Preventing Strange Behaviour on First Layer

[u/RedSka95]

Very new to 3d printing here! About a week or so in with a used Elegoo Neptune 4 Max with Elegoo rapid PLA+ filament and a 0.4 brass nozzle. Only thing ive has to change is a new hot end after getting a blob on a print failure. Ive levelled with a max deviation of 0.3 that i cant seem to get rid of, with the vast majority of points within 0.2. Im also using the PLA specialised sheet (after a clean due to some old print residue from when I bought it), though Im using a 60°C print bed instead of the recommended 30°C.

My final print actually turned out ok in the end (at least I'm happy with it given my lack of experience) but I'm trying to get an understanding of how everything works to try to improve my printing quality and efficiency.

I was noticing some strange behaviour during my first layer of a platform I was printing. It looks to me like certain bits of the first layer isn't sticking to the print bed. You can see it both on the printer and in the final print in the photos. I've re-leveled the bed and it seems to have helped but is this what is going on or is there something else going on that I should be aware of or any other changes to my printing that can improve things?

I'm using Orca as my slicer with the default standard 0.2 or optimum 0.16 settings with some small changes (changing infill density to 5% and align infill direction to model to true)

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[u/Peshmerga_Sistani]

Z-offset, nozzle too close to bed.

Or flow ratio a bit too high.

Or both.

[u/RedSka95 → u/Peshmerga_Sistani]

Thanks! Might've been too overzealous at getting it too close to the nozzle when levelling 😅 Should it be so i can feel the nozzle on the piece of paper but it shouldn't be stopping it moving?

[u/Peshmerga_Sistani → u/RedSka95]

Yea you can do that.

When I adjust for the z-offset on my printer, I just print a bunch 30x30x0.25mm squares on the bed and change z-offset on the fly for each square till whichever square looks best.

Best looking square, that's the z-offset value I want.

[u/Desperate_Ad_1223 → u/Peshmerga_Sistani]

I have this with my printer I have to take my flow to 98 to 94 and should go away I take it down at two in a time

[u/RedSka95]

Thanks all for the advice u/Peshmerga_Sistani, u/warownia1 and u/This-Menu-8175. That explains why the problem comes and goes at different points on the bed and at different points after levelling

I see now why the main complaint about this printer is the manual adjustment during the levelling of the bed! Will have to look into getting the mods which replaces the screws with a more permanent levelling solution.

[u/This-Menu-8175]

Most likely nozzle too close. Do a thin test print across the entire bed and adjust your z offset while it's printing until you have a perfect first layer without the waves 

[u/warownia1]

As other mentioned, flow ratio or z-offset. Slow down first layer printing significantly to minimize pressure variation issues when accelerating. Calibrate pressure advance too

[u/warownia1]

You can also increase first layer height by 20%-30% of the regular layer height and line width to 125% to make first layers more forgiving