Help with Print quality issues (pict heavy)

[Barefoothurst]

Hello to all.
I have been lurking around the forums for a months now soaking in as much as I can. My son and I finished our Rostock max v2 build last month and now I am calibrating, slicing, printing, learning.... I am also a huge Starwars fan so when I saw the Tie Advanced Fighter model on Thingiverse, I had to print it. http://www.thingiverse.com/thing:14480 . I was having slicing problems with the stl file early on but after cleaning it up with Microsoft's Model repair servers it slices better now. Printed in Black PLA
Its printed 2x scale so its a pretty large print. It has taken the back half 26 hours to print. here is the back half in progress
[img]http://i647.photobucket.com/albums/uu19 ... 1a697e.jpg[/img]
[img]http://i647.photobucket.com/albums/uu19 ... f4deeb.jpg[/img]

in order to speed up the print I turned off the (avoid crossing perimeters) setting in slicer and I'm getting these small thin hanging "crusts" on the edge of the model. They come off really easy and I'm not too worried about them right now.
[img]http://i647.photobucket.com/albums/uu19 ... 4413b2.jpg[/img]
[img]http://i647.photobucket.com/albums/uu19 ... f48e86.jpg[/img]

My main concern is the bumps on the outer layers. Some are nice and smooth while other sides show filament bumps.
[img]http://i647.photobucket.com/albums/uu19 ... fc33bc.jpg[/img]
[img]http://i647.photobucket.com/albums/uu19 ... 56bb7d.jpg[/img]

I haven't figured out what is causing them. The filament its dry and fresh out of a sealed bag with desiccant.

here is the unfinished font half that I printed earlier. It seems to print better but was a very long print slow print.
[img]http://i647.photobucket.com/albums/uu19 ... c48a7a.jpg[/img]
[img]http://i647.photobucket.com/albums/uu19 ... bfb79d.jpg[/img]
[img]http://i647.photobucket.com/albums/uu19 ... 52401c.jpg[/img]

here are my settings for the back half print.

[img]http://i647.photobucket.com/albums/uu19 ... 64c9a2.png[/img]
[img]http://i647.photobucket.com/albums/uu19 ... 54dff3.png[/img]
[img]http://i647.photobucket.com/albums/uu19 ... d1fa05.png[/img]
[img]http://i647.photobucket.com/albums/uu19 ... 45d4e8.png[/img]

Do you see any obvious errors I am making? I am printing hot because i am trying to get some speed out of the Printer. Other than the Astrosyn Dampers, my V2 Rostock Max is stock. Any suggestions or tips wold be greatly appreciated.
Thanks,
Jason

[mhackney]

Very ambitious early project and actually very well done!

Those bumps on the side look like the start/stop seams for each layer. Watch when it prints, is this the area where each layer is started?

Your settings all look reasonable. I like to print outside in (External perimeters first checked in your 1st screen shot) to get a nice smooth exterior. Your first layer height seems a bit big to me but if you are getting the first layer to stick well, don't mess with it. You could speed things up by printing at .25mm layers. You sacrifice a bit of resolution this way but, hey, it's 3D printing!

If your machine is dialed in well, you could also bump up the infill to 75mm/ss (or faster) and speed things up.

[Barefoothurst]

so you think it where my print starts each layer.... That would make sense because it doesn't start the print on the flat sides , (which are smooth and free of bumps) it appears to start on the angled side parts where all the bumps are. Should I adjust my retraction and (extra length on re-start) filament settings to address this??

[mhackney]

Your observation is a dead giveaway!

I'd try printing with external perimeters first and see if that helps. You might also try the KISS slicer, it gives much better surfaces IMHO. The little nubs on the surface can sometimes be addressed with retraction settings but it usually comes down to how the slicer is generating gcode. Slic3r, Cura and Simplify3D (see their forum, there are many examples of these types of nubs there) all seem to have a problem with this. KISS is always dead on. If you watch the printer printing from these different slicers you will see the difference in behavior and KISS "continues" on to the next perimeter whereas the others stop, lift (if enabled) and restart. That is the root of the problem.

Also, sometimes you get better results NOT randomizing layer starts - uncheck the randomize external perimeters box. This might result in a seam in your part but that can usually be sanded, cut or scraped away pretty easily and is a lot less visually offensive than nubs everywhere (IMHO).

I have spent a lot of time looking at gcode and printed results from all of these slicers and this is what I observe. There may be settings that can address this problem but if so, I haven't discovered them yet. KISS generates very different perimeter paths than the others and it results in nicer finishes in my opinion and for my applications.

cheers,
Michael

[Eaglezsoar]

That is a great looking model and I am definitely going to download it. Thanks for finding this for us!

[Barefoothurst]

you're welcome. here is the mostly finished model. still needs to be glued, cleaned painted and sanded.

[Eaglezsoar]

No wonder it takes so long to print, that thing is huge! Very nice looking model.

[Barefoothurst]

Yes it's almost 11" tall and 8" wide