skeinforge - Variable flowrate?

I have a Magnetic encoder DIP extruder motor, but I think skeinforge is not making full use of it.

From what I observe, the flowrate is back-calculated by the maximum feedrate and that's it. That's ok because the machine is ultimately feedrate bound, but when printing the raft-base, the speed is limited by the flow rate, and even my machine is capable at higher flowrate, it doesn't go up. The very same flow rate is used through out the process.

I could imagine changing flow rate in upper printing layer might causes issues because the extrusion rate might not response immediately due to compression of plastics. However, it should be doable to use a different flow rate for the raft.

I think this could be a huge time saver. I bet it wasn't done because not many people has flowrate controlled motor? Or is there any other blocking issue that I don't expect?

I know that on my machine, my limiting factor is not my head feedrate (I have a belt driven Darwin), but the rate of plastic that my extruder can reliably extrude. With my current extruder, an older Mk2 M5 screw drive with an M5 drive bolt driven by a GM3 DC motor and a magnetic encoder, I max out at around 3 mm^3/s of extruded plastic, so I get the extruder running as fast as I can, and then do everything else to match. Any faster than that, and the GM3 overheats, slips the clutch, or something breaks.

I'm working on a stepper driven pinch wheel extruder, which I hope will run a lot faster, which should increase my build speed.

Wade

So in a Darwin it is always extruder flowrate bound? Then that would make sense.

As you can see [picasaweb.google.com], my RepStrap is all metalled. Even if it's driven by ballscrew, there is a lot of inertia (plus the friction is somewhat high, or my motors are not beefy enough.) As a result, the max speed for one axis is 900mm/s, another axis is 1200mm/s. The max acceleration are about 200mm/s/s...Which is fast enough for milling, but pretty slow for printing.

My pinch wheel motor is a 12V DC, 50ohm, geared to be 6rpm max freeload. (not sure about the gear ratio though). It could push a whole lot of plastic out while slipping. 10mm cube/s is not an issue.

I think I am going to hack some Skeinforge speed / raft script to get this. Is there anyway I could contribute the code?...I wonder