JPWO2013073436A1 - Machine tool cutting force detection device, cutting force detection method, machining abnormality detection method, and machining condition control system - Google Patents

Abstract

A method for accurately measuring a cutting force generated between a tool and a workpiece in a machining state in which the workpiece is moved while being tilted and rotated as in the case of cutting with a 5-axis machining apparatus. I will provide a.
An acceleration sensor is attached to a processing table or work material fixing jig with a built-in force sensor, and the acceleration value of the table is measured to cancel the influence of the inertia force of the work material and the fixing jig weight due to the cutting operation. The cutting force is calculated as follows. Cutting abnormality is detected from the difference between the measured cutting force and the theoretical cutting force.

Description

  The present invention relates to an apparatus for measuring a cutting force applied to a tool during machining, a cutting force detection method, a machining abnormality detection method, and a machining condition control system in a machine tool used for machining, and in particular, machining by a 5-axis machining machine. Related to cutting force detection device, cutting force detection method, machining abnormality detection method, and machining condition control system for detecting abnormalities such as tool wear and chatter vibration occurring in the machine and suppressing workpiece damage and chatter due to excessive wear It is.

  End milling using machine tools is a general processing method for processing metal parts into various shapes, and various methods are available by cutting the cutting blade attached to the rotary tool into the work material and removing the material. To a simple shape. Usually, the cutting process involves many steps of cutting out the shape of a part from square bar or round bar, and the amount of removal increases when machining a part with a complex shape. Higher efficiency is achieved by increasing the size. Here, in order to improve product performance in recent years, high-strength and difficult-to-cut materials such as Ni-base alloys and high-hardness cast steel materials are often applied to parts to be machined. For the reason that cutting is impossible and cutting becomes impossible, the cutting conditions have to be lowered to reduce the machining efficiency, which is a problem in increasing the efficiency. In addition, the machining shape is increasingly complex with a 3D curved surface, and there are many cases where machining is performed with a multi-axis machine tool such as a 5-axis machining center. It has become.

  In such materials and shapes, depending on the depth of cut and the rotational speed of the rotating shaft, the force applied to the cutting edge increases when the depth of cut and the number of rotations of the tool are increased. Processing troubles such as wear and breakage are likely to occur. When machining trouble occurs, the surface roughness of the machined part deteriorates or gets damaged, so the material is discarded, and high-strength materials and tools that are expensive are damaged and the disposal cost is increased. This is an issue of increasing manufacturing costs. Therefore, there is a technique to monitor the vibration state and machining state of the machine tool, give a command to the machine tool immediately before the abnormality occurs, change the machining condition, and build a machining control system that can stop the machining. It is necessary.

  With respect to such means, conventionally, there have been proposed methods for detecting a cutting abnormality by measuring a load during cutting by various methods. As shown in Patent Document 1 and Non-Patent Document 1, as a method of detecting cutting abnormality due to tool wear or the like, the motor load is estimated by measuring the drive current value of the motor used for spindle rotation and set in advance. There is known a method of detecting an abnormality by comparing with a threshold value. In Patent Document 2, as a method of setting a threshold value of a motor load, a change pattern of a motor drive current value is grasped in advance by experiment or simulation, and a threshold value is set for each machining path from the change pattern. Is disclosed. Patent Document 3 discloses a method of attaching a vibration sensor (acceleration sensor) to a machine tool, detecting vibration during cutting, and controlling the spindle speed of the machine tool so that the vibration is reduced. .

JP 59-146741 JP-A-5-337790 JP 2009-190160 A

JIPM Solution Visualization Study Group, “Technology for Visualizing Machining Points”, (2008), pp85-93,

  However, in the method of measuring the current value of the motor used for spindle rotation, it is difficult to accurately detect abnormalities in the machining phenomenon because the sensitivity and frequency responsiveness of the motor current value change to the cutting tool wear and chatter vibration are low. . In addition, with the method of detecting vibration during cutting by attaching a vibration sensor to the machine tool, abnormalities that change during cutting due to the progress of tool wear are detected in order to detect abnormalities after chatter vibration associated with cutting occurs. There is a problem that you can not. In addition, it is difficult to detect the occurrence of damage to the workpiece due to a minute chipping of the blade edge, and there is a problem in realizing prediction of occurrence of abnormality.

  In order to solve the above problem, a method of detecting an abnormality by measuring the cutting force applied to the work material and the tool is effective. In this case, a measuring instrument generally called a cutting dynamometer is used. In this method, a work material is attached to a jig incorporating a force sensor, and the forces in the XYZ axial directions applied to the tool and the work material are measured. When the cutting dynamometer is used, the force of contact between the work material and the tool can be directly measured, so that chatter vibration in which cutting vibration becomes abnormally large can be detected. Further, the progress of tool wear can also be grasped by the phenomenon of increased cutting load. In addition, tool abnormalities such as minute chipping can be detected from changes in the cutting force waveform. As described above, measuring the cutting force using a cutting dynamometer is an effective means for detecting abnormalities in the cutting state, but the premise for using the cutting dynamometer is that the horizontal or vertical direction is used. It is necessary to install a dynamometer. For example, in the case of a vertical machining center that gives a cut in the Z direction, it is common to install a cutting dynamometer on a processing table, fix the work material on it, and perform cutting. However, when machining with a 5-axis cutting machine in which the table tilts and rotates, the cutting dynamometer moves while tilting, so the weight of the cutting dynamometer and the work material acts as an inertial force, and cutting There is a problem that it becomes difficult to measure the cutting force because it is adjusted to the measured value of the dynamometer.

  The object of the present invention is a cutting force generated between a tool and a work material in a machining state in which the work material is moved while being tilted and rotated as in the case of cutting with a 5-axis cutting machine. The object is to provide a method for accurately measuring the above.

  In order to solve the above problems, in the present invention, an apparatus for detecting a cutting force during machining of a machine tool includes an arithmetic unit, a storage unit, an input unit, an output unit, and a communication unit, The unit stores the work material input from the input unit and the weight of the machining table, and the calculation unit outputs the output of the force sensor incorporated in the support unit of the machining table of the machine tool, or the communication unit, A force sensor measuring unit that receives the input via the input unit and measures a cutting force applied between a tool being cut and a work material, and an output of an acceleration sensor attached to a processing table of a machine tool. Or an acceleration measurement unit that accepts via the input unit and measures acceleration during movement of the machining table during cutting, calculates the inertial force from the measured acceleration and the weight of the machining table and the work material, Measured by force sensor And a cutting force conversion unit to obtain the cutting force of the corrected by correcting the cutting force by the inertia force and the output unit, configured to output the cutting force of the corrected.

  In order to solve the above-described problem, in the present invention, the cutting force detection device, the storage unit is further in theory of machining at a cutting position of discrete points arranged at predetermined intervals or predetermined rules on a machining tool path. The cutting force and the cumulative removal volume from the machining start position to each cutting position are input and stored in advance, and the calculation unit cuts in synchronization with the measurement of the force sensor and the acceleration sensor. A cutting coordinate value acquisition unit that acquires a coordinate value from a machine tool or an NC control device is further included, and the cutting force conversion unit is configured to calculate the cumulative removal volume at a cutting position on a processing tool path corresponding to the cutting coordinate value, Calculate from the information of the corresponding cutting position stored in the storage unit, correct the weight of the work material, calculate the inertial force based on the corrected weight of the work material, and by the force sensor Configured to obtain the cutting force of the corrected and corrected by the inertial force measured by the cutting force.

  In order to solve the above-described problem, in the present invention, the cutting force detection device, the storage unit is further performing a cutting operation based on a difference between a theoretical calculation cutting force and a cutting force obtained from a measured value. A threshold value for determining abnormality is stored in advance, and the calculation unit stores the theoretical cutting force at the cutting position on the processing tool path corresponding to the cutting coordinate value in the storage unit. A cutting force comparison unit that is calculated from the cutting force information of the cutting position and is compared with the corrected cutting force obtained from the measurement value, and a cutting force that is obtained from the measurement value calculated by the cutting force comparison unit An abnormality determination unit that detects a cutting abnormality by comparing a difference value with a theoretical cutting force with the threshold value for determining an abnormality during cutting stored in the storage unit. Configured.

  Further, in order to solve the above-described problems, the present invention provides a method for detecting a machining abnormality of a machine tool according to a machining theory in a storage device, a weight of a work material and a machining table, and a cutting position on a machining tool path. The force sensor built in the support part of the machining table of the machine tool, which stores the cutting force, the accumulated removal volume information from the machining start position to each cutting position, and the threshold value for judging abnormality during cutting The cutting force applied between the tool being cut and the work material is measured from the output of, and the acceleration during movement of the work table being cut is measured from the output of the acceleration sensor attached to the work table of the machine tool. In synchronism with the measurement of the force sensor and the acceleration sensor, a cutting coordinate value is obtained from a machine tool or an NC control device, and cutting on a machining tool path corresponding to the cutting coordinate value is performed. The cumulative removal volume in the setting is calculated to correct the weight of the work material, the inertial force is calculated based on the corrected work material weight and the acceleration, and the cutting force measured by the force sensor is used as the inertial force. The theoretical cutting force at the cutting position on the machining tool path corresponding to the cutting coordinate value is calculated from the cutting force information at the corresponding cutting position stored in the storage device, and is calculated from the measured value. Compared with the calculated cutting force after correction, the difference between the cutting force obtained from the measured value and the theoretical cutting force is calculated, and the threshold value stored in the storage unit In comparison, cutting abnormality was detected.

  In order to solve the above problems, the present invention provides a system for converging the machining conditions during machining of the machine tool to the machining conditions at the peak position within the stable region of the stability limit line, an arithmetic unit, a storage unit, and an input Unit, an output unit, and a communication unit, the storage unit is a conversion table of the change rate override amount and chatter index of the machining conditions input from the input unit or the communication unit, and various variables An initial value and a threshold value are stored, and the calculation unit Fourier-transforms a cutting force calculated from an output value of a force sensor and an acceleration sensor incorporated in a machining table of a machine tool into a relationship between a frequency and an amplitude to obtain a cutting force. A means for calculating a chatter index represented by a ratio between a vibration amplitude component and a tool vibration amplitude component, and the stored conversion table is searched using the calculated chatter index, and a conversion operation is performed. A means for obtaining a rate of change in barride amount, a means for updating the override amount to a newer override amount than the current override amount in accordance with the obtained override amount change rate and an override amount upper limit value in which chatter vibration has occurred in the past, and the new override amount Accordingly, there is provided a means for changing the target machining condition and a means for outputting the changed machining condition to the NC control device via the communication unit.

  According to the present invention, even during a cutting state in which a table or work material fixing jig that is fixed with a work material rotates and tilts and moves at a high speed as if cutting with a 5-axis machine, It becomes possible to accurately measure the cutting force applied to the material and the tool. As a result, it is possible to detect abnormalities such as chatter vibration, tool wear, and chipping during cutting in curved cutting, etc., so that it is possible to improve the efficiency of cutting and reduce the cost of workpieces. it can.

It is a figure which shows the function structure of the cutting force detection apparatus of this invention. It is a figure of the workpiece fixing jig for measuring the cutting force of Embodiment 1 of this invention. FIG. 2 is a configuration diagram of a state in which a work material fixing jig for measuring the cutting force according to the first embodiment of the present invention is attached to a machine tool. It is a block diagram of the machine tool for measuring the cutting force of Embodiment 2 of this invention. It is a figure for showing the direction of the cutting force during cutting. It is a figure which shows the item of the data record of a work material and table weight memory | storage part. It is a figure which shows the item of the data record of a cutting force and acceleration measured value memory | storage part. It is a figure which shows the item of the data record of a cutting position and process condition memory | storage part. It is a figure for demonstrating the method of calculating cutting force from a force sensor and an acceleration measured value. It is a figure for demonstrating the outline | summary of the process which selects a discrete cutting position on a tool path (C). It is the figure which showed the flowchart of the process of Embodiment 2 of this invention. It is a connection block diagram of the processing apparatus (machine tool), processing control PC (cutting force detection apparatus), and NC control apparatus of Embodiment 3 of this invention. It is a figure which shows the connection apparatus structure of the cutting force detection and abnormality detection system mounted in the process control PC. It is the schematic which shows an example of the input screen of the item input into machining control PC before starting a process. It is the schematic which shows an example of the input screen of work information (work material, initial weight, jig weight). (a) It is a figure which shows an example which output the cutting force waveform to the display apparatus as a cutting force output screen during a process. (b) It is the figure which output the average cutting force display screen with a long time interval of about 60 s from the time of pressing. It is a figure which shows the change of an acceleration with the acceleration waveform on a screen. It is a figure which shows an example which output the information of the weight change of the workpiece | work in process to the display apparatus. It is a figure which shows an example which output the vibration component of the cutting force which carried out the Fourier transform of the cutting force preserve | saved at the memory | storage device during the process to the relationship between a frequency and an amplitude on the output screen. It is a figure which shows an example which output the information at the time of detecting the chatter vibration in process on the display screen. It is a figure shown about the setting method of override amount change rate, and represents the conversion graph of override amount change rate ((alpha)) applied from a chatter index | exponent. (a) It is a figure which shows the example which changes override amount change rate ((alpha)) in step shape. (b) It is a figure which shows the example which used the straight line and the curve as a conversion graph. It is a figure explaining the peak position effective in derivation | leading-out of the initial machining conditions in the stability limit diagram in general cutting conditions. It is a figure for demonstrating the method of determining the upper limit (upper limit value) of an override amount in order not to use again the override amount which the chatter vibration generate | occur | produced when chatter vibration has generate | occur | produced. It is a flowchart which shows the 1st algorithm which controls a process condition dynamically. It is a flowchart which shows the 2nd algorithm which controls a process condition dynamically.

  Hereinafter, an example of an embodiment to which the present invention is applied will be described with reference to the drawings. However, in the following description, the same components are denoted by the same reference numerals, and repeated description is omitted.

  The first embodiment will be described with reference to FIGS. 1 to 3 and FIGS. FIG. 2 shows a configuration of a work material fixing jig according to the present invention. In the embodiment of FIGS. 2 and 3, a machining apparatus with three-axis control will be described as an example, but the number of control axes and the apparatus configuration are not limited to this. The work material 4 is fixed to the work material fixing jig 1, and the work material fixing jig 1 has force sensors 2 incorporated in four places. The force sensor 2 is a strain gauge configured for load measurement.

  An acceleration sensor 3 is attached to a part of the work material fixing jig 1. The acceleration sensor 3 is generally classified into three types, mechanical type, optical type, and semiconductor type, and the application of the present invention is not particularly limited, but in this embodiment, a semiconductor type triaxial acceleration sensor is used, Measure acceleration in three directions on the XYZ axes with one device.

  The workpiece 4 is cut by repeating the trajectory of the tool path 5 of a cutting tool (not shown). At this time, the fixing jig 1 is rotated in the θ1 and θ2 directions along with the movement in the X-Y direction by a machine tool (not shown). The acceleration sensor 3 measures the magnitude of acceleration / deceleration of the fixing jig 1 in these operations. The acceleration sensor 3 can detect acceleration values in the XYZ directions, and based on these acceleration values, the magnitude of the inertial force due to the work material and the weight of the fixture relative to the X, Y, and Z directions with reference to the tool Can be calculated.

  FIG. 3 shows a configuration diagram in which the fixing jig 1 shown in FIG. 2 is installed on the processing table 16 of the machine tool 10. In FIG. 3, a three-axis machine is used for explanation. However, the present invention is not limited to this, and a multi-axis machine tool having four or more axes can perform the same measurement as long as the fixing jig 1 can be installed. It is. In FIG. 3, a machine tool 10 holds a frame 11, a processing tool 14, a main shaft 13 that holds and rotates the processing tool 14, a main spindle stage 12 that moves the main shaft 13, a work material 4, and a work material that moves while holding the work material. The table 16 to be moved, the NC control device 17 for moving the driving device of each stage, the cutting force measuring sensor 2 for measuring the cutting force attached between the table 16 and the fixing jig 1, and the fixing jig 1. And an acceleration sensor 3 for measuring the acceleration value of the fixing jig 1, a communication with the NC control device 17, a cutting force measuring sensor 2, and a cutting force detecting device 30 for detecting a cutting force from the measured value of the acceleration sensor 3. The

In the case of the first embodiment, the cutting force detection device 30 of the present invention is realized by using, for example, a part of the functions shown in FIG. The cutting force detection device 30 includes a calculation unit 40, a storage unit 50, an input unit 61, an output unit 62, and a communication unit 63. The calculation unit 40 includes a force sensor measurement unit 41, an acceleration measurement unit 42, a cutting force conversion unit 43, a cutting coordinate value acquisition unit 44, a cutting force comparison unit 45, a removal volume calculation unit 46, and an abnormality determination unit 47. The storage unit 50 includes a work material / table weight storage unit 51, a cutting force / acceleration measurement value storage unit 52, a cutting coordinate value storage unit 53, a cutting position / processing condition storage unit 54, and an abnormality detection threshold storage unit 55. Have.
The communication unit 63 of the cutting force detection device 30 is connected to the machine tool 10, the NC control device 17, the three-dimensional CAD 80, and the three-dimensional CAM 81 via the network 90.

  Returning to FIG. 3, the machine tool 10 is configured to machine the shape of the work material 4 by rotating the tool 14 to cut into the work material 4 and removing the machining region 15. The cutting force is generated by the force that the tool 14 receives from the work material 4. A fixing jig 1 is installed on the XY table 16, and a work material 4 is fixed on the fixing jig 1. The work material 4 is cut by a cutting tool 14 chucked on the main shaft 13 of the machine tool 10. The force sensor measuring unit 41 of the cutting force detection device 30 measures the cutting force generated at this time based on the output of the force sensor 2 incorporating the fixing jig 1 and the force sensor amplifier 20 connected thereto. Further, an acceleration sensor 3 is attached to the side surface of the fixing jig 1, and the acceleration measuring unit 42 of the cutting force detection device 30 uses the fixing jig (table) during cutting by the outputs of the acceleration sensor 3 and the acceleration sensor amplifier 21. ) 1 and measure the magnitude of acceleration applied to the work material.

  The output of the force sensor amplifier 20 is input to the force sensor measurement unit 41 via the network 90 and the communication unit 63 or input to the force sensor measurement unit 41 via the input unit 61. Similarly, the output of the acceleration sensor amplifier 21 is input to the acceleration measuring unit 42 via the network 90 and the communication unit 63 or input to the acceleration measuring unit 42 via the input unit 61.

Fixing jig 1 supported by force sensor 2 using fx as the cutting force in the X direction measured by force sensor measuring unit 41, and using the acceleration value in the X direction as measured by acceleration measuring unit 42: ax. The cutting force conversion unit 43 calculates, for example, the cutting force Fx in the X direction by the following equation.
(Equation 1)
Fx = fx− (m1 + m2) × ax (Equation 1)
By calculating Fy and Fz by a similar calculation method, it is possible to accurately measure the cutting force with the influence of inertia force canceled. Here, the X, Y, and Z directions in the above formula indicate values based on the table, and when converting to the tool-based X, Y, and Z directions, the table tilt angle during cutting is determined from the machine tool. It can be converted by obtaining.

  Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 4 shows an example of a machine tool having a trunnion type table in which a circular table (fixing jig) 100 for fixing the work material 4 is rotated around the X axis by a turning shaft 101. A main shaft 13 is attached to the frame 11 of the machine tool 10 and is movable in the Y direction and the Z direction by a vertical movement mechanism and a horizontal movement mechanism (not shown). A tool 14 can be chucked below the main shaft 13. The trunnion-type table 101 can be moved in the X direction by a horizontal movement mechanism (not shown). The vertical movement and horizontal movement mechanism of the spindle 13, the horizontal movement mechanism of the table 101, and the turning movement of the table 101 The work material 4 can be cut. Force sensors are incorporated in four locations of the circular table (fixing jig) 100, and the cutting force with the work material 4 generated by cutting with the tool 14 can be detected. Moreover, the acceleration sensor 3 is attached to the circular table 100, and an acceleration value accompanying the table movement can be detected.

An inertial force consisting of the weight of the circular table 100 and the work material 4 is added to the force sensor 2 incorporated in the circular table 100 by the axial movement of the machine tool 10 accompanying cutting. By measuring the value with the acceleration sensor 3, the value of the inertial force can be calculated, and the cutting force generated between the tool 14 and the work material 4 can be accurately calculated. For example, consider a case where the cutting forces Fx and Fz generated between the tool 14 and the work material 4 are calculated in FIG. It is assumed that ax is obtained in the X direction and az is obtained in the Z direction by the output value from the acceleration sensor 3 at the time of cutting. If fx and fz are detected as output values of the force sensor at this time, the true cutting forces Fx and Fz are obtained by the following equations.
(Equation 2)
Fx = fx− (m1 + m2) × ax (Equation 2)
(Equation 3)
Fz = fz− (m1 + m2) × ay (Equation 3)
Here, m1 is the weight of the work material 4, and m2 is the weight of the circular table (fixing jig) 100.
As described above, the cutting force conversion unit 43 calculates the cutting force from the output values of the force sensor 2 and the acceleration sensor 3.

  The work material / table weight storage unit 51 of the cutting force detection device 30 in FIG. 1 receives input of the weights of the work material and the table (fixing jig) from the user via the input unit 61 before the start of cutting. And stored in the storage area shown in FIG.

  The cutting force / acceleration measurement value storage unit 52 represents the cutting force generated on the work material on the table (fixed jig) by the force sensor as the cutting force in the X, Y, and Z directions based on the table of the machine tool. 7a, and the acceleration measurement unit 42 measures the output of the acceleration sensor and converts it into accelerations in the X, Y, and Z directions with reference to the table of the machine tool. The cutting force is stored in the storage area shown in FIG. 7B, and the cutting force conversion unit 43 calculates the cutting force obtained by correcting the inertial force value from the output values of the force sensor 2 and the acceleration sensor 3, and the table of the machine tool is calculated. These are converted into reference cutting forces in the X, Y, and Z directions and stored in the storage area shown in FIG. 7 (c).

  The cutting coordinate value storage unit 53 inquires of the cutting position to the machine tool 10 or the NC control device 17 that the cutting coordinate value acquisition unit 44 is cutting, for example, the representative position on the central axis of the current tool 14. Stores data acquired with X, Y, Z axis coordinate values based on the machine tool spindle or table.

  When the NC position is created in the 3D CAM 81, the cutting position / machining condition storage unit 54 has no tool wear or chipping at the positions of a plurality of required points on the tool path (C). Calculate the theoretical cutting force when it is assumed that the tool in the initial state is performing the cutting operation, and the cumulative removal volume when machining the material in the material state from the cutting start point to that position The calculated data is created for each required point, and the data is input and stored as shown in FIG. The data to be stored will be described below.

  In the three-dimensional CAM 81, a tool path for performing cutting using a cutting tool 112 in which a processing area 111 is defined for the material CAD data 110 input from the three-dimensional CAD 80 and the processing area is selected. After determining 113, an NC program is created. In the present invention, in the process, as shown in FIG. 10C, for example, as shown in FIG. 10C, a point 114 advanced by the tool radius r from the starting point of machining is set as the first cutting position, and a predetermined point is determined from that point. If the point 115 advanced by the distance d is a second cutting position and a corner point (or turning point) 116 having a change in the path of the tool is present on the tool path, the point 117 before the tool radius r is A plurality of cutting positions are determined at discrete intervals on a series of tool paths according to a rule that the point 118 advanced by the tool radius r is determined as the third and fourth cutting positions. Then, the theoretical cutting force is calculated when it is assumed that the selected tool is performing the cutting operation at each cutting position in an initial state in which no tool wear or chipping occurs. In addition, the cumulative removal volume when the workpiece in the material state is machined from the cutting start point to each cutting position is calculated.

The three-dimensional CAM 81 downloads the calculated NC program to the NC control device 17, and downloads the theoretical cutting force and cumulative removal volume at each cutting position on the tool path to the cutting force detection device 30. The cutting force detection device 30 receives an input via the communication unit 63 and stores it in the cutting position / processing condition storage unit 54. As shown in FIG. 8, in the order of a series of tool paths, the cutting position is expressed in X, Y, Z axis coordinate values on the CAM, for example, in mm units, and the cutting force is expressed on the X, Y, Z axis on the CAM. The direction component is expressed in N units, for example, and the cumulative removal volume is expressed in m ³ units, for example.

  FIG. 9 is a diagram showing a flow from detecting the cutting force from the start of machining to detecting an abnormality based on the acquired cutting force, with the table weight and the workpiece weight as input values. By starting machining, a cutting force is generated between the work material 4 and the tool 14. With respect to this cutting force, temporary cutting force calculation (primary) is performed by the force sensor 2 incorporated in the fixing jig 1 shown in FIG. 2 or the circular table 100 of the machine tool 10 shown in FIG. At the same time, the acceleration value is detected by the acceleration sensor 3 attached to the fixing jig 1 or the circular table 100, and the inertial force is calculated from the table weight and the work material weight as input information. Then, the cutting force is corrected and calculated from the values of the cutting force (primary) and inertial force obtained from the detection result of the force sensor and the detection result from the acceleration sensor. Thereby, it is possible to detect an accurate cutting force even during cutting while the table of the machine tool is moving, and it is possible to use the cutting force for detection and determination of abnormalities such as chatter vibration and tool wear.

  FIG. 11 shows the table (fixed jig) weight and the work material weight as input information, as well as the cutting position information at a predetermined interval on the tool path, the theoretical cutting force at that position, and cumulative removal at the time of NC program creation. The flowchart of the detection method of a cutting force when the information of a volume is produced beforehand and those information is memorize | stored, and the processing abnormality determination method are shown. In particular, when cutting a large material or a work material with a large machining allowance, the weight of the work material may change greatly as the cutting progresses. This method shows a method of obtaining a more accurate cutting force when cutting such a work material.

  In step S101 of FIG. 11, an instruction for taking in the force sensor value, the acceleration sensor value, and the current cutting coordinate value is issued simultaneously. The output values of the force sensor and the acceleration sensor at this time are recorded in, for example, a latch circuit. At the same time, the current cutting position is inquired to the machine tool 10 or the NC control device 17.

  In step S102, the cutting force (fx, fy, fz) generated between the work material 4 and the tool 14 by the force sensor measuring unit 41 based on the output value of the force sensor, for example, X based on a table of a machine tool. , Y, Z coordinate system.

  In step S103, the acceleration (ax, ay, az) applied to the work material 4 and the table (fixing jig) 100 by the acceleration measuring unit 42 based on the output value of the acceleration sensor is, for example, X based on the table of the machine tool. , Y, Z coordinate system.

  In step S104, the answer of the current cutting position inquired to the machine tool 10 or the NC control device 17 in step S101 is received via the communication unit 63 and stored in the cutting coordinate value storage unit 53 as a cutting coordinate value.

  In step S105, the cutting position / processing condition data stored in the cutting position / processing condition storage unit 54 is used as a search key to determine which position on the tool path the cutting coordinate value is on. Then, data records of two cutting positions sandwiching the cutting coordinate value are read out. Then, assuming that the cutting coordinate values are interpolated along the tool path between the two cutting positions, the theoretical cutting force (Ftx, Fty, Ftz) of the cutting coordinate values is calculated as 2 The value of the cutting force at one cutting position is calculated by interpolation by interpolation. Also, the cumulative removal volume at the cutting coordinate value is calculated by the removal volume calculation unit 46 by interpolating the value of the cumulative removal volume at the two cutting positions by interpolation. Since the cutting position / machining condition data is represented by X, Y, Z axis coordinate values on the CAM, the X, Y, Z coordinate system based on, for example, a machine tool table similar to the cutting coordinate values. The above calculation is performed after conversion to the value of.

In step S106, when the work material 4 is cut from the initial weight m1 to the cutting position at the cutting coordinate value, the weight m3 of the work material 4 at that time is
(Equation 4)
m3 = m1− (cumulative removal volume at cutting coordinate value) × (specific gravity of work material)
And corrected. Therefore, the inertial force due to the weight of the circular table 100 and the work material 4 is corrected.

In step S107, the cutting force conversion unit 43 uses the cutting force (fx, fy, fz) calculated by the output of the force sensor 2 as the inertia force generated by the acceleration (ax, ay, az) at the cutting coordinate value. The cutting force (Fmx, Fmy, Fmz) at the cutting coordinate value is calculated as follows:
(Equation 5)
Fmx = fx− (m3 + m2) × ax
Fmy = fy− (m3 + m2) × ay
Fmz = fz− (m3 + m2) × az
Subsequently, in step S108, the cutting force comparison unit 45 calculates the theoretical cutting force of the cutting coordinate value based on the cutting force (Fmx, Fmy, Fmz) calculated from the measurement and the cutting force calculated in advance from the cutting theory. Compare (Ftx, Fty, Ftz). Here, the cutting force threshold value registered in advance in the abnormality detection threshold value storage unit 55 is read out with respect to the magnitude of the difference in cutting force to be compared, and the abnormality determination unit 47 performs comparison determination. Detect cutting abnormalities.
In step S109, the abnormality determination result is output to the output unit 62. Here, the abnormality determination unit 47 can also transmit an emergency stop instruction to the machine tool 10 or the NC control device 17 via the communication unit 63 according to the state of the cutting abnormality.

The cutting force abnormality determination process described above can be executed at an arbitrary point in time during the cutting process. For example, it is conceivable that the program is executed at predetermined time intervals.
Alternatively, the cutting position / processing condition storage unit 54 stores information on discrete cutting positions on the tool path calculated in advance in the three-dimensional CAM 81, but the cutting position where cutting coordinate values are stored during processing. If the measured value is acquired from the force sensor and the acceleration sensor and the above calculation is executed when the value reaches the value, it is not necessary to execute the interpolation calculation by the interpolation method in step S105, and the calculation accuracy is also improved. However, it is limited to the cutting position calculated in advance.

  FIG. 12 shows a connection configuration diagram of the machining device (machine tool) 10, the machining control PC (cutting force detection device) 30, and the NC control device 17 in the third embodiment of the present invention. The NC control device 17 controls the processing device 10 and is connected to the processing machine by machine wiring. The NC control device 17 and the machining control PC 30 are connected by an optical cable or a LAN cable 90 (not shown), and control signals can be input and output to the NC control device 17. For example, the coordinate values of the X, Y, Z, A, and C axes output to the NC controller 17 can be referred to by the machining control PC 30.

FIG. 13 shows a connected device configuration of the cutting force detection / abnormality detection system mounted on the machining control PC 30. The machining control PC 30 includes a keyboard and screen touch input device 61, a display device 62 such as an LCD display that allows an operator who is the user to recognize the output result, and communication for input / output of control signals with the NC control device 17. It has an I / F device 63, a computing device 40 composed of a CPU, a memory, etc., and a storage device 50 for storing programs 56 and data 57.
In the present embodiment, the cutting force detection / abnormality detection system implemented on the general-purpose computer as the machining control PC 30 may be implemented on the NC control device 17.

  14 to 20, details of items input by the operator who is the user of the cutting force detection / abnormality detection system of the present embodiment on the machining control PC 30 and items displayed on the operator by the screen display device 62 are shown. Details will be described.

  FIG. 14 is a schematic diagram illustrating an example of an input screen 200 for items to be input to the machining control PC before machining is started. The operator designates an NC program to be used for machining from the machining NC file field 201, downloads it from the three-dimensional CAM 81 by pressing a read button, and stores it in the program area 56. Further, the tool information to be used is designated from the tool registration file column 202, downloaded from the three-dimensional CAM 81, and stored in the data area 57. Further, a cutting force in machining theory at a cutting position of discrete points arranged at a predetermined interval or a predetermined rule on the machining tool path of the NC program, and a cumulative removal volume from the machining start position to each cutting position are preliminarily three-dimensional. The creation is instructed to the CAM 81, the read button in the cutting theory / cutting state calculation information file field 203 associated with the cutting position is pressed, and the CAM 81 is downloaded from the three-dimensional CAM 81 and stored in the data area 57. Furthermore, the file to be stored can be registered in an arbitrary storage device by pressing a read button.

  FIG. 15 is a schematic diagram illustrating an example of a work information input screen 230. The workpiece material 231, the initial weight 232, and the jig weight 233 for fixing the workpiece to the processing apparatus 10 are input from each input column. The material of the workpiece can be selected from pre-registered material types. By storing the work initial weight and the jig weight in the storage device 50, in the processing flow of FIG. 9, it is used for calculating the inertia force based on the change in the work weight and the acceleration sensor value as the machining progresses. By saving the input information shown in FIGS. 14 and 15 in the storage device 57, the machining abnormality determination process based on the flow shown in FIG. 11 can be started.

  The cutting force detection / abnormality detection system of the present embodiment includes the acquisition state (S101) of the force sensor binary value and the acceleration sensor trivalue during machining in each step of the machining abnormality determination process shown in the flowchart of FIG. Information about the calculated value (S102), the calculated acceleration value (S103), the change value of the work material weight (S106), the graph display of the abnormality determination (S108), and the abnormality determination result (S109). A monitor mode for displaying on the display device 62 according to the instruction input is provided. Hereinafter, examples of output screen display will be described.

FIG. 16A shows an example in which the cutting force waveform stored in the storage device 50 is output to the display device 62 as the cutting force output screen 204 during the machining. On the cutting force output screen 204, the cutting force waveforms in the X, Y, and Z directions indicated by the cutting force waveform 206 are output to the display device 62. On the cutting force display screen 204, a button 205 for outputting a cutting force waveform in a short time is arranged, and when the user presses the button 205, a force sensor binary value of about 60 ms from the pressing is recorded. Then, the cutting force is calculated and the cutting force display screen 206 is displayed.
In addition, by selecting / pressing a button 208 at the bottom of the cutting force display screen 204 in FIG. 16B, an average cutting force display screen 207 having a time interval of about 60 seconds longer than that at the time of pressing can be output. it can.

  FIG. 17 shows an example in which the acceleration is calculated from the information of the three values of the acceleration sensor stored in the storage device 50 during the processing and is output to the display device 62 as the acceleration output screen 209. When the operator selects / presses the lower screen acceleration button 210 on the acceleration output screen 209, an acceleration sensor value of about 60 s elapsed from the time of pressing is recorded, the acceleration is calculated, and the change in acceleration is displayed on the screen 209. An acceleration waveform 211 is shown.

  FIG. 18 shows an example in which information on the weight of the workpiece being processed is output to the display device 62 as the workpiece weight output screen 212. By selecting / depressing the weight button 213 at the bottom of the work weight output screen 212, the work weight during the lapse of about 60 seconds from the time of the depression is calculated and recorded in the storage device 50, and the work weight change 214 is recorded. Show. From the relationship between the acceleration waveform 211 in FIG. 17 and the workpiece weight change in FIG. 18, the change in workpiece weight shown in S106 in FIG. 11 is calculated to calculate the inertial force.

  FIG. 19 shows an example in which the vibration component of the cutting force obtained by Fourier-transforming the cutting force stored in the storage device 57 during processing into a relationship between frequency and amplitude is output as an output screen 215. In this output screen 215, when the operator selects and presses the cutting force vibration button 216 at the bottom of the screen, the cutting force is Fourier-transformed into the relationship between frequency and amplitude from the recorded information of the force sensor value and acceleration sensor value at the time of pressing. The vibration component of the cutting force is output to the cutting force vibration screen 217. On the cutting force vibration screen, a cutting component corresponding to the cutting frequency and a tool vibration component corresponding to the tool resonance frequency component are output as the cutting force amplitude.

  FIG. 20 shows an example in which information when detecting chatter vibration during machining is output to the display screen 62. By selecting / depressing the chatter index button 219 arranged on the lower side of the screen 218, for example, the chatter vibration state is displayed in the chatter index graph during the predetermined time elapsed since the press. 220 can be output. Here, the chatter index is a value obtained by dividing the cutting force vibration amplitude component 241 by the vibration amplitude component 242 of the tool on the cutting force vibration display screen 217 of FIG. The chatter vibration state display 220 shows a change in the machining time and the abnormality determination value of the cutting force calculated in S108 of FIG. In the chatter vibration state display 220, the upper limit of the chatter index value calculated from a theoretical cutting force calculated in advance as shown in the data table of FIG. When the change value of the value calculated from the cutting force calculated from the value and the acceleration sensor value exceeds the threshold value, an abnormality is output to the display device 62 as an abnormality. By causing the operator to recognize the above screen output, it is possible to detect the occurrence of abnormality during processing. As a result, the operator can suppress chatter by taking measures such as changing the feed of the processing device (machine tool) 10, the rotation speed of the main shaft 13, and the cutting depth. In addition, tool wear, chipping, etc. can be detected.

  Next, FIGS. 21 to 25 will explain means relating to calculation / control of machining conditions for avoiding an abnormality before it occurs as a detailed configuration example related to the abnormality detection / determination. Using the machining condition control method of the present invention, machining conditions such as cutting force are dynamically controlled while the machining apparatus (machine tool) 10 is in operation.

  In the machine tool 10, the machining conditions can be dynamically controlled by multiplying the initially set machining conditions (reflected in the NC program) by an override amount. Parameters for multiplying the override amount generally include the rotational speed of the spindle 13 and the feed speed of the tool 14, and the override amount can be changed in the range of 0 to 200%. Hereinafter, a configuration example in which the machining condition is changed (controlled) by changing the override amount will be described. However, the present invention is not limited to this, and a method of directly changing the machining condition is also applicable.

  FIGS. 21A and 21B show how to set the override amount change rate. A conversion graph of an override amount change rate (α) applied from the chatter index (threshold value c1) is shown. The chatter index (threshold value c1) is one of the parameters for evaluating the occurrence of chatter vibration. The measured strength value of the cutting force component is obtained by FFT (Fast Fourier Transform) to obtain the amplitude intensity for each frequency, and the cutting frequency component 241. And a value obtained by taking an amplitude ratio between the vibration vibration frequency component 242 near the resonance point of the tool 14. As this ratio is larger, chatter vibration is more likely to occur.

  In FIGS. 21A and 21B, the threshold for determination corresponding to the chatter index is c1. When the chatter index value exceeds c1, it is determined that chatter vibration has occurred, and according to the value, the override amount change rate (α) is obtained according to the conversion graph shown in the figure, and the override amount is changed (the α value is changed). Multiply). The override amount change rate (α) when the chatter index reaches the threshold value c1 is set to 100%. That is, a new override amount is obtained by multiplying the current override amount by the α value. Further, the machining condition is updated by multiplying the calculated new override amount by the initial setting value of the machining condition.

  For example, FIG. 21A shows an example in which the override amount change rate (α) is changed stepwise. As the chatter index value greatly exceeds the judgment threshold value c1 (c5, c6, c7, etc.), the amount of decrease from 100% of the override amount change rate (α) is increased (p3, p2, p1, etc.) and exceeded. When the size is small, the 100% -α value is taken small. Thereby, chatter vibration can be quickly converged (to a normal state before occurrence).

  Further, when the chatter index value is smaller than the threshold value c2, an override amount change rate (α) that is more positive than 100% is set, and control is performed to further increase the machining efficiency. At this time, chattering of the control can be prevented by setting α = 100% between the chatter index values c1 and c2. The override amount change rate (α) that is more positive than 100% is set to take a positive value that is larger than 100% as the chatter index value is significantly lower than c2, and a small positive value that is close to c2.

  In addition to the example of FIG. 21A, for example, a straight line or a curved line can be used as shown in FIG. In particular, in the case of a curve such as A, the override amount change rate (α) is smaller than 100% when the chatter index value is close to c1 or c2, and the effect of preventing chattering of the control is further reduced. is there.

FIG. 22 shows a stability limit diagram under general cutting conditions. A method for setting the step width (ST) of the override amount change rate (α) in FIG.
In FIG. 22, the region below the stability limit line indicated by A indicates a stable condition (stable region) in which chatter vibration does not occur, and the region above the stability limit line indicates that unstable vibration occurs due to chatter vibration. The unstable condition (unstable region) is as follows. The horizontal axis is the number of rotations of the tool (min ⁻¹ ) (the number of rotations of the tool 14 around the axis 14a), and the vertical axis is the amount of cutting of the axis (k) (the amount of cutting of the tool 14 (axis 14a) into the work material 4 ). PW is the period width. The stability limit line of A takes a peak value periodically as shown in the figure, and its peak position (p) is expressed by the following equation:
(Equation 6) p = 60 · f ₀ / (N · n)
It is represented by Here, f ₀ is the natural frequency of the tool 14, N is the number of chips. n takes an integer of 1 or more.

  As one method of increasing the machining efficiency, a method of increasing the amount of removal per unit time by increasing the shaft cutting amount (k) is effective. In order to increase the shaft cut amount (k) without generating chatter vibration, it is effective to use the machining conditions at the peak position within the stability region of the stability limit line of A. For example, point f. Therefore, when the initial machining conditions are derived, the initial machining conditions can be derived by calculating the value of the peak position (p) as shown in FIG. 22 using the above-described simulation or the like.

  However, because the error is included in the stability limit line of A due to errors in the material properties and shape dimensions of the tool 14 and the work material 4, the derived condition is not necessarily optimal. Therefore, the machining condition is guided to the peak position of the stability limit line (A) using the method shown in FIG. For example, the point f is brought close to the upper peak position. At this time, for example, the step width ST of the override amount change rate (α) in FIG. 21A is preferably about a fraction (for example, 1/5 or less) of the width PW in FIG.

  FIG. 23 shows a method for determining (setting) the upper limit (upper limit value) of the override amount so that the override amount where the chatter vibration has occurred is not used again when chatter vibration has occurred. FIG. 23 shows an example of a change in the override amount (V) when the override amount change rate (α) is determined using FIG. Cutting was started under the initial machining conditions, and it was determined that chatter vibration did not occur from time 0 to T3. Therefore, the override amount change rate (α) was more positive than 100%, and the override amount (V) increased. I will do it. When the override amount (V) increases, chatter vibration is likely to occur. When the chatter index value exceeds the determination threshold (c1 in FIG. 21) (time T3), it is determined that chatter vibration has occurred. The The v3 that is the override amount (V) at this time is stored. When it is determined that chatter vibration has occurred, the override amount (V) is decreased in order to suppress chatter vibration. If chatter vibration has not recurred after a certain period of time, the override amount (V) is increased, but when the chatter vibration occurs (T3), a value smaller than the override amount v3 stored. (For example, 90% of v3) is set as the upper limit value. Thereby, stable machining can be realized by avoiding the use of the condition that once generated chatter vibration.

  In FIG. 23, it is assumed that chatter vibration is detected again at time T4 (override amount v4). Therefore, the override amount in which chatter vibration is detected is re-stored as v4 (update), and similarly, the override amount (V) is decreased so as to suppress chatter vibration. If chatter vibration does not recur after a certain period of time, the override amount (V) is increased again. For example, since the value of 90% of v4 (v5) is reached at time T5, the increase in the override amount is stopped.

  Next, FIG. 24 shows an algorithm for dynamically controlling the machining conditions described with reference to FIGS.

In step S301, an initial value is set. The initial value of the override amount (V) and the override amount change rate (here, δ) is set to 100, the upper limit value of the override amount (VC) is set to the maximum value (max) that the override amount can take, and the time An initial value t ₀ is set in the variable Tc.
In step S302, the process waits for an instruction to measure the chatter index. If the instruction is confirmed, the process proceeds to the next step S303.

In step S303, a chatter index value (here, H) is calculated.
In step S304, when the chatter index value H is equal to or greater than a predetermined determination threshold c1 (H ≧ c1), it is determined that chatter vibration has occurred. Then, the α = δ value is determined by the flow that branches the setting condition of the stepwise override amount change rate (α = δ) shown in FIG. 21A according to the magnitude of the chatter index value H. For example, δ = p4 when H <c5, δ = p3 when H <c6, δ = p2 when H <c7, and δ = p1 otherwise.

In step S305, after the override amount change rate (δ) is determined, the current override amount (V) is substituted into the override amount upper limit value (VC) to obtain a new upper limit value.
In step S306, the current time (t) is stored in Tc.
Next, in step S307, a new override amount (V) is calculated by multiplying the current override amount (V) by the override amount change rate (δ).
In step S308, the new override amount (V) is stored. The stored new override amount (V) is used to calculate new machining conditions.

  In step S309, the new machining condition is calculated by multiplying the current machining condition by the new override amount (V), and the machining condition of the machining apparatus (machine tool) 10 is changed. For example, as shown in FIG. 12, when the processing control PC 30 and the NC control device 17 are configured as separate devices, this processing calculates a new processing condition in the processing control PC 30 and transmits it via the communication cable 90. The calculated new machining conditions are transmitted to the NC control device 17 and used for controlling the machining device (machine tool) 10.

  In step S310, if the chatter index value H is less than c1 (H <c1), for example, if H> c2, δ = 100%. If H <c2, it is determined that chatter vibration has not occurred, and the difference (t−Tc) between the current time (t) and the stored Tc is equal to or greater than a predetermined value (here, T1). To determine. This is to determine the elapsed time from the time when chatter vibration last occurred, and to determine that chatter vibration has been suppressed when a time equal to or greater than a predetermined value T1 has elapsed.

  If it is determined in step S311 that the chatter vibration has been suppressed, the setting condition of the stepwise override amount change rate (α) shown in FIG. 21A is branched according to the magnitude of the chatter index value H. Confirm the value in the flow. For example, δ = p5 when H> c3, δ = p6 when H> c4, and δ = p7 otherwise.

  In step S312, it is determined whether or not the new override amount V = V * δ / 100 exceeds 90% of the override amount upper limit value (VC). If not, the process proceeds to step S307. 90% of the override amount upper limit value (VC) is substituted for the amount V (step S313), and the process proceeds to step S308.

  In step S314, if there is an instruction to end the processing condition update process, the process is ended. If there is no instruction to end, the process proceeds to step S302 again, and the above is repeated.

  FIG. 25 shows an algorithm for dynamically controlling the machining conditions described in FIG. 21 (b) and FIG. The step (S304, S311) for obtaining the override amount change rate (δ) in FIG. 24 is the function {f (H), g (H)} of the chatter index (H) in FIG.

In step S304, for example, when the chatter index value H is equal to or greater than c1, it is determined that chatter vibration has occurred, and the δ value is determined using the function f (H).
In step S311, if the chatter index value H is less than or equal to c2, it is determined that there is room for chatter vibration, and the δ value is determined using the function g (H). When the chatter index value H is smaller than c1 and equal to or larger than c2, δ = 100% is set to prevent chattering.

  The machining control PC 30 executes the processing (algorithm) as described above, issues a chatter index measurement instruction at a frequency of a predetermined time interval, for example, during machining, updates the new override amount V, and performs NC control. An operation of outputting an instruction to change the machining conditions to the apparatus 17 is conceivable. Further, it is appropriate to increase the execution frequency of this processing (algorithm) as necessary. By the processing of the present invention, it is possible to determine the occurrence of chatter vibration with a constant threshold regardless of the processing conditions, so that the threshold can be set appropriately, thereby improving the accuracy of abnormality detection. In addition, stable and highly efficient cutting can be realized under the machining conditions immediately before chatter vibration occurs.

  As described above, according to the present embodiment, the processing table 1 (workpiece fixing jig) on which the curved workpiece 4 is fixed by the 5-axis machine (machine tool 10) is rotated and inclined. Even in the state of cutting that moves, the cutting force (component) applied to the workpiece 4 and the tool 14 on the processed surface can be accurately measured (detected). As a result, abnormalities such as chatter vibration, excessive tool wear, and chipping during cutting in curved surface cutting can be detected before the occurrence, and the processing conditions can be suitably controlled. Therefore, it is possible to realize high efficiency of cutting and cost reduction of a processed product.

  The invention made by the present inventor has been specifically described based on the embodiment of the invention. However, the invention is not limited to the embodiment of the invention, and changes are made without departing from the scope of the invention. Of course, it is possible.

DESCRIPTION OF SYMBOLS 1 ... Work material fixing jig, 2 ... Force sensor, 3 ... Acceleration sensor, 4 ... Work material, 5 ... Tool path, 10 ... Machine tool, 11 ... -Frame, 12 ... spindle table, 13 ... spindle, 14 ... cutting tool, 14a ... central axis of cutting tool,
15 ... Processing area, 16 ... Table, 17 ... NC control device,
20 ... Force sensor amplifier unit, 21 ... Acceleration sensor amplifier, 30 ... Machining control PC,
40 ... calculation unit, 41 ... force sensor measurement unit, 42 ... acceleration measurement unit,
43 ... cutting force conversion unit, 44 ... cutting coordinate value acquisition unit, 45 ... cutting force comparison unit,
46 ... removal volume calculation unit, 47 ... abnormality determination unit, 50 ... storage unit,
51 ... Work material / table weight storage unit, 52 ... Cutting force / acceleration measurement value storage unit,
53 ... cutting coordinate value storage unit, 54 ... cutting position / processing condition storage unit,
55... Abnormality detection threshold value storage unit, 56... Program, 57.
61 ... Input unit, 62 ... Output unit, 63 ... Communication unit, 80 ... 3D CAD,
81 ... 3D CAM, 90 ... network, 100 ... circular table,
101 ... trunnion table, 107 ... cutting position / processing condition storage unit,
108 ... cutting force calculation value storage unit, 109 ... cutting force threshold value storage unit,
110: Material CAD data, 111: Processing area, 112: Cutting tool,
113 ... Tool path, 114, 115, 117, 118 ... Cutting position,
116... Corner point (or turning point) where there is a change in the course on the tool path
200... Input screen, 201... NC file used for machining, 202... Tool information file, 203... Cutting force / machining state calculation information file, 204. .. Button for outputting a cutting force waveform in a short time on the screen, 206... Cutting force waveform, 207... Average cutting force display screen, 208... Average cutting force display button, 209 ... acceleration output screen, 210 ... acceleration waveform display button, 211 ... acceleration waveform, 212 ... work weight output screen, 213 ... weight change display button,
214 ... Change in workpiece weight, 215 ... Cutting force vibration component output screen, 216 ... Cutting force vibration display button, 217 ... Cutting force vibration screen, 218 ... Chatter vibration display screen during machining 219 ... Chatter index button, 220 ... Chatter vibration status display,
230 ... Work information input screen, 231 ... Work material, 232 ... Work initial weight, 233 ... Jig weight, 241 ... Cutting force vibration amplitude component, 242 ... Tool Vibration amplitude component.

Claims (14)

An apparatus for detecting a cutting force during machining of a machine tool,
A calculation unit, a storage unit, an input unit, an output unit, and a communication unit;
The storage unit stores the work material input from the input unit, and the weight of the processing table,
The computing unit is
A force that receives the output of the force sensor incorporated in the support part of the machining table of the machine tool via the communication part or the input part, and measures the cutting force applied between the tool being cut and the work material A sensor measurement unit;
An acceleration measuring unit that receives an output of an acceleration sensor attached to a processing table of a machine tool via the communication unit or the input unit, and measures an acceleration when the processing table is moving during cutting; and
A cutting force conversion unit that calculates the inertial force from the measured acceleration and the weight of the work table and the work material, and corrects the cutting force measured by the force sensor with the inertial force to obtain the corrected cutting force. And
The output unit outputs the corrected cutting force, the cutting force detection device. The storage unit further preliminarily stores a CAM cutting force at a cutting position of discrete points arranged at a predetermined interval or a predetermined rule on the processing tool path, and a cumulative removal volume from the processing start position to each cutting position in advance. Enter and store the information calculated in
The computing unit is
A cutting coordinate value acquisition unit for acquiring a cutting coordinate value from the machine tool or the NC control device in synchronization with the measurement of the force sensor and the acceleration sensor;
The cutting force conversion unit calculates a cumulative removal volume at a cutting position on a processing tool path corresponding to the cutting coordinate value from information on a corresponding cutting position stored in the storage unit, and The weight is corrected, an inertial force is calculated based on the corrected weight of the work material, and the cutting force measured by the force sensor is corrected by the inertial force to obtain a corrected cutting force. Item 2. The cutting force detection device according to Item 1. The storage unit further stores in advance a threshold value for determining abnormality during cutting from a difference between a cutting force in theoretical calculation and a cutting force obtained from a measured value,
The computing unit is
The theoretical cutting force at the cutting position on the machining tool path corresponding to the cutting coordinate value is calculated from the cutting force information at the corresponding cutting position stored in the storage unit, and the correction obtained from the measurement value Cutting force comparison part to compare with the subsequent cutting force,
The difference value between the cutting force obtained from the measured value calculated by the cutting force comparison unit and the theoretical cutting force is stored in the storage unit, and the threshold value for determining an abnormality during cutting. The cutting force detection device according to claim 2, further comprising: an abnormality determination unit that detects cutting abnormality as compared with the above. The output unit displays an input screen for program information registration,
The calculation unit instructs the 3D CAM to create and download the corresponding file via the communication unit in response to the operator inputting an instruction to read each file through the input unit. The cutting force detection apparatus according to claim 1, wherein a file download is received and stored in the storage unit. Through the input unit, an instruction to display a cutting force waveform is received from an operator during machining,
The calculation unit records a force sensor value at a predetermined time interval from when the operator presses a button, and outputs a cutting force waveform at a predetermined time interval or an average cutting force display to the output unit. The cutting force detection apparatus according to claim 1. Through the input unit, an instruction to display an acceleration waveform is received from an operator during machining,
2. The cutting force detection according to claim 1, wherein the calculation unit records an acceleration sensor value at a predetermined time interval from when the operator presses a button, and outputs an acceleration waveform at a predetermined time interval to the output unit. apparatus. Through the input unit, receiving an instruction to display a change in workpiece weight from the operator during machining,
The calculation unit calculates the cumulative removal volume on the machining tool path from the cutting coordinate value when the operator presses the button from the information of the corresponding cutting position stored in the storage unit, and calculates the weight change at a predetermined time interval. The cutting force detection apparatus according to claim 2, wherein the graph is output to the output unit. Through the input unit, an instruction to display the cutting force vibration is received from the operator during machining,
The calculation unit calculates the vibration component of the cutting force, the vibration component of the cutting force obtained by Fourier transforming the cutting force into the relationship between the frequency and the amplitude based on the recorded information of the force sensor value and the acceleration sensor value when the operator presses the button, and the cutting force amplitude. The cutting force detection device according to claim 1, wherein the output is output to the output unit in a graph representation of / frequency. Via the input unit, an instruction to display a chatter vibration state is received from the operator during machining,
2. The cutting force according to claim 1, wherein the calculation unit outputs a chatter vibration occurrence state during a predetermined time from when the operator presses the button to the output unit in a chatter index graph. Detection device. A method for detecting a cutting force during machining of a machine tool,
In advance, the input work material and the weight of the processing table are received and stored in the storage device,
Receives the output of the force sensor built in the support part of the machining table of the machine tool, measures the cutting force applied between the tool being cut and the work material,
Accept the output of the acceleration sensor attached to the machining table of the machine tool, measure the acceleration when moving the machining table during cutting,
The inertial force is calculated from the measured acceleration and the weight of the machining table and the work material, the cutting force measured by the force sensor is corrected by the inertial force, and the corrected cutting force is output. Cutting force detection method. Further, the storage device further stores in advance the cutting force in the machining theory at the cutting positions of discrete points arranged at predetermined intervals or predetermined rules on the machining tool path, and the cumulative removal volume from the machining start position to each cutting position in advance. Enter and store the information calculated in
In synchronization with the measurement of the force sensor and the acceleration sensor, a cutting coordinate value is obtained from a machine tool or an NC control device,
The cumulative removal volume at the cutting position on the machining tool path corresponding to the cutting coordinate value is calculated from the information on the corresponding cutting position stored in the storage device, and the weight of the work material is corrected and corrected. The cutting force detection method according to claim 10, wherein an inertial force is calculated based on a weight of a work material, and a cutting force measured by the force sensor is corrected by the inertial force. The storage device further stores in advance a threshold value for determining an abnormality during cutting from the difference between the cutting force in theoretical calculation and the cutting force obtained from the measured value,
The theoretical cutting force at the cutting position on the machining tool path corresponding to the cutting coordinate value is calculated from the cutting force information at the corresponding cutting position stored in the storage device, and the correction obtained from the measurement value Compared with the cutting force after,
By calculating a difference value between the cutting force obtained from the measured value and the theoretical cutting force, and comparing with the threshold value for determining abnormality during cutting stored in the storage unit, The cutting force detection method according to claim 11, wherein a cutting abnormality is detected. A method for detecting a machining abnormality of a machine tool,
In the storage device, the weight of the work material and the work table, the cutting force in the machining theory at the cutting position on the machining tool path, the accumulated removal volume information from the machining start position to each cutting position, and abnormalities during cutting are stored. Memorize the threshold for judgment,
The cutting force applied between the tool being cut and the work material is measured from the output of the force sensor incorporated in the support part of the processing table of the machine tool.
From the output of the acceleration sensor attached to the machining table of the machine tool, measure the acceleration when moving the machining table during cutting,
In synchronization with the measurement of the force sensor and the acceleration sensor, a cutting coordinate value is obtained from a machine tool or an NC control device,
The cumulative removal volume at the cutting position on the machining tool path corresponding to the cutting coordinate value is calculated to correct the weight of the work material, and the inertial force is calculated based on the corrected work material weight and the acceleration. ,
The cutting force measured by the force sensor is corrected by the inertial force,
The theoretical cutting force at the cutting position on the machining tool path corresponding to the cutting coordinate value is calculated from the cutting force information at the corresponding cutting position stored in the storage device, and the correction obtained from the measurement value Compared with the cutting force after,
A difference between the cutting force obtained from the measured value and a theoretical cutting force is calculated, and compared with the threshold value stored in the storage unit, a cutting abnormality is detected. Machining abnormality detection method. A system that converges the machining conditions during machining of the machine tool to the machining conditions at the peak position within the stability region of the stability limit line,
A calculation unit, a storage unit, an input unit, an output unit, and a communication unit;
The storage unit stores a conversion table of an override amount change rate and a chatter index of processing conditions input from the input unit or the communication unit, initial values of various variables, and threshold values,
The arithmetic unit Fourier-transforms the cutting force calculated from the output value of the force sensor and acceleration sensor incorporated in the machining table of the machine tool into a relationship between frequency and amplitude, and a cutting force vibration amplitude component and a tool vibration amplitude component Means for calculating a chatter index represented by the ratio of
Means for searching the stored conversion table according to the calculated chatter index, performing a conversion operation, and obtaining a corresponding override amount change rate;
A means for updating the override amount to a newer override amount than the current override amount according to the obtained override amount change rate and the override amount upper limit value in which chatter vibration has occurred in the past;
Means for changing a target machining condition according to the new override amount;
A machining condition control system comprising: means for outputting the changed machining condition to an NC control device via the communication unit.

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