HP 815MFP - Manual (Page 33)

hp designjet 815mfp & scanner 4200 27
10. Dry the platen and rollers completely using a separate clean,
dry lint-free cloth.
11. Replace the pressure platen.
Lift the pressure platen into its original position.
Press down on the metal safety buttons to let the two sliders
move back and lock the platen into place.
12. Close the scanner cover.
Now continue with the camera alignment and calibration
procedure.
camera alignment and calibration
Before you align and calibrate the cameras, make sure that you
have gone through the first process in scanner maintenance:
cleaning the scan area. An unclean scanning area will give you
imprecise calibration results.
Camera alignment and calibration is a fully automatic process that
you only need to activate through the wizard and then leave to run
on its own.