Monitoring method and monitoring device for monitoring the rotational speed of a rotating shaft in a machine tool, and machine tool

Abstract

Monitoring method for monitoring the rotational speed of a rotary shaft in a machine tool, wherein the machine tool comprises the rotary shaft, to which either a tool or a workpiece is attached and which is driven by a motor (6), and a speed fluctuation unit which causes the rotational speed of the rotary shaft to fluctuate continuously according to an arbitrary pattern, and a fluctuation state of the rotational speed triggered by the speed fluctuation unit is displayed on a display section, characterized in that the monitoring method comprises the following steps: designing a fluctuation diagram (20) which shows a ratio between a fluctuation amplitude (Q) and a fluctuation period (P) for the rotational speed, and displaying the fluctuation diagram (20) on the display section, displaying a current fluctuation position on the fluctuation diagram (20),Calculating an adjustable range (21) for the fluctuation amplitude (Q) and the fluctuation period (P) and displaying the adjustable range (21) on the fluctuation diagram (20), and calculating at least one of an optimal fluctuation period (Po) based on equation (1) and an optimal range (P1) of the fluctuation period (P) based on equation (2), and displaying at least one of the optimal fluctuation period (Po) and the optimal range (P1) of the fluctuation period (P) on the fluctuation diagram (20), where: PO = aTaminT ≤ P1 ≤ amaxT, where PO: optimal fluctuation period [s], P1: optimal range of the fluctuation period [s], T: rotation period of the rotating wave [s], and a, amin, amax: preset coefficients.

Description

[0001] The present invention relates to a monitoring method and a monitoring device for monitoring a fluctuation state of a rotational speed, which is triggered by a speed fluctuation unit on a display section, in a machine tool which includes a rotating shaft to which a tool or a workpiece is attached and which is driven by a motor, and the speed fluctuation unit which causes the rotational speed of the rotating shaft to fluctuate continuously according to any pattern, and also relates to a machine tool which is equipped with the monitoring device.

[0002] When a workpiece with low stiffness is machined using a machine tool, or during machining using a tool with low stiffness, a shock-like vibration known as chatter often occurs during cutting. Chatter produces a periodic pattern, commonly known as chatter marks, on the machined surface and causes degradation of the finished surface finish and machining accuracy. Periodic fluctuations in cutting force cause disturbances that can lead to problems such as tool wear and failure.

[0003] As a method for suppressing chatter vibration, the publication of Japanese patent application no. 49-105277 (JP 49-105277 A) describes a technique that allows the rotational speed of a rotary shaft to fluctuate. The publication of Japanese patent application no. 2000-126991 (JP 2000-126991 A) also describes an invention that enables the simple operation of a control device by displaying a control screen for fluctuating a rotational speed and by allowing the input of a fluctuation range and degree of fluctuation of the rotational speed for each tool when chatter vibration occurs. A previous patent application (Japanese patent application no.2010-235720), filed by the applicant of the present application, provides an invention which displays parameter values ​​that have an effect on regenerative chatter vibration during cutting at fluctuating speeds and allows for easy adjustment of the parameters.

[0004] In the past, however, it was not always possible to minimize chatter vibration as a function of rotational speed, even when a fluctuation period within an operating range, which, as mentioned above, had been shown to have an effect on chatter vibration, was set to a minimum value. Therefore, the operator could not always know the optimal fluctuation period to suppress chatter vibration precisely, and finding the optimal parameters was often time-consuming.

[0005] The present invention was conceived to solve the preceding problems and it is an object of the present invention to provide a monitoring method and a monitoring device for monitoring the rotational speed of a rotary shaft in a machine tool by displaying an optimal fluctuation period for suppressing chatter vibration regardless of the rotational speed of the rotary shaft and to enable simple adjustment of optimal parameters in a short time, and also to provide a machine tool.

[0006] The problem is solved by the features of the independent claims. Further developments of the invention are the subject of the dependent claims.

[0007] To solve the above problem, a first aspect of the present invention is a monitoring method for monitoring a fluctuation state triggered by the speed fluctuation unit on a display section in a machine tool which includes a rotating shaft to which a tool or a workpiece is attached and which is driven by a motor and a speed fluctuation unit which causes a speed of the rotating shaft to fluctuate continuously according to an arbitrary pattern.The monitoring procedure includes the steps of displaying a fluctuation diagram showing the relationship between a fluctuation amplitude and a fluctuation period for the rotational speed on the display section, displaying a current fluctuation position on the fluctuation diagram, displaying an adjustable range for the fluctuation amplitude and the fluctuation period on the fluctuation diagram, and displaying at least one optimal fluctuation period based on equation (1) and one optimal fluctuation period range based on equation (2) on the fluctuation diagram, where . P O = aT (1), and a min T ≤ P1 ≤ a max T (2), where P O : optimal fluctuation period [s], P1: optimal range of the fluctuation period [s], T: Rotation period of the rotational wave [s], and a, amin , a max : preset coefficients.

[0008] According to a second aspect of the present invention, in the configuration according to the first aspect, in the adjustable range display step, an area enclosed by a line representing the power limit of the motor for the fluctuation period and a preset upper limit line for the fluctuation amplitude is displayed as the adjustable range for the fluctuation amplitude and the fluctuation period.

[0009] According to a third aspect of the present invention, the configuration according to the first or second aspect further includes the step of displaying a guide indicator which directs the current fluctuation position displayed in the current fluctuation position indicator step either to the optimal fluctuation period or to the optimal range if the current fluctuation position differs from either the optimal fluctuation period or the optimal fluctuation range displayed in the optimal fluctuation period and optimal range indicator step.

[0010] To solve the above problem, a fourth aspect of the present invention is a monitoring device for monitoring a fluctuation state of the rotational speed triggered by the speed fluctuation unit on a display section in a machine tool, which includes a rotating shaft to which a tool or a workpiece is attached and which is driven by a motor, and a speed fluctuation unit which continuously fluctuates the rotational speed of the rotating shaft according to any desired pattern.The monitoring device includes a fluctuation diagram display unit that displays a fluctuation diagram showing the relationship between a fluctuation amplitude and a fluctuation period for the rotational speed on the display section, a current fluctuation position display unit that displays a current fluctuation position on the fluctuation diagram, an adjustable range display unit that displays an adjustable range for the fluctuation amplitude and the fluctuation period on the fluctuation diagram, and an optimal fluctuation period and optimal range display unit that displays at least one of an optimal fluctuation period based on equation (1) and an optimal range of the fluctuation period based on equation (2) on the fluctuation diagram, wherein . P O = aT (1), and a min T ≤ P1 ≤ a max T (2), where P O: optimal fluctuation period [s], P1: optimal range of the fluctuation period [s], T: Rotation period of the rotational wave [s], and a, a min , a max : preset coefficients.

[0011] According to a fifth aspect of the present invention, the adjustable range display unit in the configuration according to the fourth aspect indicates a range enclosed by a line representing the power limit of the motor for the fluctuation period and a preset upper limit line for the fluctuation amplitude as the adjustable range for the fluctuation amplitude and the fluctuation period.

[0012] According to a sixth aspect of the present invention, the configuration according to the fourth or fifth aspect further includes a guide display unit that displays a guide indicator which directs the current fluctuation position displayed by the current fluctuation position display unit either to the optimal fluctuation period or to the optimal fluctuation range if the current fluctuation position differs from either the optimal fluctuation period or the optimal range displayed by the optimal fluctuation period and optimal range display unit.

[0013] To solve the above problem, a seventh aspect of the present invention is a machine tool comprising a rotary shaft to which a tool or a workpiece is attached and which is driven by a motor, a speed fluctuation unit which causes the speed of the rotary shaft to fluctuate continuously according to any pattern, and the monitoring device according to one of the fourth to sixth aspects.

[0014] According to the first, fourth, and seventh aspects of the present invention, the operator can quickly and effectively find a fluctuation cutting parameter with a high chatter vibration suppression effect during cutting at any rotational speed, based on the display on the display section. Furthermore, the fluctuation amplitude and the fluctuation period of the rotational shaft speed can be modified using optimal parameters.

[0015] According to the second and fifth aspects of the present invention, in addition to the effects described above, a suitable adjustable range can be selected which takes into account the maximum power of the motor.

[0016] According to the third and sixth aspects of the present invention, in addition to the effects described above, the operator can easily recognize the instruction to change parameters with a high chatter vibration suppression effect.

[0017] Fig. Figure 1 is a schematic configuration diagram of an NC lathe.

[0018] Fig. Figure 2 is an explanatory diagram showing an example of a fluctuation in the speed of a main spindle.

[0019] Fig. Figure 3 is a graph of experimental results.

[0020] Fig. Figure 4 is an explanatory illustration showing an example of a display on a monitor.

[0021] Fig. Figure 5 is an explanatory illustration showing an example of a different display of a fluctuation diagram.

[0022] Fig. Figure 6 is an explanatory illustration showing an example of yet another display of the fluctuation diagram.

[0023] An embodiment of the present invention is described below based on the drawings.

[0024] Fig. Figure 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 box is stored 2 a main spindle 3 rotatable. The main spindle 3 serves as a rotating shaft that moves a workpiece W through a chuck 4 and paws 5 holds on. An engine 6 , which is the main spindle 3 rotary drive and an encoder 7 , which is attached to the spindle housing 2is attached and has a rotational speed of the main spindle. 3 They are recorded, are in the spindle housing 2 built-in.

[0025] Reference sign 8 designates a main spindle control section that is connected to the motor 6 and the encoder 7 is connected. Reference sign 9 refers to a machine tool control section that transmits a speed command to the main spindle control section. 8 specifies. The main spindle control section 8 monitors the encoder 7 measured speed of the main spindle 3 constantly and also provides the information for the engine 6 delivered power such that the main spindle 3 with the machine tool control section 9 rotates at the specified speed.

[0026] The machine tool control section 9 is equipped with an input unit 10to specify a change in rotational speed or the like, a memory section 11 , which stores editing programs and the like, a parameter calculation section 12 , which calculates the optimal parameter for suppressing a chatter oscillation, and a parameter display control section 13 connected, which is connected by the parameter calculation section 12 calculated parameters and a fluctuation diagram described later on a monitor 14 , which is a display section. The machine tool control section 9 has a known configuration for performing a cutting process in which a tool mounted in a tool holder (not shown) cuts the workpiece W when the main spindle 3 rotates, and moves the tool holder in the radial or longitudinal direction.

[0027] Based on the rotational speed of the main spindle 3and a fluctuation amplitude and a fluctuation period of the main spindle 3 , each using the input unit 10 The machine tool control section can be entered 9 the speed of the main spindle 3 , as in Fig. As shown in Figure 2, the machine tool control section can fluctuate according to the specified amplitude and period of fluctuation. In other words, the machine tool control section functions as follows: 9 as a speed fluctuation unit.

[0028] An optimal fluctuation period, which suppresses chatter during cutting by varying the main spindle speed, can be found through a cutting test. For example, the optimal fluctuation period that minimizes vibration can be found by cutting a workpiece with a boring bar on the main spindle. 3The process is carried out on the fixed workpiece W, while the vibration is measured with a vibration measuring device placed on the boring bar during a cutting operation and the fluctuation period is determined by the input unit. 10 is caused to waver. Fig. Figure 3 is a diagram showing the relationship between the oscillation period found through an experiment and the magnitude of the chatter vibration. If T is a rotation period of the main spindle... 3 is, an optimal fluctuation period P can be O as shown below in equation (1). Note that a may, for example, be a coefficient empirically determined by an instrument in the cutting test described above. P O = aT (1), where P O : optimal fluctuation period [s], and T: Main spindle rotation period [s].

[0029] Next, a display will appear on the monitor. 14 described, which are described by the parameter display control section 13 , which is an essential part of the present invention. The parameter display control section 13 It functions as a fluctuation chart display unit, a current fluctuation position display unit, an adjustable range display unit, an optimal fluctuation period and range display unit, and a guide display unit. The parameter display control section 13 together with the monitor 14 a monitor device of the present invention.

[0030] First, the NC lathe is used. 1A time-domain vibration during machining is detected by a vibration sensor (not shown) mounted on the tool, and it is monitored for chatter vibration. A waveform from the vibration sensor is displayed on the monitor. 14 displayed in real time, so that the occurrence of a chatter oscillation can be detected.

[0031] If a chatter vibration is confirmed, in addition to a main program and a basic display, the current position of the main spindle is shown. 3 , based on a input unit 10 The instruction given creates a fluctuation diagram. 20 on the monitor 14 displayed (fluctuation chart display step). As in Fig. As shown in Figure 4, the vertical axis of the fluctuation diagram represents 20 A fluctuation amplitude Q and a fluctuation period P are defined on the horizontal axis. A reference rotational speed S is used here. O, the fluctuation amplitude Q, the fluctuation period P, the coefficient a for finding the optimal fluctuation period, a minimum coefficient a min and a maximum coefficient a max as the parameters are displayed. Additionally, a line L1 indicating the motor's power limit is shown. 6 and an upper limit line L2 of the fluctuation amplitude Q on the fluctuation diagram 20 Displayed (adjustable range display step). A lower range enclosed by line L1 of the power limit and by the upper limit line L2 of the fluctuation amplitude Q corresponds to an adjustable range. 21 the parameter.

[0032] Accordingly, the operator can enter predetermined parameters when a chatter vibration occurs in order to control the speed of the main spindle. 3The system allows the value to fluctuate based on the fluctuation amplitude Q and the fluctuation period P, according to the parameter values. In such a case, a setpoint A, indicating the current fluctuation position, is represented as a black circle in the fluctuation diagram. 20 displayed (Current fluctuation position display step).

[0033] It should be noted that an upper limit for input power is specified, as excessive current can damage the motor. 6 would overheat and damage. Therefore, it is not possible to allow the speed to fluctuate with the set values, even if the speed fluctuation amplitude Q is set to a large value and the fluctuation period P is set to a small value. Then the parameter display control section calculates 13for example, using equation (3) below, a limit line for the fluctuation amplitude Q and the fluctuation period P, where the rotational speed is based on the maximum input power of the motor. 6 , i.e., the line L1 of the power limit for the fluctuation period P, can be oscillated, and it displays this. Meanwhile, the upper limit of the fluctuation amplitude Q can be set on an input screen (not shown) by pressing a button at the bottom of the monitor. 14 displayed upper limit adjustment knob 22 appears, can be entered. where Q: Fluctuation amplitude [%], S: Main spindle speed [min –1 ], E: maximum motor input power [W], P: Fluctuation period [s] J: Main spindle inertia [kg·m²] 2 ], and Ec: Sum of cutting power and power loss [W].

[0034] In the fluctuation diagram 20from Fig. 4 will be the optimal fluctuation period P O , which is calculated from the preset coefficient a and equation (1), and an optimal range P1 of the fluctuation period, which is calculated in equation (2) below using the coefficients a min , a max , is calculated, and the main spindle rotation period T is displayed together (optimal fluctuation period and optimal range display step) to suppress regenerative chatter vibration. a min T < P1 < a max T (2)

[0035] Here, the optimal parameters for suppressing a chatter oscillation are indicated by a white circle representing a recommended value B. At the recommended value B, the fluctuation period P corresponds to the optimal fluctuation period P found using equation (1). O , and the fluctuation amplitude Q corresponds to the maximum value of the adjustable parameter range. 21By pressing a button at the bottom of the monitor 14 displayed Recommended Value setting button 23 The parameters can be changed immediately to the recommended value B.

[0036] It should be noted that if a chatter vibration cannot be suppressed, even after adjusting the Recommended Value setting knob... 23 The set parameters are used to determine the fluctuation period P within the range of a min T < P1 < a max T can be adjusted while the waveform is observed by the vibration sensor to set the fluctuation period P with the lowest chatter vibration. Thus, a chatter vibration suppression effect can be maximized after a short adjustment. At the bottom of the monitor 14 will be adjustment knobs? 24 , 24 for the fluctuation amplitude Q and adjustment knobs 25 , 25 Displayed for the fluctuation period P.

[0037] However, if an excessively large fluctuation amplitude Q is used, the cutting speeds at low and high speeds will differ from the tool's recommended cutting speeds. Therefore, the fluctuation amplitude Q in the range where chatter vibration can be suppressed is preferably the smallest possible value. Accordingly, as in Fig. 4 shown, based on a measurement by the input unit 10 entered instruction, a guide arrow 26 A guide indicator is displayed (guide indicator step) when the current setting value A is not within the optimal range P1. The guide arrow 26 It starts at the current setting value A and consists of a horizontal line that only shows the fluctuation period P up to the optimal fluctuation period P Oleads to a vertical line that represents the fluctuation amplitude Q from there to the upper limit, which is set as the recommended value B. Using the guide arrow 26 The operator can be encouraged to first adjust from the currently set value A to the optimal fluctuation period P. O to switch, and if this does not achieve a chatter vibration suppression effect, the operator may next be encouraged to switch to the upper limit of the fluctuation amplitude Q (here the recommended value B).

[0038] Also in the Fig. 5 and Fig. 6 fluctuation diagrams shown 20 The recommended value B and the guide arrow indicating the parameter change instruction are shown when the line L1 of the power limit and the optimal range P1 of the fluctuation period P are within the adjustable parameter range. 21The chatter vibration suppression effect increases when, assuming a constant power input from the motor, the power consumption is maintained. 6 , the fluctuation amplitude Q increases. Thus, in Fig. 5 a guide arrow 27 displayed, which consists of a horizontal line that only shows the fluctuation period P to the optimal fluctuation period P calculated from the coefficient a and equation (1). O leads to a vertical line which, in order to further increase the chatter vibration suppression effect, directs the fluctuation amplitude Q from there to the line L1 of the power limit, where the motor 6 at its maximum power output, and consists of a diagonal line that leads the fluctuation amplitude Q to the recommended value B on line L1 of the power limit. Similarly, in Fig. 6 a guide arrow 28, which consists of a horizontal line that leads only the fluctuation period P to the optimal range P1 and to the line L1 of the power limit, and a diagonal line that leads the fluctuation amplitude Q to the recommended value B on the line L1 of the power limit.

[0039] Thus, according to the monitoring procedure and the monitoring device of the NC lathe 1 of the embodiment described above, the fluctuation diagram 20 , which is the ratio between the fluctuation amplitude Q and the fluctuation period P for the rotational speed of the main spindle 3 shows, on the monitor 14 Indicates when chatter occurs, allowing the rotational speed to be continuously oscillated according to any desired pattern. The current setting value A and the adjustable range are displayed. 21 The fluctuation amplitude Q and the fluctuation period P are also shown on the fluctuation diagram. 20The optimal fluctuation period P based on equation (1) is also displayed. O and the optimal range P1 of the fluctuation period P based on equation (2) on the fluctuation diagram 20 displayed. Accordingly, the operator can adjust a fluctuation cutting parameter with a high chatter vibration suppression effect during cutting at any speed based on the display on the monitor. 14 Find it quickly and effectively. Furthermore, the fluctuation amplitude Q and the fluctuation period P for the main spindle speed can be determined. 3 modified using the optimal parameters.

[0040] It should be noted in particular here that the power limit of the engine is defined by line L1. 6 for the fluctuation period P and the preset upper limit line L2 for the fluctuation amplitude Q, the included area is the adjustable range. 21The fluctuation amplitude Q and the fluctuation period P are displayed. Therefore, a suitable adjustable range can be selected to determine the maximum power output of the motor. 6 to be considered and selected.

[0041] Additionally, the guide arrows 26 until 28 The indicator that leads the current setting value A to the optimal fluctuation period Po is displayed when the current setting value A is outside the optimal range P1. Therefore, the operator can easily recognize the instruction to change to parameters with a high chatter vibration suppression effect.

[0042] It should be noted that in the embodiment described above, after the fluctuation diagram is displayed on the monitor and fluctuation of the main spindle begins, the performance limit line, the upper limit of the fluctuation amplitude, the optimal fluctuation period, and the optimal range are displayed automatically. However, these can be displayed at any individual time using the input unit. Alternatively, a guide display can also be displayed automatically. The fluctuation diagram is obviously not limited to the embodiment and content as described above. Modifications, such as reversing the axes or using a three-dimensional display, are also conceivable.

[0043] Additionally, although the optimal fluctuation period and the optimal range are displayed simultaneously on the fluctuation diagram, each can be displayed individually.

[0044] Indications of the currently set value and the recommended value are not limited to circles. Markers of a different shape can be chosen, or the shapes of the markers for the currently set value and the recommended value can differ from each other. The indication of the adjustable range for the parameters can also be differentiated by something other than lines. For example, differences in color or shading can be used instead. Additionally, the guide indicator is not limited to an arrow and can be modified appropriately, provided that the guide indicator suggests a change to new fluctuation positions. For example, the marker for the current fluctuation position can flash while a notification to move to a new fluctuation position is repeated.The guidance is not limited to the recommended value and can also simply be a guide to either the optimal fluctuation period or the optimal range. Furthermore, it should be noted that the guidance display is not mandatory.

[0045] In the embodiment described above, the main spindle is initially rotated at a set, constant speed. If a chatter vibration is detected, the input unit is used to input the amplitude and period of the fluctuation in the rotational speed, thus causing the speed to fluctuate. However, the rotational speed may fluctuate from the outset.

[0046] The present invention is not limited to an NC lathe and includes any machine tool that allows the rotational speed to fluctuate when cutting a workpiece, e.g. a machining center that performs machining of workpieces by rotating a rotary shaft to which a tool is attached. QUOTES INCLUDED IN THE DESCRIPTION

[0047] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0048] JP 49-105277 A

[0003] JP 2000-126991 A

[0003] JP 2010-235720

[0003]

Claims

[1] Monitoring method for monitoring the rotational speed of a rotary shaft in a machine tool, wherein the machine tool is the rotary shaft to which either a tool or a workpiece is attached and which is driven by a motor ( 6 ) is driven, and includes a speed fluctuation unit that continuously fluctuates the speed of the rotating shaft according to any pattern, and a fluctuation state of the speed triggered by the speed fluctuation unit is displayed on a display section, characterized by that the monitoring procedure comprises the following steps: Displaying a fluctuation chart ( 20 ), which shows a ratio between a fluctuation amplitude and a fluctuation period for the rotational speed on the display section, Displaying a current fluctuation position on the fluctuation chart ( 20 ), Displaying an adjustable range (21 ) for the fluctuation amplitude and the fluctuation period on the fluctuation diagram ( 20 ), and Displaying at least one optimal fluctuation period based on equation (1) and one optimal fluctuation period range based on equation (2) on the fluctuation diagram ( 20 ), where: P O = aT (1), and a min T ≤ P1 ≤ a max T (2), where P O : optimal fluctuation period [s], P1: optimal range of the fluctuation period [s], T: Rotation period of the rotational wave [s], and a, a min , a max : preset coefficients. [2] Monitoring method for monitoring the rotational speed of a rotary shaft in a machine tool according to claim 1, wherein in the adjustable range display step a range defined by a line of the power limit of the motor ( 6 ) for the fluctuation period and a preset upper limit for the fluctuation amplitude is included, as the adjustable range ( 21 ) is displayed for the fluctuation amplitude and the fluctuation period. [3] Monitoring method for monitoring the rotational speed of a rotary shaft in a machine tool according to claim 1 or 2, further comprising a step of: Displaying a guide indicator that leads the current fluctuation position shown in the Current-Fluctuation-Position indicator step to either the optimal fluctuation period or the optimal range, if the current fluctuation position differs from either the optimal fluctuation period or the optimal range shown in the Optimal-Fluctuation-Period-and-Optimal-Range indicator step. [4] Monitoring device for monitoring the rotational speed of a rotary shaft in a machine tool, wherein the machine tool provides the rotary shaft to which either a tool or a workpiece is attached and which is driven by a motor ( 6) is driven, and includes a speed fluctuation unit that continuously fluctuates the speed of the rotating shaft according to any pattern, and a fluctuation state of the speed triggered by the speed fluctuation unit is monitored on a display section, characterized by the fact that the display device has: a fluctuation diagram ( 20 )-display unit that shows a fluctuation diagram ( 20 ) indicates the ratio between a fluctuation amplitude and a fluctuation period for the rotational speed on the display section, a current fluctuation position display unit that shows a current fluctuation position on the fluctuation graph ( 20 ) displays, an adjustable-range display unit that has an adjustable range ( 21 ) for the fluctuation amplitude and the fluctuation period on the fluctuation diagram ( 20 ) displays, and an optimal-fluctuation-period-and-optimal-range display unit that shows at least one of an optimal fluctuation period based on equation (1) and an optimal range of the fluctuation period based on equation (2) on the fluctuation diagram ( 20 ) displays P O = aT (1), and a min T ≤ P1 ≤ a max T (2), where P O : optimal fluctuation period [s], P1: optimal range of the fluctuation period [s], T: Rotation period of the rotational wave [s], and a, a min , a max : preset coefficients. [5] Monitoring device for monitoring the rotational speed of a rotary shaft in a machine tool according to claim 4, wherein the adjustable range display unit includes a line representing the power limit of the motor ( 6) for the fluctuation period and a preset upper limit for the fluctuation amplitude, the included area being the adjustable range ( 21 ) displays the fluctuation amplitude and the fluctuation period. [6] Monitoring device for monitoring the rotational speed of a rotary shaft in a machine tool according to claim 4 or 5, further comprising: a guide display unit that displays a guide indicator which leads the current fluctuation position displayed by the current fluctuation position display unit to either the optimal fluctuation period or the optimal range, if a current fluctuation position differs from either the optimal fluctuation period or the optimal range displayed by the optimal fluctuation period and optimal range display unit. [7] Machine tool comprising: a rotating shaft to which either a tool or a workpiece is attached, and which is driven by a motor ( 6 ) is powered, a speed fluctuation unit that continuously fluctuates the speed of the rotating shaft according to any desired pattern, and the monitoring device according to one of claims 4 to 6.

Images