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6.
6.1
6.1.1
The moment of inertia of a load (end effector and workpiece) that can be attached to the R-axis is limited by
2
the strength of the robot drive unit, service life and residual vibration during positioning. It is therefore
necessary to reduce the acceleration coefficient in accordance with the moment of inertia.
The acceleration coefficient corresponding to the R-axis tolerable moment of inertia and the moment of inertia
has the relationship shown in the graph below. The RCX340 holds different data by model or load weight inside
the controller. (Y-axis: Acceleration coefficient, X-axis: Moment of inertia around R-axis)
[ Example: YK500XC ] m=1kg
100
80
60
40
20
0
Therefore, optimal acceleration coefficient is automatically determined by entering only the load weight and
the moment of inertia.
The tolerable R-axis moment of inertia and the acceleration coefficient in relation to the moment of inertia are
given in section 6.1.3 which follows.
c
CAUTION
The "tip weight" parameter is applicable only to integer entry. For example, even when the load weight is "1.1kg",
round up the digits after the decimal point and set "2kg".
6.1.2
In the YK-X series robots, it is necessary to set the parameter according to the moment of inertia of the load
around the R-axis. Set the moment of inertia around the R-axis of the load for the "R axis inertia for SCARA
2
[kgm
x 10
c
CAUTION
• When the input value to the "R axis inertia for SCARA [kgm
actual load, the warning is issued from the controller.
When the load shape is large, set a larger value for the "R axis inertia for SCARA [kgm
• Vibrations may occur in the R-axis depending on the load status or operation pattern. In this case, make the
input value of the "R axis inertia for SCARA [kgm
• Do not change a robot parameter other than "R axis inertia for SCARA [kgm
coordinate accuracy may lower or the robot may malfunction.
Methods for calculating the moment of inertia of the load are shown in "6.2 Equation for moment of inertia
calculation" and "6.3 Example of moment of inertia calculation" in this Chapter. However, it is not easy to
precisely figure out these values. If a calculated value smaller than the actual moment of inertia is set, residual
vibrations may occur. In this case, decrease the SCARA R-axis moment of inertia further.
c
CAUTION
• Enter the correct payload and SCARA R-axis moment of inertia and strictly observe the tolerable moment of
inertia to operate the robot in a correct and safe manner. If not observed, the service life of the drive part may
lower, breakage or residual vibrations during positioning may occur.
• Depending on the Z-axis position, vibration may occur when the X, Y or R-axis moves. If this happens, reduce
the X, Y or R-axis acceleration to an appropriate level.
• If the moment of inertia is too large, vibration may occur on the Z-axis depending on its operation position. If
this happens, reduce the Z-axis acceleration to an appropriate level.
2-20
Attaching the end effector
Acceleration coefficient vs. moment of inertia
R-axis tolerable moment of inertia and acceleration coefficient
A
A
A
(%)
X,
Y,
R
0.005 ( 0.05 )
0.04
0.08
0
0.4
0.8
Parameter setting according to R-axis moment of inertial of load
-4
]" robot parameter in kgm
0.12
I
(kgm
2
)
r
1.2
J
(kgf
cm
r
•
2
-4
x 10
units.
2
x 10
2
x 10
-4
]" parameter larger to make the adjustment.
2
sec
)
•
-4
]" parameter is small when compared to the
2
-4
x 10
]" parameter.
2
x 10
-4
]". If changed, the Cartesian
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