Extrusion problems with Rostock Max - Halp!

[FullMetalBoxers]

Hello all,

I searched the forums a bit trying to see if an answer already existed to this issue, but wasn't able to find the solution I need. I'm sure this is probably a no-brainer to some of the experienced RepRappers here; this is my first 3D printer, so I could use the benefit of some experience.

I've had my Rostock assembled for a couple weeks now but have had trouble getting decent prints out. I've followed the calibration instructions, tuned my thermistors, got my bed leveled and worked the "Delta Blues" out of the system, so now it seems that my extrusion settings are my last hurdle. In short, I'm having problems with blobbing, polyps, and excess extrusion in general. Nozzle width and default extrusion width are set properly (0.5mm and 0.55mm respectively), and various retract settings don't seem to be doing the trick.

Here's an example:
[img]http://i.imgur.com/TZonYTO.jpg[/img]

As you can see, the base looks fairly nice... a tiny bit of curl at the corners, but I imagine that's easy to fix. Once it gets to the smaller "towers," however, it turns into a horrid mess. I watched the printer print this one and it looked like the hot end was just plain melting the previous layer down into a goopy sludge as it put down each layer. Here's what the nozzle looked like after the print was done:
[img]http://i.imgur.com/02tjuf1.jpg[/img]

I tried z-offsetting another print by a tiny amount to see if maybe my Z Max was just set too close to the print surface, but no luck. Any higher and the filament refuses to adhere to the build surface, leading me to believe that my Z Max is set correctly.

I have also noticed that when "primed," my extruder nozzle seems to have a constant, slow "ooze" of filament that continually creeps out. The only way I've found to stop it is to retract enough that the nozzle is no longer primed, but then I have to re-advance the filament to get the nozzle to print anything.

I am currently running Repetier Host Mac, latest version (0.56 I believe,) and the version of the Repetier firmware that was patched for the LCD controller. Any advice will be greatly appreciated!

[Polygonhell]

The pyramid is a difficult print, and I would personally start with something easier, but the first thing you want to do is print slowly and watch the print, are the blobs at the start or the end of a travel move, or are they just everywhere, are they worse near the start of a print move etc etc.

To me it looks like you are printing too hot, and probably the extruder is slipping when it retracts, leading to extra plastic on the prime, but without watching it print it's hard to tell.
Turn retract off entirely and see if the print has less blobs, you'll have a lot of strings, but it narrows down the cause. You can then move onto calibrating the retract prime settings.
Try printing 5 degrees colder and see if it's better, repeat until it won't print, or the print delaminates.
Run a fan while printing the tower pieces and see if it looks better.

[FullMetalBoxers]

Thanks for the reply! I can take a short video of the printer printing, would that help?

The blobbyness of the towers seemed more like it was due to the nozzle overheating the towers than anything else. Is that something the fan could help?

The pyramid above was ABS printed at 230, with a 90 degree bed. I'll try printing cooler and see what happens. I'll also try a print without retract.

[JohnStack]

The pyramid is a difficult print, and I would personally start with something easier, but the first thing you want to do is print slowly and watch the print, are the blobs at the start or the end of a travel move, or are they just everywhere, are they worse near the start of a print move etc etc.

Mr. Polygonhell:
What are the causes blobbing:
1) at the beginning of a travel move?

2) end of a travel move?

To me it looks like you are printing too hot, and probably the extruder is slipping when it retracts, leading to extra plastic on the prime, but without watching it print it's hard to tell.
Turn retract off entirely and see if the print has less blobs, you'll have a lot of strings, but it narrows down the cause. You can then move onto calibrating the retract prime settings.
Try printing 5 degrees colder and see if it's better, repeat until it won't print, or the print delaminates.
Run a fan while printing the tower pieces and see if it looks better.

Printing too hot causes delamination. That makes total sense based on what I was doing this AM. Can you reduce the bed temp after a few layers?

Is there a good primer in the forum on retraction? I've looked.

(thanks, great question!!!)

[barnett]

Not that my pyramids are perfect, but I got significantly less blobbing after calibrating the extruder flow using the method described by polygonhell here. Before I did that, I was pumping out too much plastic and the nozzle was dragging though the extra blobs, resulting in strings and blobs.

[FullMetalBoxers]

but the first thing you want to do is print slowly and watch the print, are the blobs at the start or the end of a travel move, or are they just everywhere, are they worse near the start of a print move etc etc.

I'm currently printing the Rostock spool rod hosted on Thingiverse (should help some filament starving issues I noticed on a thin wall test print when I was playing around with some of your suggestions earlier) and noticed that the polyps seem to very specifically be happening at the end of a print layer. Is there a specific fix for that?

I'm still noticing some inaccuracies in the outer perimeters - although I have read that that may be a peculiarity of Slic3r itself always printing perimeters inner-to-outer - but overall this print is looking much better so far. I believe the new Repetier firmware the SeeMeCNC guys posted about seems to have helped somewhat. Step by step, step by step...