Extruder Steps per/mm changing with extruder temp

so im been trying to work out my steps for mm for the extruder, but im having issues of how much it extrudes each time

the lower the temp the less it extrudes and the higher the temp the more it extrudes

im testing with PLA ive tried 190c 210c and 225c and each one gives a different result…

the feeding gear isnt slipping to my knowledge, i tried holding the filament and it keeps pulling with alot of force

the feed speed 60mm/m

190c - extrudes 90mm
210c- extrudes 99mm (what im calabrating it at till i found this bug)
225c - extrudes 105mm

all the tests are out of 100mm extruding, so its not a small amount

how do i fix this? is it a setting in the Marlin software that is controlling it?

EDIT - so i thought maybe it was feeding in to fast, but i dont think that is the issue but the results are different again

i extruded 10mm/min so super slow…

190c extruded 102mm
225c extruded 106mm

to me its looking like its struggling to feed, but at that slow rate, i dont understand

im using the e3d v6 with titan extruder, marlin software

Heya, perplex.

What happens if you take honey out of the cabinet and try to pour it into your tea? Then what happens if you microwave it for a few seconds?

Essentially, you are changing the viscosity of your plastic as you raise the temperature. You should expect it to extrude faster at higher temperatures.

Set your rate based on the proper temp for the material. If you switch materials often, most slicers have a way for you to adjust your feed rate as a percentage of the firmware setting.

-Stefan

yes i understand your honey reference but i still disagree because this is mechanical

the extruder works on step counting, so mathematically it should always be the same, if the extruder is to cold then it will skip steps or slip on the filament, if its to hot it will only push in the required amount still.

so from me saying that, it means i must have be skipping steps or slipping, or something in the firmware doing it.

i recently had a thought, if the motor isnt powerful enough, what happens, will it just slow down and not skip steps? like stalling? because if thats true then im going to swap back to the original motor and test

You’re absolutely right about the motor partitioning a measured length of material.

Are you measuring the length of material going INTO the extruder or the length going OUT of the extruder?

The filament flowing out of the extruder will be impacted by the temperature.

yes, i measure it going in. using Toms guide on youtube

the temp shouldnt have any effect, unless the motor is skipping or slipping ect

so i swapped the motor and same issue, so its not skipping steps or under powered

only one i cant really test is if the filament slips, but i dont think it is since i cant even move it when i try pulling it.

so it must be a setting in marlin, i dont understand why it would push more filament through when its hotter

ideas?

Ok, I think I’m all caught up. I agree, temp should have no impact on the incoming filament. I’m not too familiar with 2.0, so I don’t know if there is a setting for extrusion adjustment based on temperature.

I’d look at the teeth marks cut into the filament as it passes the extruder. Extrude a bit then reverse. See if the hobbed gear is mangling the filament.

still using 1.9

i checked the filament and it looks good, a nice hold

i did more tests

i took the extruder off set the temp to 190c and 225c and they were only .5mm off so ill call that margin of error, so that means its not the firmware, i then put the extruder back on with the new settings i just got from using no extruder and tested it again, 9mm under extrusion at temp 200c

so its not the firmware
not the motor

it has to be slipping on the filament… but i cant even pull it out myself…

unless there is something im not thinking of…

I’d definitely check to see if the extruder gear is chewing the filament. It might be holding on tight but not moving it forward. (Higher temp means lower viscosity, which means less pressure & less resistance to feeding).

The only other thing I can think of at the moment is if you have an inconsistent filament diameter. It would be odd that it always extrudes more at higher temps.

yea, i did a test and i think its slipping somehow

i guess i just need to tighten it even more, ill have to do more tests but so far it seems that its slipping

i wonder is the cog teeth are to far apart and when it finished with 1 tooth it slides back abit, i guess making it tighter should kinda fix this

Be sure to look at the filament as it passes the extruder gear. It is actually possible that it is too tight, too. There is definitely a sweet spot between the two.

well i cant do any more tests, my extruder fan wires broke, so ill have to get new fan before i can test more.

but i did 1 more test with no extruder attached and i got the number that it should be, so when i get the fan back i just have to make it work somehow

here is a picture of the extruder gear bite in the filament, thats with the titan screw half in, quite tight imo

Those grooves look about right. There must be some slipping due to pressure in the extruder but not enough to cause missed steps.

I’d just tune it to based on the right temperature for the filament and see how it prints. The real world has a funny way of messing with those perfect theoretical values.

-S

well i got my fan, did the test without the extruder nozzle, then put it back on and it was 6mm out. think im going to give up and just hope it works fine lol

A lot of this is still just an art. If your prints look good, what’s 6% ?

yea thats true, they seem to be looking good, just need to stop it from warping, think my cooling is to much