question about the quality of the Um3 output.

[Jini 0]

I think the bed leveling is okay. 

But the output is distorted at certain coordinates. 

I don't know the cause. 

 

[gr5 2,172]

Leveling looks good.  That's most likely different things on your bed.  For example, if you want it smoother than that then don't use gluestick.  Or if you do, wipe it with a wet tissue to spread it much thinner.  If there is no glue stick on your bed then it's probably oils from your fingers or maybe some dripped off the gantry.  Or if you washed the glass recently you may have left some soap behind.  You have to clean it really well if you want a consistent bottom.  

 

I like to wash with soap and water and then dry it with a paper towel and then wash it again with glass cleaner (Windex).  But some say Windex leaves behind a barrier layer behind and PLA won't stick to it but I wouldn't know because then I put a very thin layer of PVA on top of that.

[geert_2 557]

I also think your bed leveling is good, but bed bonding needs improvement. Which methods did you use for cleaning the glass, and for bonding, if any?

 

Usually I clean the glass with isopropyl alcohol. And then I clean again several times with pure warm tap water; no soaps, no degreaser, no solvents, no other cleaning aids. Soap reduces bonding, and some solvents might leave traces of oils or other stuff if they are cheap commercial grades and not very pure.

 

Then for printing PLA I wipe the glass with a tissue moistened with salt water: gently wipe while it is drying, so it leaves a very thin mist of salt stuck to the glass. This improves bonding for most brands of PLA (but not for other materials). I am not sure why it works for PLA, but it does; probably because salt increases surface tension of the glass? (Contrary to soap and oils which reduce surface tension and reduce bonding. That is how I came upon the idea to search for the inverse: something that increases surface tension, which was salt.)

 

This "salt method" gives good bonding on a heated bed to 60°C for PLA, but after cooling down models come off by themselves without effort; there is no bonding at all on a cold plate.