Issues printing with 0.6 and 0.8 nozzles

[43915 19]

Hello!

 

I've recently started printing with an Ultimaker 2+ through my new job. I've experimented a whole lot with both PLA and ABS and it's working great for the most part.

 

However, I'm having some issues with the larger nozzles. If I'm printing something big that doesn't need that much details I'd like to use the 0.6 or 0.8 nozzles to save time, but larger flat layers like the bottom layers tend to distort in a wierd way.

 

The printer leaves "ditches" or bumps in lines on the surface. My first thought was under/over extrusion, but I figure that since the distortion appear on the same place on every new line that's not the case, and I can raise or lower the speed significantly without making it better nor worse. The kind of symmetrical distortion that happens makes me think it's software related, but I'm fairly new to 3D printing and would need some help to figure out what I'm doing wrong here. 

 

I've never experienced this with the 0.25 and 0.4 nozzles so far. Even though I had some issues and a lot of trial and error with the 0.25 nozzle to begin with I find it much easier to get good results with now compared to the larger nozzles.

 

I'm posting an image where you can hopefully see what I mean. Currently printing with ABS, though it doesn't seem to matter if I use that or PLA when it comes to this problem.

 

Regards, 

Jocke

 

[Smithy 1,146]

Printing with bigger line widths is not so smooth as you know it from the .4 nozzle, but usually after the 2nd or 3rd layer it is gone.

 

But more important, have you levelled your bed after changing the nozzle? Maybe you are too close to the glass?

[43915 19]

I know it won't be as smooth as with smaller nozzles, but the surfaces ends up being so uneven that it doesn't look like it's solely a matter of "resolution". It looks like certain areas of large flat surfaces get distorted while the rest of it works fine and end up like I'm expecting. It persists through the entire print as well, only smaller surfaces look better. For example it's usually most prominent in the center of a large round surface, where it looks like it prints uneven on the exact same place on every line, creating one or several ditches or elevations across the middle.

 

I have levelled the bed after changing nozzle. I did however have issues with 0.25 PLA prints not sticking to the bed earlier and found several threads where people recommended to level it by eye instead of with the calibration paper that came with it. I got it to work really well with the 0.25 nozzle and I might be putting the nozzle a little bit too close for the larger nozzles after getting a feel for the 0.25. I realize now that the larger nozzles probably need a little more space than the 0.25 does. I have however also read on this forum that the leveling mostly affects the first layer. But I'll try that with the next print, thank you for the help!

[Smithy 1,146]

Yes levelling is mostly for your first layer, I was just asking, so if you have levelled it, then it is ok. 

 

What about nozzle temperature and bed temp? Are they ok and in the correct range for your filament?

You say you have the issues with PLA, but I would test it further with PLA, which is easier to handle and when it is ok with PLA then do the next step with ABS.

 

[geert_2 558]

Can you make a few close-ups of the bottom of that part? At first glance it looks like the first layer did not stick to the glass, sort of lifted, and created gaps. That would be my first guess. But we need to see the bottom.

 

If yes, then thoroughly clean your build-plate, first with isopropyl alcohol, then a couple of times with pure warm tap water only. No soaps, as they reduce bonding. Then apply a bonding method suitable for your model and material. If using the glue stick, do a thin layer and spread and wipe it smooth with a wet tissue afterwards.

 

For the later layers, it looks like it almost doesn't bond to the previous layers too? Seems a bit hard to believe, but it looks a bit like if you were laying plastic PVC-pipes next to each other. So how is layer bonding? Too big changes in extrusion-flow, feeding rate, or nozzle-temp seem unlikely. Or could that still be the effect of the first layer shining through till several layers up?

 

[43915 19]

I have been using the preset settings for temperatures initially but later I've managed to get better results through tips I've read here on the forum. Firstly I'm raising the bed temp to about 100-110C since that seems to be the consensus here to work best with ABS. Nozzle temp is preset from the machine at 260C, but lately I've started lowering it to 250 because it seems to work better. And I have front cover on the printer but no top cover.

With PLA I usually stick to the preset bed heat since it's been working fine, but I'm usually changing the nozzle temp and print speed on the fly when it's printing depending on the amount of details at that point of the print. On these larger prints with larger nozzles I do however often stick to a higher temp of around 220-230 and a bit higher speed.

 

Unfortunately I'm currently treating the part with acetone vapor, but I can assure you the bottom layer stuck to the bed, I do use the method with glue wiped out to a very thin layer with a wet tissue and I've never had issues with prints not sticking properly except for the 0.25 nozzle before I learned to level the bed by eye. Every time I print with these nozzles I check the bottom too since I had the same thought that you have, but the prints are always completely flat on the bottom and impossible to remove from the bed before it cools down. Nice smooth surface on the bottom once it snapps off at around 40C.

 

It does seem to bond well between layers, I do however think it looks like it overextrudes partially because on smaller areas of prints it kind of "smears" the plastic around as if there's too much plastic or the head moves too low. That was also an idea I had earlier to why the uneven surfaces happen, but the seemingly overextruding areas only happen on small surfaces, as in about 1cm^2 or less. Those areas also end up good at the end of the print. On larger surfaces it rather looks like the nozzle extrudes "uneven", as if the plastic "wiggles" a bit as it exits the nozzle, but it only happens on very specific places, the same place on every new line of plastic.

The only other thing I can think of is if the first layer overextrudes and makes an uneven surface right from the start which then transfers to every new layer onwards. On smaller surfaces the plastic has time to melt together with each layer but on the larger ones it might harden too much, I guess. That would explain why the problem areas remain on the exact same place throughout the print as well. I'll try experimenting more with lower temp or changing the speed and see if it works.

 

I'll try to get some images once the part has hardened again, I doubt the acetone will remove the uneven surface on the lower part of the print. Otherwise I'll make another piece and get some images then.

 

Thanks for helping me brainstorm in any case, I'm the only one familiar with the printer on my workplace, so I have no one to discuss these kinds of problems with.

 

 

EDIT:

I've experimented a bit more now and kept an eye on the printer when it make the first layers, and it did look like over extrution on the first layer which then stuck with every following layer. I tried messing with temperatures, speed and fans for a while but it kept doing the same thing.

Finally I lowered the initial layer height to much less and it finally worked like it should. It almost looks like the printer puts the head too close to the bed when you print with higher initial layer height, and hence drags through the plastic it extrudes.

I tried leveling the bed with more distance between the nozzle and bed, but after a certain point it just stopped adhering to the bed instead while still somehow getting the plastic semi-stuck to the nozzle when it moves. But since it works with lower initial layer height I'm satisfied, I can work with that. Thanks for the help!

Edited September 25, 2020 by 43915

[Jkazemek 1]

I know it has been awhile but I just wanted to chime in here and say thank you. I have been racking my brain, trying everything and anything (contemplated on throwing the machine) and it was This thread that s’ok Ed my issue.  It was lowering the initial layer height. So thank you!  My wife thanks you too. Now I can go to bed lol.