The original pinch wheel pulley has an “effective” diameter of 9mm (assuming you push the filament all the way into the pulley’s teeth).
The worm-gear style pulley has a OD of 10mm and the grove is 1,5mm, so the effective diameter should be around 7mm.
This makes a difference of 1mm in the radius and thus approx. 3mm less feed per revolution with the worm-gear style pulley.
So now the funny part of calculations (please correct me if I made a mistake here…): Since the filament has 3mm diameter and is extruded at approx. .5mm, this should result in 9x less extruded .5mm plastic, i.e. 27mm less extrusion per revolution or 54mm less extrusion per minute (given the full 2RPM of the Kysan DC Gearmotor). That’s .9mm less extrusion per second, let’s say 1mm/sec to make things easier.

The “usual” feed rate on a MakerBot is about 26-28mm/s, so the 1mm difference of extruded plastic shouldn’t do too much harm. If necessary, you could either slow down the feed rate a little bit (well, 1mm/sec less…) or adjust the layer thickness a little bit. But given the relatively small difference, the decrease of layer thickness should be really, really small.

Go!

=ml=

First, thanks for the great blog!

I just got my build 11 makerbot last week and made my first test prints yesterday! I started with a cube and then printed your whistle v2.

My skeinforge settings are not nearly as nice as yours. When I print from the stl file on thingiverse it has huge gaps, when I print from your gcode everything comes out beautifully.

Have you by any chance made your skeinforge settings from that build available anywhere? Or was the gcode produced by your Pleasant3D software instead of skeinforge?

Thanks!

–Derek