Extruder nozzle blocked

I have been struggling for three days and would really like some help on this. My printer printed fine with some minor artifacts but not real problems for several days since I finished building it. I printed about 15 to 20 test pieces and parts. Four days ago it just stopped in the middle of a print. The motor was running and no slippage of the gears. I used the forum and google and read as much as I can about possible problems.

I first suspected the filament feeder and opened if, cleaned it up and made sure everything looked OK. Could not really see much wrong. A little bit of play in the one bearing case which I fixed by placing a piece of tape on the inside. Did the next print with an old file that I knew worked but the same happened. Switched off and on again, fed the filament manually and everything looked OK (the only possible problem was that the PLA curled a bit but more about that later).

Tested the feeder by holding the filament between my two fingers. I could not hold it even if I tried so decided that the feeder is probably OK. Is that a reasonable assumption?

The filament is PLA from RS and I assume that it is good quality? I measured the thickness and it varied mostly between 0.70 and 0.72, worst case 0.69 and 0.74.

Next tackled the hot end. The filament moved freely through the Bowden tube so no problem there. Opens the hot end, unplugged it with a piece of PLA as described in the trouble shooting guide to remove any possible loose pieces and tried again. Worked for one smallish print for about 40 minutes and stopped again. Opened the hot end again, cleaned it and replaced the PTFE tube inside. Next print worked fine but stalled again on the second print. Next heated up the nozzle and use a 0.5mm drill bit to clean it up. After this the PLA came out of the nozzle without any curling so I am not sure if there was something dirt/buildup on the in side of the nozzle or not. Also cleaned the nozzle from the back again as before.

I should also mention that in all the cases that I have tried I could manually fed the filament and it worked fine after all the stoppages without me having to clean it at all. I also tried different temperature setting from 190 to 215 C. I monitored the temperature during the stall to make sure that there is not a bad contact on the heater but the temperature stayed constant.

Several different objects were printed at different speeds and layer thickness to make sure that he feed rates were different. Small objects I can sometimes finish but at random times the filament stopped feeding. I did get the feeling that with a higher feed rate, e.g. while filling, it jammed quicker but that might not be an objective observation because I tried it with very slow feeds and it also jammed.

Otto, see my suggestions in the other thread you started about Ormerod issues in general (although now that I have read this one, I can see that some of them are not applicable).

If you find that you can always feed the filament manually even when the extruder can't feed it, then perhaps the extruder motor is not quite providing enough torque. You can increase the extruder drive current by editing the M906 command in config.g. Try 1000mA instead of 800. But I haven't needed to do that (although I have increased the current for the y-axis motor).

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Thanks for the interest dc

I do not think that the torque is the problem because the motor and gears still turns, even if the filament stopped. Obviously the teeth on the feeder 'eats' out a small piece of the filament and it can cannot get grip again on the filament again without some help. Normally I stop it, wait a while, heat up the nozzle and feed it by hand past the gap. I cleaned up the nobbed gear a couple of times but it did not really make a difference. What I would like to know is how strong should the pull be? Is it enough that if I can not hold it back between my thumb and forefinger?

You have a Ghost....hahahahahaha That eats filament....


Does the filament stop? It must do when it happends. If so, then either the Hobbed nut is not central, or your nozzle is blocked by PTFE.
Sardi had similar, and it was the PTFE tube in the Nozzle that was causing the problem.

The feeder rear bearing should be level with the back of the feeder.
If you look at the filament after it's been through the filament then the grooves in it should go down equal both sides of the filament if it's central.
Have you tried heating the HotEnd with filament in, then when it cools to about 150' or less retracting it to drag the rubbish out?

Kim

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Please send me a PM if you have suggestions, or problems with Big Blue 360.
I won't see comments in threads, as I move around to much.
Working Link to Big Blue 360 Complete

Quote
OttoES
...What I would like to know is how strong should the pull be? Is it enough that if I can not hold it back between my thumb and forefinger?

Hi Otto

You could heat up the hot end, dismount the bowden cable from the extruder and push the filament trough with you fingers, then run some filament through the extruder against you fingers and compare the forces

Erik

You appear to have covered all the bases to try to find the fault. Make sure that your cool block (bolted to the heatsink) is not overheating (it should remain cool enough to be able to hold your finger against at all times). When the feed stops, if you find that pushing the filament by hand momentarily (without stopping the print) starts it feeding again, then the problem is not likely to be a blockage, but rather an issue in your extruder or Bowden tube. Kim's suggestion is sound - if the hobbed part is not gripping the filament centrally, it can occasionally tear out a chunk and stop feeding. Ensure you have washers in all the right places in the extruder (see build instructions). When I replaced my extruder block some months ago, a washer fell out without me noticing, and I got similar symptoms as you describe even though it worked OK at first. Also examine your Bowden tube for any sign that it has been crushed or kinked, and perhaps drill out the inside of the tube again at the threaded sections at each end, just in case there remains any pinching at those points - being careful not to leave PTFE shavings in the tube.

Some blockages can be difficult to clear, and a small PTFE shaving can remain in the nozzle even after repeated cleaning, intermittently blocking the nozzle. You could try burning out any debris by holding the nozzle in a gas flame, then washing out the ash and pricking the hole with a strand of wire. Using a 0.5mm drill bit to clear the nozzle is not advisable because it is likely to change the shape and roughen the sides of the hole. Alternatively (and probably better) soak & occasionally shake the nozzle inside a sealed jar of PLA solvent for an hour or two (you can get PLA solvent here: [www.amazon.com] ) which should dissolve all the PLA so any debris can be easily cleared out.

Dave
(#106)

Thanks for all the suggestions guys, it is really great to have such a forum!

I wanted to try all your suggestions tonight but I am afraid my Arduino board is dying. It is not dead yet but it is on its way out. Tonight when I switched it on I had trouble connecting through the USB. I opened the Device manager under windows and could at first not see the COM port. After a reset I did not see it immediately but it did appear after the ATX power supply was switched on as well. I could connect but every thing was a bit erratic and not really predictable. Temperatures were out, first to low around 0 and later the head went up to 200 and back again. Furthermore the Adruino kept on sending temperatures although I did not request the temperature. I did a reset and the same happened. I could still send commands to the steppers and they reacted at first but the head heater did not react at all. When I felt the enclosure it felt warm. I switched everything off immediately and opened the box. The processor and 5V SMPS regulator (I think it is) both still felt hot (about 40-50C) I kept it open and switched everything on again. The processor heated up to about 60C withing 20 seconds (very hot to a finger touch) so I switched it all off again.

Will have to think about what next.