fix raft model spacing

src/mode/fdm/prepare.js

@@ -147,6 +147,7 @@
 
                 // raise first layer off raft slightly to lessen adhesion
                 firstLayerHeight += process.outputRaftSpacing || 0;
+                zoff += process.outputRaftSpacing || 0;
 
                 // retract after last raft layer
                 output.last().last().retract = true;