JPS62204311A - Arithmetic method for circular arc interpolation of numerical control - Google Patents

Abstract

PURPOSE:To improve the follow-up accuracy even in a high-speed feed mode by calculating a reduction amount of the radius to a commanded circular arc, adding this radius reduction amount to the circular arc interpolation data for correction of the shift data and therefore eliminating the radius reduction amount. CONSTITUTION:The radius reduction amount is calculated for each sampling, for example, based on the radius of a commanded circular arc, the feed speed, the override of the feed speed, the position loop gain constant and the acceleration/deceleration time constant. The calculated radius reduction amount is added to the circular arc interpolation shift data for correction of the shift data. Thus the radius reduction amount is eliminated in a circular arc interpolation mode and the actual tool locus can be set close to the NC program command value as much as possible. Furthermore the feed speed limited in the circular arc interpolation mode is increased for reduction of the working time.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a circular interpolation calculation method in numerical control,
For example, it can be used as a calculation method for generating tool trajectory data during circular interpolation cutting.

[Background technology and its problems]

In circular interpolation cutting in numerical control of machine tools,
Generate tool path data using an NC program (for example, GO2X YrJF-, where the rotation direction of the arc, the coordinates of the end point of the arc, the distance from the start point to the center of the arc, and the feed rate are given), and convert this to a plane. The upper two-axis components (X and Y-axis components) are distributed and given as command values to the respective positioning servo systems, and the tool movement is obtained through simultaneous two-axis control.

This will be explained with reference to FIG. Set the sampling time to Δ
T (sec), feed speed F(0′″/,i,),
If the feed rate override is α [%], the movement amount ΔL [μ] for one sampling time is, and the rotation angle Δθ (rad) at that time is R, where R is the radius of the circular arc. be.

Now, the coordinate value of the creation time is (1,,J,), the angle between the straight line connecting that point and the center of the arc and the X axis is θ, and the coordinate value after one sampling is zL. 1°J, l. 1), the current value (1,, J,) is 1, l +, and the coordinate value after one sampling (1-+, Jll, etc.).

)teeth, becomes.

Here, assuming that Δθ- is one minute, it can be approximated as follows, so the coordinate value after one sampling (
I A-+, J Ll-+) is ■ 7.1 = Rcos OcosΔ θ −Rsinθsin
Δ θ= I, l (1--)-J, Δ θ
・・・ ・・・ (68) J74゜=RsinθcosΔ θ + RcosθsinΔ
θΔ θ 2 =Rsinθ(1-) +R(cos θ) Δ
θΔ θ 2 − J ll (1--) + I II Δ θ
It can be expressed as (6B). Therefore, the movement amounts Δ■7 and ΔJ7 between one sampling are as follows: Δ16=191 1°Δ θ 2 =-J, l Δθ−I11□ ・・・・・・・・・・・・・・・
・(7A) Δ J ll = J , 1. , −J 11Δ
θ Snow? It can be expressed as

By calculating these movement amounts Δr, .DELTA.J11 for each sampling and instructing the positioning servo system as the movement amounts, a tool trajectory according to the program can be obtained.

In such conventional calculation methods, the actual movement of the tool with respect to the generated tool trajectory is determined by the position loop gain of the positioning servo system, the acceleration/deceleration constant of the feed rate, the radius of the command arc, and the feed rate.

An error occurs due to radius reduction.

This will be explained according to FIG. In FIG. 3, ■ indicates the commanded tool trajectory, and ■ indicates the actual tool movement trajectory. The radius reduction amount ΔR of ■ with respect to
Two equations, i.e. -) the equation when acceleration/deceleration is not used, 2)
It can be approximated by the equation when using exponential acceleration/deceleration and 3) the equation when using linear acceleration/deceleration.

However, R: radius T of the command arc; reciprocal of the position loop gain constant T0; exponential acceleration/deceleration constant (cutting feed) Tt; 7 linear acceleration/deceleration constant (cutting feed) F; cutting feed rate. Therefore, the radius reduction amount ΔR becomes larger as the feed rate is faster, the radius R is smaller, or the acceleration/deceleration time constant is larger.

Conventionally, when performing circular interpolation cutting, a method has been adopted in which the feed rate is limited so that the radius decrease does not exceed a set value. Normally, in large machines, the weight of the driven body is large and the acceleration/deceleration constant has a fairly large value, so the amount of radius reduction is currently almost determined by the acceleration/deceleration time constant.

Therefore, it becomes a big problem for tools such as mold processing machines that often perform contour processing and require high cutting speeds.

[Purpose of the invention]

The purpose of the present invention is to solve these conventional problems, eliminate radius reduction, and operate tools according to program command values, while at the same time providing circular interpolation in numerical control with less error even at high-speed cutting feeds. The objective is to provide a calculation method.

[Means and actions for solving problems] Therefore,
In the present invention, the radius and feed rate of the command arc obtained from the circular interpolation data of the NC program, the arbitrarily set feed speed override, and the position loop gain and acceleration/deceleration time constant of the positioning servo system are used to calculate the command arc. The present invention is characterized in that a radius decrease amount is calculated for the radius, and this radius decrease amount is added to the circular interpolation data to correct the movement data.

In short, based on the command arc radius, feed rate, feed rate override, position loop gain constant, and acceleration/deceleration time constant, for example, calculate the radius reduction amount for each sampling, and add this to the circular interpolation movement data. By correcting the movement data, the actual tool trajectory is corrected so as not to cause an error with respect to the command value of the NC program, and the tracking accuracy is improved even during high-speed feeding.

〔Example〕

An embodiment of the invention will be described with reference to FIG. In the figure, ■ indicates a tool trajectory based on the NC program, and ■ indicates a tool trajectory corrected according to the present invention.

Now, the symbols in the diagram are defined as follows.

(1,l,J,)i is the coordinate value of the program command value at a certain time T.

(1',, J'piece; Coordinate value corrected for radius decrease at a certain time T.

([,,-+,J,,l); Coordinate value of program command value after 1 sampling.

(1'a-++ J'n+r) i Coordinate value corrected for radius decrease after sampling.

ΔR: Radius decrease amount at a certain time T.

ΔI? , , Radius reduction amount after il sampling.

Here, in (8A) to (8C) 2 above, since it is customary to select either an exponential function type or a linear type for the acceleration/deceleration time constant, the radius reduction amount Δ
Rn can be calculated as follows.

Therefore, each coordinate value (1'
n, J's) (bih l + J',, +
1) can be calculated as follows.

Bin n”Ia+ΔR, cosθ ΔR7 ” I, ++ I 'n □ j', = Jll+ Δ RRsinθ +'ll+l −E 11. , 10A R11-+CO
3(19+ A I9 )Δ R7,.

-I, 1.1 +Ill++ □■nJ'n++ = J n+++ΔRg*l5ln(θ
+Δθ)ΔR7,.

≠ Jn,I +JR,l □ Therefore, the corrected increment Δ('7ΔJ/
7 can be calculated as follows.

Δ　I’m　-1’＊＊＋　　　I’n■ - Δ IM + <In-+ ΔR7,.

−r, lΔR1,) ・・・・・・・・・
... (12B) ΔJ', w J',,, -
J'.

1 Δ Jn 10-(Jll, I ΔRB * 11 J
ll ΔR,) ・・・・・・・・・・・・
...(12B) However, Δ! ΔJ7 is the increment of the trajectory according to the program command value.

From this, for each sampling, the above (12A) (1
By calculating ΔI′ and ΔJ/1 in equation 2B) and commanding the tool trajectory with the radius reduction amount corrected, it is possible to make the actual tool movement trajectory as close as possible to the NC program trajectory.

Therefore, in the past, it was not possible to increase the cutting speed above a certain value due to errors due to radius reduction, but according to this embodiment, it is possible to increase the cutting speed and accuracy regardless of the radius of the commanded arc and the feed rate.

〔Effect of the invention〕

As described above, according to the present invention, the amount of radius decrease during circular interpolation is eliminated, the actual tool trajectory can be brought as close as possible to the NC program command value, and the feed rate, which was conventionally limited during circular interpolation, can be increased to a high speed. This has the advantage of reducing machining time.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the circular interpolation calculation method of the present invention, and FIG.
FIG. 3 is an explanatory diagram showing a conventional circular interpolation calculation method, and FIG. 3 is an explanatory diagram showing an actual tool trajectory with respect to a tool trajectory generated by the conventional circular interpolation calculation method.

Claims (1)

[Claims] (1) Radius reduction for the command arc based on the radius and feed rate of the command arc obtained from the circular interpolation data of the NC program, the arbitrarily set feed speed override, and the position loop gain and acceleration/deceleration time constant of the positioning servo system A circular interpolation calculation method in numerical control, characterized in that the movement data is corrected by calculating the radius reduction amount and adding the radius reduction amount to the circular interpolation data.