Skeinforge QuickTip: Tweaking the Speed Knob

Skeinforge: Too Many Options

Skeinforge is a pretty big bundle of scripts, and having a first flawed build as your only reference point for going in and fixing the settings can be a pretty daunting task.  Rather than try to provide a full manual, I’m going to present this the way I learned it: one feature at a time.

There are probably well over a hundred teeny tiny knobs you can turn on this beast, but the first one we’ll cover, and one of the more important ones to getting decent builds, is the Speed control:

The Speed dialog box controls both how quickly the XY CNC machine will move and how quickly the extruder will push the filament.  If your default settings are giving you messy or stringy builds, this dialog can probably help you.

Key vocabulary words here: Feedrate and Flowrate.  Feedrate is how fast the tool head moves (or in the case of the MakerBot and McWire, how fast the XY table moves) and the Flowrate is how fast the extruder is extruding.  For a clean build, both of these need to be about right with respect to each other, and unfortunately I’ve found it to be a bit of a trial and error process.  (MakerBot users: got a favorite setting for this?)

I like to start from the assumption that I want maximum flowrate (255 on PWM settings) and then set the Feedrate high enough that the bot moves so quickly that this is okay.  This can cause trouble if you’ve got a bot that stops at the end of a line segment in skeinforge, as your effective feedrate will be much slower in more polygon-dense areas.  However, I think the current firmware for the MakerBot and other Sanguino-based implementations has buffering which solves this problem, so going for a high feedrate/flowrate pair is probably ideal in most cases.

With the flowrate set where you like it, you’ll find higher feedrates result in stringy, sparse builds if it’s set too high, and gloppy, heavy builds which rip off the build base as the nozzle picks past dried plastic if it’s set too low.  (I find the latter is way more unpleasant than the former, so I shoot high on feedrate.)

More Skeinforge tips to follow: one bite at a time, it is learnable.