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.
It has 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 the print was aborted.
- Restarted the same print job.
- 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 the bed remains flat and level, but the height is off. That is to say, the bed is flat and level before and after this occurs.
Please note: I have done over 100 successful prints, prior to this issue, so I do have some knowledge about levelling the bed. I am interested in what could cause such a large variation. Initially I thought it was temperature as I switched to ABS at the time, but it now varies from one print to the next.
The machine is a month old and rock solid. The Z-axis is the slowest moving axis, controlled by the limit switch only, hence my suspecting that is the cause.
I purchased a couple of spare Ender 3's and will update various parts in turn to see what the cause is. The metal trigger on my Z-limit switch seems a little floppy sideways, but I am also starting to suspect the bed springs have lost their springiness.
I have the removal bed version and also a borosilicate glass bed. The glass is perfectly flat and the standard removable is dipped ever so slightly in the middle, but the difference is huge when it goes wrong. As you can see from the photo the trench it digs is quite uniform depth. That's why I keep coming back to the Z-limit switch. I have a spare switch now so will try that next.