Volumetric Dimension settings

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Skeinforge 040 introduced some changes based on the Volumetric 5D skeinforge plugin. With 040, skeinforge calculates how much plastic, by volume, is entering the top of the extruder per step, and therefore how much plastic is being pushed out the nozzle per step.

In other words, if 1 cm^3 enters the extruder, 1 cm^3 must exit the extruder.

(In actuality, some plastics like ABS break down or out-gas a bit and decrease in volume. 'packing density' must be lowered for ABS)

So now we don't need to change feed/flow rate in order to get good prints. all we need to know is how much plastic is entering the extruder.

The biggest change that must be made is recalculating your E_steps_per_mm firmware setting. You need to know how many steps it takes to move the feedstock 1mm into the top of your extruder.

here's the basic formula:

micro steps per rev * gear ratio / ( pinch wheel diameter * pi)


Wade's Extruder

  • gear ratio: 39/11
  • pinch wheel: 8mm hobbed bolt. probably between 7-5 mm


Adrian's Extruder

  • gear ratio: 59/11
  • pinch wheel: 7mm


Herringbone Extruder

  • gear ratio: ?
  • pinch wheel: 8mm hobbed bolt. probably between 7-5 mm


Universal Mini Extruder

  • gear ratio: 31/11?
  • pinch wheel: 8mm hobbed bolt. probably between 7-5 mm


Please list your e_steps_per_mm below, so that other reprappers have a data point for comparison:

Wades - .9 degree stepper x 8 microstepping: 722 steps/mm