WEIGHT and INERTIA Settings
The WEIGHT and INERTIA commands are for setting the load parameters of the Manipulator. These settings optimize the Manipulator motion.
- WEIGHT Setting
The WEIGHT command is for setting the load weight. The more the load weight increases, the more the speed and acceleration/deceleration are reduced. - INERTIA Setting
The INERTIA command is for setting the inertia moment and the eccentricity of the load. The more the inertia moment increases, the more the acceleration and deceleration of the Arm #6 are reduced. The more the eccentricity increases, the more the acceleration and deceleration for the Manipulator movement are reduced.
To ensure that the Manipulator is functioning properly, keep the load (the sum of the weights of the hand and workpiece) and the moment of inertia of the load within the rated values, and do not allow for eccentricity from the center of the Arm #6. If the load or the inertia moment exceeds the ratings or if the load becomes eccentric, follow the steps below to set parameters.
Setting parameters makes the operation of the Manipulator optimal, reduces vibration to shorten the operating time, and improves the capacity for larger loads. This also works to curb any persistent vibration that may occur when the hand and workpiece have a large moment of inertia.
You can also perform settings using the "Weight, Inertia, and Eccentricity/Offset Measurement Utility."
For details, refer to the following manual.
"Epson RC+ User's Guide - Weight, Inertia, and Eccentricity/Offset Measurement Utility"
The allowable load for C4 series Manipulators is up to 4 (5) kg*.
Due to the limitations of the moment and moment of inertia shown in the table below, the load (hand + workpiece) should also meet these conditions.
If force is applied to the Manipulator instead of weight, it should not exceed the values shown in the table below.
* If the payload exceeds the maximum payload, refer to the following section.
"WEIGHT Setting - Restrictions on payload exceeding the maximum payload"
Allowable Load
| Joint | Allowable moment | (GD2/4) Allowable Moment of Inertia |
|---|---|---|
| Joint #4 | 4.41 N·m (0.45 kgf·m) | 0.15 kg·m2 |
| Joint #5 * | 4.41 N·m (0.45 kgf·m) | 0.15 kg·m2 |
| Joint #6 | 2.94 N·m (0.3 kgf·m) | 0.1 kg·m2 |
Moment
The moment indicates amount of torque applied on the joint in order to support the gravity on the load hand + workpiece). The moment increases as weight of the load and amount of eccentricity increase. As this also increases the load applied on the joint, make sure to keep the moment within the allowable value.
A maximum torque (T) is calculated by the following formula.
T = m (kg) × L (m) × g (m/s2)
- m: Weight of load (kg)
- L: Eccentricity of load (m)
- g: Gravitational acceleration (m/s2)
The figure below shows distribution of the center of gravity when the volume of the load (hand + workpiece) is small. Design the hand so that the center of gravity is within the allowable moment.
| Symbol | Description |
|---|---|
| a | Distance from the center of Arm #* rotation [mm] |
| b | Center of gravity of load from the Arm #* rotation center [mm] |
Max. Eccentricity of Load (Distance between the joint rotation center and the load’s center of gravity)
| Axis | WEIGHT 1 kg | WEIGHT 2 kg | WEIGHT 3 kg | WEIGHT 4 kg |
|---|---|---|---|---|
| #4 | 200 mm | 200 mm | 150 mm | 112 mm |
| #5 | 200 mm | 200 mm | 150 mm | 112 mm |
| #6 | 200 mm | 150 mm | 100 mm | 75 mm |
(The maximum eccentricity of load is restricted to 200 mm or less.)
When calculating the critical dimension of the load using the allowable moment and inertia moment, the calculated value represents a distance from the Arm #6 rotation center, not the distance from the flange. To calculate the distance from the flange to the load’s center of gravity, subtract the distance from the center of the Arm #5 rotation center to the flange (=65 mm) as shown in the example below.
Example: Calculate the critical dimension of the load on the Arm #5 (A) when a 2.5 kg load is on the Arm #6 rotation center line (B = 0)
Center of gravity by the allowable moment control: 4.41 N·m/(2.5 kg × 9.8 m/s2) = 0.18 m = 180 mm
Due to the allowable moment control, center of gravity for the load limit is 180 mm from the Arm #5 rotation center.
Distance from the flange to the center of gravity for the load limit A = 180 mm - 65 mm = 115 mm
Critical Dimension of Load
(Units: mm)
| Symbol | Description |
|---|---|
| a | Load center of gravity position |
| b | Arm #6 rotation center |
| c | Flange |
| d | Arm #5 rotation center |