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6.
Attaching the end effector
6.1
Acceleration coefficient vs. moment of inertia
6.1.1
R-axis tolerable moment of inertia and acceleration coefficient
The moment of inertia of a load (end effector and workpiece) that can be attached to the R-axis is limited by
the strength of the robot drive unit 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)
100
80
60
40
20
0
0.01
0.1
0
Therefore, optimal acceleration coefficient is automatically determined by entering only the load weight and
the moment of inertia.
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
Parameter setting according to R-axis moment of inertial of load
In the YK-XG 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 "SCARA R axis inertia [kgm
2
-4
parameter in kgm
x 10
c
CAUTION
• When the input value to the "SCARA R axis inertia [kgm
actual load, the warning is given from the controller.
When the load shape is large, set a larger value for the "SCARA R axis inertia [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 "SCARA R axis inertia [kgm
• Do not change a robot parameter other than "SCARA R axis inertia [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.
0.02
0.03
0.2
0.3
steps.
2
x 10
0.04
0.05
Ir (kgm
)
2
0.4
0.5
Jr (kgfcmsec
2
2
-4
x 10
]" parameter is small when compared to the
-4
]" parameter larger to make the adjustment.
2
-4
x 10
]". If changed, the Cartesian
)
23207-FM-00
2
-4
x 10
]" robot
2
-4
x 10
]" parameter.
2-11
2
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