Mitsubishi Electric MELDAS C6 Programming Manual page 269

13. Program Support Functions
(2) Arc speed clamp
During circular interpolation, even when moving at a constant speed, acceleration is
generated as the advance direction constantly changes. When the arc radius is large
compared to the commanded speed, control is carried out at the commanded speed. However,
when the arc radius is relatively small, the speed is clamped so that the generated acceleration
does not exceed the tolerable acceleration/deceleration speed before interpolation, calculated
with the parameters.
This allows arc cutting to be carried out at an optimum speed for the arc radius.
When the above F' expression is substituted in the expression expressing the maximum
logical arc radius reduction error amount ∆R explained in the section "a) Pre-interpolation
acceleration/deceleration", the commanded radius R is eliminated, and ∆R does not rely on R.
1
∆R ≤
2R
1
≤
2R
In other words, with the arc command in the high-accuracy control mode, in logical terms
regardless of the commanded speed F or commanded radius R, machining can be carried out
with a radius reduction error amount within a constant value.
To further lower the arc clamp speed (to further improve the roundness), the arc clamp speed
can be lowered with the machining parameter "#8019 R COMPEN". In this case, speed control
is carried out to improve the maximum arc radius reduction error amount ∆R by the set
percentage.
∆R × (100 − Ks)
∆R' ≤
After setting the "R COMPEN", the above ∆R' will appear on the parameter screen.
R COMPEN (0.078) 50
(Note 1) When the "R COMPEN" is set, the arc clamp speed will drop, so in a machining program
with many arc commands, the machining time will take longer.
(Note 2) The "R COMPEN" is valid only when the arc speed clamp is applied. To reduce the radius
reduction error when not using the arc speed clamp, the commanded speed F must be
lowered.
∆θ
F
F
θ
F
2 (1 − Kf 2 2
{Tp ) } ( )
60
∆V' × 1000
(1 − Kf
2 2
{Tp ) } (
60
(mm)
100
Accuracy coefficient setting value
∆R'
261
13.12 High-accuracy control
F : Commanded speed (mm/min)
F
R : Commanded arc radius (mm)
θ
∆
: Angle change per interpolation unit
∆V
∆V : Speed change per interpolation unit
F
The tool is fed with the arc clamp speed F so that
∆V does not exceed the tolerable
acceleration/deceleration speed before
interpolation ∆V.
F ≤ R × ∆V × 60 × 1000 (mm/min)
G1bF (mm/min)
∆V =
G1btL (ms)
∆R : Arc radius reduction error amount
Tp : Position loop gain time constant of
servo system
Kf : Feed forward coefficient
)
F : Cutting feedrate
∆R' : Maximum arc radius reduction error amount
Ks : R COMPEN (%)