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FANUC Series 30i/300i/300is-MODEL A. Machining Center System. User's manual - page 26

5.FEED FUNCTIONS

PROGRAMMING

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5.4

CUTTING FEEDRATE CONTROL

Cutting feedrate can be controlled, as indicated in Table 5.4 (a).

Table 5.4 (a) Cutting Feedrate Control

Function name

G code

Validity of G code

Description

Exact stop

G09

This function is valid for
specified blocks only.

The tool is decelerated at the end point of a
block, then an in-position check is made.
Then the next block is executed.

Exact stop mode

G61

Once specified, this function is
valid until G62, G63, or G64 is
specified.

The tool is decelerated at the end point of a
block, then an in-position check is made.
Then the next block is executed.

Cutting mode

G64

Once specified, this function is
valid until G61, G62, or G63 is
specified.

The tool is not decelerated at the end point of
a block, but the next block is executed.

Tapping mode

G63

Once specified, this function is
valid until G61, G62, or G64 is
specified.

The tool is not decelerated at the end point of
a block, but the next block is executed.
When G63 is specified, feedrate override and
feed hold are invalid.

Automatic
override for inner
corners

G62

Once specified, this function is
valid until G61, G63, or G64 is
specified.

When the tool moves along an inner corner
during tool radius compensation, override is
applied to the cutting feedrate to suppress the
amount of cutting per unit of time so that a
good surface finish can be produced.

Automatic

corner

override

Internal circular
cutting feedrate
change

This function is valid in the tool
radius compensation mode,
regardless of the G code.

The internal circular cutting feedrate is
changed.

NOTE

1 The purpose of in-position check is to check that

the servo motor has reached within a specified
range (specified with a parameter by the machine
tool builder).

In-position check is not performed when bit 5 (NCI)
of parameter No. 1601 is set to 1.

2 Inner corner angle

: 2

≤

178

(

is a set value)

Workpiece

Tool

Format

Exact stop

G09

_ ;

Exact stop mode

G61 ;

Cutting mode

G64 ;

Tapping mode

G63 ;

Automatic corner override

G62 ;

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PROGRAMMING

5.FEED FUNCTIONS

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5.4.1

Exact Stop (G09, G61), Cutting Mode (G64), Tapping Mode

(G63)

Explanation

The inter-block paths followed by the tool in the exact stop mode,
cutting mode, and tapping mode are different (Fig. 5.4.1 (a)).

Tool path in the exact stop mode

Tool path in the cutting mode or tapping mode

In-position check

(1)

(2)

Fig. 5.4.1 (a) Example of tool paths from block (1) to block (2)

CAUTION

The cutting mode (G64 mode) is set at power-on or
system clear.

5.FEED FUNCTIONS

PROGRAMMING

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5.4.2

Automatic Corner Override

When tool radius compensation is performed, the movement of the
tool is automatically decelerated at an inner corner and internal
circular area. This reduces the load on the tool and produces a
smoothly machined surface.

5.4.2.1

Automatic override for inner corners (G62)

Explanation
- Override condition

When G62 is specified, and the tool path with tool radius
compensation applied forms an inner corner, the feedrate is
automatically overridden at both ends of the corner.
There are four types of inner corners (Fig. 5.4.2(a)).
2

°≤θ≤θ

≤

178

in Fig. 5.4.2(a)qp is a value set with parameter No.

1711. When

is approximately equal to

p, the inner corner is

determined with an error of 0.001

or less.

: Tool

: Programmed path

: Tool center path

1. Straight line-straight line

2. Straight line-arc

3. Arc-straight line

4. Arc-arc

Fig. 5.4.2(a) Inner corner

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PROGRAMMING

5.FEED FUNCTIONS

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- Override range

When a corner is determined to be an inner corner, the feedrate is
overridden before and after the inner corner. The distances Ls and Le,
where the feedrate is overridden, are distances from points on the tool
center path to the corner (Fig. 5.4.2(b), Fig. 5.4.2(c), Fig. 5.4.2(d)). Ls
and Le are set with parameter Nos. 1713 and 1714.

Programmed path

Tool center path

The feedrate is overridden from point a to point b.

FIg. 5.4.2.1 (b) Override Range (Straight Line to Straight Line)

When a programmed path consists of two arcs, the feedrate is
overridden if the start and end points are in the same quadrant or in
adjacent quadrants (Fig. 5.4.2(c)).

Programmed path

The feedrate is overridden from point a to b.

Tool center path

Fig. 5.4.2(c) Override Range (Arc to Arc)

Regarding program (2) of an arc, the feedrate is overridden from point
a to point b and from point c to point d (Fig. 5.4.2(d)).

(2)

Programmed path

Tool center path

Tool

Fig. 5.4.2(d) Override Range (Straight Line to Arc, Arc to Straight Line)

- Override value

An override value is set with parameter No. 1712. An override value
is valid even for dry run and one-digit F code feed specification.
In the feed per minute mode, the actual feedrate is as follows:

override)

(feedrate

corners)

inner

for

override

(automatic

5.FEED FUNCTIONS

PROGRAMMING

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Limitation
- Acceleration/deceleration before interpolation

Override for inner corners is disabled during acceleration/deceleration
before interpolation.

- Start-up/G41, G42

Override for inner corners is disabled if the corner is preceded by a
start-up block or followed by a block including G41 or G42.

- Offset

Override for inner corners is not performed if the offset is zero.

5.4.2.2

Internal circular cutting feedrate change

For internally offset circular cutting, the feedrate on a programmed
path is set to a specified feedrate (F) by specifying the circular cutting
feedrate with respect to F, as indicated below (Fig. 5.4.2(e)). This
function is valid in the tool radius compensation mode, regardless of
the G62 code.

Rc : Tool center path radius
Rp : Programmed radius
It is also valid for the dry run and the one-digit F code feed command.

Programmed

Tool center
path

Fig. 5.4.2(e) Internal circular cutting feedrate change

If Rc is much smaller than Rp, Rc/Rp

0; the tool stops. A minimum

deceleration ratio (MDR) is to be specified with parameter No. 1710.
When Rc/Rp

≤

MDR, the feedrate of the tool is (F

MDR).

CAUTION

When internal circular cutting must be performed
together with override for inner corners, the
feedrate of the tool is as follows:

override)

(feedrate

corners)

inner

for the

(override

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PROGRAMMING

5.FEED FUNCTIONS

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5.5

FEEDRATE INSTRUCTION ON IMAGINARY CIRCLE FOR
A ROTARY AXIS

Overview

This function acquires movement feedrate on imaginary circle by
synthetic movement distance is calculated from movement distance of
a rotary axis by using instruction angle and the parameter of an
imaginary radius (No.1465).
Then, movement feedrate on imaginary circle is feedrate of a rotary
axis.

Explanation

Cutting feedrate

- Conventional method

In linear interpolation of a linear axis and a rotary axis, 1deg in
movement angle of a rotary axis is interpolated as 1mm in movement
distance (1inch at inch input).

Program example
N1G91G01X10.F10.;
N2C10.F10.;

It instructs in a instruction feedrate
of a rotary axis at a feedrate of a
rotary axis.

Instruction speed
(deg/min)

Feedrate of liner axis(X axis)

(

)

min

∆

Feedrate of rotary axis(C axis)

(

)

min

deg

∆

Synthetic movement distance

( )

∆

Movement time

)

(

min

- Feedrate instruction on imaginary circle of a rotary axis

In this function, synthetic movement distance is obtained based on
movement distance of a rotary axis requested from instruction angle
and the parameter of an imaginary radius(parameter No.1465).

5.FEED FUNCTIONS

PROGRAMMING

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Instruction
feedrate(mm/min)

Imaginary
radius

半径

Program example
N1G91G01X10.F10.
N2C10.

Instruction feedrate is feedrate of
a rotary axis on imaginary circle in
a radius specified by the
parameter.
Then, feedrate element of a rotary
axis can be excluded by setting 0
in imaginary radius

Feedrate of liner axis(X axis)

(

)

min

′

∆

Feedrate of rotary axis(C axis)

(

)

min

deg

′

∆

Synthetic movement distance

( )

180













∆













∆

′

Movement time

(

)

min

′

，

: imaginary radius(parameter No.1465)

It becomes feedrate from which movement feedrate on imaginary
circle is instructed by this. <Example 1 reference>

In this function, feedrate of a axis becomes

′

times for the

feedrate displayed on the NC screen from difference of the method of
obtaining movement distance. Especially, a movement of a axis
quickens when small value is set to an imaginary radius. Note input of
the parameter enough.
Cutting feedrate is clamped based on the maximum cutting feedrate
parameter (No.1430) and feedrate of an actual axis (data before this
function is converted). Therefore, it is possible to instruct at feedrate
more than setting the maximum cutting feedrate by setting big value in
an imaginary radius (parameter No.1465). When small value is set in
an imaginary radius, it is clamped at the feedrate following setting the
maximum cutting feedrate.
Moreover, dry run becomes effective as for this function, too.

AI Contour Control

AI contour control is done to movement feedrate on imaginary circle.
Therefore, It is likely not to become feedrate in the calculation in this
function by feedrate control of AI contour control. Then, feedrate of
AI contour Control is clamped at parameter(No.1432). Moreover, it is
clamped at parameter(No.8465), When the parameter(No.8465) is not
0.

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PROGRAMMING

5.FEED FUNCTIONS

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0mm in imaginary radius

When an imaginary radius is assumed 0mm, synthesized distance is as
follows because the movement distance of a rotary axis becomes
0mm.

∆

′

A movement feedrate of a linear axis can be instruction feedrate F by
excluding feedrate element of a rotary axis.<Example 2 reference>
Moreover, it moves at the maximum cutting feedrate in case of this
setting and instruction only in a rotary axis.

Examples
- Example 1

When the follwing block is instructed on IS-B,
G91 G01 C10. F10. ;

The calculation is as follows, when 10.000(10mm) is set in an
imaginary radius(parameter No.1465).

(

)

(

)

(

)

(

)

(

)

(

)

(

)

(

min

)

(

)

(

)

(

4719755

17453292

7453292

2957795

7453292

180

sec

min

deg

⋅⋅

⋅

⋅⋅

⋅

⋅⋅

⋅

′

⋅⋅

⋅

⋅⋅

⋅

⋅⋅

⋅

























∆

′

Therefor, the movement time becomes about 10.472(sec), and the
rotation feedrate becomes about 57.296(deg/min). The feedrate on
10.000mm in an imaginary radius becomes 10.000mm/min at
instruction feedrate in Fig.5.5(a).

The calclation is as follows, when 36.000(36mm) is set in an
imaginary radius(parameter No.1465).

(

)

(

)

(

)

(

)

(

)

(

)

(

)

(

)

(

)

(

)

(

6991118

628318530

28318530

9154943

28318530

180

sec

min

deg

min

deg

⋅⋅

⋅

⋅⋅

⋅

⋅⋅

⋅

′

⋅⋅

⋅

⋅⋅

⋅

⋅⋅

⋅

























∆

′

Therefor, the movement time becomes about 37.700(sec), and the
rotation feedrate becomes about 15.915(deg/min). The feedrate on
36.000mm in an imaginary radius becomes 10.000mm/min at
instruction feedrate in Fig.5.5(a).

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