Weight and Inertia Settings
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 Joint #4. If, for some unavoidable reason, the load or moment of inertia exceeds the rated value, or if eccentricity occurs, configure parameters as described in the "Weight setting" and "Inertia setting."
These settings optimize the Manipulator's PTP motion, reduce vibration, and shorten operation times. 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"
Weight Setting
CAUTION
- The total weight of the hand and the workpiece must not exceed 8 kg. The GX8 series Manipulators are not designed to work with loads exceeding 8 kg. Always set the value according to the load. Setting the hand weight parameter to a value smaller than the actual weight may cause errors or impact that not only impair full functionality but also shorten the life of the mechanical components.
The allowable load weight (hand and workpiece) in the GX8 series is 4 kg at the default rating and 8 kg at the maximum.
Depending on the load weight, change the setting for the hand weight parameter in the Weight statement. After the setting is changed, the maximum speed and acceleration/deceleration of the Manipulator during PTP motion that correspond to the "Hand Weight" are corrected automatically.
Weight of Load Attached to Shaft
The weight of the load (hand + workpiece) attached to the shaft can be set by the "Hand Weight" parameter in the Weight statement.
Go to [Tools] - [Robot Manager] - [Weight] panel, and enter the value in the [Weight] text box. (This can also be set using the Weight statement in [Command Window].)
Weight of Load Attached to Arm
When a camera, valve, or other object is attached to the arm, its weight is converted to the equivalent weight of the shaft and added to the weight of the load attached to shaft to set the "Hand Weight" parameter.
If an external wiring unit (excluding cables) is installed near the user connector on the Arm #2 side, add 0.16 kg to the equivalent weight conversion value of the shaft.
Equivalent weight formula
WM=M×(LM+L1)2/(L1+L2)2
WM: Equivalent weight
M: Weight of load attached to the arm
L1: Length of Arm #1
L2: Length of Arm #2
LM: Distance from rotation center of Joint #2 to center of gravity of load attached to the arm
Example:
Calculates [Weight] parameter when a 1 kg camera is attached to the end of GX8 Arm #2 (350 mm from the center of rotation of Joint #2) with a load weight of W = 2 kg
W=2
M = 1
L1=300
L2 = 250
LM = 350
WM=1×(350+300)2/(250+300)2=1.40 (Round up to two decimal places)
W + WM = 2 + 1.4 = 3.4
Enter "3.4" for the [Hand Weight] parameter.
| Symbol | Description |
|---|---|
| a | Shaft |
| b | Weight of the entire camera M = 1 kg |
| c | W = 2 kg |
| d | Joint #2 |
| e | Joint #1 |
Automatic Speed Correction at Weight Setting
Standard mode
GX8-A/GX8-B/GX8-C45***
The percentages on the graph are ratios based on 100% as the speed at the rated (4 kg) setting.
GX8-A/GX8-B/GX8-C55***
The percentages on the graph are ratios based on 100% as the speed at the rated (4 kg) setting.
GX8-A/GX8-B/GX8-C65***
The percentages on the graph are ratios based on 100% as the speed at the rated (4 kg) setting.
Boost mode
GX8-A/GX8-B/GX8-C45***
The percentages on the graph are ratios based on 100% as the speed at the rated (4 kg) setting.
GX8-A/GX8-B/GX8-C55***
The percentages on the graph are ratios based on 100% as the speed at the rated (4 kg) setting.
GX8-A/GX8-B/GX8-C65***
The percentages on the graph are ratios based on 100% as the speed at the rated (4 kg) setting.
Automatic Acceleration/Deceleration Correction at Weight Setting
Standard mode
GX8-A/GX8-B/GX8-C45***
The percentages on the graph are ratios based on 100% as the acceleration/deceleration at the rated (4 kg) setting.
GX8-A/GX8-B/GX8-C55***
The percentages on the graph are ratios based on 100% as the acceleration/deceleration at the rated (4 kg) setting.
GX8-A/GX8-B/GX8-C65***
The percentages on the graph are ratios based on 100% as the acceleration/deceleration at the rated (4 kg) setting.
Boost mode
GX8-A/GX8-B/GX8-C45***
The percentages on the graph are ratios based on 100% as the acceleration/deceleration at the rated (4 kg) setting.
GX8-A/GX8-B/GX8-C55***
The percentages on the graph are ratios based on 100% as the acceleration/deceleration at the rated (4 kg) setting.
GX8-A/GX8-B/GX8-C65***
The percentages on the graph are ratios based on 100% as the acceleration/deceleration at the rated (4 kg) setting.
Inertia Setting
Moment of Inertia and Inertia Setting
The moment of inertia is a quantity that expresses how hard it is for an object to turn, and it is expressed in terms of values for the moment of inertia, inertia, or GD2. When a hand or other object is attached to a shaft for operation, the moment of inertia of the load must be taken into consideration.
CAUTION
- The moment of inertia of the load (weight of the hand and workpiece) must be 0.16 kg·m2 or less. The GX8 series Manipulators are not designed to work with a moment of inertia exceeding 0.16 kg·m2. Always set the value corresponding to the moment of inertia. Setting a parameter value that is smaller than the actual moment of inertia may cause errors or impact, may prevent the Manipulator from working at full functionality, and may shorten the lifespan of mechanical parts.
The allowable moment of inertia of a load for GX8 series Manipulators is 0.01 kg·m2 at the default rating and 0.16 kg·m2 at the maximum. Depending on the moment of inertia, change the setting of the moment of inertia parameter for the load in the Inertia statement. After the setting is changed, the maximum acceleration/deceleration of Joint #4 during PTP motion that corresponds to the "Inertia" value is corrected automatically.
Moment of Inertia of Load Attached to Shaft
The moment of inertia of the load (hand + workpiece) attached to the shaft can be set by the "Inertia" parameter in the Inertia statement.
Go to [Tools] - [Robot Manager] - [Inertia] panel, and enter the value in [Inertia].
This can also be set using the Inertia statement in [Command Window].
Automatic Acceleration/Deceleration Correction of Joint #4 at Inertia (Moment of Inertia) Setting
Standard mode, boost mode
GX8-A/GX8-B/GX8-C45***, GX8-A/GX8-B/GX8-C55***, GX8-A/GX8-B/GX8-C65***
The percentages on the graph are ratios based on 100% as the acceleration/deceleration at the rated (0.01 kg·m2) setting.
Eccentricity and Inertia Setting
CAUTION
- The eccentricity of the load (hand and workpiece) must be 150 mm or less. The GX8 series Manipulators are not designed to work with eccentricities exceeding 150 mm. Always set the value based on the eccentricity. Setting the eccentricity parameter to a value smaller than the actual eccentricity may cause errors or impact that not only impair full functionality but also shorten the life of the mechanical components.
The allowable eccentricity of load for GX8 series Manipulators is 0 mm at the default rating and 150 mm at the maximum. Depending on the load eccentricity, change the setting for the eccentricity parameter in Inertia statement. After the setting is changed, the maximum acceleration/deceleration of the Manipulator during PTP motion that corresponds to the "Eccentricity" is corrected automatically.
Eccentricity
| Symbol | Description |
|---|---|
| a | Rotation axis |
| b | Load center of gravity position |
| c | Eccentricity (150 mm or less) |
Eccentricity of Load Attached to Shaft
The eccentricity of the load (hand + workpiece) attached to the shaft can be set by the "Eccentricity" parameter in the Inertia statement.
Go to [Tools] - [Robot Manager] - [Inertia] panel, and enter the value in [Eccentricity].
This can also be set using the Inertia statement in [Command Window].
Automatic Acceleration/Deceleration Correction at Inertia (Eccentricity) Setting
Standard mode, boost mode
GX8-A/GX8-B/GX8-C45***, GX8-A/GX8-B/GX8-C55***, GX8-A/GX8-B/GX8-C65***
The percentages on the graph are ratios based on 100% as the acceleration/deceleration at the 0 mm setting.
Calculating the Moment of Inertia
An example of calculating the moment of inertia of a load (hand holding a workpiece) is shown below.
The moment of inertia of the entire load is calculated by the sum of (a), (b), and (c).
| Symbol | Description |
|---|---|
| a | Hand |
| b | Workpiece |
| c | Workpiece |
| d | Shaft |
| e | Rotation axis |
The methods for calculating the moment of inertia for (a), (b), and (c) are shown below. Use the moment of inertia of these basic shapes as a reference to find the moment of inertia of the entire load.
(a) Moment of inertia of a rectangular parallelepiped
| Symbol | Description |
|---|---|
| a | Rotation axis |
| c | Center of gravity of rectangular parallelepiped |
(b) Moment of inertia of a cylinder
| Symbol | Description |
|---|---|
| a | Center of gravity of cylinder |
| b | Rotation axis |
(c) Moment of inertia of a sphere
| Symbol | Description |
|---|---|
| a | Rotation axis |
| b | Center of gravity of sphere |