problems with cura's steps per E wizard

[yoveo 0]

my ultimaker is working very nicely in general. I have one mayor issue though.

I can't seem to get steps per E under control. sometimes it seems fine, other

times there is simply not enough material extruded (never had the issue of

blobbing/too much material. now if I use the wizard to configure the setting

I arrive at around 810 to 820 steps which is nowhere near enough if I then try

to print. I mostly use around 880 steps which mostly works fine (but sometimes

doesn't). have you made similiar observations or is something wrong with my setup?

(note that if I rerun the test and I use the calculated values my ultimaker extrudes

exactly 100 mm, so the calculation at least is correct).

oh and by the way, why doesn't cura have a material multiplier while printing?

that would make it really easy to save a print...

[fuchs 0]

Did you dial in the right diameter for the filament? Step will only affect the length of the extruded material, not the volume....

[yoveo 0]

I don't have a way to digitally measure my filament, but 2.85 should be more or less correct I think.

[fuchs 0]

I don't have a way to digitally measure my filament, but 2.85 should be more or less correct I think.

So you are basically saying that you alter a parameter (steps) but don't find it necessary to validate a second, related (and coupled) parameter? One that accounts for a square function (^2) regarding volume? *ahem*

[yoveo 0]

as I said, I validated the diameter as well as I could.

so you're saying this could account for as much difference

as I notice? I don't really think this can be the issue though,

because my filament is rather more than the stated 2.85

(which would result in more material extruded than set).

[fuchs 0]

You could try to set the number for filament thickness (diameter) to a smaller value, 2.80 or 2.75 while not changing the E setting.

To my knowing (for what it's worth), the E value is quite fixed, as the ratio of movement is dictated by the physics of the stepper motor itself (how far it moves per impulse) and the gear ratios. So as long as the bolt grips the filament tight(!) it should always push 100mm with the same (unchanged) setting for E - because that is basically a linear feeding process. - Just be sure that the bolt grips the filament (you should feel it being pulled into the extruder, when you try to stop it from moving. IIRC the extruder is / should be able to lift 3-5kg of weight when pulling in filament).

The volume on the other hand is a bit tricky, as it depends foremost on the diameter, but that diameter isn't necessarily constant along the length of the filament. I measured one of my 100m spools and found values like

2.76 2.82 2.87 2.83 2.76 2.74 2.79 (actual values from the filament i currently use).

So you can't even be sure that the test you print now is exactly the same as the one with filament 2 meters into the spool.

Also (theoretically) your PLA (if you print with PLA) can accumulate humidity which accounts for volume / diameter but not to plastics (but to vapor). But that's usually negligible.