I am not the best programmer by any means but I usually can sort out most problems; not this time. Three of us have been trying to solve this issue, it has gotten to the point where it is starting to crank my winder so I figured it was time to seek outside assistance.
Not the best of programs but it has been running for more than a year without problems.
We have a small rotary assembly table that compresses three separate components together using about 900 ft.-Lbs. supplied through a pneumatic cylinder. To prevent dry cycling the fixtures we have two lasers looking for parts in the nests. The Bit Array is shifted every time the table indexes, if parts are present the cylinder is cycled and a one is loaded. Three stations over a pick-and-place; using vacuum cups, picks the parts and drops them onto a conveyor. This has run flawlessly for over a year.
There are times when the components do not successfully snap together and then are dropped on the line and need to be sorted and run back through the press. It was decided that the we should be looking for the cylinder to completely extend instead of using the part present lasers. This would allow the pick-and-place to skip over parts that were not compressed together properly, instead cycling them back through the machine a second time.
Now I am finally to my problem, the lasers worked perfectly for more than a year. When we switched the input signal in the program to the “Press in Down Position” bit, the Bit Shift stops working. The limit is functional and is seen by the PLC, the “Parts Present” bit will go true but a one is never loaded into the Array. To troubleshoot the problem we branched the rung and added a test bit that we toggle on the fly. When we run the lasers everything is perfect, as soon as we toggle over to the limit switch the Bit Shift stops and when we swap back it will start again.
The table dwell time is two seconds. The “Table in Position” bit and the lasers come on almost simultaneously, whereas the “Press in Down Position” bit lags by about a quarter second. I do not see that this should be an issue because I can manually load the bit while the machine is idle and it takes me far longer than a quarter second but it will accept it. That is the only difference we have been able to find.
Now that I have finished my novelette, hopefully someone can enlighten us as to the error of our ways.
Thank you for taking the time to read.
Not the best of programs but it has been running for more than a year without problems.
We have a small rotary assembly table that compresses three separate components together using about 900 ft.-Lbs. supplied through a pneumatic cylinder. To prevent dry cycling the fixtures we have two lasers looking for parts in the nests. The Bit Array is shifted every time the table indexes, if parts are present the cylinder is cycled and a one is loaded. Three stations over a pick-and-place; using vacuum cups, picks the parts and drops them onto a conveyor. This has run flawlessly for over a year.
There are times when the components do not successfully snap together and then are dropped on the line and need to be sorted and run back through the press. It was decided that the we should be looking for the cylinder to completely extend instead of using the part present lasers. This would allow the pick-and-place to skip over parts that were not compressed together properly, instead cycling them back through the machine a second time.
Now I am finally to my problem, the lasers worked perfectly for more than a year. When we switched the input signal in the program to the “Press in Down Position” bit, the Bit Shift stops working. The limit is functional and is seen by the PLC, the “Parts Present” bit will go true but a one is never loaded into the Array. To troubleshoot the problem we branched the rung and added a test bit that we toggle on the fly. When we run the lasers everything is perfect, as soon as we toggle over to the limit switch the Bit Shift stops and when we swap back it will start again.
The table dwell time is two seconds. The “Table in Position” bit and the lasers come on almost simultaneously, whereas the “Press in Down Position” bit lags by about a quarter second. I do not see that this should be an issue because I can manually load the bit while the machine is idle and it takes me far longer than a quarter second but it will accept it. That is the only difference we have been able to find.
Now that I have finished my novelette, hopefully someone can enlighten us as to the error of our ways.
Thank you for taking the time to read.