Auto Bed leveling?

Hello, I really appreciate all the help I've gotten so far, and I apologize if I've asked too many questions, but I had one last one. How exactly does the auto bed leveling work? The printer I'm looking at is an i3 with auto bed leveling as an add on for $40. I saw a video, and it showed the print head going to all 4 corners, but I don't understand. Does it tell you which corner to screw in more/less or does it do it automatically or what? I've only ever owned a printrbot simple, so I'm very unfamiliar with auto bed leveling, but it's definitely something I want because I could never get my printer perfectly leveled for bigger prints. It would always come up before the print was done because it wasn't level. Thank you for any help!

Edited 1 time(s). Last edit at 04/12/2015 12:35AM by fatesalign.

any ideas?

Auto bed leveling/zeroing measures the location and tilt of the bed, then the firmware compensates for the tilt by running the Z axis screws continuously as the machine prints. It essentially tilts the print in software to match the tilt of the bed.

Quote
the_digital_dentist
Auto bed leveling/zeroing measures the location and tilt of the bed, then the firmware compensates for the tilt by running the Z axis screws continuously as the machine prints. It essentially tilts the print in software to match the tilt of the bed.

That makes sense. Thank you very much!

I opted for a different approach - I took time to ensure that my machine was totally level and not leaning using a set square etc. I then fixed the heat bed and use a hall effect endstop on the Z Axis which can be adjusted by a potentiometer for micro adjustments. Works a treat and I haven't had to level the bed for ages,.