19.7 ai contour control function/ai nano contour control function

49 Pages·2013·0.57 MB·English

19. HIGH SPEED CUTTING FUNCTIONS PROGRAMMING B–63534EN/02
19.7
AI CONTOUR
CONTROL
FUNCTION/AI NANO
CONTOUR CONTROL
FUNCTION
Overview The AI contour control/AI nano contour control function is provided for
high–speed, high–precision machining. This function enables
suppression of acceleration/deceleration delays and servo delays that
become larger with increases in the feedrate and reduction of machining
profile errors.
Look–ahead acceleration/deceleration before interpolation is enabled for
up to 40 blocks in AI contour control or for up to 180 blocks in AI nano
contour control. This enables execution of smooth acceleration/
deceleration extending over multiple blocks and higher machining.
The AI nano contour control function calculates a position command to
be output to the digital servo in nanometers (nm) with nano–interpolation,
so the machine can be moved smoothly and the surface precision is
improved.
Explanation This function is enabled by setting the AI contour control or AI nano
contour control mode.
(cid:1) Format
G05.1 Q _ ;
Q1 : AI contour control/AI nano contour control mode on
Q0 : AI contour control/AI nano contour control mode off
NOTE
1 Always specify G05.1 in an independent block.
2 The AI contour control/AI nano contour control mode is also
canceled by a reset.
3 When the AI nano contour control option is installed, bit 0
(NAN) of parameter No. 7053 is set to 1 to set the AI contour
control mode.
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B–63534EN/02 PROGRAMMING 19. HIGH SPEED CUTTING FUNCTIONS
(cid:1) Functions valid in the AI The functions listed below are valid in the AI contour control/AI nano
contour control/AI nano contour control mode:
contour control mode
⋅ Nano–interpolation (only in the AI nano contour control mode)
⋅ Look–ahead linear acceleration/deceleration before interpolation
⋅ Look–ahead bell–shaped acceleration/deceleration before interpolation
(The option of look–ahead bell–shaped acceleration/deceleration
before interpolation is required.)
⋅ Automatic corner deceleration
⋅ Feedrate clamping by acceleration
⋅ Feedrate clamping by arc radius
⋅ Block overlap (up to five blocks)
⋅ Advanced preview feed forward
(cid:1) Nano–interpolation (only Nano–interpolation calculates a position command to be output to the
in the AI nano contour digital servo in nanometers (nm) for a conventional program (IS–B or
control mode) IS–C command). Using the calculation results, a smooth position
command is output to the servo, so the machine can be moved smoothly
and the surface precision is improved.
Nano–
NC program interpolation High–precision Servo motor
servo control
Uses a conventional Calculates the
program. position precisely.
Combination with HRV
control improves the
follow–up ability.
NOTE
The positioning precision depends on the detection unit.
(cid:1) Look–ahead linear For a cutting feed command in the feed per minute mode, linear
acceleration/deceleration acceleration/deceleration can be applied before interpolation, that is, for
before interpolation the specified feedrate by reading up to 40 blocks (in the AI contour control
mode) or 180 blocks (in the AI nano contour control mode) in advance.
With acceleration/deceleration after interpolation, the interpolated data is
changed because acceleration/deceleration is applied to the data. With
acceleration/deceleration before interpolation, the interpolated data
cannot be changed by acceleration/deceleration because acceleration/
deceleration is applied to the feedrate data before interpolation. For this
reason, the interpolated data can always be applied to the specified
straight line or curve to eliminate machining profile errors caused by
acceleration/deceleration delays.
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19. HIGH SPEED CUTTING FUNCTIONS PROGRAMMING B–63534EN/02
Linear accelera-
tion/deceleration
before
interpolation
Specified Distribution
Acceleration/
feedrate pulse
Feedrate Interpolation deceleration Servo
calculation calculation after control
interpolation
Linear interpolation,
circular interpolation, etc.
(Example of deceleration)
Deceleration is started in a prior block so that the feedrate specified for
the target block is reached at the execution.
Feedrate
Specified feedrate
Point1
Feedrate determined by
F3 acceleration/deceleration
before interpolation
Point2
F2
F1 Time
N1 N2
To decelerate from feedrate F3 to F2, deceleration must start with point 1.
To decelerate from feedrate F2 to F1, deceleration must start with point 2.
Multiple blocks can be read in advance to perform deceleration extending
over several blocks.
(Example of acceleration)
Acceleration is performed so that the feedrate specified for the target
block is reached at the execution.
Feedrate
Specified feedrate
Feedrate determined by
F3
acceleration/deceleration
before interpolation
F2
F1 Time
N1 N2
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(cid:1) Look–ahead bell–shaped Linear acceleration/deceleration before interpolation for cutting feed in
acceleration/deceleration the AI contour control/AI nano contour control mode can be changed to
before interpolation bell–shaped acceleration/deceleration before interpolation. With
bell–shaped acceleration/deceleration before interpolation, smooth
acceleration/deceleration can be applied to the cutting feedrate to reduce
the shock on the machine by fluctuations in acceleration that are involved
in changes in the cutting feedrate.
To use this function, the option of look–ahead bell–shaped acceleration/
deceleration before interpolation is required.
Feedrate
Linear acceleration/
deceleration
Bell–shaped acceleration/
deceleration
ta Depends on the linear acceleration.
tb Time constant for bell–shaped
acceleration/deceleration
tc Bell–shapedacceleration/
deceleration time
tc = ta + tb
ta is not constant and depends
on the specified feedrate.
Specified feedrate
Time ta =
tb tb tb tb Linear acceleration
tb is constant.
ta ta
tc tc
Acceleration
tb tb
Linear acceleration/
deceleration
Bell–shaped acceleration/
deceleration
ta Depends on the linear acceleration.
Time tb Time constant for bell–shaped
acceleration/deceleration
tc Bell–shapedacceleration/
deceleration time
tb tb 12. tc = ta + tb
ta ta
tc tc
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19. HIGH SPEED CUTTING FUNCTIONS PROGRAMMING B–63534EN/02
When the feedrate is changed, deceleration and acceleration are
performed as follows:
For deceleration:Bell–shaped deceleration is started in the preceding
block so that deceleration terminates by the beginning of the block in
which the feedrate is changed.
For acceleration:Bell–shaped acceleration is started after the
beginning of the block in which the feedrate is changed.
Deceleration
Fa
Fb
Time
N1 N2
Acceleration
Feedrate
Fb
Fa
Time
N1 N2
(cid:1) Automatic corner Between contiguous two blocks, the feedrate difference for an axis may
deceleration exceed the setting (parameter No. 1783). In this case, the feedrate at the
corner is calculated as follows based on the axis for which the ratio of the
actual feedrate difference to the allowable feedrate difference is the
largest. Deceleration is performed so that the feedrate is reached at the
interface of the blocks.
The change in the feedrate for each axis (Vx, Vy, ...) during movement at
the specified feedrate F is compared with the setting of parameter No.
1783 (Vprm–x, Vprm–y, ...). If the change in the feedrate for any axis
exceeds the setting of the parameter, the following expression is used:
! Vx Vy #
Rmax max , ,,,

Vprm x Vprm y
" "
The required feedrate (Fc) is obtained as follows and deceleration is
performed at the corner:
1
Fc F
(cid:1)
Rmax
For example, assume that the tool move direction changes by 90 degrees
from movement along the X–axis to that along the Y–axis. Also assume
that the specified feedrate is 1000 mm/min and the allowable feedrate
difference (parameter No. 1783) is 500 mm/min. Deceleration is
performed as shown in the figure below:
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B–63534EN/02 PROGRAMMING 19. HIGH SPEED CUTTING FUNCTIONS
N1 G01 G91 X100. F1000 ;
N2 Y100. ;
N2
Tool path when deceleration
is not performed at the corner
Tool path when deceleration is
performed at the corner
N1
Feedrate
When deceleration is not performed
s
xi F1000 at the corner
a
–
e X When deceleration is performed
h at the corner
g t
n
o
al F500
e
at
dr
e
e
F
N1
Time
Feedrate
xis F1000
a
–
Y
e
h
g t
n
alo F500
e
at
dr
e
e
F
N2
Time
Feedrate
F1000
e
at
dr
e
e
al f F500
nti
e
g
n
a
T
N1 N2
Time
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19. HIGH SPEED CUTTING FUNCTIONS PROGRAMMING B–63534EN/02
(cid:1) Feedrate clamping by When continuous minute straight lines form curves as shown in the
acceleration example in the figure below, the feedrate difference for each axis at each
corner is not so large. For this reason, deceleration according to the
feedrate difference is not effective. Continuous small feedrate differences
make a large acceleration for each axis as a whole, however.
In this case, deceleration is performed to suppress the shock on the
machine and machining errors caused by too large acceleration. The
feedrate is decreased so that the acceleration for each axis that is obtained
using the expression below does not exceed the allowable acceleration
setting for all axes.
The allowable acceleration is set based on the maximum cutting feedrate
(parameter No. 1432) and time required to reach the feedrate (parameter
No. 1785).
Acceleration for each axis =
Feedrate difference for each axis at each corner
max!Traveldistanceinprecedingblock,Traveldistanceinfollowingblock#
F F
The decreased feedrate is obtained for each corner. The decreased feedrate
obtained at the start or end point of the block, whichever is lower, is used
as the actual feedrate.
(Example) In the example below, deceleration is performed because the
acceleration (gradient of each dotted line in the feedrate
graphs) from N2 to N4 and from N6 to N8 is too large.
N8
N7
N9
N6
N5
N4
N1
N3
N2
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N1 N5 N9 N1 N5 N9
(cid:1) Feedrate clamping by The maximum allowable feedrate v for an arc of radius r specified in a
arc radius program is calculated using the arc radius R and maximum allowable
feedrate V (setting of a parameter) for the radius as follows so that the
acceleration in an arc block does not exceed the allowable value. If the
specified feedrate exceeds the feedrate v, the feedrate is automatically
clamped to the feedrate v.
V2
Maximum allowable feedrate

R
R : Arc radius V : Feedrate for arc radius R
then, the maximum allowable feedrate v for an arc of radius r can be
obtained using the following expression:
v $ (r%R)(cid:1)V
NOTE
As the specified arc radius becomes smaller, the maximum
allowable feedrate v becomes lower. If the maximum
allowable feedrate v is lower than the setting of parameter
No. 1732 (lower feedrate limit for feedrate clamping by arc
radius), it can be assumed to be the setting of the parameter
to prevent the maximum allowable feedrate from becoming
too low.
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19. HIGH SPEED CUTTING FUNCTIONS PROGRAMMING B–63534EN/02
(cid:1) Rapid traverse By setting the corresponding parameter, the linear or non–linear
interpolation type can be selected. (In the AI nano contour control mode,
the non–linear interpolation type cannot be selected.)
When the linear interpolation type is selected, acceleration/deceleration
is performed before interpolation and linear interpolation type
positioning is used for movement. For acceleration/deceleration, linear
or bell–shaped acceleration/deceleration can be selected by setting the
corresponding parameter. (To select bell–shaped acceleration/deceleration,
the option of bell–shaped acceleration/deceleration for rapid traverse is
required.)
The feedrate during movement and acceleration for acceleration/deceleration
before interpolation are obtained as follows:
(1) Feedrate during movement
The minimum value obtained using the following expression for each
axis along which movement is done is used as the feedrate during
movement:
Rapid traverse rate for each axis (parameter No. 1420) =
Amount of travel in block
Amount of travel for each axis
(2) Acceleration for acceleration/deceleration before interpolation
(cid:1) For linear acceleration/deceleration
The minimum value obtained using the following expression for each
axis along which movement is done is used as the acceleration for linear
acceleration/deceleration before interpolation during movement:
Rapid traverse rate for each axis (parameter No. 1420)
(cid:1)
Time constant for each axis (parameter No. 1620)
Amount of travel in block
Amount of travel for each axis
(cid:1) For bell–shaped acceleration/deceleration
The time constant set in parameter No. 1621 (time constant for
bell–shaped acceleration/deceleration for rapid traverse for each axis) for
the axis for which the minimum value is obtained using the above
expression is applied to the feedrate obtained using the above
acceleration.
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B–63534EN/02 PROGRAMMING 19. HIGH SPEED CUTTING FUNCTIONS
Feedrate
Linear acceleration/
deceleration
Bell–shaped acceleration/
deceleration
ta Depends on the linear acceleration.
tb Time constant for bell–shaped
acceleration/deceleration
tc Bell–shapedacceleration/
deceleration time
tc = ta + tb
ta
tb
Time
tb tb tb tb
ta ta
tc tc
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