ROUGH PRINTS>?? weird...

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JonathanB
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ROUGH PRINTS>?? weird...

Post by JonathanB » Tue Mar 10, 2015 9:32 pm

I'm sure some of the 3DP veterans would know what the issue is here... I'm getting some roughness in my prints. This is with ABS. The weird part is, it doesn't do it on every print and if you notice, some area's print fine, some not so good...really weird, almost makes me wonder if it's something to do with the filament... The one that looks slightly nicer was at 230C, bed 99. The really rough one's were 235, 110C, which is what I normally cook with so not sure what's going on. Seems like it got worse...

These parts were .25 layer height(.35 nozzle), interestingly, I just printed a tiny part with .15 layer height prior and it came out looking great, but I've printed at .25 layer height a million times before with great results...I'm wondering if it could be cross contamination with stuff lingering in my nozzle, other filaments etc?

all insights are welcomed! Gotta get these prints dialed in, they need to look perfect, they will be going up for sale.
another issue is that I've started using the LCD lately(SD card). Think I'll plug in and try to run the same prints on Pronterface to help narrow down the cause.
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piercet
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Re: ROUGH PRINTS>?? weird...

Post by piercet » Wed Mar 11, 2015 1:18 am

Looks like a couple of minor calibration issues. That's a long skinny part, and the layer issues you are seeing are in the areas where it is transitioning to a much different layer profile, where it goes from the whole part to just the upper structure, where it meets the holes, etc.

For starters, I think it is possibly overextruding slightly. You might try bumping up your filliament diameter modifier slightly and reprinting. If you are using Slic3r, since it is such a narrow part. you may want to make sure that "enable auto cooling" is turned on. It was off by default in some slic3r profiles. I'd also see if it is set to print the outer perimiter first, and set it to print at least 3 perimiters before infilling.

It also looks like you might have had a tiny bit of lifting on the inner edge of one of the parts. That could be an artifact of the part removal process, but it might have been enough to cause an issue given how skinny the part is. You might try printing it with a 2-3mm brim layer if you aren't already.

Another thing it could possibly be is nozzle wobble due to a worn bearing, somethign loose, or something out of allignment. If you have that, you can usually see it in a large flat first layer area. it often shows up as a wavy first layer surface, especially towards corners or along long travel paths at the edge of the highest point of acceleration. Overextrusion can also cause that symptomatically because the print nozzle ends up with too much plastic and no where to put it, so it forces it up slightly until the overpressure is released. If thats the case you'll see excess material buildup in sharp corners.

if you thicken that part another mm or 2, it will probably print easier.

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JonathanB
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Re: ROUGH PRINTS>?? weird...

Post by JonathanB » Wed Mar 11, 2015 1:28 am

I plan on doing some tests to figure this out, but I just did a quick measure of my filament dimaeter, and I'm getting crazy values from 2.75-3.00mm within a few inches between measuring points, and some area's are thinned out, if I roll my caliper around in one place it will go from 2.7 to almost 3mm meaning it's not round. It's looking like the end of this roll of ABS has some tolerance issues....maybe a worn out extruder nozzle..

when setting filament diameter in slic3r, is it better to air on the larger or smaller side? How exactly does that parameter affect the extrusion...??

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JonathanB
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Re: ROUGH PRINTS>?? weird...

Post by JonathanB » Wed Mar 11, 2015 1:35 am

Peircet, I really appreciate the thorough response, the more idea's the better, I have most of the those things checked off the list, but the whole corner lifting thing is just an optical illusion because it's sitting on a piece of acrylic on the table top, I used a 10mm brim and it stuck like glue so no warping or lifting at all... you're right though, just a calibration issue, it does look like it's over extruding in those area's, I'm going to recal the extruder tomorrow.

meh, loose bearing issue is low on the list, everything is pretty tight and it would have showed up in that other print I did with the .15mm layer height, that came out so perfect I could have ate it with some whip cream and a cherry on top.

I also noticed that the end of this roll of ABS is extremely out of tolerane, as mentioned in my previous post so not sure if I can fix that issue but the results I'm getting, ie fine some layers, then blobby at random times would make sense if the filament was out of tolerance... also, I've printed with this roll prior to this without issue so something changed along the way. I'm going to adjust the retraction settings also. Just going to try a bunch of things tomorrow and report back.

if anyone has any other idea's, keep em coming, iz more than appreciated!
thanks guys.

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mhackney
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Re: ROUGH PRINTS>?? weird...

Post by mhackney » Wed Mar 11, 2015 6:58 am

Looks like a bit of "erratic" extrusion and perhaps too high melt temp.

Erratic extrusion can happen when the filament snags along the cold path. That creates excess back pressure and when it finally pops free (this all happens in fractions of seconds) it exerts excess force on the melt, cause a little over extrusion blob. If the part were consistently blobby I would say over extrusion but this part seems to have areas of blobs and areas of gaps. Inconsistent filament diameter can do this - especially if the size is too large and it is snagging somewhere. See my recent post where I discovered the aluminum mount between the extruder and Budhashnozzle was snagging my filament.

The other way inconsistent filament diameter can impact this is at the extruder - thin diameters may not be gripped as well and actually slip. Again, resulting in gaps succeeded by blobs.

Check the filament path through your extruder and hot end.

If you have very inconsistent filament the best bet is to take 10 measurements and average them. Test on a piece and then adjust. It can be challenging since the inconsistencies may not be uniform over the length of the filament.
Sublime Layers - my blog on Musings and Experiments in 3D Printing Technology and Art

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JonathanB
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Re: ROUGH PRINTS>?? weird...

Post by JonathanB » Wed Mar 11, 2015 10:10 am

well look who it is, .....ya know, I was sorta hoping you would come along and find this thread. ;)
you're word is golden on this stuff so thanks. I'll look into all those things.. yes, snagging could be a very real possibility as the roll dwindles in size, I also like the theory about the off sized filament not gripping well on the extruder bolt, all very logical reasons. I'm pretty sure filament that goes from 2.7-3mm is not very standard? right? Just seems to have gotten worse towards the end of the roll. I might give the supplier a call. Would it be better to overshoot or undershoot when setting the filament size..? thank you for helping with this...*ehem*... persnickety situation.

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mhackney
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Re: ROUGH PRINTS>?? weird...

Post by mhackney » Wed Mar 11, 2015 10:18 am

2.7 to 3.0mm is a BIG variation for filament. Do you have any other that you can test?

Under or over- shooting both have their issues. Under and you get an incomplete part, maybe week bonding, etc. Over- and you get a bigger part, maybe blobbing or oozing. I'd just do the 10 point average over 5' of filament (measure at 6" intervals for a total of 10 measurements.)
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JonathanB
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Re: ROUGH PRINTS>?? weird...

Post by JonathanB » Wed Mar 11, 2015 10:39 am

Ok thanks..

Just remeasured this morning, it's more like 2.8ish to 2.95ish, sometimes 3mm... still a pretty wide variation I would think. I have some Lulzbot HIPS here and the variation is like 2.9-2.95, which I think is acceptable. I'm getting the large variation with the other brand because it's ovalized in some areas, I know that because I can see it and when I rotate my caliper around it changes :). And yes, I have other filament I can use as a control test afterwards..

So I have a test print going now. Some of the changes I made were...

1. tightened up the tesnsion screws, assuming the filament is uneven, should help grip the smaller diameters better.
2. In Slic3r, adjusted retraction to 1.5, 50mm/s speed.
3. In Slic3r, 2.92 as filament diameter vs. 2.85, brought travel speed down from 180 to 130 (reduce heat build up in motors)
4. Recalibrated the extruder using the LCD, set to 890mm/s vs. 900mm/s. First time I've done this on the LCD, didn't think I needed to because I had good prints before. Or maybe since they were larger prints, the blobbing was just not as noticeable. Now it's BANG on.

If I get the similar results, I'm going to keep all these settings and then try a few different ABS filaments to see what happens there. It's a matter of picking off each parameter, gotta be scientific with it. ;)

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JonathanB
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Re: ROUGH PRINTS>?? weird...

Post by JonathanB » Wed Mar 11, 2015 12:21 pm

Alright guys, so considering all the adjustments I made (detailed in my previous post). Here is the outcome. Looks like I'm on the right track.. the blobs are gone, only thing now is some slight area's of under extrusion, but overall layer bonding seems good regardless. The print came out clean enough that I could slide fit parts, which is what I want.

The little part was from a seperate print, .15 layer height.
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Re: ROUGH PRINTS>?? weird...

Post by mhackney » Wed Mar 11, 2015 12:26 pm

How is this part oriented on the table as it prints? It now look like you have some layer misregistration. This is usually from either loose belts or slipping pulleys on the steppers. Sloppy guides can also contribute. If it is aligned in X or Y primarily it gives you a starting place to look deeper.
Sublime Layers - my blog on Musings and Experiments in 3D Printing Technology and Art

Start here:
A Strategy for Obtaining Great Prints

Strategies for Resolving Print Artifacts

The Eclectic Angler

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