Problem with PLA at 100 micron Resolution

[furicks]

Hi all,

I'm hoping someone maybe be able to offer some guidance on a frustrating problem I'm having. I'm running a Makerbot 2x with almost all plastic parts replaced with aluminum. Extruders, arms, carriage. It's a very reliable machine and can easily print ABS, PLA, Nylon etc. I have active cooling fans for the part installed as well.

I can consistently print PLA at temperatures as high as 230C and speeds up to 7000mm/min without problems as long as I don't go to a layer resolution below 0.2mm. The filament literally never strips. I haven't seen stripped filament in months so I can rule out that as a problem. I'm trying to print the attached object at 0.1mm resolution and I'm consistently getting nozzle jams.

Photo of one of many filed prints

Let me tell you a few symptoms I'm experiencing. All of my tests seem to fail right around the same place on the print. This is right where the bottom hole starts. You can see in the print where a few layers were not extruded properly. When this happens the drive motor just clicks. There's no slipping filament but the motor continues to try to push it through. The hot end appears to still be hot as I am able to remove the filament, cut off the end and resume printing. In this photo you can see the print continued for some time and then failed.

Things I have tried:
1) Very hot and cold temperatures between 180C and 230C - this seems to have an impact on the amount of ooze but not much else about the print. Fails in roughly the same area.
2) Calibrated Extrusion 1.72mm filament and way under extrusion 2.00mm filament and/or extrusion multiplier 75%
3) Very high and Very slow print speeds 3000mm/min up to 7000mm/min
4) Manual Extrusion Width multiplier from 0.5mm to 0.35mm

I'm happy to try any settings you guys might thing would help as I've been running experiments for days and I'm running out of things to try. Thank you!
Steven

[DarthRevan]

Try turning on retraction?

[furicks]

I'll give retraction a try tonight. I turned it off because I was trying to reduce the number of variables. Thanks for the suggestion!

[dkightley]

I've been successfully printing in PLA almost exclusively at 0.1mm layer thickness on my Replicator 2 ever since I bought the software some months ago.

I'm not sure how similar of different the setting requirements are between Makerbot's 2 and 2x models, but I've attached a factory file of a pair of semis you can lift setting off to try....

[furicks]

Thanks for the factory file. I'll give these settings a try for sure since they are confirmed functional on a similar printer. They look to be pretty close to stock Simplify3D settings. Would you say that's correct? Are you taking any extra steps to calibrate your machine to these settings? Do you use a specific brand of PLA?

I'm starting to think the Replicator 2x barrier assembly is to blame. It's as if there's a small gap between the nozzle and the barrier tube which is just enough for PLA to squish into and get stuck when under the increased pressure from the reduced layer height. I'll put up some more pictures of the results.

[dkightley]

I think you're right that my settings are close to the stock settings, and I've not really needed to do much adjusting to get a decent print quality. The only small issue I still have is a small amount of stringing where the model reduces down to two or more small cross-sections (for example when printing chimneys on rooftops!), but I currently slice the offending bits off with a scalpel.

I use filament from http://www.faberdashery.co.uk. It's more expensive that most filament, but I find it extrudes very nicely, it is of consistent diameter and I get almost no issues with included moisture.

Your mention of the gap between the nozzle and the barrier tube has reminded me that I did once suddenly get problems not so dissimilar to what you're suffering - an apparent lack of plastic being extruded towards the end of the print. Replacing the nozzle seemed to make it go away..it was probably a piece of carbonated plastic causing the problem. This new nozzle had a slightly longer thread that allowed me to close the gap....again, not sure if this helped or not!