intermittent "air print" desperate for help... MB REP 2

Hello! thank you for taking the time to read!!!
I am just getting started in 3dprinting and have learned a lot in getting started, but now at my wits end. :confused:

Here is whats happening:
I start prints just fine perfect smooth stream and i "load filament" to get PLA to the nozzle before each build and to check for clogs.
It build the raft flawlessly and the detach layer works great. but randomly anytime after it starts building the real print it appears to stop extruding intermittently.It creates a small gap between the print-head and the build; which then proceeds to extrude small amounts of filament which forms webs and balls of string. it also appears to not extrude properly just before it starts stringing.
When i try "load filament" to check for extrusion it is slow then suddenly takes off and extrudes perfectly after about 2 seconds.

Here is what i have done so far to try to correct the issue:
I thought it might be temperature so i did research and tried several different temperatures which appears to have no effect.
I bought new nozzles and swapped out the original for an identical.
I completely disassembled cleaned and checked the entire print-head/extruder assy.
I tried different combinations of speeds and build quality.
the drive gear was slipping and if i press the filament in a little but it starts extruding. that seemed to go away after i cleaned the gear.
I would be totally grateful for any information you could provide that might send me down the right path.

PS: Really small things print perfectly but randomly anywhere after a half hour two ten hours later it will start the issue... really annoying!


Thank you AGAIN!!! :)

Possibly your spool of filament is binding?

@ssayer Thanks for the reply! Nope been checking that.
Right now out of sheer frustration I doubled the layer thickness to .1mm and upped the temp from the default 230c to 240 and *crosses fingers* that 'seems' to be the best print quality so far. much more liquid... I wonder if my thermocouple is reading way off... apparently rep 1 and 2 makerbots have a tendency to have that kind of thing...
We will see...

Still jammed about 7 hours in at about 80% done.........
the extruder clogged hard and the gear managed to cut the filament in two from grinding on the filament....
going to try again at 245c.
anyone else have any ideas why this might be happening?

Okay, it's definitely interrupted filament feed. I had this problem the other day and it turned out to be dust clogging my extruded nozzle; canned air did the trick. That said, it sounds like you've already eliminated that.

While upping the heat improves filament flow, do be careful. While no two hot ends will give the same reading at a given temp, I set my MakerGear M2 to 212C for PLA. Not saying you should use that number at ALL as you've got a different rig.

In any event, you're doing the right thing by gradually upping the temp in 5 degree steps.

As annoying as it would be, you should try to arrange to be there for the whole print. I sat there for three hours messing with cad software before I was finally there to witness the issue. If it's the nozzle, the filament will start squeezing out at an odd angle. If it's the gear, you may hear it skip or see it stop pulling filament.

Lastly, does your software give you the chance to mess with extruding settings? Make sure you've punched in the right nozzle size and filament diameter. Simplify3d also has an "extrusion multiplier" setting that I find needs to be tweaked for different types of filament.

- If your extrusion gear is stripping the filament down then you may some of these issues going on:

1) You may have some poor quality filament that is varying too much in size, circularity, or may even be over-sized (oversized will almost always cause a clog). Using some calipers make multiple measurements along the filament to make sure your filament diameter variable matches the filament your using. Take a look at my BLOG ARTICLE for more details on tuning this variable.

2) Another related possibility is that your extruder is trying to extrude more material than it can push out. This will cause back pressure to build up in the hot-end and will eventually make the filament stepper skip/strip the filament. The root of this is also directly related to the filament diameter variable. If you have a the value for the filament parameter set lower than what the actual filament diameter is then the extruder will try pushing more material than needed.

Thank you guys so much for replying!


@King_Alistair Ok so checked out the dust sticking part and did some research and apparently one trick is to use a mini droplet of a high temp oil ie; canola oil, will lube the extruder. I dipped the end of my black makerbot PLA, in soybean oil and so far not another incident has arisen! except for one weir reoccurring issue but i think that may be due to a instability in the build plate. I do level the plate every time. and yeah I do attempt to be there for the whole thing including cold pause when i go to work. I did make the mistake of leaving it overnight being overconfident in the printing working out... but that mistake will not be again.


@GOC So, I am using "official" makerbot PLA calibrates as so, but my next roll is inventables so I gotta check that one and calibrate. This is one of the original rolls.
and yes i think the problem was a blockage due to sticking filament and the more it stuck the more blocked it got.


Ok, so one more issues that I mentioned. I've always had that issue and even though I got the extruder (i think) fixed.
so when extruding flat surfaces it sometimes forms these hills or wrinkles. whats up with this? it randomly forms but usually at the ends of the build plate.
I think its cause the plate can wobble if pressed on. not sure though ideas?

http://3dprintboard.com/attachment.p...tid=4779&stc=1http://3dprintboard.com/attachment.p...tid=4780&stc=1

Thanks again so much for the replys'!

Quote:

---

Originally Posted by Archangel

...
I think its cause the plate can wobble if pressed on. not sure though ideas?
...

---

- Your right with that assumption. Those are waves from transitioning 'backlash', if you were to correlate your gcode pathing to those area's you should notice some path transitioning in those locations.