Mitsubishi Electric MELSEC iQ-R16MTCPU Programming Manual page 232

Tolerable acceleration control for each axis (optimum acceleration control)
The acceleration that occurs at the joint between blocks is evaluated by each axis and deceleration control for passing block
joints at the optimum speed is performed. This enables the cutting of highly precise edges. The optimum speed is calculated
so that the acceleration that occurs at each axis at the block joints is equal to or less than the tolerable acceleration for each
axis. The system decelerates to this speed in advance, and after passing the corner, returns to the command speed. When
blocks are joined smoothly (when the acceleration that occurs at each axis is equal to or less than the tolerable acceleration of
each axis), there is no deceleration. By using tolerable acceleration control for each axis, even when a specific axis (rotating
axis) has a low tolerable acceleration and vibrations on the machine occur easily, deceleration is made at deceleration speeds
that correspond to the characteristics of each axis. Thus at corners where acceleration occurs, the deceleration speed can be
set high on axes whose tolerable acceleration is high, reducing the cycle time.
For a corner when acceleration occurs in both the X-axis (linear axis) and C-axis (rotating axis) such as the corner in the chart
below, the corner speed (F) of each axis is controlled so that the acceleration that occurs at the X-axis does not exceed the X-
axis tolerable acceleration, and the acceleration that occurs at the C-axis does not exceed the C-axis tolerable acceleration.
When the X-axis tolerable acceleration is higher than the C-axis tolerable acceleration, the deceleration speed on paths
where acceleration occurs only on the X-axis can be set higher than the deceleration speed on paths where acceleration
occurs only on the C-axis, resulting in the following speed patterns.
Acceleration occurs at the X-axis (linear axis)
Corner shape
C-axis
Speed pattern
Composite speed
X-axis speed
C-axis speed
To improve edge precision further, make the accuracy coefficient larger. However, when the accuracy coefficient is made
larger, the optimum corner speed is reduced, making the cycle time longer.
When a negative value is set to the accuracy coefficient, the optimum corner speed increases and the cycle time shortens.
However, the edge precision is reduced.
The tolerable speed can be adjusted for each axis and is calculated with the following formula.
Common tolerable acceleration
2
for each axis[mm/s ]
*1 When set to "0", the speed of the G-code control axis parameter "fast forward speed" is used.
*2 When set to "0", the time constant of the G-code control axis parameter "G0 time constant (linear)" is used.
6 AUXILIARY AND APPLIED FUNCTIONS
230
6.7 High-Accuracy Control
F: Speed after passing corner
F: Speed before passing corner
∆F: Acceleration at corner
X-axis
2
F0 = F0x + F0c
The acceleration that
occurs at X-axis is
controlled so it is equal
to or less than the X-axis
tolerable acceleration/deceleration
F0x
F0c
Cutting feed for each axis before
interpolation - maximum speed[mm/min]
=
Cutting feed for each axis before
interpolation - time constant[ms]
Acceleration occurs at the C-axis (rotating axis)
C-axis
F: Speed before passing corner
Composite speed
2
Time
X-axis speed
Time
C-axis speed
Time
100 - Corner accuracy
coefficient
*1
÷ 60
×
*2
÷ 1000
F: Speed after passing corner
∆F: Acceleration at corner
X-axis
2
F0 = F0x + F0c
F0x
The acceleration that occurs
in the C-axis is controlled so
it is equal to or less than the
C-axis tolerable acceleration/
deceleration
F0c
100 - Accuracy
coefficient for each axis
×
100 100
2
Time
Time
Time