I had a couple of recent nozzle/bed crashes, so I now frequently do a manual bed levelling. I do these while the bed is heated to allow for expansion.
Today i found, after levelling, a subsequent print could vary from having too much clearance (paper moves very freely) to less than no clearance (which left deep grooves in the bed as per the photo).
What are the possible causes? Is it just a dodgy Z-limit switch or something else? What solutions are available and at what cost? Obviously an ABL seems essential now, but requires a lot of hardware and setup.
Just happened again so here are some more details.
Printing PLA this time. - Preheated bed. - Levelled bed all over and got a very good raft. - Print failed later so aborted. - Restarted the same print. - Nozzle gouged out a uniform depth trench around print perimeter.
The uniform depth of the gouge indicates a problem related to Z-axis only as bed remains flat and level, but height is out.