There are a lot of settings in Skeinforge, which can be intimidating, but there are only a few that really matter. You access the different categories of settings through the rows of buttons.
If you don’t have heated build platform, you will want to use Raft. This is a first layer made of wide, thick lines designed to stick hard onto the bed and prevent warping from the plastic peeling up. Aside from turning the raft on or off, there is no need to change any of the settings that determine how it is drawn.
The next layer up from the raft is the interface. This is a looser, thinner set of lines that go between the raft and object, to make the raft easier to peel away from it. Turning down the temperature and flow rate a little can help keep it from sticking too hard.
Object First Layer settings affect the first layer of the model itself. If you are not using the raft, you can change the settings for the first layer only, to help it stick to the bed better. Feed rate is the speed the extruder moves over the platform. The multiplier determines how much faster or slower it goes compared to the overall Feed Rate set under the Speed Tab. Flow Rate is the speed the plastic is extruded. The multiplier sets the speed in relation to the overall Flow Rate set in the speed tab. A 1 means 100%, or the same speed. .8 is 80%, 1.2 would be 120%.
You can help the first layer of the model stick by slowing the feed rate a little, or raising the flow rate to push a little more plastic down. Most of the time you would leave this alone, because you can use the Z offset screw on the printer to control the stickiness of the first layer.
A model is built in 3 parts. The solid layers at the top and bottom, the walls (perimeters or shells) and the fill.
Extra Shells determines how many outlines are drawn to create the sides of the part. The more shells you have, the thicker the walls. If the model has a gradual curve to the top, such as a fillet, you may need more than 2-3 shells. If you don’t have enough shells, then as the curve nears horizontal one layer may be set far enough back from the layer below that it doesn’t reach the innermost shell of that lower layer, leaving a gap. You can see that happening around the neck and ear of the yoda print below.
Infill is the plastic inside the “solid” portion of the object. There is no need to fill it completely with plastic, and Infill Solidity Ratio is where you determine how dense the fill is. The higher the ratio, the longer it will take to print because of all the lines that must be drawn. It doesn’t take much to make a strong part. Large amounts of fill will be able to apply more force to the sides of the part as the plastic shrinks, and increase the chances of warping. .2 (20%) is a good number to start with.
The Grid settings determine the shape of the fill pattern. Hexagonal and Rectangular are strong, but Line can print faster.
The last setting under fill you want to think about is Solid Surface Thickness. This is the number of layers used to make the top and bottom of the model. The first layer is usually sparse because the threads tend to droop into the fill, depending on how loose the fill pattern is. Each layer will droop less than the last until there is a solid top. The more sparse the fill is, the more solid layers you will need to cover it. 3 solid layers is a good starting point.
Most of the time you won’t need to adjust anything here. Feed Rate is how fast the extruder moves, and Flow Rate is how much plastic it pushes through. If you are finding that the threads are squished together on solid layers and pushing up plastic that the extruder is dragging through, then flow rate might be too high. If the threads are barely touching and you see gaps between them, then Flow Rate might be too low. Don’t judge this by the first layer however, because this can be affected by the distance between the nozzle and bed, as set by the Z screw.
If there is a problem with the extruder pausing around complex perimeters, as in the first Yoda post, you can help this by slowing down the printing of the perimeters. Setting Perimeter Feed Rate below 1 will slow down the extruder so it can print the outlines with more precision.
Most of the time, 195 is a good temperature for ABS. Higher temperatures stick better, so if you are having problems, you can try setting the Object First Layer temps to 210. If you are using a raft, the set Base Temperature to 210 (Base is another term for Raft). Object Next Layers is everything else, so set that to 195.
Something that may come up is the need to cool. If you have a model with small areas like narrow columns, it might only take a few seconds to draw each layer. As a result plastic will be extruded onto a layer that is still slightly melted, pushing it around. Minimum layer time assures that each layer will have at least 15 seconds (or whatever is set) to cool down, either by the extruder running circles doing nothing for awhile, or it could slow down the Feed Rate so the layer takes longer to draw.
For most things, the defaults will work, but this should give you an idea of what you might adjust on a part to part basis. The main ones will be Solid Layer Thickness, Infill Solidity Ratio, and Extra Shells.