MK52 heated beds are designed by Prusa and made from thick PCB boards. PCB is an abbreviation of Printed Circuit Board, and it is the same technology being used in all electronic devices dressed with microprocessors, transistors, capacitors and resistors.
The substrate most commonly used in printed circuit boards is a glass
The MK52 beds are not scratch proof because they are not made to print nor do any other process on them. Magnetic structure of your MK52 bed lets you magnetically stick a sprint steel sheet on it to print on. These spring steel sheets are being manufactured by lots of different vendors. Some of them have fine smooth edges, some have more rough edges, however, regardless of the edge roughness of the steel sheets, if you stick the steel sheet on the magnetic heated bed and slide it back and forth you will end up with a scraped surface which might reveal the thin copper wiring beneath.
IMPORTANT There are two pivot pins on the top surface of your MK52 heat bed and a coherent top notch on your spring steel sheet. Please align the notch(es) of the steel sheet with the pins in question and slowly put down the steel sheet on the heated bed. And do the opposite when your print job finishes. Try not to slide your steel sheet over the surface of the heated bed.
If you follow the instructions your MK52 heated bed should serve you for many years.
As mentioned above, due to continuous missuse, copper wiring beneath might reveal in time. If this had happened to you, try applying a thin layer of nail polish to cover the revealed part or simply use a
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