Program Data Tracking for production line

Hello everyone,

I am in charge of programming a handling system that includes conveyors, cranes, saw, ... on PLC Allen Bradley 1756-L8, and I have to program Data Tracking to tack each product at any time

I will create an instance of the UDT for each conveyor, and when product is moved from one station to another, the data is copied to the next station.

Every thing seems straight forward when it's in automatic mode and the system is running smooth

My 3 questions today are about monitoring this Tracking:

1- Do you think that transferring data from one station to another is triggered by SFC step or conveyor sensors? what about if operator starts conveyors in manual mode where the SFC is frozen or even reset to the initial step??
2- Do you think it is important to create an intermediate Tracking UDT between the two conveyors, so when the product is being transferred to the next conveyor the data is transferred to an intermediate UDT and when the transfer is finished, the data is sent to the destination station UDT??
3- What about Recovering from an Estop, SFC Reset, what are the best practices to handle the Data Tracking especially if conveyors are moved manually by the operator?? I must avoid data shift or loss

I thank you in advance

Yes, tracking the product in any mode is essential, make your UDT moves/copies based on the physical components being satisfied so that that it doesn't matter if the mode is in_cycle or manual (#3 won't matter).

As far as #2, it depends on the mechanics. If its a simple transition, its not needed. If there is a mechanism that facilitates the transfer, then yes.

Is there only one product on a conveyor at a time? If as one product leaves the next is coming, I would have multiple spots. I would make the tracking work the same whether in auto or manual.

+1 for letting the physical inputs transfer product data. No matter the mode.

Also, a word of advice. These systems can start out simple and escalate to a seriously complex system if your brain isn’t kept in check. You will fall down an interlock rabbit hole quick. Especially with sequenced data transfer. That is why you must rely on the physical states to transfer the data.

You may also use your states along with the physical inputs to double verify.

Operators manually running the equipment is going to play havoc. Instead of letting anyone move the conveyors as much as they want all Willy-nilly, can you instead have a controlled jog? Instead of the typical Jog Fwd, opt for “Jog Four Parts Forward” or reverse. Then let the PLC take control.

Recovering from power outage or estop will probably require a sudo setup requiring the operator to confirm the location of the parts is correct.

If the line had RFID tracking or serialized barcodes, it would be a little easier.

I thank you all for your quick reply, here are answers to your questions:

- I have two types of conveyors, those who have only one product at a time and others that accumulates products before transferring them to the next conveyors

- It could be a good idea to get a jog signal as an input and let the PLC controls the manual moves, but the customer specified that the push button stations beside the conveyors are hardwired to the starters/VFD in the MCC, this means as soon as the Local mode is activated using a selector, the PLC doesn't have any control of the motors

- Products are not identified, no barcodes, no labels,.... and no RFID

Now everybody agreed that physical sensors should be used to manage the data tracking, usually we install 3 sensors on each conveyor, One at the infeed, the second at the outfeed and the third one as a diagonal covering the whole conveyor (see the attached image)

In your opinion:
1- what should be the best way to install those sensors to easily manage the tracking and at the same time recovering from Estop or any condition that requires global reset?
2- how the tracking should be programmed? when the product is detected at the outfeed sensor and at the same time at the infeed sensor of the next conveyor, then move the data from actual to the next conveyor??
3- In this case, is it better to use an intermediate UDT, so as soon as the previous point occurs, the data is transferred to the intermediate UDT and when the product is completely transferred to the next conveyor, the data is transferred from the intermediate UDT to the Next conveyor UDT. Is this way would make the system easier to manage and troubleshoot or it will make it more complex?

Thank you in advance for you help

I'm going to go off on a different direction here, and be a bit more specific in handling the data, and hopefully give you some inspiration and decompose the problem.

So, your first concern is about allowing manual running of equipment such as conveyors. I would do a couple things here. First of all, each "section" of the conveyor that has physical controls is its own object with its own UDT. By doing this, you can put the various states of the conveyor such as HAND, AUTO, RUN, STOP, READY, ALARM, etc. This allows you to contain the logic for each conveyor and handle different situations where the operators have intervened.

Now, with the details of each conveyor handled, you can begin using those status indicators to handle how the equipment functions as a whole, together. For instance, if conveyor #2 stops, would conveyor 1 have to be stopped while the rest of product clears from 3?

So, that brings us to the last bit. Each product needs a UDT with its relevant parameters. I have no clue what these would be for you, but you can use bit shifts to track each product through the process, or even better, you can include in your UDT what part of the overall process the particular part is in, and change that part based on certain information.

Overall, you are getting into some very advanced programming techniques, many of which I've never tried to implement from scratch myself. There is also going to be the issue of shaping the product flow to meet your necessary conditions.