Method and device for estimating machining time of machine tool, and machine tool

Abstract

This method for estimating a machining time when a machining program is executed by a machine tool comprises: setting first and second threshold values for a machining load; acquiring from moment to moment a machining load when a workpiece (W) is machined according to a predetermined machining program; obtaining a total machining time required for machining the workpiece; setting an acceleration override value in a machining load range in which the machining load is lower than a first threshold value (TH1); setting a deceleration override value in a machining load range in which the machining load is higher than a second threshold value (TH2); and calculating a corrected total machining time when a feed speed specified in the machining program is adaptively controlled, according to the acceleration override value and the deceleration override value.

Description

Method, apparatus, and machine tool for estimating machining time of a machine tool

[0001] The present invention relates to a method and an apparatus for estimating the machining time of a machine tool capable of feed rate adaptive control, and a machine tool capable of estimating the machining time when feed rate adaptive control is implemented.

[0002] Patent Document 1 describes an adaptive control method in which when the ultrasonic acoustic signal value is between the standard low level and the lower limit level, the override gradually decreases and approaches 100% as the ultrasonic acoustic signal increases from the lower limit level to the standard low level, and when the ultrasonic acoustic signal value is between the upper limit level and the standard high level, the override gradually increases and approaches 100% as the acoustic signal decreases from the upper limit level to the standard high level, so as to correspond the ultrasonic acoustic signal and the override.

[0003] Patent Document 2 also describes a technique for predicting in advance the machining time when the feed rate of the spindle is adaptively controlled so that the load applied to the spindle becomes constant.

[0004] Japanese Patent Publication No. 3-060621 International Publication No. 2022 / 186135

[0005] In the adaptive control method described in Patent Document 1, the operator cannot recognize how much the machining time actually changes, and thus there is a problem that it is impossible to determine whether the adaptive control is appropriate or not.

[0006] In the prediction technique described in Patent Document 2, when adaptive control is performed, the machining time becomes long, and there is a problem that it cannot meet the recent demand for shortening the machining time in the field of machine tools.

[0007] Conventional feed rate adaptive control is generally used to prevent overload by applying a deceleration override to reduce the feed rate when the set load is exceeded. In this case, the set load value (second threshold) can be empirically adopted by using the load value at which chatter vibration occurs or the machining sound changes abnormally, making the setting easy. In contrast, feed rate adaptive control also functions to increase productivity by applying a speed increase override to increase the feed rate when the load falls below a set value (first threshold). However, the criteria for setting this first threshold are ambiguous, and setting it to a high value can lead to problems such as excessive feed rate, accelerated tool wear, and an increased risk of chipping. Therefore, it is currently set to a safe low value, and in practice, the speed increase override is hardly applied. The present invention aims to solve these problems of the conventional technology and to provide a method, apparatus, and machine tool capable of estimating machining time that support the easy setting of the first and second thresholds of machining load to avoid excessive machining load conditions while suppressing an increase in machining time.

[0008] To achieve the above objectives, the present invention provides a method for estimating machining time when executing a machining program on a machine tool capable of feed rate adaptive control, comprising the steps of: setting a first threshold for machining load and a second threshold greater than the first threshold; acquiring the machining load moment by moment when actually machining a workpiece according to a predetermined machining program or when performing a machining simulation; storing the acquired machining load in association with time; determining the total machining time required to machine the workpiece based on the stored machining load and time; setting a speed-increasing override value greater than 100% for use in a machining load range where the machining load is smaller than the first threshold; setting a deceleration override value less than 100% for use in a machining load range where the machining load is larger than the second threshold; and calculating the corrected total machining time when the feed rate specified in the machining program is adaptively controlled according to the speed-increasing override value and the deceleration override value.

[0009] Furthermore, according to the present invention, a device for estimating the machining time when executing a machining program on a machine tool, which is capable of adaptive feed rate control, is provided, comprising: a parameter storage unit that stores a first threshold for machining load, a second threshold greater than the first threshold, a maximum value of a speed-increasing override exceeding 100% applied in a machining load range where the machining load is less than the first threshold, and a minimum value of a deceleration override less than 100% applied in a machining load range where the machining spindle load is greater than the second threshold; a machining load acquisition unit that acquires the machining load moment by moment when a workpiece is actually machined or when a machining simulation is performed according to the machining program; a machining load storage unit that stores the acquired machining load in association with time; and a machining time calculation unit that calculates the total machining time required to machine a workpiece based on the stored machining load and time, and the corrected total machining time when the feed rate specified in the machining program is adaptively controlled according to the maximum value of the speed-increasing override and the minimum value of the deceleration override.

[0010] Furthermore, according to the present invention, a machine tool that can perform feed rate adaptive control and processes a workpiece according to a processing program includes a parameter storage unit that stores a first threshold for processing load, a second threshold greater than the first threshold, a maximum value of a speed-increasing override exceeding 100% that is applied in a processing load range where the processing load is less than the first threshold, and a minimum value of a deceleration override less than 100% that is applied in a processing load range where the processing load is greater than the second threshold, a processing load acquisition unit that acquires the processing load when processing a workpiece according to the processing program moment by moment, and the acquired processing load A machine tool is provided that includes a machining load storage unit that stores machining loads associated with time, a machining time calculation unit that calculates the total machining time required to machine a workpiece based on the stored machining loads and time, and a corrected total machining time when the feed rate specified in the machining program is adaptively controlled according to the maximum value of the speed-increasing override and the minimum value of the speed-deceleration override, and a display device that displays the total machining time when a workpiece is machined according to the machining program and the corrected total machining time, wherein the first threshold and the second threshold are determined such that the corrected total machining time is shorter than the total machining time.

[0011] According to the present invention, the operator can compare the total machining time when machining is performed without adaptive control or when machining is simulated with the corrected total machining time assuming adaptive control is performed, and based on the results, can easily set appropriate first and second thresholds to avoid excessive machining load while shortening the machining time. Thus, according to the present invention, it is possible not only to make adjustments to avoid excessive machining load on the spindle, but also to easily perform adaptive control of the feed rate to actively shorten the machining time in light-load cutting, and ultimately, productivity can be improved by shortening the machining time.

[0012] This is a block diagram showing an example of the machining time estimation device of the present invention. This is a schematic front view showing an example of an operation panel. This is a graph showing an example of the temporal change in spindle load. This is a schematic diagram showing an example of a feed rate adjustment window displayed on the display panel of the operation panel.

[0013] Hereinafter, preferred embodiments of the present invention will be described with reference to the attached drawings. Referring to Figure 1, an example of a machining time estimation device 10 and an NC machine tool 100 is shown.

[0014] As an example, the NC machine tool 100 includes a bed 102 as a base fixed to the factory floor, a column 104 mounted on the upper surface of the bed 102 at the rear end (right side in Figure 1) so as to be able to reciprocate in the left-right direction or in the X-axis direction (direction perpendicular to the plane of the paper in Figure 1), a Y-slider 110 mounted on the front of the column 104 so as to be able to move in the up-down direction or in the Y-axis direction, a spindle head 114 mounted on the Y-slider 110, and a table 106 mounted on the upper surface of the front part (left side in Figure 1) of the bed 102 so as to be able to move in the front-back direction or in the Z-axis direction (left-right direction in Figure 1).

[0015] The spindle 112 is rotatably supported by the spindle head 114 around a horizontal rotation axis O extending in the Z-axis direction. The spindle head 114 is equipped with a spindle motor 116 that rotationally drives the spindle 112. Preferably, the spindle motor 116 is formed by a built-in motor disposed within the housing (not shown) of the spindle head 114. The spindle motor 116 may be equipped with a rotary encoder (not shown). The current value of the spindle motor 116 is detected by a current sensor 126 and converted into a load (torque) acting on the spindle 112 as a machining load. The machining load is not limited to the spindle load in this embodiment, but may also be the feed axis load determined by detecting the current values ​​of the X-axis motor 118, Y-axis motor 120, and Z-axis motor 122, or it may be determined by a load cell attached to the workpiece holder 106a, or it may be determined from the material removal rate (MRR), which is the product of the cutting area of ​​the workpiece W by the tool 124 and the feed rate. In this embodiment, the spindle load will be used as a representative example of the machining load.

[0016] A tool 124 for machining a workpiece W fixed to a table 106 is mounted at the tip of the spindle 112. The workpiece W is fixed to the upper surface of the table 106. In the example shown in Figure 1, the workpiece W is fixed to the table 106 via a workpiece mounting fixture 106a, such as an angle bracket.

[0017] The NC machine tool 100 also includes a control panel 50 for an operator to operate the NC machine tool 100. The control panel 50 can be mounted on the wall of a cover (not shown) that surrounds the NC machine tool 100. Referring to Figure 2, an example control panel 50 includes a rectangular prism-shaped housing 52 housing electrical components such as an electronic circuit board, wiring, and connectors; a display panel 54 mounted on the front of the housing 52; a keyboard 56 for inputting necessary information to the NC device 30 of the NC machine tool 100 and editing NC programs; an emergency stop button 58; a button assembly 60 containing multiple buttons for operating various functions of the NC machine tool 100; and rotary knobs 62, 64, and 66 for override adjustment. The display panel 54 displays various operating statuses and machining conditions of the NC machine tool 100. The display panel 54 can be formed as a touch panel that allows the operator to select or input corresponding to the touched area by touching the screen with their finger or a stylus.

[0018] The NC machine tool 100 may further include peripheral equipment such as a tool magazine (not shown) for storing multiple tools used for machining, an automatic tool changer (not shown) for exchanging tools between the tool magazine and the spindle 112, and a coolant supply device (not shown) for supplying coolant to the machining area of ​​the NC machine tool 100, as well as a machine control device (not shown) for controlling the peripheral equipment. In this embodiment, the NC machine tool 100 is configured as a horizontal machining center, but the NC machine tool 100 may also be a vertical machining center that rotates the spindle around a vertical axis of rotation. Alternatively, it may be any other NC machine tool that performs turning, grinding, etc.

[0019] Column 104 is mounted to reciprocate along a pair of X-axis guide rails (not shown) extending in the X-axis direction on the upper front surface of table 106. Bed 102 is provided with an X-axis feed device that drives column 104 to reciprocate along the X-axis guide rails, which consists of a ball screw (not shown) extending in the X-axis direction and an X-axis motor 118 connected to one end of the ball screw. A nut (not shown) that engages with the ball screw is attached to column 104. Bed 102 is also mounted with an X-scale (not shown) for measuring the coordinate position of column 104 in the X-axis direction.

[0020] The Y-slider 110 is mounted on the front surface of the column 104 so as to be able to reciprocate along a pair of Y-axis guide rails extending in the Y-axis direction. The column 104 is equipped with a Y-axis feed device that drives the Y-slider 110 to reciprocate along the Y-axis guide rails, which includes a ball screw (not shown) extending in the Y-axis direction and a Y-axis motor 120 connected to one end of the ball screw. The Y-slider 110 is fitted with a nut (not shown) that engages with the ball screw. The column 104 is also fitted with a Y-scale (not shown) for measuring the coordinate position of the Y-slider 110 in the Y-axis direction.

[0021] Table 106 is mounted on the upper surface of bed 102 so as to be able to reciprocate along a pair of Z-axis guide rails (not shown) that extend horizontally in the Z-axis direction (left-right direction in Figure 1). Bed 102 is equipped with a Z-axis feed device that drives table 106 to reciprocate along the Z-axis guide rails, which consists of a ball screw (not shown) extending in the Z-axis direction and a Z-axis motor 122 connected to one end of the ball screw. A nut (not shown) that engages with the ball screw is attached to table 106. A Z-scale (not shown) for measuring the coordinate position of table 106 in the Z-axis direction is also attached to bed 102.

[0022] The X-axis motor 118, Y-axis motor 120, Z-axis motor 122, X-scale, Y-scale, Z-scale, spindle motor 116, and rotary encoder are connected to the NC device 30, and the X-axis motor 118, Y-axis motor 120, Z-axis motor 122, and spindle motor 116 are controlled according to a machining program input to the NC device 30 based on the measurements of the X-scale, Y-scale, Z-scale, and rotary encoder. In this way, the NC machine tool 100 rotates the spindle 112 while moving the tool 124 at the tip of the spindle 112 relative to the workpiece W on the table 106, according to the machining program supplied to the NC device 30, to machine the workpiece W.

[0023] The machining time estimation device 10 comprises a feed rate adaptive control unit 12, a parameter storage unit 14, a machining time calculation unit 16, an image generation unit 18, a spindle load storage unit 20, and a spindle load acquisition unit 22 as its main components. The feed rate adaptive control unit 12, parameter storage unit 14, machining time calculation unit 16, image generation unit 18, spindle load storage unit 20, and spindle load acquisition unit 22 can be composed of a computer and associated software including a CPU (Central Processing Unit), memory devices such as RAM (Random Access Memory) and ROM (Read-Only Memory), storage devices such as HDD (Hard Disk Drive) and SSD (Solid State Drive), an RTC (Real-Time Clock) consisting of an integrated circuit with a clock function, input / output ports, and a bidirectional bus that interconnects these. The machining time estimation device 10 can be formed by a personal computer, server, or tablet independent of the NC device 30 or machine control device of the NC machine tool 100. The machining time estimation device 10 may be configured as software as part of the NC device 30 or machine control device of the NC machine tool 100. The display device of the present invention can be formed by the display panel 54 of the control panel 50 or by the display (not shown) of a personal computer, server, or tablet.

[0024] The operation of this embodiment will now be explained. Referring to Figure 3, a time-series graph is shown illustrating an example of the change in the load (spindle load SL) acting on the spindle 112. In the graph in Figure 3, the vertical axis is the spindle load SL, and the horizontal axis is time (T). At time T0, power is supplied to the spindle 112 and the spindle 112 begins to rotate, and from time T1, the tool 124 engages with the workpiece W and machining begins.

[0025] During the time period T0 to T1, air cutting (dry cutting) is performed in which the spindle 112 and the tool 124 are fed relative to the workpiece W in the X, Y, and Z axis directions while the tool 124 is not engaged with the workpiece W. Air cutting occurs during the approach process from the cutting feed start position until the tool actually cuts into the workpiece W, when there are pockets in the reciprocating machining of the workpiece surface, or when there are variations in the material dimensions of the cast workpiece.

[0026] In this invention, air cut is determined by the magnitude of the spindle load SL. The threshold value TH0 of the spindle load SL used to determine air cut is called the air cut threshold. The feed rate adaptive control unit 12 determines that air cut is being performed when the spindle load SL is less than the air cut threshold TH0. For example, the air cut threshold TH0 can be input by the operator from the control panel 50 to the parameter storage unit 14 based on past performance, experience, and experiments.

[0027] In the graph in Figure 3, machining is performed with a relatively low spindle load SL (low-load machining) between times T1 and T2, machining is performed with an intermediate spindle load SL (intermediate-load machining) between times T2 and T3, low-load machining is performed between times T3 and T4, intermediate-load machining is performed between times T4 and T5, high-load machining is performed between times T5 and T6, intermediate-load machining is performed between times T6 and T7, low-load machining is performed between times T7 and T8, and air cut is performed between times T8 and T9.

[0028] In this invention, the first threshold TH1 is defined by the upper limit of low-load machining or the lower limit of intermediate-load machining, and the second threshold TH2 is defined by the upper limit of intermediate-load machining or the lower limit of high-load machining. The first and second thresholds TH1 and TH2 can, for example, be input by the operator from the control panel 50 to the parameter storage unit 14 based on past results, experience, and experiments. Alternatively, a limit threshold TH3 may be input to the parameter storage unit 14 as the maximum allowable value of the spindle load SL, and an alarm may be generated when the spindle load SL exceeds the limit threshold TH3.

[0029] Furthermore, the parameter storage unit 14 receives the maximum value OVR1 for speed increase override and the minimum value OVR2 for speed deceleration override. The maximum value OVR1 and minimum value OVR2 for speed increase override are percentages of the feed rate command value specified in the machining program input to the NC device 30, with 100% being the value. The maximum value OVR1 for speed increase override is a parameter that increases the feed rate, and a value greater than 100% is input. The minimum value OVR2 for speed deceleration override is a parameter that decreases the feed rate, and a value less than 100% is input. For example, the user can input the maximum value OVR1 and minimum value OVR2 for speed increase override from the control panel 50 to the parameter storage unit 14 based on past results, experience, and experiments. When the spindle load SL falls below the first threshold TH1, the feed rate adaptive control unit 12 applies a speed increase override to the feed rate. In this feed rate adaptive control, it is preferable that in a load range smaller than the first threshold TH1, the speed increase override value gradually increases as the spindle load SL decreases from the first threshold TH1, and plateaus at the maximum speed increase override value OVR1. Furthermore, in a load range larger than the second threshold TH2, it is preferable that the deceleration override value gradually decreases as the spindle load SL increases from the second threshold TH2, and plateaus at the minimum deceleration override value OVR2. The reason for setting the maximum speed increase override value OVR1 and the minimum deceleration override value OVR2 is to prevent the feed rate from increasing unnecessarily, which would accelerate tool wear or cause chipping, and also to prevent the feed rate from decreasing drastically, which would lengthen the machining time.

[0030] The spindle load acquisition unit 22 acquires the spindle load SL acting on the spindle motor 116 moment by moment based on the current value of the spindle motor 116 detected by the current sensor 126, and outputs the acquired spindle load SL to the spindle load storage unit 20. The spindle load storage unit 20 stores the spindle load SL received from the spindle load acquisition unit 22, associating it with the time it was received. Alternatively, the spindle load SL may be acquired by simulating machining using the machining simulator 200 without actually performing machining.

[0031] The machining time calculation unit 16 receives the moment-by moment spindle load SL and time T from the spindle load storage unit 20 after the workpiece W has actually been machined according to the machining program, and calculates the total machining time ΔT, which is the time required for machining. For example, in the example in Figure 3, ΔT = T9 - T0.

[0032] Next, the machining time calculation unit 16 divides the spindle load SL into an air-cut spindle load range L0 smaller than the air-cut threshold TH0, a low spindle load range L1 greater than or equal to the air-cut threshold TH0 and smaller than the first threshold TH1, an intermediate spindle load range L2 greater than or equal to the first threshold TH1 and less than or equal to the second threshold TH2, and a high spindle load range L3 greater than the second threshold TH2, and calculates the air-cut time ΔT0 in the air-cut spindle load range L0, and the machining times ΔT1, ΔT2, and ΔT3 in each of the spindle load ranges L1, L2, and L3.

[0033] For example, in the example in Figure 3, ΔT0 = (T1 - T0) + (T9 - T8) ΔT1 = (T2 - T1) + (T4 - T3) + (T8 - T7) ΔT2 = (T3 - T2) + (T5 - T4) + (T7 - T6) ΔT3 = (T6 - T5)

[0034] Furthermore, the operation of the machining time calculation unit 16 will be explained using Figure 4. Figure 4 shows the speed adjustment window 70 displayed on the display panel 54 of the control panel 50. First, the machining time calculation unit 16 converts Figure 3, which is an example of time-series data of the spindle load SL stored in the spindle load storage unit 20, into the histogram 8 shown in Figure 4. In the histogram 8, the horizontal axis shows each band of the spindle load SL, and the vertical axis shows the time T included in each band of the spindle load SL. For convenience, the spindle load SL is displayed as a percentage (%) of the rated current value of the spindle motor 116, and the time T is displayed in minutes (min). The actual values ​​in Figure 3 are shown by the length of the black bars in the histogram 8. Other related information is added through the image generation unit 18 to make it easier for the operator to see, and it becomes the speed adjustment window 70.

[0035] Figure 4 shows the histogram 8, and as related information, the histogram 8 shows machining time display fields 74 and 76, indicating that the actual machining time without adaptive control is 22 minutes and 29 seconds for tool number T200, and that the estimated machining time with adaptive control is reduced to 21 minutes and 34 seconds. Below that, a slider bar 78 and arrows 72a and 72b are shown, indicating the first threshold TH1 and second threshold TH2 of the spindle load SL. Below the histogram 8 are input boxes 84 and 86 for the upper limit of AC corresponding to the second threshold TH2 of the spindle load SL and the lower limit of AC corresponding to the first threshold TH1, and input boxes 88 and 90 for the maximum feed override corresponding to the maximum speed override OVR1 and the minimum feed override corresponding to the minimum speed override OVR2. Further below are a calculation button 94 and an execution button 92.

[0036] The operator enters the AC upper limit, AC lower limit, feed override maximum value, and feed override minimum value recommended by their organization (user) into input boxes 84, 86, 88, and 90, for example, 20.0, 8.0, 150, and 50, respectively. When the calculation button 94 is pressed, the arrows 72a and 72b on the slider bar 78, which indicates the AC range in which adaptive control is performed, move and are displayed at the corresponding positions on the horizontal axis scale of the histogram 8. Simultaneously, acceleration and deceleration calculations are performed according to the feed override value applied to each spindle load band, and the estimated machining time is displayed as hatching to the right of each bar. The estimated machining time can be calculated by multiplying the actual machining time by the reciprocal of the override value. The feed override value applied to each spindle load band at this time gradually increases as it decreases below the AC lower limit. For example, it is set to 110% in the band around 7.5% spindle load, 120% in the band around 6.7%, 130% in the band around 5.8%, and 140% in the band around 5.0%. It also gradually decreases as it increases above the AC upper limit. For example, it is set to 90% in the band around 20.8% spindle load, 80% in the band around 21.6%, 70% in the band around 22.5%, and 60% in the band around 23.5%. This feed override value is automatically assigned by prorating the interval from 100% to the minimum feed override value based on the number of spindle load bands that exceed the AC upper limit, and similarly, it is automatically assigned by prorating the interval from 100% to the maximum feed override value based on the number of spindle load bands that exceed the AC lower limit.

[0037] Histogram 8 in Figure 4 shows actual machining times, solidified in black, represented by the length of bars for each spindle load SL range. Furthermore, adaptive control of speed increase override is performed in the range of spindle load SL below the AC lower limit of 8.0% (coarse dot shading), and the estimated machining time at that time is represented by the height of the bar with speed increase hatching to the right of the black bar. Adaptive control of deceleration override is performed in the range of spindle load SL above the AC upper limit of 20.0% (fine dot shading), and the estimated machining time at that time is represented by the height of the bar with deceleration hatching to the right of the black bar. In the range between the AC lower limit of 8.0% and the AC upper limit of 20.0%, adaptive control is not performed, so only the actual black bars are displayed. The machining time without adaptive control, which is the total time of the black bars, is calculated and displayed as 22 minutes and 29 seconds in the machining time display field 74. The machining time (estimated value) with adaptive control, which is the total time of the bars for speed-increasing hatching and speed-decreasing hatching, and the black bars in the spindle load range where adaptive control is not performed, is calculated and displayed as 21 minutes and 31 seconds in the machining time (estimated value) display field 76.

[0038] The operator observes the display in the speed adjustment window 70, and if the estimated machining time differs from the target value, re-enters the AC upper limit and / or AC lower limit values, presses the calculate button 94 to recalculate and redisplay. This is repeated until the estimated machining time approaches the target value. Once the estimated machining time approaches the target value, the operator decides to machine under those conditions and presses the execute button 92 to perform machining with the desired adaptive control. Note that the display and settings of the speed adjustment window 70 may be performed using a personal computer, server, or tablet used as the machining time estimation device 10 instead of the control panel 50.

[0039] As explained above, there are two methods for calculating machining time: one based on time-series data as shown in Figure 3, and another based on histograms as shown in Figure 4. However, the histogram-based method has more advantages for the following reasons: The histogram-based method can use less data than time-series data, thus reducing the data handling capacity of the machining time calculation unit 16. This is particularly effective for machining with long machining times. In addition, while time-series data results in a graph with a long horizontal axis (time T), making it difficult to read and understand, the histogram uses the spindle load band on the horizontal axis, resulting in a more compact graph that is easier for operators to understand intuitively at a glance.

[0040] Instead of the operator looking at the speed adjustment window 70 on the control panel 50 to determine the conditions for adaptive control, the target machining time (estimated value) may be pre-entered into the parameter storage unit 14, the machining time calculation unit 16 extracts various parameters from the parameter storage unit 14, performs a calculation to estimate the machining time with adaptive control applied, automatically determines the AC upper limit (second threshold for spindle load) and AC lower limit (first threshold for spindle load) that are close to the target machining time, and a command is sent from the feed rate adaptive control unit 12 to the NC device 30 without human intervention to execute machining with adaptive control added. The machining time estimation and setting of appropriate first and second thresholds for machining load described in this embodiment will be performed for each tool if the machining program includes multiple tools.

[0041] 10 Machining time estimation device 12 Speed ​​adaptation control unit 14 Parameter storage unit 16 Machining time calculation unit 18 Image generation unit 20 Spindle load storage unit 22 Spindle load acquisition unit 30 NC device 50 Control panel 80 Histogram 82 Parameter input box 84 Upper limit box 86 Lower limit box 88 Speed ​​increase override value box 90 Speed ​​reduction override value box 100 NC machine tool

Claims

1. A method for estimating machining time when executing a machining program on a machine tool capable of feed rate adaptive control, comprising: a step of setting a first threshold for machining load and a second threshold greater than the first threshold; a step of acquiring the machining load moment by moment when actually machining a workpiece according to a predetermined machining program or when performing a machining simulation; a step of storing the acquired machining load in relation to time; a step of determining the total machining time required to machine the workpiece based on the stored machining load and time; a step of setting a speed-increasing override value greater than 100% for use in a machining load range where the machining load is smaller than the first threshold; a step of setting a deceleration override value less than 100% for use in a machining load range where the machining load is larger than the second threshold; and a step of calculating the corrected total machining time when the feed rate specified in the machining program is adaptively controlled according to the speed-increasing override value and the deceleration override value.

2. The machining time estimation method according to claim 1, further comprising the step of displaying the first threshold and the second threshold of the machining load, and the total machining time and the corrected total machining time on a display device.

3. A machining time estimation method according to claim 1 or 2, wherein in a machining load range for which a speed-increasing override value is set, the machining time obtained when machining a workpiece according to the machining program in that load range is multiplied by the reciprocal of the speed-increasing override value to obtain the machining time obtained when adaptive control is performed, and in a machining load range for which a deceleration override value is set, the machining time obtained when machining a workpiece according to the machining program in that load range is multiplied by the reciprocal of the deceleration override value to obtain the machining time obtained when adaptive control is performed.

4. The machining time estimation method according to claim 1 or 2, wherein the speed-increasing override value gradually increases as the machining load decreases from the first threshold in a load range smaller than the first threshold, and the deceleration override value gradually decreases as the machining load increases from the second threshold in a load range larger than the second threshold.

5. The machining time estimation method according to claim 1 or 2, wherein the machining time estimation method is performed for each tool used to machine the workpiece.

6. A device for estimating machining time when executing a machining program on a machine tool capable of adaptive feed rate control, comprising: a parameter storage unit that stores a first threshold for machining load, a second threshold greater than the first threshold, a maximum value of a speed-increasing override exceeding 100% applied in a machining load range where the machining load is less than the first threshold, and a minimum value of a deceleration override less than 100% applied in a machining load range where the machining spindle load is greater than the second threshold; a machining load acquisition unit that acquires the machining load moment by moment when a workpiece is actually machined or when a machining simulation is performed according to the machining program; a machining load storage unit that stores the acquired machining load in association with time; and a machining time calculation unit that calculates the total machining time required to machine a workpiece based on the stored machining load and time, and the corrected total machining time when the feed rate specified in the machining program is adaptively controlled according to the maximum value of the speed-increasing override and the minimum value of the deceleration override.

7. A machine tool capable of adaptive feed rate control and for machining a workpiece according to a machining program, comprising: a parameter storage unit that stores a first threshold for machining load, a second threshold greater than the first threshold, a maximum value of a speed-increasing override exceeding 100% applied in a machining load range where the machining load is less than the first threshold, and a minimum value of a deceleration override less than 100% applied in a machining load range where the machining load is greater than the second threshold; a machining load acquisition unit that acquires the machining load moment by moment when machining a workpiece according to the machining program; a machining load storage unit that stores the acquired machining load in association with time; a machining time calculation unit that calculates the total machining time required to machine the workpiece based on the stored machining load and time, and the corrected total machining time when the feed rate specified in the machining program is adaptively controlled according to the maximum value of the speed-increasing override and the minimum value of the deceleration override; and a display device that displays the total machining time when machining a workpiece according to the machining program and the corrected total machining time. A machine tool comprising the above, characterized in that the first threshold and the second threshold are determined such that the total corrected machining time is shorter than the total machining time.

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