Skeinforge Quicktip: The Raft, Part 1

The Raft is pretty important to a print job.  Smaller prints might squeak by without a raft at all, and middle size ones won’t curl up too bad if the raft isn’t there or is defective, but for big jobs, the raft is mandatory, and a build won’t make it if its raft isn’t laid down right.

In skeinforge terminology, the Raft consists of two parts: the Base and the Interface.  The base is a set of thick, heavy lines whose purpose is to glue the raft to the build base.  The Interface is the relatively thin lines that criscross on top of it to provide a level surface for the build.

The Base layer thickness over infill thickness is the speed of the print head relative to the standard feedrate.  Moving half the speed as in the above settings, the print head deposits thick plastic which sticks to a build base like hot glue.  (Like hot glue though, it’ll peel off if you stick your fingernail under it.)  The Base Infill Density is how far apart these layers are, set here to have a spacing between them about equal to the width of the lines.  (Hence, a density raio of one half.)

The Base Layers number is how many of these layers are used.  I have only used one layer for builds with a raft, or zero for builds without one.  Making the nozzle lift less than one standard layer (here it’s 0.75 of one standard layer) means that the nozzle will not raise up as far as it would for a standard layer, which like the other options is designed to flatten the plastic of the raft out so it will be better as a glue for holding the object to the build base.

These numbers repeat for the interface, and mean about the same thing.  So far I’ve used 1 or 2 layers for the interface, depending on how worried I am about the object curling up.

I have done builds without rafts on occasion, when a build is small enough that I’m not worried about it curling up.  However I never do it by clicking those disable check boxes.  Doing this seems to make Skeinforge center the build around zero, which can make it very tricky to correctly position the print head.  A better solution is to leave the raft turned on, but set both the base and interface layer counts to zero.