JP7707095B2 - Processing device and control method thereof - Google Patents

Description

The present invention relates to a processing device that moves a table on which a workpiece is placed relative to a spindle that holds a tool such as a drill, and processes the workpiece with the tool, and in particular to a technology for automatic warm-up operation after the device is started.

In accordance with a program, the processing device moves a table on which a workpiece is placed in the X direction and moves a spindle holding a tool such as a drill in the Y direction to relatively position the tool, then lowers the spindle in the Z direction and rotates the tool to perform processing such as drilling. Here, the table and spindle are moved by engaging a ball screw with a nut or the like attached to them, and the ball screw is rotated and driven by a servo motor, but it is known that the temperature of each part of the device rises due to frictional heat at the parts where the ball screw slides against the nut and bearings, and the rotational heat of the motor itself, and that thermal deformation of these parts causes deviations in the machine positioning precision.

This deviation stabilizes when each part of the device is thermally saturated, so conventionally, the device is warmed up for a predetermined time after startup to thermally saturate each part and stabilize the deviation in positional accuracy before starting processing. Here, since it is believed that the amount of temperature drop after the device is stopped depends on the time the device is stopped and the rate of temperature increase after startup depends on the operating time, a technique is known in which the device's stopped time is measured and the warm-up operation is automatically performed for a predetermined time based on the stopped time, as disclosed in Patent Document 1, for example. There is also a technique in which a sensor is actually installed near a heat source such as the device's moving mechanism to measure the temperature and the warm-up operation is automatically performed until each part reaches a temperature at which it is thermally saturated.

Japanese Patent Application Publication No. 5-228792

However, when warming up is performed only for a period based on the equipment downtime, the rate of temperature rise after the equipment is started up can vary depending on factors such as equipment aging and the accumulation of dirt, so there are cases where appropriate warming up is not always possible. In such cases, if the warming up is insufficient, the processing precision is unstable and product yields decrease. Furthermore, if the warming up is excessive, there are times when processing is not performed even though processing can be performed with high precision, resulting in a problem of reduced production efficiency.

In addition, when measuring the temperature of each part near the heat source to terminate the warm-up operation, it is necessary to add a temperature sensor that is not actually necessary for the processing device, which makes the device configuration complicated and increases costs.

The present invention aims to provide a processing device that can detect the timing when warm-up operation is no longer necessary after the start of warm-up operation based on the state of the processing device using a method other than a temperature sensor, and can end the warm-up operation just right and resume processing quickly.

The inventors have discovered that the torque value of a servo motor is large when the temperature of the processing equipment is low (when not thermally saturated), decreases as the temperature increases, and becomes constant when the equipment is thermally saturated. This is thought to be because the grease applied to the servo motor itself and to the parts where the ball screw connected to the servo motor comes into sliding contact with the nut and bearings, has a high viscosity at low temperatures and becomes softer as the temperature increases, causing the load on the servo motor to fluctuate. In other words, when the grease is hard, the grease itself acts as a resistance when rotating the servo motor, and the torque value of each servo motor increases, but as the grease becomes softer, the resistance decreases and the torque value of each servo motor also decreases.

Based on the above findings, in order to solve the above problems, the present invention provides a processing device that performs processing by moving a spindle that holds a tool and a table on which a workpiece is placed and fixed relative to each other by rotating a ball screw driven by a servo motor according to a processing program, and is characterized in that the processing device starts a warm-up operation before processing the workpiece based on the processing program, and is equipped with a torque detection unit that detects the torque value of the servo motor, and a warm-up completion judgment unit that judges the completion of the warm-up operation using the torque value detected by the torque detection unit.

According to the present invention, it is possible to determine whether the processing equipment is thermally saturated based on the actual state of the processing equipment, and it is possible to perform warm-up operation without excessive or insufficient operation while reducing the complexity of the equipment.

1 is a configuration diagram of a drilling device according to an embodiment of the present invention; FIG. 4 is a flow chart illustrating the operation of the drilling device according to one embodiment of the present invention.

Below, a representative embodiment of the present invention will be described with reference to the drawings. Note that in each figure, the components shown are those that are considered to be necessary mainly for explaining this embodiment, and do not show all the components necessary for the processing device.

Figure 1 is a diagram showing the configuration of a drilling device according to an embodiment of the present invention. The configuration of a drilling device 20 according to an embodiment of the present invention will be described with reference to Figure 1. Gate-shaped columns 2 are fixed to both sides of a bed 1, and a table 4 on which a workpiece 3 is placed and fixed is provided on the upper surface of the bed 1 so as to be movable back and forth in the depth direction of the bed 1 (depth direction in the figure, X-axis direction) along a pair of guides 5. A nut that engages with a ball screw (not shown) is fixed to the underside of the table 4, and the ball screw is rotated by a servo motor 6 (hereinafter also referred to as the "X-axis drive servo motor") to move the table 4 in the X-axis direction.

A pair of guides 7 are provided in parallel with the surface of the table 4 on the front side of the horizontal part of the column 2, and the slider 8 is supported by the guides 7 so as to be movable. A nut (not shown) that engages with the ball screw 9 is fixed to the rear side of the slider 8. The ball screw 9 is rotated by a servo motor 10 (hereinafter also referred to as the "servo motor for driving the Y axis"), so that the slider 8 moves in the horizontal direction (left-right direction in the figure, the Y axis direction) along the guide 7. A pair of guides 11 are provided in the vertical direction (up-down direction in the figure, the Z axis direction) on the front side of the slider 8, and the base 12 is supported so as to be movable along the guides 11. A nut (not shown) that engages with the ball screw 13 is fixed to the rear side of the base 12, and the ball screw 13 is rotated by a servo motor 14 (hereinafter also referred to as the "servo motor for driving the Z axis"), so that the base 12 moves in the Z axis direction.

A saddle 16 that supports a spindle 15 is fixed to the base 12. A collet chuck 17 is attached to the lower end of the spindle 15, and a tool, a drill 18, is removably held by the collet chuck 17 at a position facing the workpiece 3. Inside the spindle 15, a servo motor (not shown in the figure) (hereinafter also referred to as a "spindle drive servo motor") rotates, causing the drill 18 to rotate. Each servo motor is equipped with an encoder that detects the rotation angle, rotation speed, etc.

The overall control device 30 controls each part of the drilling device 20, and includes an X-axis drive servo motor control unit 31, a Y-axis drive servo motor control unit 32, a Z-axis drive servo motor control unit 33, a spindle drive servo motor control unit 34, a torque detection unit 35, and a warm-up completion determination unit 36.

The X-axis drive servo motor control unit 31, the Y-axis drive servo motor control unit 32, the Z-axis drive servo motor control unit 33, and the spindle drive servo motor control unit 34 are connected to the respective servo amplifiers and servo motors (not shown), and drive and control each servo motor.

The overall control device 30 generates a position command according to the contents of the program and outputs it to each servo motor control unit. Each servo motor control unit generates a torque command based on the input position command and position feedback sent from the encoder provided in the servo motor, and outputs it to each servo amplifier. Each servo amplifier generates a current command based on the torque command and supplies a current according to this to rotate and drive each servo motor. In this way, the rotation of the drill or ball screw is controlled according to the program and machining is performed. The method of driving and controlling the above servo motors is similar to the commonly known method.

The torque detection unit 35 detects the torque command output from each servo motor control unit to each servo amplifier at each sampling interval defined as a torque value.

The warm-up completion determination unit 36 determines whether the torque value of each servo motor detected by the torque detection unit 35 is equal to or lower than the respective threshold value stored in advance, and determines that the device is thermally saturated and the warm-up is complete when the torque values of all servo motors are equal to or lower than the respective threshold value. Note that the threshold torque value differs for each servo motor, so it is determined in advance for each before using the device.

The overall control device 30 is equipped with a CPU and memory (not shown), and the CPU includes a control unit and a calculation unit, with the control unit interpreting commands and controlling the flow of program control, and the calculation unit executing the calculations. The program is stored in a memory (not shown), and the command to be executed (a certain number or sequence of numbers) is retrieved from the memory in which the program is placed, and the program is executed. Furthermore, the overall control device 30 has control functions other than those described here, and is also connected to blocks (not shown). Some of the components may be provided separately from the overall control device 30.

Next, the method of using and operation of the drilling device 20 using the present invention will be described. Prior to using the drilling device 20, a trial warm-up operation is first performed as preparation for use to obtain the torque values of each servo motor when the drilling device 20 is thermally saturated. The torque value of each servo motor decreases after the warm-up operation begins, and eventually stops decreasing and becomes a constant value. This value is stored as a threshold value in a memory unit (not shown) of the overall control device 30. During the trial warm-up operation, a workpiece is not actually machined, so a warm-up operation program that has been created in advance and stored in the overall control device 30 is used instead of a machining program.

Figure 2 is a flowchart that explains an example of the operation of the drilling device 20, which is one embodiment of the present invention. The operation of the drilling device 20 after a trial warm-up operation has been performed, the torque thresholds of each servo motor have been stored in the overall control device 30, and the device is ready for use will be explained according to the flowchart shown in Figure 2.

First, the operator saves the previously created machining program in the memory unit (not shown) of the overall control device 30 (step 1). Next, the workpiece 3 is placed and fixed on the table 4 (step 2). After that, the operator instructs the overall control device 30 to start machining through an input device (not shown) (step 3). When the overall control device 30 receives the machining start instruction, it reads out the warm-up operation program previously stored in the memory unit, drives each servo motor according to the program, and starts the warm-up operation (step 4). During the warm-up operation, the torque detection unit 35 detects the torque value of each servo motor at a predetermined sampling interval and transmits it to the warm-up completion judgment unit 36 (step 5). The warm-up completion judgment unit 36 judges whether the received torque value of each servo motor is equal to or less than the respective threshold value (step 6). If the torque values of all the servo motors are equal to or less than the respective threshold value (YES in step 6), the overall control device 30 ends the control by the warm-up operation program, reads out the machining program stored in step 1, and drives and controls each servo motor to machine the workpiece according to the program (step 7). If the torque value of any of the servo motors exceeds the threshold value (NO in step 6), the process returns to step 5, and the torque detection unit 35 continues to detect the torque value of each servo motor at each predetermined sampling interval while continuing the warm-up operation.

When the warm-up completion determination unit 36 determines that the warm-up operation is complete (the processing device 60 is thermally saturated) (YES in step 6 of FIG. 2), a notification may be sent to the operator (for example, by turning on a lamp or sounding a buzzer) via an output device (not shown). The time required for warm-up operation varies depending on the state of the device, but may take several hours. Therefore, if the operator is notified that the warm-up operation is complete and actual processing has begun, the operator can perform other tasks until the warm-up operation is complete.

In this embodiment, the X-axis, Y-axis, Z-axis, and spindle are all driven by servo motors, but the present invention is not limited to this, and some of the drives may be driven by something other than servo motors. In this case, the thermal saturation state is judged by torque for parts using servo motors, and for parts driven by other than servo motors, a temperature sensor is provided as in the past to judge the thermal saturation state. In this case, in order to judge the thermal saturation state of parts driven by other than servo motors, the temperature of the saturated state is stored in advance as a threshold value. Then, the warm-up completion judgment unit may judge that the parts are thermally saturated when the temperature detected by the temperature sensor is equal to or higher than the threshold value and all the torques detected by each servo motor are equal to or lower than the threshold value. In this way, even if a temperature sensor is used for a drive part other than the servo motor, the axis driven by the servo motor can be judged without providing a temperature sensor, so that the complexity of the device configuration can be reduced and costs can be reduced.

In addition, in this embodiment, the warm-up operation is performed after the device is started, but the warm-up operation may also be performed when starting actual processing after a certain period of time has elapsed in a standby state in which no actual processing is performed after the device is started.

Furthermore, in this embodiment, a processing device using a drill as a tool has been described, but the present invention is not limited to this, and may be a processing device using, for example, an end mill.

In addition, as the device continues to be used, the thresholds in a thermally saturated state may change due to aging or the accumulation of dirt, so each threshold may be updated each time the device is used for a specified period of time or each time it is started up a specified number of times.

Furthermore, each threshold value may be updated each time actual machining by the machining program is completed. In this way, each time the machining device is started, it is possible to determine whether warm-up is complete based on the torque threshold value that reflects the device's status immediately before starting, and it is possible to further optimize the warm-up operation time.

As described above, according to the present invention, it is possible to detect that the processing device has become thermally saturated and terminate the warm-up operation based on the torque value of the servo motor that constitutes the processing device. In other words, it is possible to determine whether the processing device has become thermally saturated using a torque value that can be detected by the control unit of the servo motor that is essentially required by the processing device, rather than a mechanism that is essentially unnecessary for the processing device, such as a temperature sensor, thereby avoiding or reducing the complexity of the device and further reducing costs.

3: Workpiece 9, 13: Ball screws 6, 10, 14: Servo motor 15: Spindle 18: Drill 20: Drilling device 30: Overall control device 31: X-axis drive servo motor control unit 32: Y-axis drive servo motor control unit 33: Z-axis drive servo motor control unit 34: Spindle drive servo motor control unit 35: Torque detection unit 36: Warm-up completion determination unit

Claims (10)

A processing device that performs processing by relatively moving a spindle holding a tool and a table on which a workpiece is placed and fixed by rotating a plurality of ball screws driven by a plurality of servo motors in accordance with a processing program, the processing device starting a warm-up operation before processing the workpiece based on the processing program,
a torque detection unit for detecting a plurality of torque values in the plurality of servo motors;
a warm-up completion determination unit that determines that the warm-up operation is completed when a plurality of torque values detected by the torque detection unit become equal to or less than a plurality of threshold values respectively determined for the plurality of servo motors. performing a test warm-up operation based on a warm-up operation program, detecting during the test warm-up operation that the torque values have stopped decreasing and become constant values, and defining the constant values as the threshold values;
performing the trial warm-up operation each time a predetermined time has elapsed since the time the processing device was used, or each time the number of startups exceeds a predetermined number, or each time actual processing according to the processing program is completed, and updating the plurality of threshold values;
2. The processing apparatus according to claim 1 . The spindle is rotated by a servo motor,
2. The processing device according to claim 1, wherein the warm-up completion determination unit determines that the warm-up operation is completed when torque values of all the servo motors detected by the torque detection units become equal to or less than a threshold value. a temperature sensor for measuring a temperature of the spindle;
The processing apparatus according to claim 1, characterized in that the warm-up completion determination unit determines that the warm-up operation is completed when the torque values of all servo motors detected by the torque detection unit become equal to or lower than a threshold value and the temperature detected by the temperature sensor becomes equal to or higher than a threshold value. 5. The processing device according to claim 1 , wherein when the warm-up completion determination unit determines that the warm-up operation is completed, the warm-up operation is terminated and processing based on the processing program is started. A control method for a processing device which performs processing by relatively moving a spindle holding a tool and a table on which a workpiece is placed and fixed by rotating a plurality of ball screws driven by a plurality of servo motors in accordance with a processing program, the control method comprising the steps of:
a torque detection step of detecting a plurality of torque values in the plurality of servo motors;
a warm-up completion determination step of determining completion of the warm-up operation when a plurality of torque values detected in the torque detection step become equal to or less than a plurality of threshold values respectively determined for the plurality of servo motors . a threshold setting step of performing a test warm-up operation based on a warm-up operation program, detecting during the test warm-up operation that the torque values have stopped decreasing and become constant values, and setting the constant values as the threshold values;
and a threshold updating step of performing the threshold setting step and updating the plurality of thresholds each time a predetermined time has elapsed since the time when the processing device has been in use, or each time the number of times the processing device has been started exceeds a predetermined number of times, or each time actual processing according to the processing program is completed.
7. The control method according to claim 6. The spindle is rotated by a servo motor;
7. The control method according to claim 6, wherein in the warm-up completion determining step, it is determined that the warm-up operation is completed when the torque values of all the servo motors detected in the torque detecting step become equal to or less than a threshold value. a temperature measuring step of measuring a temperature of the spindle;
7. The control method according to claim 6, wherein in the warm-up completion determination step, it is determined that the warm-up operation is completed when the torque values of all the servo motors detected in the torque detection step are equal to or less than a threshold value and the temperature detected in the temperature measurement step is equal to or greater than a threshold value. The control method according to any one of claims 6 to 9 , characterized in that, when it is determined in the warm-up completion determination step that the warm-up operation is completed, the warm-up operation is terminated and machining based on the machining program is started.

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