Really interesting post; thanks for the superb detail. I too have been 3DPrinting for nearly 10 years, and have just recently upgraded to a shiny new K2 Plus combo (from Prusa). I’m having what sounds like the same first layer too close issue that you describe, but only intermittently. It presented initially only with ABS (I print mostly ABS, with some PLA and PETG). But yesterday it did the same thing with PLA, so it’s not exclusively high temp, as you describe. It seems to happen about 40% of the time, and so far I can’t find a correlation with any other factors. So when I send a print (using C.P.6.0.4) it’s a lottery as to whether it’ll print perfectly (it does print ABS extremely well if the first layer goes down OK) or errors out with the “doesn’t seem to be extruding” error you get when you’re too close and it can’t extrude properly. I’m thinking it’s something to do with the firmware retaining the Z Offset value after calibration (or not, in some cases). Can anyone else throw any light on this issue?
In my case, the inconsistent first layer height was due to the prtouch sensor inaccuracy. I say this because the problem disappeared as soon as I started using a Cartographer sensor instead of the stock strain gauge sensor.
It might help to tighten every screw on your toolhead and rails, including the screws holding the strain gauge. Additionally, you could order a new strain gauge - they’re quite cheap, and replacing it while tightening the screws might be a good idea because it is very inconvenient to have to disassemble the toolhead.
I was having the same issues but i have 2 k2 printers that i got the same day from different stores. I notice that one printed a little different. One has the bambu quality and the other was off. If i wouldn’t had the 2 printers i don’t think i would found the issue. Fist i notice the bed shaking more that the other after every z drop. I ran the tower test and i can really see the z drop shaking. I pushed down on the beds and one good one has more rigid springs so i was like maybe they put the wrong ones after going back and trying to tighten the screws i notice i can pick the bed and on the other machine the bed is solid. The poles were the bed attached to are broken but because the bed is so heavy i was able to get decent prints. But if wouldn’t have the other printer it would it take me a wild to find out. Check your bed because i found out that is common issue. Im still waiting for parts.
