Extruder is "popping" backwards.

[jeffhuber]

So this happens often when I'm printing. It makes a loud popping noise (which can you see in the video) which is rather disconcerting, but it doesn't seem to harm the overall print integrity. Do your extruders do this? I know retraction can be used for when the hot is moving, but in this print the hot end never "travels" (joris type spiral vase design).

https://www.dropbox.com/s/ogl0xkr34mkvf ... 6%20PM.mov

Would love to hear what your experience and any tips you might have.

thanks!

[Eaglezsoar]

So this happens often when I'm printing. It makes a loud popping noise (which can you see in the video) which is rather disconcerting, but it doesn't seem to harm the overall print integrity. Do your extruders do this? I know retraction can be used for when the hot is moving, but in this print the hot end never "travels" (joris type spiral vase design).

https://www.dropbox.com/s/ogl0xkr34mkvf ... 6%20PM.mov

Would love to hear what your experience and any tips you might have.

thanks!

There are two things that I can think of that can cause this, one is what you mentioned which is retraction, the other is the step motor drivers have built in circuitry that will cause to stepper to momentarily shut off because the step
motor driver is too hot. Ensure that the fan at the rear of the Rambo is running at all times the printer is powered if it is, try printing with the LCD door open and a small fan blowing on the front of the Rambo.
If the fan blowing on the front of the Rambo stops the problem then you need to figure out how to mount a small fan on the LCD door pointing at the front of the Rambo. Some have had success adding heatsinks to the driver chips but
active cooling with a fan seems to work the best. If you are wondering why the extruder stepper would move backwards if it looses power momentarily remember that the filament is under tension by being pushed by the stepper and if
the stepper looses power that tension is immediately releases pushing the stepper backwards. Let us know the results of your work. Another thing that can be tried would be to reduce the amount of current being received by the extruder stepper motor by editing the configuration.h file and reloading the firmware. The reduced current may prevent the driver circuitry from becoming hot enough to trip the auto-cool down.

[geneb]

It can also happen if the hot end is too cool for the speed at which you're printing.

g.

[Hansen]

I am quite sure this is the extruder motor skipping a step. The exact same thing happens to me, when I try to push too much material through the nozzle (flow rate > 10 mm3/s approx.).

You could try one or more of the following:

1. Increase temperature
2. Decrease speed
3. Decrease layer height.

[jeffhuber]

Thank you all. This is really useful - I will be trying all of these things and will report back!

Jeff