Would 3D printing multiple copies at once saves time?
I am wondering - of course if the 3D printer's bed big enough - printing multiple copies of the same print could save me significant amount of time in a small production line, excluding minor wastage such as setup time, post-processing time, etc.
e.g. if my foo print takes 10 hours, printing 2x copies at the same time would take 2x times more, increasing linearly or it would be significantly less?
This depends. Are you printing everything from one extruder, or do you have multiple extruders working in parallel?
Actually no. It will take slightly more for each addition. You also then have the point of failure, where one gets knocked off and ruins all the prints.
The fastest way to print multiple objects is one at a time. In fact slic3r lets you do just that with their sequential printing feature.
The reason is, the time it takes to lift 0.5mm, travel the few MM over to the next object, lower the 0.5mm back down.. Repeat for inner shells, outer shells, infill.. all add time. Doesn't seem like much till you do it 14,000 times.
In the case of your example, it would be negligible. In more complicated or well spaced prints its another story.
For extra extra fast, look into loss PLA casting...
What does "loss PLA casting" have to do with this? How does it allow you to speed things up?
You might add to your answer that the user is pretty much responsible for verifiying that the required X-Y clearance for the extruder head after a few objects have been printed is set properly. And of course for those not using slic3r, the advantage of printing everything at once is that we can walk away from the setup and come back when everything is done :-)
That's not the right terminology then. "Lost PLA casting" refers to a process where a PLA print is encased in plaster, then burned/melted out, and then molten metal poured into the void left. The mold is then broken, and a metal part extracted. This doesn't help for making a bunch of parts, since both the master part and mold are destroyed. The idea to look in to (silicone) mold making and casting in resin is not a bad suggestion though, but not really related to the question (and there is no indication OP is looking to print *that* many copies of this part).
If other processes are acceptable, "Cast Urethane Molding" would also be a really good option. It's a good option for the 20-1000 part numbers. Cheaper than injection molding or investment casting for those quantities. Faster and cheaper by far compared to 3D printing. (suggested by Tom, but didn't have the terms explicit stated)