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First layer fill issue

Posted: Sat Dec 15, 2018 11:30 am
by Daws
I've noticed that I get different results for the first layer solid fill dependent on the direction of travel of the extruder.

The easiest way to describe this is to imagine printing an item where the bottom layer is a square, I have found that I get terrible infill if the print head starts at the top left of the square and works its way down to the bottom right (using linear solid fill set at 45/135 degrees)... but if the print head starts at the bottom right corner and makes its way to the top left, I get a beautifully smooth solid fill.

I have noticed this mixture of bad/good bottom solid fill on multiple prints but only worked out why it was happening tonight.

Check out the slicer preview from my current print job, this picture shows the print head moving from the lower right up to the upper left, print quality is perfect, just like a freshly ploughed field.

layer_1_1.JPG


The following picture shows the extruder moving from the upper left to the bottom right of the area and the print is lumpy and bumpy, like the nozzle is dragging through the material that has already been laid down.

layer_1_2.JPG


I've done a search but "First layer problems" is quite a common term in the world of 3D printing ;)

I've noticed this on multiple brands of PLA and I generally print at 0.2 layer height with a 0.4 nozzle.

Anyone else noticed this?

Re: First layer fill issue

Posted: Mon Dec 17, 2018 5:16 am
by Vicky@Raise3D
Would you mind share gcode, stl and date files with us?

Re: First layer fill issue

Posted: Mon Dec 17, 2018 6:43 am
by Daws
Sure, the file is too large to attach here as a zip, I have put it on my dropbox here
images of the first layer printing here

This issue is not just limited to this model and I believe this also contributes to a similarly bad finish on the top layer too, the top is harder to confirm as I'm not usually watching the end of a print.

I re-homed my N2 to see if that would help, it prints the first layer at the perfect height but it hasn't made any difference to the quality when filling areas from the "top" down. Filament for this job was Raise Premium PLA

Re: First layer fill issue

Posted: Mon Dec 17, 2018 9:18 pm
by crimsonyoshi
I've noticed over larger or more complex objects, if I don't have Z-hop enabled, things can get a little wonky. Smaller singular objects have never had a problem with default PLA print settings (or polycarbonate).

For example, if you were to print a non hollow tube however high, and maybe 3" in diameter, no problems. Get that tube above 6" and I'm going to need Z-hop. Print a cone with some attachments that require support layers, and have the support structures basically be three seperate rafts on the print bed? Absolutely need z-hop enabled. Prints have turned out excellent (save for some thin stringing) with Z-hop on, and there's not a huge difference in time on the smaller models for comparison testing. Maybe 3-5% longer.

Re: First layer fill issue

Posted: Wed Dec 19, 2018 2:56 am
by Vicky@Raise3D
I'd like to have you test some settings if you'd like to have a try.
Edit the first layer height to be 0.2mm, print speed of first layer to be 10mm/s.
Increase bed temperature to be 55-60C to provide better adhesion for the first layer.
Enable Print Shells in optimal order can provide better binding among shells.
And there look like too many retractions at your first layer. Please increase the minimal travel for retraction from 0.5 to 1.0.

Re: First layer fill issue

Posted: Thu Dec 20, 2018 4:21 am
by Daws
Thanks Vicky, I'll give those settings a go and see if it makes a difference.

Re: First layer fill issue

Posted: Fri Jan 11, 2019 7:55 am
by Daws
Vicky@Raise3D wrote:I'd like to have you test some settings if you'd like to have a try.
Edit the first layer height to be 0.2mm, print speed of first layer to be 10mm/s.
Increase bed temperature to be 55-60C to provide better adhesion for the first layer.
Enable Print Shells in optimal order can provide better binding among shells.
And there look like too many retractions at your first layer. Please increase the minimal travel for retraction from 0.5 to 1.0.


Hi Vicky, I tried these settings and they have made no difference. Print quality for the first layer when printing in one direction is remarkably different to printing in the other direction. Is there some known mechanical limitation of the hardware (backlash, flex etc?) that could cause this?

Re: First layer fill issue

Posted: Mon Jan 14, 2019 10:49 pm
by Vicky@Raise3D
If the issue only happens on one side but not the other, either it is due to cooling or poor adhesion which may be caused by unleveled bed or dirt on build surface.