Problems with bottom layers

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Tinkerer
Posts: 176
Joined: Mon Oct 09, 2017 8:30 pm
Location: Germany

Problems with bottom layers

Postby Tinkerer » Sat Dec 09, 2017 11:55 am

Hi,

I am constantly having this problem:

IMG_4016.jpg


I have tried a brand new roll of Raise3D PLA and it's a new buildtak foil but still
the printed material partially comes off the surface during the print.

It gets better when (and if...) the print continues and reaches higher layers.
The print temperature is as low as 195°C and the heated bed I have tried at cold, 40°, 60°C.

I already noticed the same issue with other materials, including Raise3D ABS, BioFila PLATec and PTEG.

Can it be that this is related to the temperature-control-issue my printer seems to suffer from?
...there's nothing like the smell of fresh ABS in the morning...

ABH
Posts: 172
Joined: Sun Aug 14, 2016 7:31 pm

Re: Problems with bottom layers

Postby ABH » Sat Dec 09, 2017 1:44 pm

Raise3D PLA sticks very well to Buildtak.
What is your z-gap (bed to nozzle-tip distance)?

Did you check that your build plate is level?

Although I think it is unlikely that your z-gap is larger in the center of the glass plate than in the peripheral, it should be checked.
(z-gap is more likely to be smaller in the center than in the peripheral, due to the glass plate bending.
A metal ruler can be used for checking along x and y axes and diagonal.

Raise3D recommendation is to use 0.2 mm z-gap. This is too much, in my opinion, especially if you use 0.2 mm layer height or below. I use 0.1 mm z-gap and 0.2 mm layer height for the first layer.
Using 0.1 mm z-gap requires that the bed is extremely level, and this is where the Raise3D printers might suffer when delivered from the factory.
Remember, that all slicers expect that there is 0 (zero) distance between the nozzle-tip and the bed, so any z-gap basically represents a volume that is not filled with extruded plastic, i.e. it corresponds to strong under-extrusion.
That being said, in practice it is impossible to get full filling for the first layers, so we need a small gap.

It is also important that the Buildtak is clean and degreased before any new print is started. I almost always use a Scotch-Brite Heavy Duty Scrub Sponge to remove any residue from earlier prints.
You claim that your Buildtak is new, so that is probably not your problem.

If you have used the Buildtak for ABS or ASA (what I never do anymore) then it is extremely important to use the scrub sponge, otherwise PLA will not stick the the Buildtak surface at all.

Tinkerer
Posts: 176
Joined: Mon Oct 09, 2017 8:30 pm
Location: Germany

Re: Problems with bottom layers

Postby Tinkerer » Sat Dec 09, 2017 7:21 pm

Hi ABH,

thanks for your tips.

The print bed is level, did check with a dial gauge.
Actually, my N2 suffers from a lot of things but not from an uneven bed leveling;-)

Z-Gap I do actually have at 0.2mm - will try at a lower setting again.

With "new" Buildtak I do not mean I have never printed anything else on it.
But I did install this one just a day ago so there was not much printed on it so far.
I did actually print something with ABS on this buildtak before I started the print in question.
But the area where the defect showed has not been printed on before...

I try not to use "hard" things like the sponge you mentioned to clean the buildtak because my impression was that this leads to a smoother sufrace - which would give less adhesion.
Until now I just use dish cleaning solvent and my hands.

I think I will cease using ABS and Raise3D-PLA and switch to BioFila PLA Tec - that stuff now really sticks well to the buildtak, prints very even surfaces, can handle higher temperatures than ABS and is also mechanically very stable. Really great stuff! Do not know whether that is available outside Germany already but it is worth a try.

My current conclusion:

I am afraid there are significant variations in the temperature (hotend end and/or build plate) with my printer.
Because the same stuff suddenly works and next time it doesn't - without changes in the parameters on my side.
Since this devil of a N2 did already throw thermal runaway-errors several times now, that might not be too unrealistic to assume.
...there's nothing like the smell of fresh ABS in the morning...


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