15. Measurement Support Functions
15.2 Skip Function; G31
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Detailed description (G31 coasting)
The amount of coasting from when the skip signal is input during the G31 command until the
machine stops differs according to the parameter "#1174 skip_F" or F command in G31.
The time to start deceleration to a stop after responding to the skip signal is short, so the machine
can be stopped precisely with a small coasting amount
δ
0
=
F
60
×
Tp +
F
60
×
( t
1
±
t
2
) =
F
60
×
( Tp + t
1
)
±
F
60
×
t
2
δ
1
δ
2
δ
0
:
Coasting amount (mm)
F :
G31 skip speed (mm/min.)
Tp :
Position loop time constant (s) = (position loop gain)
−
1
t
1
:
Response delay time (s) = (time taken from the detection to the arrival of the skip
signal at the controller via PC)
t
2
: Response error time (0.001 s)
When G31 is used for calculation, the value calculated from the section indicated by
δ
1 in the
above equation can be compensated, however,
δ
2 results in calculation error.
Skip signal input
Stop pattern with skip signal input
Area inside shaded section
denotes coasting amount
δ
0
Time (S)
Tp
t
1
±
t
2
F
The relationship between the coasting amount and speed when Tp is 30ms and t
1
is 5ms is shown
in the following figure.
Coas
tin
g
am
ount
δ
(
mm
)
Average
Feedrate F (mm/min)
Relationship between coasting amount and feedrate (example)
Max. value
Min. value
Tp = 0.03
t
1
= 0.005
0.050
0.040
0.030
0.020
0.010
0 10 20 30 40 50 60 70