Layer height if raft specified
If Layer Height and First Layer Height are different. What layer height is used for the raft and is the first layer height applied to the part or the raft (or perhaps both)?
RE: Layer height if raft specified
The support layer for the raft itself (the layer in contact with the bed) will be whatever your first layer is specified at. The raft itself will be, well I'm not sure as its a support layer and that's controlled by slicer and support uses variable layer thickness so it can change.
Here is the important one though and the reason you should never use a raft unless ABSOLUTELY necessary, your bottom layer of the model will be whatever your nozzle diameter is. So for a 0.4mm nozzle the layer will be 0.4 thick. You have no choice about that. Printing on a raft is the same as printing on support so in effect bridging as far as PS is concerned. As such Prusa Slicer treats those as being the extruded nozzle diameter as there is no squish with the layer below. You will see them in thick blue colour just like any other overhang/bridging perimeter.
Rafts were traditionally used to compensate for beds that were not very level, to increase adhesion. With a modern bed that is leveled well (or using mesh leveling) and with a PEI surface there is very little reason now to actually use a raft. If you are having first layer problems then its better to sort that out another way.
If your print surface is not even then its better to increase the first layer height slightly to try and even it out (so up 0.2 to 0.3 for example).
Btw if you have similar questions then in future you could just slice a model and then on the preview just change type to height. That will show you exactly what layer heights Slicer is using for the different bits of the model(s). The preview with all its various settings can tell you a lot about what slicer is doing.
RE: Layer height if raft specified
@neophyl
Woq, thanks for all that info, all news to me. I've usually avoided rafts if for no other reason than lose of nice flat "touching the bed" surface. I do sometimes use then where a curve meets the bed a bed at right angles (can't think of anyway to explain better), the raft make for a slightly less ugly first few layers.
RE: Layer height if raft specified
Later edit for Woq read Wow