Extruder/Nozzle Clogging Problem

Hi,

I have problem with my extruder. I can extrude filament before printing, but when I start to print and nozzle touches a little the bed, extrusion stops or extruder is clogged.

Then, I can retract the filament uneventfully and extrude again the same filament, no problem. Additionally, sometimes drive gear crushes the filament because of clogging of the nozzle, so I retract it and cut it.

My extruder and filament after clogging:

I suggest that your nozzle is too close to the bed, creating back-pressure.

If you "print" with the nozzle (say) 10mm above the bed, does it extrude properly?

If I print 10mm above the bed, there is no problem. I tried it.

I had problems with retraction, a blob of molten PLA get pushed back and get clogged in the cooling part of the extruder because it get hard.

I've also had a similar problem where the pinch idler on the extruder was too tight. It wasn't deforming the filament, but cutting grooves into it big enough to catch on the edge of where it enters the hot end. Uusually a retraction would bring it up and back down and then it would catch. I ended up taking the hot end up to temp and decreasing the pinch idler until it was just barely touching. Then tighten it a little, feed some filament by hand. No catches. Tighten a little more, then feed by hand until i felt it catch, then backed it off.

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cagtag
If I print 10mm above the bed, there is no problem. I tried it.

OK, so the problem isn't in the extruder or hot-end.

What kind of printer do you have? How are you setting the nozzle height? Are you using auto-leveling?

How flat is your bed? ("Level" refers to the plane of the bed... it should be in the same plane as the nozzle moves. "Flat" refers to variations in the height of the bed surface above/below the plane).

Quote
frankvdh

Quote
cagtag
If I print 10mm above the bed, there is no problem. I tried it.

OK, so the problem isn't in the extruder or hot-end.

What kind of printer do you have? How are you setting the nozzle height? Are you using auto-leveling?

How flat is your bed? ("Level" refers to the plane of the bed... it should be in the same plane as the nozzle moves. "Flat" refers to variations in the height of the bed surface above/below the plane).

I designed my own printer and I also designed my extruder system. I set the nozzle height with a paper in 3 points and Z limit switch. I tried the auto-leveling.

I used the BuildTak on glass.

Additionally, If I tampon the nozzle with spatula, extruder can't extrude the filament and I must retract the filament because of pinch idler more crushing the filament.

There is always a trade-off on the first layer between sticking filament to the bed and extruding. If your nozzle is too high, it won't stick. If it is too low, it won't extrude.

I'd try setting the initial height a bit higher, to maybe 1mm or so... then gradually wind it down by hand until filament sticks to the bed. Hopefully you will find a sweet spot between "too high to stick" and "so low the hotend jams".

If you still get jams, you could try several things:
1. Increase nozzle temperature... I print the first layer at 200 and subsequent layers at 190
2. Reduce printing speed
3. Larger nozzle
4. Increase the power of your extruder and tension on your extruder spring (but it sounds like you are close to the limit on this already)