I'd like to print a cylinder, 50 mm diameter, 200 mm long, with 1.5 mm diameter holes tightly fit like this:
The holes go all the way through from top to bottom.
I am using a Prusa i3 MK3S. With 0.1 mm detail and 20 % infill, printing one cylinder is going to take 5 days and 5 hours. I need at least five cylinders.
You are printing a model that has a highly complex structure there, with about 650ish holes, assuming there is space for about 2 perimeters between each hole.
Taking my standard 0.3 mm layer height and 0.4 mm nozzle using a 0.45 mm wide line, I sliced a 10mm high slice of the model for a first estimate of the expected print time - and came out with 2:21 hours. That means the expected print time with 0.3 mm layer height is in the area of 47 hours - or just about 2 days.
As a result, 5 days and 5 hours are in the order I'd expect from a 0.1 mm layer height print for the same nozzle, in fact, your settings seem to have a faster print speed than I do work with.
In general, I don't think this model is good for FDM printing at all, due to many non-fully formed lines inside the model (yellow) and the red perimeters being a very dense pattern.
You might get a faster speed with a high-flow solution, for example, using a long melt zone (volcano-style) or an even higher flow core-heating 3DSolex nozzle. The latter originally only comes in 0.6 mm and up, also mandating fewer holes, but in late 2021 CHT nozzles in 0.4 mm came to the market. This could drop print time some, but it'd still be a several days print job.
Besides increasing layer height to drop printing time by the same factor, reducing the number of holes and as a result, spacing them further apart not only can increase the print speed but also make the print form more reliable.
Another alternative would be to alter the pattern from a circle to a hexagonal pattern: by using hexagons, the resulting pattern does not contain thin walls and might print much faster - depending on hole size, you might experience a drop by a factor of 2!
Going from FDM printing to a system such as SLS might be faster and more reliable while SLA/DLP would make this print not only fast and reliable but also trivial - if one can get a 200 mm high SLA/DLP printer, all three models should be able to be printed in one go at the same time!
Late to the party, but for other people that stumble here with a similar problem i've seen a lot of people use a 0 top layers, 0 bottom layers settings to expose infill structure. That with a suitable infill pattern might give you a different slicing that might be faster to print.
Holes, circles, and curves are slow to print, and get slower as the number of wall segments increase.
Ideally you'd use square holes, but hexagonal-sided ones would be a fair compromise too.
Your slicer should be able to give a breakdown on the times for each kind of line in the part. Check and see how much of the time is spent on "moves".
Is there a reason for using all these little holes? Fewer, larger holes will provide better airflow and require less printing, up to the ultimate of one single large hole, where you're essentially printing a pipe/tube.
Do you need the holes to go right-through? Printing a big "cup" with holes across the floor, and separately a "lid" then gluing them together would be quicker and you have one large hole in the middle. If this idea works, you might prefer to just buy plastic pipe of a suitable size, and print only endcaps.
Additionally, if you're printing 5 cylinders because you need a metre total length, then printing two endcaps for a 1 metre piece of plastic PVC pipe should take a couple of hours at most. And it will save you a lot of filament.
