Can't print holes on first layer

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Here we go again, another first layer problem thread. I really thought I had this sussed ages ago but it's come back to haunt me.

So I do a manual bed mesh leveling routine (9 points) using a piece of paper (0.12mm thick) as a feeler gauge and save the settings. I have LCD bed leveling enabled in the firmware and save the settings, so I assume the next G28 called before I begin printing won't cancel the saved mesh. I'm happy to be corrected if I have that wrong.

So I do a test cube and everything works great, it's dimensionally excellent and bed adherence is great but then when I do a print with holes in it the nozzle rips their outlines up and drags them all over the place. The rest of the print works fine but the hole detail is butchered almost every time. If the print has no surface detail (like holes) the print works great and I don't have any problems.

Before each print I like to squirt about 20mm of filament through the nozzle and ensure it's flowing well and falling in a straight line out of the nozzle, then I have a clean routine which extrudes a bit more before each print.

Here's a bit more info
Nozzle - 0.4 mm
Layer height - 0.3mm
First layer height - 0.2mm
First layer print speed - 23mm/s (was 30 but I've slowed it down twice)
Slicer - Cura
Printing surface - anycubic ultrabase cleaned with alcohol.
Filament - EDA PLA
Bed temp - 60
Ext. temp - 200

If I print a brim to gauge the layer height (which I have been doing) the brim is coning out at 0.35mm thick when measured at multiple sample points so my bed seems very level. I'm not sure why it's coming out at 0.35mm when I have the first layer set at 0.3mm either, is it a z offset error that I need to compensate for and is 0.3 mm too high for the first layer?


I'm almost certain it would be OK if Cura drew lines from the edges of the print to support the holes before it printed the outlines of the holes in the middle of nowhere but my other printers seem to to handle it OK so maybe that's a moot point.

Is this a Z offset problem or is it likely to be something else?

Edited 2 time(s). Last edit at 02/16/2019 09:49PM by Shreks donkey.

Quote
Shreks donkey

I have LCD bed leveling enabled in the firmware and save the settings, so I assume the next G28 called before I begin printing won't cancel the saved mesh. I'm happy to be corrected if I have that wrong.

In my testing any G28 or G29 Will disable Automatic bed leveling.
After the Last G28 or G29 line in your startup G-Code should be M420 S1

G92 E0 ;reset extruder length
M420 S1   ; Bed Leveling On
M420 Z2   ; Bed Level Z Height

Quote
Shreks donkey

Before each print I like to squirt about 20mm of filament through the nozzle and ensure it's flowing well and falling in a straight line out of the nozzle,


Is this a Z offset problem or is it likely to be something else?

I do the same, and include a two lap skirt as to quickly adjust the Z-Axis baby steps by sight to that perfect height.

If you do not have Baby steps it merely allow you to nudge the nozzle into place without changing the recorded coordinates.

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Computer Programmer / Electronics Technician

Thanks for the reply @Roberts_Clif, I'll revise my start code tomorrow when I'm not as intoxicated and see how it turns out.

Does 0.35mm seem like a good first layer height for a 0.4mm nozzle printing PLA?

I'd normally run it bit lower for a 0.4mm nozzle but the brim looked excellent and was almost that exact thickness all around, although I'm only measuring with verniers so they could be a bit off.

with a .4mm nozzle you are allowed up to 80% of the diameter for layer height
0.4mm * 80% = .32mm max layer height.

I make all my measurements with digital Calipers.
I guess in my opinion that is too thick. I have printed up to .3 layer height with a .4 nozzle though get the best results printing .28 layer heights an lower.

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Computer Programmer / Electronics Technician

I'm using digital calipers too.

0.35mm really did seem a bit much to me too, I'm used to just going by intuition and it just looked a bit high when it did the cleaning run.

Thanks for the feedback it's always good to get another opinion/perspective , I'll adjust my offset and make sure I'm not cancelling the mesh leveling and run a few tests tomorrow.

This is all sorted now, the first layer is as perfect as I've ever seen it and the outline for the holes are staying where they are printed. I've done a few single layer level test prints and it's measuring consistently 0.3mm everywhere, which is awesome because my bed has some serious distortion in it.

Thanks for the assistance @Roberts_Clif, I really appreciate you taking the time to set me on the right track.

I'm considering removing the springs from under the bed and replacing them with spacers now I've got it functioning properly.