CONTROL DEVICE

Abstract

Control device (1) which regulates a feed rate based on a load exerted on a spindle during the machining of a workpiece, wherein the control device (1) comprises: a spindle load storage unit (220) that stores data relating to the load applied to the spindle; a quantile specification unit (160) that specifies a predetermined quantile; a target spindle load calculation unit (140) which calculates the quantile specified by the quantile specification unit (160) in the data relating to the load applied to the spindle, which are stored in the spindle load storage unit (220), as the target spindle load; a spindle load measuring unit (120) that measures the load exerted on the spindle; and a control unit (110) that controls the feed rate of the spindle with respect to the workpiece in such a way that the load applied to the spindle becomes the target spindle load, exhibits.

Description

Technical field

[0001] The present invention relates to a control device and more precisely to a control device that controls a feed rate in such a way that a load exerted on a spindle becomes constant. General state of the art

[0002] There is a technology that improves cutting speed and extends the service life of cutting tools by controlling the feed rate to maintain a constant load on the spindle. Varying the feed rate in such a way as to keep the spindle load constant allows for a reduction in cycle time and an extension of tool life. Various methods for controlling the feed rate in accordance with the spindle load are conceivable, and generally, a PID controller (PTL 1, 2, etc.) can be used to maintain a constant value for an object.

[0003] Fig. Figure 7 is an example of a block diagram when a PID controller is used to maintain a constant spindle load. As shown in Fig. As shown in Figure 7, a control device for performing the aforementioned control defines a target spindle load and then obtains the spindle load detected by a machine during the machining of a workpiece as a feedback value. The control device then calculates a difference e L (t) between the achieved spindle load and the specified target spindle load and regulates a speed override O(t) based on the calculated value. List of literature on patent literature PTL 1: Japanese Patent Publication JP 2017 - 19A1 536 A PTL 2: Japanese Patent Publication JP 2019 - 149 041

[0004] DE 10 2019 003 731 A1 describes a numerical control device with a vibration amplitude determination unit for determining the amplitude of a vibration component of a spindle load attributable to the rotation of a spindle. An object of the invention is to propose a control device for controlling a feed rate based on a load exerted on a spindle during the machining of a workpiece. This object is achieved by a control device according to claim 1 of the invention. Brief description of the invention: Technical problem

[0005] When the control described above is implemented, it is necessary to determine a target spindle load, which represents a target value for the load exerted on the spindle. However, setting the target spindle load to a suitable value requires expertise acquired through manual effort over a large number of repeated machining operations. Furthermore, the appropriate target spindle load also varies depending on the tools used for machining, the shape and material of the workpieces to be machined, and so on, and must therefore be redefined each time.

[0006] Regarding the method for easily determining the target spindle load, one approach is to perform a trial machining operation on the workpiece and define the maximum load exerted on the spindle during this operation as the target spindle load. However, using this method for machining operations where there are points where the load momentarily increases leads to the problem that the target spindle load is set too high. If a suitable implementation of both cycle time reduction and tool life extension is to be considered for various types of machining, it is necessary to enable users to easily define the target spindle load using the spindle load measured under stable machining conditions as a reference. Solution to the problem

[0007] A control device according to one embodiment of the present invention solves the above problem by defining a pre-specified quantile as the target spindle load for a set of load values ​​applied to a spindle and measured during the machining of a workpiece. When a workpiece is machined, the load value changes depending on the section being machined, the type of machining, the way the tool comes into contact with the workpiece, and so on. However, the proportion of time during the machining process when an extremely high load is applied to the spindle, or when the spindle load is extremely low, is small.In the present invention, when measuring the load exerted on the spindle during the machining process of a workpiece, a predetermined load or load range, measured over a relatively long period, is defined as the stable machining load. Furthermore, a machining area in which a stable machining load is measured is defined as a section with stable machining. In the present invention, the section with stable machining is identified based on a load exerted on the spindle measured during a trial machining operation or the like, and the stable machining load measured in the identified section with stable machining can be automatically set as the target spindle load.

[0008] One embodiment of the present invention is a control device that regulates a feed rate based on a load exerted on a spindle during the machining of a workpiece. The control device comprises a spindle load storage unit that stores data relating to the load exerted on the spindle; a quantile specification unit that specifies a predetermined quantile; a target spindle load calculation unit that calculates the quantile specified by the quantile specification unit in the data relating to the load exerted on the spindle, stored in the spindle load storage unit, as the target spindle load; a spindle load measuring unit that measures the load exerted on the spindle; and a control unit that controls the feed rate of the spindle with respect to the workpiece such that the load exerted on the spindle becomes the target spindle load. Advantageous effects of the invention

[0009] According to one embodiment of the present invention, when the feed rate is controlled in such a way that the load exerted on a spindle becomes constant, it is no longer necessary for a person to determine the target spindle load suitable for the tool and the workpiece in advance based on experience and so on, but the load of a section with stable machining can be used as the target spindle load. Brief description of the drawings Fig. 1 Fig. Figure 1 is a schematic hardware diagram of a control device according to one embodiment. Fig. 2 Fig. Figure 2 is a schematic functional block diagram of a control device according to a first embodiment. Fig. 3 Fig. Figure 3 is a diagram showing an example of a frequency distribution of values ​​of the load applied to a spindle. Fig. 4 Fig. Figure 4 is a diagram showing an example of quantile calculation. Fig. 5 Fig. Figure 5 is a diagram showing another example of quantile calculation. Fig. 6 Fig. Figure 6 is a schematic functional block diagram of a control device according to a second embodiment. Fig. 7 Fig. Figure 7 is a diagram showing an example of a block diagram of a PID controller using conventional techniques. Description of embodiments

[0010] With reference to the figures, embodiments of the present invention will be described below.

[0011] Fig. Figure 1 is a schematic hardware diagram illustrating the main sections of a control device according to one embodiment of the present invention. The control device according to the present invention can, for example, be implemented as a control device that controls a machine tool.

[0012] A CPU 11 comprising the control device 1 according to the present invention is a processor that controls the control device 1 as a whole. The CPU 11 reads a system program stored in a ROM 12 via a bus 22 and controls the entire control device 1 according to this system program. Temporary calculation data and display data, various types of externally input data, and so on, are temporarily stored in a RAM 13.

[0013] A non-volatile memory 14, for example, consists of a memory device supported by a battery (not shown), an SSD (solid-state drive), or the like, whereby the memory state is retained even after the power to the control device 1 has been switched off. The non-volatile memory 14 stores data and processing programs read from an external device 72 via an interface 15, data and processing programs entered via an input device 71, various types of data obtained from machine tools, and so on. The data and processing programs stored in the non-volatile memory 14 can be loaded into RAM 13 at the time of execution / use. Furthermore, various types of system programs, such as known analysis programs, are pre-written in ROM 12.

[0014] Interface 15 connects the CPU 11 of the control device 1 to the external device 72, such as a USB device or similar. The external device 72 can read, for example, machining programs, various parameters, and so on, used for controlling the machine tool. Furthermore, machining programs, various parameters, and so on, processed in the control device 1 can be saved via the external device 72 to an external storage device (not shown).

[0015] A PLC (programmable logic controller) 16 outputs signals via an I / O unit 17 to the machine tool and its peripheral devices (e.g., tool changers, actuators such as robots or the like, sensors attached to the machine tool, and so on) and controls them, according to a sequence program implemented in the control device 1. In the control device 1 according to the present embodiment, for example, a sensor 3 is connected via the I / O unit 17, which measures a load exerted on a spindle during machining. Furthermore, signals from various types of switches on a control panel located on the main unit of an industrial machine, peripheral devices, and so on are received, subjected to the necessary signal processing, and then passed on to the CPU 11.

[0016] Various types of data read into memory, data obtained as a result of executing processing programs or system programs, and so on, are output via an interface 18 and displayed on a display device 70. Furthermore, the input device 71, consisting of a keyboard, a pointing device, and so on, transmits commands, data, and so on, based on actions performed by a worker, to the CPU 11 via an interface 19.

[0017] A shaft control circuit 30 for controlling a shaft with which the machine tool is equipped receives a control command value relating to the shaft from the CPU 11 and outputs this command to a servo amplifier 40. The servo amplifier 40 receives this command and drives a servo motor 50, which moves a drive section contained in the machine tool along the shaft. The servo motor 50 of the shaft has a built-in position / speed detector and receives feedback of position / speed signals from this position / speed detector to the shaft control circuit 30, thus performing position / speed feedback control. Although in the hardware setup diagram of Fig. Figure 1 shows only one shaft control circuit 30, one servo amplifier 40, and one servo motor 50. It should be noted that they are actually provided in a number corresponding to the number of shafts on the machine tool that is the target of the control. For example, in the case of controlling a general machine tool, three sets of shaft control circuit 30, servo amplifier 40, and servo motor 50 are provided, which move the spindle, to which a tool is attached, and the workpiece relative to each other in the directions of three linear axes (an X-axis, a Y-axis, and a Z-axis).

[0018] A spindle control circuit 60 receives a spindle rotation command and outputs a spindle speed signal to a spindle amplifier 61. The spindle amplifier 61 receives this spindle speed signal and rotates a spindle motor 62 of the machine tool at the commanded rotational speed, thereby driving the tool. A position encoder 63 is connected to the spindle motor 62, and the position encoder 63 outputs feedback pulses synchronously with the rotation of the spindle, with these feedback pulses being read by the CPU 11.

[0019] Fig. Figure 2 is a schematic block diagram illustrating the functions of the control device 1 according to a first embodiment of the present invention. The functions of the control device 1 according to the present embodiment are implemented by the CPU 11, with which the Fig. 1 is equipped with the control device 1 shown, executes a system program and controls the activities of the individual units of the control device 1.

[0020] The control device 1 according to the present embodiment comprises a control unit 110, a spindle load measuring unit 120, a spindle load recording unit 130, a target spindle load calculation unit 140, and a quantile specification unit 160. Furthermore, a machining program obtained from the input device 71, the external device 72, or the like is pre-stored in the RAM 13 or the non-volatile memory 14 of the control device 1. Additionally, a spindle load storage unit 220, which is an area for storing the measured spindle load, is pre-configured in the RAM 13 or the non-volatile memory 14 of the control device 1.

[0021] The control unit 110 is implemented by the CPU 11, with which the in Fig. The control device 1, as depicted, is equipped with a system program read from ROM 12. This program primarily performs computational processing using RAM 13 and non-volatile memory 14, and processes data for controlling the units of a machine tool 2 using the shaft control circuit 30, the spindle control circuit 60, and the PLC 16. The control unit 110 analyzes the machining program 210 and generates command data for controlling the machine tool 25 and peripheral devices such as the sensor 3, etc. The control unit 110 then controls the units of the machine tool 2 based on the generated command data. For example, based on commands to move the shafts of the machine tool 2, the control unit 110 generates data related to the movement of the shafts and outputs this data to the servo motor 50.Furthermore, the control unit 110, for example, generates data related to the rotation of the spindle of the machine tool based on a command to rotate the spindle and outputs it to the spindle motor 62. Additionally, the control unit 110 generates predefined data for operating the peripheral devices of the machine tool 2 based on commands to operate peripheral devices and outputs it to the PLC 16. Moreover, the control unit 110 receives the status (motor current value, position, speed, acceleration, torque, etc.) of the servo motor 50 and the spindle motor 62 as feedback values, which are used for the individual control processing operations.

[0022] The control unit 110, with which the control device 1 is equipped according to the present embodiment, controls the spindle feed rate (the relative feed rate between the spindle and the workpiece) when a target spindle load, specifying a target value for the spindle load, is input by the target spindle load calculation unit 140, such that the spindle load reaches the target spindle load. The control unit 110 also instructs the spindle load measuring unit 120 to start / stop the measurement of the load exerted on the spindle based on commands from blocks of the machining program 210, commands entered by an operator at the input device 71, and so on.

[0023] The spindle load measuring unit 120 is implemented by the CPU 11, with which the in Fig. The control device 1, as shown in Figure 1, executes a system program read from ROM 12 and performs arithmetic processing primarily by the CPU 11 using RAM 13 and non-volatile memory 14, and processes for controlling the units of the machine tool 2 using PLC 16. The spindle load measuring unit 120 instructs the sensor 3 to measure the load exerted on the spindle with which the machine tool is equipped and obtains its measurement results. The spindle load measuring unit 120 can obtain the load exerted on the spindle, for example, as a set (time series data) of values ​​measured over a specific cycle. The value of the load exerted on the spindle obtained by the spindle load measuring unit 120 can be expressed in a predetermined unit of load (Nm, etc.).The load may be expressed as a percentage of parts per hundred, etc., or as a ratio of the measured load (% of parts per hundred, etc.) to the continuous rated load of the motor for moving the spindle relative to the workpiece. The set of values ​​of the load exerted on the spindle obtained by the spindle load measuring unit 120 is output to the spindle load recording unit 130.

[0024] The spindle load recording unit 130 is implemented by the CPU 11, with which the in Fig. The control device 1 shown in Figure 1 executes a system program read from ROM 12, and computational processing is mainly carried out by the CPU 11 using RAM 13 and non-volatile memory 14. The spindle load recording unit 130 records the set of values ​​of the load applied to the spindle obtained by the spindle load measuring unit 120 in the spindle load storage unit 220. The spindle load recording unit 130 can record the set of values ​​of the load applied to the spindle obtained by the spindle load measuring unit 120 directly in the spindle load storage unit 220.Alternatively, the spindle load recording unit 130 can generate a frequency distribution of the load values ​​applied to the spindle based on the set of values ​​obtained from the spindle load measuring unit 120 and record the data relating to the generated frequency distribution in the spindle load storage unit 220. The spindle load recording unit 130 can also store the results of a simulation of the load applied to the spindle, performed using an average (not shown), in the spindle load storage unit 220.

[0025] When the set of values ​​of the load exerted on the spindle is recorded as data relating to a frequency distribution, predetermined classes are established by subdividing a range of values ​​that the load exerted on the spindle can assume. The spindle load recording unit 130 then calculates, for each of the above classes, the frequency with respect to each data element contained in the set of values ​​of the load exerted on the spindle obtained by the spindle load measurement unit 120, based on its load value, thereby generating the frequency distribution.

[0026] For example, if the values ​​of the load exerted on the spindle are expressed as a ratio to the continuous rated load of the motor, as described above, and the values ​​of the load exerted on the spindle can range from 0% to 150%, then the range of values ​​is divided into 151 classes, where, for instance, data with a load value of not less than 0% but less than 1% are considered 0%, data with a load value of not less than 1% but less than 2% are considered 1%, and so on. It is determined to which class each data element contained in the set of values ​​of the load exerted on the spindle obtained by the spindle load measuring unit 120 belongs, and the number of data elements belonging to each class is calculated as a frequency, thus generating the frequency distribution.

[0027] Fig. Figure 3 shows an example of generating a frequency distribution of the values ​​of the load exerted on the spindle using the spindle load recording unit 130. In the example of Fig. 3. The unit of measurement for the values ​​of the load applied to the spindle is expressed as the ratio with respect to the continuous nominal load range. It is further assumed that the spindle load measurement unit 120 measures the load applied to the spindle every 10 ms. It is also assumed that the range of values ​​of the load applied to the spindle, as described above, is divided into 151 classes at every 1%. Now, the spindle load measurement unit 120 determines to which class each of 10,001 data elements, acquired from a time of 0 ms to 100,000 ms, belongs and calculates the number of data points belonging to each class to generate the frequency distribution. Among the load value data obtained in Fig. As illustrated in the examples below, the frequencies in the load classes of 60% to 80% show a relatively high value, while the frequencies of the other classes are low.

[0028] The target spindle load calculation unit 140 is implemented by the CPU 11, with which the in Fig. The control device 1, as depicted in Figure 1, executes a system program read from ROM 12, and performs arithmetic operations primarily by the CPU 11 using RAM 13 and non-volatile memory 14. The target spindle load calculation unit 140 calculates a quantile specified by the quantile specification unit 160 in the data stored in the spindle load memory unit 220 as the target spindle load. If a set of values ​​of the load applied to the spindle is stored as data in the spindle load memory unit 220, the target spindle load calculation unit 140 can rearrange the individual data elements in ascending or reverse order, calculate the cumulative frequency from the bottom up, and then calculate the quantile corresponding to the specified quantile.Even if the frequency distribution of the values ​​of the load exerted on the spindle is stored as data in the spindle load storage unit 220, the target spindle load calculation unit 140 can calculate the cumulative frequency for each class from the bottom up and calculate the quantile corresponding to the specified quantile. The target spindle load calculation unit 140 outputs the calculated quantile as the target spindle load to the control unit 110.

[0029] Fig. 4 is a diagram showing a procedure to derive the frequency distribution from the data in Fig. Figure 3 illustrates how to find the ½ quantile. As in Fig. As illustrated in Figure 4, if, for example, the ½ quantile has been specified beforehand, the cumulative frequency is calculated from the bottom up based on the data in the frequency distribution, and the value indicating the class containing the 5001st data element is calculated as the ½ quantile. In the case of Fig. 4 outputs the target spindle load calculation unit 140 74%, which is the ½ quantile, as the target spindle load to the control unit 110.

[0030] The control device 1 according to the present embodiment can regulate the target spindle load by changing the specified quantile depending on the machining objective. Fig. Figure 5 shows an example of the calculation of the target spindle load in a case where the operator has specified the 1 / 4 quantile or the 3 / 4 quantile. For example, in a case where cycle time is to be sacrificed to extend tool life, the operator instructs the target spindle load calculation unit, via input unit 71 or the like, to calculate the 1 / 4 quantile as the target spindle load. In this case, the target spindle load calculation unit 140 calculates the value of the class that contains the 2500th and 2501st data elements from the bottom in the set of values ​​of the load applied to the spindle as the 1 / 4 quantile. In the example of Fig. 5 outputs the target spindle load calculation unit 140 58%, which is the 1 / 4 quantile, as the target spindle load to the control unit 110. Conversely, if tool life is to be sacrificed to speed up the cycle time, the operator of the target spindle load calculation unit 140 commands, via input unit 71 or the like, to calculate the 3 / 4 quantile as the target spindle load. In this case, the target spindle load calculation unit 140 calculates the value of the class that contains the 7500th and 7501st data elements from the bottom in the set of values ​​of the load exerted on the spindle as the 3 / 4 quantile. In the example of Fig. Unit 5 outputs the target spindle load calculation unit 140 80%, which is the ¾ quantile, as the target spindle load to the control unit 110. It should be noted that if the specified quantile spans classes, the average of the values ​​corresponding to those classes can be used as the target spindle load.

[0031] The quantile specification unit 160 is implemented by the CPU 11, with which the in Fig. The control device 1, as depicted, is equipped with a system program read from the ROM 12. Computational processing is primarily performed by the CPU 11 using the RAM 13 and the non-volatile memory 14, and input processing is performed using the interface 19. The quantile specification unit 160 receives input from the operator to specify the quantile and outputs it to the target spindle load calculation unit 140. The quantile specification unit 160 can receive a direct input to specify the quantile, such as the ½ quantile, the ¾ quantile, and so on, or it can receive a specifying input in the form of a percentile, such as 30%, 50%, 70%, or the like.In addition to receiving a specification of the quantile from the input device 71, a quantile that is set in a setting range provided in the non-volatile memory 14 of the control device 1 can also be received as the specified quantile, or a quantile that has been received via a network not shown from another computer such as a host computer or the like can be received as the specified quantile.

[0032] When the control device 1 according to the present embodiment is used with the setup described above, the operator measures the load exerted on the spindle while performing a trial machining operation. Simply specifying a predetermined quantile with respect to the set of load values ​​obtained through the measurement then automatically sets the target spindle load. Enabling the specification of a quantile with respect to values ​​of the load exerted on the spindle, as described above, facilitates the extraction of a value measured a large number of times from the loads exerted on the spindle during the trial machining operation.The load exerted on the spindle is not constant, even when the workpiece is machined at the same spindle speed, feed rate, and cutting depth, due to spindle vibrations, the way the cutting edge contacts the workpiece, and other factors. Consequently, it is difficult to identify a section with stable machining using only a mode value or similar method. Control device 1, according to the present embodiment, allows the specification of distributions with respect to a set of measured values ​​of the load exerted on the spindle, thus facilitating the identification of a section with stable machining where load values ​​are concentrated with a relatively high frequency.Then, using this section with a stable machining process as a reference, predetermined distributions can be specified, making it easy to determine a specification depending on the goal of the machining, such as machining with a focus on cycle time or machining with a focus on tool life.

[0033] In the control device 1 according to the present embodiment, the set of values ​​of the load exerted on the spindle can be stored as is in the spindle load storage unit 220. However, storing this data as frequency distribution data significantly reduces the required data storage capacity compared to recording the set of values ​​of the load exerted on the spindle obtained by the spindle load measuring unit 120 as is. Furthermore, calculating the frequency distribution in advance simplifies the calculation at the time of performance with regard to quantiles.

[0034] As a modification of the control device 1 according to the present embodiment, the quantile specification unit 160 can be configured by the operator using option fields, pull-down menus, or the like, with regard to the specification of quantiles. For example, a menu including "Cycle time priority," "Equilibrium priority," "Tool life priority," and so on, can be selected, and a quantile corresponding to the selected item can be specified by choosing that item. By providing such a configuration, the operator can easily specify a predetermined quantile by defining their intention.

[0035] Fig. Figure 6 is a schematic block diagram illustrating the functions of the control device 1 according to a second embodiment of the present invention. The functions of the control device 1 according to the present embodiment are implemented by the CPU 11, with which the Fig. 1 is equipped with the control device 1 shown, executes a system program and controls the activities of the individual units of the control device 1.

[0036] The control device 1 according to the present embodiment comprises, in addition to the control unit 110, the spindle load measuring unit 120, the spindle load recording unit 130, and the target spindle load calculation unit 140, a spindle operating state determination unit 150. Furthermore, the machining program 210, which was obtained from the input device 71, the external device, or the like, is pre-stored in the RAM 13 or the non-volatile memory 14 of the control device 1. Additionally, a spindle load storage unit 220, which is an area for storing the measured spindle load, is pre-configured in the RAM 13 or the non-volatile memory 14 of the control device 1.

[0037] The control unit 110, the spindle load measuring unit 120 and the spindle load recording unit 130, which the control device 1 has according to the present embodiment, have the same functions as the functions that the control device 1 has according to the first embodiment.

[0038] The spindle operating state determination unit 150 is implemented by using the CPU 11, with which the in Fig.The control device 1 shown in Figure 1 executes a system program read from ROM 12, and computational processing is primarily performed by the CPU 11 using RAM 13 and non-volatile memory 14. The spindle operating state determination unit 150 determines the operating state of the spindle, such as whether it is accelerating / decelerating or stopped, based on information obtained from the control unit 110, and instructs the spindle load recording unit 130 not to record the spindle load measured while it is accelerating / decelerating or stopped. Whether the spindle is accelerating / decelerating or stopped can be determined from the state of the execution of the machining program 210 by the control unit 110.For example, the spindle's rotation speed may accelerate or decelerate immediately after executing a normal rotation command (a reverse rotation command), a stop command, a speed command, or the like, and the spindle's rotation speed may change. This can cause a high load on the spindle, even in a state where no machining is taking place. In such a state, it can be determined that the spindle is accelerating / decelerating. Similarly, if a sufficient amount of time has elapsed after executing a stop command, it can be determined that the spindle is stopped.

[0039] Including the value of the load exerted on the spindle, measured during acceleration / deceleration or standstill, in the calculation of the target spindle load leads to a high or low target spindle load. The control device 1 according to the present embodiment with the above setup can exclude the load exerted on the spindle when the spindle is accelerating / decelerating or stopped from the calculation of the target spindle load, thereby expected to determine a more appropriate target spindle load.

[0040] Although embodiments of the present invention have been described above, the present invention is not limited to the examples of the embodiments described above, but can be implemented in various ways by appropriately applying different modifications. REFERENCE MARK LIST 1 Control device 2 machine tools 3 Sensor 11 CPU 12 ROM 13 RAM 14 non-volatile memory 15, 18, 19 interface 16 PLC 17 I / O units 22 Bus 30 shaft control circuit 40 servo amplifiers 50 servo motor 60 Spindle control circuit 61 Spindle amplifiers 62 Spindle motor 63 position encoders 70 Display device 71 Input device 72 external institution 110 Control unit 120 Spindle load measuring unit 130 Spindle load recording unit 140 Target spindle load calculation unit 150 Spindle operating condition determination unit 160 quantile specification unit 210 Editing program 220 spindle load storage unit

Claims

[1] A control device (1) which regulates a feed rate on the basis of a load applied to a spindle during machining of a workpiece, the control device (1) comprising: a spindle load storage unit (220) that stores data relating to the load applied to the spindle; a quantile specification unit (160) that specifies a predetermined quantile; a target spindle load calculation unit (140) that calculates the quantile specified by the quantile specification unit (160) in the data relating to the load applied to the spindle stored in the spindle load storage unit (220) as the target spindle load; a spindle load measuring unit (120) that measures the load exerted on the spindle; and a control unit (110) which controls the feed rate of the spindle with respect to the workpiece so that the load exerted on the spindle becomes the target spindle load, has. [2] The control device (1) according to claim 1, wherein the target spindle load calculation unit (140) calculates the target spindle load based on a cumulative frequency calculated by accumulating the frequencies of the values ​​of the load applied to the spindle stored in the spindle load storage unit (220) in an order from low values, and the quantile specified by the quantile specification unit (160). [3] The control device (1) according to claim 1, further comprising a spindle load recording unit (130) which divides values ​​that the load exerted on the spindle can assume into a plurality of classes, calculates a frequency distribution for which the loads measured by the spindle load measuring unit (120) were counted as corresponding to the respective classes, and records them in the spindle load storage unit (220). [4] The control device (1) according to claim 1, further comprising a spindle operating state determining unit (150) that instructs the spindle load storing unit (220) not to store the load applied to the spindle when the spindle is accelerated / decelerated or stopped. [5] The control device (1) according to claim 1, wherein the quantile specification unit (160) determines a quantile to be specified based on the selection of an option indicating a target related to the processing.

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