FANUC Series Series 16i-TB, Series 18i-TB, Series 160i-TB, Series 180i-TB. OPERATOR’S MANUAL

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PROGRAMMING

14. COMPENSATION FUNCTION

COMPENSATION FUNCTION

This chapter describes the following compensation functions:

14.1

TOOL OFFSET

14.2

OVERVIEW OF TOOL NOSE RADIUS COMPENSATION

14.3

DETAILS OF TOOL NOSE RADIUS COMPENSATION

14.4

CORNER CIRCULAR INTERPOLATION FUNCTION (G39)

14.5

TOOL COMPENSATION VALUES, NUMBER OF

COMPENSATION VALUES, AND ENTERING VALUES FROM

THE PROGRAM (G10)

14.6

AUTOMATIC TOOL OFFSET (G36, G37)

14.7

COORDINATE ROTATION (G68.1, G69.1)

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Tool offset is used to compensate for the difference when the tool actually

14.1

used differs from the imagined tool used in programming (usually,

TOOL OFFSET

standard tool).

Standard tool

Actual tool

Offset amount

on X axis

Offset amount

on Z axis

Fig. 14.1 Tool offset

In this unit, there is no G code to specify tool offset.

The tool offset is specified by T code.

14.1.1

Tool geometry offset and tool wear offset are possible to divide the tool

offset to the tool geometry offset for compensating the tool shape or tool

Tool Geometry Offset

mounting position and the tool wear offset for compensating the tool nose

and Tool Wear Offset

wear.

Total value of tool geometry offset value and tool wear offset value is set

as the tool wear offset value without option.

NOTE

Tool geometry offset and tool wear offset are optioned.

Point on the program

Imaginary tool

X axis

geometry

Offset

offset

amount

value

on X axis

X axis

wear

Actual

offset

tool

value

Z axis

wear

geometry

Offset

offset

amount

value

on Z axis

Fig. 14.1.1 (a) Difference the

Fig. 14.1.1 (b) Not difference the

tool geometry offset from tool

wear offset

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14. COMPENSATION FUNCTION

14.1.2

There are two methods for specifying a T code as shown in Table 14.1.2

(a) and Table 14.1.2 (b).

T Code for Tool Offset

Format

D Lower digit of T code

Table 14.1.2 (a)

specifies geometry and

Kind of

Parameter setting for specifying of

wear offset number

Meaning of T code

T code

offset No.

2-digit

T f f

When LD1, bit 0 of

When LGN, bit 1

command

parameter

of parameter

Tool wear and tool

No.5002, is set to

geometry offset

1, a tool wear off-

0, the tool geome-

number

set number is spe-

try offset number

Tool selection

cified with the last

and tool wear off-

digit of a T code.

set number speci-

fied for a certain

4-digit

T ff ff

When LD1, bit 0 of

tool are the same.

command

parameter

Tool wear and tool

No.5002, is set to

geometry offset

0, a tool wear off-

number

set number is spe-

Tool selection

cified with the last

two digits of a T

code.

D Lower digit of T code

Table 14.1.2 (b)

specifies wear offset

Kind of

Parameter setting for specifying of

number and higher digit

Meaning of T code

T code

offset No.

number specifies tool

selection number and

2-digit

When LD1, bit 0 of

When LGN, bit 1

T f f

command

parameter

of parameter

geometry offset number

No.5002, is set to

Tool wear offset

1, a tool wear off-

1, the tool geome-

number

Tool selection and tool

set number is spe-

try offset number

geometry offset num-

cified with the last

and tool wear off-

ber

digit of a T code.

set number speci-

fied for a certain

4-digit

T ff ff

When LD1, bit 0 of

tool are the same.

command

parameter

Tool wear offset

No.5002, is set to

number

0, a tool wear off-

Tool selection and

set number is spe-

tool geometry offset

cified with the last

number

two digits of a T

code.

14.1.3

Tool selection is made by specifying the T code corresponding to the tool

number. Refer to the machine tool builder’s manual for the relationship

Tool Selection

between the tool selection number and the tool.

14.1.4

Tool offset number has two meanings.

It is specifies the offset distance corresponding to the number that is

Offset Number

selected to begin the offset function. A tool offset number of 0 or 00

indicates that the offset amount is 0 and the offset is cancelled.

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14.1.5

There are two types of offset. One is tool wear offset and the other is tool

geometry offset.

Offset

Explanations

D Tool wear offset

The tool path is offset by the X, Y, and Z wear offset values for the

programmed path. The offset distance corresponding to the number

specified by the T code is added to or subtracted from the and position of

each programmed block.

Tool path after offset

This block contains the offset

command with T code

Programmed path

Compensation by offset X, Z (offset vector)

Fig. 14.1.5 (a) Movement of offset (1)

D Offset vector

In Fig. 14.1.5 (a), the vector with offset X, Y, and Z is called the offset

vector. Compensation is the same as the offset vector.

D Offset cancel

Offset is cancelled when T code offset number 0 or 00 is selected. At the

end of the cancelled block, the offset vector becomes 0.

N1 X50.0 Z100.0 T0202 ; Creates the offset vector corresponding

to offset number 02

N2 X200.0 ;

N3 X100.0 Z250.0 T0200 ; Specifying offset number 00 deletes the

offset vector.

Tool path after offset

Programmed path

Fig. 14.1.5 (b) Movement of offset (2)

When the power is first turned on , and the reset key on the MDI units is

pushed or the reset signal is input to the CNC from the machine tool, the

offset is cancelled.

Parameter LVK (No. 5003#6) can be set so that offset will not be cancelled

by pressing the reset key or by reset input.

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D Only T code

When only a T code is specified in a block, the tool is moved by the wear

offset value without a move command. The movement is performed at

rapid traverse rate in the G00 mode . It is performed at feedrate in other

modes.

When a T code with offset number 0 or 00is specified by itself, movement

is performed to cancel the offset.

WARNING

When G50 X_Z_T_ ; is specified

Tool is not moved.

The coordinate system in which the coordinate value of the

tool position is (X,Z) is set. The tool position is obtained by

subtracting the wear offset value corresponding to the offset

number specified in the T code.

With the tool geometry offset, the work coordinate system is shifted by

D Tool geometry offset

the X, Y, and Z geometry offset amounts. Namely, the offset amount

corresponding to the number designated with the code is added to or

subtracted from the current position.

Absolute command

Programmed path after work

coordinate system shift

Tool path after offset

Offset amount by tool

geometry offset in X, Z

axis (offset vector

Programmed path before

work coordinate system shift

Fig. 14.1.5 (c) Movement of tool geometry offset

NOTE

As well as wear offset, the tool can be compensated by

parameter setting LGT(No.5002#4) to add or subtract the

programmed end point of each block.

D Offset cancel

Specifying offset number 0, 00, or 0000 cancels offset.

NOTE

When LGC, bit 5 of parameter No.5002, is set to 0,

specifying offset number 0 or 00 does not cancel offset.

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Examples

1. When a tool geometry offset number and tool wear offset number are

specified with the last two digits of a T code

(when LGN, bit 1 of parameter No. 5002, is set 0),

N1 X50.0 Z100.0 T0202 ; Specifies offset number 02

N2 Z200.0 ;

N3 X100.0 Z250.0 T0200 ; Cancels offset

Absolute command

Offset cancel

Programmed

path after work

coordinate

system shift

Tool path after offset

Offset

NOTE

When LGC, bit 5 of parameter No.5002, is set to 0,

specifying offset number 0 does not cancel tool geometry

offset.

2. Assume that geometry offset is not cancelled with offset No. 0

(Set the parameter (No. 5002#1).)

N1 X50.0 Z100.0 T0202 ; Tool selection number

(specified tool

geometry offset number 02)

N2 Z200.0 ;

N3 X100.0 Z250.0 T0000 ; Cancels offset

Offset cancel

Programmed

path after work

coordinate

system shift

Tool path after offset

Offset

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14.1.6

This section describes the following operations when tool position offset

is applied: G53, G28, G30, and G30.1 commands, manual reference

G53, G28, G30, and

position return, and the canceling of tool position offset with a T00

G30.1 Commands

command.

When Tool Position

Offset is Applied

Explanations

D Reference position

Executing reference position return (G28) or a G53 command when tool

return (G28) and G53

position offset is applied does not cancel the tool position offset vector.

command when tool

The absolute position display is as follows, however, according to the

position offset is applied

setting of bit 4 (LGT) of parameter No. 5002.

LGT = 0 (Tool geometry compensation is based on shift of the coordinate system.)

Tool position offset

Tool geometry

Tool wear

(without option)

compensation

Absolute

Block for reference

The vector is not reflected.

The shift is reflected.

The vector is not reflected.

position

position return or

The coordinates are dis-

Coordinates shifted ac-

The coordinates are dis-

coordinate

G53 command

played as if the offset had

cording to the tool geome-

played as if the offset had

display

been temporarily can-

try compensation are dis-

been temporarily can-

celed.

played.

celed.

Next block

The vector is reflected.

Coordinates shifted ac-

The vector is reflected.

cording to the tool geome-

try compensation are dis-

played.

LGT = 1 (Tool geometry compensation is based on tool movement.)

Tool position offset

Tool geometry

Tool wear

(without option)

compensation

Absolute

Block for reference

The vector is not reflected.

position

position return or

The coordinates are dis-

coordinate

G53 command

played as if the offset had

display

been temporarily can-

celed.

Next block

The vector is reflected.

NOTE

Bit 6 (DAL) of parameter No. 3104 is set to 0 (the actual positions to which the tool position offset

is applied are displayed in the absolute position display).

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D Manual reference

Executing manual reference position return when tool position offset is

position return when tool

applied does not cancel the tool position offset vector. The absolute

position offset is applied

position display is as follows, however, according to the setting of bit 4

(LGT) of parameter No. 5002.

LGT = 0 (Tool geometry compensation is based on shift of the coordinate system.)

Tool position offset

Tool geometry

Tool wear

(without option)

compensation

Absolute

Upon manual refer-

The vector is not reflected.

The shift is reflected.

The vector is not reflected.

position

ence position return

The coordinates are dis-

Coordinates shifted ac-

The coordinates are dis-

coordinate

played as if the offset had

cording to tool geometry

played as if the offset had

display

been temporarily can-

compensation are dis-

been temporarily can-

celed.

played.

celed.

Next block

The vector is reflected.

Coordinates shifted ac-

The vector is reflected.

cording to tool geometry

compensation are dis-

played.

LGT = 1 (Tool geometry compensation is based on tool movement.)

Tool position offset

Tool geometry

Tool wear

(without option)

compensation

Absolute

Upon manual refer-

The vector is not reflected.

position

ence position return

The coordinates are dis-

coordinate

played as if the offset had

display

been temporarily can-

celed.

Next block

The vector is reflected.

NOTE

Bit 6 (DAL) of parameter No. 3104 is set to 0 (the actual positions to which the tool position offset

is applied are displayed in the absolute position display).

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D Canceling tool position

Whether specifying T00 alone, while tool position offset is applied,

offset with T00

cancels the offset depends on the settings of the following parameters:

When the tool geometry/wear compensation option is selected

LGN = 0

LGN (No.5002#1)

LGT (No.5002#4)

LGC (No.5002#5)

The geometry offset number is:

Geometry compensation is applied:

The geometry offset is:

Result

0: Same as the wear offset

0: Based on shift of the

0: Not canceled with T00

number

coordinate system

1: Canceled with T00

1: Same as the tool selection

1: Based on movement of the tool

number

LGT=0

LGC=0

Not canceled

LGC=1

Canceled

LWM (No.5002#6)

Tool position offset is applied:

0: By means of T code

1: By means of movement

along axis

LGT=1

LWM=0

Canceled

LWM=1

Not canceled

NOTE

When LGT=0, LWM is unrelated.

When LGT=1, LGC is unrelated, even when LGN = 0.

LGN = 1

LGN (No.5002#1)

LGT (No.5002#4)

LGC (No.5002#5)

The geometry offset number is:

Geometry compensation is applied:

The geometry offset is:

Result

0: Same as the wear offset

0: Based on shift of the

0: Not canceled with T00

number

coordinate system

1: Canceled with T00

1: Same as the tool selection

1: Based on movement of the tool

number

LGT=0

LGC is unrelated.

Canceled

LWM (No.5002#6)

Tool position offset is applied:

0: By means of T code

1: By means of movement

along axis

LGT=1

LWM=0

Canceled

LWM=1

Not canceled

NOTE

When LGT = 0, LWM is unrelated.

When LGT = 1, LGC is unrelated.

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When the tool geometry/wear compensation option is not selected

LGN (No.5002#1)

LGT (No.5002#4)

LGC (No.5002#5)

The geometry offset number is:

Geometry compensation is

The geometry offset is:

Result

0: Same as the wear offset

applied:

0: Not canceled with T00

number

0: Based on shift of the

1: Canceled with T00

1: Same as the tool selection

coordinate system

number

1: Based on movement of the

tool

LGN is unrelated.

LGT is unrelated.

LGC is unrelated.

The tool position offset number

Tool position offset is always

LWM (No.5002#6)

always uses the low-order digits.

applied based on the movement

of the tool.

Tool position offset is applied:

0: By means of T code

1: By means of movement

along axis

LWM=0

Canceled

LWM=1

Not canceled

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14. COMPENSATION FUNCTION

It is difficult to produce the compensation necessary to form accurate parts

14.2

when using only the tool offset function due to tool nose roundness in

OVERVIEW OF TOOL

taper cutting or circular cutting. The tool nose radius compensation

NOSE RADIUS

function compensates automatically for the above errors.

COMPENSATION

Workpiece

Tool path without compensation

Tool path with compensation

ÇÇ

Insufficient

ÇÇ

Tool nose

depth of

ÇÇÇ

cutting

ÇÇÇÇ

Shape processed without tool

nose radius compensation

Fig 14.2 Tool path of tool nose radius compensation

14.2.1

The tool nose at position A in following figure does not actually exist.

The imaginary tool nose is required because it is usually more difficult to

Imaginary Tool Nose

set the actual tool nose radius center to the start position than the

imaginary tool nose (Note).

Also when imaginary tool nose is used, the tool nose radius need not be

considered in programming.

The position relationship when the tool is set to the start position is shown

in the following figure.

Start position

When programmed using the

tool nose center

imaginary tool nose

Fig. 14.2.1 (a) Tool nose radius center and imaginary tool nose

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CAUTION

In a machine with reference positions, a standard position like the turret center can be placed

over the start position. The distance from this standard position to the nose radius center or

the imaginary tool nose is set as the tool offset value.

Setting the distance from the standard position to the tool nose radius center as the offset

value is the same as placing the tool nose radius center over the start position, while setting

the distance from the standard position to the imaginary tool nose is the same as placing the

imaginary tool nose over the standard position. To set the offset value, it is usually easier to

measure the distance from the standard position to the imaginary tool nose than from the

standard position to the tool nose radius center.

OFX

(Tool offset

in X axis)

OFZ

(Tool offset

in Z axis)

Setting the distance from the standard position

Setting the distance from the standard position to

to the tool nose center as the tool offset value

the imaginary tool nose center as the tool offset

value

The start position is placed over the tool nose center The start position is placed over the imaginary tool

nose

Fig. 14.2.1 (b) Tool offset value when the turret center is placed over the start position

Unless tool nose radius compensation is

If tool nose radius compensation is used, accu-

performed, the tool nose center path is the

rate cutting will be performed.

same as the programmed path.

Start-

Tool nose center path

Programmed path

Fig. 14.2.1 (c) Tool path when programming using the tool nose center

Without tool nose radius compensation, the

With tool nose radius compensation, accurate

imaginary tool nose path is the same as the

cutting will be performed.

programmed path.

Imaginary tool

nose path

Start-

Programmed path

Fig. 14.2.1 (d) Tool path when programming using the imaginary tool nose

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14.2.2

The direction of the imaginary tool nose viewed from the tool nose center

is determined by the direction of the tool during cutting, so it must be set

Direction of Imaginary

in advance as well as offset values.

Tool Nose

The direction of the imaginary tool nose can be selected from the eight

specifications shown in the Fig.

14.2.2 below together with their

corresponding codes.

This Fig 14.2.2 illustrates the relation between the tool and the start

position. The following apply when the tool geometry offset and tool

wear offset option are selected.

Imaginary tool nose number 1

Imaginary tool nose number 2

Imaginary tool nose number 3

Imaginary tool nose number 4

Imaginary tool nose number 5

Imaginary tool nose number 6

Imaginary tool nose number 7

Imaginary tool nose number 8

Fig. 14.2.2 Direction of imaginary tool nose

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Imaginary tool nose numbers 0 and 9 are used when the tool nose center

coincides with the start position. Set imaginary tool nose number to

address OFT for each offset number.

Bit 7 (WNP) of parameter No. 5002 is used to determine whether the tool

geometry offset number or the tool wear offset number specifies the

direction of the virtual tool nose for tool nose radius compensation.

Imaginary tool nose number 0 to 9

Limitations

D Plane selection

Virtual tool nose directions 1 to 8 can be used only in the G18 (Z-X) plane.

For virtual tool nose 0 or 9, compensation is applied in both the G17 and

G19 planes.

14.2.3

Offset Number and

Offset Value

Explanations

D Offset number and offset

value

Tool nose radius compensation value

(Tool nose radius value)

This value is set from the MDI according to the offset number.

When the options of tool geometry compensation and tool wear

compensation are selected, offset values become as follows :

Table 14.2.3 (a) Offset number and offset value

OFR

OFT

OFX

OFZ

(Tool nose

OFY

(Direction

Offset

(Offset

radius

(Offset

of imagi-

number

value on X

value on Z

com-

value on Y

nary tool

axis)

pensation

axis)

nose)

value)

0.040

0.020

0.20

0.030

0.060

0.030

0.25

0.040

0.050

0.015

0.12

0.025

0.030

0.025

0.24

0.035

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When the options of tool geometry compensation and tool wear

compensation are selected, the offset values become as follows :

Table 14.2.3 (b) Tool geometry offset

OFGX

OFGZ

OFGR

OFGY

Geome-

OFT

(X-axis

(Z-axis

(Tool nose

(Y-axis

try

(Imaginary

geometry

radius ge-

geometry

offset

tool nose

offset

ometry off-

offset

number

direction)

amount)

set value)

amount)

G01

10.040

50.020

70.020

G02

20.060

30.030

90.030

G03

0.20

G04

G05

Table 14.2.3 (c) Tool wear offset

OFGR

OFGX

OFGZ

OFT

OFGY

Wear

(Tool nose

(X-axis

(Z-axis

(Imaginary

(Y-axis

offset

radius

wear offset

tool nose

wear offset

number

wear offset

amount)

direction)

amount)

value)

W01

0.040

0.020

0.010

W02

0.060

0.030

0.020

W03

0.20

W04

W05

D Tool nose radius

In this case, the tool nose radius compensation value is the sum of the

compensation

geometry or the wear offset value.

OFR=OFGR+OFWR

D Imaginary tool nose

The imaginary tool nose direction may be set for either the geometry

direction

offset or the wear offset.

However, the last designated direction later is effective.

D Command of offset value

A offset number is specified with the same T code as that used for tool

offset. For details, see Subsec. II-14.1.2.

NOTE

When the geometry offset number is made common to the

tool selection by the parameter LGT(No.5002#1)setting

and a T code for which the geometry offset and wear offset

number differ from each other is designated, the imaginary

tool nose direction specified by the geometry offset number

is valid.

Example)

T0102

OFR=RFGR₀₁+OFWR₀₂

OFT=OFT₀₁

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D Setting range of offset

The range of the offset value is an follows :

value

Increment system

metric system

Inch system

IS-B

0 to "999.999 mm

0 to "99.9999 inch

IS-C

0 to "999.9999 mm

0 to "99.99999 inch

The offset value corresponding to the offset number 0 is always 0.

No offset value can be set to offset number 0.

14.2.4

In tool nose radius compensation, the position of the workpiece with

respect to the tool must be specified.

Work Position and

Move Command

G code

Workpiece position

Tool path

G40

(Cancel)

Moving along the programmed path

G41

Right side

Moving on the left side the programmed

path

G42

Left side

Moving on the right side the programmed

path

The tool is offset to the opposite side of the workpiece.

X axis

G42

Z axis

Workpiece

G41

The imaginary tool nose is

on the programmed path.

G40

Imaginary tool nose

Imaginary tool

number 1 to 8

nose number 0

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The workpiece position can be changed by setting the coordinate system

as shown below.

Z axis

G41 (the workpiece is

on the left side)

X axis

Workpiece

G42 (the workpiece is

Note

on the right side)

NOTE

If the tool nose radius compensation value is negative, the

workpiece position is changed.

G40, G41, and, G42 are modal.

Don’t specify G41 while in the G41 mode. If you do, compensation will

not work properly.

Don’t specify G42 while in the G42 mode for the same reason.

G41 or G42 mode blocks in which G41 or G42 are not specified are

expressed by (G41) or (G42) respectively.

D Tool movement when the

When the tool is moving, the tool nose maintains contact with the

workpiece position does

workpiece.

not change

(G42)

Enlarged

diagram

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D Tool movement when the

The workpiece position against the toll changes at the corner of the

workpiece position

programmed path as shown in the following figure.

changes

Workpiece

G41

position

G42

Workpiece

position

G41

G42

Although the workpiece does not exist on the right side of the

programmed path in the above case. the existence of the workpiece is

assumed in the movement from A to B. The workpiece position must not

be changed in the block next to the start-up block. In the above example,

if the block specifying motion from A to B were the start-up block, the

tool path would not be the same as the one shown.

D Start-up

The block in which the mode changes to G41 or G42 from G40 is called

the start-up block.

G40 _ ;

G41 _ ; (Start-up block)

Transient tool movements for offset are performed in the start-up block.

In the block after the start-up block, the tool nose center is positioned

Vertically to the programmed path of that block at the start position.

G40

(G42)

G42 (Start-up)

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D Offset cancel

The block in which the mode changes to G40 from G41 or G42 is called

the offset cancel block.

G41 _ ;

G40 _ ; (Offset cancel block)

The tool nose center moves to a position vertical to the programmed path

in the block before the cancel block. The tool is positioned at the end

position in the offset cancel block (G40) as shown below.

End position

G40

(G42)

D Specification of G41/G42

When is specified again in G41/G42 mode , the tool nose center is

in G41/G42 mode

positioned vertical to the programmed path of the preceding block at the

end position of the preceding block.

(G42)

G42 W-500.0 U-500.0 ;

In the block that first specifies G41/G42, the above positioning of the tool

nose center is not performed.

D Tool movement when the

When you wish to retract the tool in the direction specified by X(U) and

moving direction of the

Z(W) cancelling the tool nose radius compensation at the end of

tool in a block which

machining the first block in the figure below, specify the following :

includes a G40

G40 X(U) _ Z(W) _ I _ K _ ;

command is different

from the direction of the

I, K

Moving direction of tool

workpiece

U, W

G40

G42

G40 U_ W_ I_ K_ ;

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The workpiece position specified by addresses I and K is the same as that

in the preceding block. If I and/or K is specified with G40 in the cancel

mode, the I and/or K is ignored.

G40 X_ Z_ I_ K_ ;

Tool nose radius compensation

G40 G02 X_ Z_ I_ K_ ;

Circular interpolation

G40 G01 X_ Z_ ;

G40 G01 X_ Z_ I_ K_ ; Offset cancel mode (I and k are ineffective.)

The numeral s followed I and K should always be specified as radius

values.

Examples

(3)

f300

(1)

(2)

200

f60

120

150

(G40 mode)

1.G42 G00 X60.0 ;

2.G01 X120.0 W-150.0 F10 ;

3.G40 G00 X300.0 W150.0 I40.0 K-30.0 ;

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14. COMPENSATION FUNCTION

14.2.5

Notes on Tool Nose

Radius Compensation

Explanations

D Tool movement when

1.M05 ;

M code output

two or more blocks

2.S210 ;

S code output

without a move

3.G04 X1000 ;

Dwell

command should not be

4.G01 U0 ;

Feed distance of zero

programmed

5.G98 ;

G code only

consecutively

6.G10 P01 X10.0 Z20.0 R0.5 Q2 ; Offset change

If two or more of the above blocks are specified consecutively, the tool

nose center comes to a position vertical to the programmed path of the

preceding block at the end of the preceding block. However, if the no

movement commands is 4 above, the above tool motion is attained only

with one block.

(G42 mode)

Programmed path

N6 W1000.0 ;

N7 S21 ;

N7 N8

N8 M04 ;

U9 U-1000.0 W1000.0 ;

Tool nose center path

D Tool nose radius

Tool nose radius compensation with G90

(outer diameter/internal

compensation with G90

diameter cutting cycle) or G94 (end face turning cycle) is as follows, :

or G94

1. Motion for imaginary tool nose numbers

For each path in the cycle, the tool nose center path is generally parallel

to the programmed path.

G90

G94

Tool nose center path

4, 8, 3

5, 0, 7

1, 6, 2

In all case

1, 4, 5

8, 0, 6

1, 4, 5

8, 0, 6

In all

3, 7, 2

case

Programmed path

3, 7, 2

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2. Direction of the offset

The offset direction is indicated in the figure below regardless of the

G41/G42 mode.

G90

G94

D Tool nose radius

When one of following cycles is specified, the cycle deviates by a tool

compensation with G71

nose radius compensation vector. During the cycle, no intersection

to G76 or G78

calculation is performed.

G71 (Stock removal in turning or traverse grinding cycle)

G72 (Stock removal in facing or traverse direct constant-dimension

grinding cycle)

G73 (Pattern repeating or Oscillation grinding cycle)

G74 (End face peck drilling)

G75 (Outer diameter/internal diameter drilling)

G76 (Multiple threading cycle)

G78 (Threading cycle)

D Tool nose radius

Movement after after compensation is shown below.

compensation when

chamfering is performed

(G42)

Programmed path

(G41)

D Tool nose radius

Movement after compensation is shown below.

compensation when a

corner arc is inserted

(G42)

Programmed path

(G41)

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This section provides a detailed explanation of the movement of the tool

14.3

for tool nose radius compensation outlined in Section 14.2.

DETAILS OF TOOL

This section consists of the following subsections:

NOSE RADIUS

COMPENSATION

14.3.1

General

14.3.2

Tool Movement in Start-up

14.3.3

Tool Movement in Offset Mode

14.3.4

Tool Movement in Offset Mode Cancel

14.3.5

Interference Check

14.3.6

Overcutting by Tool Nose Radius Compensation

14.3.7

Correction in Chamfering and Corner Arcs

14.3.8

Input Command from MDI

14.3.9

General Precautions for Offset Operations

14.3.10 G53, G28, G30, and G30.1 Commands in Tool-tip Radius

Compensation Mode

14.3.1

General

D Tool nose radius center

The tool nose radius center offset vector is a two dimensional vector equal

offset vector

to the offset value specified in a T code, and the is calculated in the CNC.

Its dimension changes block by block according to tool movement.

This offset vector (simply called vector herein after) is internally crated

by the control unit as required for proper offsetting and to calculate a tool

path with exact offset (by tool nose radius) from the programmed path.

This vector is deleted by resetting.

The vector always accompanies the tool as the tool advances.

Proper understanding of vector is essential to accurate programming.

Read the description below on how vectors are created carefully.

D G40, G41, G42

G40, G41 or G42 is used to delete or generate vectors.

These codes are used together with G00, G01, G02, G03 or G33 to specify

a mode for tool motion (Offsetting).

G code

Function

Workpiece position

G40

Tool nose radius compensation cancel

Neither

G41

Left offset along tool path

Right

G42

Right offset along tool path

Left

G41 and G42 specify an off mode, while G40 specifies cancellation of the

offset.

D Cancel mode

The system enters the cancel mode immediately after the power is turned

on, when the RESET button on the MDI is pushed or a program is forced

to end by executing M02 or M30. (the system may not enter the cancel

mode depending on the machine tool.) In the cancel mode, the vector is

set to zero, and the path of the center of tool nose coincides with the

programmed, path. A program must end in cancel mode. If it ends in the

offset mode, the tool cannot be positioned at the end point, and the tool

stops at a location the vector length away from the end point.

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14. COMPENSATION FUNCTION

D Start-up

When a block which satisfies all the following conditions is executed in

cancel mode, the system enters the offset mode. Control during this

operation is called start-up.

D G41 or G42 is contained in the block, or has been specified to set the

system enters the offset mode. Control during this operation is called

start-up.

D The offset number for tool nose radius compensation is not 00.

D X or Z moves is specified in the block and the move distance is not

zero.

A circular command (G02 or G03) is not allowed in start-up.

If specified, P/S alarm (PS34) will occur. Two blocks are read in during

start- up. The first block is executed, and the second block is entered into

the tool nose radius compensation buffer. In the single block mode, two

blocks are read and the first block is executed, then the machine stops.

In subsequent operations, two blocks are read in advance, so the CNC has

the block currently being executed, and the next two blocks.

D Inner side and outer side

When an angle of intersection created by tool paths specified with move

commands for two blocks is over 180°, it is referred to as “inner side.”

When the angle is between 0° and 180°, it is referred to as “outer side.”

Inner side

Outer side

Programmed path

Workpiece

Programmed path

180°xα

0°xα<180°

D Meaning of symbols

The following symbols are used in subsequent figures:

- S indicates a position at which a single block is executed once.

- SS indicates a position at which a single block is executed twice.

- SSS indicates a position at which a single block is executed three times.

- L indicates that the tool moves along a straight line.

- C indicates that the tool moves along an arc.

- r indicates the tool nose radius compensation value.

- An intersection is a position at which the programmed paths of two

blocks intersect with each other after they are shifted by r.

- indicates the center of the tool nose radius.

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14.3.2

When the offset cancel mode is changed to offset mode, the tool moves

as illustrated below (start-up):

Tool Movement in

Start-up

Explanations

D Tool movement around

an inner side of a corner

Linear→Linear

(180°xα)

Workpiece

Programmed path

G42

Tool nose radius center path

Start position

Linear→Circular

G42

Work-

piece

Tool nose radius

Programmed path

Start position

center path

D Tool movement around

the outside of a corner at

Linear→Linear

Start position

an obtuse angle

G42

(90°xα<180°)

Workpiece

Programmed path

Tool nose radius center path

Intersection

Linear→Circular

Start position

G42

Work-

piece

Intersection

Tool nose radius

Programmed path

center path

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14. COMPENSATION FUNCTION

D Tool movement around

the outside of an acute

Linear→Linear

Start position

angle (α<90°)

G42

Workpiece

Programmed path

Tool nose radius center path

Linear→Circular

Start position

G42

Work-

piece

Tool nose radius

center path

Programmed path

D Tool movement around

the outside linear→linear

Tool nose radius center path

at an acute angle less

than 1 degree

(α<1°)

Programmed path

G41

Start position

Less than 1 deg

D A block without tool

If the command is specified at start-up, the offset vector is not created.

movement specified at

G91 G40 … ;

start-up

N6 U100.0 W100.0 ;

N7 G41 U0 ;

N8 U-100.0 ;

N9 U-100.0 W100.0 ;

Tool nose radius

center path

Programmed path

NOTE

For the definition of blocks that do not move the tool, see

Subsec. II-14.3.3.

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14. COMPENSATION FUNCTION

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14.3.3

In the offset mode, the tool moves as illustrated below:

Tool Movement in

Offset Mode

Explanations

D Tool movement around

the inside of a corner

Linear→Linear

(180°xα)

Workpiece

Programmed path

Tool nose radius center path

Intersection

Linear→Circular

Work-

piece

Intersection

Tool nose radius

Programmed path

center path

Circular→Linear

Workpiece

Programmed path

Tool nose radius center path

Intersection

Circular→Circular

Work-

Intersection

piece

Programmed path

Tool nose radius

center path

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D Tool movement around

the outside corner at an

Linear→Linear

obtuse angle

(90°xα<180°)

Workpiece

Programmed path

Tool nose radius center path

Intersection

Linear→Circular

Work-

piece

Intersection

Programmed path

Tool nose radius

center path

Circular→Linear

Workpiece

Programmed path

Tool nose radius center path

IntersectionSL

Circular→Circular

Programmed path

Work-

piece

Tool nose radius

center path

Intersection

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FANUC Series Series 16i-TB, Series 18i-TB, Series 160i-TB, Series 180i-TB. OPERATOR’S MANUAL - page 9