We have an issue when trying to calibrate the bed. We removed the print sticker and any glue residue but when trying to calibrate the middle part of bed seems higher than both corners.Is it possible that the bed is has a bump in the middle?
pls see link below
I would say that it is probably the leveling screws, there is no room for the glass bed to expand when heating up.
I drilled out the M6 screw holes on my printer, but a alternate solution that some of the guys here has done, is to replace the M6 screws for M4 ones of the corresponding length. You may need some bigger washers though.
This way the plate has enough room to expand and you won't void any warranty on your printer.
Thanks for the advice,will try