Prusa Mk3S, great print followed by disaster, what's wrong

[Bobslay]

Hi,

Can someone please share their opinion on the failed prints in the attached photos. I have spent hours tweaking z offset, temps and changed nozzle and cleaned the printer but I am still struggling. I got the successful phone stand you can see in the photos but for every one of those I'm getting 20 that don't even get started. I have tried with and without bed adhesion, I clean the bed with detergent before each print (I didn't on the two pics but the fail happened on a clean part of the bed).

I'm hoping that someone which much more experience than me will look at these and be able to give some advice as I am just constantly tweaking thigs and I think I am making things worse half the time.

Also, even though I have run the config several times and run the z-offset each time there appears to be more squish on the right side of plate than the left (that may give a clue as to what's wrong).

Thanks in advance

[curious aardvark]

what is your first layer speed ?
And DON'T ever use detergent to clean a printbed.
Always use either isopropyl alcohol or acetone.

I prefer acetone - but ipa is just as good.

Detergent will always leave a thin film behind, alcohol and acetone won't.
So that's probably part of the problem.

next - what speed are you using for the first layer ?
And you could do with the nozzle being a little closer to the bed.
Adjust it in 0.05mm increments.

Also what are your retraction settings.
try 3mm at 70mm/s
That gives really clean retractions for most direct drive setups.

Also what temps are you using ?
people often print pla too cool. 200c is pretty much the sweet spot with 65c for the printbed.
And don't mess about with it. changing temps mid print is not a good idea.
90% of my prints are at those temps.

Have you actually physically levelled the printbed ?
With the knobs ?
That's very important.
The autolevel stuff is all well and good (and unnecessary if the bed is flat and physically level) - but the bed needs to be physically level.

[Bobslay]

Hi,Thanks for taking the time for such a thorough response. I shall start working down that list immediately. Strangely, I used to use alcohol to clean the bed and someone on another forum , about 4 months ago, said to never use alcohol and always use detergent!I'll post back once I have been through everything you suggest.Thanks again

[curious aardvark]

detergent always leaves a very thin film behind, which will definitely effect your adhesion.

Alcohol or acetone will remove any organics (things with carbon based molecules) and totally evaporate, leaving a much cleaner and 'stickier' surface.

It does depend on what the print bed is made of whether you use acetone or ipa.

I mean all you need to do is to get a folded sheet of kitchen paper. Briefly upend the bottle so it dampens the paper. And give the bed a quick wipe.
It's so quick that the chances of it effecting even something soluble is minimal.

And you don't need to clean it very often.

In your case.
I'd wipe first with a water dampened sheet - to remove the residual detergent.
Then an alcohol wipe to remove any residual grease.

The little packets of glasses wipes or computer screen wipes are usually ipa. they work well and you can get them from buckstores/poundstores

And then physically level the bed.
Remove filament and heat the nozzle to 200c Before starting the level.

Always level with a cold bed and a hot nozzle.

I have tried heating both - but I've always had the best results with just a heated nozzle,
:-)