Extruder motor skipping/slipping

I'm finally getting close on having a fully functional printer. I can print objects now, but am not getting optimal results.

When printing infill or extruding large amount in air (>10mm), the extruder makes a clunking noise and stops extruding for a small amount of time. This is obvious in the infill as there are a lot of broken lines of filament.

I have tried just about everything I can think of, tuning the pot on the pololu anywhere from where the motor won't extrude to the point where it gets uncomfortable to touch with heatsink and fan. I have tried adjusting the tension on the idler, from really tight to really loose, to no effect. I have tried changing the temperature up and down.

The only thing that seemed to work when extruding 30mm in air was turning the speed down to 30mm/s in repetier, so I changed the max feedrate in the firmware to 30, but I still get the issue while printing.

Some specs:
Prusa Mendel
Mix G1 Extruder
RAMPS 1.4
1.75mm PLA
0.3mm Nozzle
0.4mm layer height
55°C heated bed with glass and blue tape (80°C first layer)

Any insight or tips would be greatly appreciated!

Quote

the extruder makes a clunking noise and stops extruding for a small amount of time

Sounds like your Pololu is overheating.

Quote

I have tried just about everything I can think of

Adjusting a printer isn't gambling. Changing one parameter at a time and looking at the results should give a much better idea of what's happening. If you think your extruder is stopping at times, for example, you'd see the motor actually stopping. If you can't see the motor shaft turning, put a marker on it.

---

Generation 7 Electronics	Teacup Firmware	RepRap DIY

I have had a similiar issue, I found that my extruder gear was slipping on the motor shaft. It would click and release pressure on the hobbed bolt drive gear, almost looks like its reversing when it would click.

I had a computer fan on my electronics RAMPS 1.4 and did not know if I even needed it in the basement in the winter ~60F room temp, then I disconnected it, and got the x axis making a clunking noise and skipping. The motors weren't even really hot to the touch- only warm at the level they were trimmed to. I put the fan back on the electronics and the skipping went away.
Do you have a fan on your stepper drivers?

I don't know what happens when the driver overheats, so I'm not gonna go into that, but some general thoughts:

I can think of two things happening here, that I've seen myself:

Motor is not strong enough, because of too low drive current or too high work load. It will then make a nasty low frequncy "brrruuuup" noise.
OR it's entered crazymode. I do not know what causes this, but I sometimes see it on my Z-axis motors for some reason. It looks like they don't know where to go basically, spinning in random directions at random intervals.

Your nozzle might be jammed, requiring huge pressure to extrude. This could make any motor wince. Try to see if you need to clean out the nozzle.

You might be using too low temperature in your nozzle. I basically cannot use any less than 200 degrees, and I usually print at 220-230 to get good flow at higher speeds(50 mm/s and up).

Maybe something else is causing too much friction in you filament feed?

Also, You don't really mention if the problem goes away when you turn up the potentiometers for the current drive to the motor. It's OK, really, if the motors are hot. They are designed for that sort of use. Below 100 degrees C(your finger will hiss if you touch them after wetting your finger) is probably fine.

Quote

I don't know what happens when the driver overheats

When overheating, the driver drops the current for about half a second. Some recognize this as a "clunking" sound, as the motor stops turning then.

With current a lot over maximum current, the next overheat can be only half a second away, too, so you get something like stuttering.

---

Generation 7 Electronics	Teacup Firmware	RepRap DIY

I also experience clicking sound of extruder motor on my Folger Prusa i3, but I was able to figure out that it generally happens because of following reasons:
- if something block extruding, so extruder can't extrude filament. In my case it happens sometimes when Z level is not correctly adjusted and the extruder comes too closer to printing surface when printing very first layer
- if it's too high printing speed. Over 120 mm/s. The reason I guess the same - extruder can't melt and extrude given amount per given time.
- extruder temperature is too low. Again, extruder can't melt filament fast enough.

Hope it helps.