Under extrusion, new issue?


Hey everyone!
It’s been a long time since I’ve posted here and the i3 clone has been printing like a dream!

So here’s my new issue I’m beating my head against the wall to figure out. The extruder starts to under extrude at random levels. Sometimes the first level, sometimes the 100th, etc. There’s no apparent reason.

What happened before:
My ramps 1.4 board fried and the extruder driver card was getting passed too much current. Even if I dialed the potentiometer down, it would not go low enough. I swapped out the ramps 1.4, and the extruder driver board and adjusted the Marlin firmware for the new DRV8825.

The extruder motor, even during the under extrusion layers, keeps moving as if nothing is wrong. It’s working mechanically.

What else have I done:
I have gone through a few atomic pulls to clean the nozzle. I have disassembled the hotend to replace the ptfe tubing (Genuine E3D V6). I have baked the filament.

It’s almost like heat creep except instead of jamming completely, it will start printing again.

I’m lost on what to look at now. Here’s a link to some pictures of the “failed” prints.




This sure sounds like heat creep, but that is unusual with a genuine V6. Have you checked the hotend cooling fan (and shroud)? Or might you have damaged the inside of the heat break or nozzle, creating additional friction?



I’m thinking that it could still be heat-creep. Heat creeps enough to cause the jam, then eventually it creeps more to re-melt the jammed filament and allows the filament to flow again. Just a thought because this happened to me when I built my first DIY i3, although that wasn’t an E3D v6, it was a J Head … before I knew better lol



OK, the E3D fan boys are going to blow a fit, but, it’s worth a try as it worked well for me…

PLA’s generally don’t like all metal hotends… yes yes, many have no issues but a lined heat break is actually more reliable for PLA (and TPU). I’d highly recommend at least trying a cheapo knock off PTFE lined heat break tube, they can be found for like 6-8 bucks for a multiple of them even on Amazon. worth the few bucks to at least try. Even better is to get the Capricorn Heatbreak liner tubing (it’s 3mm exterior over the normal PTFE tubing that is 4mm exterior) I did this over the summer just as a random trial and error as I as having this same issue. not a problem since. And the Cap tubing has no issues with PETG temps and works like a dream. Have this setup now on 2 printers now and it has fixed 90% of my errors and random troubles I was plagued with.

other options,…
1-there could just be a smidge of smutz in the Heatbreak tube preventing the PTFE from seating 100% flush and leaving a gap that can cause minor issues.
2-the retaining clips that hold the ptfe tube in place are too small and allowing the hose clamp and tube to move a little bit up and down with retractions- this is a know issue with cheapo units (noted issue many have had with then Ender 3) that is easily fixed by printing a slightly thicker clip to replace the stock one as a temporary fix/test and then replace the part if it corrects.
3-clogged or just a bad nozzle. I’ve gotten too aggressive with tweezers and/or needle nose pliers pulling drippings and actually scared the nozzle and it flared into/over the hole making it in effect smaller. though that’s an easy to check for by just extruding in the air and watching how bad the curl is of the extruded filament.
4-just plain bad filament…? not necessarily wet, but under or over sized diameter
5-dirty/clogged extruder gears, clean off with a dollar store tooth brush usually works.

all I can come up with off the top of my head. … but honestly, had the same issue and the cheapo heat break tube with the liner fixed it



My guess was heat creep as well. This happened to me on my Prusa MKS2 and 2.5 with genuine E3D V6 as well with PLA and seems eventually resolved with the new extruder parts Prusa had released this summer which improved the airflow for the heatsink. In my case it usually clogged the nozzle nearly completely, but I could imagine that it varies depending on how much heat creep you have.



On a random thought, I turned my retraction off and the problem went away. I didn’t have any crazy retraction though, 5mm @ 60mm/s. I tried turning it down to 40mm/s but the issue remained.

I am not sure why, after months of printing with those retraction speeds, it would suddenly become an issue. I’m going to try breaking down my hotend again and go through cleaning each piece by hand to ensure it’s not the issue.



dou you have a bowden or a direct setup
1mm should be fine at a direct setup



Direct Drive. The problem with 1mm retraction is the stringing continued. I’ll try adjusting settings as well and report back.



then your filament is not dry or/and the temparature you are printing with is to hot.
The print looks very glossy -> printing hot :wink:

maybe the temp sensor got damaged and is reading bullsh*t now.
or with which temparature are you printing?



I’ve been using eSun PLA Pro which has a range of 205-225. I normally printed at 215 for about a year without issues but after all this started, I dropped the temp to 205. I’m going to have to mess with the settings and such anyway. I don’t like when problems randomly pop up. It’s… frustrating.

Thanks for your suggestions, everyone.



5mm is entirely too high for a direct drive. In fact it’s often entirely too high for a Bowden setup with E3D all metal hotends. I was doing 5mm for a while with mostly PLA then started to get jams from retraction. I go with 3mm and switch to 2mm if a filament jams overtime. But 1mm is max you should use for direct drive, often less. Stringing is something you just have to accept, especially with all metal hotends. @thomllama is right that PLA does better without all metal hotends. Have you tried a temperature tower to see what other temperatures are acceptable with less stringing? Don’t worry about stringing so much if that’s what’s stopping you from retracting less. Strings can be wiped off or with blowing a hair dryer on it for a few seconds. Worry more about successful prints and surface quality, less about stringing; it’s an overrated concern in my experience.



I totally agree, 0.6 should usually be sufficient with direct drive, 1.0 at the very most.



Do you have a fan cooling the DRV8825 and does it have a heat sink? I just have to wonder if it is having a thermal shutdown.