JP2001009672A - Numerical control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform proper work even when the tool axial direction is not vertical to an XY plane by determining an angle between a tool axis directional vector and an axial moving directional vector, and controlling an optimal peripheral speed in this angle so that a cutting speed becomes the same to an optional angle by using this angle. SOLUTION: A character train such as an X code, an S code and a G code is extracted from a character train in a work program by an analyzing part 11 for inputting the work program 1 to determine an axial moving distance. For example, a moving distance running along the respective axes of X to Z is determined from coordinates of a starting point and an end point of work, and the moving distance of the respective axes is converted into a movement command of the respective axes by a distributing part 16 to be sent to a servo system 20 of the respective axes. An axial moving directional vector is calculated by an axial moving directional vector calculating part 12 from the moving distance of the respective axes, and a main spindle rotating speed command value S is determined from a desired cutting speed, a main spindle maximum rotating speed, a main spindle minimum rotating speed and a tool axis directional vector read out of respective storage parts 13, 14 by a main spindle rotating speed calculating part 15 from the value to be outputted to a main spindle drive 30.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a numerical controller suitable for machining a free-form surface at high speed and with high accuracy.

[0002]

2. Description of the Related Art In a numerically controlled (NC) machine tool for machining a free-form surface with high speed and high accuracy, a moving path of a tool is commanded by a machining program, and a moving speed of the tool along this path is also included in the machining program. It is instructed by filling in the F code. However, when moving at the speed specified by the F code, the processing accuracy may not be maintained due to error factors such as a delay in the servo system.

A recent NC apparatus for high-speed and high-precision machining of a free-form surface has a function for preventing such a problem, which is to evaluate a shape of a commanded path and allow the machining accuracy to fall within an allowable error range. In some cases, the maximum speed is determined according to the shape, and the speed is automatically reduced to a value equal to or lower than the allowable maximum speed regardless of the speed specified by the F code.

[0004] The rotation speed of the spindle is instructed by an S code in a program, and there is an optimum combination of the rotation speed of the spindle and the feed speed of the shaft depending on cutting conditions. However, if there is a function to automatically control the above-mentioned feed speed according to the shape, if these values are commanded by the F code and S code of the program, the speed value is restricted and the rotation speed of the spindle is constant. However, there is a disadvantage that the speed may be far away from the value specified by the F code.

In general, in cutting, it is said that it is a good cutting condition that the feed amount per tooth is constant and the cutting speed, that is, the relative tangential speed of the contact point between the tool and the workpiece is constant. ing.

From this viewpoint, the inventors of the present invention have filed Japanese Patent Application No.
In 175277 (JP-A-9-29584),
When machining free-form surfaces, maintain the optimal conditions for the combination of spindle speed and feed rate determined by cutting conditions,
We have proposed a numerical control device that can suppress tool wear and perform high-speed and high-precision machining. This numerical control device controls a peripheral speed in accordance with a contact diameter of a tool, which changes momentarily according to a curved surface shape, and synchronizes a rotation speed and a feed speed with a preset cutting speed. Specifically, the rotation speed of the spindle is changed by the spindle rotation speed control means in accordance with the feed speed obtained by the feed speed determination means based on the moving shape of the tool instructed by the machining program, and The main spindle rotation speed is changed by the main rotation speed control means based on a change in the contact position between the tool and the work material based on the axis movement direction information obtained by the feed speed determination means based on the moving shape of the tool. The main shaft rotation speed is changed by the main rotation speed control means based on the feed speed including the following.

As a result, the actual cutting speed is stabilized, the tool life is extended, the tool wear occurs, and a stable feed speed per tooth is obtained, so that the quality of the machined surface is improved.
The processing time can be reduced by improving the feed rate.

[0008]

However, the invention previously proposed by the inventors is based on the fact that the tool axis is
This is based on the premise that it is perpendicular to the Y plane.

For this reason, when the tool axis is not perpendicular to the XY plane but perpendicular to an arbitrary plane, such as when an angle head is used, according to the above-described invention, the rotational speed of the main shaft (in accordance with the moving direction) is determined. Even if the S code) and the feed rate (F code) are controlled, there is a problem that correct control is not performed between the tool and the shape.

The present invention has been made to solve such a problem. In machining a free-form surface, a combination of a spindle speed and a feed rate determined by cutting conditions even when the tool axis direction is not perpendicular to the XY plane. To prevent the actual processing conditions from deviating from the optimum conditions of
It is an object of the present invention to provide a numerical control device capable of suppressing tool wear and breakage, extending the life, performing high-speed and high-precision machining, and suppressing an increase in program capacity.

[0011]

According to the present invention, there is provided a numerical controller for controlling a machine tool for machining a shape surface of a work, comprising: means for designating a tool axis direction vector; Means for calculating an axis movement direction vector based on the amount, an angle formed by the tool axis direction vector and the axis movement direction vector, an optimum peripheral speed at this angle is determined by the shape surface, the tool axis direction vector, and A spindle rotation speed control means for controlling the rotation speed of the spindle so that the cutting speed is the same for an arbitrary angle using an angle formed by the axis movement direction vector is provided.

It is preferable that the apparatus further comprises feed speed control means for controlling the feed speed in accordance with the spindle speed so that the amount of movement per blade is constant.

It is preferable that the spindle speed control means further corrects the spindle speed by the output of the feed speed control means.

Further, according to the present invention, there is provided a numerical control device for controlling a machine tool for processing a shape surface of a workpiece, wherein the numerical control device reads a machining program, outputs a tool axis direction vector, and determines an axial movement amount. An analyzing unit for outputting, an axis moving direction vector calculating means for obtaining an axis moving direction vector from each of the axial moving amounts, and a tool axis inclination and commanded by a machining program from the tool axis direction vector and the axis moving direction vector. Calculate the spindle rotation speed based on the change in the contact position between the tool and the work material according to the axis movement direction,
Spindle speed control means for outputting to the spindle driver;
The apparatus further comprises a distribution unit that calculates a feed rate based on an output of the spindle rotation speed control unit and an amount of movement in each axis direction from the analysis unit.

An angle θ with respect to the XY plane as a processing tool
Using a ball end mill having a radius R (mm) inclined only by an angle, the tool axis direction vector is Vt, the movement direction vector Vd, and the optimum peripheral speed when θ = π / 2 is V0 (mm).
/ Min), and the spindle speed at this time is S0 (rp
m), the spindle speed control means calculates the spindle speed S according to the following equation: S = S0 | Vt || Vd | /Vt.Vd (rpm), and the distribution unit calculates the feed speed for S0. Let F = F0 | Vt || Vd | /Vt.Vd (mm / m)
in) is preferably calculated.

It is preferable that the rotation speed control unit further includes a limiter that limits the calculated main shaft rotation speed by giving upper and lower values to the calculated main shaft rotation speed.

In the numerical controller according to the present invention, even when the tool axis is not perpendicular to the XY plane using an angle head or the like, the feed amount per tooth is constant and the cutting speed, that is, The relative tangential velocity between the contact point of the workpiece and the workpiece becomes constant, thereby suppressing tool wear and breakage, extending tool life and shortening machining time.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a schematic configuration of a numerical controller 10 according to an embodiment of the present invention. In this embodiment, the spindle speed command value is not commanded in the machining program.

The machining program 1 is sent to the analysis unit 11,
It is analyzed here. The analysis unit 11 extracts a character string such as an X code, an S code, a G code, and an M code from the character string in the machining program, and calculates the axis movement amount from the extracted character string. For example, the amount of movement along the X, Y, and Z axes can be determined from the coordinates of the starting point and the ending point of the machining. Further, a tool axis direction vector is obtained from the coordinates and angles of the tool. These amounts are obtained for each block.

The movement amount of each axis is converted into a movement command of each axis by the distribution unit 16 and sent to the servo system 20 of each axis.

On the other hand, the amount of movement of each axis is given to an axis movement direction vector calculation section 12, where the axis movement direction vector is calculated and sent to a spindle speed calculation section 15.

The spindle speed calculating section 15 stores the desired cutting speed as a reference value stored in the desired cutting speed storage section 13, the maximum spindle speed, and the maximum spindle speed stored in the minimum spindle speed storage section 14. The rotation speed, the minimum spindle rotation speed, the above-described tool axis direction vector, and the spindle override amount are input, and the spindle rotation speed command value S is obtained based on these. This command value S is output to the spindle driver 30.

The method of calculating the spindle speed is, for example, as follows. In the present invention, since it is assumed that the tool axis is not perpendicular to the work plane, it is necessary to define the tool axis direction as a parameter or a variable. Therefore, as shown in FIG. 2, a tool axis direction vector Vt and a movement direction vector Vd are defined.

FIG. 2 shows a tool 40 and a workpiece 50 represented as end mills. The angle between the tool axis direction vector Vt and the moving direction vector Vd is represented by ψ, π / 2− as shown in FIG. If ψ = θ, the spindle speed S
The peripheral speed at the cutting point of the tool having the radius R (mm) at (rpm) is as follows: V = 2πrS (mm / min) r = Rsin (θ) (mm)

The optimum peripheral speed when θ = π / 2 is V0
(Mm / min), and S at this time is S0 (rpm)
Then, since there is a relationship of V0 = 2πRS0, in order to always keep the peripheral speed at V0 at an arbitrary θ, since 2πRS0 = 2πRsin (θ) S, S = S0 / sin (θ). S = S0 / cos (ψ)

Here, considering the inner product of Vt and Vd, Vt · Vd = | Vt || Vd | cos (ψ), so that cos (ψ) = Vt · Vd / | Vt || Vd |.

Using this relationship, S = S0 | Vt || Vd | /Vt.Vd (rpm).

The spindle speed S is sent to the distribution unit 16,
A tool feed speed is also calculated.

That is, assuming that the above-mentioned feed speed for S0 is F0, F for S is F = F0 | Vt || Vd | /Vt.Vd (mm / m
in). At this time, if the tool direction vector is a unit vector, | Vt | = 1, so that F = F0 | Vd | / VtVd (mm / min). This F value may be set as the upper limit speed. In the main shaft rotation speed calculating section 15, the main shaft rotation speed obtained by the above-described procedure can be corrected as required. If Kx = actual feed speed / reference feed speed, Sx = command rotation speed * Kx * Spindle override. However, since this rotation speed should be between the predetermined minimum rotation speed and the maximum rotation speed, Sx may be determined so as to satisfy the condition of minimum rotation speed ≦ Sx ≦ maximum rotation speed. .

According to this embodiment, the axis movement direction vector is obtained from the movement amount of each axis, and the spindle speed is obtained together with the tool axis direction vector specified by the machining program. Since it is not necessary to add the rotation speed command value (S command value) in the program, the machining program can be shorter than in the case where the optimal S command value is added to the machining program. No need to increase the communication speed during remote buffer operation.

When the tool axis is XY using an angle head or the like,
Optimal cutting conditions are maintained even when not perpendicular to the plane.

In the above embodiment, the spindle speed is first optimized, and the feed speed is made to follow the speed. However, as shown in FIG. The rotation speed may be input to the rotation speed calculation unit to finally correct the main shaft rotation speed.

[0034]

As described above, in the numerical controller according to the present invention, since the control is performed so as to maintain the optimum cutting speed by using the tool axis direction vector and the moving direction vector, the XY control is performed by using the angle head or the like. Even when the tool axis is not perpendicular to the plane, the feed per tooth is constant,
In addition, the cutting speed is constant, tool wear and breakage can be suppressed, tool life can be extended, and machining time can be shortened.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing the principle in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Machining program 10 Numerical control apparatus 11 Analysis part 12 Axis movement direction vector calculation part 13 Desired cutting speed storage part 14 Main spindle maximum rotation number, minimum rotation number storage part 15 Spindle rotation number calculation part 16 Distribution part 20 Servo mechanism 30 Spindle driver

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[Procedure amendment]

[Submission date] July 12, 1999 (1999.7.1)
2)

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] All figures

[Correction method] Change

[Correction contents]

FIG.

FIG. 2

Claims (6)

[Claims] 1. A numerical controller for controlling a machine tool for processing a shape surface of a workpiece, comprising: means for designating a tool axis direction vector; and calculating an axis movement direction vector based on each axis movement amount for each sampling. Means, the angle between the tool axis direction vector and the axis movement direction vector, the optimum peripheral speed at this angle the shape surface, using the angle between the tool axis direction vector and the axis movement direction vector. A numerical control device comprising: a spindle rotation speed control means for controlling a rotation speed of a spindle so that a cutting speed is the same for an arbitrary angle. 2. The numerical control device according to claim 1, further comprising a feed speed control means for controlling a feed speed in accordance with said spindle speed so that a movement amount per blade is constant. 3. The numerical control device according to claim 2, wherein said spindle rotation speed control means further corrects the rotation speed of the spindle by an output of said feed speed control means. 4. A numerical controller for controlling a machine tool for processing a shape surface of a work, comprising: an analysis unit that reads a processing program, outputs a tool axis direction vector, and outputs an amount of movement in each axis direction; An axis moving direction vector calculating means for obtaining an axis moving direction vector from each of the axial moving amounts; a tool associated with a tool axis tilt and an axis moving direction instructed by a machining program from the tool axis direction vector and the axis moving direction vector; Spindle speed control means for calculating a spindle speed based on the change in the contact position between the workpiece and the work material, and outputting the spindle speed to the spindle driver; and the output of the spindle speed control means and each axis direction from the analysis unit. A numerical control device comprising a distribution unit that calculates a feed speed based on a movement amount. 5. An angle θ with respect to an XY plane as a processing tool.
Using a ball end mill having a radius R (mm) inclined only by an angle, the tool axis direction vector is Vt, the movement direction vector Vd, and the optimum peripheral speed when θ = π / 2 is V0 (mm).
/ Min), and the spindle speed at this time is S0 (rp
m), the spindle rotation speed control means calculates the spindle rotation speed S according to the following equation: S = S0 | Vt || Vd | /Vt.Vd (rpm), and the distributing unit calculates the feed speed for S0. Let F = F0 | Vt || Vd | /Vt.Vd (mm / m)
The numerical controller according to claim 4, wherein the numerical controller is calculated according to the following equation: 6. The numerical control according to claim 4, wherein said rotation speed control unit further comprises a limiter for giving an upper limit and a lower limit to the calculated spindle speed to limit the calculated spindle speed. apparatus.