Offset
Pickup of moving parts
With conveyor tracking, the pickup position of the robot may deviate from the center of the part as shown below. This gap occurs as a result of accuracy errors of the vision system calibration, tool calibration, and tracking.
Followings are countermeasures for the problem.
Feed the part with an angle near 0°degree. Then, pick up the part.
Measure the gap between the center of the part and the robot’s pickup position.
Repeat the steps 1 and 2 for five times and calculate the average.
Set the average calculated in step 3 to the program as follows:
> Jump Cnv_QueGet(1) +X(**)Feed the part with an angle near 90°degree. Then, pick up the part.
If the gap is large, fine-tune the value set in the step (4).
Feed the part with an angle near 0°degree. Then, pick up the part.
If the gap is large, fine-tune the value set in the step (6).
Repeating steps 6 to 8 may improve picking accuracy.
KEY POINTS
If the gap between the center of the part and the pickup position can be measured by using the vision system, compensate the "Offset" as follows:
Feed the part with an angle near 0 degree. Then, pick up the part.
Take the image of the picked part by the camera and record X and Y coordinates.
Repeat the steps 1 and 2 for five times and calculate the average.
Feed the part with an angle near 90°degree. Then, pick up the part.
Take the image of the picked part by the camera and record X and Y coordinates.
Repeat the steps 5 and 6 for five times and calculate the average.
Feed the part with an angle near 180°degree. Then, pick up the part.
Take the image of the picked part by the camera and record X and Y coordinates.
Repeat the steps 7 and 8 for five times and calculate the average.
Feed the part with an angle near 270 degree. Then, pick up the part.
Take the image of the picked part by the camera and record X and Y coordinates.
Repeat the steps 11 and 12 for five times and calculate the average.
Plot the values in the steps 3, 6, 9, and 12 as shown in the figure below, and calculate the offset value.
Set the offset value to the program as follows:
> Jump Cnv_QueGet(1) +X(offset)
KEY POINTS
Depending on the offset value, the upstream limit may be exceeded and error 4406 may occur.
Wait Cnv_QueLen(1, CNV_QUELEN_PICKUPAREA) > 0
Jump Cnv_QueGet(1) -X(offset)
The error can be avoided by doing either of the following:
- Set the wait time before Jump command.
- Set the "offset" when registering the queue and not to register when executing the Jump command.