Mendel User Manual: Bed
If the bed of your RepRap machine isn't maintained flat and parallel with the movement of the extrude head, it is very hard to get good quality parts. This section tells you how to get the bed flat, and how to keep it that way.
Getting the Bed Flat
Keeping the Bed Flat
This video shows how to prepare a tray for RepRap printing on a heated bed and to maintain its flatness. The blue tape on the tray is Scotch painter's masking tape 2090, which can be obtained at most hardware shops.