Is Slic3r's Bridging capability busted???

[Roxy]

I'm running Slic3r 1.1.7. I'm trying to print some multicolor pieces for a Pump-Jack for my brother (who is a recently graduated Petroleum Engineer). There are several pieces in the design that are multicolor. I have to switch filament at the right time to make it work. The Yellow lines you can see are raised above the main black part of each piece.

Statoil-Pumpjack.jpg

Now... No matter what I do, Slic3r can't bridge the lines when the color change happens. It decides to bridge the gap in the long direction. Check out the .STL and .GCODE files attached below. If you feed the .GCODE file into: http://gcode.ws/# you can see each level of the print. When it is time to change the filament and bridge the gap, Slic3r goes Brain Dead and goes the wrong direction.

I've tried re-orientating the parts when they are combined to make the .STL file. I've tried rotating the .STL file on Slic3r's print bed. It refuses to bridge the gap in the short direction!!!!

I've tried Cura and it bridges in a rational direction. But the problem with Cura is I can't control the amount filament or speed during a bridging operation. (Is that true??? That seems like such a limitation!)

Does anybody have any ideas?

[Geoff]

I feel silly suggesting it because you probably know more about it than me, but does the starting point for each layer possibly have anything to do with it, ie the options for "Nearest, Random" etc...
I can't say I colour swap with my kossel yet so haven't actually tried what you are trying to do - and unless the bridging is happening at the start of a layer, my above suggestion is even more useless

[Roxy]

No... The bridging happens all during the layer. Usually you get a lot of perimeters traced first. And from the looks of it, usually, there is one line of perimeter that is left undone on the edge of the bridge. I suspect that is done so the bridge material has somewhere to tack onto. But the crazy thing is Slic3r is making the bridges go in the exactly wrong (longest) direction.

[3dkarma]

There are a number of historic bugs in Slic3r regarding generating bridges in the wrong direction - it seems you've hit upon another one.

I had a brief look at the STL and had some success by modifying the parts that would be printed in yellow. The internal edges are angled, which Slic3r doesn't seem to like. I made the edges square internally on one of the pieces and bridging was generated correctly across the shorter span.

[Roxy]

There are a number of historic bugs in Slic3r regarding generating bridges in the wrong direction - it seems you've hit upon another one.

I had a brief look at the STL and had some success by modifying the parts that would be printed in yellow. The internal edges are angled, which Slic3r doesn't seem to like. I made the edges square internally on one of the pieces and bridging was generated correctly across the shorter span.

OH??? The part looks better angled, but if that is what it takes to get it to bridge.... So Be It!!! I'll change the source and see if I can get Slic3r to behave itself!

THANKS!!!!