Jump to content
Ultimaker Community of 3D Printing Experts
Sign in to follow this  
ggabriele3

Cura adding 'evil' fill, causing warts, ruining prints.

Recommended Posts

Hi everyone. First post on the forum.

I have a Printrbot Simple Metal and I have been working with Cura.

Cliff Notes: Cura adds infill behind curved layers that is screwing up my prints, and the walls have a "rippled" look to them.

This issue affects any model that has curves, but this is the specific one I'm using for testing: http://www.thingiverse.com/thing:371177. The model has long curves, small curves, overhangs, and fine detail.

 

I was getting blobs randomly all over the print and vertical ripples all over.

 

FRONT: http://i.imgur.com/u1eEueU.jpg

REAR: http://i.imgur.com/NxBr1DZ.jpg

Bad Overhangs: http://i.imgur.com/1r1wvHa.jpg

 

Initially, I tweaked virtually every variable independently (temperature, filament quality (I have tried cheap and expensive), E-steps (adjusted down +/- 5%, 10%), acceleration, infill, speed, retraction distance and speed, etc). Nothing solved the issue.

 

Finally, I looked at the tool path in Cura around the area where the warts were worst. This is what I find (Red = outer shell, Green = inner shell, Yellow = infill):

 

"Evil Infill": http://i.imgur.com/41gYtlP.png

Another Angle: http://i.imgur.com/dV1TqJU.png

 

Cura is adding zig-zag infill (yellow) on the inner shell to support layers above it. The warts appear on the outside wherever Cura puts it on the inside.

 

This is what the interior looks like printed with Cura: http://i.imgur.com/Z2jmDxP.jpg

 

Slic3r does not do this: http://i.imgur.com/9yRi8pq.png

And, as a result, the outcome is cleaner: http://i.imgur.com/w8AfBjf.jpg

 

Comparison of the two results, upside-down showing the overhangs: http://i.imgur.com/NgNrexK.jpg

 

Today I upgraded from 14.21 --> 15.01, but i'm getting similar issues.

 

I printed several models with 0% infill, and all the jagged mess is still in there.

I can post more pictures if needed.

 

 

What can I do about this?

 

Share this post


Link to post
Share on other sites

Thanks for the reply. Details:

0.4 Nozzle

0.2 layer height

0.8 shell thickness

0.8 bottom/top thickness

0.3 initial layer thickness.

I thought about just making the shells very thick to move the jagged infill away from the outer edge, but this idea falls apart with thin/intricate designs. It just makes the jagged infill tighter, so the printer is violently moving back and forth on the X and Y axes.

 

Share this post


Link to post
Share on other sites

Yeah, as said above, print with more wall thickness. I never go under 1.6mm. Perimeter loops are stronger and faster than infill; printing with thin walls but heavy infill is poor print optimization.

 

OK, I just adjusted Shell Thickness from 0.8 --> 1.6 and let Cura re-slice.

The yellow infill is still there, just moved further from the edge. Cura seems to be putting this extra infill there whether the print needs it or not.

And what about printing with stuff that's supposed to be transparent, like a vase or bowl?

For example, I'm printing with clear filament right now. Using the "simplify short movements" plugin, i'm getting a much smoother exterior, but the messy jagged infill is visible through the shell.

 

Share this post


Link to post
Share on other sites

Nick Foley has taught me some great techniques for getting better quality. I'm pretty sure he's smarter than I am. So that's probably good advice. The "jagged infill" near the edge is just what you thought - support for layers above. Yeah it shakes the machine a bit but it's usually worth it.

 

For example, I'm printing with clear filament right now. Using the "simplify short movements" plugin, i'm getting a much smoother exterior, but the messy jagged infill is visible through the shell.

 

Interesting point!

There's an expert setting in Cura that removes this: "Black Magic - only follow mesh surface". The problem is I think it won't do top surfaces either. Unless maybe you check them on purpose? Probably not. Hopefully Daid will read this topic and some day allow you to disable that "jagged support infill" although *most* of the time it *improves* quality.

 

Share this post


Link to post
Share on other sites

By the way your leveling looks a bit off. You should have the print bed about .1mm closer to the nozzle for the bottom layer. I know you said you did .3mm bottom layer thickness but Cura commands the nozzle to .3mm above the bed so it should be squished more wide than tall (pancake like but with .3mm by .4mm cross section). Whereas your bottom layer is more round.

 

Share this post


Link to post
Share on other sites

Personally the shaking doesn't bother me all that much, it's more the time it adds. It adds a butt load of print time when it's doing that extra infill on every layer. The idea is great and it's often helpful, but there have been many many times where I've wanted to toggle it off (or adjust the angle at which it activates).

 

Share this post


Link to post
Share on other sites

By the way your leveling looks a bit off. You should have the print bed about .1mm closer to the nozzle for the bottom layer. I know you said you did .3mm bottom layer thickness but Cura commands the nozzle to .3mm above the bed so it should be squished more wide than tall (pancake like but with .3mm by .4mm cross section). Whereas your bottom layer is more round.

 

I have improved it since then, but it has been a struggle to get that right. When I print calibration cubes, it looks as though the Z-height is too low...the corners bulge a bit as if it's being laid down too flat, and bulging at the corners.

If I raise the Z-height any further, however, I get the stringing on the bottom layer that you see in that pic.

 

Share this post


Link to post
Share on other sites

Check that the three leveling screws are properly countersunk into the heated bed. There was a bad batch of screws that meant that they were sticking up a bit above the surface of the heated bed which can make the glass bow a bit. It's easy enough to fix with a large drill bit or, preferably, with a countersinking bit.

 

Share this post


Link to post
Share on other sites

Check that the three leveling screws are properly countersunk into the heated bed. There was a bad batch of screws that meant that they were sticking up a bit above the surface of the heated bed which can make the glass bow a bit. It's easy enough to fix with a large drill bit or, preferably, with a countersinking bit.

 

I'm actually on a Printrbot Simple Metal - it auto-levels.

 

Share this post


Link to post
Share on other sites

I have also had this problem as stated by the OP.

Also see Topic: http://umforum.ultimaker.com/index.php?/topic/9509-no-infill-means-no-infill/. I think it may be the same thing.

Edit: So my self doubt was justified per Daids comment below.

To me, I think Cura may be evaluating the wall thickness rather than the wall width. Sounds like semantics, but width would imply measurements strictly parallel to the X-Y plane. Thickness may be evaluated at a slope perpendicular to the wall angle. It may be a misnomer for users to think of thickness as my referred to 'width'. So my theory is that when you 'N' number of perimeters don't add up to the desired wall thickness as measured on the appropriate slope, infill is added. If this is the case, it would be nice to be able to instruct Cura to print N perimeters regardless of diagonal thickness - if you know what I mean.

Disclaimer: I am not coder, and have not looked into this any more than to observe the print behavior. I could be completely wrong...

 

Share this post


Link to post
Share on other sites

Disclaimer: I am not coder, and have not looked into this any more than to observe the print behavior. I could be completely wrong...

 

You are wrong indeed. What we're looking at there and in your topic is "top/bottom" skin. Cura puts material there, because if you look from the top of the model, there needs to be a 0.8mm piece of solid material there. Which is why it is putting the yellow zig-zag lines there.

 

Share this post


Link to post
Share on other sites

You are wrong indeed. What we're looking at there and in your topic is "top/bottom" skin. Cura puts material there, because if you look from the top of the model, there needs to be a 0.8mm piece of solid material there. Which is why it is putting the yellow zig-zag lines there.

 

that's interesting. I set Bottom/Top Thickness to zero and the lines disappeared.

But why is it putting that infill all over the inside of the print? And why a zig-zag? The effect of the zigzag is to make the printer shake violently back and forth (even with acceleration turned down).

I really want to understand this, and how to control it. I don't want to go back to Slic3r.

 

Share this post


Link to post
Share on other sites

Thank you Daid. I stand corrected. I'll leave my blunder for all to see. Just to be clear, the linked topic is not mine, just another current one seemingly the same symptom.

I had realized this top/bottom skin effect in the mid model for myself in the past. Apparently, I have also forgotten it.

I'm sure its been asked before if the top/bottom skin could be turned off except for the very top and bottom. Obviously this couldn't be universal for all models as most will have horizontal top/bottoms in middle heights.

Is there a critical wall angle where the top/bottom thickness begins to take effect?

I'll try pm_dude's swap-at-z as a solution as he suggested in the linked post above.

 

Share this post


Link to post
Share on other sites

that's interesting. I set Bottom/Top Thickness to zero and the lines disappeared.

But why is it putting that infill all over the inside of the print? And why a zig-zag? The effect of the zigzag is to make the printer shake violently back and forth (even with acceleration turned down).

I really want to understand this, and how to control it. I don't want to go back to Slic3r.

 

I think part of the answer to your question is that Cura was is designed, tested and optimized for UMO and UM2, which have relatively light hotends. That lets them accelerate faster with less force and therefore less shaking.

That said, it has been a while sense I looked at the code, but I do believe Cura marks infill on the gcode output. It shouldnt be to hard for someone to write a plugin that destroys infill between a chosen set of build heights, if someone hasn't already. I would do it, but I have too many other things going on.

Share this post


Link to post
Share on other sites

I think part of the answer to your question is that Cura was is designed, tested and optimized for UMO and UM2, which have relatively light hotends. That lets them accelerate faster with less force and therefore less shaking.

That said, it has been a while sense I looked at the code, but I do believe Cura marks infill on the gcode output. It shouldnt be to hard for someone to write a plugin that destroys infill between a chosen set of build heights, if someone hasn't already. I would do it, but I have too many other things going on.

 

Well here's the thing - there is a plugin that simplifies the lines (it's called Simplify.py) that enabled me to get a smooth outer surface.

However, the infill is still there. I printed the hedgehog model in transparent filament. You can see the zig-zag infill on the inside, making the print look messy even though the outer shell is smooth.

So it's really not an issue of which printer, since there are other threads on this (see: "no infill means no infill").

My suggestion would be simply to make it an option.

Though Cura may have been developed for the UM, I hugely prefer it to Slic3r and Repetier. It's much more user friendly and easier to tweak settings from print to print. People are asking Printrbot to write up tutorials for Cura. I humbly suggest that it's worth the devs time to keep other printers in mind.

Share this post


Link to post
Share on other sites

I don't disagree that it would be nice, and maybe Daid will decide to do it, but, it isn't all on him. Not only is Cura open source, but it has a plugin system that would pretty easily allow anyone to do the thing you want. I bet you could probably even write the plugin yourself, if you sat down and put your mind to it; though I would check to see what is in the latest tweek@z version first.

Share this post


Link to post
Share on other sites

It's hard to turn off top/bottom thickness on some parts of the model and "only leave it for the real top and real bottom". This assumes you are printing spheres or cubes. Most things I print have many many "top" and "bottom" sufaces at many different heights.

I've never minded the fast paced zig zag of this little bit of infill on some layers because the UM2 head is so light weight. Although if I ever print with transparent filament I will be equally annoyed by it and probably set my top/bottom skin thickness to .2mm or 0mm.

Did you try that @ggabriele3? See what it looks like in the slice view?

 

Share this post


Link to post
Share on other sites

It's hard to turn off top/bottom thickness on some parts of the model and "only leave it for the real top and real bottom". This assumes you are printing spheres or cubes. Most things I print have many many "top" and "bottom" sufaces at many different heights.

I've never minded the fast paced zig zag of this little bit of infill on some layers because the UM2 head is so light weight. Although if I ever print with transparent filament I will be equally annoyed by it and probably set my top/bottom skin thickness to .2mm or 0mm.

Did you try that @ggabriele3? See what it looks like in the slice view?

 

You mean setting Bottom/Top thickness to zero? yes - it gets rid of the yellow infill, but also makes the bottom and top very thin. Setting it to zero makes a part that has no bottom.

I guess I understand now what's happening. It sees the internal layers that have overhangs as having "tops" and "bottoms".

My expected behavior was that it would only set the actual top and bottom of the entire part, I suppose by measuring the distance from the bottom layer up and the top layer down, where Shell Thickness would set a minimum thickness for the inner walls of the entire print.

 

Share this post


Link to post
Share on other sites

I guess I understand now what's happening. It sees the internal layers that have overhangs as having "tops" and "bottoms".

YES ! I was going crazy because even with the black magic "only follow mesh surface", Cura adds some infill every now and then (but a bit less than wihtout this option). My next try will be to combine this setting (0 infill, no top and no bottom) with the "swap at Z", and see what results I can get ! Getting rid of the "extra" infill is pretty much reducing a 3hour print by a whole hour, which is a pretty nice improvement !

 

Share this post


Link to post
Share on other sites

It's hard to turn off top/bottom thickness on some parts of the model and "only leave it for the real top and real bottom". This assumes you are printing spheres or cubes. Most things I print have many many "top" and "bottom" sufaces at many different heights.

I've never minded the fast paced zig zag of this little bit of infill on some layers because the UM2 head is so light weight. Although if I ever print with transparent filament I will be equally annoyed by it and probably set my top/bottom skin thickness to .2mm or 0mm.

Did you try that @ggabriele3? See what it looks like in the slice view?

 

I figure one could at least destroy infill between a desired set of layers. Sort of a sledgehammer approach.

 

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

Announcements

  • Our picks

    • Architect Design Contest | Vehicles.
      We're open for entries! - Design and submit your 3D designs of architectural entourage - vehicles - for a chance to win a large filament pack. Presenting an idea, an architectural design or something as big as an urban project isn't easy. A scaled model can really help to get your idea across.
        • Like
      • 14 replies
    • What The DfAM?
      I'm Steve Cox, an experienced engineer familiar with 3D printing. I wanted to share some DfAM guidelines with this community to help and make stronger parts.
      I'm also an Autodesk Certified Instructor for Fusion 360, so many of the images in ...
        • Thanks
        • Like
      • 18 replies
×

Important Information

Welcome to the Ultimaker Community of 3D printing experts. Visit the following links to read more about our Terms of Use or our Privacy Policy. Thank you!