[solved] Capacity Constrained Resource - how to setup?

We have got an oven to heat up material in some routing task. This oven needs setup time to heat up and to cool down. Thats not a problem.
This oven has got a physical capacity which is measured in volume or in some units of loading equipment. (e.g. spindle)

Now we want to limit the capacity of this oven up to a concrete volume or a quantity os spindles.
How can we set this up?