Inconsistant E-Step Calibration

[adamfilip]

Im tryng to recalibrate my esteps now that im using 2.85mm filament instead of 3mm
recommended esteps for my Bondtech v2 extruder is 510

Using a Caliper i mark out 150mm of filament. I then extrude 100mm so I should have 50mm left if all goes well.
I then use this calculation to determine my new estep value
(old estep value * 100) / (150mm - amount remaining)

I have tried it several times and each time im getting a different result. that can vary 30-40 esteps.
I thought that perhaps my extruder was slipping because im using a thinner filament but that isnt it.. its been tightened and its grip is strong.. its not grinding.. no residue on the hobbed gears. its not skipping steps. and it has ample amps allocated.

Not sure whats going on.

[Roxy]

Well... I guess that should work. What I do is load a light colored filament. Usually white. And I use a Sharpie to mark little dots on it every 5mm or 10mm. I get the first dot to an easily duplicatable place, and then see how much it takes to get the next dot to the same place. This lets me repeat the test several times to get a good measurement.

[Chadd]

That formula doesn't work. You just need to do trial and error when adjusting it.

Im tryng to recalibrate my esteps now that im using 2.85mm filament instead of 3mm
recommended esteps for my Bondtech v2 extruder is 510

Using a Caliper i mark out 150mm of filament. I then extrude 100mm so I should have 50mm left if all goes well.
I then use this calculation to determine my new estep value
(old estep value * 100) / (150mm - amount remaining)

I have tried it several times and each time im getting a different result. that can vary 30-40 esteps.
I thought that perhaps my extruder was slipping because im using a thinner filament but that isnt it.. its been tightened and its grip is strong.. its not grinding.. no residue on the hobbed gears. its not skipping steps. and it has ample amps allocated.

Not sure whats going on.

[adamfilip]

(old estep value * 100) / (150mm - amount remaining)

510 old estep * 100 = 51000
150-55mm remaining = 95
51000 / 95 = 536 Esteps new

whats wrong with this calculation?

[printbus]

Sounds to me like you're marginal on too low of a temperature or trying to extrude too fast for 3mm filament.

[adamfilip]

running 240 degrees with PETG. it flows easily. and I tried extruding at 1mm/sec and 3mm sec.
if I try to extrude too quickly it will skip steps. but it wasnt skipping

[printbus]

I just know that multiple people have found inconsistent calibration results to often be from driving the calibration extrusion too fast for the temperature they're running. There seems to be something more to it than is the motor skipping or not. Maybe increased pressure at the hot end feed changes how the hobbed bolt cuts into the filament. Or maybe there's some skipping occurring at a microstep level that goes unnoticed until there's a LOT of skipping going on.

My earlier testing concluded a 1.75mm hexagon hot end with 0.4mm nozzle topped out at about 300mm/min feedrate. I go for half that or 150mm/min for calibration. Volume wise, 3mm filament would be equivalent at 50mm/min. Your 1mm/sec is in that ballpark. 3mm/sec might be a bit optimistic, at least extrapolating from my 1.75mm results.

FWIW, I also try to be consistent in how each test is conducted. For example, if the hot end has been soaking at idle for long, I'll run a 20-30mm extrusion through, discard it, and then run the calibration length as soon as I can get the filament marked.

[Chadd]

I am not a mathematician so I can't tell you exactly why, all I can tell you is that I fought for a few days trying to get my esteps calibrated using that formula and it never came out right. I finally just started to manually tune it and got it calibrated.

Every time I would use the formula it would either over or under extrude with the calculated estep value.

Get it close then just start adjusting your value a little at a time until you hit your mark.

(old estep value * 100) / (150mm - amount remaining)

510 old estep * 100 = 51000
150-55mm remaining = 95
51000 / 95 = 536 Esteps new

whats wrong with this calculation?

[Alibert]

Remove the nozzle and measure what comes out at the end instead of what goes in. That way you measure the e-steps without any back-pressure buildup in the nozzle, which will influence the transport. The transport thoough the gear or hobbed bolt is influenced by both forces (the stepper pushing and the back-pressure in the nozzle). Have a look at the picture at the bottom of this post: http://www.extrudable.me/2013/04/18/...ty-and-limits/

If you do it that way you should get a much more consistent result.

The back-pressure will always influence how much plastic is actually extruded (as opposed to what the slicer thinks that it is putting out), and depends on the polymer type, temperature and nozzle diameter/friction/fluid_flow characteristics. As you will vary polymer, printing speed (kicks in with the friction stuff) and temperature (viscosity), you wil only get a pretty true extrusion rate at lower printing speeds, or higher temperatures (lowers the viscosity), or general lower viscosity (using other type/brand polymer).

[adamfilip]

I saw someone in a Bondtech forum attach the end of some filament that was in an extruder directly to a caliper head. so when they did a extraction. it would pull out the caliper the exact amount.. it looked like an easy way to fine tune the extrusion steps. I am going to setup a rig and give it a go.