First Layer inconsistent when there is a Z movement.  

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Joãozinho
(@joaozinho)
Active Member

Hi guys!

I'm having sort of some issues whenever i have some Z movement on the first layer. 

To be more specific, i'm printing some square with round edges shape and it has some holes on the middle. This means that the printer will start by laying the perimeters of edges and holes and then start filling the surface. The final product reflects the following:

Take by example some part of that shape that the extruder fills without lifting. That filament gets squished in a way. then it finds those holes and has to lift somewhere to fill another area. After this procedure, the filament gets squished in a different way than previous. and this repeats for all the times it has to do some Z movement. I have the Z pretty low as i use Prusament PETG on PEI sheet that is smooth and i love that perfect finish where all the lines from the filament are almost indistinguishable. But since that Z movement produces different results, the finishing is inconsistent across the shape. And this also does not mean that the first "touchdown" is perfect and the others are not. Sometimes the gaps between the holes get better finishing than other areas and filling never starts from that point. 

On a tray i do 4 of these shapes and in different areas of the tray. The odd effect is found across all shapes, regardless of where they are found on the tray.

I have re-done the initial calibration and things look the same ever since this started to happen. It's like everytime Z moves it will not return to the same height as before.

Any thoughts on why this may happen? 

Note: i have also used prusament PLA before and this happens the same. 

Posted : 02/03/2021 6:25 am
Dan Rogers
(@dan-rogers)
Honorable Member

pictures?

 

Posted : 02/03/2021 2:44 pm
Joãozinho
(@joaozinho)
Active Member

@dan-rogers

Its not very easy to snap but there it is. thanks

Posted : 02/03/2021 3:19 pm
Dan Rogers
(@dan-rogers)
Honorable Member

Gotcha.  The first layer is a little bit inconsistent - so I'd recommend cleaning the bed with dish soap and dry thoroughly, and then do a Live Z as your print starts to see if you can get better thread to thread adhesion.  The perimeters on the holes are missing the overlap that I would expect to see with the rectilinear infill.  There is a setting that lets you increase that overlap - you'll find it on the Advanced tab (enable advance settings view) - the default overlap I am seeing for generic PLA is 25% perimeter overlap.  

You could also probably achieve a similar "more integration" outcome by increasing your extruder multiplier by .1

 

Posted : 02/03/2021 3:58 pm
Joãozinho
(@joaozinho)
Active Member

@dan-rogers

Thanks for the reply roger! Actually i have the multiplier on 0.98 as i was feeling that some scarring and excess of material was being deposited on the end of the layer. Also my calibration cubes were x2cm y2cm and z2.02

last ones i did were already ok as some extruder stepping was also corrected. The dish soap procedure is done regularly. The lack of overlap does not bother me much i just dont understand this pattern. You are looking at lack of grip? I think i have plenty grip in my way of seeing things just did rule that out on my approach to the problem. Will try to get the multiplier back to 1 next print. Anyways there are some “batches” that come out better than others. Without changing nothing. So adhesion could make sense...

 

thanks for your time and help!

This post was modified 2 months ago by Joãozinho
Posted : 02/03/2021 4:14 pm
Dan Rogers
(@dan-rogers)
Honorable Member

I wasn't so much going for adhesion as going for "were they squshed enough in the first layer when the second layer was put down"

So it's worth a live Z squish (ten or so at a clip until you see over-squish (build-up on the head starts, and you see drag marks in the squish.  The tell is the fuzzy texture left behind with a rectilinear bottom layer.

Posted : 03/03/2021 11:25 pm
Joãozinho
(@joaozinho)
Active Member

@dan-rogers

not sure if i got exactly all of what you meant cause of my english skills but still i am not sure what do you mean about the "ten or so at a clip" part. what are you mentioning with "clip"? And ten is 0.010 of value on the live z above the point where those over squish signals start to appear?

 

Once again, thank you so much for the help and time.

João

Posted : 04/03/2021 3:03 am
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