Problem printing an arch with ABS  

Problem printing an arch with ABS

I am a new Prusa owner and love my machine! Thank you!

I am having trouble printing a small arch in ABS. After reading the forum, I tried playing with the following settings:

- Lower filament temperature
- Increasing the Bridge Fan Speed
- Slowing down the Bridge speed
- Increasing the support angle

In the end I got the best results with all Slic3r defaults for ABS, .2mm layers, and a 40 deg supports setting - as can be seen in the attached image (part # 6). Part #3 is all the same defaults, but with no supports.

You can be seen in picture of #6 with the supports, there is still kind of a curling of the ends of each layer where they end along the arch. This does not happen with PLA with all defaults - the print is much cleaner. In PLA I can actually get a pretty clean print even without the supports, but I need ABS for this part.

Can anyone suggest what changes I should try? From my reading I've learned that more cooling during bridging and slower speeds can be important, but I can't get any better after playing with the above items than that shown on part #6. Also, I guess this isn't really a bridge situation until the vary last layer of the arch - and the problem is occurring before that point.

Thanks for your help! Looking forward to learning from all of you.
Jon