FANUC Series 30i/300i/300is-MODEL A. Machining Center System. User's manual - page 119

22.5-AXIS MACHINING FUNCTION

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- Interference check when the compensation plane changes

An interference check is made when the compensation plane (a plane
perpendicular to the tool vector) has changed.
Example:
If the following program is executed, an alarm PS0041
(INTERFERENCE IN CUTTER COMPENSATION) is issued at N4:
O100

F3000

N1 G90 G00 X0 Y0 Z0 A-46 C180

N2 G41.2 D1

N3 G01 X100

N4 Y-200 Z-200

A45

N6 Y-400 Z0

N8 Y-200 Z-200

A-46

N10 Y0 Z0

N11

G40

M30

N10

Fig. 22.5.1.1 (j) Conceptual diagram

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Va: Tool vector when A=-46
Vb: Tool vector when A=45
A:    End point of N3
B:    End point of N4
C:    End point of N6

Fig. 22.5.1.1 (k) Tool vector

A’

C’

B’

A’: Point A projected onto the compensation plane
B’: Point B projected onto the compensation plane
C’: Point C projected onto the compensation plane

Fig. 22.5.1.1 (l) Compensation vector at the end point (point B) of N4 (in

the compensation plane)

The movement direction of A'B' is opposite to that of B'C', so two
compensation vectors V1 and V2 are produced at point B' (the end
point of N4). In such a case, there is a possibility of overcutting, so
an alarm PS0041 is issued at N4.

<1> Conditions for issuing the interference alarm

Suppose that a move command for a rotary axis makes the tool
vector change significantly from one block to another. In this
case, an interference alarm is assumed because compensation
vectors are regarded as being generated in wrong directions when
the path angle difference in the compensation plane is large, even
though the angle difference between the directions of
compensation vectors to be generated by those blocks is small.

Here, the compensation plane is perpendicular to the tool
direction (Va in the figure below) of the first of the two blocks.

Specifically, the conditions listed below are used for issuing the
alarm.

22.5-AXIS MACHINING FUNCTION

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Ua: Vector AB
Ub: Vector BC
Va: Tool vector between A and B
Vb: Tool vector between B and C
Wa: Va

Wb: Vb

(Here,

represents an outer product operator.)

Fig. 22.5.1.1 (m) Conceptual diagram

A’: Point A projected onto the compensation plane
B’: Point B projected onto the compensation plane
C’: Point C projected onto the compensation plane
Ra: Vector A’B’
Rb: Vector B’C’

A’

C’

B’

Fig. 22.5.1.1 (n) Programmed path before and after the end point (point

B) of N4 (in the compensation plane)

When all the following conditions are satisfied, an alarm
PS0041) is issued:
(1) The tool vector changes significantly.

: Angle for determination set in parameter No. 19635

(The default is 45

(Va,Vb)

≤

cos(

)(where, (Va,Vb) means an inner product.)

(2) The difference between the directions of the compensation

vectors to be generated is small.
Wa: Direction of a compensation vector to be generated by

block AB

Wb: Direction of a compensation vector to be generated by

block BC

Wa = Va

Wb = Vb

(Wa,Wb)

≥

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(3) The path angle difference in the compensation plane is

large.

(Ra,Rb) < 0

<2> Suppressing the issue of the alarm with a Q command

By inserting a Q command into a block that resulted in the alarm,
the issue of the alarm can be suppressed.
(1) Q1

command

By inserting a Q1 command, a perpendicular vector is
generated.

Example: N4 Y-200 Z-200 Q1

At B', a vector (V) perpendicular to A'B' is generated.

A’

C’

B’

Fig. 22.5.1.1 (o) Q1 command

A perpendicular vector can also be generated by specifying
G41.2 or G42.1 in the next block as follows:

Example: N6 G41.2 Y-400 Z0

(2) Q2

command

With a program specifying a linear-to-linear connection, up
to two compensation vectors are generated. In this case,
the second vector is deleted by inserting a Q2 command.

The Q2 command has no effect on circular interpolation.

Example: N4 Y-200 Z-200 Q2

The second vector (V2) is deleted, and only V1 is used as a compensation vector.

A’

C’

B’

Fig. 22.5.1.1 (p) Q2 command

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(3) Q3

command

By inserting a Q3 command, the issue of the alarm can be
suppressed.

Example: N4 Y-200 Z-200 Q3

The two vectors (V1 and V2) are not deleted.

A’

C’

B’

Fig. 22.5.1.1 (q) Q3 command

- Others

When the tool movement changes linear to circular (helical), circular
(helical) to linear, or circular (helical) to circular (helical), the start,
end, and center points of a circular (helical) movement are projected
on the compensation plane that is perpendicular to the tool axis, and a
compensation vector is calculated in the plane. The obtained vector
is added to the originally specified position to create a position to be
specified. Then, the tool is moved linearly or circularly (helically) to
the created position.

Tool

Tool axis

Start point

End point

Tool

Tool center path created in the compensation plane

(Compensation plane = XY plane)

Compensation vector

created in the

compensation plane

Actual

compensation

vector

Move command

Projected

Fig. 22.5.1.1 (r) Operation during compensation

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- Angle of the rotary axis for type 2 (when the movement range is not specified)

When the direction of the tool is specified by I, J, K, Q for type 2,
more than two pairs of "computed angles" of the rotary axes usually
exist.
The "computed angle" is the candidate angle at which the rotary axis
is to be controlled in the specified tool axis direction.
The "output angle" is determined from the "computed angle" based on
the "output judgment conditions" described below.
The following descriptions assume that there is no movement range
specification (parameter No.19741 - No.19744 = 0).

Tool rotation type or table rotation type machine

<1> The "output angles" are represented by the computed rotary axis

angle pair whose master axis (first rotary axis) moving angle is
smaller.

↓

When the master axis moving angle is the same

↓

<2> The "output angles" are represented by the computed rotary axis

angle pair whose slave axis (second rotary axis) moving angle is
smaller.

↓

When the slave axis moving angle is the same

↓

<3> The "output angles" are represented by the computed rotary axis

angle pair whose master axis (first rotary axis) angle is nearer to 0
degree (multiple of 360 degrees).

↓

When the master axis angle is equally near to 0 degree

↓

<4> The "output angles" are represented by the computed rotary axis

angle pair whose slave axis (second rotary axis) angle is nearer to 0
degree (multiple of 360 degrees).

Composite type machine

<1> The "output angles" are represented by the computed rotary axis

angle pair whose table (second rotary axis) moving angle is smaller.

↓

When the table moving angle is the same

↓

<2> The "output angles" are represented by the computed rotary axis

angle pair whose tool (first rotary axis) moving angle is smaller.

↓

When the tool moving angle is the same

↓

<3> The "output angles" are represented by the computed rotary axis

angle pair whose table (second rotary axis) angle is nearer to 0
degree (multiple of 360 degrees).

↓

When the table angle is equally near to 0 degree

↓

<4> The "output angles" are represented by the computed rotary axis

angle pair whose tool (first rotary axis) angle is nearer to 0 degree
(multiple of 360 degrees).

Fig. 22.5.1.1 (s) Output judgment conditions

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The process of judging whether the moving angle is smaller or larger
as the output judgement condition is called "movement judgement."
When bit 5 (PRI) of parameter No.19608 is 1, the movement
judgements for the first rotary axis and second rotary axis are made in
reverse order.

The "movement judgement" process is explained below.
When the "computed angle" is within the range between 0 and 360
degrees, it is called the "basic computed angle."
Usually, two pairs of "basic computed angles" exist.
For example, assume that a tool rotation type or table rotation type
machine has rotary axis A (master) and rotary axis B (slave) and that
there are two pairs of basic computed angles as follows:
(A

1 degree; B

1 degree)

2 degrees; B

2 degrees) where

≤

The "computed angle" is obtained from either of the following
expressions: "basic computed angle" + 360 degrees

N or "basic

computed angle" - 360 degrees

The current position of rotary axis A (master) is PA, and that of rotary
axis B (slave) is 0 degree.
Based on the PA angle, the "movement judgement" process is done as
follows (when bit 5 (PRI) of parameter No.19608 is 0).

•

Computed angle A

-360

(N + 1) degrees

1 - 360

-360

N degrees

2 - 360

(N + 1)

1 - 360

(N - 1)

(*1)

0 degree

360 degrees

2 - 360

1 + 360

(*2)

360

(N + 1) degrees

1 + 360

360

N degrees

2 + 360

(N - 1)

1 + 360

(N + 1)

(*3)

Fig. 22.5.1.1 (t) Movement judgment

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When the PA angle is (*1):
The output angle is: (A

2 - 360 × (N + 1) degrees; B

2 degrees).

Namely,

2 - 360 × (N + 1) degrees is adopted that is nearer to the

computed angle of A, and

2, which is the same group as

2, is

adopted as the computed angle of B.

When the PA angle is (*2):
The output angle is: (A

1 degrees; B

1 degrees).

Namely,

1 degrees is adopted that is nearer to the computed angle of

A, and

1, which is the same group as

1, is adopted as the computed

angle of B.

When the PA angle is (*3):
The output angle is: (A

2 + 360 × N degrees; B

2 degrees).

Namely,

2 + 360 × N degrees is adopted that is nearer to the

computed angle of A, and

2, which is the same group as

2, is

adopted as the computed angle of B.

When the moving angle of rotary axis A (master) is the same, a
"movement judgement" is made for rotary axis B (slave) according to
the "output judgment conditions."
If the "output angle" of rotary axis A is determined by the "movement
judgement" for rotary axis A, the computed angle representing the
"smaller moving angle" is adopted as the "output angle" of rotary axis
B.
Similarly, if the "output angle" of rotary axis B is determined by the
"movement judgement" for rotary axis B, the computed angle
representing the "smaller moving angle" is adopted as the "output
angle" of rotary axis A.

The "output angle" is explained below using a tool rotation type
machine as an example.
This example illustrates a machine having a "BC type tool axis Z."

•

BC type tool axis Z

C-axis:

First rotation axis
(master)

B-axis: Second rotation axis

(slave)

Fig. 22.5.1.1 (u) BC type tool axis Z

The following two pairs of "computed basic angles" exist that direct
the tool axis toward the +X-axis direction.
(B 90 degrees; C 180 degrees)
(B 270 degrees; C 0 degree)

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