Fanuc encoder and collaborative robot

All important info is missing including type of robot, type of plc, type of connection between them...

Also don't see why plc needs to know the conveyor position. Based on your description, robot just needs a digital signal from plc that it is ok to load parts on conveyor.

if you have a working EIP connection, mapping signals back and forth should be no problem and if you need help, members in Fanuc forum section should be able to provide guidance. so i am moving this topic to Fanuc forum.

as far as process goes, i find that setup odd...

1. PLC controls conveyor

2. Robot monitors conveyor position via encoder.

3. conveyor position is sent from robot to PLC

4. PLC makes decision and sends to Robot signal "load conveyor enable"

first of all there need to be a sensor to ensure that placement location is not already populated. for example placed by operator, or even one placed by robot if robot loses track of it (perhaps after restart etc.)

also if the signal from PLC is supposed to function as registration sensor, the problem is latency or data update speed.... above approach can work for conveyor that moves a bit then stops and waits for robot to place parts. but if conveyor is running continuously, this kind of handshaking is going to be slow and as a result placement is going to be inconsistent (6 parts will not be in nice straight line of 6 but three jagged lines of 2). reason is latencies in EIP data exchange, PLC scan time etc.

in my experience registration input is a high speed input on same device that tracks conveyor position. in this case that would be robot controller because that is where encoder is wired.

not familiar enough with your process or Fanuc setup or capabilities so i would leave that to others. for me, this could work slightly differently:

1. robot signal that enables placing is not treated as registration signal, it is only permission to place parts on conveyor (for example to allow dry cycle operation, etc.). so this signal does not change very frequently (for every part) - it can stay on for hours/days/weeks...

2. robot reads conveyor signal, robot decides where to place parts (if permitted by PLC and conveyor moved enough to place the part). then robot triggers registration or resetting of conveyor position in a convenient manner... this also enables continuous operation without conveyor position rollower.

3. PLC monitors conveyor position (refresh and latencies not critical any more). and if value exceeds some present limit (according to robot reach and conveyor speed), it pauses conveyor or optionally disables placing of parts on conveyor. this way robot can catch up if needed...

Do you only need to map the encoder counts over? The encoder is hooked up to the robot right?

Can the omron do explict messaging? If so, you could read the counts out of a register. Otherwise, you will have to setup some group outputs.

The Ethernet/IP manual goes over it. There is a whole section that covers all the explicit messages. If you have Rockwell software, I created an example program for all cases in the manual here.

Why to bother with encoder at all? How much precision on the conveyor you are looking for? (gap between rows of parts) What kind of drive you have on the conveyor? I would drive the belt ether off PLC or robot DO with a timer. And set a sensor parallel to the row trailing edge to be sure it is clear to place the part after belt was indexed.

Also from your picture there should be one placement location and then you offset it five times to create your row. Or the conveyor never stops? Than I would placed the sensor on the leading edge of the row, sensor not blocked - ready to start new row, finished the row, reset offsets, sensor is off - start new one...

Quote from manthan

. So belt expands, retracts, bents, slips, anything you can think off. Sometimes, gets a bumps on it.

Your encoder won't detect that mechanical inadequates, it is mounted at the motor, so bending, extracting, slipping will not be detected.

If you really want to catch all those things I think you need a camera.

Quote from hermann

Your encoder won't detect that mechanical inadequates, it is mounted at the motor, so bending, extracting, slipping will not be detected.

If you really want to catch all those things I think you need a camera.

I guess he meant encoder with the roller that we roll on the conveyor surface... Any way seems over kill. I have a cell that places parts on the slow moving belt, two parts per normal cycle, and in the break mode, when operator is not present it stagger them on the belt to fill entire surface. Pretty tight too. Coolant reserve tank, sitting on the belt upside down...on the neck... Runs on timers and constant belt speed. Unless you are talking one millimeter tolerance, but in this case squeezing parts on the belt, what are you gaining? One extra row of six parts over an hour? Need more parts on the belt, get a bigger belt...

Still, what if something stuck under encoder, you will get false reading and potentially either crush of never load or bigger gaps...

Quote from sborchshev

Still, what if something stuck under encoder, you will get false reading and potentially either crush of never load or bigger gaps...

Put a broom in front of the encoder. Did this exact thing on several ford lines with the encoder wheel on the conveyor surface.

Quote from manthan

Also, if you could help. We have iRPick tool as well. But, without sensor or vision. Is it possible to use just encoder to place parts? what would the basic idea would be? I am reading manuals but they all includes sensor and vision to work with.

I'm not familar with iRPick tool, but I think you could use the line tracking commands to do this. Take a look at the line tracking option manual.

The basic setup would be: Trigger via an IO to reset the tracking, then go place via a tracking program.