Usage of IT PLC (MES in vehicle manufacturing)

IT PLC is widely used in vehicle manufacturing system, such as Ford NGAVS and Volvo ANDON.

This article will introduce the function and architecture advantage of IT PLC.

Normally Andon system has its own PLC, because it’s very convenient to connect lots of lineside hardware into single PLC.

In case of Painting Shop, lots of ropes, speakers, screens are installed distributed, if we connect them to conveyor PLC, then there will be lots of conveyor PLCs need to connect and integrate.

And with Andon PLC, together with remote I/O stations and Fiber network, we can connect all hardware into same network, so it will be very convenient to install and integrate, and it has lowest risk of impacting production.

Now let’s take an example of AVI system, without IT PLC VS with IT PLC.

Diagram 3.6-1 shows architecture without IT PLC:

Diagram 3.6-1: AVI without IT PLC

 

Diagram 3.6-2 shows architecture with IT PLC:

Diagram 3.6-2: AVI with IT PLC

 

By comparing these 2 architectures, we can see IT PLC’s functions:

First, from point view of conveyor vendor, by removing AVI Data Block and Function, conveyor PLC’s business logic is quite pure, and has lowest impact to production. PN/PN Coupler can map data from Data Block into I/Q Area, it’s very easy to integrate. Their project only has business Data Blocks and Functions, it’s more stable, and has low coupling level.

Second, from point view of AVI vendor, because AVI Data Block and Function are installed in same IT PLC, so they don’t need to consider the difference between conveyor PLCs, that means it can suit all stations. And there’s no any conflict of Data Blocks/Functions/Timers/Counters, so it’s much more simple to develop and debug.

Besides that, IT PLC can also provide some additional functions such as data buffer. Considering lineside control network is much more stable than IT network, we can buffer Orders after they are downloaded to IT PLC, and we can also buffer vehicle travel record into IT PLC, so lineside control system has a soft coupling relationship with MES, so it has lowest impact to production.