Dual Extruder PB+ Project Step 2: Ramps 1.4

[Tdeagan]

[ei8htohms]

Very cool/intense project!

It does seem weird that you can't set separate E-steps values. Maybe you can get around that with flow rate variables in your slicer? Weird though.

[Tdeagan]

At this point I think you're right, flow rate is adjustable per extruder with a recommended value of .9-1.1 and that may well be the mechanism to adjust the Steps/mm. I've been trying to sniff through the code to really understand what the relationship between flow rate and feed rate is. They don't appear to be identical, but I can't say for sure yet.

There's also an adjustable value on the LCD menu labelled 'FR 100%' (percentage changes with the click wheel). It's apparently a global feed rate adjustment, but that seems like a strange thing to adjust in the middle of a print on a global basis. I haven't been gusty enough to experiment with it yet, but hopefully I will soon.

[ei8htohms]

Feed rate is speed, flow rate is volume. If you adjust feed rate during a print (via Repetier or the main "Watch" screen on the LCD with the encoder click wheel) you're just adjusting the global speed of the print. I do use this if I realize I've set the print speed too low and I want to speed things up OR of course vice versa.

You can also change flow rate in Repetier on the fly as a percentage or you can "Tune" the E steps per mm (via LCD/encoder), but I guess that would be for both extruders simultaneously.

Some folks have reported using the Flow Rate Tweak separate from the E steps per mm setting to control extrusion width in a manner I don't quite understand however, so maybe there's more to that adjustment than I know (or less than they think? ).

[Tdeagan]

Good description! Thanks!!

The more I work with it , the more I want to mod the LCD menu. The FR setting is global (X,Y,Z,E), I'd _really_ like to have controls on the LCD/encoder to mod the flow rate of the Extruders individually (or even as a pair via steps/mm, but if I'm going to hack it, might as well try for what I want.)

I'm with you on not totally understanding what parameters, other than Extruder Steps/mm, would impact the extruder flow rate. Given that there is no per-extruder steps/mm setting, I'm dead curious what parameters are being modified (either via the LCD or via the slicer,) to tweak it. I suppose the only other factor is the time domain, so perhaps it's all some integral of mm/sec that's being tweaked.

I need to find a lot more time to trace the code. The arduino editing environment is a weak multi-file dev environment. I need to build it all out in Eclipse or something.

[ei8htohms]

It may also be worth reading what Triffid Hunter has to say about e-steps, flow rate and filament diameter:

http://reprap.org/wiki/Triffid_Hunter's ... tion_Guide

He seems to think that they all affect the same parameter (volume of filament extruded) and recommends simplifying them to the easiest tunable variable. While this approach seems sensible for single extruder machines, it also highlights the possibilities for tuning different extruders as well.