Newbie: Prints GOOD, except first 3-4 layers??  

Re: Newbie: Prints GOOD, except first 3-4 layers??

[...] I started with height of 0.3, with first layer 0.35... I have since changed this to 0.28 and 0.38
I suspect this is your problem. Assuming you're using the default 0.40mm nozzle:

These are general guidelines, and don't mean you can't vary from them if you want to experiment, but I'd suggest getting some good consistent results first before trying anything more aggressive.

Re: Newbie: Prints GOOD, except first 3-4 layers??

THANKS!
I took the defaults and lowered them.
so the Height was 0.3 and I changed it down to 0.28. if I read your advice correctly, I can leave this value as is.
the First Layer Height was 0.35, and I changed it UP to 0.37 thinking thicker (for the first layer) was better... sounds like you're suggesting that is not necessarily the case... I will try a SQUISHED layer later (in the region of 0.2 for the first layer height) and come back

Could this be my Z-offset is still not right?? the test looked good, and the rest of the CUBE looks good so I assumed it was ok... but I can try lowering this too (I find changing this value hard as my eyes just aren't what they used to be <LOL>)

Re: Newbie: Prints GOOD, except first 3-4 layers??

THANKS!
I took the defaults and lowered them.
so the Height was 0.3 and I changed it down to 0.28. if I read your advice correctly, I can leave this value as is.
the First Layer Height was 0.35, and I changed it UP to 0.37 thinking thicker (for the first layer) was better... sounds like you're suggesting that is not necessarily the case... I will try a SQUISHED layer later (in the region of 0.2 for the first layer height) and come backTry 0.20mm for a 1st layer. Get that working, then experiment. My experience has been that an even 1st layer is most critical and even heating is a big part of that. Other printers with poor surfaces tended to favor a higher layer height for the 1st layer to help mask bed imperfections. With the Mk3, you don't need to worry about that aspect, so you want thin and even. I use a 0.20mm layer height for all my prints using nozzles over 0.25mm.

Could this be my Z-offset is still not right?? the test looked good, and the rest of the CUBE looks good so I assumed it was ok... but I can try lowering this too (I find changing this value hard as my eyes just aren't what they used to be <LOL>)

Very possibly. The on-board Live-Z calibration routine can be a bit difficult to interpret. I recommend Jeff Jordan's excellent "Life Adjust" routine. It is much easier to use and understand.

Starting high (less negative - maybe raise it up 0.2 or so from current position) and working your way down (more negative). Initially, lines may not adhere at all. Keep going lower in large increments (0.10mm) until lines start to stick. Go lower in smaller increments (0.02mm) until you get good, even 1st layer lines with no gaps between extrusions.

When you've got your Live-Z setting adjusted properly, you should not be able to move single-line extrusions with a gentle poke. They should adhere enough to require a bit of a push to pop off.

Good luck with it!

Re: Newbie: Prints GOOD, except first 3-4 layers??

THANKS for the guidance. I think I am making success.
I have followed your recommendation of Jeff Jordan's approach... and revised the Z offset from -0.4 to -0.835. I am not sure I have finished but I can see the difference.

that coupled with lower layer height has resulted in the third CUBE... which at this point feels like success. the top surface isn't what I want, but that can come next.

New Layer Height = 0.25
New First Layer Height = 0.2

THANKS for the help

Re: Newbie: Prints GOOD, except first 3-4 layers??

You might try dropping your extrusion multiplier a bit and see if the top evens out. Glad it's getting better.

Re: Newbie: Prints GOOD, except first 3-4 layers??

From my experience new users need only to get the live z height right and use the defaults for a perfectly accpetable prints. (Caveat - clean build plate and using the Prusa supplied filament.)

Re: Newbie: Prints GOOD, except first 3-4 layers??

thanks john.h68
I am pretty pleased with how my Z-calibration sheets are now looking --- though in the process of getting things better I monkey'd with the speed and the like.

I think I need to take your advice and go back to zero ---- ummm - when I have replaced the ptfe tubing (see my other post) since I think the speed, retraction etc settings are what caused my ptfe issue.

thanks again for the help