Numerical control device

Abstract

Numerical control device (1) of a drilling machine for performing a feed operation while rotating a spindle, suspending the feed operation of the spindle for a predetermined dwell time at a predetermined hole base position and then performing a drilling operation by retracting the spindle, the numerical control device comprising: - a dwell time calculation unit (111) for calculating the dwell time based on a prescribed rotation amount in response to the specification of the prescribed rotation amount at the bore bottom position, - wherein the prescribed amount of rotation is set based on the number of blades of the tool (2) to ensure that the uncut portions within the bore are eliminated at the base position of the workpiece.

Description

Background of the invention 1. Field of the invention

[0001] The application relates to a numerical control device and, in particular, to a numerical control device that optimizes dwell time at the bottom of a bore. 2. Description of the related prior art

[0002] Fig. Figure 1 is an illustration describing a machining process called dwell.

[0003] When drilling, as in Fig. 1, a tool 2 is moved to a workpiece 3 by rapid traverse to a point R, and cutting feed is started at the point R (1). In response to a distal end of the tool 2 arriving at a hole bottom (point Z) (2), the cutting feed is suspended for a predetermined period of time while maintaining the rotation of a spindle (not shown) to improve machining accuracy at the hole bottom (so as not to leave an uncut portion) (3). Thereafter, the tool 2 is retracted (4). A suspension time at point (3) is called a dwell time.

[0004] If the dwell time at the hole bottom is insufficient, the machining accuracy at the hole bottom will deteriorate. Specifically, an uncut portion, insufficient hole depth, etc. will be generated. For example, if the tool 2 has two blades, an uncut portion may be generated unless the blades are rotated by 1 / 2 a turn or more. If the tool 2 has three blades, an uncut portion may be generated unless the blades are rotated by 1 / 3 a turn or more. Meanwhile, if the dwell time at the hole bottom is excessively long, a cycle time will be prolonged.

[0005] Conventionally, when commanding a dwell time based on the spindle speed, an operator can obtain a time T per revolution of a spindle and command the dwell time at the bottom of the hole, where the dwell time is obtained by multiplying a prescribed rotation amount by the time T. However, since the dwell time varies depending on the spindle speed, this method requires time and effort in programming the machining process. Therefore, a uniform dwell time can be commanded. However, it is difficult to minimize the cycle time.

[0006] Furthermore, in actual machining, due to the influence of a delay at a machine position (hereinafter referred to as machine delay) with respect to a command value, a dwell time may be started before the tool reaches the hole bottom. As a result, the dwell time at the hole bottom is shorter than the commanded dwell time, and an uncut portion, insufficient hole depth, etc. may be generated. For this reason, it is necessary to determine an appropriate value of the commanded dwell time through trial and error, which is troublesome.

[0007] Japanese Patent Application Laid-Open No. JP 2004-001120 A and Japanese Patent Application Laid-Open No. JP 2015-005108 A are known as conventional drilling-related technologies. Both of these documents describe that, during drilling, when the tool reaches a hole root position, the spindle is decelerated and stopped, and a direction of movement is reversed to retract the tool.

[0008] However, neither Japanese Patent Application Laid-Open No. JP 2004-001120 A nor Japanese Patent Application Laid-Open No. JP 2015-005108 A provide means for solving the problem that it is difficult to instruct an optimal residence time.

[0009] DE 101 09 990 B4 discloses a method for producing bores, particularly in long-chipping materials and with large recess depths, using a rotary-driven drilling tool on CNC-controlled machines. This method is characterized in that the tool feed is interrupted in alternating repetitions during the drilling process, with this process being repeated until the recess depth to be created is reached. The tool feed to the feed interruption occurs at a ratio of approximately 2:1, i.e., two tool revolutions with feed followed by approximately one tool revolution without feed.

[0010] DE 10 2014 008 658 B4 describes a numerical control with a feed shaft, which enables an increased production speed of a turning tool connected to the feed shaft. Summary of the invention

[0011] In response to the above problem, an object of the present invention is to provide a numerical control device that optimizes bottom hole dwell.

[0012] The object is achieved by a numerical control device having the features of patent claim 1. A numerical control device according to the application is a numerical control device of a drilling machine for performing a feed operation while rotating a spindle, suspending the feed operation of the spindle for a predetermined dwell time at a predetermined hole root position, and then performing a drilling operation by retracting the spindle, wherein the numerical control device comprises a dwell time calculation unit for calculating the dwell time based on a prescribed rotation amount in response to the specification of the prescribed rotation amount at the hole root position.

[0013] The dwell time calculation unit may add a time period corresponding to a delay at a tool position with respect to a command to the dwell time.

[0014] The prescribed amount of rotation can be specified by a program command or a parameter.

[0015] The present invention can provide a numerical control device that optimizes bottom hole dwell by the configurations described above. Brief description of the drawings Fig. 1 is a diagram describing a conventional drilling process; Fig. 2 is a diagram showing a hardware configuration example of a numerical control device; Fig. 3 is a diagram showing an example of a functional configuration of the numerical control device; Fig. 4 is an example of a diagram showing an operation of the numerical control device; Fig. Fig. 5 is an example of a diagram showing an operation of the numerical control device; and Fig. 6 is a diagram showing an operation example of the numerical control device. Detailed description of the preferred embodiments

[0016] Fig. 2 is a schematic hardware configuration diagram showing a main part of a numerical control device 1 according to an embodiment of the application.

[0017] The numerical control device 1 is a device that controls an industrial machine that performs a drilling operation. The numerical control device 1 includes a central processing unit (CPU) 11, a read-only memory (ROM) 12, a random access memory (RAM) 13, a non-volatile memory 14, a bus 10, an axis control circuit 16, a servo amplifier 17, and an interface 18. A servo motor 50 and an input / output device 60 are connected to the numerical control device 1.

[0018] The CPU 11 is a processor that controls the numerical control device 1 as a whole. The CPU 11 reads a system program stored in the ROM 12 via the bus 10 and controls the entire numerical control device 1 according to the system program.

[0019] For example, a system program for executing various control functions on a machine is stored in advance in ROM 12. Temporary calculation data or display data, data and programs entered by an operator via the input / output device, etc., are temporarily stored in RAM 13.

[0020] The non-volatile memory 14 is backed up, for example, by a battery (not shown), and maintains a stored state even when the power supply to the numerical control device 1 is turned off. Data and programs input via the input / output device 60 are stored in the non-volatile memory 14. The programs and data stored in the non-volatile memory 14 can be loaded into the RAM 13 when they are executed and used.

[0021] The axis control circuit 16 controls the machine's motion axes. The axis control circuit 16 receives an axis motion command amount issued by the CPU 11 and outputs a motion axis motion command to the servo amplifier 17. The servo amplifier 17 receives the axis motion command issued by the axis control circuit 16 and drives the servo motor 50.

[0022] The servo motor 50 is driven by the servo amplifier 17 to move the machine's motion axes. In the present embodiment, the spindle movement is performed by the servo motor 50. The servo motor 50 typically includes a position / speed detector. The position / speed detector outputs a position / speed feedback signal, which is fed back to the axis control circuit 16 to perform position / speed feedback control.

[0023] In Fig. 2, only a single axis control circuit 16, a single servo amplifier 17, and a single servo motor 50 are shown. In practice, however, the servo amplifiers, servo motors, and axis control circuits are each provided according to the number of axes included in the machine to be controlled.

[0024] The input / output device 60 is a data input / output device that includes a display, hardware keys, etc., and is typically a manual data input (MDI) device or a control panel. The input / output device 60 displays information received from the CPU 11 via the interface 18 on a display. The input / output device 60 forwards commands, data, etc., entered via the hardware keys, etc., to the CPU 11 via the interface 18.

[0025] Fig. 3 is a block diagram showing a characteristic functional configuration of the numerical control device 1.

[0026] The numerical control device 1 includes a preprocessing unit 101 that reads and analyzes a machining program, an interpolation motion command distribution processing unit 103 that generates an interpolation motion command and distributes the generated interpolation motion command to each axis, a motion command output unit 105 that outputs a motion command to each axis, an acceleration / deceleration processing unit 107 that performs acceleration / deceleration after interpolation, and a servo control unit 109 that controls the servo motor 50. Furthermore, the numerical control device 1 includes a dwell time calculation unit 111 that calculates an appropriate dwell time as an application-specific component.

[0027] A typical operation of the numerical control device 1 is described with reference to Fig. 4 described.

[0028] In a conventional numerical control device, it is necessary to specify a dwell time in the machining program. However, the numerical control device 1 according to the present embodiment can specify a dwell rotation amount (hereinafter also referred to as a prescribed rotation amount) in the machining program. In this case, the preprocessing unit 101 acquires the prescribed rotation amount. Alternatively, the numerical control device 1 can store any prescribed rotation amount as a parameter.

[0029] The interpolation motion command distribution processing unit 103, the motion command output unit 105, the acceleration / deceleration processing unit 107, and the servo control unit 109 move the tool to a point R on the workpiece 3 through a rapid traverse and start the cutting feed at point R according to the machining program analyzed by the preprocessing unit 101 (1). Then, in response to a distal end of the tool arriving at the hole bottom (point Z), a dwell is started (2). As shown in Fig. However, as shown in Figure 5, a position where dwelling is started (actual hole bottom) is located before a commanded hole bottom position (commanded hole bottom) due to machine deceleration. When the tool enters an in-position area of ​​the actual hole bottom, the dwell time calculation unit 111 calculates the dwell time in the following manner.

[0030] The dwell time calculation unit 111 calculates the dwell time so that the rotation amount of the spindle reaches a prescribed number. Specifically, a time period per rotation of the spindle is obtained from a spindle speed, where time period × prescribed rotation amount is defined as the dwell time. The spindle speed can be specified based on a spindle rotation command. Furthermore, the dwell time calculation unit 111 adds a time period required for the tool to arrive from the actual hole bottom to the commanded hole bottom—that is, a machine delay time—to the dwell time. In other words, in this example, the execution of a subsequent move command is waited until the delay time has elapsed.

[0031] After executing the dwell according to the dwell time calculated as described above, the process proceeds to the subsequent movement command (3), and the tool is retracted (4). Consequently, since the dwell is executed at the specified rotation amount after the tool has reached the commanded hole bottom, it is possible to perform the drilling operation with the shortest cycle time while maintaining machining accuracy.

[0032] An example of the application is shown with reference to Fig. 6 described.

[0033] In this example, a command can be used in the machining program according to the following command format. Unlike the conventional command format, this command format allows a dwell rotation amount (prescribed rotation amount) to be specified. Command format example: G82 Z_R_F_P_ Z: Hole bottom R: Reference point F: Cutting feed rate P: Dwell rotation amount (prescribed rotation amount)

[0034] Command example with an absolute command and feed per minute: (1) G82 Z-30.0 R-5.0 F100.0 P3.0 (2) G82 Z-30.0 R-5.0 F100.0 P0.5

[0035] The specified rotation amount can be set uniformly as a parameter. However, since a different value than the specified rotation amount may be used depending on the workpiece material, etc., it is preferable to be able to specify the specified rotation amount in the machining program as described above. If the specified rotation amount is specified in the machining program, the specified rotation amount can be used instead of the parameter.

[0036] In a command example (1), the numerical controller 1 starts the cutting feed from a point R (-5.0) and performs the dwell at the prescribed rotation amount (3 revolutions) at a point Z (-30.0). In a command example (2), the dwell at a prescribed rotation amount (0.5 revolutions) is performed in the same way.

[0037] Specifically, a commanded prescribed rotation amount P is internally converted into a dwell time by the dwell time calculation unit 111. Furthermore, although dwelling at the actual bottom of the hole (not shown) starts before the point Z(-30.0), since a time period until arriving at the point Z(-30.0) corresponding to the commanded bottom of the hole (mechanical delay time) is added to the dwell time, dwelling at the commanded bottom of the hole at the prescribed rotation amount is guaranteed. That is, a time period obtained by adding a dwell time corresponding to the commanded rotation amount P to a mechanical delay time corresponds to an actual dwell time.

[0038] According to the present embodiment, the dwell time calculation unit 111 sets the dwell time so that the dwell is performed at the prescribed rotation amount after the tool arrives at the commanded hole bottom. In this way, a drilling operation can be performed in the shortest cycle time while maintaining machining accuracy. That is, the dwell time deficiency at the hole bottom is eliminated, and the machining accuracy at the hole bottom is improved. Furthermore, an excessively long dwell time at the hole bottom is eliminated, and the cycle time can be minimized.

Claims

[1] Numerical control device (1) of a drilling machine for performing a feed operation while rotating a spindle, suspending the feed operation of the spindle for a predetermined dwell time at a predetermined hole base position and then performing a drilling operation by retracting the spindle, the numerical control device comprising: - a dwell time calculation unit (111) for calculating the dwell time based on a prescribed rotation amount in response to the specification of the prescribed rotation amount at the bore bottom position, - wherein the prescribed amount of rotation is set based on the number of blades of the tool (2) to ensure that the uncut portions within the bore are eliminated at the base position of the workpiece. [2] The numerical control device (1) according to claim 1, wherein the dwell time calculation unit (111) adds a time period corresponding to a delay at a tool position with respect to a command to the dwell time. [3] A numerical control device (1) according to claim 1, wherein the prescribed rotation amount is specified by a program command or a parameter.

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