Part tracking in PLC.

Sometimes to take decisions on a process based on some condition that happened in a previous stage in the process, A typical Example is Sorting based on height where the Sensors to detect the height are installed far away from the sorting table. So I need to keep Track of the status of the Parts and Take the decision later >>> How I can Accomplish This part tracking in PLC Programming ???

I've done this for Goodyear.
We used an encoder on the conveyor to track conveyor speed.
We used a photo-eye to sense the tire.
In the plc memory, I used shift registers to track the tire.
The conveyor speed gives you the rate.
The photo-eye gives you the tire size.
You basically create a shift register in memory.
It basically a conveyor in memory.
But VFDs are basically good enough now a days where I don't think you need an encoder for that basic application.

Ld

I still didn't learn ST, Do you have The Code in LD logic ?

ok, i will have to do this tomorrow when I am sober.

This was a recent thread that dealt with a similar problem, with some possible solutions in ladder:


https://www.plctalk.net/qanda/showthread.php?t=124552


That will not work exactly for your system, but it might giveyou some ideas.

Use a FIFO that count parts being inspected and add height as info to the FIFO at entry, this way you have control for every part in the conveyor, you can not take out or include new boxes between entry and exit. FIFO size must be bigger than number or parts that can be handled in the conveyor.

https://accautomation.ca/plc-programming-example-sorting-station-shift-register/

The above thread may help you out. It is written in ladder logic and demonstrated with Factory IO (3D simulation)

Regards,
Garry

I would use an integer shift register.
detect the art in insert the part number into a register. as the part moves down the line, shift the part numbers down the line.
at the end of the line, you know the part number and what to do with it.
james

Here is some logic for bit & word tracking shift (FIFO) Both use a timer to generate the pulses however, for accuracy it would be better to use a prox on a drive to give pulses, depending on the part size & speed you may not need a fast pulse like an encoder as the shift register would be very large of you could count the pulses (say 20) then use the count to create a pulse & reset the counter so effectively divide by 10. In the word shift data is entered into D0, the shift pulse shifts the data in to the FIFO & then resets the data on the same scan, this stops the data being entered into more than one register. On this application a range of registers at the end of the shift are used to detect the part as using a timer instead of an absolute count from the conveyor may introduce differences in conveyor speed so not strictly synchronised with the conveyor. This window will have to be less than the distance between the parts plus the part width. This was done in GX Developer so depending on your PLC will need to use the equivalent functions.