Slic3r : Increasing layer height increase print time  

Re: Slic3r : Increasing layer height increase print time

Without the STL file it's hard to tell.
I suspect limitations in the maximum flow rate and geometry change due to the layer change.
For example if your settings for 0.4 nozzle, 0.2 layer height have speeds which are already at the maximum flow rate then it will not print significantly faster if you choose 0.3 layer height.
In regards to geometry it can happen that more layers are being considered top/bottom layers. The speed for those is usually slower so you don't have fast printing middle-infill fast printing layers anymore.
But again this question can be answered in detail only if you provide the STL file and the used settings, so everybody can reproduce it.

Re: Slic3r : Increasing layer height increase print time

It's not a bug, it's a feature! Seriously. There's a lot more than just the size of the nozzle and layer heights that goes into determining your print times. The E3D V6 hotend has a maximum volumetric speed (MVS) of something close to 15mm^3/s. That's how fast it can melt and move plastic through the nozzle. This means that the combination of your extrusion width, layer height and speed can't exceed 15mm^3/s. MVS is calculated as:

MVS = Extrusion Width X Layer Height X Speed

This means you can calculate the maximum speed at which you can print as:

Speed = MVS/(Extrusion Width X Layer Height)

With smaller nozzles, the printer hardware limit of ~200mm/s kicks in before this is an issue, but at 0.60mm, you start hitting limits. I did a quick calc, and with 120% extrusion width (0.72mm) and 0.20mm layer heights, your speeds are limited to close to 80mm/s with a 0.60mm nozzle. Increase that layer height to 0.40mm and your maximum safe speed is closer to 40mm/s. The feature in Slic3rPE is the Max Volumetric Speed (MVS) setting available in Printer and Filament settings. Prusa defaults MVS to 15 for PLA, 8 for PETG. In practice, the E3D V6 is happiest around 11.5mm^3/s. Slic3rPE will use up to the speeds you specify so long as MVS is not exceeded. If it is, it will start slowing the print down. You can see this in Preview mode if you view speeds.

Whether this makes your print finish faster or slower depends entirely on the model. Your choice of material may also impact it. If you can save printing perimeters, there's a good chance a larger nozzle will speed things up. If using the same number of perimeters, it's going to depend on how often your nozzle would otherwise be moving. On a part with short walls or not much infill, it might be faster. On larger parts or with lots of infill, it might be slower. If you care to provide a link to the STL you're printing, I'd be happy to give it a look.