Summary

This is a test object for tuning your printer to make accurate prints. It's a remix of http://www.thingiverse.com/thing:42623 by walter, with a loop added so you can attach a tag with info on the options you used to make it.

Instructions

I'm using skeinbforge 50 and a Makerbot Replicator, and have found these parameters to be good ones for tuning:

Bottom->Altitude: If your gaps are closed on the bottom layer, but open the rest of the way up, you're printing the bottom layer too low. Turn on the Bottom plugin and try different setting of Altitude. You'll know you've gone too high when your filament doesn't stick.

Dimension->Filament Diameter: Measure it with a micrometer. I've found filament ranging from 1.72 to 1.82 all labelled as 1.75. Don't have a micrometer? Get one, they can be had for under $40.

Dimension->Filament Packing Density: If your layers above the bottom are too fat (causing the gaps to be closed), try raising this value. If your solid infill has gaps between the filaments, lower it. Basically, the lower the value, the fatter your filament will be.

Dimension->Retraction Distance: If you find that the lowest layer of the outlines of your gaps are getting dragged around because they are staying attached to the extruder when it moves away, increase this a bit so the extruder will suck the filament back in before moving.

Fill->Infill Begin Rotation: The Replicator default is 90 degrees. I found I got better results by switching this to 45 degrees. YMMV.

Fill->Infill Perimeter Overlap: If your perimeter filament looks fine, but your infill bulges up near the edges, try lowering this a bit. Going from the default 0.3 down to 0.2 helped me a lot.

I keep notes for each print on paper tags I picked up in an office supply store for $5 for a pack of 100 tags. A handy way to see what you've got set is to do do a 'diff -r' of the default profile and your modified profile. This is what I do on Linux:
% diff -r ~/makerbot/replicatorg-0040/skein_engines/skeinforge-50/skeinforge_application/prefs/Replicator\ slicing\ defaults/ /home/khearn/.replicatorg/sf_50_profiles/yellow\ ABS/

Of course, you'll need to change the paths as appropriate.

I also note the "grade" for each print on a scale of 0-10, for how many of the gaps are open, plus a decimal if part of a gap is open. So if all of the gaps from 1.0mm down to 0.5mm are open, and the 0.4mm gaps is a little under half open, I'd call it a 6.4.

I've found that different colors of filament print differently, so you may want to create a different profile for each color you have.

Gap Test with loop