Infill getting sparse at low layer heights

I'm having a problem with infill when I try to dial down my layer height. I generally run with 0.3mm layers at 130 mm/sec infill, 54mm/sec perimeters and achieve good results. Firmware is Marlin, and gcode generator is Skeinforge-40. Now I'm trying to go down to 0.2 mm layer height, but my infill is getting really sparse. Here's an example:



Adjusting the infill width over thickness ratio doesn't seem to help at all with the infill, but it sure does affect the solid layers (not to mention the printing time):



I also tried to slowing down to 50 mm/sec for infill and perimeters, to no effect. It almost seems like the problem may be unnecessary reversal at the start and end of many of the infill lines that get drawn, which causes the filament not to get pushed out enough once it needs to extrude again. I printed another cube at 0.3 mm layer height and these same reversals are present, but the problem didn't manifest itself, presumably due to the increased flow for the taller layers being less affected by the reversal. I tried reducing my retraction distance from 1.5 mm to 0.75 mm, with no effect.

Anybody know how to fix this?

I find for small layer heights you need to lower your speed.

Or

Turn on hexagon or rectangular or round infill as they all make for shorter/slower moves.

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Well, that helped a lot. Thanks!

There is a maximum amount you can stretch filament before it starts to snap. If you make the layers too thin for the nozzle aperture that is what happens. To get round it you have to increase the W/T. You don't want W to be much less than the nozzle aperture so if you have say a 0.4mm nozzle and want 0.2mm layers W/T needs to be 2 or more.

The other thing to remember is you need to increase the number of solid layers. If you use 3 with 0.3mm layers then you need 4 or 5 for 0.2mm layers.

Edited 1 time(s). Last edit at 11/06/2011 01:01PM by nophead.

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In the end, I just started using Slic3r and it made everything better. I've now printed with 0.08mm layer heights.

I'm having the same problem with PLA. How did you get rid of it?
The strange thing is that with ABS everything works perfectly. But as soon as I'm switching to PLA there's just a big mess in my infill section (tried temperature between 175 and 210... nothing worked) I got even worse results with coloured PLA...

Thanks a lot for your hint to use slic3r! It's a reeally great software=)

thanks and have a nice weekend

I just tried Slic3r and I found that it can't slice some files that Skeinforge can. A good example is the x-end-motor.stl file that comes with the most recent Master release of Prusa Mendel in Github.