clucking extruder - air printing

[Greg von Plettenberg]

I have been using my new Rostock max v2 for a few weeks with no extrusion problems. lately the first few layers have been very thin (like my z0 is too high) and yesterday it just stopped extruding with the extruder clucking like it does when you press the manual extrude button before it gets up to full temp. It heats up nicely to 225 C with the temp curve showing a well tuned PID setup, but when you manually extrude it only extrudes about 1/3 of the usual amount. If i try print it just prints air after the extruder has stripped the filament and just slips. ( the plastic gear still turns but the filament doesnt feed). Is the nozzle perhaps blocked, and if so how do I clean it ? Any other suggestions ? my hotend is the one with the glue in thermistor and the two green heater resistors which I glued in with copper rtv

[Mac The Knife]

What material are you extruding?

[Greg von Plettenberg]

ABS at 225 C . I did print the beginning of a small part in PLA at 225 C by mistake about two weeks ago, and it jammed much like it is doing now, but once I removed the PLA it printed just fine in ABS again

[Mac The Knife]

I haven't tried PLA yet, but I wonder if a scrap of it was still in the nozzle, and came loose. I'd pull the nozzle, and soak it in acetone. and carefully run a wire through the tip.

[TFMike]

acetone wont remove the pla unfortunately, might be best to run a flame through the nozzle. Also check with a PID that your nozzle is actually heating to the temperature that your machine thinks it is and make sure the hobbed gear on the EZ struder is lined up dead center with the bearing on the red lever arm so it wont grind up the filament. Also, what is your print speed?

[Greg von Plettenberg]

I have been printing on the standard settings for abs that came with the setup instructions ie. 30 mm/s. I have cranked up the speed in the manual control window in Repetier to 150 , 200 and 300 percent which would be 90 mm/s max. In general i print at about 45 mm/s.

Also thanks for the PLA scrap hint, I will try flush or burn it out in the morning, its late at night here. The gear should be aligned as it has printed perfectly up till now, but Ill check it anyway

[TFMike]

You may want to slow your print speeds down until you get the clunky extruder resolved. This should help: http://forum.seemecnc.com/viewtopic.php?f=37&t=5231" onclick="window.open(this.href);return false;

and this: http://forum.seemecnc.com/viewtopic.php ... 797#p41797" onclick="window.open(this.href);return false;

How much dust is collecting on the ez struder gear, if any?

[dtgriscom]

Have you tried using Repetier-Host to feed the filament while the nozzle is at temperature but in mid-air? If that works, then the problem is your too-low Z0. Either way, it's a great way to clean out old material.

[Greg von Plettenberg]

Problem Solved, thanks for the advice
The printer is back to its former glory. The brass nozzle was blocked with overcooked ABS, so I unscrewed it and soaked it, and picked at it with a tiny screw driver, then repeated again and again until the overcooked ABS softened and could be extruded by hand by pushing in the back of the nozzle with a piece of filament.
REASON FOR FAILURE
The reason the ABS had become overcooked and hardened was that the thermistor had worked loose and was making a bid for freedom, but still registering a temperature somewhat lower than the actual nozzle temp. Luckily it did not melt the whole hot end.
SOLUTION TO THE PROBLEM
Inspired by the guy in the video with the handy 40 w heating resistor, brass screw in thermistor, and silione tape, which are unfortunatley currently in short supply down here on the southern tip of Africa, I put the thermistor back in its hole and then wedged a block of cured silicone rubber between the thermistor and the lug that crimps the wire legs from the heating resitors, and did the same at the other side opposite the thermistor. I then glued the whole set up with copper silicone. Since silicone bonds to silicone and the copper silicone is coating the resistor wires, I am fairly confident this solution will stand the test of time, as I am not relying on the adhesive properties of the silicone because it is restrained laterally by the resistor legs.
With hindsight I would have done this on initial assembly, and if you are reading this it may already be too late for your hot end, if not just add an extra large blob of copper silicone between the thermistor hole and the crimped lug and over the resitor legs to form a mechanial bond not reliant solely on silicones' poor adhesive qualities.