CN113874798A

CN113874798A - Numerical control device

Info

Publication number: CN113874798A
Application number: CN201980096558.5A
Authority: CN
Inventors: 高币一树; 铃木教和
Original assignee: National University Corp Donghai National University; Mitsubishi Electric Corp
Current assignee: National University Corp Donghai National University; Mitsubishi Electric Corp
Priority date: 2019-05-23
Filing date: 2019-05-23
Publication date: 2021-12-31
Anticipated expiration: 2039-05-23
Also published as: JP7101883B2; JPWO2020235106A1; DE112019007355T5; WO2020235106A1; CN113874798B

Abstract

A numerical control device (1) according to the present invention controls the operation of a machine tool (2) that machines a workpiece by a tool, and comprises: a uniform motion generating unit (14) that generates a uniform motion command for independently and continuously changing the spindle rotation speed and the feed speed; a data acquisition unit (16) that synchronizes a control signal for controlling the machine tool, which is generated based on the identification operation command, with an operation state signal indicating the operation state of the corresponding machine tool (2), and outputs the control signal and the operation state signal as identification data; a vibration determination unit (12) that determines, based on the identification data, which of stable machining, chatter vibration, and forced vibration is the state of vibration of the machine tool (2); and a specifying unit (13) that selects, as a selection parameter, a machining characteristic parameter that can be specified, from among machining characteristic parameters that indicate characteristics of a machining phenomenon between the tool and the workpiece, based on the determination result of the vibration determination unit (12), and specifies the selection parameter using the specification data.

Description

Numerical control device

Technical Field

The present invention relates to a numerical control device for controlling a machine tool.

Background

A machine tool is a machining device that applies force or energy to a workpiece using a tool to perform machining, i.e., removal machining, in which a part of the workpiece is not removed. In particular, in cutting, which is one of the removal processes, the cutting edge of the tool is brought into contact with the workpiece at a high speed, thereby causing shear fracture in the surface of the workpiece and performing a process of scraping an unnecessary portion of the workpiece.

Since the cutting process is a physical phenomenon in which a machining process and machine dynamics mutually affect each other, it is preferable to manage both processes simultaneously in order to manage a machining state. Here, the machining process means a series of processes of forming a machined surface while a tool tip penetrates a workpiece to generate chips. The mechanical dynamics represents the operation of a mechanical member when the mechanical member is vibrated by vibration sources inside and outside the machine. In general, cutting is a phenomenon in which various physical phenomena including the above-described machining process and mechanical dynamics complicatedly affect each other, and therefore, it is difficult to comprehensively analyze the physical phenomena. Therefore, in the production site, the evaluation target is limited, and the processing management according to the purpose is achieved.

As described above, in the cutting process, the machine dynamics and the machining process affect each other, and therefore, the state of the machine tool before or after the machining is different from the state of the machine tool during the machining. That is, the state of the machine tool during machining cannot be accurately estimated before or after machining. Therefore, it is preferred to use the information obtained during the machining to identify the mechanical dynamics and the machining process. By using the result of specifying the machining dynamics and the machining process, the worker at the production site can effectively perform improvement work such as management of the tool life, efficient setting of machining conditions, and design change of the fixing jig. This is expected to improve productivity.

As a method for identifying parameters based on information obtained by sequentially changing machining conditions during actual machining, patent document 1 proposes the following method. In the method described in patent document 1, an adaptive spectrum is calculated from displacements and forces generated when machining is performed at a plurality of spindle speeds, and a natural frequency of a tool is calculated from a peak obtained when the adaptive spectra of the spindle speeds are synthesized. In this method, the machine tool is caused to perform a machining operation so that the rotation speed of the main shaft is changed stepwise in a single operation of each feed shaft or in a combined operation of the feed shafts, and the adaptive spectrum is calculated using the detection results of the displacement and the force during machining.

Patent document 1: japanese patent laid-open publication No. 2017-94463

Disclosure of Invention

However, in the method described in patent document 1, various adaptive frequency spectrums are obtained by setting the feed amount at which chatter vibration does not occur and changing the spindle rotation speed in stages, and the natural frequency is calculated. Therefore, the method described in patent document 1 has a problem that only the natural frequency can be identified, and the machining characteristic parameter such as the relative cutting resistance cannot be identified. In the method described in patent document 1, when parameters other than the natural frequency are identified, other identification operations are required. In the method described in patent document 1, the spindle rotation speed is changed to a plurality of predetermined stages only in stages, and therefore, it takes time to acquire parameters corresponding to various spindle rotation speeds.

The present invention has been made in view of the above circumstances, and an object thereof is to obtain a numerical control device capable of efficiently identifying machining characteristic parameters in a short time.

In order to solve the above problems and achieve the object, the present invention is a numerical control apparatus for controlling an operation of a machine tool having a main shaft and a feed shaft and machining a workpiece with a tool, the numerical control apparatus including: and a constant motion generating unit that generates a constant motion command for changing the rotational speed and the feed speed of the spindle independently and continuously. In addition, the numerical control device includes: a data acquisition unit that synchronizes a control signal for controlling the machine tool generated based on the identification operation command and an operation state signal indicating an operation state of the machine tool operated based on the control signal and outputs the control signal and the operation state signal as identification data; and a vibration determination unit that determines whether the state of vibration of the machine tool is stable machining, chattering vibration, or forced vibration, based on the identification data. The numerical control device further includes a specifying unit that selects, as a selection parameter, a machining characteristic parameter that can be specified among machining characteristic parameters indicating characteristics of a machining phenomenon between the tool and the workpiece based on a determination result of the vibration determination unit, and specifies the selection parameter using specification data.

ADVANTAGEOUS EFFECTS OF INVENTION

The numerical control device according to the present invention has an effect that machining characteristic parameters can be identified efficiently in a short time.

Drawings

Fig. 1 is a block diagram showing a configuration example of a numerical control device according to embodiment 1.

Fig. 2 is a diagram showing an example of a pattern of the identified motion command generated by the identified motion generating unit according to embodiment 1.

Fig. 3 is a diagram showing an example of a pattern of the identified motion command generated by the identified motion generating unit according to embodiment 1.

Fig. 4 is a diagram showing an example of a pattern of the identified motion command generated by the identified motion generating unit according to embodiment 1.

Fig. 5 is a schematic view showing a case where disturbance force is transmitted to the table in embodiment 1 when the workpiece fixed to the table is vibrated by the cutting force.

Fig. 6 is a diagram showing an example of the rotation angle of the tool in which the tool tip contacts the workpiece in embodiment 1.

Fig. 7 is a diagram showing an example of the rotation angle of the tool in which the tool tip does not contact the workpiece in embodiment 1.

Fig. 8 is a view showing a state of cutting at the 1 st cutting edge in a case where an offset is generated between the tool center and the spindle rotation center in embodiment 1.

Fig. 9 is a view showing a state of cutting at the 2 nd cutting edge in a case where an offset is generated between the tool center and the spindle rotation center in embodiment 1.

Fig. 10 is a flowchart showing an example of the identification processing procedure in the identification unit according to embodiment 1 when the vibration determination unit determines that the vibration has occurred.

Fig. 11 is a flowchart showing an example of the operation of the numerical control device according to embodiment 1.

Fig. 12 is a diagram showing a configuration example of a processing circuit according to embodiment 1.

Fig. 13 is a block diagram showing a configuration example of the numerical control device according to embodiment 2.

Fig. 14 is a flowchart showing an example of the operation of the numerical control device according to embodiment 2.

Fig. 15 is a block diagram showing a configuration example of the numerical control device according to embodiment 3.

Fig. 16 is a block diagram showing a configuration example of the numerical control device according to embodiment 4.

Detailed Description

A numerical control device according to an embodiment of the present invention will be described in detail below with reference to the drawings. The present invention is not limited to the embodiments.

Embodiment 1.

Fig. 1 is a block diagram showing a configuration example of a numerical control device 1 according to embodiment 1 of the present invention. The numerical control device 1 according to embodiment 1 controls the operation of the machine tool 2 by transmitting a control signal to the machine tool 2, and receives an operation state signal indicating an operation state of the machine tool 2 from a sensor not shown.

The machine tool 2 has a main spindle and a feed shaft, and machines a workpiece with a tool. Specifically, the machine tool 2 performs cutting processing on a workpiece by operating at least one of a tool and the workpiece. For example, the work machine 2 includes: a spindle that imparts rotational motion to a tool or a workpiece; and a feed shaft which is a servo shaft for giving a position to the tool or the workpiece. The main shaft and the feed shaft each have a motor.

The machine tool 2 includes a sensor that detects an operation state of the machine tool 2 and outputs a detection result as an operation state signal. The sensors included in the machine tool 2 include sensors capable of detecting vibrations of at least one of the tool and the workpiece. The sensor capable of detecting the vibration of at least one of the tool and the workpiece is, for example, a linear encoder and a current sensor provided in advance in the machine tool 2 for feedback control of each motor of the machine tool 2. The linear encoder detects the position of each shaft of the machine tool 2, and the current sensor detects the motor current of the motor of each shaft. Other examples of sensors include an acceleration sensor, a position sensor, a force sensor, and a microphone. Next, as an example, the sensors included in the machine tool 2 are a linear encoder, a current sensor, and a force sensor. The force sensor is provided on or in a member such as a table constituting the feed shaft, for example. The position where the force sensor is provided is not limited to this, and may be a position where the force between the tool and the workpiece can be detected.

As shown in fig. 1, the numerical control device 1 includes a correction unit 11, a vibration determination unit 12, an identification unit 13, an identification motion generation unit 14, a drive control unit 15, and a data acquisition unit 16. The operation of each part of the numerical control device 1 according to embodiment 1 will be described.

The synchronous operation generating unit 14 generates a synchronous operation command for continuously and independently changing the spindle rotation speed and the feed speed of the machine tool 2, and outputs the synchronous operation command to the drive control unit 15. The spindle speed is the rotational speed of the spindle and indicates a number of revolutions of the spindle per unit time. The identification operation is an operation for causing the drive control unit 15 and the machine tool 2 to generate a control signal and an operation state signal, respectively, in order to obtain identification data used when the identification unit 13 executes identification processing described later. The constant operation command is a command generated for performing a constant operation, and includes a command for a spindle rotation speed and a command for a feed speed.

Fig. 2 to 4 are diagrams showing examples of the pattern of the same-fixed-motion command generated by the same-fixed-motion generating unit 14 according to embodiment 1. Hereinafter, the mode of identifying the operation command is also referred to as a command mode. Fig. 2 to 4 show command patterns in which the spindle rotation speed and the feed speed are continuously changed from the same fixed operation start time t1 to the same fixed operation end time t 2. In fig. 2 to 4, the horizontal axis represents time (time), the vertical axis represents the upper level of the spindle rotation speed, and the lower level of the spindle rotation speed. Hereinafter, the spindle rotation speed and the feed speed may be individually referred to as S, F.

Here, S0 represents the reference spindle speed before the same operation, and S1 represents the maximum value of the spindle speed during the same operation. T1 is a time constant when accelerating from a state where the spindle rotation speed is S0 to a state where the spindle rotation speed is S1. T2 is a time constant when accelerating from a state of a feed speed of F0 to a state of a feed speed of F1. Fig. 2 shows command patterns for acceleration and deceleration of the spindle rotation speed and the feed speed, respectively. In the example shown in fig. 2, after the spindle rotation speed is accelerated with a time constant T1, if the spindle rotation speed is called S1, the spindle rotation speed is decelerated. Then, if the spindle rotation speed is reduced to S0, S0 is maintained. If the spindle rotation speed is reduced to S0, the feed speed is accelerated to F1 with a time constant T2. Then, if the feed speed becomes F1, the feed speed is decelerated.

Fig. 3 shows a command pattern in which the feed speed is accelerated and then decelerated after the acceleration of the spindle rotation speed, and the spindle rotation speed is decelerated. Fig. 4 shows a command pattern in which the spindle rotation speed is accelerated and then decelerated, and the feed speed is repeatedly accelerated and decelerated in a change in the spindle rotation speed.

In fig. 2 to 4, an example is shown in which the spindle rotation speed is changed between S0 and S1 with S1 being the maximum value of the spindle rotation speed in the same operation, but the same operation generation unit 14 may set the minimum value S2 of the spindle rotation speed in the same operation and show a command pattern that changes in the range from S0 to S2. Similarly, the minimum value F2 of the feed speed in the same operation may be set as the feed speed, and the command pattern may be changed from F0 to F2.

Although the command pattern for acceleration/deceleration in a triangular wave shape is illustrated in fig. 2 to 4, the coincidence generating unit 14 can generate an arbitrary command pattern if the command pattern is a command pattern in which the spindle rotation speed and the feed speed are continuously accelerated/decelerated. For example, the fixed motion generating unit 14 may generate a command pattern that changes in a sinusoidal or sigmoidal manner instead of a triangular wave.

As described above, the identical operation generating unit 14 can generate the identical operation including various combinations of the spindle rotation speed and the feed speed by changing the spindle rotation speed and the feed speed independently from each other.

It is known that the magnitude of a cutting force, which is a force generated when a tool cuts a workpiece, mainly depends on the feed amount per 1 blade, and the vibration cycle of the cutting force mainly depends on the spindle rotation speed. Therefore, in general, when the spindle rotation speed and the feed speed are changed, they are changed at the same rate. As a result, the load applied to the tool edge becomes constant, and the magnitude of the cutting force generated by the cutting edge of the tool 1 does not change. Since the identical operation generating unit 14 changes the spindle rotation speed and the feed speed independently of each other, the magnitude and amplitude of the cutting force can be changed variously, and further, various vibration states described later can be generated in the machine tool 2 in the identical operation.

The drive control unit 15 generates a control signal for controlling the machine tool 2 such that the main shaft and the feed shaft of the machine tool 2 operate in the operation defined by the identified operation command, based on the identified operation command generated by the identified operation generating unit 14. Here, the control signal is a command for the main shaft and the feed shaft of the machine tool 2, and includes at least 1 of a position command, a speed command, and a current command for each of the motors for the main shaft and the feed shaft. Further, when the identical operation command is not input from the identical operation generating unit 14, that is, during the normal machining operation, the drive control unit 15 generates a control signal for the machine tool 2 based on the machining path and the reference spindle rotation speed and the reference feed speed in the machining path. The drive control unit 15 acquires a correction signal from the correction unit 11 described later, corrects the control signal for the machine tool 2 based on the correction signal, and outputs the corrected control signal to the machine tool 2.

The drive control unit 15 is preset with a machining path and a reference spindle rotation speed and a reference feed speed in the machining path. The machining path and the reference spindle rotational speed and the reference feed speed in the machining path may be given by a numerical control program. When the identical operation command is input from the identical operation generating unit 14, the drive control unit 15 also generates a control signal so that only the spindle rotation speed and the feed speed are changed in accordance with the identical operation command without changing the set machining path. The machine tool 2 includes a motor and a motor control device for each axis, and the motor control device controls the motor based on a feedback signal such as a control signal, a position, a speed, and a motor current received from the drive control unit 15. The feedback signal of the position and the speed is calculated based on the position detected by the linear encoder, and the feedback signal of the motor current is calculated based on the detection result of the current sensor. The feedback signals of the position, the speed, and the motor current are hereinafter referred to as a position feedback signal, a speed feedback signal, and a current feedback signal, respectively.

The data acquisition unit 16 synchronizes the control signal output from the drive control unit 15 with an operation state signal indicating the operation state of the work machine 2 operated based on the control signal and outputs the control signal and the operation state signal as identification data. Specifically, the data acquisition unit 16 synchronizes the data included in the control signal output from the drive control unit 15 and the operation state signal output from the sensor of the work machine 2 with time, and outputs the synchronized data to the vibration determination unit 12 and the synchronization unit 13. As described above, the operation state signal is a signal indicating the operation state of the work machine 2, and includes a signal capable of detecting vibration of at least one of the tool and the workpiece. Here, since the linear encoder, the current sensor, and the force sensor are provided as the sensors as described above, the data acquisition unit 16 can acquire feedback signals of the position, speed, and current of the main shaft and the feed shaft, and force, torque, and the like detected by the force sensor as the operation state signals. Hereinafter, actual measurement values such as force and torque detected by the force sensor are also referred to as force information. Since the operation state signal is generated after the machine tool receives the control signal, the operation state signal is temporally delayed from the corresponding control signal due to the influence of time required for communication and the like. Therefore, the data acquisition unit 16 compensates for the time difference between the two signals by shifting the data included in the operation state signal or the data included in the control signal by a time corresponding to the difference in communication time or the like. The data acquisition unit 16 integrates the data whose temporal offset has been compensated, that is, the synchronized data, into the identification data, and outputs the data to the vibration determination unit 12 and the identification unit 13.

The vibration determination unit 12 determines whether or not vibration has occurred in the machine tool 2 using the identification data, determines the type of vibration when it is determined that vibration has occurred, and outputs the determination result to the identification unit 13. Next, the details of the vibration determination unit 12 will be described. The vibration determination unit 12 determines whether or not vibration has occurred, and indicates vibration having a larger amplitude than a vibration component caused by the cutting force of the tool and the workpiece.

The determination of the occurrence of vibration by the vibration determination section 12 is performed by a known unit. For example, it is determined that vibration has occurred when a force or torque indicated by force information output from the force sensor exceeds a predetermined amplitude in a time region. The type of signal used for vibration determination is not limited to force information, and for example, the vibration determination unit 12 may determine whether or not vibration has occurred using a current feedback signal included in the operation state signal. The vibration determination unit 12 may convert a signal used for determining whether or not vibration has occurred into a signal in a frequency region, and determine that vibration has occurred when a vibration component having a maximum amplitude in the frequency region exceeds a predetermined amplitude.

In addition, there are forced vibration and self-excited vibration in the vibration phenomenon, and chatter vibration is one of the self-excited vibrations. The forced vibration is a vibration phenomenon in which a cutting force acts as an oscillation source and a member existing in the vicinity of a tool or a workpiece is excited. It is known that, by this property, the vibration frequency of the forced vibration is an integral multiple of the basic cutting frequency. On the other hand, self-excited vibration, that is, chattering vibration is a vibration phenomenon that occurs due to instability of a system composed of a cutting force and displacement of the member. From this property, it is known that the vibration frequency of the chatter vibration is a non-integral multiple of the basic cutting frequency. In the above, the basic cutting frequency is a frequency obtained by multiplying the spindle rotation speed by the number of tool edges.

When determining that vibration has occurred, the vibration determination unit 12 determines the type of vibration. Specifically, the vibration determination unit 12 determines whether the generated vibration is forced vibration or chattering vibration as the determination of the type of vibration. The type of vibration is determined based on whether the determined frequency of the vibration is an integral multiple of the basic cutting frequency. That is, the vibration determination unit 12 determines forced vibration if the frequency of the vibration is an integral multiple of the basic cutting frequency, and determines chatter vibration if the frequency is a non-integral multiple of the basic cutting frequency.

When the vibration determination unit 12 determines that no vibration has occurred, it determines that stable machining is performed. The stable machining is a machining state in which only a vibration component due to a cutting force of the tool and the workpiece is generated, and a vibration in the vicinity of a natural frequency of the member is not excited.

The vibration determination unit 12 always executes the above-described processing to determine which of the stable machining, the forced vibration, and the chattering is the same determination data at each time, and outputs the determination result to the determination unit 13 as a vibration determination result. That is, the vibration determination unit 12 determines which of a plurality of states, i.e., the stable machining, the forced vibration, and the chattering vibration, the vibration state of the machine tool 2 is based on the identification data.

The identification unit 13 selects, as a selection parameter, a machining characteristic parameter that can be identified among the machining characteristic parameters based on the determination result of the vibration determination unit 12, and identifies the selection parameter using identification data input from the data acquisition unit 16. The identification unit 13 further selects, as a selection parameter, a dynamic characteristic parameter that can be identified among the dynamic characteristic parameters, based on the determination result of the vibration determination unit 12. Hereinafter, the selection parameter is also referred to as an identifiable parameter. The identification unit 13 outputs the result of the identification process to the correction unit 11. The identification processing is executed using identification data and processing condition information. The machining condition information is information indicating a machining condition in the same operation, and is information set in advance in the same unit 13. The machining condition information includes, for example, a tool diameter, a tool edge number, a tool torsion angle, a tool axial feed amount, a tool radial feed amount, and a machining pattern of an up-cut or an down-cut.

In addition, although an example in which the identification unit 13 identifies both the dynamic characteristic parameter and the machining characteristic parameter will be described below, the identification unit 13 may identify only either the dynamic characteristic parameter or the machining characteristic parameter. For example, the identification unit 13 selects, as a selection parameter, a machining characteristic parameter that can be identified among the machining characteristic parameters based on the determination result of the vibration determination unit 12, and identifies the selection parameter using identification data.

Generally, the spindle rotation speed and the feed speed in machining are specified at constant values. In this case, the identification unit 13 can acquire only identification data when machining is performed at a set of spindle rotation speed and feed speed. Since the identification data includes the operation state signal detected by the sensor of the machine tool 2 as described above, the identification unit 13 can acquire only the operation state signal when the machining is performed at a set of the spindle rotation speed and the feed speed. However, in the present embodiment, since the identification operation generating unit 14 generates the command in which the spindle rotation speed and the feed speed are continuously changed, the identification unit 13 can acquire the operation state signal in the case where the machining is performed at the spindle rotation speed and the feed speed which are differently combined at each time.

Here, the dynamic characteristic parameter and the machining characteristic parameter will be described. The dynamic characteristic parameter is a parameter indicating the characteristics of a dynamic model described later, and is a parameter indicating the characteristics of the vibration of the work machine 2. The dynamic characteristic parameters are, for example, equivalent mass, damping coefficient, natural vibration frequency. On the other hand, the machining characteristic parameter is a parameter indicating the characteristic of a machining process model described later, and is a parameter indicating the characteristic of a machining phenomenon between the tool and the workpiece. The machining characteristic parameters are, for example, relative cutting resistance, edge force, tool eccentricity, tool wear amplitude.

The dynamic model is a mathematical model describing dynamics of a machine member, a tool, and a workpiece inside the machine tool 2. Next, an example of the kinetic model will be described. Fig. 5 is a schematic view showing a case where disturbance force is transmitted to the table in embodiment 1 when the workpiece fixed to the table is vibrated by the cutting force. Fig. 5 shows an example of milling of the machine tool 2 by rotation of the tool 33. In fig. 5, a configuration example is assumed in which a workpiece 32 is placed on a table 31 constituting a drive shaft, and a tool system 34 constituting a spindle holds a tool 33. In fig. 5, a relative displacement 35 shows a relative displacement of the workpiece tip in the vibration direction with respect to the table 31, a cutting force 36 shows a cutting force in the workpiece 32, and a disturbance force 37 shows a disturbance force transmitted to the table 31. The relationship among the cutting force 36, the disturbance force 37, and the relative displacement 35 at this time can be expressed by the following equation (1). The dynamic model shown in equation (1) is a mathematical model for calculating the disturbance force 37 transmitted to the feed axis by the mechanical structure including the tool 33 or the workpiece 32 when the cutting force 36 is generated, and calculating the positional deviation generated at each feed axis by the mechanical structure when the cutting force 36 is generated.

Formula 1

In this connection, it is possible to use,

f_c: cutting force, f_d: interference force, m_t: the equivalent mass is that of the material,

x: relative displacement of the front end of the workpiece with respect to the vibration direction of the table

c_t＝2m_tζω_n，

ζ: attenuation coefficient, ω_n: natural frequency of vibration

The dynamic model shown in equation (1) is described with the workpiece 32 on the table 31 as a 1-degree-of-freedom vibration system, but the dynamic model is not limited to the above example. For example, the vibration system may be described as a multi-degree-of-freedom vibration system including a fixed portion for fixing the workpiece 32 and the table 31. Further, a dynamic model relating to a tool side member including the tool 33, the tool system 34, and the spindle motor can be set. Further, a dynamic model may be set as a vibration system in which a workpiece side member and a tool side member including a fixing portion for fixing the workpiece 32 and the table 31 are combined.

The machining process model is a mathematical model describing a cutting process between a tool and a workpiece. An example of the machining process model is shown in the following equation (2).

Formula 2

f_c: cutting force, K^c: relative cutting resistance, K^ce: the force of the edge is applied to the edge,

a: axial feed amount of the tool, h: the thickness of the workpiece is cut off,

tool rotation angle, t: time of day

The meshing angle of the cutter is set according to the design,

non-engagement angle of tool

The above equation (2) is an equation for calculating the cutting force applied to the workpiece 32 by the tool 33 based on the cutting thickness corresponding to the rotation angle of the tool 33 at each time. Here, the cut-off thickness refers to a thickness of the workpiece 32 cut off when the tip of the tool 33, i.e., the tool tip, passes through the workpiece 32. As shown in fig. 6 and 7, the cutting force is calculated as a value equal to or greater than zero when the tool tip is at an angle at which the tool tip contacts the workpiece 32, but is calculated as zero when the tool tip is at an angle at which the tool tip does not contact the workpiece 32. Fig. 6 is a diagram showing an example of the rotation angle of the tool 33 in which the tool tip contacts the workpiece 32 in embodiment 1, and fig. 7 is a diagram showing an example of the rotation angle of the tool 33 in which the tool tip does not contact the workpiece 32. That is, at each rotation angle or timing of the tool 33, whether or not the tool is in contact with the workpiece is determined based on the positional deviation, the cut-out thickness is calculated when the tool tip is in contact with the workpiece 32, and the cut-out thickness is calculated as zero when the tool tip is not in contact with the workpiece 32.

The calculation expressed by the equation (2) is performed in 3 directions of the tangential direction, the radial direction, and the axial direction of the tool, and thus the cutting force in the 3 directions can be calculated. In the machining process model, the cutting force in the tool reference coordinate system is calculated by multiplying the cutting force having the 3-direction component by a rotation matrix corresponding to the tool rotation angle, which is the rotation angle of the tool 33, to perform coordinate transformation. Equation (3) shows an example of coordinate transformation.

Formula 3

f_cx: cutting force in X-axis direction, f_cy: cutting force in the Y-axis direction, f_cz: the cutting force in the Z-axis direction,

f_ct: tangential cutting force of the tool, f_cr: cutting force in the radial direction of the tool, f_ca: axial cutting force of tool

The calculation of the above-described equations (2) and (3) is performed by the number of tool cutting edges, and the calculation results are accumulated, whereby the cutting force generated by the entire tool can be finally calculated. The machining process model shown in equation (2) is a mathematical model for calculating the removal thickness based on the relative position between the tool tip and the workpiece 32 as the object to be machined of the tool 33 and the tool rotation angle, and calculating the cutting force generated between the tool and the workpiece based on the removal thickness. The cutting thickness in equation (2) can be calculated by equation (4) using the feed amount per 1 blade and the tool rotation angle.

Formula 4

c: feed per 1 blade

As another example, the cut thickness can also be calculated using equation (5).

Formula 5

v: tool center displacement amount in the tool radial direction, w: the displacement of the front processing surface in the radial direction of the cutter,

Δ r: correction quantity, N, corresponding to each tool tip_tooth: cutter point numbering

Equation (5) is a calculation equation in which a variation calculated from the difference between the current tool displacement and the pre-machining surface, which is the machining surface generated by the tool cutting edge 1 before the cutting edge, is added to equation (4), and the removal thickness is added by the correction amount corresponding to each tool cutting edge. In the calculation expressed by equation (5), the cut thickness is corrected by the difference between the displacement amount that affects the machining surface shape and the displacement amount that occurs at the current tool tip, within the displacement amount that occurs at the current tool tip and the displacement amount that occurs at the tool tip that is greater than or equal to 1 edge. That is, the removal thickness is calculated based on the difference between the trajectory generated by the current tool tip for cutting and the trajectory of the tool tip that affects the machined surface shape in the tool tip before 1 or more cutting edges with respect to the current tool tip.

Here, the tool center displacement v is a displacement amount corresponding to a component in the direction from the tool center to the tool edge in the relative displacement x in expression (1). The front machining surface displacement amount w is a displacement amount generated on the machining surface by the relative displacement x at the time of cutting by the tool tip at 1 or more blade front. The tool edge at 1 or more cutting edges is a tool edge related to cutting at a time earlier than a time based on the tool edge related to cutting. For example, in a tool with the number of blades of 2, when the tool tip in the current cutting is the 2 nd blade, the tool tip before 1 blade is the 1 st blade before 180 degrees of rotation, the 2 nd blade before 2 blades is the 2 nd blade before 360 degrees of rotation, and the tool tip before 3 blades is the 1 st blade before 540 degrees of rotation. When the tool is displaced during cutting and the cutting edge is temporarily separated from the workpiece 32, the current tool cutting edge cuts not only the pre-machined surface created by the tool cutting edge 1-point ahead but also the pre-machined surface created by the tool cutting edge 2-point ahead or more.

In the calculation shown in equation (5), the cut-out thickness is corrected by a correction amount corresponding to the tool edge number indicating the tool edge and the tool rotation angle. Here, the correction amount is introduced to correct a change in the cut thickness caused by cutting at a different rotation radius for each tool cutting edge. As an example of the correction amount to be introduced, the following is exemplified. For example, when a specific cutting edge is worn or curled, the radius of rotation of the cutting edge becomes smaller than that of other cutting edges, and therefore, correction amounts corresponding to the wear width, the curl width, and the like are added. As another example, in the tip-replaceable tool, when there is an attachment error of the tool tip, a correction amount corresponding to the attachment error is added. As another example, when the spindle rotation center does not coincide with the tool center, that is, when there is tool eccentricity, a correction amount corresponding to the tool eccentricity amount is added. Further, the center of the tool is the center of the circumscribed circle of the tool.

The tool eccentricity amount is an amount of correcting the cut thickness by an amount of increase or decrease in the rotation radius of the tool tip for each tool tip when an offset amount is generated between the tool center and the spindle rotation center as shown in fig. 8 and 9. Fig. 8 is a view showing a state of cutting at a 1 st cutting edge in a case where an offset is generated between a tool center and a spindle rotation center in embodiment 1, and fig. 9 is a view showing a state of cutting at a 2 nd cutting edge in a case where an offset is generated between a tool center and a spindle rotation center. The 1 st and 2

nd cutting edges

43 and 44 are cutting edges of the tool. In the example shown in fig. 8 and 9, there is a deviation between the tool center 41 and the spindle rotation center 42. In the case described above, it is necessary to correct the cut thickness with respect to the cut thickness in the case where there is no deviation, and the tool eccentricity amount indicates a correction amount at that time. That is, the tool eccentricity amount corresponding to the rotation angle of the tool 33 is added to or subtracted from the cut-out thickness. The example of correcting the cut thickness by the correction amount is not limited to the above example, and the correction amount may be appropriately changed in accordance with a phenomenon occurring at the tool cutting edge.

The machining process model is not limited to the formula (2). For example, the relative cutting resistance value can be changed using equation (2) in the case of a high speed at which the cutting speed is greater than or equal to the threshold value and in the case of a low speed at which the cutting speed is less than the threshold value. Further, a model to which a process damping force is added may be set on the right side of equation (2). Here, the process damping force is a force generated by the contact of the relief surface of the tool tip with the workpiece. The process damping can be expressed, for example, as a value obtained by multiplying the relief surface contact area by a process damping coefficient. In this case, the process damping coefficient becomes one of the machining characteristic parameters.

As another example, a machining process model for a tool in which a torsion angle exists may be used. Specifically, a model may be used in which the tool is divided into small-thickness tools in the axial direction, the cutting force of each of the divided small-thickness tools is calculated, and the cutting force is integrated in the tool axial direction to calculate the final cutting force. As another example, a model for calculating the cutting thickness and the cutting force by finite element analysis may be used.

In the following, when the kinetic model is the formula (1) and the machining process model is the formula (2), parameters that can be identified are determined based on the vibration determination result, and the processing for identifying the parameters will be described. The following candidates for the parameter that can be identified are equivalent mass, damping coefficient, natural frequency, relative cutting resistance, edge force, and tool eccentricity, which are dynamic characteristics.

The identification unit 13 performs the following processing in accordance with the vibration determination result if the vibration determination result indicating that the machining is stable, forced vibration, or chatter is input from the vibration determination unit 12 as the vibration determination result. In addition, it is rare that the forced vibration and the chattering vibration occur simultaneously, and in the case described above, it is determined that the chattering vibration occurs and the determination is made.

[ case where the judgment result is stable working ]

The identification unit 13 selects the machining characteristic parameters, i.e., the relative cutting resistance and the edge force, as identifiable parameters. The identification unit 13 identifies the relative cutting resistance and the edge force by the following processing. The identification unit 13 calculates the relative cutting resistance and the edge force according to equations (2) to (4) using the force information output from the force sensor and the machining conditions recorded in advance in the identification unit 13. That is, the relative cutting resistance and the edge force in equation (2) are calculated such that the calculated value of the force in each axial direction calculated when equation (3) is substituted for equations (2) and (4) substantially coincides with the actual measurement value of the force detected by the force sensor. The calculation method of the relative cutting resistance and the edge force may be performed by using a known optimization method or numerical simulation. For example, a minimum 2 multiplication or gradient method can be used.

[ case where the judgment result is forced vibration ]

The identification unit 13 selects the attenuation coefficient and natural frequency, which are dynamic characteristic parameters, and the relative cutting resistance and edge force, which are machining characteristic parameters, as identifiable parameters. The identification unit 13 identifies the damping coefficient, the natural frequency, the relative cutting resistance, and the edge force by the following processing.

The identification unit 13 identifies the damping coefficient, the natural frequency, the relative cutting resistance, and the edge force according to equations (1) to (4) using the force information output from the force sensor and the machining conditions recorded in advance in the identification unit 13. Specifically, f in the following formula (6) obtained by modifying the formula (1)_dThe actual measurement value of the force detected by the force sensor is substituted.

Formula 6

Then, the calculated values of the forces in the respective axial directions calculated when equations (2) and (4) are substituted into equation (3) are substituted into f in equation (6)_c. At this time, since there is a combination of the attenuation coefficient, the natural frequency, the relative cutting resistance, and the edge force satisfying equation (6), the identification unit 13 calculates a combination of the attenuation coefficient, the natural frequency, the relative cutting resistance, and the edge force satisfying equation (6). Specifically, the identification unit 13 searches for the damping coefficient, the natural frequency, the relative cutting resistance, and the edge force by using the gradient method so that the error between both sides of equation (6) is minimized. As another method, the damping coefficient, the natural frequency, the relative cutting resistance, and the edge force can be calculated by the minimum 2-multiplication.

[ case where the judgment result is chattering ]

The identification unit 13 selects equivalent mass, attenuation coefficient, natural frequency, and machining characteristic parameters, i.e., relative cutting resistance, edge force, and tool eccentricity, as parameters that can be identified. The identification unit 13 identifies the equivalent mass, the damping coefficient, the natural frequency, the relative cutting resistance, the edge force, and the tool eccentricity amount by the following processing.

The identification unit 13 identifies the equivalent mass, the damping coefficient, the natural frequency and the relative cutting resistance, the edge force, and the tool eccentricity according to equations (1), (2), (3), and (5) using the force information output from the force sensor and the machining conditions recorded in advance in the identification unit 13. Specifically, the equivalent mass, the damping coefficient, the natural frequency and the relative cutting resistance, the edge force, and the tool eccentricity can be identified in the order shown in fig. 10.

Fig. 10 is a flowchart showing an example of the identification processing procedure in the identification unit 13 of embodiment 1 when the vibration determination unit 12 determines that the vibration is generated. First, in step S1, the identification unit 13 sets an initial value for each set of parameters. The set of parameters at this time is a combination of dynamic characteristic parameters, i.e., equivalent mass, damping coefficient, natural frequency, and machining characteristic parameters, i.e., relative cutting resistance, edge force, and tool eccentricity.

In step S2, the identification unit 13 calculates the displacement amount satisfying both the kinetic model and the machining process model. For example, the displacement amount satisfying both the equation (1) as a kinetic model and the equations (2) and (5) as a machining process model is calculated. Here, the displacement amounts are the relative displacement x in the formula (1) and v, w in the formula (5).

In step S3, the similarity determination unit 13 calculates a disturbance force when the displacement amount is given to the dynamic model. For example, the identification unit 13 adds the displacement amount calculated in step S2 to the dynamic model, i.e., expression (1), to thereby generate the disturbance force f_dAnd (6) performing calculation.

In step S4, the identification unit 13 determines whether or not the error between the actual measurement value of the force detected by the force sensor and the calculated value of the force calculated in step S3 is less than or equal to an allowable value. If the error is less than or equal to the allowable value (step S4 Yes), the identification unit 13 ends the identification process with the value of the parameter group at that time as the identification result. When the error exceeds the allowable value (No at step S4), the identification unit 13 updates the values of the parameter group at step S5, and returns to the process at step S2.

As the updating method of the parameters in step S5, for example, a method of increasing or decreasing each parameter by a predetermined amount can be used. Note that the identification process in the identification unit 13 when the vibration determination unit 12 determines that the vibration is generated is not limited to the process of steps S1 to S5 described above. For example, each parameter may be calculated by combining equations (1), (2), (3), and (5) and using a minimum 2 multiplication.

Returning to the description of fig. 1, the correction unit 11 receives the dynamic characteristic parameter and the machining characteristic parameter, which are the identification results, from the identification unit 13, and outputs a correction signal for correcting the operation of the machine tool 2 to the drive control unit 15 based on the identification results. Specifically, simulations relating to machine dynamics and machining processes are executed in the correction unit 11, and a combination of the spindle rotational speed and the feed speed at which the vibration amplitude of the tool tip is equal to or smaller than a predetermined value is calculated. The correction unit 11 generates a correction signal for correcting the spindle rotation speed and the feed speed based on the calculated spindle rotation speed and feed speed, and outputs the correction signal to the drive control unit 15. Here, the predetermined value is a value set in advance in the correcting unit 11 and is a value set so as to satisfy the size intersection in which the machining result is determined. The target of the correction may include the amount of feed in the tool axial direction or the tool radial direction, in addition to the spindle rotation speed and the feed speed.

An example of the operation of the numerical control device 1 according to embodiment 1 described above will be described with reference to fig. 11. Fig. 11 is a flowchart showing an example of the operation of the numerical control device 1 according to embodiment 1. In step S11, the numerical control device 1 starts the synchronization operation. Specifically, the identical operation generating unit 14 generates an identical operation command, and the drive control unit 15 outputs a control signal to the work machine 2 so that the work machine 2 executes an operation specified by the identical operation, with respect to the work machine 2.

In step S12, the vibration determination unit 12 acquires the identification data. Specifically, the data acquisition unit 16 acquires a control signal from the drive control unit 15, acquires an operation state signal from a sensor of the work machine 2, generates identification data in which a time deviation between the two is compensated, and outputs the identification data to the vibration determination unit 12 and the identification unit 13.

In step S13, the vibration determination unit 12 determines the state of vibration based on the identification data. Specifically, the vibration determination unit 12 determines whether or not vibration has occurred based on the operation state signal of the identification data, and if it is determined that vibration has not occurred, determines that the state of vibration is stable machining. When it is determined that vibration has occurred, the vibration determination unit 12 determines which of forced vibration and chatter vibration is based on the frequency of the vibration. The vibration determination unit 12 outputs the result of the determination of the state of vibration to the identification unit 13 as a vibration determination result.

In step S14, the identification unit 13 selects an identifiable parameter based on the identification data and the vibration determination result. Specifically, the identification unit 13 selects an identifiable parameter from among the dynamic characteristic parameter and the machining characteristic parameter in accordance with the vibration determination result.

In step S15, the identification unit 13 identifies the parameter that can be identified selected in step S14, using the identification data. In step S16, the numerical control device 1 corrects the operation of the machine tool 2 based on the result of the identification after the end of the identification operation up to step S15, that is, in the normal machining operation. Specifically, the correction unit 11 generates a correction signal for correcting the operation of the work machine 2 based on the identification result calculated by the identification unit 13, and outputs the correction signal to the drive control unit 15. The drive control unit 15 generates a control signal based on the machining path, the reference spindle rotational speed and the reference feed speed in the machining path, and the correction signal, and outputs the control signal to the machine tool 2.

The numerical control device 1 can identify the parameters by executing a series of processes from step S11 to step S15 at any time during the machining. After the identification operation, the processing state can be improved by using the identification result in the processing of step S16.

Next, a hardware configuration of the numerical controller 1 will be explained. Each part of the numerical control apparatus 1 shown in fig. 1 is realized by a processing circuit. The processing circuitry may be circuitry with a processor or may be dedicated hardware.

In the case where the processing circuit is a circuit having a processor, the processing circuit is, for example, a processing circuit having a configuration shown in fig. 12. Fig. 12 is a diagram showing a configuration example of a processing circuit according to embodiment 1. The processing circuit 200 has a processor 201 and a memory 202. When each unit of the numerical control device 1 is realized by the processing circuit 200 shown in fig. 12, the processor 201 reads out and executes a program stored in the memory 202, thereby realizing them. That is, when each part of the numerical control apparatus 1 is realized by the processing circuit 200 shown in fig. 12, the functions thereof are realized by using software, that is, a program. The memory 202 is also used as a work area of the processor 201. The processor 201 is a cpu (central Processing unit) or the like. The memory 202 is, for example, a nonvolatile or volatile semiconductor memory such as a ram (random Access memory), a rom (read Only memory), a flash memory, or a magnetic disk.

When the processing circuit implemented by each unit of the numerical control device 1 is dedicated hardware, the processing circuit is, for example, an fpga (field Programmable Gate array) or an asic (application Specific Integrated circuit). Each part of the numerical control apparatus 1 may be realized by combining a processing circuit having a processor and dedicated hardware. Each part of the numerical control apparatus 1 can be realized by a plurality of processing circuits.

As described above, the numerical control device 1 according to embodiment 1 generates a command whose speed changes continuously for the main shaft and the feed shaft, and gives the command to the main shaft and the feed shaft independently, thereby causing the machine tool to perform the identical operation. The numerical control device 1 according to embodiment 1 determines the state of vibration of the machine tool 2 based on the identification data collected by the identification operation, and identifies the machining characteristic parameters that can be identified according to the determination result. As described above, the numerical control device 1 according to embodiment 1 can efficiently identify machining characteristic parameters in a short time. Further, the numerical control device 1 according to embodiment 1 can also identify the dynamic characteristic parameter that can identify the vibration state according to the determination result. Further, the numerical control device 1 according to embodiment 1 can reproduce a plurality of types of vibration states in one identical operation with respect to the machine tool 2, and therefore, an operator can efficiently perform the identical operation in a short time without changing the machining conditions each time. By reproducing the chattering state, the dynamic characteristic parameter and the machining characteristic parameter can be estimated at the same time. As a result, the numerical control device 1 according to embodiment 1 can correct the control signal for the machine tool based on the identification result, and thus can continue the machining without causing a machining failure. Further, if the main shaft rotation speed is varied stepwise and is identified, only the peak values that are candidates for the natural frequency can be discretely searched. In contrast, in the present embodiment, since the commands for continuously changing the speed are generated for the spindle and the feed shaft as described above, the dynamic characteristic parameter and the machining characteristic parameter can be identified with high accuracy as compared with the case where the spindle rotation speed is changed stepwise.

The kinetic model and the machining process model are not limited to the above equations (1) and (2), and may be appropriately modified according to the machine structure and the machining method. Therefore, the dynamic characteristic parameters are not limited to the equivalent mass, the damping coefficient, and the natural frequency, and similarly, the machining characteristic parameters are not limited to the relative cutting resistance, the edge force, and the tool eccentricity amount. The dynamic characteristic parameters and the machining characteristic parameters can be appropriately changed in accordance with the dynamic model and the machining process model, and the same effects as those of embodiment 1 are obtained.

In embodiment 1, the configuration in which 1 machine tool 2 is controlled by 1 numerical controller 1 has been described, but 2 or more machine tools may be connected to the numerical controller 1. For example, by generating a command for changing the spindle rotation speed for the 1 st machine tool, generating a command for changing the feed speed for the 2 nd machine tool, and simultaneously giving an operation command to each machine tool, the same effect can be achieved in a shorter time than when 1 machine tool is operated. In embodiment 1, the machine tool 2 that performs milling by rotation of the tool is described, but the present invention can also be applied to a machine tool that performs turning by rotation of a workpiece.

In embodiment 1, the force sensor directly detects the force, but the force sensor indirectly estimates the force using another sensor can also have the same effect as embodiment 1. For example, using the motor current command, i.e., the reference motor current and the position detected by the linear encoder, the data acquisition unit 16 or the identification unit 13 can calculate the force by the following expression (7).

Formula 7

f_est＝K_TI_ref-Mü …(7)

f_est: interference force of servo axis, K_T: the torque constant of the motor is constant and the torque is constant,

I_ref: referring to the motor current, M: feed shaft equivalent mass, u: linear encoder detecting position

As another example, the force can be calculated similarly using an acceleration sensor. In this case, the data acquisition unit 16 or the identification unit 13 can calculate the force by the following expression (8) using the acceleration detected by the acceleration sensor.

Formula 8

f_est＝K_TI_ref-Mα …(8)

α: acceleration sensing detection amount

Equations (7) and (8) are calculation equations of force when the feed shaft is regarded as 1 inertial body, but calculation equations regarded as multiple inertial bodies may be used as appropriate depending on the structure of the feed shaft. Further, a term for compensating for the frictional force may be added.

Embodiment 2.

Fig. 13 is a block diagram showing a configuration example of a numerical control device according to embodiment 2 of the present invention. In embodiment 1, an example in which the identification processing is performed based on the control signal and the operation state signal during a period in which the identification operation is performed once has been described. In embodiment 1, if chattering vibration does not occur in one identical operation, there is a parameter that cannot be identified between the dynamic characteristic parameter and the machining characteristic parameter. In embodiment 2, an example of correcting the same-timing operation when no chattering vibration occurs at the time of executing the same-timing operation will be described. Hereinafter, the same reference numerals are used for components having the same functions as those in embodiment 1, and redundant description thereof will be omitted. The following description focuses on differences from embodiment 1.

As shown in fig. 13, the numerical control device 1a is the same as embodiment 1 except that it includes an identification unit 13a and an identification motion generation unit 14a instead of the identification unit 13 and the identification motion generation unit 14 of embodiment 1. The identification unit 13a and the identification motion generation unit 14a are realized by a processing circuit in the same manner as the identification unit 13 and the identification motion generation unit 14 of embodiment 1.

The same section 13a selects parameters that can be identified from among the dynamic characteristic parameters and the machining characteristic parameters, using the vibration determination result input from the vibration determination section 12, as in the same section 13 of embodiment 1. Further, the identification unit 13a executes identification processing for identifying the selected parameter that can be identified based on identification data input from the data acquisition unit 16, and outputs the result of the identification processing to the correction unit 11, as in the identification unit 13 of embodiment 1. The identification processing is executed by the same method as the identification unit 13 of embodiment 1 using the identification data and the processing condition information.

Then, the identification unit 13a sets at least 1 of the dynamic characteristic parameter and the machining characteristic parameter as a parameter to be identified. The identification unit 13a outputs an identification operation correction signal to the identification operation generation unit 14a described later when an unidentified parameter is present among the parameters to be identified after the identification processing is performed once or more. The uniform motion correction signal is a signal indicating the presence of an unidentified dynamic characteristic parameter or machining characteristic parameter.

The constant operation generating unit 14a generates a constant operation command for changing the spindle rotation speed and the feed speed of the machine tool, and outputs the constant operation command to the drive control unit 15, in the same manner as the constant operation generating unit 14 of embodiment 1.

The identified motion generating unit 14a corrects the command pattern of the identified motion based on the identified motion correction signal output from the identified unit 13 a. As with the identification unit 13, the identification unit 13a can identify the most various types of parameters when the machine tool vibrates. Therefore, the same-timing-operation generating unit 14a corrects the same-timing operation so that chatter vibration occurs in the course of the same-timing operation by changing the range in which the spindle rotation speed or the feed speed is changed. Specifically, the identical operation generating unit 14a generates the identical operation command pattern in which at least 1 of the maximum value S1, the minimum value S2, the maximum value F1, and the minimum value F2 of the spindle rotation speed is changed at a predetermined ratio. Specifically, for example, at least 1 of the maximum value S1, the minimum value S2, and the maximum value F1 and the minimum value F2 of the spindle rotation speed is changed so that the range of change set by the previous identical operation is different for at least 1 of the spindle rotation speed and the feed speed.

An example of the operation of the numerical control device 1a according to embodiment 2 described above will be described with reference to fig. 14. Fig. 14 is a flowchart showing an example of the operation of the numerical control device 1a according to embodiment 2. In step S21, the numerical control device 1a starts the synchronization operation. In the first step S21, the identical operation generating unit 14a generates a first identical operation command, and the drive control unit 15 outputs a control signal to the machine tool so that the machine tool executes the operation specified by the identical operation.

In steps S22 to S25, the same processing as in steps S12 to S15 of fig. 11 described in embodiment 1 is performed. In step S26, the identification unit 13a determines whether or not to identify the parameter to be identified in advance, and if the identification is completed (step S26 Yes), the process proceeds to step S28. If there is any parameter that is not identified among the parameters of the predetermined identified objects (No at step S26), the numerical control device 1a corrects the identified operation command at step S27, and repeats the processing from step S21. Specifically, in step S27, the coincidence unit 13a outputs the coincidence operation correction signal to the coincidence operation generating unit 14a, corrects the coincidence operation command so that the coincidence unit 13a changes the range of at least 1 change in the shaft rotation speed and the feed speed, and outputs the corrected coincidence operation command to the drive control unit 15. In step S21 of the 2 nd time and thereafter, a control signal is generated for the machine tool 2 based on the same operation command corrected by the drive control unit 15 and output to the machine tool 2.

In step S28, the numerical control device 1a corrects the operation of the work machine 2 based on the identification result. Specifically, the correction unit 11 generates a correction signal based on the coincidence result calculated by the coincidence unit 13a after the coincidence operation is completed, and outputs the correction signal to the drive control unit 15, as in the correction unit 11 of embodiment 1. The drive control unit 15 generates a control signal based on the machining path, the reference spindle rotational speed and the reference feed speed in the machining path, and the correction signal, and outputs the control signal to the machine tool 2.

During machining, the numerical control device 1a repeatedly executes a series of processes from step S21 to step S27. That is, the identification unit 13a generates an identification operation correction signal instructing a change of an identification operation when there is an identification unfinished parameter among identification target parameters which are parameters set as an identification target after identification is performed using identification data of a period corresponding to an identification operation command, and outputs the same to the identification operation generation unit 14 a. Then, the identical operation generating unit 14a changes the identical operation command if receiving the identical operation correction signal, and the data acquiring unit 16 synchronizes the control signal generated based on the changed identical operation command with the operation state signal indicating the operation state of the work machine 2 operated based on the control signal and outputs the control signal as identical data to the vibration determining unit 12 and the identical operation unit 13 a. These operations are repeated until the identification of all the parameters set as the identification target is completed. This allows identification of all the dynamic characteristic parameters and machining characteristic parameters set as objects of identification. Further, by the processing of step S28, the machining state can be improved using the identification result. Here, although the processing flow in the case where the identical operation command is corrected after the completion of one identical operation has been described, the processing flow may be a processing flow in which the identical operation is corrected in the middle of the identical operation.

As described above, the numerical control device 1a according to embodiment 2 corrects the approval operation and performs the approval operation again when there is a parameter of the approval failure among the parameters of the predetermined approval target. Therefore, the numerical control device 1a according to embodiment 2 has an effect that, even when there are parameters that cannot be identified in the command pattern of the first identifying operation, the identifying operation is corrected to generate chattering vibration, thereby making it possible to identify all the parameters among the parameters of the identifying object that have been specified in advance.

Embodiment 3.

Fig. 15 is a block diagram showing a configuration example of a numerical control device according to embodiment 3 of the present invention. In embodiment 2, the identification operation is repeated until all the identification of the parameter of the identification target set in advance is completed. In embodiment 3, an example in which parameters of an identical object can be set from the outside will be described. Hereinafter, the same reference numerals are used for components having the same functions as those in embodiment 2, and redundant description thereof will be omitted. The following description focuses on differences from embodiment 2.

As shown in fig. 15, the numerical control device 1b according to embodiment 3 is configured such that an input unit 17 is added to the numerical control device 1a according to embodiment 2. The input unit 17 can receive an input of a parameter of a predetermined object from the outside. The input unit 17 can receive at least 1 input of the dynamic characteristic parameter and the machining characteristic parameter as a parameter to be identified from, for example, an external device or an operator. The input unit 17 may be a communication circuit for communicating with an external device, an interface circuit for an external medium for reading data from the external medium, or an input unit such as a keyboard or a mouse. When the input unit 17 receives an input from an operator, a display unit such as a monitor or the like is also used as the input unit 17. The parameter of the identified object may be input to the input unit 17 as a numerical control program, or may be input to the input unit 17 by an operator in a dialogue format. The input unit 17 may accept input of parameters of the same object in an interactive programming format. The input unit 17 outputs the received parameter of the identified object to the identifying unit 13 a. Examples of the case where the parameter of the identification target is designated by an operator or from the outside include a case where "a parameter that has already been identified by another means or the like is desired to be removed from the identification target" (case 1) and a case where "only the identification target having a high priority is desired to be identified and the time taken for identification is reduced" (case 2). Therefore, if the case 1 is assumed, for example, the identification completion parameter is displayed in the menu list so that the identification completion parameter can be distinguished from the identification completion parameter by inputting a value obtained by the past identification in advance, and thus the identification of the unidentified parameter becomes easy. In addition, if the case 2 is assumed, the parameter to be identified can be selected by a selection box or the like, and a display window in which the expected time is changed every time a check is input to the selection box is provided, whereby the operator can select the most parameters in the range within the same volume of the allowed time at the same time. The form of the interactive programming is not limited to these examples, and may be any form, but as described above, information to be considered by the operator for selection is displayed, so that the operator can easily select the parameters of the same object.

The identification unit 13a performs the same operation as in embodiment 2, using the parameter of the identified object input from the input unit 17 instead of the parameter of the identified object set in advance, as in the identification unit 13a of embodiment 2. The identification unit 13a may be capable of executing both an operation using a parameter of the identified object set in advance and an operation using the parameter of the identified object input from the input unit 17. The identification unit 13a outputs the result of the identification process to the correction unit 11. The operation of the correction unit 11 is the same as that of embodiment 1. The operation of the correction unit 11 when the parameter of the identification target is specified according to the numerical control program is as follows. In the numerical control program, information such as a machining path, a spindle rotation speed, a feed speed, and a tool number is generally described. When an operator designates a parameter of a predetermined object from the numerical control program, the numerical control program designates a machining path for performing a predetermined operation and the parameter of the predetermined object. When the identification by the identification unit 13a is completed, for example, the correction unit 11 continues to generate a correction signal such that the vibration amplitude of the tool edge is equal to or smaller than a predetermined value from the timing at which the tool number is changed to the timing at which the machining path in which the other identification operation is set is machined. The operation of the numerical control device 1b according to embodiment 3 other than the above is the same as the operation of the numerical control device 1a according to embodiment 2.

As described above, the numerical control device 1b according to embodiment 3 corrects the identification operation and performs the identification operation again when the parameter of the identification target set by the external input is present. Therefore, the same effect as that of embodiment 2 is obtained, and the parameter of the same target can be changed according to the desire of the operator or the like.

Embodiment 4.

Fig. 16 is a block diagram showing a configuration example of a numerical control device according to embodiment 4 of the present invention. In embodiment 3, a configuration is described in which parameters of an identical object can be set from the outside. In embodiment 4, a configuration in which a command mode for a predetermined operation can be set by an input from the outside will be described. Hereinafter, the same reference numerals are used for components having the same functions as those in embodiment 3, and redundant description thereof will be omitted. The following description focuses on differences from embodiment 3.

The numerical control device 1c is similar to the numerical control device 1b according to embodiment 3, except that it includes a constant operation generating unit 14b and an input unit 17a instead of the constant operation generating unit 14a and the input unit 17, as shown in fig. 16.

The input unit 17a can receive the parameter of the same object from the outside, and output the received parameter of the same object to the same unit 13a, as in the input unit 17 of embodiment 3. The input unit 17a can receive input of command pattern information for determining a command pattern of the predetermined operation from the outside. The input unit 17a outputs the received command pattern information to the synchronization operation generating unit 14 b. The command mode information is information indicating, for example, the spindle rotation speeds S0 and S1, the feed speeds F0 and F1, and the time constants T1 and T2 in fig. 2 to 4. That is, the command pattern information is information indicating a waveform corresponding to the time of the spindle rotation speed and the feed speed when the spindle rotation speed and the feed speed are changed by the same operation command. The command mode information is input to the input unit 17a, for example, as a numerical control program or by an interactive method. In addition, the command mode information may be input in the form of interactive programming. The command pattern information may be configured to be capable of setting a waveform from the outside in addition to the waveform shown in fig. 2 to 4 or information indicating the waveform.

The input unit 17a may be a communication circuit for communicating with an external device, an interface circuit for an external medium for reading data from the external medium, or an input unit such as a keyboard or a mouse, as in the input unit 17. When the input unit 17a receives an input from an operator, a display unit such as a monitor or the like is also used as the input unit 17 a. The parameter and the command pattern information of the identified object may be input to the input unit 17a from an external device in the form of a numerical control program, or may be input to the input unit 17a by an operator in the form of a dialog. The input unit 17a may create a program in the form of an interactive program, and specify parameters and command mode information of the same object by the program. The input unit 17a outputs the received parameter of the identified object to the identifying unit 13a, and outputs the received command pattern information to the identifying operation generating unit 14 b. The operation of the same section 13a and the correction section 11 is the same as that of embodiment 3.

The synchronous operation generating unit 14b generates a command pattern of the synchronous operation based on the command pattern information of the synchronous operation received by the input unit 17a, and outputs a synchronous operation command to the drive control unit 15. The uniform motion generating unit 14b corrects the command pattern of the uniform motion based on the uniform motion correction signal output from the uniform motion generating unit 13a, as in the uniform motion generating unit 14a of embodiment 2. The operation of the numerical control device 1c according to the present embodiment other than the above is the same as that of the numerical control device 1b according to embodiment 3.

As described above, the numerical control device 1c according to embodiment 4 can set the command mode for the identified operation by an external input in addition to the parameters of the identified object described in embodiment 3. Therefore, the numerical control device 1c according to embodiment 4 has an effect that the identification result can be calculated preferentially to the combination of parameters specified by the input from the outside.

The configuration described in the above embodiment is an example of the content of the present invention, and may be combined with other known techniques, and a part of the configuration may be omitted or modified without departing from the scope of the present invention.

Description of the reference numerals

1. 1a, 1b, 1c numerical control device, 2 machine tool, 11 correction unit, 12 vibration determination unit, 13 identification unit, 14 identification action generation unit, 15 drive control unit, 16 data acquisition unit, 17a input unit.

Claims

1. A numerical control device for controlling the operation of a machine tool having a main shaft and a feed shaft and machining a workpiece with a tool,

the numerical control device is characterized by comprising:

a fixed motion generating unit that generates a fixed motion command for changing the rotation speed and the feed speed of the spindle independently and continuously;

a data acquisition unit that synchronizes a control signal for controlling the machine tool generated based on the identification operation command and an operation state signal indicating an operation state of the machine tool operated based on the control signal and outputs the control signal and the operation state signal as identification data;

a vibration determination unit that determines whether the state of vibration of the machine tool is stable machining, chattering vibration, or forced vibration, based on the identification data; and

and a specifying unit configured to select, as a selection parameter, a machining characteristic parameter that can be specified, from among machining characteristic parameters indicating characteristics of a machining phenomenon between the tool and the workpiece, based on a determination result of the vibration determination unit, and to specify the selection parameter using the specification data.

2. The numerical control apparatus according to claim 1,

the identification unit further selects, as the selection parameter, an identifiable dynamic characteristic parameter from among dynamic characteristic parameters indicating characteristics of vibration of the machine tool, based on a determination result of the vibration determination unit.

3. The numerical control apparatus according to claim 1 or 2,

the identification unit generates a command change signal instructing a change of the identification operation and outputs the command change signal to the identification operation generation unit when there is an identification unfinished parameter among identification target parameters which are parameters set as an identification target after the identification is performed using the identification data for a period corresponding to the identification operation command,

the identified motion generating part changes the identified motion command if receiving the command changing signal,

the data acquisition unit synchronizes the control signal generated based on the modified identification operation command with an operation state signal indicating an operation state of the machine tool operated based on the control signal, and outputs the control signal and the operation state signal as the identification data to the vibration determination unit and the identification unit.

4. The numerical control apparatus according to claim 3,

the device has an input unit for receiving the input of the parameter of the identified object from the outside.

5. The numerical control apparatus according to claim 4,

the input unit further receives, from the outside, input of command mode information indicating waveforms of the rotational speed and the feed speed according to time when the rotational speed and the feed speed are changed by the synchronous operation command,

the identified motion generating unit generates the identified motion command based on the command pattern information.

6. The numerical control apparatus according to claim 4 or 5,

the input unit receives an input from the outside as a numerical control program.

7. The numerical control apparatus according to claim 4 or 5,

the input unit accepts input from the outside in the form of interactive programming.

8. The numerical control apparatus according to any one of claims 1 to 7,

the control device includes a correction unit that generates a correction signal for correcting the operation of the machine tool based on the identification result.