JPH07251351A - Rotation speed control method for rotary cutting tool and cutting work device - Google Patents

Abstract

PURPOSE:To maintain a feed quantity per rotation of a rotary cutting tool at nearly constant even the actual feed speed of the rotary cutting tool is deviated from a command feed speed due to the delay of data processing and the like. CONSTITUTION:Signals SFx, SFy, and SFz, expressing moving speeds in the 3-axis directions of a 3-axis moving table for moving a rotary cutting tool, are inputted in a rotation speed control part 32 to calculate an actual feed speed F from the moving speed. Also, a target rotation speed S is calculated according to the following expression from a command feed speed Fo and a command rotation speed So preset in an NC program to control a main spindle motor 18 so as to rotate and drive the rotary cutting tool at the target rotation speed. S=F.So/Fo.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention controls the rotational speed of a rotary cutting tool when the rotary cutting tool is rotationally driven about its axis and is moved relative to a work material while performing cutting. The present invention relates to a method and a cutting device in which the rotation speed of a rotary cutting tool is controlled according to the rotation speed control method.

[0002]

2. Description of the Related Art In the case of performing a predetermined cutting while rotating a rotary cutting tool such as a ball end mill or a milling cutter around a shaft and moving the rotary cutting tool relative to a work material, for example, JP-A-61-168008. It is usually done according to an NC (Numerical Control) program as described in. NC programs generally include commands related to cutting conditions such as tool rotation speed, feed rate, and cutting cross-sectional area.
The cutting conditions are set in accordance with, for example, a predetermined standard condition table. This standard condition table is set by the tool manufacturer by comprehensively judging the tool life and the machining efficiency according to the material of the work material, the machining conditions such as the machining accuracy, the type of the tool, and the diameter dimension. In addition, the command related to the movement path is created by a CAM (Computer Aided Manufacturing) device based on the shape data before and after processing so that the cutting process of the predetermined shape is performed while satisfying the feed rate and cutting cross-sectional area of the above cutting conditions. Or set by teaching.

[0003]

However, the above N
When performing cutting while moving the rotary cutting tool relative to the work material in accordance with the C program, send the tool according to the command value with a delay in data processing in a portion where the movement direction of the tool changes greatly such as a corner portion. May not be possible and the feed rate may temporarily decrease. When the feed speed is reduced in this way, the feed amount per rotation of the rotary cutting tool that is rotationally driven at a preset number of revolutions is reduced, so that the cutting amount per blade is reduced and the cutting heat generated by the cutting chips is reduced. The removal effect of the tool decreases, the temperature of the cutting edge rises, which promotes wear and chipping of the cutting edge, while the cutting resistance decreases as the cutting amount per cutting edge decreases. Inclination (flexural deformation) of the tool is reduced as compared with the portion where the tool is sent, and the machining accuracy is reduced. If you slow down the feed rate in advance, you can move it at a constant feed rate even at corners, etc.
Machining efficiency decreases and machining time becomes longer.

The present invention has been made in view of the above circumstances, and an object thereof is to keep the feed amount per one revolution of a rotary cutting tool substantially constant regardless of the change of the feed speed. Is to

[0005]

In order to achieve such an object, a first aspect of the present invention is to perform a cutting process while rotating a rotary cutting tool around an axis and moving the rotary cutting tool relative to a work material. A method of controlling the number of revolutions of the rotary cutting tool when performing, (a) a speed detecting step of detecting an actual feed speed F of the rotary cutting tool, and (b) one revolution of the rotary cutting tool. A rotation speed control step of controlling the rotation speed S of the rotary cutting tool according to the actual feed speed F so that the feed amount per hit becomes a predetermined set value f.

[0006]

That is, first, in the speed detecting step, the actual feed speed F of the rotary cutting tool that is moved relative to the work material is detected, and in the rotation speed control step, the rotary cutting tool The rotation speed S of the rotary cutting tool is controlled according to the actual feed speed F so that the feed amount per revolution becomes a predetermined set value f. When the actual feed speed F is detected, for example, when the tool is three-dimensionally moved relative to each other by the three-axis moving table, each moving speed in the three-axis directions is detected from the rotation speed of the servo motor and the like. The moving speeds in the directions may be squared and added, and the square root thereof may be obtained. Further, the set value f may set the feed amount per one turn of the rotary cutting tool itself, but if the command feed speed Fo and the command rotation speed So are set as the cutting conditions, for example, both unit times are set. If they are the same, the set value f is represented by Fo / So, and the feed amount per one rotation may be fixed at least. Feed amount per blade Fz
Also, the set value f = Fz.Z can be set from the number of blades and Z. Then, if the actual feed speed F is divided by the set value f, the number of rotations S at which the feed amount per rotation becomes the set value f is obtained, and the number of rotations S is calculated from the relationship of F / S = Fo / So. You can also ask. The feed speeds F and Fo are relative movement speeds of the rotary cutting tool and the work material, and include not only the case of moving the rotary cutting tool but also the case of moving the work material.

With this configuration, even if the feed rate F changes due to a delay in data processing or the like, the feed amount per rotation of the rotary cutting tool is maintained at the set value f. Therefore, the change in the cutting amount per blade due to the fluctuation of the feed speed F is prevented, the cutting amount per blade decreases and the blade edge temperature rises, so that wear and chipping are promoted, and It is possible to prevent the cutting amount per hit from increasing to cause a chipping of the blade and to obtain a predetermined tool life. Also,
Since the amount of cutting per blade is kept substantially constant, the cutting resistance is stabilized, the way the tool falls down is kept substantially constant, and the machining accuracy is improved. Furthermore, even if the feed rate F changes in this way, the tool life and machining accuracy do not decrease, so the feed rate F
It is also possible to set a relatively high speed for high efficiency machining.

[0008]

[Second Means for Solving the Problems] The second invention is
(A) movement control means for moving the rotary cutting tool relative to the work material at a constant command feed rate Fo according to a predetermined NC program; and (b) rotationally driving the rotary cutting tool around an axis. (C) a speed detecting means for detecting an actual feed speed F of the rotary cutting tool which is moved relative to the work material by the movement control means, in a cutting apparatus provided with a tool rotating means; Regarding the rotational speed of the rotary cutting tool, the target rotational speed S that satisfies the following equation with respect to the command rotational speed So set in the NC program
And a rotational speed control means for controlling the tool rotating means so that the rotary cutting tool is rotationally driven. S = F · So / Fo

[0009]

In the cutting apparatus described above, when the rotary cutting tool is moved relative to the work material at a constant command feed speed Fo in accordance with a NC program predetermined by the movement control means. , The actual feed speed F is detected by the speed detecting means, and S = F.multidot.F for the commanded rotational speed So set in the NC program.
The rotation speed control means controls the tool rotation means so that the rotary cutting tool is rotationally driven at the target rotation speed S that satisfies So / Fo. That is, the target rotation speed S at which the feed amount per rotation of the rotary cutting tool is Fo / So is calculated according to the actual feed speed F, and the rotary cutting tool is rotationally driven at the target rotation speed S. The tool rotating means is controlled, and the same effect as the first invention in which the rotation speed is controlled so that the feed amount per rotation of the rotary cutting tool becomes the set value f can be obtained. Further, since the target rotation speed S is calculated based on the command feed speed Fo and the command rotation speed So preset in the NC program, the NC program is changed or the set value f is set separately. It is not necessary, and the cutting process can be performed by the same operation as in the past.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic configuration diagram of a cutting device 10 for cutting a molding surface of a press die, and a work material 12 such as a die material is positioned and fixed at a predetermined position on a positioning table 14. . Positioning table 14
A rotary cutting tool 16 such as a milling cutter or an end mill is attached to the main shaft 20 of the main shaft motor 18 in a posture in which the rotary cutting tool 16 faces downward.
The rotary cutting tool 16 is parallelly moved three-dimensionally by the shaft moving table 22, and while the rotary cutting tool 16 is driven to rotate about the axis by the main shaft motor 18, the rotary cutting tool 16 is three-dimensionally moved by the three-axis moving table 22 together with the main shaft motor 18. The workpiece 12 is subjected to a predetermined cutting process by being moved. The spindle motors 18 and 3
The axis movement table 22 is an NC controller 26 according to an NC program previously stored in the NC program memory 24.
Controlled by.

FIG. 2 is a block diagram for explaining the control system of the cutting apparatus 10. The NC program is stored in the NC program memory 24 including a paper tape or a magnetic disk. This NC program is 3 as a program related to the moving path of the rotary cutting tool 16.
The X-axis position command, the Y-axis position command, and the Z-axis position command of the axis movement table 22 and the command rotation speed So regarding the rotation speed of the spindle motor 18 are included.
It is created by a CAM device or the like based on the shape data before and after machining so that the rotary cutting tool 16 is moved at a preset command cutting cross-sectional area and a command feed speed Fo. The command cut sectional area and the command feed speed Fo are also stored in the NC program memory 24.

The NC control device 26 comprises a microcomputer for performing signal processing according to a program previously stored in the ROM while utilizing the temporary storage function of the RAM, and reads the NC program from the NC program memory 24 to execute the above-mentioned processing. The three-axis moving table 22 and the spindle motor 18 are controlled, and the X-axis position controller 28, the X-axis speed controller 30 related to the control of the three-axis moving table 22, and the control of the spindle motor 18 are related. The rotational speed control unit 32 is provided functionally. X-axis position controller 28
The X-axis speed control unit 30 controls the number of rotations of the X-axis servo motor 34 of the three-axis moving table 22 according to the X-axis position command, and the X-axis position control unit 28 controls the X-axis position.
A signal representing the X-axis direction position is supplied from the axis position detector 36, and a signal SFx representing the X-axis direction speed Fx is supplied from the X-axis speed detector 38 to the X-axis speed control unit 30 for feedback control. It is like this. The X-axis position detector 36 is composed of a rotary encoder,
The X-axis speed detector 38 is composed of a detector for detecting a motor current or voltage corresponding to the rotation speed of the X-axis servo motor 34, and the X-axis direction speed Fx is integrated to obtain the X-axis direction position. Alternatively, the change in the X-axis direction position may be differentiated to obtain the X-axis direction speed Fx. Although not shown, the 3-axis movement table 22 includes a Y-axis servo motor and a Z-axis servo motor in addition to the X-axis servo motor 34, and these servo motors are the same as the X-axis servo motor 34. Further, the NC controller 26 controls the Y-axis position command and the Z-axis position command. As a result, the rotary cutting tool 16 can be moved along a predetermined moving path at a constant command feed speed Fo. In the present embodiment, the X-axis position controller 2 of the NC controller 26 is used.
8, X-axis speed control unit 30 and Y-axis position control unit (not shown),
The Y-axis speed control unit, the Z-axis position control unit, the Z-axis speed control unit, and the three-axis movement table 22 constitute movement control means.

The rotation speed control unit 32 is for controlling the rotation speed of the spindle motor 18 when cutting is actually performed, and reads the command feed speed Fo and the command rotation speed So from the NC program memory 24. Together with the X
From the axis speed detector 38, the Y axis speed detector (not shown), and the Z axis speed detector, the X axis direction speed Fx, the Y axis direction speed Fy,
The signals SFx, SFy, SFz representing the Z-axis direction speed Fz are fetched, and the rotation speed of the spindle motor 18 is controlled according to the flowchart shown in FIG. The flowchart of FIG. 3 is repeatedly performed with a predetermined cycle time,
First, in step S1, the signals SFx, SFy, SFz are taken in, and in step S2, those signals SFx, SFy, Sz are fetched.
From the X-axis direction speed Fx, the Y-axis direction speed Fy, and the Z-axis direction speed Fz represented by Fz, the actual feed rate F is calculated according to the following equation (1).
To calculate. In step S3, the speed ratio α (= F / Fo) between the feed speed F and the command feed speed Fo is obtained, and in step S4, the speed ratio α and the command rotation speed So are multiplied to calculate the target rotation speed S. . Then, in step S5,
The motor current and voltage are controlled so that the spindle motor 18 rotates at the target rotation speed S. This target speed S
Is, after all, F · So / Fo, so the feed amount per revolution of the spindle motor 18, that is, per revolution of the rotary cutting tool 16 is always a constant value F regardless of the actual feed speed F.
It becomes o / So. Steps S1 and S2 are speed detection steps, steps S3, S4, and S5 are rotation speed control steps, and the constant value Fo / So corresponds to a preset set value f. Further, of the series of signal processing by the NC control device 26, the part that executes steps S1 and S2 constitutes a speed detecting means together with the X-axis speed detector 38, the Y-axis speed detector (not shown), and the Z-axis speed detector. In addition, the part that executes steps S3, S4 and S5 corresponds to the rotation speed control means, and the spindle motor 18 corresponds to the tool rotation means. F = √ (Fx ² + Fy ² + Fz ² ) (1)

According to the cutting apparatus 10 of this embodiment as described above, even if the actual feed speed F becomes lower than the command feed speed Fo due to a delay in data processing or the like, one rotation of the rotary cutting tool 16 is performed. The spindle motor 18 is adjusted according to the actual feed speed F so that the feed amount per hit becomes a constant value Fo / So.
Since the number of rotations is controlled, the cutting amount per blade is maintained substantially constant. This prevents wear and chipping due to a decrease in the cutting amount and an increase in the cutting edge temperature,
A predetermined tool life can be obtained, the cutting resistance is stable, and the tool tilting direction is maintained substantially constant, so that the machining accuracy is improved. Further, even if the actual feed speed F changes in this way, the tool life and the machining accuracy do not decrease, so that it is possible to set the command feed speed Fo to a relatively high speed and perform highly efficient machining. Further, in this embodiment, the command feed speed Fo and the command rotation speed So preset in the NC program are set.
Since the target rotation speed S is calculated from the actual feed speed F based on the above, it is not necessary to change the NC program or perform a special operation. It can be carried out.

Although one embodiment of the present invention has been described in detail with reference to the drawings, the present invention can be implemented in other modes.

For example, although the rotary cutting tool 16 is moved in parallel by the three-axis moving table 22 in the above embodiment, the rotary cutting tool 16 is moved by using other moving means such as an articulated robot. You can also
It is also possible to hold the rotary cutting tool 16 in a fixed position and move the work material 12, or to move both the rotary cutting tool 16 and the work material 12.

In the above embodiment, the command feed speed Fo and the command rotation speed So stored in the NC program memory 24 are used.
The target rotation speed S was calculated using
The setting value f can be set in the NC controller 26,
The target feed speed S is calculated by dividing the actual feed speed F by the set value f.
The method of calculating the target rotation speed S may be changed as appropriate, such as calculating The set value f may be set in the NC program instead of the command rotation speed So.

Further, in the above embodiment, the rotary cutting tool 16 is moved at a predetermined constant command feed speed Fo, but the feed speed of the rotary cutting tool 16 changes in the middle of the movement path. Is defined as
The rotation speed control method according to the first aspect of the invention can be similarly applied even when the feed rate is changed according to a change in cutting resistance or the like.

Although not illustrated one by one, the present invention can be implemented in various modified and improved modes based on the knowledge of those skilled in the art.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a cutting apparatus that is an embodiment of a second invention and that can suitably implement the rotation speed control method of the first invention.

FIG. 2 is a block diagram illustrating a control system of the cutting apparatus of FIG.

FIG. 3 is a flowchart illustrating a function of a rotation speed control unit in FIG.

[Explanation of reference symbols] 10: Cutting device 12: Work material 16: Rotary cutting tool 18: Spindle motor (tool rotating means) 22: 3-axis moving table (moving control means) 26: NC control device 28: X-axis position Control unit (movement control unit) 30: X-axis speed control unit (movement control unit) 32: Rotation speed control unit 38: X-axis speed detector (speed detection unit) Steps S1 and S2: Speed detection process, speed detection unit Step S3, S4, S5: Rotational speed control process, rotational speed control means

Claims (2)

[Claims] 1. A method for controlling the number of revolutions of a rotary cutting tool when performing cutting while rotating the rotary cutting tool around an axis and moving the rotary cutting tool relative to a work material, said method comprising: A speed detection step of detecting an actual feed speed F of the rotary cutting tool, and a step of adjusting the actual feed speed F so that the feed amount per one rotation of the rotary cutting tool becomes a preset set value f. A rotation speed control step of controlling the rotation speed S of the rotary cutting tool. 2. A movement control means for moving the rotary cutting tool relative to a work material at a constant command feed speed Fo according to a predetermined NC program, and a tool for rotationally driving the rotary cutting tool around an axis. In a cutting device including a rotating means, a speed detecting means for detecting an actual feed speed F of the rotary cutting tool which is relatively moved with respect to a work material by the movement control means, and a rotation of the rotary cutting tool. With respect to the number of rotations, a rotation speed control means for controlling the tool rotation means so that the rotary cutting tool is rotationally driven at a target rotation speed S satisfying the following equation with respect to a command rotation speed So set in the NC program: = F · So / Fo.