Configuring Skeinforge: Some Basic Terms…

I’ve gotten a bunch of questions lately about configuring Skeinforge, the program MakerBot people (and others!) use to take a 3D model and turn it into a gcode file. I’m sure there are others around who are a lot more up on how Skeinforge works than I am but, unlike me, they have the good sense to keep quiet about it.

I confess to not really knowing where to start but I guess some terms & definitions are probably as good a place as any. I’m going to err on the side of defining most everything I can think of here – you likely know a lot of these already..

The goal is to define enough things that you can take just the stuff below and at least get a decent idea of what most of the common settings mean in Skeinforge.

Flow Rate: This is how fast the extruder is taking in a given length of filament. More on this in the next blog.

Feed Rate: This is how fast the build platform is moving, in milimeters per second. Again, more on this one next time. (feed and flow rate are Really Big Things and are too much to talk about here..)

Thickness: Any time you see the word “thickness” think “height” instead.

I say this because the word “height” is pretty much always talking about how tall something is, top-to-bottom. The word “thickness” can indeed mean height but, at least for me, is more frequently used to describe a more front-to-back type measurement.

You can think “thickness” any time you read that word if you’d like but keep in mind that any time Skeinforge uses it, it’s talking about how tall something is.

Width: Width really does mean “width” and in particlular, it means the width of a line of plastic (a thread) in your print. Note that this isn’t the same as the width of your nozzle or the width of the plastic coming out of the nozzle (which, for ABS, is a bit wider than the nozzle size).

Perimeter: This is the term for things on the exterior of the object – stuff that touches the air.

That’s not exactly 100% true. Say you were to print a hollow sphere or something like nophead’s dodecahedron, which is mostly hollow. The exterior parts of the object – the bits you can touch on the finished print – are all perimeter but the surface of the inside wall – the parts that touch the bubble of air in the center – is also considered part of the perimeter.

Different example, in 2D: imagine drawing a large letter O on a piece of paper. Two circles with the stuff between scribbled in. Both the outer and inner circles are perimeter. The scribbles in between the perimeter lines is infill…

Infill: Infill is all the printed stuff inside the perimeter lines.

Sometimes, things you think should be perimeter are actually infill. You can tell Skeinforge to print multiple laps (shells) around the perimeter and if you’re looking down at the top of a print, they look just like the perimeter threads but they’re infill – only the outer lines are perimeter.

You can tell skeinforge to not totally fill in solid parts of an object and it will happily do that by drawing tons of little squares (or lines or hexagons or circles – you can change the infill pattern) instead.. Note that even though they’re surrounding little bubbles of air inside the print just like my example in the perimeter stuff above, they’re still all infill – what is perimeter and what is infill is more about the object model itself rather than the way it’s printed.

Shells: Shells the lines around the perimeter. Again, the very outer shell line that’s at the edge of the object is perimeter and the others are all infill shell lines.

Over: Over just means “divided by.”

There are 197 “A over B” parameters in Skeinforge. A value of 2.0 for “A over B” simply means the value of A is twice the value of B. A 0.5 means it’s half the value. A 1.0 means A and B are the same.

There are too many of these ratios and they make my brain hurt. If math isn’t second nature to you (and it’s not to me) just remember that a value greater than 1.0 means the the stuff before “over” is bigger than the stuff after it and a value less than 1.0 means the stuff before “over” is less than the stuff after it.

Multiplier: Similar to “over”, this is short hand for “some value over the normal value for the rest of the object.”

If you see something like “Infill on Every Seventh Layer Multiplier” (and you won’t actually see that) it’s the same as “Infill on Every Seventh Layer Over Infill on the Rest of The Object”.

Orbit: Sometimes Skeinforge needs to waste some time. When it does, it “orbits” around the print. Basically, the extruder turns off and the build platform slowly moves around, not really doing anything except moving around.

This is frequently related to temperature changes – if it thinks it needs to do a temperature change it will orbit around the print until the temperature should be right, then go back to printing.

Travel: When Skeinforge needs to stop printing at one spot, move to another spot and start printing again, it’s travel.

This is different than orbit in that orbit is just wandering around, killing time. Travel is when it’s actually trying to print but needs to move to a different spot without putting down any plastic.

Raft: The raft is a sort of a foundation layer that can be put down beneath the object. Raft’s usually have more width and height than the normal object lines and are painful to watch because they frequently print pretty slowly.

Raft’s are good if you don’t have a heated build platform or your platform is banged up or isn’t very level. The big, thick lines fill in divots in the platform and help level it out a little. They also have good adhesion, which helps prevent warping on large prints if you don’t have a heated build platform.

The raft isn’t part of the object itself – it’s meant to be removed later.

Base and Interface Layers: These are parts of the raft. The base layers are on the bottom – right up against the build platform – and the interface layers are between the base layers and the object.

Base layer threads are typically a lot bigger than interface layer threads and people frequently disable the interface entirely, since it takes a fair amount of time to print and can be difficult to remove.

Base layers are always drawn on X and interface layers are always drawn on Y. If you have multiple base layers, they will sort of stack up instead of printing in alternate directions like object layers do. Same with the interface layers – they stack.

Object First Layer: Just like it sounds, this is the very first layer of your object. If you are printing a raft, this is the first layer above the raft.

Bridge: I’m actually not really sure on this one but believe bridges refer to printing over open spaces.

For example, if you had a model of the letter H standing up, the center horizontal bit would be a bridge. I think just the bottom layer of that center bit is bridge but could be wrong..

edit: nophead says: Yes bridges are where filament has to span a gap. “Infill in the direction of bridges” tries to get the infill lines in the direction of the bridge so that both ends are on something solid. Diagonal infill does not work unless the ends have something to land on. (thanks, nophead!)

Next up: The 4 (or 5) big settings that make up a profile..

PS: there’s a bunch of people to thank for the things that are right in these blogs (but not the stuff I’ve gotten wrong) . In particular, the www.BitsFromBytes.com wiki pages on Skeinforge, Nick Ames, nophead and Jordan Miller come to mind. There are probably more but those ones stand out. Thanks, folks!

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10 Responses to Configuring Skeinforge: Some Basic Terms…

  1. nophead says:

    Yes bridges are where filament has to span a gap. “Infill in the direction of bridges” tries to get the infill lines in the direction of the bridge so that both ends are on something solid. Diagonal infill does not work unless the ends have something to land on.

  2. Luis Rodriguez says:

    This is a great simple way to explain these parameters! Can’t wait for subsequent posts! Let’s make sure this kind of language makes it on a wiki somewhere! http://wiki.makerbot.com/skeinforge ?

  3. Great article, this helped a lot ! It made clear so many basic terms that this was definitely needed. Thanks !

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