Slc3r top/solid layer over extrusion

Hello,

I'm writing here because It seems I cannot help myself to get some settings right in slic3r.
For example, I'm trying to print the file attached to this thread. Everything seems to go ok until the print gets to the smaller part. It starts extruding a lot more plastic for the infill and because of this the layers start getting thicker until the nozzle starts digging into the layers and the part ends up all deformed on top... Things that I've tried but have not worked: changing layer height, extrusion widths, infill levels, speed...
It seems that If I slice without solid top and bottom layers the problem kinda goes away.
I've tried modifying extrusion width for infill, solid infill and top solid infill, but nothing seems to help.
I'm running Slic3r 1.2.9 on Ubuntu 14.04 64bit. My printer is a Prusa i3 running a wade extruder for 1.75 filament with a 0.4 nozzle.
The printer is well calibrated and has no trouble printing parts don't have small features.
Any thoughts on what might be wrong?

Thanks!

When the layer area is below some preset threshold (Print Settings>Infill>Solid infill threshold area) slic3r switches to solid infill. With such a small part, it finishes the layer quickly and then starts a new layer before the last one has had time to cool. The result is the gloppy mess you're getting.

You need to give those small area layers time to cool before the nozzle comes around again. You can do that by printing multiple parts, or by printing a sacrificial part that is at least as tall as the one you're printing. I find that a 10-15 mm diameter cylinder usually requires long enough print time per layer to let small area layers cool before the extruder prints on them again.

---

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

Thanks for the tip. I've tried to print the part with PLA and use a cooling fan. The result is indeed much better but I still had some trouble. After looking at the layers and playing around a bit with the settings it seems that "bridge flow ratio" with the default value of 1 is too much. When printing the layer just above the hole in the tab the extruded plastic would be so much that it would take up more than one layer height and cause the print head to dig in on the next pass.
Bridge flow ratio doesn't seem to be very well documented. Can anyone suggest how to set a proper value? Or just use trial and error?

When printing a bridge since the filament is flowing into thin air, it doesn't get squished flat on a previous layer, the cross section is circular, the same diameter as the nozzle if the flow ratio is 1. If you reduce the flow ratio the extruder's motion will stretch the line thinner until it anchors it on the opposite side of the bridge. That will leave horizontal gaps between the bridge lines but they will print flatter and subsequent layers will look better. Try a bridge flow ratio of 80% as see if that improves things a bit.

Edited 1 time(s). Last edit at 11/24/2015 10:02AM by the_digital_dentist.

---

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

I did a bit of experimenting with bridge flow ratio and it seems that for very small parts a value of 40% seems to help a lot. I've also learned that it's better to look at Slic3r's preview layers a bit more carefully. I can tell where possible extrusion problems might take place. Also I think that the quality of my filament and hot end might not be up to par .