Temperature also plays an important role in print quality and is especially linked to print speed and layer height. As a general rule, if you start to slow your printing speed below 20mm per second, you should also reduce your printing temperature.
You may decide to print more slowly for a variety of reasons, such as printing a single small object or a part that's been tricky to print in the past. Most thermoplastic materials print perfectly well at temperatures lower than you'd normally use. Reducing the temperature also helps stop hot plastic from oozing out of the extruder nozzle, which can make a big difference in the quality of fine parts being printed slowly. You have more control of the plastic being extruded with such an approach. Also, you lower pressure in the extruder nozzle, which further improves print quality.
If you're getting lots of print failures when you print plates of multiple parts, you may have a small mechanical-alignment problem. Check your belts to see whether they're tight enough. Also check carriage speed. If you're moving the carriage too fast for the frame design of your 3D printer, try slowing it. If that change doesn't help, consider tweaking another Expert-mode setting in Slic3r: Avoid Crossing Perimeters. This option tries to move the print head around the outside of a printed layer instead of across the part to reach the other side of the build bed or other object. The setting extends the time required to print an object, but it also improves the quality and reliability of the print.
PLA prints at temperatures as low as 160 degrees C when you're printing parts slowly, which can produce less oozing and finer detail for smaller parts. You can still use a fan to force-cool the plastic layers, even at such low temperatures.
