I haven’t leveled my bed in a while. After encountering some adhesion issues I decided to do it again. But for some reason the indicator jumps around way too much every time the nozzle touches the bed. Normally it should just settle down if I don’t touch the knobs. There might have been a FW update between now and my last bed leveling so I don’t know if that’s the reason.
Edit: Nevermind it was some residue on the tip that didn’t come off with the brass brush. Used something harder to clean the tip and it now calibrates.
I always do a cold pull before calibration. Not much additional work as I usually only do calibration when switching hotends and for that I have to remove the filament anyways.
I have noticed similar behavior of bed levelling after I upgraded FW to the latest version. Before it was either working OK or not at all, latter if poor electrical contact has been present between nozzle tip and contact spots on bed. Maybe this is something to do with FW?
I decided to upgrade because of PID tuning available on the latest one and thought my new hotends will benefit from that. At the end it was “jumpy” levelling and erratic at the end too. So I did manual tuning of bed level and Z-offset to have first layer in place.
Funny but hotend alignment part of calibration worked really well - transition lines from one nozzle to the other are not visible at all. Before upgrading FW I had severe offset along X axis (close to 0.08mm) and less pronounced (0.05mm) on Y. Now calibration is within 0.02mm - nothing better to desire.
It is possible that contact of hotend PCB into print head is not secure well enough but normally this fault should affect only right extruder being adjusted. I had problems with the right one, left was more stable in bed level readings however not as steady as with old hotends and FW.
I’ve gotten into the habit of unloading the filament before doing any bed leveling. Some filaments ooze more than others. You can probably get away with leaving standard PLA but I print with nylon a lot and the hot end will never stop oozing with this stuff. You could probably say the same with most silky PLA. It likes to puff up when it melts and never seems to stop coming out of the nozzle.
I have finally yet almost accidentally discovered reason for inability to make good bed leveling and right extruder Z-alignment with jumpy indication involved. Problem for my SJ1 was too large play in linear carriages, especially the right one. I just have attached a little video on the left carriage.
I had the whole X-rail replaced under warranty few month ago because of the same reason but I did not assume it will fall into the same condition that soon again.
As I had already X-rail of Hiwin make by me, I replaced Snapmaker one with that. Result was surprisingly good - bed alignment and especially Z-alignment of right extruder was rock solid, indicator remained at the same position every time nozzle was touching contact spot on table. Needless to admit - also first layer significantly benefited from implementation of Hiwin rail - is is now very uniform and consistent around the whole surface of table.