Extruder nozzle cleaning / messing up / drops of material

I've been checking the nozzle (basically 'unscrewed' itself under the high pressure of the filament), and discovered there was quite some sneaky material lurking inside...

[lh3.googleusercontent.com]

Is it possible to clean the nozzle, or at this point is beyond recovery?

Some material also tended to stuck in the heater block nut when extruding (don't know why, but when pushing material down it kept going 'up' following the shape of the nozzle for a while, then began to fall down leaving material all around the nozzle), so when i had to unmount it I also broke few parts... and will have to buy a new thermistor... so this means I'll have few days off for this thing until i get new stuff.

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I also found that even changing the configuration parameters (the STEPS_PER_MM for the filament injection) there was a certain behavior that repeated no matter what i put on that constant.
That behavior is leaving a 'drop' of material when starting a new layer, or actually, a new line, before the extruder starts to move. On higher numbers this means creating drops of PLA around the object, of which, sometimes, the nozzle 'bumps' into...
[lh3.googleusercontent.com]
[lh5.googleusercontent.com]
[lh4.googleusercontent.com]

I also faced this problems quite a few times:
[lh4.googleusercontent.com]
I think it might be related to a too high STEMS_PER_MM of the extruder, I wonder?
If I'm not wrong though, it seemed to happen even with the default value (gen6 electronics firmware, it was something like 20), which ended to be way too small even for making clean lines when testing plotting.

So basically I'm wondering: when the new layer is attempting to be layed down, the extruder 'rolls back' a bit, to suck up some material for not leaving dirty parts around the place, and then rolls back in to reset the position. But when it rolls in it goes way too much and:
- makes that bubbles of material
- messes up the filament up there

That's what I've guessed till now though.
This happened with both setting the steps to 20.2 (original value) than 45.14 (my calculated one for 1.75->0.35)

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I'm wondering what people think of this outcome.

Edited 1 time(s). Last edit at 07/11/2011 03:24AM by raffaele.ragni.

You can clean the nozzle using a blow torch: [www.youtube.com].

Other people like Nophead use a drill bit held with a hand to clean the nozzle.

Your tip temperature is too hot. This is probably how your tip clogged and it's also the reason for the blobs. It looks like heat is traveling up the filament and making it soft near the hobbed drive. If turning the temperature down doesn't fix this, you might need to improve your thermal isolation between the tip and the cold end, provide heatskink, active cooling or both. The steps per mm is not the parameter to adjust to solve the blobs. You can calculate that or look it up based on your extruder design and your gcode software. Skeinforge 40 and later is based on mm of feed while earlier versions and other sw is based on mm of extruded filament.

Is that a Wade's geared extruder? Did you resize the hole for use with the 1.75 mm filament?

Edited 2 time(s). Last edit at 07/07/2011 06:39AM by brnrd.

brnrd Wrote:
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> Is that a Wade's geared extruder? Did you resize
> the hole for use with the 1.75 mm filament?

Yes it's a Wade's.
No I didn't do any resizing, didn't knew about that.
Besides the filament seemed to go smoothly in the beginning, so I never wondered about that solution.

How can that be done in a proper way? Closing the hole with something and then drilling?
In both up and down holes?

You might be able to insert a PTFE tube of the right size all the way to the tip. I haven't done this so I don't know if this will work. It might be easier to buy 3 mm feed instead.

The main advantage of 1.75 is is allows you to use a smaller lighter extruder because you need less force, so you can use less gearing, and / or a smaller motor.

I can't see any point in using 1.75mm filament in a Wade's extruder designed for 3mm. To make it work you would need to make a smaller heater barrel to prevent back flow (which may be the reason it jammed) and the filament guide path needs to be smaller to stop the filament buckling. A PTFE liner may work, but plastic tends to flow back up the outside of the liner causing it to constrict and jam.

To take advantage the whole design needs shrinking: smaller hotend, motor, gears and bearings as Jean-Marc has done for his eMaker Huxely, although that is a Bowden version.

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[www.hydraraptor.blogspot.com]

OK, I'll see and try with a 3mm config then, as long as i can get my hands on one.
I guess I made something wrong from the beginning.

(I got the plastic parts in the start, and completed the kit by 'hand' not really knowing much about it - didn't even knew the extruder I had wasn't the default - of course if I did start with a complete kit all this mess wouldn't came up)