So my prints suffer from over-extrusion but the flow rate fields in cura doesn’t seem to be working. I’ve made countless attempts trying settings ranging from 100% all the way down to 60% but nothing actually changes when I print. I thought I was going crazy until I saved the gcode before and after changing various flow settings and confirmed the gcode command values remained unchanged. It acts like cura simply ignores the filament related setting fields (flow %, diameter, and e-steps). Other settings work fine. Interestingly I’ve also noticed the print estimate stats (minutes, meters, and cost) also don’t change; filament diameter, for example, should certainly affect the filament length estimate! It shows it recalculating but then updates the estimates with exactly the same values - I assume this is the same issue.
I’ve tried resetting to a default profile. I’ve tried restarting cura in between setting changes. I’ve tried the newer cura for windows (v21.04 vs v21.03). I’ve tried numerous models. Nothing seems to matter.
Help! What am I missing? Since these three fields have clearly worked for others on this forum I don’t understand why it would be different for me unless I’m literally the only one here using the lulzbot version of cura.
Update: If I manually edit the gcode to reduce the extrusion values in every line to 1/3 the size the models print flawlessly. I assume this confirms this is a software issue (bug?). This highly manual workaround is super-miserable, however, and a terrible solution.
Some files attached if anyone wants to see the gcode (and test model) for themselves.
If you compare the two 2.85mm gcode files with any text editor you will see they are identical even though I decreased the flow setting to 80% in one of them. I would expect Cura should have reduced the filament feed values seen in that file by aprox 20% but it appears the same. If I print instead of saving gcode they also come out the same.
I also included an example where I instead reduced the diameter from 2.85mm to 1.75mm. Again - the gcode values remain identical. The only difference is the comments at the top that include the estimates (appear bugged). I would expect the length of filament needed should increase while weight and price would stay the same. Instead length stayed the same and weight/price went WAY down (1/3 the size). This makes zero sense.
Why is this happening? It doesn’t sound like this is happening for others even though I’m trying to stick to default settings for everything else.
test stl (1.75mm, 100pct flow).gcode (78.2 KB)
test stl (2.85mm, 80pct flow).gcode (78.2 KB)
test stl (2.85mm, 100pct flow).gcode (78.2 KB)
test stl.amf (1.14 KB)
Slicers may factor other variables into the “flow rate”, but ideally, it would be a the one “F” value. Various parts of the print may utilize different flow rates.
Try printing the peg in cylinder type test. Ideally you should notice a sloppier fit when the flow rates are lower.
I print a thumbcap that snaps on to a socket cap to gauge dimensional accuracy and use flow-rate to help compensate looser or tighter fit.
If you want to continue analyzing the gcode, do a diff between the two files and determine the % difference in different F values. Maybe not all the F values are affected by the flow rate.
Might be a misunderstanding… I’m saying the flow rate setting has zero impact anywhere. Every single extrusion value in the entire gcode file is identical to its matching line in the other file. 0% difference. 100% match. Put another way: You can alter the flow % as much as you want and it won’t change a single character in any gcode line.
BTW: Since my first post I used MS excel and a text editor to modify the extrusion values in every line of the gcode. If I modify every extrusion value (multiply by 0.35), update the gcode, and print from cura the models are flawless. This seems to prove this is a software issue - specifically a bug in cura’s flow calculations. Still don’t understand, however, why I’m the only one noticing it and even if I write a more automated script to fix cura’s gcode this is a miserable workaround that adds many steps to each print.
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