EZStruder bowden on custom Delta skipping

[oracledude]

I built a Griffin 3D delta and upgraded to an Azteeg X5, E3D V6 hotend, & an EZstruder bowden setup using a HobbGoblin 8mm drive gear. With any hot end (E3D, E3D volcano, JHead Mk IV) the filament does not feed for more than a few minutes with the EZstruder. If I remove the extruder from the equation, I can manually push filament through the bowden tube and nozzle(s) with no problem. The filament has bites in it, so it is apparent that the extruder is grabing it, but after a while it stops and the drive gear just grinds at the stationary filament. It even skips with a 1.0mm nozzle on a 260 degree Volcano hotend which is big enough/hot enough that the filament pretty much drips out of on its own with little resistance.

Any ideas?

[Tincho85]

Hello, What motor are you using for the extruder?
Is the current set ok?
Does it burn when you touch it?

[oracledude]

It's a Kysan NEMA 17 with a 5.18:1 gear ratio. It is warm, not hot to the touch. I have the current set to 1.2A in my smoothieware config.txt

[mhackney]

Did you calibrate the extruder? If not, it might be trying to push more filament than commanded and that would cause this sort of problem. Also, how fast are you feeding? Too fast can also cause problems.

[teoman]

You have to inspect the skipping. Is it "biting" parts of the filament or is the motor skipping? Or are the teeth slipping on the filament.

Usually running it from a rambo some people have their stepper a little bit too hot which softens the filament. That does not appear to be your case.

Your spring could be a little loose. I would check that. So when it starts skipping manually apply some more pressure to the lever.


With your gears the motor should not have much force on it.

Or you could have a bad motor or connection to motor.

[oracledude]

The extruder's steps/mm was properly calibrated, down to under 50 microns of accuracy. The filament has teeth marks in it along the entire length. When it slips, it grinds down the filament. The motor is cool running and does not click or knock. I added a spacer in behind the spring to increase tension and both variations have the same problem. My latest attempt was using a 50mm/s print speed set in Cura.

[mhackney]

When it stalls, abort the print then press the red lever down to release the filament and try to push it by hand. Pull it out a bit and push back in and pay very close attention to see if you can feel where the filament is snagging.

I would also check the path between the drive gear and the push to fit fitting the Bowden connects to. You might have a molding flash or distortion or something.

[oracledude]

Just failed... the filament was ground down by almost 50% in one spot. Teeth marks past it in the tube. I was able to manually push the filament forward without any substantial pressure.

[mhackney]

Something is snagging the filament. I've experienced this situation - the teeth create raised ridges on the filament, these ridges can snag on something in the extrusion path. In my case, this was in the hot end - usually where the PTFE Bowden tube transitions to the PTC or metal inside the hot end. You have this problem with 3 different hot ends of significantly different internal geometry, so that leads me to think maybe you are getting a snag at the extruder side as I described above. The symptom you describe - filament snags, gets ground down by the drive cog, and then releasing the pressure on it, it pushes by hand easily - is very symptomatic of this sort of "micro snag".

One thing you might try if you've checked the path as I described above, is remove the Bowden from the hot end and start a print. No filament will be extruded since it will be coming out the open end of the Bowden. What happens when you do this?

[teoman]

So maybe your spring is too tight that it diggs too deed in to the filament?

[jason128]

Try no retract- e3d don't like much- this will prove if it's the problem.
I added a bolt on mine under the spring on the extruder to tighten it up, and it fixed it for me

[Glacian22]

You might also try lowering your retraction speed if it's high...I noticed that when I had fast retraction (100mm/s) and the printer hit a section with a lot of quick retracts in a row the filament sometimes got torn up. Slowing down to 35mm/s led to less damage to the filament and stopping it from occasionally grinding flats.

[mhackney]

There is NO PROBLEM with using retract with E3D hot ends. Don't spread false information please. Even with no retract, the micro snagging problem I described can take place. 100mm/s retract is way too high even for filaments like ABS. PLA requires a very slow retract (20mm/s) to keep from jamming. I've written extensively about it here and other places. PLA melt is thixotropic and fast retracts will cause it to "lock". The original poster does not say what filament they are using, I missed that last night. What filament/s are you experiencing this problem with. What you are observing is also a classic problem with too fast retract with PLA. Large retracts make it worse. With an E3D V6 you can use .5mm or so for retract length and 20mm/s for retract speed and should have no problems.

If the gear is grinding the filament, spring tension is not the issue.

[IMBoring25]

I didn't see anyone say you can't use retraction. I saw eliminating it suggested as a diagnostic tool.

[mhackney]

I saw "Try no retract- e3d don't like much" - rubbish. And, the OP has the problem with a JHead too, it has a completely different internal path than an E3D V6 hot end.

[626Pilot]

Have you tried cleaning out the gear teeth with a toothpick? Sometimes ground-up plastic can lodge in the valleys of the gear, ruining traction.

Did you use thread locker when you tightened down the grub screw on the drive gear?

Have you tried adding a drop of canola oil to the Bowden tube?

Have you tried different filaments, and if so, did you notice if one was particularly "grabby" with the Bowden tube? I got an early spool of Taulman filament and it's just WAY too fat.

Is the drive gear lined up 100% perfectly with the filament path? If it's even a little off, it will add friction to the path.

I use 25mm/sec retracts @ 2mm on my E3D v6 and Cyclops hot ends. Same stepper and gear as you too, I think. I got them from TriDPrinting. PLA jams are quite rare.

[oracledude]

Notes/Observations:
Retraction is probably set too high. I was using Cura's suggestion of 4.5mm @ 50mm/s
The gear is torqued down pretty good and has thread locker on it. There is absolutely no play to it. After failures I clean the teeth out with a pick.
This is using various PLA filaments. I haven't heard of the canola oil trick - I'll try that also.
My bowden tube seems pretty long, maybe 450mm. I added some extra length to it due to not knowing the final position of the extruder. I'll try and tighten that up some.
I was also planning to replace the brass fitting on the EZStruder the one similar to the E3D bowden fitting to reduce friction and ease filament change.

[JFettig]

50mm/s might be too much for the gear motor. I set mine to 40mm/s max

[jason128]

There is NO PROBLEM with using retract with E3D hot ends. Don't spread false information please. Even with no retract, the micro snagging problem I described can take place. 100mm/s retract is way too high even for filaments like ABS. PLA requires a very slow retract (20mm/s) to keep from jamming. I've written extensively about it here and other places. PLA melt is thixotropic and fast retracts will cause it to "lock". The original poster does not say what filament they are using, I missed that last night. What filament/s are you experiencing this problem with. What you are observing is also a classic problem with too fast retract with PLA. Large retracts make it worse. With an E3D V6 you can use .5mm or so for retract length and 20mm/s for retract speed and should have no problems.

If the gear is grinding the filament, spring tension is not the issue.

Hey ease off... there's no misinformation being spread by me - ill give you that i probably should have said they don't like TOO much retract.

I say this as it caught me out, they require much less than the default settings that come for the seemecnc hotend- and i ended up witg the exact symptoms described last week.
setting the retract to zero is just a simple way to diagnose if this is the issue, there is obviously no way this is a permanent printer setting.

[626Pilot]

I normally retract fast (60mm/sec) and prime slow (20 or 25mm/sec). I think that was the upshot of the "thixotropic" thread. I suppose retracting slow could also be done, but when I tried it it was a little bit stringier.

450mm is really long for the tube. It should be long enough that you can move the effector to the edge of the print surface without it getting tight at all, but there shouldn't be a bunch of excess length. That will only add more friction, and give it more of an ability to act like a spring, which you don't want it to do.

[JFettig]

Again I will state this - your retract speeds might be too high for the motor! Run a program without filament - delete the heat up parts of the g-code and set the z a little high and listen for the extruder to skip.

[oracledude]

So on retraction, the motor hums and I hear a click coming from inside its chassis. Does that mean too much current, too fast, or too long of a retract?

[KAS]

Can you take a few pictures of the extruder? Specifically the alignment of the hobbed gear to the path of the filament guide. Will have to remove the clear shield to get a decent angle.

What is your extruder_steps_Per_mm set to?

Also remove the PTFE tube from the hotend. Mark the filament with a pen, extrude 100mm then measure the length.

A video of what's happening would definitely help.

[JFettig]

So on retraction, the motor hums and I hear a click coming from inside its chassis. Does that mean too much current, too fast, or too long of a retract?

Watch the wheel to make sure its actually spinning during a retract, I was getting missed steps on retracts and extends - but not always, so sometimes it would miss steps on a retract but not a extend - which would bite right into the filament that wasn't retracted.

[mhackney]

That clicking is the stepper skipping steps. This is the consequence of the force required to move being greater than the force the stepper can apply. Too much current would increase the force the stepper can apply so that is not the cause. Too little current could cause this (unless the stepper current is already at it's max. If that's the case, you need to look elsewhere).

Moving too fast can certainly cause skipped steps BUT if your current is set reasonably and the filament is at a good melt temperature your and the friction along the filament path is reasonable (i.e. not binding) then you should be able to extrude/retract at 50 mm/s with no problems. The retract length shouldn't cause an issue unless one or more of the parameters I just mentioned are off.

This all leads me to ask - how did you calibrate the thermistor in your hotend? It is very possible (I helped another member diagnose this/similar problem 2 years ago) that you think you are extruding at say 190°C and the actual temperature is 160°C. The melt will come out but is quite viscous. At slow speeds or pushing manually it seems fine but as soon as you start to print something it is too viscous to flow nicely and leads to skipping.

I also still think the ridges the cog is leaving on the filament could be snagging somewhere along the extrusion path. You need to rule that out too. In particular, you need to setup the E3D exactly like the instructions say - leaving a little gap between the nozzle and heater. If you don't do that, the nozzle can not be tightened against the heat break - which leaves a very small gap, which can capture the melt and cause issues. Similarly, the Bowden babe must be completely seated in the recess in the top of the break. I also like to taper the end of the tube with a sharp pencil sharpener so it more closely matches the drill cone. A large gap is created if this is not setup properly that can certainly snag the ridges on the filament. This is the #1 thing I've seen and helped others fix when having E3D V'n' extruder issues.