Bridge troubleshooting

[bobthechemist]

I'm trying to improve bridge quality on my Makerfarm i3V Prussa. This thing (the casing.stl) has a bridge that isn't visible in the default view and it is the object that I'm using to test my printer. I just printed and installed this cooling fan and tried the casing.stl object in both ABS and PLA. Here are my results.
bridgeprintattempt.jpg

The gray filament is PLA and the green filament is ABS. Both print struggle with bridging between the outer and inner circles. ABS appears to bridge outer-to-outer reasonably well and PLA shows a bit of sagging in this region. When I paid close attention to the printing, it looked as if neither print "knew" where the edge of the inner circle was, and therefore the hot end would not travel far enough to attach the filament to the inner circle. It is probably not visible in the image, however, the inner circle is one perimeter at the base, and then extends to 3 perimeters when it gets to the bridged layer. This behavior is not intentional, and I do have 3 perimeters set in my slicing software.

Any suggestions on how I might be able to troubleshoot this issue are welcomed. I'm assuming that the STL file is sound, since others have indicated that they have made this thing. Therefore, I suspect there is either a problem with my hardware or the slicing options I have set.

I mentioned above this is an 8" i3v Prusa from MakerFarm and I'm using Slic3r 1.29 to generate the gcode.

[Davo]

I us 2/3 of my normal print speed and crank the fan up from 50% to 100% for bridges and overhangs.

[dbregman]

You might also lower your printing temp to as low as the filament will allow.

[bobthechemist]

You might also lower your printing temp to as low as the filament will allow.

Thanks for the suggestion, I will give that a shot. I'm now starting to think that the issue isn't really bridging, since I am able to print this bridge test in PLA with very little sagging. It might be how my slicing software is creating the perimeters, but I'm not sure how to debug that.

[LambdaFF]

but I'm not sure how to debug that.

Have you looked at the gcode layer by layer preview ? Might give you an idea of the problem.