JP5674449B2 - Machine Tools - Google Patents

Description

  The present invention relates to a machine tool that includes a rotary shaft that is mounted with a tool or a workpiece and is driven by a motor, and that can perform cutting by varying the rotational speed of the rotary shaft.

When cutting is performed by a machine tool equipped with a rotating shaft that is driven by a motor while the tool or workpiece is mounted, so-called “chatter vibration” may occur if the rigidity of the tool or workpiece is low. When chatter vibration is generated, problems such as tool breakage and deterioration of the surface accuracy of the workpiece occur. This chatter vibration causes a phase lag between the undulation before one rotation generated on the machined surface and the vibration due to the current cutting, so that the cut thickness of the workpiece fluctuates and the vibration expands.
As techniques for suppressing this chatter vibration, the countermeasures of Patent Document 1 and Patent Document 2 have been proposed. The techniques described in Patent Document 1 and Patent Document 2 vary chatter vibration by changing the rotation speed of the rotating shaft with a predetermined fluctuation amplitude and fluctuation period, and by irregularly inputting force due to fluctuations in the cutting thickness. It is something to try.

JP-A-49-105277 Japanese Utility Model Publication No. 61-3522

  However, the methods described in Patent Document 1 and Patent Document 2 use two parameters of a fluctuation amplitude and a fluctuation period in order to fluctuate the rotation speed (hereinafter referred to as “fluctuation value” when both parameters are not distinguished). Therefore, it is unclear which parameter should be changed, and it is difficult for an inexperienced operator to judge.

  Accordingly, the present invention has been made in view of the above problems, and provides a machine tool that can easily set a variation value for varying the rotational speed of the rotating shaft regardless of the depth of experience of the operator. It is intended.

In order to achieve the above-mentioned object, the invention according to claim 1 is a variable value setting for setting a rotating shaft on which a tool or a work is mounted to drive a motor, and a fluctuation amplitude and a fluctuation cycle of the rotational speed of the rotating shaft. A rotation axis control means for controlling the rotation speed of the rotation axis based on the fluctuation amplitude and fluctuation period set by the fluctuation value setting means, the fluctuation value setting means, The ratio between the fluctuation amplitude and the fluctuation period is set based on the rated output of the motor, the cutting output, the usage ratio with respect to the rated output of the motor, the average value of the rotation speed, and the inertia of the rotation shaft. The variation amplitude and the variation period are set simultaneously based on the ratio.
The invention according to claim 2, in the configuration of claim 1, wherein the variation value setting means, which is characterized in that the setting the ratio of the fluctuation amplitude and variation period based on the following equation (1) It is.

In order to achieve the above object, a third aspect of the present invention is a variable value setting for setting a rotation shaft that is driven by a motor by mounting a tool or a workpiece, and a fluctuation amplitude and a fluctuation cycle of the rotation speed of the rotation shaft. A rotation axis control means for controlling the rotation speed of the rotation axis based on the fluctuation amplitude and fluctuation period set by the fluctuation value setting means,
The fluctuation value setting means sets a ratio between the fluctuation amplitude and the fluctuation period, sets the fluctuation amplitude and the fluctuation period at the same time based on the ratio, and shows a relationship between the fluctuation amplitude and the fluctuation period. A button provided on the display means for displaying the current position of the fluctuation amplitude and the fluctuation period and a straight line relating to the ratio of the fluctuation amplitude and the fluctuation period on the graph. The variation amplitude and the variation period can be simultaneously changed by maintaining the ratio by pressing the button .

According to the first aspect of the present invention, the two parameters of the fluctuation amplitude and the fluctuation period can be set simultaneously by one operation. Therefore, regardless of the depth of experience, the operator can easily set a fluctuation value for changing the rotation speed of the rotary shaft.
Further , the variation value can be set in a situation where the current flowing through the motor is not excessive, and the occurrence of thermal displacement due to the heat generation of the motor is suppressed.
According to the third aspect of the present invention, the current fluctuation value and the changed fluctuation value can be easily recognized by the graph, and the fluctuation value can be set more easily.

It is a schematic block diagram of NC lathe. It is explanatory drawing which shows the fluctuation state of a rotational speed and a spindle torque. It is explanatory drawing which shows the display of a monitor.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of an NC lathe 1 which is an example of a machine tool. In the NC lathe 1, a spindle 3 as a rotating shaft for grasping the workpiece W via a chuck 4 and a claw 5 is rotatably supported on the spindle stock 2, and the spindle 3 is placed inside the spindle stock 2. A motor 6 that is driven to rotate and an encoder 7 that is fixed to the headstock 2 and detects the rotational speed of the main shaft 3 are incorporated.
Reference numeral 10 denotes a control unit of the NC lathe 1. The control unit 10 is provided with a spindle control unit 11 connected to the motor 6 and the encoder 7, and an NC device 12 for instructing the spindle control unit 11 on the rotation speed. Thus, the spindle control unit 11 adjusts the input power supplied to the motor 6 so as to rotate the spindle 3 at the rotation speed commanded from the NC device 12 while constantly monitoring the rotation speed of the spindle 3 detected by the encoder 7. doing.

In the control unit 10, the NC device 12 is connected to a storage unit 13 for storing a machining program and the like, and a fluctuation value setting unit 14 as a fluctuation value setting unit having a monitor 15 as a display unit. The NC device 12 performs a cutting process by feeding and moving a tool (not shown) in the rotation axis direction and the radial direction of the workpiece W while rotating the spindle 3 according to the machining program stored in the storage unit 13.
Furthermore, the NC device 12 and the spindle control unit 11 as the rotation axis control unit are input here by inputting the rotation speed of the spindle 3 and its fluctuation amplitude and fluctuation period from the monitor 15 provided with the input unit to the fluctuation value setting unit 14. As shown in FIG. 2, the rotational speed of the main shaft 3 can be changed with a specified fluctuation amplitude and fluctuation cycle.

Then, when the fluctuation amplitude and the fluctuation cycle are input, the fluctuation value setting unit 14 takes the fluctuation amplitude-fluctuation with the fluctuation amplitude on the vertical axis and the fluctuation period on the horizontal axis, as shown in FIG. The period graph 16 is displayed, and the current fluctuation amplitude-fluctuation period setting value (current fluctuation value) is displayed with a black circle marker M.
Further, the monitor 15 displays a left down arrow button 17 and a right up arrow button 18 so that when the operator presses any button, the position of the marker M moves in the arrow direction of the button. It has become. 19 and 19 are windows for displaying numerical values of the fluctuation amplitude and fluctuation period at the position of the marker M, respectively.

  However, the fluctuation value setting unit 14 sets a ratio between the fluctuation amplitude and the fluctuation period of the rotation speed, and sets the fluctuation amplitude and the fluctuation period at the same time based on the ratio. Specifically, the ratio between the fluctuation amplitude and the fluctuation period is obtained from the rated output of the motor 6, the cutting output, the usage ratio with respect to the rated output of the motor 6, the average value of the rotation speed, and the inertia of the spindle 3. For example, a value satisfying the following expression (1) is conceivable. In this case, the output of the motor 6 is regulated and changed at a ratio with respect to the rated output. When the rotational speed is changed, the current flowing through the motor 6 increases, the heat generation of the motor 6 increases, and thermal displacement occurs. It is because there is a possibility of doing.

  Of these, the cutting output Pc can be calculated from the changing spindle torque once the change starts. The relationship between the time and the rotation speed when changing the rotation speed and the relationship between the time and the spindle torque are clear from FIG. 2, and it is understood that a large torque is required during acceleration and deceleration of the rotation speed of the spindle 3. . The main shaft torque during acceleration and deceleration has the same vertical width around the cutting torque. From this, the cutting torque can be obtained as the median value (average value) of the main shaft torque during acceleration and the main shaft torque during deceleration. Since there is a relationship of the following formula (2) between the torque and the output, the cutting torque can be converted into the cutting output. The obtained value includes the friction loss due to the rotation of the main shaft 3, but the friction loss is a small value and is omitted here.

When the cutting power thus obtained is 2 kW, for example, the rated output is 8 kW, the inertia is 0.5 kW · m ² , the rotational speed is 1500 min ⁻¹ , and the output during fluctuation is 80% of the rated output, the fluctuation amplitude is 20%. Then, the fluctuation period satisfying the equation (1) is 1.1 s.
In the graph 16, a straight line L1 representing the ratio of the formula (1) is displayed. For example, when the upper right arrow button 18 is pressed, the cycle is long and the amplitude is specified in advance. The marker M moves along the straight line L1 by the amount of fluctuation amplitude, and the fluctuation value is displayed in the window 19. For example, when the fluctuation amplitude designated in advance is 5% and the upper right arrow button 18 is pressed once, the fluctuation amplitude is 25%, and the fluctuation period is 1.4 s from the equation (1). When a determination button (not shown) is pressed here, a fluctuation value is output to the NC device 12, and the rotation speed of the spindle 3 fluctuates with the fluctuation value displayed in the window 19.

  In general, when the output of the motor 6 is the same, the larger the fluctuation amplitude, the greater the chatter vibration suppression effect. However, when the fluctuation amplitude increases, the difference in speed between the high speed and the low speed is large, and a striped pattern appears on the processed surface. There are conflicting relationships. Therefore, it is desirable that the operator adjusts by pressing the upper right arrow button 18 when chatter vibration is occurring and pressing the left lower arrow button 17 when chatter vibration is not occurring.

  In addition, the fluctuation value setting unit 14 recalculates the ratio between the fluctuation amplitude and the fluctuation period in accordance with the fluctuation of each parameter of the equation (1), and changes the straight line L1. For example, when the machining allowance of the workpiece W increases during machining, the cutting output increases, so that the straight line L1 is changed to the straight line L2 with a small inclination. When the upper right arrow button 18 is pressed here, the marker M has a long cycle along the straight line L2, starting from a point M1 that intersects the straight line B with the current fluctuation amplitude (a point satisfying the recalculated formula (1)). In addition, it moves by the fluctuation amplitude specified in advance in the direction of increasing the amplitude.

As described above, according to the NC lathe 1 of the above embodiment, the fluctuation value setting unit 14 sets the ratio between the fluctuation amplitude and the fluctuation period, and simultaneously sets the fluctuation amplitude and the fluctuation period based on the ratio. Two parameters of the fluctuation amplitude and the fluctuation period can be set simultaneously by one operation. Therefore, regardless of the depth of experience, the operator can easily set a variation value for varying the rotation speed of the spindle 3.
In particular, here, the fluctuation value setting unit 14 uses the above-described equation (1) using the rated output of the motor 6, the cutting output, the usage ratio with respect to the rated output of the motor 6, the average value of the rotational speed, and the inertia of the spindle 3. Since the ratio between the fluctuation amplitude and the fluctuation cycle is set based on 1), the fluctuation value can be set in a situation where the current flowing through the motor 6 is not excessive, and the occurrence of thermal displacement due to the heat generation of the motor 6 is suppressed. The

  Further, the fluctuation value setting unit 14 includes a monitor 15 that displays a graph 16 indicating the relationship between the fluctuation amplitude and the fluctuation period. The graph 16 includes a position (marker M) of the current fluctuation amplitude and the fluctuation period, and a fluctuation. Since the straight lines L1 and L2 relating to the ratio between the amplitude and the fluctuation cycle are respectively displayed, the current fluctuation value and the changed fluctuation value can be easily recognized, and the fluctuation value can be set more easily. Can do.

  The ratio between the fluctuation amplitude and the fluctuation period is not limited to the case according to the above formula (1). For example, when the cutting output can be considered to be substantially constant, when the output is changed with the motor output equivalent to the current one, the following expression (3) may be simultaneously changed.

The constant k is obtained by substituting the current fluctuation amplitude and fluctuation period. When the left down arrow button 17 or the right up arrow button 18 is pressed once, a constant k is obtained from the current value, and is changed to a variation value satisfying Expression (3). For example, when the upper right arrow button 18 is pressed, the movement value is changed to a fluctuation value that satisfies the expression (3) while moving by the fluctuation amplitude specified in advance in the direction in which the fluctuation period is long and the fluctuation amplitude is large. Also in this case, the straight line of the formula (3) is shown on the graph.
In this way, when the cutting power can be regarded as almost constant, the relationship between the fluctuation amplitude and the fluctuation cycle becomes a simple proportional formula, so even if the cutting power fluctuates for some reason, stable fluctuations can be achieved by pressing the arrow buttons. A value can be obtained.

  Furthermore, in the above embodiment, when the graph is displayed on the monitor, the marker indicating the current fluctuation value and the straight line relating to the ratio are automatically calculated and displayed. These may be displayed at arbitrary timings. Of course, the form of the graph is not limited to the above contents, and it is possible to change the axis to be reversed or to be displayed three-dimensionally. However, it is not essential to display a straight line related to a graph, a marker, or a ratio, and the current fluctuation value and the changed fluctuation value may be displayed only by numerical values.

On the other hand, after selecting the fluctuation value on the monitor, the rotation axis control means changes the rotation speed by inputting the enter button again. However, the rotation speed is linked with the selection of the fluctuation value. It is also possible to automatically execute the change.
In addition, the present invention is not limited to an NC lathe, and includes a machining center including a main shaft on which a tool is mounted, for example, as long as it is a machine tool that performs cutting by changing the rotational speed of a rotary shaft.

  1 .... NC lathe 2 .... spindle stand 3 .... spindle 4 .... chuck 5 .... claw 6 ... motor 7 ... encoder 10 .... control unit 11 .... spindle control unit, 12..NC device, 13..Storage unit, 14..Variable value setting unit, 15..Monitor, 16..Graph, 17..Upper left arrow button, 18..Upper right arrow button, 19..Window , W ... work, M ... marker, L1, L2 ... straight line.

Claims (3)

A rotary shaft that is driven by a motor with a tool or workpiece mounted thereon, a fluctuation value setting means that sets a fluctuation amplitude and a fluctuation cycle of the rotation speed of the rotation axis, and a fluctuation amplitude and a fluctuation period that are set by the fluctuation value setting means A rotation axis control means for controlling the rotation speed of the rotation axis based on
The fluctuation value setting means includes the fluctuation amplitude and fluctuation based on the rated output of the motor, the cutting output, the usage ratio with respect to the rated output of the motor, the average value of the rotation speed, and the inertia of the rotation shaft. A machine tool characterized by setting a ratio with a period and simultaneously setting the fluctuation amplitude and the fluctuation period based on the ratio. 2. The machine tool according to claim 1 , wherein the variation value setting means sets a ratio between the variation amplitude and a variation period based on the following equation (1).

A rotary shaft that is driven by a motor with a tool or workpiece mounted thereon, a fluctuation value setting means that sets a fluctuation amplitude and a fluctuation cycle of the rotation speed of the rotation axis, and a fluctuation amplitude and a fluctuation period that are set by the fluctuation value setting means A rotation axis control means for controlling the rotation speed of the rotation axis based on
The fluctuation value setting means sets a ratio between the fluctuation amplitude and the fluctuation period, sets the fluctuation amplitude and the fluctuation period at the same time based on the ratio, and shows a relationship between the fluctuation amplitude and the fluctuation period. A button provided on the display means for displaying the current position of the fluctuation amplitude and the fluctuation period and a straight line relating to the ratio of the fluctuation amplitude and the fluctuation period on the graph. A machine tool characterized in that the fluctuation amplitude and the fluctuation period can be changed simultaneously while keeping the ratio by pushing operation .

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