[Very bad quality infill]

It would be cool if this could be automated a bit...

I'm thinking something along the lines of a printer-calibration sheet (those that you scan in again, or pick the number in the software so that the colours are aligned).

Imagine asking the printer to print a set of cubes, say 8 by 8, and it automatically adjusts the speed in the one axis and the temperature in the other. Based on the results you can then choose the best combo. Since the temperature and print speeds will have to be adjusted, it would have to be a solution a bit more powerful than Cura. I imagine that it should be possible though... maybe someone smarter than me can come up with the GCODE.

[Very bad quality infill]

80mm/sec for infill and 50mm/sec for walls is a bad idea.  It has only been the default for a year or so and often these new settings end up going back to the old settings after a year or two of complaints.

I mean maybe 80/50 works fine on most printers as long as your layer height is thin enough.

Most likely your printer can't extrude as fast as it used to be able to due to a very thin layer of gunk in your nozzle.  You can burn that gunk out or soak it in acetone over night.  Or your white teflon isolator may have softened after lots of printing and now squeezes the filament causing much resistance.

Anyway what is your layer height?  80mm/sec is just too fast if you are at the default 210C and .2mm.  You can go that fast at .1mm but barely.

Here are my recommended top speeds for .2mm layers (twice as fast for .1mm layers):

20mm/sec at 200C

30mm/sec at 210C

40mm/sec at 225C

50mm/sec at 240C

The printer can do double these speeds but with huge difficulty and usually with a loss in part quality due to underextrusion. Different colors print best at quite different temperatures and due to imperfect temp sensors, some printers print 10C cool so use these values as an initial starting guideline and if you are still underextruding try raising the temp. But don't go over 240C with PLA.

If you hear the feeder stepper skip back (make that sound) then the pressure is too high.  That happens around 10 pounds (5kg) of force which is rather extreme.  You shouldn't need that kind of force but that would be completely expected at 80mm/sec .2mm layer height 210C nozzle temp.

 

Thanks for the detailed response. Do you have suggestions for temperature and speeds for ABS?

On another note: we are eagerly awaiting the upgrade kit for the Ultimaker 2 (to convert it to a 2+).

[Very bad quality infill]

and try a print with 24% infill, it looks less material, but the infill is printed in both directions on each layer.

 

Thanks for the suggestion. We usually left the print settings on the 20% defaults. The reason we switched to 25% is precisely because the algorithm works differently from thereon onwards. Be it as it may, both algorithms used to work flawlessly, and we could set the infill rate based on our requirements for structural strength, not to force a specific algorithm.

As in the reply to Nicolinux above, I have a suspicion that the nozzle or the feeder is damaged. I trust that if there was a flaw with Cura it would have been discovered and fixed by now.

Perhaps I should also try other slicers (it just always seem like such a schlep to get them working for the Ultimaker), as you suggest the algorithm could make such a huge difference - will keep you updated.

[Very bad quality infill]

This could be due to your slicing settings in Cura. Switch to the "Advanced" tab and set every speed to 0 except for the travel speed and bottom layer speed.

 

I'll definitely give this a try; the intent of course being to slow down the printer during infill and such.

The latest version of Cura gives you the option to copy the settings when you switch over from "quickprint" to "full settings". When I do this, the infill speed for example is set as 80mm/s. The print speed is 50mm/s (for normal quality). This reduction does not seem big enough to make such a huge impact, but it is worth a try.

After playing around a bit more over the weekend, I have a funny suspicion that the feeder stepper motor is skipping or something (motor problem, not with filament slipping or similar), or perhaps the nozzle has been damaged. I've already ordered a replacement nozzle.

[Very bad quality infill]

We've been having a problem with our Ultimaker 2. The print quality in general seems very good, but the infill is very bad. We've found by setting the flow-rate much higher (as much as 140%) we can mitigate the problem somewhat, but it negatively affects the rest of the print.

The images below are of models printed at normal quality (Cura), but infill set at 25%. We are using ABS.

I've tried to show the infill from the side to give an idea of how insufficient it is. Note, however, that the rest of the print is not bad at all.

Sometimes entire holes will fall in because of the lack of infill, as shown here.

We've tried many things already to fix this. I've used the "atomic method" to clean the nozzle; I've opened up the entire print head and cleaned it out (soaked it in acetone over the weekend). We've checked the feeder and Bowden tube.

Any advice on what I can investigate, or what could be the problem, would be greatly appreciated!