Many of the Z-603S printers come with print beds that are not flat. This is a problem, as it makes it nearly impossible to get large prints to be stuck down evenly to the printing surface.

There are a few solutions for this:

1. Ask JGAurora for a non-warped bed (good luck…), or buy a new bed from their Amazon store here.
2. Put up with it, and use the flattest region on the bed you can find - giving up on any hope of printing large prints
3. Buy a new perfectly flat custom cast aluminium print bed
4. Install a custom firmware on your printer, and go through the mesh bed levelling routine to compensate for the uneven surface.
5. Modify your printer with an automatic bed levelling probe.