Numerical control device and computer-readable storage medium

Abstract

This numerical control device comprises: a spindle load detection unit for detecting time series data about a load applied to a spindle during machining of a workpiece; a target load setting unit for setting a target load to be applied to the spindle; a machining time prediction unit for predicting, on the basis of the time series data, machining time when a forwarding speed of the spindle is controlled to make the load applied to the spindle equal to the target load; and a machining time output unit for outputting data about the predicted machining time.

Description

[Technical field]

[0001] The present disclosure relates to a numerical control device for controlling a machine tool, and a computer-readable storage medium. [Background technology]

[0002] In machine tools, a technique is known for controlling the feed speed of the spindle so that the load on the spindle is constant (for example, see Patent Document 1). This control can extend the life of the tool. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-117458 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, when the feed speed of the spindle is controlled so that the load on the spindle is constant, the feed speed changes according to the load, making it difficult to predict the machining time in advance.

[0005] The present disclosure aims to provide a numerical control device and a computer-readable storage medium that are capable of predicting machining time in advance when controlling the feed speed of a spindle so that the load on the spindle is constant. [Means for solving the problem]

[0006] A numerical control device includes a spindle load detection unit that detects time series data of a load applied to a spindle when a workpiece is machined, a target load setting unit that sets a target load applied to the spindle, a machining time prediction unit that predicts, based on the time series data, a machining time when a feed speed of the spindle is controlled so that the load applied to the spindle becomes the target load, and a machining time output unit that outputs data of the predicted machining time, and the machining time prediction unit assumes that the load applied to the spindle and the feed speed are proportional to each other. From target load The feed rate is calculated, and the processing time is predicted based on the calculated feed rate.

[0007] A computer-readable storage medium stores instructions for causing a computer to execute the following: detecting time series data of the load applied to the spindle when machining a workpiece; setting a target load applied to the spindle; predicting a machining time when the feed speed of the spindle is controlled so that the load applied to the spindle becomes the target load based on the time series data; and outputting data of the predicted machining time. In particular, the load applied to the spindle and the feed speed are assumed to be proportional to each other. From target load Instructions are stored to cause a computer to calculate a feed rate and predict a machining time based on the calculated feed rate. Effect of the Invention

[0008] According to the present disclosure, it becomes possible to predict the machining time in advance when controlling the feed speed of the spindle so that the load on the spindle is constant. [Brief description of the drawings]

[0009] [Figure 1] FIG. 2 is a diagram illustrating an example of a hardware configuration of a machine tool. [Diagram 2] FIG. 2 is a block diagram showing an example of a function of a numerical control device. [Diagram 3] 10 is a diagram illustrating an example of time-series data stored in a spindle load storage unit. FIG. [Figure 4A] 11 is a diagram illustrating a method in which a processing time prediction unit predicts a processing time. FIG. [Figure 4B]11 is a diagram illustrating a method in which a processing time prediction unit predicts a processing time. FIG. [Figure 4C] 11 is a diagram illustrating a method in which a processing time prediction unit predicts a processing time. FIG. [Figure 4D] 11 is a diagram illustrating a method in which a processing time prediction unit predicts a processing time. FIG. [Diagram 5] 11 is a diagram illustrating a method in which a processing time prediction unit predicts a processing time. FIG. [Figure 6] 4 is a flowchart showing an example of a flow of processing executed by a numerical control device. [Figure 7] FIG. 13 is a diagram illustrating an example of a processing time prediction unit including a learning unit. [Figure 8] FIG. 13 is a diagram showing an example of a processing time displayed on the input / output device; [Figure 9] FIG. 2 is a block diagram showing an example of a function of a numerical control device. [Figure 10] FIG. 11 is a diagram showing an example of time-series data of a load applied to a spindle. [Figure 11] FIG. 13 is a diagram illustrating an example of a frequency distribution. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. Note that not all combinations of features described in the following embodiment are necessarily required to solve the problem. In addition, unnecessary detailed description may be omitted. In addition, the following description of the embodiment and the drawings are provided to enable a person skilled in the art to fully understand the present disclosure, and are not intended to limit the scope of the claims.

[0011] 1 is a diagram showing an example of a hardware configuration of a machine tool 1. The machine tool 1 is, for example, a lathe, a machining center, or a multi-tasking machine.

[0012] The machine tool 1 includes, for example, a numerical control device 2, an input / output device 3, a servo amplifier 4 and a servo motor 5, a spindle amplifier 6 and a spindle motor 7, and auxiliary equipment 8.

[0013] The numerical control device 2 is a device that controls the entire machine tool 1. The numerical control device 2 includes a CPU (Central Processing Unit) 201, a bus 202, a ROM (Read Only Memory) 203, a RAM (Random Access Memory) 204, and a non-volatile memory 205.

[0014] The CPU 201 is a processor that controls the entire numerical control device 2 in accordance with a system program. The CPU 201 reads the system program and the like stored in the ROM 203 via the bus 202. The CPU 201 also controls the servo motor 5 and the spindle motor 7 in accordance with a machining program.

[0015] The CPU 201 performs, for example, analysis of a machining program and output of a control command to the servo motor 5 for each control period.

[0016] The bus 202 is a communication path that connects each piece of hardware in the numerical control device 2 to each other. The pieces of hardware in the numerical control device 2 exchange data via the bus 202.

[0017] The ROM 203 is a storage device that stores a system program for controlling the entire numerical control device 2. The ROM 203 functions as a computer-readable storage medium.

[0018] The RAM 204 is a storage device that temporarily stores various data and functions as a working area for the CPU 201 to process various data.

[0019] The nonvolatile memory 205 is a storage device that retains data even when the machine tool 1 is turned off and power is not being supplied to the numerical control device 2. The nonvolatile memory 205 stores, for example, a machining program and various parameters input from the input / output device 3. The nonvolatile memory 205 functions as a computer-readable storage medium. The nonvolatile memory 205 is formed, for example, of an SSD (Solid State Drive).

[0020] The numerical control device 2 further includes an interface 206 , an axis control circuit 207 , a spindle control circuit 208 , a PLC (Programmable Logic Controller) 209 , and an I / O unit 210 .

[0021] The interface 206 connects the bus 202 and the input / output device 3. The interface 206 sends, for example, various data processed by the CPU 201 to the input / output device 3.

[0022] The input / output device 3 is a device that receives various data via the interface 206 and displays the various data. The input / output device 3 also accepts input of various data and sends the various data to the CPU 201 via the interface 206. The input / output device 3 includes a display such as an LCD (Liquid Crystal Display), a keyboard, a mouse, and the like. The input / output device 3 may also be a touch panel.

[0023] The axis control circuit 207 is a circuit that controls the servo motor 5. The axis control circuit 207 receives a control command from the CPU 201 and outputs a command to drive the servo motor 5 to the servo amplifier 4. The axis control circuit 207 sends, for example, a torque command to control the torque of the servo motor 5 to the servo amplifier 4.

[0024] The servo amplifier 4 receives a command from the axis control circuit 207 and supplies a current to the servo motor 5 .

[0025] The servo motor 5 is driven by receiving a current supply from the servo amplifier 4. The servo motor 5 is connected to, for example, a ball screw that drives a tool post, a spindle head, or a table. When the servo motor 5 is driven, the structures of the machine tool 1, such as the tool post, the spindle head, or the table, move, for example, in the X-axis direction, Y-axis direction, or Z-axis direction. The servo motor 5 may include a built-in speed detector (not shown) that detects the feed speed of each axis.

[0026] The spindle control circuit 208 is a circuit for controlling the spindle motor 7. The spindle control circuit 208 receives a control command from the CPU 201 and outputs a command for driving the spindle motor 7 to the spindle amplifier 6. The spindle control circuit 208 sends, for example, a torque command for controlling the torque of the spindle motor 7 to the spindle amplifier 6.

[0027] The spindle amplifier 6 receives a command from the spindle control circuit 208 and supplies a current to the spindle motor 7. The spindle amplifier 6 includes an ammeter 61 that measures the current value of the current supplied to the spindle motor 7.

[0028] The ammeter 61 detects the current value of the current supplied to the spindle motor 7. The ammeter 61 sends data indicating the detected current value to the CPU 201.

[0029] The spindle motor 7 is driven by receiving a current supply from the spindle amplifier 6. The spindle motor 7 is connected to a main shaft and rotates the main shaft.

[0030] The PLC 209 is a device that executes a ladder program to control the auxiliary device 8. The PLC 209 sends commands to the auxiliary device 8 via the I / O unit 210.

[0031] The I / O unit 210 is an interface that connects the PLC 209 and the auxiliary device 8. The I / O unit 210 transmits commands received from the PLC 209 to the auxiliary device 8.

[0032] The auxiliary device 8 is installed in the machine tool 1 and performs auxiliary operations in the machine tool 1. The auxiliary device 8 operates based on commands received from the I / O unit 210. The auxiliary device 8 may be a device installed in the periphery of the machine tool 1. The auxiliary device 8 is, for example, a tool changer, a cutting fluid ejection device, or an opening / closing door drive device.

[0033] Next, an example of the function of the numerical control device 2 will be described. The numerical control device 2 detects the load on the spindle when the workpiece is machined at the feed rate commanded by the machining program. Furthermore, the numerical control device 2 predicts the machining time when the workpiece is machined so that the load on the spindle becomes the target load, based on the data of the detected load on the spindle.

[0034] 2 is a block diagram showing an example of functions of the numerical control device 2. The numerical control device 2 includes a program storage unit 211, a control unit 212, a spindle load detection unit 213, a spindle load storage unit 214, a target load reception unit 215, a target load setting unit 216, a machining time prediction unit 217, and a machining time output unit 218.

[0035] The program memory unit 211 and the spindle load memory unit 214 are realized by storing the machining program input from the input / output device 3, etc., and the data input from the ammeter 61 and various sensors in the RAM 204 or the non-volatile memory 205.

[0036] The control unit 212, the spindle load detection unit 213, the target load receiving unit 215, the target load setting unit 216, the machining time prediction unit 217, and the machining time output unit 218 are realized, for example, by the CPU 201 performing calculations using the system program stored in the ROM 203 and the machining program and various data stored in the non-volatile memory 205.

[0037] The program storage unit 211 stores a machining program. The machining program is a program for machining a workpiece by operating each part of the machine tool 1. In the machining program, the movement path of the tool, the feed speed of the tool, the rotation speed of the spindle, and the like are commanded using G codes, M codes, and the like.

[0038] The control unit 212 controls each part of the machine tool 1 based on a machining program. The control unit 212 controls the servo motor 5 and the spindle motor 7, for example.

[0039] The control unit 212 performs constant speed control based on the machining program. The constant speed control is a control for moving the spindle at a feed speed specified in the machining program.

[0040] Furthermore, the control unit 212 performs constant load control based on the machining program. The constant load control is a control for changing the feed speed of the spindle specified in the machining program so that the load applied to the spindle becomes the load set by the target load setting unit 216. The constant load control can suppress the fluctuation of the load applied to the spindle more than the constant speed control.

[0041] The spindle load detection unit 213 detects time series data of the load applied to the spindle when the workpiece is machined based on the machining program. The spindle load detection unit 213 also detects time series data indicating the feed speed of the spindle. In other words, the spindle load detection unit 213 detects the load applied to the spindle and the feed speed of the spindle at predetermined intervals while the workpiece is machined based on the machining program.

[0042] The spindle load detection unit 213 detects the load applied to the spindle based on, for example, a current value indicated by an ammeter 61 built into the spindle amplifier 6. The spindle load detection unit 213 also detects the feed speed of the spindle based on data detected by a speed detector built into the servo motor 5. The load applied to the spindle is a load torque applied in the opposite direction to the rotation direction of the spindle.

[0043] The spindle load storage unit 214 stores time series data of the load applied to the spindle detected by the spindle load detection unit 213. That is, the spindle load storage unit 214 stores time series data indicating the load applied to the spindle when a workpiece is machined. The spindle load storage unit 214 also stores time series data indicating the feed speed of the spindle when a workpiece is machined. The time series data stored in the spindle load storage unit 214 is time series data detected when constant speed control of the spindle is performed based on the machining program.

[0044] Fig. 3 is a diagram for explaining an example of time series data stored in the spindle load storage unit 214. That is, the time series data shown in Fig. 3 is data detected when machining is performed under constant speed control. Fig. 3 shows that the spindle load storage unit 214 stores, in order, time series data L, 2L, 3L, 4L, 3L, 2L, and L indicating loads detected at each predetermined cycle T.

[0045] Now, let us return to the explanation of FIG.

[0046] The target load receiving unit 215 receives an input of a value indicating a target load applied to the spindle when constant load control is performed. The target load receiving unit 215 receives a value input by an operator using, for example, the input / output device 3. The operator inputs, for example, using the input / output device 3, a target load applied to the spindle when a workpiece is machined under constant load control.

[0047] The target load setting unit 216 sets a target load to be applied to the spindle received by the target load receiving unit 215. The target load setting unit 216 sets the target load, for example, by storing data indicating the target load in a predetermined register (not shown).

[0048] The machining time prediction unit 217 predicts the machining time when the feed speed of the spindle is controlled so that the load on the spindle becomes the target load, based on the time series data stored in the spindle load storage unit 214. In other words, the machining time predicted by the machining time prediction unit 217 is the machining time when the machining program executed when the time series data stored in the spindle load storage unit 214 is acquired is executed under constant load control. In other words, the machining time prediction unit 217 predicts the machining time when the machining program is executed so that the target load set by the target load setting unit 216 is applied to the spindle, based on the time series data detected when constant speed control is performed. The machining time prediction unit 217 predicts the machining time assuming that the load on the spindle and the feed speed of the spindle are proportional to each other.

[0049] 4A to 4D and 5 are diagrams for explaining a method for predicting the machining time by the machining time prediction unit 217. The machining time prediction unit 217 first reads out time series data of the load on the spindle stored in the spindle load storage unit 214. The time series data indicating the load on the spindle is data detected at every predetermined period T.

[0050] Next, the processing time prediction unit 217 calculates the time for each period. To T The machining time is calculated when the load applied to the spindle is changed to a target load and machining is performed.

[0051] For example, under the assumption that the load on the spindle and the spindle feed speed are proportional, to change the load L to a target load 2L, it is necessary to double the spindle feed speed. In this case, the machining time for machining the section where the load L is detected is T / 2 (see Figure 4A). Because the load in the section where the load 2L is detected is the same as the target load, the spindle feed speed is not changed. In other words, the machining time T does not change (see Figure 4B).

[0052] If the load in the section where a load of 3L is detected is changed to 2L, the machining time for machining this section will be 3T / 2 (see FIG. 4C). Similarly, if the load in the section where a load of 4L is detected is changed to 2L, the machining time for machining this section will be 2T (see FIG. 4D).

[0053] Next, the machining time prediction unit 217 sums up the machining times when the load on the spindle in each cycle T is changed to the target load (see FIG. 5). This allows the machining time prediction unit 217 to predict the machining time when constant load control is performed so that the load on the spindle becomes the target load. The machining time prediction unit 217 may further predict the feed speed in each cycle when the feed speed is controlled so that the load on the spindle becomes the target load.

[0054] The machining time output unit 218 outputs data indicating the machining time predicted by the machining time prediction unit 217. For example, the machining time output unit 218 outputs data indicating the machining time and data indicating the target load to the input / output device 3, and causes the input / output device 3 to display the machining time and the target load. The machining time output unit 218 may output the feed speed of the spindle calculated in the process of the machining time prediction unit 217 predicting the machining time. In this case, the machining time output unit 218 may output data indicating the feed speed of the spindle so that the feed speed of the spindle for each period T is displayed in a graph.

[0055] The control unit 212 may execute the machining program under constant load control to machine the workpiece so that the target load received by the target load receiving unit 215 is applied to the spindle. In this case, the workpiece can be machined in the machining time predicted by the machining time prediction unit 217 or in a machining time that is close to the predicted time.

[0056] Next, the flow of processing executed by the numerical control device 2 will be described.

[0057] 6 is a flowchart showing an example of a flow of processing executed by the numerical control device 2. First, the spindle load detection unit 213 detects time-series data indicating the load applied to the spindle when a workpiece is machined under constant speed control based on a machining program (step S1).

[0058] Next, the spindle load storage unit 214 stores time-series data indicating the load acting on the spindle detected by the spindle load detection unit 213 (step S2).

[0059] Next, the target load receiving unit 215 receives an input of a value indicating a target load applied to the spindle (step S3). Next, the target load setting unit 216 sets the target load accepted by the target load accepting unit 215 (step S4).

[0060] Next, the machining time prediction unit 217 predicts the machining time when the feed speed of the spindle is controlled so that the load applied to the spindle becomes the target load (step S5).

[0061] Finally, the processing time output unit 218 outputs data indicating the processing time predicted by the processing time prediction unit 217 (step S6), and the process ends.

[0062] As described above, the numerical control device 2 includes a spindle load detection unit 213 that detects time series data of the load applied to the spindle when the workpiece is machined, a target load setting unit 216 that sets a target load applied to the spindle, a machining time prediction unit 217 that predicts the machining time when the feed speed of the spindle is controlled so that the load applied to the spindle becomes the target load based on the time series data, and a machining time output unit 218 that outputs data of the predicted machining time. This allows the numerical control device 2 to output the machining time when the feed speed of the spindle is controlled so that the target load is applied to the spindle. As a result, the operator can determine the load applied to the spindle in consideration of the output machining time. For example, it enables the operator to determine the load applied to the spindle so that the machining time is matched to the cycle time of the machining of the previous process.

[0063] The numerical control device 2 further includes a target load receiving unit 215 that receives an input of a value indicating the target load set by the target load setting unit 216. Therefore, the numerical control device 2 can predict the machining time according to the input target load.

[0064] In addition, the machining time prediction unit 217 predicts the machining time assuming that the load on the spindle is proportional to the feed rate, so that the machining time prediction unit 217 can predict the machining time without performing complex calculations.

[0065] Furthermore, the machining time prediction unit 217 predicts the feed speed of the spindle when the feed speed of the spindle is controlled so that the load applied to the spindle becomes the target load. This allows the operator to determine whether the feed speed of the spindle is appropriate for machining the workpiece and set the target load.

[0066] The numerical control device 2 further includes a spindle load storage unit 214 that stores time-series data detected by the spindle load detection unit 213. This allows the machining time prediction unit 217 to predict the machining time any number of times based on various target loads accepted by the target load acceptance unit 215.

[0067] In the above-described embodiment, the machining time prediction unit 217 predicts the machining time assuming that the load on the spindle is proportional to the feed speed of the spindle. However, the machining time prediction unit 217 may predict the machining time based on a correlation model that indicates the relationship between the load on the spindle and the feed speed of the spindle.

[0068] 7 is a diagram illustrating an example of the processing time prediction unit 217. The processing time prediction unit 217 includes a learning unit 221, a correlation model storage unit 222, and a prediction unit 223. Note that the configuration other than the processing time prediction unit 217 is the same as the configuration of the above-described embodiment.

[0069] The learning unit 221 generates a correlation model indicating the relationship between the load on the spindle and the feed speed of the spindle, based on time series data indicating the load on the spindle and time series data indicating the feed speed of the spindle stored in the spindle load storage unit 214. The learning unit 221 generates the correlation model using, for example, a regression equation, a Support Vector Machine (SVM), or a neural network.

[0070] The correlation model storage unit 222 stores the correlation model generated by the learning unit 221 .

[0071] The prediction unit 223 predicts the machining time when the spindle is controlled so that the load applied to the spindle becomes the target load, by using the correlation model stored in the correlation model storage unit 222. Furthermore, the prediction unit 223 may predict the feed speed of the spindle when the spindle is controlled so that the load applied to the spindle becomes the target load, by using the correlation model.

[0072] Data indicating the processing time predicted by the prediction unit 223 is output by the processing time output unit 218.

[0073] In the above-described embodiment, the machining time prediction unit 217 further includes a learning unit 221 that learns the relationship between the load applied to the spindle and the feed rate, and the machining time prediction unit 217 predicts the machining time based on the relationship learned by the learning unit 221. Therefore, the machining time prediction unit 217 can predict the machining time with high accuracy.

[0074] The target load receiving unit 215 may receive, for example, a value indicating the ratio of the target torque to the rated torque as the value indicating the target load applied to the spindle. For example, the target load can be set by receiving an input of a numerical value such as 50%, 55%, 60%, or 65%.

[0075] Furthermore, although the numerical control device 2 in the above-described embodiment includes the target load receiving unit 215, the numerical control device 2 does not necessarily have to include the target load receiving unit 215. In this case, the numerical control device 2 may store values ​​indicating a plurality of target loads in advance and predict each of the machining times when constant load control is performed so that each of the plurality of target loads is applied to the spindle.

[0076] Fig. 8 is a diagram showing an example of a display of a machining time displayed on the input / output device 3 when a machining time is predicted for each of a plurality of target loads. In the numerical control device 2, for example, a value indicating a ratio of a target torque to a rated torque is stored in advance as a target load. In the example shown in Fig. 8, 50%, 53%, 56%, 59%, 62%, 65%, 68%, and 71% are stored as the target loads.

[0077] The machining time prediction unit 217 predicts each machining time when constant load control is performed so that each of these target loads is applied to the spindle. Data indicating the machining time predicted by the machining time prediction unit 217 is output by the machining time output unit 218 and displayed on the display screen of the input / output device 3.

[0078] On the display screen, for example, a straight line with a scale extending to the left and right is displayed. Above this straight line, a value indicating the ratio of the target torque to the rated torque is displayed as the target load.

[0079] Below the straight line, predicted machining times are displayed corresponding to the respective target loads. For example, a machining time of 11:00 is displayed corresponding to a target load of 50%. A machining time of 10:30 is displayed corresponding to a target load of 53%. A machining time of 10:00 is displayed corresponding to a target load of 56%. A machining time of 9:30 is displayed corresponding to a target load of 59%. A machining time of 9:00 is displayed corresponding to a target load of 62%. A machining time of 8:00 is displayed corresponding to a target load of 65%. A machining time of 7:00 is displayed corresponding to a target load of 68%. A machining time of 6:00 is displayed corresponding to a target load of 71%.

[0080] By displaying the machining time in this manner, the operator can easily grasp the respective machining times when the spindle is controlled so as to apply each load.

[0081] In addition, the ratio of the machining time when the constant load control is performed at each target load to the machining time when the machining program is executed under constant speed control may be displayed below the area where each machining time is displayed. For example, in the example shown in Fig. 8, the machining time when the constant speed control is performed is 10:00, and the ratio of the machining time when the constant load control is performed at each target load to this machining time is displayed in parentheses.

[0082] 8, when the target load and the machining time corresponding to the target load are displayed side by side on the input / output device 3, any one of the target loads may be selected on the display screen. In this case, the workpiece may be machined under constant load control so that the selected target load is applied to the spindle.

[0083] In the above-described embodiment, the numerical control device 2 includes the spindle load storage unit 214. However, the numerical control device 2 does not necessarily have to include the spindle load storage unit 214.

[0084] 9 is a block diagram showing an example of the functions of the numerical control device 2. The numerical control device 2 includes a generating unit 224 and a frequency distribution storing unit 225 instead of the spindle load storing unit 214. The other configurations are the same as those of the numerical control device 2 shown in FIG.

[0085] The generating unit 224 is realized, for example, by the CPU 201 performing arithmetic processing using the system program stored in the ROM 203 and the processing program and various data stored in the non-volatile memory 205. The frequency distribution storage unit 225 is realized, for example, by storing in the RAM 204 or the non-volatile memory 205 data generated by the CPU 201 performing arithmetic processing using the system program and various data.

[0086] The generating unit 224 generates frequency distribution data based on the time series data detected by the spindle load detecting unit 213 .

[0087] FIG. 10 is a diagram showing time series data of the load applied to the spindle detected by the spindle load detection unit 213. That is, the time series data shown in FIG. 10 is data detected when machining is performed under constant speed control. FIG. 11 is a diagram showing an example of a frequency distribution. The generation unit 224 divides the load applied to the spindle detected by the spindle load detection unit 213 into a plurality of classes and counts the frequency of each class. For example, the generation unit 224 divides the detected load into one of four classes L, 2L, 3L, and 4L. The generation unit 224 divides the value of the load detected by the spindle load detection unit 213 into one of classes L, 2L, 3L, and 4L, for example, by rounding it off.

[0088] For example, the generation unit 224 assigns loads of magnitude equal to or greater than 0.5L and less than 1.5L to class L. Similarly, the generation unit 224 assigns loads of magnitude equal to or greater than 1.5L and less than 2.5L to class 2L. Similarly, the generation unit 224 assigns loads of magnitude equal to or greater than 2.5L and less than 3.5L to class 3L. Similarly, the generation unit 224 assigns loads of magnitude equal to or greater than 3.5L and less than 4.5L to class 4L. In the example shown in FIG. 11, data indicating four loads are assigned to class L, five to class 2L, two to class 3L, and one to class 4L.

[0089] The frequency distribution storage unit 225 stores the frequency distribution data generated by the generation unit 224.

[0090] The processing time prediction unit 217 predicts the processing time based on the frequency distribution data stored in the frequency distribution storage unit 225. The processing time prediction unit 217 calculates the processing time when the load indicated by each class is changed to the target load and processing is performed, and calculates the processing time by adding up the processing times of each class. The processing time T L , T 2L , T 3L and T 4L , can be calculated by (frequency) x (class value) x (period) / (target load).

[0091] For example, the processing time T L is T L = 4 × L × T / 2L = 2T. Similarly, the processing time T calculated for class 2L is 2L is T 2L = 5 × 2L × T / 2L = 5T. Similarly, the processing time T 3L is T 3L = 2 × 3L × T / 2L = 3T. Similarly, the processing time T 4L is T 4L = 1 × 4L × T / 2L = 2T. The processing time calculated for each class is added together to obtain a processing time of 12T.

[0092] In the above-described embodiment, the numerical control device 2 further includes a frequency distribution storage unit 225 that stores data indicating a frequency distribution generated based on the time series data detected by the spindle load detection unit 213. Therefore, the amount of data stored can be reduced compared to the case where the spindle load storage unit 214 stores time series data.

[0093] The processing time calculated for each class does not have to be calculated in the above-mentioned order. For example, the processing time may be calculated by adding up the values ​​of (frequency) x (class value) calculated for each class, and then multiplying the sum by (cycle) / (target load). [Explanation of symbols]

[0094] 1 Machine tools 2. Numerical control device 201 CPU 202 Bus 203 ROM 204 RAM 205 Non-volatile memory 206 Interface 207 Axis control circuit 208 Spindle control circuit 209 PLC 210 I / O Unit 211 Program storage unit 212 Control section 213 Spindle load detector 214 Spindle load storage section 215 Target Load Reception Unit 216 Target load setting unit 217 Machining time prediction section 218 Processing time output section 221 Learning Department 222 Correlation Model Memory Unit 223 Prediction Department 224 Generation part 225 Frequency distribution memory section 3 Input / Output Devices 4 Servo Amplifier 5. Servo motor 6 Spindle Amplifier 61 Ammeter 7 Spindle motor 8 Auxiliary equipment

Claims

1. a spindle load detection unit that detects time series data of the load applied to the spindle when the workpiece is machined; a target load setting unit that sets a target load applied to the spindle; a machining time prediction unit that predicts, based on the time series data, a machining time when a feed speed of the spindle is controlled so that a load applied to the spindle becomes the target load; A processing time output unit that outputs data of the predicted processing time; Equipped with The machining time prediction unit is a numerical control device that calculates the feed speed from the target load assuming that the load on the spindle and the feed speed are proportional to each other, and predicts the machining time based on the calculated feed speed.

2. The numerical control device according to claim 1 , further comprising a target load receiving unit that receives an input of a value indicating the target load set by the target load setting unit.

3. The numerical control device according to claim 1 or 2, wherein the processing time output unit further outputs data indicating a relationship between the target load and the predicted processing time.

4. 4. The numerical control device according to claim 1, wherein the machining time prediction unit further predicts the feed speed when the feed speed is controlled so that the load applied to the spindle becomes the target load.

5. 5. The numerical control device according to claim 1, further comprising a spindle load storage unit that stores the time series data detected by the spindle load detection unit.

6. 6. The numerical control device according to claim 1, further comprising a frequency distribution storage unit that stores frequency distribution data generated based on the time series data detected by the spindle load detection unit.

7. Detecting time series data of a load applied to a spindle when a workpiece is machined; Setting a target load on the spindle; predicting a machining time when a feed speed of the spindle is controlled so that a load applied to the spindle becomes the target load based on the time series data; Outputting data of the predicted processing time; A computer-readable storage medium storing instructions for causing a computer to execute the method, the storage medium further comprising: A storage medium that stores instructions that cause a computer to execute the following: calculating the feed speed from the target load assuming that the load on the spindle and the feed speed are proportional to each other; and predicting the machining time based on the calculated feed speed.

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