FANUC Series 30i-MODEL B, 31i-MODEL B, 32i-MODEL B. For Machining Center System. OPERATOR'S MANUAL

6.COMPENSATION FUNCTION

PROGRAMMING

B-64484EN-2/02

Linear→Linear

(Circular

connection type)

Workpiece

Programmed path

Tool center path

Linear→Circular

(Circular

connection type)

Work-

piece

Tool center path

Programmed path

Circular→Linear

(Circular

connection type)

Workpiece

Programmed path

Tool center path

Circular→Circular

(Circular

connection type)

Programmed path

Work-

piece

Tool center path

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6.COMPENSATION FUNCTION

Tool movement around the outside corner at an acute angle (α<90°)

Linear→Linear

(Linear

connection type)

Workpiece

Programmed path

Tool center path

Linear→Circular

(Linear

connection type)

Work-

piece

Programmed path

Tool center path

Circular→Linear

(Linear

connection type)

Workpiece

Programmed path

Tool center path

Circular→Circular

(Linear

connection type)

Work-

piece

Tool center path

Programmed path

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6.COMPENSATION FUNCTION

PROGRAMMING

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Linear→Linear

(Circular

connection type)

Workpiece

Programmed path

Tool center path

Linear→Circular

(Circular

connection type)

Work-

piece

Programmed path

Tool center path

Circular→Linear

(Circular

connection type)

Workpiece

Programmed path

Tool center path

Circular→Circular

(Circular

connection type)

Work-

piece

Tool center path

Programmed path

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PROGRAMMING

6.COMPENSATION FUNCTION

When it is exceptional

End point for the arc is not on the arc

If the end of a line leading to an arc is not on the arc, the system assumes that the cutter compensation has

been executed with respect to an imaginary circle that has the same center as the arc and passes the

specified end point. Based on this assumption, the system creates a vector and carries out compensation.

The same description applies to tool movement between two circular paths.

End the arc

Work-

piece

Imaginary circle

Programmed path

Tool center path

Center of the arc

L S

There is no inner intersection

If the tool radius / tool nose radius compensation value is sufficiently small, the two circular tool center

paths made after compensation intersect at a position (P). Intersection P may not occur if an excessively

large value is specified for tool radius ⋅ tool nose radius compensation. When this is predicted, PS0033

occurs at the end of the previous block and the tool is stopped.

For example, tool center paths along arcs A and B intersect at P when a sufficiently small value is

specified for tool radius ⋅ tool nose radius compensation. If an excessively large value is specified, this

intersection does not occur.

Alarm occurs and the tool stops

When the cutter or tool nose radius

compensation value is large

When the cutter or tool nose radius

compensation value is small

Center of the arc B

Center of the arc A

Programmed path

Arc A

Arc B

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6.COMPENSATION FUNCTION

PROGRAMMING

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When the center of the arc is identical with the start point or the end point

If the center of the arc is identical with the start point or end point, PS0041 is displayed, and the tool will

stop at the start point of the preceding block of the arc.

(G41)

N5 G91 G01 X50.0 ;

Tool center path

N6 X50.0 ;

N7 G02 X100.0 I0 J0 ;

Alarm is displayed and the

N8 G01 Y-100.0 ;

tool stops

Programmed path

Change in the offset direction in the offset mode

The offset direction is decided by G codes (G41 and G42) for tool radius ⋅ tool nose radius compensation

and the sign of the compensation value as follows.

Sign of compensation

G code

G41

Left side offset

Right side offset

G42

Right side offset

Left side offset

The offset direction can be changed in the offset mode. If the offset direction is changed in a block, a

vector is generated at the intersection of the tool center path of that block and the tool center path of a

preceding block.

However, the change is not available in the start-up block and the block following it.

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PROGRAMMING

6.COMPENSATION FUNCTION

Tool center path with an intersection

Linear→Linear

Workpiece

G42

Intersection

Programmed path

G41

Tool center path

Workpiece

Linear→Circular

Workpiece

G41

G42

Programmed path

Workpiece

Intersection

Tool center path

Circular→Linear

Workpiece

G42

Programmed path

Tool center path

Intersection

G41

Workpiece

Circular→Circular

Workpiece

G42

Programmed path

G41

Tool center path

Workpiece

Intersection

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6.COMPENSATION FUNCTION

PROGRAMMING

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Tool center path without an intersection

When changing the offset direction in block A to block B using G41 and G42, if intersection with the

offset path is not required, the vector normal to block B is created at the start point of block B.

Linear→Linear

W orkpiece

(G42)

Programmed path

G42

G41

W orkpiece

Tool center path

G42

Programmed path

G41

Tool center path

Linear→Circular

Intersection

Tool center path

(G41)

G42

(G41)

Programmed path

Circular→Circular

An arc whose end position

is not on the arc

G41

(G42)

Programmed path

(G42)

Center

Tool center path

The length of tool center path larger than the circumference of a circle

Normally there is almost no possibility of generating this situation. However, when G41 and G42 are

changed, or when a G40 was commanded with address I, J, and K this situation can occur.

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PROGRAMMING

6.COMPENSATION FUNCTION

The cutter compensation is not performed with more than one circle circumference: an arc is formed from

P₁ to P₂ as shown. Depending on the circumstances, an alarm may be displayed due to the "Interference

Check" described later. To execute a circle with more than one circumference, the circle must be

specified in segments.

Tool center path Programmed path

(G42)

N5 G01 G91 X500.0 Y-700.0 ;

N6 G41 G02 J-500.0 ;

N7 G42 G01 X500.0 Y700.0 ;

Cutter compensation G code in the offset mode

The offset vector can be set to form a right angle to the moving direction in the previous block,

irrespective of machining inner or outer side, by commanding the cutter compensation G code (G41, G42)

in the offset mode, independently. If this code is specified in a circular command, correct circular motion

will not be obtained.

When the direction of offset is expected to be changed by the command of cutter compensation G code

(G41, G42), see "Change in the offset direction in the offset mode".

Linear→Linear

A block specified by G42

G42 mode

Tool center path

Intersection

Circular→Linear

A block specified by G42

G42 mode

Intersection

Programmed path

Command canceling the offset vector temporarily

During offset mode, if G92 (workpiece coordinate system setting) or G52 (local coordinate system

setting) is commanded, the offset vector is temporarily cancelled and thereafter offset mode is

automatically restored.

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6.COMPENSATION FUNCTION

PROGRAMMING

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In this case, without movement of offset cancel, the tool moves directly from the intersecting point to the

commanded point where offset vector is canceled.

Also when restored to offset mode, the tool moves directly to the intersecting point.

Tool center path

Programmed path

G92 block

(G41)

N5 G01 X700.0 Y300.0 ;

N6 X600.0 Y-300.0 ;

N7 G92 X200.0 Y100.0 ;

N8 G01 X800.0 Y400.0 ;

Before specifying G28 (reference position return), G29 (movement from reference position), G30 (second,

third, and fourth reference position return), G30.1 (floating reference position return), and G53 (machine

coordinate system selection) commands, cancel offset mode, using G40. If an attempt is made to specify

any of the commands in offset mode, the offset vector temporarily disappears.

If I, J, and K are specified in a G00/G01 mode block

At the start of cutter compensation or in that mode, by specifying I, J, and K in a positioning mode (G00)

or linear interpolation mode (G01) block, it is possible to set the compensation vector at the end point of

that block in the direction vertical to that specified by I, J, and K. This makes it possible to change the

compensation direction intentionally.

IJ type vector (XY plane)

The following explains the compensation vector (IJ type vector) to be created on the XY compensation

plane (G17 mode). (The same explanation applies to the KI type vector on the G18 plane and the JK type

vector on the G19 plane.) It is assumed that the compensation vector (IJ type vector) is the vector with a

size equal to the compensation value and vertical to the direction specified by I and J, without performing

intersection calculation on the programmed path. I and J can be specified both at the start of cutter

compensation and in that mode. If they are specified at the start of compensation, any start-up type set in

the appropriate parameter will be invalid, and an IJ type vector is assumed.

Offset vector direction

In G41 mode, the direction specified by I, J, and K is assumed an imaginary tool movement direction, and

an offset vector is created vertical to that direction and on the left side.

Compensation vector

I, J, K

In G42 mode, the direction specified by I, J, and K is assumed an imaginary tool movement direction, and

an offset vector is created vertical to that direction and on the right side.

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PROGRAMMING

6.COMPENSATION FUNCTION

I, J, K

Compensation vector

Example

If I and J are specified at the start of compensation (with

tool movement)

N50

N40

(G40)

N30

N10 G91 G41 X100.0 Y100.0

N20

N60

I1 D1 ;

N20 G04 X1000 ;

Tool center path

N30 G01 F1000 ;

N10

N40 S300 ;

N50 M50 ;

Programmed path

N60 X150. ;

Note) In N10, a vector is

specified with a size of D1

in the direction vertical to

the X axis, using I1.

If I and J are specified at the start of compensation

(without tool movement)

(G40)

N30

N10 G41 I1 D1 ;

N20 G91 X100. Y100. ;

Tool nose radius

N30 X150. ;

center path

N20

Note) In N10, a vector is

Programmed path

specified with a size

of D1 in the direction

N10

vertical to the X axis,

using I1.

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6.COMPENSATION FUNCTION

PROGRAMMING

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If I and J are specified at the start of compensation (with

tool movement)

(G17 G41 G91 D1)

N10 G00 X150. J50. ;

N20 G02 I50. ;

(I,J)

N30 G00 X-150. ;

<2>

Note) In N10, a vector is specified

N10

N20

with a size of D1 in the

N30

direction vertical to the Y axis,

<1>

<2>

using J50.

<1> IJ type vector

<2> Vector determined with

intersection calculation

Tool center path

Programmed path

Path determined with

intersection calculation

If I and J are specified in a block without tool movement in

compensation mode

N30

N40

Tool center

S S

path

Start-up/cancel type C

N20

N50

N10 G41 D1 G01 F1000 ;

(I, J)

N20 G91 X100. Y100. ;

Programmed path

N30 I10. ;

N40 X150. ;

N50 G40 ;

N10

Limitation

If an IJ type vector is specified, tool interference may occur due to that vector alone, depending on the

direction. If this occurs, no interference alarm will occur, or no interference avoidance will be performed.

Overcutting may, therefore, result.

Overcutting

(I, J)

Start-up/cancel

Type C

N40

N30

Programmed

N10 G42 D1 F1000 ;

N20

path

N20 G91 X100. ;

N30 X100. Y-100. I10. ;

N50

N10

N40 X100. Y-100. ;

N50 G40 ;

Tool center path

A block without tool movement

The following blocks have no tool movement. In these blocks, the tool will not move even if cutter

compensation is effected.

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PROGRAMMING

6.COMPENSATION FUNCTION

M05 ;

M code output

S21 ;

S code output

G04 X10.0 ;

Dwell

G22 X100000 ;

Machining area setting

G10 L11 P01 R10.0 ;

Cutter compensation value setting/changing

(G17) Z200.0 ;

Move command not included in the offset plane.

G90 ;, O10 ;, N20 ;

G, O, and N codes only

G91 X0 ;

Move distance is zero.

A block without tool movement specified in offset mode

Unless the number of blocks without movement consecutively specified is more than N-2 blocks (where

N is the number of blocks to read in offset mode (parameter No. 19625)) in offset mode, the vector and

the tool center path will be as usual. This block is executed at the single block stop point.

N6 G91 X100.0 Y100.0 ;

Programmed path

N7 G04 X10.0 ;

N8 X100.0 ;

Tool center path

Block N7 is executed here.

In offset mode, the number of blocks without movement consecutively specified must not exceed N-2

(where N is the number of blocks to read in offset mode (parameter No. 19625). If commanded, a vector

whose length is equal to the offset value is produced in a normal direction to tool motion in earlier block,

so overcutting may result.

N6 G91 X100.0 Y100.0 ;

N7,N8

N7 S21 ;

Programmed path

N8 G04 X10.0 ;

N9 X100.0 ;

(No. of blocks to read in

offset mode = 3)

Tool center path

SSS

L Blocks N7 and N8 are executed here.

If an M/G code that suppresses buffering is specified

If an M/G code that suppresses buffering is specified in offset mode, it is no longer possible to read and

analyze subsequent blocks regardless of the number of blocks to read in offset mode, which is determined

by parameter No. 19625. Then, intersection calculation and a interference check, described later, are no

longer possible. If this occurs, overcutting may occur because a vertical vector is output in the

immediately preceding block.

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6.COMPENSATION FUNCTION

PROGRAMMING

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If an M code (M50) that suppresses buffering is not specified

(G42)

Programmed path

N5 G91 G01 X40.0 Y40.0 ;

N6 X40.0 ;

Tool center path

Intersection

If an M code (M50) that suppresses buffering is specified

(G42)

Programmed path

N5 G91 G01 X40.0 Y40.0 ;

N6 M50 ;

N7 X40.0 ;

Tool center path

Block N6 is executed here.

Workpiece coordinate system or local coordinate system command in the

offset mode

If the local coordinate system (G52) or workpiece coordinate system (G92) is specified in the cutter

compensation (G41 or G42) or 3-dimensional cutter compensation (G41.2 to G41.6 or G42.2 to G42.6)

mode, G52 or G92 is assumed to be a buffering masked G code. The subsequent blocks are not executed

until the G52 or G92 block is executed.

Corner movement

When two or more offset vectors are produced at the end of a block, the tool moves linearly from one

vector to another. This movement is called the corner movement.

If these vectors almost coincide with each other (the distance of corner movement between the vectors is

judged short due to the setting of parameter No. 5010), corner movement is not performed. In this case,

the vector to the single block stop point takes precedence and remains, while other vectors are ignored.

This makes it possible to ignore the very small movements arising from performing cutter compensation,

thereby preventing velocity changes due to interruption of buffering.

ΔV_X

This vector is ignored, if

ΔV_X≤ ΔV_limitand

ΔV_Y≤ ΔV_limit

ΔV_Y

The vector to the single block

stop point remains even if

ΔV_X ≤ ΔV_limit and ΔV_Y ≤ V_limit.

Tool center path

Programmed path

ΔV_limit is determined with the setting of parameter (No. 5010).

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PROGRAMMING

6.COMPENSATION FUNCTION

If the vectors are not judged to almost coincide (therefore, are not erased), movement to turn around the

corner is performed. The corner movement that precedes the single block stop point belongs to the

previous block, while the corner movement that succeeds the single block stop point belongs to the latter

block.

This move belongs to block N6, thus, the feedrate is equal

to that in block N6.

This move belongs to block N7, thus, the

feedrate is equal to that in block N7.

However, if the path of the next block is semicircular or more, the above function is not performed.

The reason for this is as follows:

P₂ P₃ P₄ P5

N4 G41 G91 G01 X150.0 Y200.0 ;

N5 X150.0 Y200.0 ;

N6 G02 J-600.0 ;

N7 G01 X150.0 Y-200.0 ;

P₁

P₆

N8 G40 X150.0 Y-200.0 ;

N₅ N7

N₄

N₈

N₆

Programmed path

Tool center path

If the vector is not ignored, the tool path is as follows:

P₁ → P₂ → P₃ → (Circle) → P₄ → P₅ → P₆

But if the distance between P₂ and P₃ is negligible, the point P₃ is ignored. Therefore, the tool path is as

follows:

P₂ → P₄

Namely, circle cutting by the block N6 is ignored.

Interruption of manual operation

For manual operation during the offset mode, see "Manual Absolute ON and OFF."

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PROGRAMMING

6.COMPENSATION FUNCTION

If the cancel block is a block with tool movement, and the tool moves around

the outside at an obtuse angle (90° ≤ α < 180°)

Tool path has two types A and B, and they are selected by bit 0 (SUP) of parameter No. 5003.

Linear→Linear

G40

Workpiece

Programmed path

Tool center path L

Type

Circular→Linear

G40

Work-

piece

Programmed path

Tool center path

Linear→Linear

(Linear

connection type)

G40

Workpiece

Programmed path

Tool center path

Intersection

Type

Circular→Linear

(Linear

connection type)

G40

Work-

piece

Inter-

section

Programmed path

Tool center path

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PROGRAMMING

6.COMPENSATION FUNCTION

If the cancel block is a block with tool movement, and the tool moves around

the outside at an acute angle (α<90°)

Tool path has two types A and B, and they are selected by bit 0 (SUP) of parameter No. 5003.

Linear→Linear

G40

W orkpiece

Programmed path

G42

Tool center path

Type

Circular→Linear

G40

W ork-

piece

G42

Tool center path

Programmed path

Linear→Linear

(Linear

connection type)

W orkpiece

G40

Programmed path

Tool center path

Type

Circular→Linear

(Linear

connection type)

W ork-

piece

Tool center path

Programmed path

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6.COMPENSATION FUNCTION

PROGRAMMING

B-64484EN-2/02

Linear→Linear

(Circular

connection type)

Workpiece

G40

Programmed path

Tool center path

Type

Circular→Linear

(Circular

connection type)

Work-

piece

Tool center path

Programmed path

If the cancel block is a block with tool movement, and the tool moves around

the outside at an acute angle of 1 degree or less in a linear → linear manner

(α≤1°)

Tool center path

Programmed path

(G42)

1° or less

G40

A block without tool movement specified together with offset cancel

For types A and B

In the block preceding the cancel block, a vector is created with a size equal to the tool radius ⋅ tool

nose radius compensation value in the vertical direction. The tool does not operate in the cancel

block. The remaining vectors are canceled with the next move command.

N6 G91 X100.0 Y100.0 ;

N7 G40 ;

N8 X130.0 ;

Programmed path

Tool center path

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PROGRAMMING

6.COMPENSATION FUNCTION

For type C

The tool shifts by the compensation value in the direction vertical to the block preceding the cancel

block.

Programmed path

Tool center path

G40 (without

movement)

Block containing G40 and I_J_K_

The previous block contains G41 or G42

If a G41 or G42 block precedes a block in which G40 and I_, J_, K_ are specified, the system assumes

that the path is programmed as a path from the end point determined by the former block to a vector

determined by (I,J), (I,K), or (J,K). The direction of compensation in the former block is inherited.

N1 (G42 mode) ;

In the N1 block, the tool nose radius center moves

towards P.

N2 G40 Xa Yb I_ J_ ;

In the N2 block, the tool nose radius moves towards E.

E(a, b)

(I, J)

G40

Tool center path

(G42) Programamed path

Workpiece

In this case, note that the CNC obtains an intersection of the tool path irrespective of whether inner or

outer side machining is specified.

G40

Tool center path

Programmed path

(G42)

(I, J)

When an intersection is not obtainable, the tool comes to the normal position to the previous block at the

end of the previous block.

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6.COMPENSATION FUNCTION

PROGRAMMING

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G40

Tool center path

(G42) Programmed path

(I, J)

Length of the tool center path larger than the circumference of a circle

In the Example shown below, the tool does not trace the circle more than once. It moves along the arc

from P₁ to P₂. The interference check function described below may raise an alarm.

To make the tool trace a circle more than once, program two or more arcs.

P₁

Tool center path

P₂

Programmed path

(I, J)

(G41)

N5 G01 G91 X100.0 ;

N6 G02 J-60.0 ;

N7 G40 G01 X50.0 Y50.0 I-10.0 J-10.0 ;

6.6.5

Prevention of Overcutting Due to Tool Radius / Tool Nose

Radius Compensation

Explanation

Machining a groove smaller than the diameter of the tool

Since the cutter compensation forces the tool center path to move in the reverse of the programmed

direction, overcutting will result. In this case an alarm is displayed and the CNC stops at the start of the

block.

An alarm is displayed and

Tool center path

the operation stops

Programmed path

Workpiece

Overcutting if the operation would not stop

Fig. 6.6.5 (a) Machining a groove smaller than the diameter of the tool

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PROGRAMMING

6.COMPENSATION FUNCTION

Machining a step smaller than the tool radius

For a figure in which a workpiece step is specified with an arc, the tool center path will be as shown in

Fig. 6.6.5 (b). If the step is smaller than the tool radius, the tool center path usually compensated as

shown in Fig. 6.6.5 (c) may be in the direction opposite to the programmed path. In this case, the first

vector is ignored, and the tool moves linearly to the second vector position. The single block operation is

stopped at this point. If the machining is not in the single block mode, the cycle operation is continued.

If the step is of linear, no alarm will be generated and cut correctly. However uncut part will remain.

Single block stop point

Tool center path

Programmed path

Arc center

Workpiece

Fig. 6.6.5 (b) Machining a step larger than the tool radius

Single block stop point

Linear movement

Tool center path

Path to be taken if

the

Programmed path

vector is not ignored

The first vector is ignored

Arc center

Arc

Workpiece

An overcutting will result if the first vector is not ignored.

However, tool moves linearly.

Fig. 6.6.5 (c) Machining a step smaller than the tool radius

Starting compensation and cutting along the Z-axis

It is usually used such a method that the tool is moved along the Z axis after the cutter compensation

(normally XY plane) is effected at some distance from the workpiece at the start of the machining. In the

case above, if it is desired to divide the motion along the Z axis into rapid traverse and cutting feed,

follow the procedure below.

Let us consider the program in the Fig. 6.6.5 (d), assuming the number of blocks to read in cutter

compensation mode (parameter No. 19625) to be 3.

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6.COMPENSATION FUNCTION

PROGRAMMING

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N1 G91 G00 G41 X500.0 Y500.0 D1 ;

N3 G01 Z-300.0 F100 ;

N6 Y1000.0 F200 ;

After compensation

Workpiece

N3:Move command in Z axis (one block)

Fig. 6.6.5 (d)

In the program example in the Fig. 6.6.5 (d), when executing block N1, blocks N3 and N6 are also

entered into the buffer storage, and by the relationship among them the correct compensation is

performed as in the Fig. 6.6.5 (d).

Then, suppose that the block N3 (move command in Z axis) is divided into N3 and N5 in the Fig. 6.6.5

(e).

N1 G91 G00 G41 X500.0 Y500.0 D1 ;

N3 G01 Z-250.0 ;

N5 G01 Z-50.0 F100 ;

N6 Y1000.0 F200 ;

After compensation

Workpiece

N3, N5:Move command for the Z axis (two blocks)

Fig. 6.6.5 (e)

At this time, because the number of blocks to read is 3, blocks up to N5 can be read at the start of N1

compensation, but block N6 cannot be read. As a result, compensation is performed only on the basis of

the information in block N1, and a vertical vector is created at the end of the compensation start block.

Usually, therefore, overcutting will result as shown in the Fig. 6.6.5 (e).

In such a case, it is possible to prevent overcutting by specifying a command with the exactly the same

direction as the advance direction immediately before movement along the Z axis beforehand, after the

tool is moved along the Z axis using the above rule.

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PROGRAMMING

6.COMPENSATION FUNCTION

N1 G91 G00 G41 X500.0 Y400.0 D1 ;

N2 Y100.0 ;

N3 Z-250.0 ;

N5 G01 Z-50.0 F100 ;

N6 Y1000.0 F200 ;

After compensation

W orkpiece

N3, N5 : Move command for the Z axis (2 blocks)

Fig. 6.6.5 (f)

As the block with sequence N2 has the move command in the same direction as that of the block with

sequence N6, the correct compensation is performed.

Alternatively, it is possible to prevent overcutting in the same way by specifying an IJ type vector with

the same direction as the advance direction in the start-up block, as in N1 G91 G00 G41 X500. Y500. I0

J1 D1;, after the tool has moved along the Z axis.

6.6.6

Interference Check

Tool overcutting is called interference. The interference check function checks for tool overcutting in

advance. However, all interference cannot be checked by this function. The interference check is

performed even if overcutting does not occur.

Explanation

Condition under which an interference check is possible

To perform an interference check, it is necessary to read at least three blocks with tool movement. If,

therefore, three or more blocks with tool movement cannot be read in offset mode because blocks without

tool movement, such as independent auxiliary function and dwell, are specified in succession, excessive

or insufficient cutting may occur because an interference check fails. Assuming the number of blocks to

read in offset mode, which is determined by parameter No. 19625, to be N and the number of commands

in those N blocks without tool movement that have been read to be M, the condition under which an

interference check is possible is

(N - 3) ≥ M.

For example, if the maximum number of blocks to read in offset mode is 8, an interference check is

possible even if up to five blocks without tool movement are specified. In this case, three adjacent blocks

can be checked for interference, but any subsequent interference that may occur cannot be detected.

Interference check method

Two interference check methods are available, direction check and circular angle check. Bit 1 (CNC) of

parameter No. 5008 and bit 3 (CNV) of parameter No. 5008 are used to specify whether to enable these

methods.

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Parameter CNV

Parameter CNC

Operation

An interference check is enabled, and a direction check and a circular

angle check can be performed.

An interference check is enabled, and only a circular angle check is

performed.

An interference check is disabled.

NOTE

There are no settings for performing a direction check only.

Interference reference <1> (direction check)

Assuming the number of blocks to read during cutter compensation to be N, a check is first performed on

the compensation vector group calculated in

(block

1 - block

2) to be output this time and the

compensation vector group calculated in (block N-1 - block N); if they intersect, they are judged to

interfere. If no interference is found, a check is performed sequentially in the direction toward the

compensation vector group to be output this time, as follows:

(Block 1 - block 2) and (block N-2 - block N-1)

(Block 1 - block 2) and (block N-3 - block N-2)

(Block 1 - block 2) and (block 2 - block 3)

Even if multiple number of compensation vector groups are generated, a check is performed on all pairs.

The judgment method is as follows: For a check on the compensation vector group in (block 1 - block 2)

and those in (block N-1 - block N), the direction vector from the specified (end point of block 1) to the

(end point of block N-1) is compared with the direction vector from the (point resulting from adding the

compensation vector to be checked to the end of block 1) to the (point resulting from adding the

compensation vector to be checked to the end of block N-1), and if the direction is 90^o or greater or 270^o

or less, they are judged to intersect and interfere. This is called a direction check.

Example of interference standard <1>

(If the block 1 end-point vector intersects with the block 7 end-point vector)

The direction differs by

180°.

Tool center path

Programmed path

Block 2

Block 7

Block 1

Block 8

Block 3

Block 6

Block 4

Block 5

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Example of interference standard <1>

(If the block 1 end-point vector intersects with the block 2 end-point vector)

Programmed path

Tool center path

Block 1

The directions of

these two paths are

different (180°).

Block 2

Interference reference <2> (circular angle check)

In a check on three adjacent blocks, that is, a check on the compensation vector group calculated on

(block 1 - block 2) and the compensation vector group calculated on (block 2 - block 3), if block 2 is

circular, a check is performed on the circular angle between the start and end points of the programmed

path and the circular angle of the start and end point of the post-compensation path, in addition to

direction check <1>. If the difference is 180^o or greater, the blocks are judged to interfere. This is called a

circular angle check.

Example of <2> (if block 2 is circular and the start point of the post-compensation arc coincide with the

end point)

Tool center path

Programmed path

Block 3

Block 1

Programmed path

Block 2

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When interference is assumed although actual interference does not occur

<1> Depression which is smaller than the tool radius ⋅ tool nose radius compensation value

Programmed

path

Tool center path

Stopped

There is no actual interference, but since the direction programmed in block B is opposite to that of

the path after the cutter compensation, the tool stops and an alarm is displayed.

<2> Groove which is smaller than the tool radius ⋅ tool nose radius compensation value

Programmed

path

Tool center path

Stopped

Like <1>, an alarm is displayed because of the interference as the direction is reverse in block B.

6.6.6.1 Operation to be performed if an interference is judged to

occur

The operation to be performed if an interference check judges that an interference (due to overcutting)

occurs can be either of the following two, depending on the setting of bit 5 (CAV) of parameter No.

19607.

Parameter CAV

Function

Operation

Interference check alarm

An alarm stop occurs before the execution of the block in

function

which overcutting (interference) occurs.

Interference check avoidance

The tool path is changed so that overcutting (interference)

function

does not occur, and processing continues.

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6.6.6.2 Interference check alarm function

Interference other than those between adjacent three blocks

If the end-point vector of block 1 and the end-point vector of block 7 are judged to interfere as shown in

the Fig. 6.6.6.2 (a), an alarm will occur before the execution of block 1 so that the tool stops. In this case,

the vectors will not be erased.

Stopped

Tool center path

Block 1

Block 8

Programmed path

Block 2

Block 7

Block 3

Block 6

Block 4

Block 5

Fig. 6.6.6.2 (a)

Interference between adjacent three blocks

If an interference is judged to occur between adjacent three blocks, the interfering vector, as well as any

vectors existing inside of it, is erased, and a path is created to connect the remaining vectors. In the

Example shown in the Fig. 6.6.6.2 (b), V₂ and V₅ interfere, so that V₂ and V₅ are erased, so are V₃ and V₄,

which are inside of them, and V₁ is connected to V₆. The operation during this time is linear interpolation.

V₆

V₁

V₂

V₅

V₄

V₃

Tool center path

Programmed path

Fig. 6.6.6.2 (b)

If, after vector erasure, the last single vector still interferes, or if there is only one vector at the beginning

and it interferes, an alarm will occur immediately after the start of the previous block (end point for a

single block) and the tool stops. In the Example shown in the Fig. 6.6.6.2 (c), V₂ and V₃ interfere, but,

even after erasure, an alarm will occur because the final vectors V₁ and V₄ interfere.

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Stopped

Tool center path

Programmed path

Fig. 6.6.6.2 (c)

6.6.6.3 Interference check avoidance function

Overview

If a command is specified which satisfies the condition under which the interference check alarm function

generates an interference alarm, this function suppresses the generation of the interference alarm, but

causes a new compensation vector to be calculated as a path for avoiding interference, thereby continuing

machining. For the path for avoiding interference, insufficient cutting occurs in comparison with the

programmed path. In addition, depending on the specified figure, no path for avoiding interference can be

determined or the path for avoiding interference may be judged dangerous. In such a case, an alarm stop

will occur. For this reason, it is not always possible to avoid interference for all commands.

Interference avoidance method

Let us consider a case in which an interference occurs between the compensation vector between (block 1

- block 2) and the compensation vector between (block N-1 - block N). The direction vector from the end

point of block 1 to the end point of block N-1 is called a gap vector. At this time, a post-compensation

intersection vector between (block 1 - gap vector) and a post-compensation intersection vector between

(gap vector - block N) is determined, and a path connecting them is created.

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Post-compensation intersection vector

between gap vector and block 8

between block 1 and gap vector

Movement o f block 7

Post-compensation

path

Gap vector

Block 1

Block 8

Block 2

Block 7

Programmed path

Block 3

Block 6

Block 4

Block 5

In this case, the post-compensation end points of blocks 2 to 6 coincide with the end

point of block 1. Thus, after compensation, blocks 2 to 6 will be blocks without tool

movement.

Fig. 6.6.6.3 (a)

If the post-compensation intersection vector of

(block

1 - gap vector) and the post-compensation

intersection vector of (gap vector - block N) further intersect, vector erasure is first performed in the same

way as in "Interference between adjacent three blocks". If the last vectors that remains still intersects, the

post-compensation intersection vector of (block 1 - block N) is re-calculated.

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FANUC Series 30i-MODEL B, 31i-MODEL B, 32i-MODEL B. For Machining Center System. OPERATOR'S MANUAL - page 8