Start with one cell that has a clear customer and find a way so that the cell owns all its own finished goods inventory: its shop stock. As with any bakery, the cell is now responsible for serving its customers.

Then get the following process to come and pick up what it needs as it needs it; either by coming to pick up themselves, or with a logistics small train.

Set up a simple kanban system (think of cheques to purchase the products) and ask the two cells, customer and supplier, to coordinate, until you all see together the impact on quality, inventory and flexibility.

How best manage suppliers?  
How do we manage our stock to be lean and responsive to varied customer demand?
Should we plan according to what we can do, or the other way around?
I've had visible results with lean but my corporate colleagues want to force their ERP and purchasing practices on my division. Any advice?
How do you suggest we should do lean in a foundry?