Optimise print time by changing infill density?

Hi,

I noticed something today while changing the infill density in Cura.

The total time that was computed (by Cura) for the print, seemed to be at a minimum when the infill density was at 50%.

Actually, I didn't try very low fill densities, e.g. 5%, as they may be faster (but probably unusable for most objects), but I tried a range from 20% to 70% and 50% seemed to give the lowest time, i.e 2 hours 40 (for 50% fill) instead of 3 hours 50 mins for 30% fill.

In this case I need the object to be fairly strong, so 50% fill isn't a problem.

I realise that its going to cost more in filament, but it really only amounts to a few cents, so it seems a no brainer to use whatever infill gives the best speed, unless there is a specific requirement for either a very strong object or a very light one.

PS. I've not actually timed the prints at different densities, I'm just relying on what Cura displayed, So this could be a complete red herring if Cura is know for getting the times distinctly wrong

Edited 1 time(s). Last edit at 01/02/2014 07:55PM by rogerclark.

There has to be an error somewhere. At the same feed rate, there is absolutely no way 50% would take less time than 20%.

@Dirty Steve

I did the print that Cura computed would take 2 hour 43 and it took about 3 hours 20 mins.

I checked again what time Cura thought it should take at 50% and also at 40% 30% and 20%

The computed time for 40% was a lot higher than for 50%
And computed time for 30% was still slightly higher than for 50%

But 20% was less

Its hard to know without actually printing the same model at different densities, whether Cura's calculations are vaguely correct.
i.e I know the print took around 25% longer than the computer time, but it could be that all prints take 25% longer.

I presumed that perhaps the difference between 30 or 40 and for 50% was the fill pattern, but I guess this is probably a question for the Cura people.

I use KISSlicer, it's time estimates are pretty accurate, even for 96 hr prints. I run my machine with MACH3, but check my gcode with Repetier which also give a pretty accurate time estimate.

@Dirty Steve

I'd like to use KISSlicer but have never managed to work out the settings to get a decent print on my MendelMax :-(

I had mainly been using Slic3r, but recently started to use Cura as Slic3r can't slice some models. I have tried KISSlicer a few times, but have not had the time to do multiple test prints in order to get the settings correct, and the KISSSlicer defaults don't work at all for me, the printer didn't seem to extrude at all :-(