the workpiece may be determined by moving the.

<Other embodiments>
The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, etc.) of the system or apparatus reads the program. It is a process to be executed.

Claims (8)

A machine tool,
A spindle that rotates the attached tool;
A table for mounting a workpiece to be machined by a tool attached to the spindle;
Obtaining means for obtaining a size of a workpiece placed on the table;
Driving means for driving the spindle in the vicinity of the work placed on the table according to the size of the work obtained by the obtaining means;
When the driving means stepped out, the work on the workpiece was controlled as if the actual size of the workpiece was larger than the size of the workpiece acquired by the acquiring means, and the driving means did not step out. In this case, the machine tool includes: a control unit that controls a work on the workpiece as a case where an actual size of the workpiece is equal to or smaller than a size of the workpiece acquired by the acquisition unit.   2. The machine tool according to claim 1, wherein the drive unit reduces the drive torque when the spindle is moved in the vicinity of the workpiece. 3. When the driving means moves the spindle to the vicinity of the work, the driving means moves the spindle closer to the work from above, left, right, near, or the back of the work placed on the table. ,
The control means includes
When approaching the spindle from the upper side to the work, determine the size related to the height of the work,
When approaching the spindle from the left or right side to the work, determine the size related to the width of the work,
3. The machine tool according to claim 1, wherein when the main shaft is brought close to the work from the front or the back, a size related to the depth of the work is determined. The control means includes
When determining the size related to the height, width, or depth of the workpiece, at each of a plurality of points, move the spindle to the vicinity of the workpiece using the driving means,
When the driving means steps out at at least one point, the work on the work is controlled as if the actual size of the work is larger than the size of the work obtained by the obtaining means, and at all points 4. If the drive means does not step out, the work on the work is controlled as if the actual size of the work is less than or equal to the size of the work acquired by the acquisition means. The machine tool described in 1.   The acquisition means acquires the size of the workpiece by being input from an operator of the machine tool, or acquires the size of the workpiece by referring to information stored in the machine tool in advance. The machine tool according to any one of claims 1 to 4, wherein: A machine tool,
A spindle that rotates the attached tool;
A table for mounting a workpiece to be machined by a tool attached to the spindle;
Obtaining means for obtaining a size of a workpiece placed on the table;
Driving means for driving the table in accordance with the size of the workpiece acquired by the acquiring means to move the workpiece placed on the table in the vicinity of the spindle;
When the driving means stepped out, the work on the workpiece was controlled as if the actual size of the workpiece was larger than the size of the workpiece acquired by the acquiring means, and the driving means did not step out. In this case, the machine tool includes: a control unit that controls a work on the workpiece as a case where an actual size of the workpiece is equal to or smaller than a size of the workpiece acquired by the acquisition unit. A machine tool control method comprising: a spindle for rotating an attached tool; and a table for attaching a workpiece to be machined by the tool attached to the spindle,
An acquisition step of acquiring a size of a workpiece placed on the table;
A driving step of driving the spindle in the vicinity of the work placed on the table according to the size of the work obtained in the obtaining step;
When step-out occurs in the driving step, the work on the workpiece is controlled as if the actual size of the workpiece is larger than the size of the workpiece acquired in the acquisition step, and step-out occurs in the driving step. And a control step for controlling a work on the workpiece when the actual size of the workpiece is equal to or smaller than the size of the workpiece acquired in the acquisition step. Control method. A machine tool control method comprising: a spindle for rotating an attached tool; and a table for attaching a workpiece to be machined by the tool attached to the spindle,
An acquisition step of acquiring a size of a workpiece placed on the table;
A driving step of driving the table according to the size of the workpiece acquired in the acquiring step and moving the workpiece placed on the table in the vicinity of the spindle;
When step-out occurs in the driving step, the work on the workpiece is controlled as if the actual size of the workpiece is larger than the size of the workpiece acquired in the acquisition step, and step-out occurs in the driving step. And a control step for controlling a work on the workpiece when the actual size of the workpiece is equal to or smaller than the size of the workpiece acquired in the acquisition step. Control method.

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