Clogged Extruder?

I just finished my kit and loaded some PLA into a 185C hot end. Temp goes from 185-187C. Plastic just slowly flows from the end as the extruder motor tries valiantly to push it thru as the hobbed bolt slips on the filiment. If I tighten the idler bearing screws down almost the way, the motor stalls and skips steps. The PLA measures about 2.87-2.89 and feeds smoothly along the tube to the extruder. I've tried 3 different spools of PLA all with the same results. Now once during a few cycles of extrude/reverse I did get it to flow nicely, but it was short lived. It's a .35mm nozzle.

Sounds like it might be clogged, but not sure how to clean it out. I've got the hot end off now. I cut the wires so I can reinstall with a terminal block for next time I have to mess with it. I plan on heating it up off the machine and feeding the PLA by hand to dislodge any debris. Any suggestions would be appreciated...I just wanna print something!

Thanks,

Dave

It has been a while since I had a clog but the first step I would take is to heat up the hotend (I do it on the machine with the bowden tube off) and then push some filament in and through it very quickly and then pull out the filament before it melts any more than has gone through the hotend. Then remove the melted end of the filament (which may look dirty) and do it again. I would repeat this a few times and the filament will start to come out clean.

If the filament coming out of the nozzle hole is curling then you know you have something in the very tip. To get it out you would need a very small wire or drill bit (0.3mm) to clean it out.

The next thing to try if the first one did not work and the second is not the problem is to remove the hollow set screw in the top of the J-head and slide out the liner and see if it has been overheated or over-tightened squishing the end of the liner closed a little. If the liner is damaged for some reason (doubtful as they come assembled by the creator of them, Brian at hotends.com) you can use some of the extra bowden tube to replace it.

One last thing to check is to make sure the ends of the bowden tube where the nuts are threaded on are not too small for the filament after it has gone through the hobbed bolt.

---

FFF Settings Calculator	Gcode post processors	Geometric Object Deposition Tool Blog
Tantillus.org	Mini Printable Lathe	How NOT to install a Pololu driver

185C isn't hot enough for some types of PLA. 200-220C is often needed if the temperature is being reported accurately.

---

[www.hydraraptor.blogspot.com]

I got a .3mm bit and cleaned out the tip. When feeding it be hand I can get a nice noodle of filiment, but if I push too hard it starts to curl around the tip. I've went to several cycles of clean, push filiment, clean and it's flowing better but still curls if pushed hard. I'll install back on the machine and if I have a problem, I'll video what I'm seeing.

nophead
I'll up the temp a bit.

Dave

Ursine Wrote:
-------------------------------------------------------
> I got a .3mm bit and cleaned out the tip. When
> feeding it be hand I can get a nice noodle of
> filiment, but if I push too hard it starts to curl
> around the tip. I've went to several cycles of
> clean, push filiment, clean and it's flowing
> better but still curls if pushed hard. I'll
> install back on the machine and if I have a
> problem, I'll video what I'm seeing.
>
> nophead
> I'll up the temp a bit.
>
> Dave

Curling is usually a sign of a small burr in the hole or dirt. But I could see it curling if you have pushed all the molten plastic out and you are almost cold extruding and the plastic is under enough pressure that it expands and curls as it comes out. I would try as Nophead said and up the temp at this point.

---

FFF Settings Calculator	Gcode post processors	Geometric Object Deposition Tool Blog
Tantillus.org	Mini Printable Lathe	How NOT to install a Pololu driver

I made a video of the hotend. You can hear the missing steps. I believe the motor has enough torque but maybe I need to increase current? Strange that sometimes it flows just fine. I increased the temp to about 200c.

[youtu.be]

Dave

Edited 2 time(s). Last edit at 02/14/2013 11:17AM by Ursine.

That test looks good and yes it is skipping steps. But you are also using the purge button via the LCD which empties the melt chamber pretty fast. When you print the extruder never turns that fast except during retractions so it should not be a problem, I would try and print. If you find it skips steps during printing then I would try and increase the current and/or temperature. Just be careful you do not turn up the current so high it overheats or overheats the extruder motor.

---

FFF Settings Calculator	Gcode post processors	Geometric Object Deposition Tool Blog
Tantillus.org	Mini Printable Lathe	How NOT to install a Pololu driver

For the video I was using the extrude button in Pronterface, but still probably faster than a printing feed. I increased the current til it went into it's overload fit and then backed it off a bit. Still skips a step every once in awhile but much better.
I started the calibration process by printing out the 20x20x10 cube. First layer looked nice until the nozzle started dragging thru the print. Still have to finish the cal but it might be trying to extrude too much. That would also explain the odd missed step. Z-steps seem correct...the finished cube is 10mm exactly.

Yup looks like over extrusion. I would reduce the steps per mm by 20 and try again. Once you can print a solid cube without this issue you will be set to print. Also you may be able to lower the temperature a little now that you are printing and the flow is lower. The slightly blobby corner could be from the temperature being higher than needed which results in ooze but could simply be because of the over extrusion too. You may also find the need to re-tension the cables after a few test prints as the slack comes out of the cables.

---

FFF Settings Calculator	Gcode post processors	Geometric Object Deposition Tool Blog
Tantillus.org	Mini Printable Lathe	How NOT to install a Pololu driver

I've been fighting extruder problems for awhile now and I think I have it solved. The upper nut on the hobbed bolt (the one that fits into the gear) would eventually tighten itself against the bearing and cause the motor to skip. Even with Locktite it would ride up on the lower bearing and almost seize the bolt. I tightened the nut where it held it snug but still allowed the bolt to rotate smoothly and installed a set screw (also filed a flat on the threads). Initial tests look good. I had to install a washer to allow the bottom of the gear to clear the housing.

Looks good.

---

FFF Settings Calculator	Gcode post processors	Geometric Object Deposition Tool Blog
Tantillus.org	Mini Printable Lathe	How NOT to install a Pololu driver