Having a level build platform is crucial to successful prints. This allows the first layer to be applied evenly and properly adhere to the build plate. having the nozzle too far from the build plate can cause the print to warp or even dislodge while printing. If your nozzle is too close to the build surface, the filament will be squished against the bed and this could either jam the extruder nozzle or complicate the print removal process.
First off; when leveling the build platform you will have to heat the bed to it’s printing temperature. The thickness of an aluminum bed will vary greatly depending at what temperature it is in. To level your bed properly, the same temperature at the time of printing is needed.
Place a sheet of paper on the platform, you will want the nozzle to touch the paper and still be able to move it freely with a bit of drag.
Move the extruder to each corner of the platform making sure that the amount of drag is constant on each corner, adjust the screws on the corners accordingly.
The center part of the build plate is the most important to have leveled properly as this is the location where you will most often be printing at.
Make sure to double check all positions once you are done leveling all four corners.
Perform this routine every time a physical parameter is changed on the printer, or if the printer is moved to another location. Once you get the hang of it, it will be very quick to level and you will not need to resort to any auto calibration features on your printer.