Any improvements on the default Raft settings?

[TomniSells 0]

So I've never done a raft before. I don't know if people have improved and experimented with better raft tweaks, or if I should keep everything default as-is. I would appreciate any niche knowledge that I should know about before giving it a go.

[GregValiant 531]

I don't use raft very much.  If I notice a model that may lift (long thin features on the build plate) I typically use "mouse ears" to help adhesion (usually with PETG).  That being said, a raft is just a bunch of heavy extrusions with a model starting on top.  The distance between the top of the raft and the initial layer of the model has a large effect on both Surface Quality of the model bottom, and the release of the raft from the model without tearing up the model.  "Raft Air Gap" and "Initial Layer Z Overlap" have the biggest effect on those.

 

I sliced a model and used a raft with the default raft settings.  Layer Height = 0.2, Raft Air Gap = 0.3, Initial Layer Z Overlap = 0.15.  The first layer of a raft is a negative number and in this example is "Layer:-6".  The bottom of the model is always Layer:0 in the Gcode.  You'll notice this does not match up with layer numbering in the Cura preview which always starts at "1".

Z0.24   (.24) ;Layer:-6

Z0.54   (.30) ;Layer:-5

Z0.74   (.30) ;Layer:-4

Z0.94   (.20) ;Layer:-3 Top layer of the raft

Z1.44   (.50)   ;Layer:0 - The first layer of the model @ [Air Gap + Layer Height] above the raft

Z1.49   (0.05) ;Layer:1 @ [Layer Height - Initial Layer Z Overlap] above Layer:0.

Z1.69   (0.20) ;Layer:2 starts using the actual Layer Height

Edited June 23, 2021 by GregValiant