Extruder drive stalls after retraction

[msdevstep]

I'm having an issue where anytime I try to go higher than 38mm/s on a retraction, the extruder drive will stall after a retract when the drive is trying to return the filament to the original position. The retract is always smooth, but when it tries to push the filament back into nozzle, the drive just stalls. The drive bolts don't slip, instead the motor just stops. After a stall, when the drive returns to normal extrusion speed, everything works as it should, but now there is not enough filament in the nozzle for a short time and causes holes. I've tried running the head hotter, adjusting the POT on the stepper driver both ways until I'm sure it's now set for max torque, and also fiddled a little bit with the acceleration constants in the firmware (but have since restored the defaults). Additionally I've tried shorter retraction distances, but it makes no difference, as it won't go any higher than 38mm/s. Reading on these forums, it seems that others are able to get 60mm/s out of theirs.

I really need this to go faster because I'm almost rid of travel strings, but still get little towers building up in the middle of travels where the head is still oozing and drags on the extra plastic from previous layers. I have my travel speeds very high and feel that if only I could get pressure in the nozzle lower quicker, then these things would disappear. I am also seeing a bit of blobbing when the head is stationary during a retraction, so I'm hoping faster retraction will lower the amount of time spent stationary.

Anyone have any ideas?

[johnoly99]

msdevstep, from the sound of adjusting pots, i'll assume you have a RAMPS setup. Default FW has crazy stupid defaults for accel/jerk settings. Try taking your accel for the extruder down to 2500, and the jerk to 20, and remove the filament, and manually enter

G91 ;incremental mode
G1 E100.0 F3600 ;run extruder for 100mm at 60mm/s
G90 ;back to absolute mode

[msdevstep]

johnoly99,

Thanks for getting back with me. I've been able to try what you suggested. I lowered the accel down to 2500, and jerk was already set at 20. I removed the filament and ran the commands. I'm still getting the "stalling". I'm now going to try and lower accel a bit more.

Thanks

[msdevstep]

Ok, so I lowered the accel down to 2000, and about one out of 10 runs would still get a little stall. So I dropped it to 1900 and the stalling has gone away. I'm going to feed the filament back in now and see if the problem is gone.

Thanks again!!!

[msdevstep]

So I'm all the way down to 800 and still getting stalling (but it's a lot better). Jerk is still at 20. Anymore ideas? Should I keep going lower? If I go lower, is the extrude even getting to 60mm/s during an 8mm retract?

[msdevstep]

So I'm all the way down to 400, with a jerk of 20. I've lowered the retract speed to 42mm/s and still am getting fairly consistent stalling. I really don't know what else to try. I'm essentially back where I started as far as retract speed goes. Do you have anymore ideas at all?

[msdevstep]

I can run this over and over again and not have a single stall:

G91 ;incremental mode
G1 E10.0 F3600 ;run extruder for 10mm at 60mm/s
G1 E-10.0 F3600 ;reverse extruder for 10mm at 60mm/s
G1 E10.0 F3600 ;run extruder for 10mm at 60mm/s
G90 ;back to absolute mode

It just stalls like crazy when printing. I'm still at 400 accel, 20 jerk.

[VerticalSpeed]

Hi there,

I have exactly the same problem, but it's stalling at 30mm/s. I changed the bearings cause one of them was not good looking.
I tried to adjust the current setting (on a RAMBO 1.1b) to 220. It's a little better but still stalling at very slow speeds.

I'll try to change the acceleration settings but it seems that this extruder is having much problems.

[mhackney]

Acceleration setting can have a profound impact with this or any extruder or stepper motor for that matter. Reduce it by half, test, reduce by half test until you find a good spot, then start inching your way up to find the best acceleration.