Extruder skipping in a pattern

OK, yet another problem.

somehow during my last print my filament was bent out of the extruder and ravelled itself around into a knot.
Once I cut the filament out the extruder started randomly skipping steps, at first I thought it would be due to a clogged nozzle so I took out the nozzle and replaced it with a new one while I cleaned out the blockage.
3 Nozzles later and the extruder is still skipping.
I have increased the stepper motor power and even changed the stepper motor on the board with no luck in getting rid of the skipping steps. Nothing in the software has changed.

As you can see in the pictures, the skipping seems to happen in a pattern and when it isn't skipping, there is no problem extruding the filament.

I have also provided a picture of what the finished product has come out like with the bad skips.

Is your hobbed bolt clean?
filament dust in the teeth might cause slipping = stops extruding until it rotates and starts pulling again.

EDIT: or bolt has damaged teeth?

Edited 2 time(s). Last edit at 12/07/2016 03:15PM by Veesta.

The teeth are fine, i've had it in peices and back together, same problem.
I've now turned down the voltage of the driver to where it should be and put my desktop fan over the board to make sure the driver isn't overheating, i'm still getting the same problem.

Whats the filament like?
Could be one side of the filament role is poor for some reason.
Is the extruder idler wheel/bearing damaged/sticking/has a lump of filament stuck to it.
What is the route the filament takes to the extruder. I have my filament drum under my printer and feeding up the back. I had to make a guide to keep it away from the bed to avoid the bed bending the filament - bent filament causes problems at the extruder.
Are you using a Bowden system?
Are you sure the extruder motor is rotating during these events? If it is a blockage I would have expected grinding and the feed wouldn't resume but these things are often not intuitive.

I have tried 3 different filaments, all different colors to make sure,
The idler and teeth are fine, I've had it all to bits and back together.
I have my filament stored above my printer which then goes straight through a hole in the top of my enclosure and then into the extruder, no bending.
I am using an MK8 extruder.
The motor is definitely rotating, its just skipping steps.

Last night I managed to print 1 item off with very few skips, but then the next print the filament ended up pushing back out of the extruder and tangling up again.

I have ordered some brand new nozzles, a new heat block and a new teflon lined nozzle throat.
My latest theory is that at some point in the past few days part of the teflon tube from the throat has become dislodged and is blocking the filament from being extruded.
Just a theory though.

Any other ideas will be very well received.

If the filament is coming back out of the extruder it seems to me that there is too much retraction going on somewhere.

it isn't "coming back" out of the extruder, the filament is trying to be pushed through the extruder but its obviously not going and it eventually bends between the gear and the throat, it is then extruded normally but with the bend gets sent outside the extruder.
Which is the reason I am thinking something is wrong with the throat as it is not fixed by replacing the nozzle or the filament.

What temperature are you useing to print

The teflon liner is a close fit in the throat tube and anyway, if you have the throat tube the correct way up, the entry hole is only marginally larger than the filament and it should not be possible to displace the liner. The large end of the throat tube should be towards the bottom. If you have used too high an extruder temperature it is just possible that you have melted the liner, but that should be obvious on dismantling the hot end.

Are you sure that you have got the filament into the extruder properly? It is not enough that it is simply gripped by the drive. You have to make sure that the filament has entered the small hole at the top of the throat tube and passed down to the heater, which is about another 20mm. If the hot end is at the correct temperature for the filament that you are trying to print, then I can't think of any other reason why the filament will not extrude, or why the stepper should miss steps. Don't forget that PLA+ requires a higher temperature than ordinary PLA, or it will not be able to extrude.

It seems to me that there is something wrong with the physical set-up of your hot end. The throat tube should be screwed far enough up into the extruder drive that there is only a small gap between the drive and the tube. It should not be possible to cause the filament to bow out and get sent outside the extruder. This is the whole reason why direct drive extruders are so good for printing flexible filaments. There is only about a 1/4" gap on mine between the lock nut and the heater block, and the throat tube entry is only just clear of the extruder gear.

Edited 2 time(s). Last edit at 12/08/2016 07:37PM by Supermec.

Quote
muntahunta
it isn't "coming back" out of the extruder, the filament is trying to be pushed through the extruder but its obviously not going and it eventually bends between the gear and the throat, it is then extruded normally but with the bend gets sent outside the extruder.
Which is the reason I am thinking something is wrong with the throat as it is not fixed by replacing the nozzle or the filament.

My mind says extruder steps calibration.
Are you extruding too much that it curls in the feeder?


Is there a setting in the slicer to multiply the extrusion to something that the printer cannot handle?

Is the extruder steps calibrated to exact?

My extruder steps are calibrated, i've tested this over and over.
the physical setup is the same one I have now used for well over a year and prior to this was extruding fine.
I print at 220-230 depending on the make of filament, Currently using PLA.

I am going to wait for the new nozles and throats to arrive and build my setup over again and I will report back.

Did you try to manually feed the hotend? How hard do you have to push?
What about your controller? If it's a RAMPS it could be a faulty microstep jumper.

I had a similar problem with a MK8 extruder, I even bought a full metal one and kept having the problem.
I was using A4988 drivers and replaced the extruder one with a DRV8825, which can handle more current.
That solved the step skipping for me, but still had filament that curled up in the extruder.

I drilled out the push fitting so that the teflon tube can enter the extruder, and then cut the tube in the form of the hobbed bolt and idler wheel so that the filament has no other way to go then in the tube.

That worked out for me

see attached file

220-230 seems high for PLA. I am no expert as I mainly use ABS. I have read on here that too high a temperature can cause the pla to melt and flow back up the hot end where it cools-solidifies and jams the hot end. I have seen on here temperatures for PLA quoted at around 185 - 190.
Another possibility is that the idler pressure on the extruder gear is too high. Normally I would have expected grinding when the hot end jams but you seem to still be feeding. If the pressure is too high so it maintains drive then you may get skipping instead. However the load forces the gear teeth into the filament. This distortion (big teeth marks sticking OUT of the filament) could cause jams in the hot end.
It also implies you have a significant (big) gap between the end of the hot end threaded tube and the drive gear. Can you adjust this closer? But it needs to align with the drive gear as well or you will get high resistance trying to bend it into the tube.

I'm currently printing eSun PLA+ @ 175°C

This roll says printing temperature should be around 205-225°C, but those are way too much.
I think those temperatures are needed only if you print really fast and really high layers.
20-80mm/s and 0.2 layers seems to be happy at 175°C

Hey, muntahunta. How are you man? Are your problem solved?

I am thinking that I have the same problem and like the o_lampe said, I tried to push manually the filament, and it´s to hard, like something blocking the nozzle.

Because I changed the nozzle, the breakthroat (with and withou PFTE) and the filament, but the problem persisted, I am considering that the clone e3d v6 is the problem (I want to buy the e3d v6 lite original, but thet dont ship to Brasil).

To understand how much is this clogging, I can only extrude at 3mm/s, more than that, the extruder skip back.

Setup:
Bowden 1.75mm
Hot end e3d v6 clone
Nozzle 0.4mm
Extruder MK8

Many times the extruder skipping is because of a hot end jam. I’m having a problem with my E3Dv6 right now caused by heat creep. The heat from the heat zone creeps up the hotend causing the filament not in the hot zone to soften. Then the extruder cannot push the filament throught because it’s too soft causing it to jame. Keepting the fan blowing is key, and you can see if this is a prbblem by touching the fins on the hotend. If they are fairly warm, chances are this is your issue. There could also be a problem where all the pieces join, but I’m not familiar with e3d clones.

But your prints are actually printing, so that may not be the issue. If the mk8 gear in the extruder is too loose, it can skip too. If it’s too tight, that’s not good because it flattens out the filament. You can mess around with the tightness and get it as tight as it can wihtout flattening the filament.

Good luck.

This could be temperature cycling at the hot end. Check the temperature trace although this doesn't always show the issue. Try printing hotter to see if the spacing changes.
As stated in other posts we have had reports of the driver failing and causing similar issues.