under-exrusion

[hugues]

Hello.
My prusa I3a worked fine for a few week, but not any longer...
The extrusion seems to stop and start again not regularly...
I don't know what to do, I've put a new nozzle but the problem is the same.
Here is a picture of a first layer, it is supposed to be full...

HELP!!!!!

[midiman310]

Yikes!

1) Check to make sure driver board vref is at least 0.8volts.
2) In Repetier-Host Heat your nozzle and to your extrusion temperature.
3) Mark off 100mm on your filament going into your extruder mouth.
4) Go to the Print Panel and extrude 100mm of filament. Insure the filament flow freely and consistently out the nozzle.
5) Once extrusion has stopped, check your filament entering the extruder and see if you indeed have extracted 100mm of filament.

If you didn't, then you may have old filament stuck in the Teflon tube which is hindering or dragging the flow or maybe the pinch groove roller doesn't have enough tension on the filament. I found that sometimes after I retract to change filament, the pinch doesn't return to the original spot. Usually the spring inside the extruder is supposed to keep tension on that pinch roller.

As you're heating the nozzle check the "temperature curve" in Repetier host to make sure it's reasonably stable even when you're extruding.

Hope this helps.

[hugues]

Thanks for the help.

So, I started to check that and I think that I've found that my problem is....

...overheating of the motor driver!

The original A4988 was dead after my first test prints, I replaced it by a DRV8825.
And I don't know why, after several flawless prints , It overheats.

I tune it a little down, tried to improve air flow and TADAAA! It works again!

My next print failed because the nozzle stops heating in the middle of the print... A new problem to fix.

[zhangxueyou]

Thanks for the help.

So, I started to check that and I think that I've found that my problem is....

...overheating of the motor driver!

The original A4988 was dead after my first test prints, I replaced it by a DRV8825.
And I don't know why, after several flawless prints , It overheats.

I tune it a little down, tried to improve air flow and TADAAA! It works again!

My next print failed because the nozzle stops heating in the middle of the print... A new problem to fix.

Do you print on computer? If so, maybe it's because of bad communication, you can try to print off-line by SD card.

[hugues]

Do you print on computer? If so, maybe it's because of bad communication, you can try to print off-line by SD card.

Exactly!
I have followed your advice and printed several parts with SD card flawlessly. Now, I'm printing back on computer and the problem didn't reappear yet. But I monitor it closely.
Thanks.