Chronic Nozzle Clogging Issues, Retraction Possible Culprit?

[mitchfx]

I'm having issues lately with any print that is taller than about 75mm and longer than around 4 hours where the extrusion starts to become very sparse and sometimes eventually just stops altogether. My printer is a Dremel Idea Builder (rebranded Flashforge Dreamer) and I've had many successful prints on it the first month of use, but this new problem has become quite chronic. I've repeatedly tried cleaning the nozzle using the Taulman "pull" technique and using some extruder floss + nozzle cleaning tool from MakerGeeks. This often remedies the issues for a little while but usually the sparse extrusion creeps back in about halfway through the next print.

I've tried a few different brands of PLA filament, all of which worked flawlessly for weeks prior. When the issue kicks in the infill seems to suffer most and gets quite spider-webby which is usually my first indication that things are going south. I even purchased a second Dremel a few weeks ago to get through a huge print rush and within a week it developed the same problem.

One thing I'm wondering is if there could be something in my print settings in Simplify that might be causing or compounding the issues. It would stand to reason if you don't have the retraction set right it could continually putting pressure on the filament feed...or even the opposite effect of retracting too much and letting residual plastic in the nozzle get carbonized. This is all pure speculation of course.

My prints are always at 100 micron and usually 3 outline layers (inside to out order), 15% fill. I've also tried variations on temp within the suggest range for each PLA with no improvement.

Any ideas or suggestions would be appreciated. Thanks.

[Scottbee]

The Dreamer series has a pretty serious design error where they terminate the thermocouple wiring at the carriage instead of running it all the way back to the control board (where the cold junction compensation lives). That means that the reported extruder temperature is not correct, and the true temperature can climb during printing... especially if you have the printer closed up (door, lid).

If memory serves me correctly, the Dreamer also has PTFE lined thermal tubes.. which can degrade at elevated temperature.

Add those two together and you have a formula for clogs and general extruder problems. I'm going to guess that your PTFE liners are now damaged and need to be replaced. And you'll have to do that with some frequency if you don't get the thermocouple design issue fixed.

[mitchfx]

Scott,

Thanks for the reply. What you are saying does ring true for what I've been experiencing. The degradation of the liner would explain how things work well for a few weeks then start to go awry. I noticed how the liner appeared to be some kind of white plastic material just yesterday and was thinking "uh oh". The thermocouple flaw would also explain why it only happens on longer prints.

I'm still within the Home Depot 90 day return window so I might take them back. I do however love the quality of the prints that this unit kicks out WHEN it's working so finding a suitable replacement might be a challenge. I have a Rapide 200XL coming in May-June (hopefully) but will need something else to tide me over until then.

[mitchfx]

A little follow up. After about 4 months using two Dremel printers I'm still experiencing these issues with long prints. Dremel support sent me a replacement extruder head assembly about 2 months ago and all my problems immediately went away with beautiful print quality once again. I also scored a second Idea Builder off Craigslist for next to nothing which had only 32 hours usage logged. It also was printing flawlessly out of the gate.

However both started to go downhill after about 400 more hours of printing, exhibiting the exact symptoms from before. For the first few hours of a print things are usually fine then begin degrading into sparse infill, crepe-like supports and lots of nasty lines or voids in the outlines. Scott's theory about the thermocoupler and PTFE liner make a lot of sense considering the nature of my problems and how/when then being to occur. I guess my next quest is to find out if there is anything I can do myself to rectify these design shortcomings, shy of buying different printers.

[Narg]

Simple question, is there a better liner that can be purchased? I'm about to start my 3rd rebuild of the print head on my Dreamer and would love to get better parts to replace if possible.

[mitchfx]

Narg,

I was wondering the same thing! Out of curiosity, have you been experiencing similar issues to mine? Ideally i would love to just upgrade the entire head assembly including the stepper, gears and hot-end but not sure if that is possible with this printer.