Newbie test cube printing walls lines separated in pla

[paulrhee2002 2]

I had (somewhat) successfully printed a test cube with flexible filament but when test printing with pla, each wall line is completely separated from the other walls.  It looks like concentric infill vs a 3 line solid wall.  I did mess with cura settings in between the flex test cube and pla test cube.

I am using a tevo black widow with cura and the cube was downloaded from thingiverse.  

I have attached pics of the cube (bottom broke off) as well as pics of my cura settings.

Newbie question but appreciate any help!

[gr5 2,172]

The problem is you have severe underextrusion.  Maybe about 50%.

 

Your print speed looks to be 30mm/sec with 0.3 layer height and 0.4 line width that is 30*0.3*0.4 or 3.6 cubic mm/sec.  That should be doable.  So I'd guess your feeder is somewhat weak.  You need about 5 pounds or 3kg force to push hard enough to print at that speed with typical printing temps (220C).  So I'd test the feeder and make sure it can pull that hard. 

 

One way to test is to energize the feeder but don't advance it and then pull back on the filament hard and see how much force it takes for the filament to slip.

 

[paulrhee2002 2]

Thanks for the reply!!!!  I did loosen my feeder tightening screws and will try tightening them more and reprint.

Will follow up after re-printing!

 

[paulrhee2002 2]

You are the best!  When I switched filaments I didn't tighten the feeder screws as much thinking I don't want to over-tighten.

The prints came out so much better now, but any other flaws in the print and/or advice you have is all greatly appreciated!

Thanks again so much.  I spent nearly a week changing cura settings....  I should have asked sooner.  Thank you again.  

[paulrhee2002 2]

I also increased the nozzle temp to 210.  Still to low?  Does the top layer seems lumpy on the perimeter lines?

[geert_2 557]

To me this seems reasonably okay, it looks like what you could expect at 0.3mm layer height. Although there seems to be a bit of "elephant feet" at the first layers (=thick bottom). There may be other reasons, but often this is caused by a bed temperature that is a little bit too high for the material, so the first layers sag a bit. Maybe you could try to lower your bed temperature by 5°C and test if the model still sticks well? Stay with the print, in case the model would come off, so you can abort.

 

When printing on a glass bed (I don't know what bed your printer has), we often have to find a balance between bed temp and good bonding. A too low temperature reduces bonding, and the model may suddenly pop off while printing. A too high temperature also reduces bonding: the model stays too weak, and warping forces tend to peel off the model gradually, in my tests.

 

In both my UM2, and for PLA, the best bed temperature was the default indeed, 60°C. Although 55°C also worked usually. At 45...50°C the models would suddenly pop off. At 65...70°C they would get severe elephant feet and would be peeled off. This will differ from material to material, and printer to printer, so I recommend doing test prints at various bed temps, and definitely stay with the printer!

 

[paulrhee2002 2]

Ok thanks again!!!!

-Paul

[paulrhee2002 2]

Hello, I am following up with you regarding another issue.  You were so helpful last time thank you!

I switched my nozzle to 1mm because my prints need speed vs detail.

Not sure whats going on.  Is this under-extrusion again?

I printed a filament spoolholder but it's not so smooth and has to pull pretty hard for the spool to turn.

 

I printed at .8 layer height and 1 mm line width.  25mm/s speed, 215 nozzle temp, 60 bed temp, 15% infill, 3 wall lines and 2 top/bottom layers

Maybe that's a factor?  Any help is always appreciated!!!!

[SefPinneyStudio 5]

On 6/12/2019 at 8:52 PM, paulrhee2002 said:

I printed at .8 layer height and 1 mm line width.  25mm/s speed, 215 nozzle temp, 60 bed temp,

 

Old Post.  Weighing in for Community benefit.

 

From my experience / understanding:  0.8mm Layer likely too Tall for the Nozzle Dia of 1mm.  (Narrow success range)

Also, I don't think Cura does great out of the box calculations for > .8mm nozzles... I'm guessing b/c UM's printers don't ship with 1mm or larger.(Lack of feedback, machine designed for < .8mm)

I'm assuming you're using a 1mm nozzle.  If you ARE, the Line width should be .9 or .95mm (fractionally less, to force the extrusion ovals into close contact with adjacent lines.)

My reading tells me that for a 1mm Nozzle (not UM.) you could do 0.5mm Layer height, or maybe .6  but  .7 or .8 would require real tweaking. 

Slowing speed down is always important, because "you're already" pushing lots more plastic at 1mm.

Also, 215° might be too hot, If 190-200 works for .8mm, thats a big jump to 210 for PLA.

 

Start your Cube printing at the low end of the Temp range and increase on-the-fly until there's no underextrusion to find your spot for Feeds and Speeds.

 

Do others experiences comport with these ideas on larger nozzles?

[geert_2 557]

Another factor is cooling: in small models it doesn't get enough cooling time. So the whole thing stays soft and sags. On sharp corners, the strand is pulled inwards like a rubber band.

 

See the tests I did a few months ago. This is PET. Nozzle = 0.4mm.

Layer-thickness from left to right (mm): 0.4, 0.3, 0.2, 0.1, 0.06.

Top row: 50mm/s, bottom row: 10mm/s.

 

You see the same rounding and not-enough-cooling effects in the thickest layers (left), although less than in your tests.