Why does PLA hate me now?

I have a curious issue with PLA that I am hoping someone can help me with :smiley:

Pics here: https://www.dropbox.com/sh/chnlr1qjc18uw6g/shtz54-KRR


Background: I initially had the same issues with printing I believe everyone has (TAZ3 is my first 3D printer) but the forum and Lulzbot staff got me over the hump and I was able to print with ABS with only the normal issues (warping/shrinkage) which was no surprise as my printing environment is often in the 65F range. After printing almost 3 spools of ABS I decided to try PLA. I printed an entire Prototype Supply (from Amazon) spool of PLA with only one issue (in the center of the spool the filament was brittle for a few meters and broke). After that I printed an entire spool of ODB glow in the dark PLA with a similar experience (no issues except for 1 section of brittle/breaking filament). After these two spools I wondered if I would ever print with ABS again unless I had a specific need for the flex found in ABS vs PLA.

That brings us to recently. I purchased a spool of Jet brand yellow PLA and had terrible luck. I assumed this was the price to pay for getting cheap filament and bought another spool of ODB PLA in orange (remember I had great luck with this brand previously) and also had terrible luck and was unable to print things (using same gcode) I had printed previously with no issues at all. I finally decided I had learned my lesson and purchased a spool of LulzBot translucent blue PLA (and a green one which is unopened for now) and was shocked to find I could not get it to print either. I dinked around with different settings (including the Lulzbot approved Slic3r settings) with no luck at all. I tried printing files I had printed flawlessly before, etc, no luck. In the link above are some pics of the failures. I checked everything I could think of, replaced a slightly worn small gear, replaced the hobbed bolt, etc with no change. I went back to IC3D ABS (the red prints) and it works great (was able to print the Octopus tablet stand using the fast settings in a touch under 7 hours!).

Note: The pictures with the 4 prints (2 blue and 2 red) are as follows from left to right:

PLA sliced with ABS settings, PLA sliced with PLA settings, ABS sliced with same ABS settings as 1, ABS same as 1 and 4

One other note: The clamp on the extruder that has the bearing in it that pinches the filament into the hobbed bolt has a slot that guides the filament down into the hole that goes to the hot end. That guide groove has been worn out (my understanding is that glow in the dark filament is quite abrasive?) towards the front of the printer resulting in more of an L shaped groove vs the normal I shape. I cannot see how this would be related but figured it is note worthy.

For now I am back to using ABS but would love to be able to use the 4 spools of PLA I have now :cry: Any thoughts or ideas based on the pics above would be greatly appreciated.

FYI: I used the ABS and PLA no support medium settings found here: http://www.lulzbot.com/support/taz-slic3r-profiles

Temps for PLA were the recommended 180C and 50C

For reference my job log shows I am creeping up on 175 print jobs (this does not include ones that failed almost immediately) and many of the jobs were multiple parts/sizable).

wait, you replaced the hobbed bolt? Did you recalibrate the extruder at that point? The e-steps value is in part based off the hobbed bolt diameter. You may want to re-calibrate your extruder before going much further, or put the old hobbed bolt back in.

Other things to check:

  1. Do the bearings in the extruder all still move (the idler bearing can get gunked up sometimes)
  2. is the small gear set screw really tight
  3. is the idler spring tension set right.
  4. Is there shavings in the bearing chamger
  5. Check the filliament diameter settings in slic3r and measure your filliament exactly and enter that value in the filliament settings section

That is a rediculously worn out idler filliament guide. I’d print a new one if I were you because if nothign else your filliament is hitting the idler hobs at an angle now.

Thanks for the input!

The hobbed bolt I put in was actually the original one that came in the printer, it was replaced with another (I assume identical) one from Lulzbot while we were troubleshooting other issues initially.

#1 The bearings seem to move very nicely, during my troubleshooting I removed them, wiped them down/blew them out and reassembled. I torqued the nut enough so that there is no lateral play but it still turns freely.

#2 The small gear (this is the second one that has been on it during this troubleshooting) is very tight as is the set screw.

#3 is a loaded question I think it is set right and based on my previous performance with PLA/ABS I think I have gotten the hang of it but cannot be sure :smiley: I do not seem to have jam issues and when spot checking it the grooves seem consistent. It does seem like PLA filament is harder and the hobbed bolt does not “bite” into it as aggressively as ABS even if it is tightened very tight.

#4 I check/clean the grooves in the hobbed bolt very frequently and during this troubleshooting session cleaned everything when I disassembled the plastic bits of the extruder.

#5 I have spot checked the diameter with calipers on all the rolls and they are very close to the 2.89 default. I have not really played with this much however…I need to do that!

As you see in the pics I have 2 nice new red ones ready to rock…just need to swap one in :wink:

Thanks again!

Have you cleaned out all of the previous ABS from the nozzle before starting to use PLA again?
Just a thought, as the remains of ABS will not melt nicely at PLA temps and could cause blockages.
Maybe worth taking the nozzle off and giving it a thorough clean out, if you haven’t already.

Antony

I normally run at least 100mm of new filament through at the higher temp when I switch between ABS/PLA.

I worked on this some more today and think I may have found the problem. The idler clamp is slipping. I am torquing the bolts (the ones with the springs) down to 10mm per the manual (and even a little more at times) yet after a print fails I measure and they are out to 11mm or so.

you can glue some fine grit sandpaper to the plastic rounded latch pies that presses the idler in place to increase it’s “bite” Standard CA superglue, make sure you don’t glue anything important together though

Well, I got the idler changed and tried printing again and it was doing great for about 1.5 hours then jammed/stripped the filament. Now my hot end will not heat up Not sure if it cooled down first thus causing the issue or not.

One thing then another :cry:

Heat Resister = no resistance at all/open

To the store! https://www.lulzbot.com/products/heat-resistor-47-ohm

Instructions on replacing the heater resistor can be found here: https://www.lulzbot.com/support/replacing-your-budaschnozzle-heater-resistor-or-thermistor When you have the resistor out of the housing, would you mind sending an image of it to support@lulzbot.com?

Email/pics sent to support :smiley:

New heat resistor, new idler, new idler latch = same problem

I can still print ABS prints wonderfully including lengthy semi-difficult jobs (enclosure made all the difference in the world with ABS/warping) but PLA is still working me over. I have tried the recommended PLA fast, med and fine settings with no luck.

It seems to be an extrusion issue and oddly enough it seems to be time related (heat??)? When I first fire the printer up I can actually get some layers to print cleanly and have even printed a few coasters (30 minute jobs) successfully with PLA. However after that things go badly and I it starts “feathering” as seen in the pics. Eventually it gets to the point where I cannot even get the extruder to successfully spit out 100mm of filament. I remove the chewed up filament with the big divot in it where the hobbed bolt chewed it up, pick out each groove and blow out all of the shavings with canned air, insert cleanly cut filament, tighten idler (tried many different tensions), try to manually extrude 100mm 5mm at a time, cannot make it more than 5 or 6 5mm sections before it slows then stops Removing the filament shows a divot at the top and based on how tight I adjust the idler either light grooves up the filament below the divot, or medium grooves. If I go very tight there are medium grooves, mini divot, medium grooves, mini divot, etc until you get to the big divot at the top.

Does anyone have any ideas? I am at my wits end and really do not want to have a printer I cannot use PLA on :cry:

Are you using active cooling when printing with PLA?

I am not using any active cooling. Ambient temp is below 70F (showing 67-68F)

It is possible my original 2 spools of PLA that printed great were slightly lower temp but not much.

It is frustrating that it worked so great before with no active cooling but if you think that is a factor I can certainly round up a fan to throw on it…

Thanks again for your help!