Bridges and Slic3r.

I'm trying to print the 50mm "bridge torture test" from thingiverse and I can't seem to get Slic3r to cooperate. I've dialed in my bridge speed settings, flow ratio, etc, but when it comes time to print the bridge, it prints a "perimeter" of the bridge which it treats like a perimeter instead of a bridge before it prints the actual bridge! The result is that it doesn't anchor properly and breaks. I've posted a (sorry, poor quality) picture of what I'm getting. The first one was with all cooling disabled and I fully expected it to look like that and the rest were my playing with different settings. If you'll notice, there is always one broken filament that is dangling down. That's the first line of the bridge (that Slic3r treats like a perimeter). It doesn't anchor at all and it looks like it isn't using enough plastic in the beginning since the trace starts out thinner than a strand of hair before it starts to take shape but by then it's too late. It breaks and then dangles.

I'm printing with ABS at 210 degrees, 0.5mm J-head nozzle, 0.3mm layer height with a layer width of 0.45 (set manually) and Slic3r 0.9.9. I did modify the scad file from thingiverse to make the object match my layer height/trace width.

That bridge on the right looks good. The one filament that doesn't anchor, could that be because the fan turns on only while bridging? That slight delay prevents it from cooling enought to hold?

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Yvan

Singularity Machine

I thought of that myself, there's only one problem. The fan doesn't kick on when it's printing that! Slic3r treats it like a perimeter and leaves the fan off until it gets to what it considers the bridge. Also, one of those pics I posted (second one from the left I think) was printed with the fan on full speed for the whole print. With the fan on, the print bed could not maintain temperature although the part still stuck to the bed.

Okay, now I see what you mean about perimeter vs bridge.

What kind of fan setup do you have? I'm trying to add a duct on mine(modeling it slowly in Cinema 4D). I've also found that leaving the fan on cools the bed,(even just at 30 or 40%) and I eventually get one corner of the work piece lifting off. I have just been pausing the print and taping a little square of paper on the glass build platform. That keeps the air flow off it. I am hoping adding the duct will direct the air flow towards the hot ABS, and not so much towards the heated bed.

In any case, I may have to set aside the 3Dprinter(again) because someone asked me to build something, ASAP. My head is now swirling full of metal housings and fiberglass molds and such... I have much brainstorming to do!

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Yvan

Singularity Machine

I just have a fan that is aimed at the PEEK insulator on my j-head. There is no duct. I know that isn't ideal for cooling the plastic that's extruded, but it's what I have as of now until I can successfully print a duct. I tried to print one, but when I got to the top the filament slipped off the hobbed bolt and it stopped extruding. I'll have to correct my filament guide somehow to make it work properly at high Z heights. Anyway, as far as getting Slic3r to cooperate, I've pretty much given up on it and am starting over with skeinforge. I hate its UI, but it does give me control over a lot more parameters than Slic3r does, and it's expandable (and I can learn python). I have yet to print anything with it, right now I'm just trying to get some gcode that looks like it'll work.

My first skeinforge print turned out pretty well! The top layer bridged properly and the object is deafeningly functional. I've actually never successfully printed this with Slic3r. The attached object is straight from the print bed, no cleanup needed. There is room for improvement though, but over time I think I can get some pretty good prints with it, maybe even bordering on awesome. It seems Slic3r is the future of 3D printing and skeinforge is the present unfortunately. Slic3r is so much easier to work with, but it just doesn't get things right sometimes and in that case there are few options to correct it.

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0.3mm layer height with a layer width of 0.45 (set manually)

Have you tried adjusting your bridge flow rate ? As you set your width manually you might need to adjust that too. A line width of 0.45 seems a bit small for 0.3 layers anyway, that only gives you a WOH of 1.5 which will most likely cause problems with stability of your prints.

I did try that (down to 0.9) and it did help a little. The problem is the part that doesn't anchor properly is the part that Slic3r doesn't consider a bridge (the perimeter of the bridge) so bridge flow ratio has no effect on it. Also, when I let Slic3r choose the trace width, it goes for 0.7 (2 1/3 WOH) which I've noticed doesn't give very good quality prints (more delamination). Although come to think of it, there may be another reason for that since you'd expect there would be less delamination in that case.