Extruder feedrate for Z moves are too fast
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I was playing around with this tool mentioned on CNC Kitchen to determine my maximum feed rates for fast prints, but even a supposed feed rate of 2mm3/s (well within a normal print feed rate) was causing my extruder to skip.
Looking at the G code, this command is supposed to extrude 200mm of filament in a 10.5mm high pile, with a 2.49 mm/min feed rate for the Z movement (you then weigh the pile and compare it with faster extrusion rates to determine the point at which you start under-extruding).
G1 Z10.5 E200 F2.49 ; Extrude 200mm at 2mm3/s
However that pile completes in about 20 seconds, meaning (if my calculations are correct) that this is trying to extrude at 24mm3/s, which would explain why my extruder was struggling.
The question is, why is my extruder trying to feed faster than the G code specifies?
Obviously extruding during a Z move is not normal, so not something I would have noticed before. I can't think of anything in my config that would affect this, is this an issue with the way RepRap FW interprets an extrude during a Z movement?Hardware for this test:
Duet 2 (Fw.3.2)
E3D Toolchanger
Hemera hot ends
0.4mm nozzle -
@ByteSized Is that feedrate correct? I make 2.49mm/min to be 0.0415mm/s which is pretty slow. It is also below the 0.5mm/s minimum feedrate that is used by RRF (see: https://docs.duet3d.com/en/User_manual/Reference/Gcodes#feedrate), the 0.5mm/s rate would give you the 20 seconds I think. It seems you can change this minimum with M203 and the I parameter. Might be worth trying that?
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@gloomyandy
Yes, I think 2.49mm/min would be correct to get you a feed rate of 2mm3/s.
I think you are on to something with the 0.5mm/s rate, if that's being enforced that would explain the too fast extrusion and it indeed matches the 20 seconds I'm seeing, I'll give "M203 Innn" a go, thanks.
