Looking at Dave’s Profileinator seems really well suited to a stepper extruder. However, he also suggests adding a “Flow Fudge Factor.” I just use this set to 1.0, so I’m not sure if I’m using it correctly.
Flow Fudge Factor: I have to enter 1.0 into the flow rate to get 2.0 RPMs on the extruder.. I got tired of doing this math so I added flow fudge factor and set it to 0.5. This doesn’t change the volume calculations – it just modifies the flow rate on the table. If you have a MK4/MK5 extruder with a DC motor, start this at 127.5 to get the PWM value to use
In any case, it looks like by multiplying it by 127.5 you can get the required flowrate for a DC motor. In printing with a DC motor, I never wanted to drop the speed below 255, because the DC motor had such a small range of speeds. I could print between about 230 – 255. Given this, I can understand why so many others, probably using a DC motor, would rather pick their flowrate as 255 and then determine the proper feedrates.
Flow fudge factor has to do with the weird compression noticed in ABS. For some reason when printing in ABS the material compresses to about 85% volume compared to the volume of the filament going into the extruder. PLA does not have that problem and you should run it at 1.
@Aaron: That’s what I’ve been using in the new development version. If you’re willing to help test it, I’ll give you a link. :)
Actually, the flow fudge is because when I tell my extruder to do 1 RPM, it does 2 RPM. Or if I tell it to do 1.5 RPM, it does 3.0 RPM. Rob says it’s a firmware bug but I’ve been too lazy (and damned busy!) to track it down or use a different EC FW.
Anyway, I set flow fudge to 0.5 and it tells me the values that *I* should use. If you get 1.000 RPM when you set it to 1 RPM, you should use a flow fudge of 1.
The horrible named “gear swell mod” is for the ABS compression/volume loss/gear grab diameter/etc.. That’s the one that accounts for apparent volume loss.