Repetitive Manufacturing

Dear Gurus,

In Repetitive Manufacturing, we create a work center of Category 'Production Line' which has a Cost Center assigned to it. We also create a Product Cost Collecter for the REM Material. What is the need of Product Cost Collector, and how is it working differently for cost center assigned to work-center

Also I hope we use Planned Orders and not Production Orders in Repetitive Manufacturing. How is the Planned Order confirmed in Repetitive Manufacturing.

Thanks in advance.

Sachin