Help identifying print quality issue

I'm running into a problem in which the top layer of some of my prints have raised ridges (see pics). This only happens on the top layer - as far as I can tell, layers underneath look to be coming out OK. Also, this problem only seems to happen on certain prints and in certain areas - printing the same part twice results in ridges in the same area of the prints, but I have not been able to notice a pattern of what could be causing this. I looked through the print pictorial guide and did not come across anything that looked similar, but maybe I missed something. Can anyone help identify the issue? I'm using a MendelMax 1.5 with Budaschnozzle hotend, running Repetier and slicing with slic3r - printing ABS at 240C (but I've tried the same filament at temperatures as low as 225C and received the same problem).

Thanks!

Edited 1 time(s). Last edit at 01/26/2016 12:17AM by dan0291.

It looks like the first layer over the infill did not cover, and then the layers over that broke as well.

Note that the first layer over infill is Bridging!
If the feed rate is too fast, or the bridge flow ratio is too low then the extruded filament will stretch and break when it crosses one of the sparse infill lines.

So increase your bridge flow ratio (with Expert settings on, Advanced tab, Flow) - try 10% or more, and decrease your bridging speed.

Let us know if that fixes it.

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My printer: Raptosaur - Large Format Delta - [www.paulwanamaker.wordpress.com]
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I've had prints come out like that. In my case, slic3r set the infill width too narrow- slic3r set it to a width that was narrower than the extruder nozzle. I fixed it by specifying the infill line width instead of letting slic3r decide how wide it should be. I don't know what caused slic3r to do that because it was working fine for a long time, then one day decided that the line width should be narrower. Slic3r does things like that now and then...

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]