davidg68124
Member
Okay guys,
I have a project where I am using the CompactLogix L43 processor with a SERCOS interface to an Ultra 3000. I also have a 1769-HSC card with 2 auxiliary encoders (Dynapar 1000ct/rev) for feedback in addition to the motor mounted encoder (I will explain why in a minute). The motor is a 1326AB-430E with an Alpha SK+ GB at 10:1. It is on a press/shear and it drives in angle bar stock to a length and then I drive the press to cycle. Easy, right?
The customer had an old existing press using a 1394 and the same motor and ratio gearbox. They had the 2 encoders on the old unit so that is why they wanted the 2 on the new unit. They were buying a new press and duplicating the tooling so they needed to stay with the same concept. They requested a direct upgrade to current technology and I obliged them.
I mimiced everything up to and including converting some of the GML to motion on the Compactlogix. Much of the GML was really bad, so I ignored it and wrote the program as a true indexing application with the Encoders as a backcheck to the Servo in terms of distance indexed. Well after seeing the thing run, I actually simplified the programming and removed all the old program limitations. What I did not realize is how they were utilizing the 2 encoders. They relied on the primary encoder (infeed) throughout the piece of barstock until the last piece was to be cut. There they used a relay to switch the encoders on the Auxiliary input and tried to copy the position back into it, back up, and then feed it out to length for the final cut. Well, as you can imagine, there are all sorts of problems with this.
I have all the system up and going. It cycles properly and everything moves as I would expect. They are extremely happy with the overall installation and operation with one exception, I cannot get the length to be right. WHy? The physical drive (not the Servo) slips on the barstock. That is why they need the auxiliary encoder. So just put the encoder on the auxiliary and call it good. What about the second encoder? WE (the customer and I) do not want to go back to the way the other press is doing it.
I have been in Rockwell's tech support on this and we can up with a way to create virtual axi out of the HSC's, but there is one caveat. I have geared the servo axis to the encoder virtual axis and it follows without any problem but the Move Axis(MAM instruction) command required to cause the system to move that I issue for the Virtual axis is being overwritten by the ones that I am using to aquire the encoder position with. So after a few calls we came up with creating another master virtual axis to follow to gear to, but that is not getting me there wither since it has no reference for an actual postion so I still do not get the proper lengths. I cannot gear the master to the encoder axis as I still run into the same problem as before. Rockwell says I should just change the drive to a Kinetix 6000 and hang another axis module on there and use it for a feedback only axis and then I could merge the encoder positions on the fly. That is not so easy as this is a bid project and that would mean additional costs.
In retrospect, I should have run all the motion calcualtions as I could have used a much smaller motor. I might have also caught the fact about how they are using the encoders and averted this. But now I need some ideas to make this work. I would welcome all suggestions right now. I am mulling it over this weekend so I can get a direction. If you have any suggestions, I would greatly appreciate it.
David
I have a project where I am using the CompactLogix L43 processor with a SERCOS interface to an Ultra 3000. I also have a 1769-HSC card with 2 auxiliary encoders (Dynapar 1000ct/rev) for feedback in addition to the motor mounted encoder (I will explain why in a minute). The motor is a 1326AB-430E with an Alpha SK+ GB at 10:1. It is on a press/shear and it drives in angle bar stock to a length and then I drive the press to cycle. Easy, right?
The customer had an old existing press using a 1394 and the same motor and ratio gearbox. They had the 2 encoders on the old unit so that is why they wanted the 2 on the new unit. They were buying a new press and duplicating the tooling so they needed to stay with the same concept. They requested a direct upgrade to current technology and I obliged them.
I mimiced everything up to and including converting some of the GML to motion on the Compactlogix. Much of the GML was really bad, so I ignored it and wrote the program as a true indexing application with the Encoders as a backcheck to the Servo in terms of distance indexed. Well after seeing the thing run, I actually simplified the programming and removed all the old program limitations. What I did not realize is how they were utilizing the 2 encoders. They relied on the primary encoder (infeed) throughout the piece of barstock until the last piece was to be cut. There they used a relay to switch the encoders on the Auxiliary input and tried to copy the position back into it, back up, and then feed it out to length for the final cut. Well, as you can imagine, there are all sorts of problems with this.
I have all the system up and going. It cycles properly and everything moves as I would expect. They are extremely happy with the overall installation and operation with one exception, I cannot get the length to be right. WHy? The physical drive (not the Servo) slips on the barstock. That is why they need the auxiliary encoder. So just put the encoder on the auxiliary and call it good. What about the second encoder? WE (the customer and I) do not want to go back to the way the other press is doing it.
I have been in Rockwell's tech support on this and we can up with a way to create virtual axi out of the HSC's, but there is one caveat. I have geared the servo axis to the encoder virtual axis and it follows without any problem but the Move Axis(MAM instruction) command required to cause the system to move that I issue for the Virtual axis is being overwritten by the ones that I am using to aquire the encoder position with. So after a few calls we came up with creating another master virtual axis to follow to gear to, but that is not getting me there wither since it has no reference for an actual postion so I still do not get the proper lengths. I cannot gear the master to the encoder axis as I still run into the same problem as before. Rockwell says I should just change the drive to a Kinetix 6000 and hang another axis module on there and use it for a feedback only axis and then I could merge the encoder positions on the fly. That is not so easy as this is a bid project and that would mean additional costs.
In retrospect, I should have run all the motion calcualtions as I could have used a much smaller motor. I might have also caught the fact about how they are using the encoders and averted this. But now I need some ideas to make this work. I would welcome all suggestions right now. I am mulling it over this weekend so I can get a direction. If you have any suggestions, I would greatly appreciate it.
David