Hello, I am college student and i have a project where a UR3 is used. The entire system will be controlled by a PLC. The goal is to have the operation of the machine done by only one HMI which is connected to the PLC. For simplicity of operation, the teach pendant of the UR shall not be needed in normal operation. There are different tasks the robot must perform (mostly pick and place). Ive done the program in UR3 and it run with no problem at all. But after the PLC and the UR3 was connected via Modbus TCP/IP the gripper suddenly error(gripper will shut the entire system stop or the gripper still working but not like how we want).
If you are using a gripper like ROBOTIQ or OnRobot, very likely there will be already a MODBUS connection between the robot and the tool. Therefore, you have to make sure the MODBUS between the PLC and the robot does not overlap with the one that communicates with the gripper.
I would advise to change the PLC and robot IP addresses, and then assign the PLC-UR MODBUS to one of the new addresses.
Also review this new MODBUS does not overlap with the UR internal MODBUS either. Through the IP address 127.0.0.1 port 502 you can access it, and it contains info about the TCP, joints, etc: Modbus Server - 16377 | Universal Robots Support