Interior structures not printing

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bmz
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Interior structures not printing

Post by bmz » November 9th, 2017, 10:15 pm

Hello all. Im very new to this. My printer is anet a3, and seems to work fine. Im using repetier to run the print, and cura 2.5.1 for slicing. I had tried using the very latest cura, but it slowed down my laptop to about a 5 second lag time for keyboard inputs!

So, heres the issue. I designed a part with some interior structures at 2mm thick. Just basic vertical walls and some round pillars to surround through hole locations. I was very careful to extrude all the features that I wanted as surfaces at 2mm thick. My slicer settings are as follows. 0% infill, support structures on, 1mm wall thickness, 1mm top and bottom layer thickness.

So theoretically, all my interior wall structures should print at at 1mm thick per side resulting in 2mm thick walls. The bottom skin should be solid at 1mm thick, and so should be top skin. All interior open spaces should remain open.

The way its printing is with the interior wall structures as 1 pattern, then it lays down an infill right over the wall structures. The outside walls are intact, but the bottom skin on those has a bunch of holes in it. So, my interior walls are disappearing, and the the structure wants to print more solid than open. I killed the print when it became obvious that it was going to do this.

How can I get a solid bottom layer, solid interior walls, and then a nice solid top skin? My exterior side walls seem fine, as do my round pillars that surround through holes.

The point is to make a strong structure using internal bracing rather than a solid chunk of printed plastic.

Im using ninjateck armadillo with some rudimentary pla settings. No issues with actual print performance, its the slicing or drawing work that I think is failing at the intended output.
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susp arm front 03.stl
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bmz
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Re: Interior structures not printing

Post by bmz » November 9th, 2017, 10:34 pm

2nd pic facing right is the bottom skin. My cross walls clearly visible, and so are the open spaces that should be skinned over. 1st pic facing left is the top side which should show my walls climbing higher, but instead they are getting filled over, except in those open areas where nothing is happening any more.
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IMG_20171109_202727.jpg
IMG_20171109_202712.jpg

bmz
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Re: Interior structures not printing

Post by bmz » November 9th, 2017, 11:00 pm

I think perhaps it needs infill then to support the top skin. But,, why at 0% infill is it just printing solid? Sure a nice honey comb pattern would be great to replace my interior walls,, but thats not what my other parts have had..... Slowly figuring this out, any help greatly appreciated. Thanks!

GrueMaster
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Re: Interior structures not printing

Post by GrueMaster » November 10th, 2017, 9:58 am

I've downloaded your model but haven't had time to examine it yet, beyond loading in Cura. Cura shows support needed on the top flat areas, suggesting that there is something going on in the interior. Are you trying to create your own infill? I would suggest making your design solid where it needs to be, then letting Cura slice and infill accordingly.

I'll know more this weekend when I can fire up Blender and examine the model in more detail.

bmz
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Re: Interior structures not printing

Post by bmz » November 12th, 2017, 11:38 am

I came to a similar conclusion. Today, will be trying out a new cad which has the side areas as an 80% infill, to surround the through holes, and the center as a 20% infill with triangle structure. Would be nice if cura would allow this without jumping through hoops, but its fine. In the end, I have imported two separate stl files, and then made different infill parameters for each before joining on the build plate. Another thing I noticed: would be nice to get a confirmation of saving the separate parameters when finished entering them on cura. As is, the user just jumps from one part to the next with no confirmation. When it comes time to save the joined project, again, there is no confirmation of the new parameters. One would assume that current material parameters would be saved onto the project. The user must then load the gcode to the machine software and observe a layer diagram to ensure that the new separate parameters were saved and utilized. Perhaps its better in newer versions?

GrueMaster
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Re: Interior structures not printing

Post by GrueMaster » November 12th, 2017, 12:58 pm

Cura 3.0.4 should be able to do this, and all versions should show you the resulting print in Layer View. I use layer view to figure out a pause point for doing a filament color change (printing a lid for a Dice Jail now using this technique).

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jonnybischof
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Re: Interior structures not printing

Post by jonnybischof » November 13th, 2017, 5:02 am

cura xray.png
Here's the problem (X-Ray view in Cura shows model problems). There are colliding surfaces inside of your model. You could use the "fix errors" functions in Cura (don't know the newer versions, maybe someone else can help with details on this), but I would strongly suggest fixing the errors in the actual model.

Did you design this model, or is it from the internet?

//
Edit: Looks like this is supposed to be an assembly of multiple parts? Not sure what to make of the model... STLs can be confusing sometimes, as a lot of information from the source file is lost.
Best regards,
Jonny

bmz
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Re: Interior structures not printing

Post by bmz » November 13th, 2017, 9:26 am

I designed it using sketchup. WHen saving in sketchup, it gave an option to fix error, so I did. I guess the errors cura found are different? Will run it through the cura again and see the results of fixing errors. Its kind of a moot point though. I have already moved on from that model, but it would be interesting to have the knowledge to get it to print correctly just to gain a higher mastery of cura and repetier. The new model is going to be using traditional infill in varying densities to make the part stronger, and lighter. I will update when the print is finished.

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jonnybischof
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Re: Interior structures not printing

Post by jonnybischof » November 14th, 2017, 3:44 am

I started with Sketchup as well. Looking at Cura's X-Ray view to find errors and then fix them in Sketchup is a great way to learn how to avoid them!

By the way: I found that - unless the interior structures serve a certain purpose (which they usually don't if they're completely interior) - just designing solid models and printing them with something like 3 perimeter lines (wall thickness 3x nozzle diameter) and 24% infill usually gives you the lowest printing time, lowest weight, AND highest part strength. I once tried skeletonising a complex part which took more time than designing the part itself. It looked great and you'd think it would be very strong, but the printing time was very high and the result really not as tough as the simple version I printed before.

/edit:
I would also suggest moving away from Sketchup when you want to design mechanical assemblies. Sketchup can't handle assemblies well enough and sometimes has issues with dimensional accuracy.. A few years ago I designed a complete improved Ultimaker printer in Sketchup, so I know :)
Best regards,
Jonny

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LePaul
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Re: Interior structures not printing

Post by LePaul » November 14th, 2017, 8:38 am

What are you using now instead of SketchUp? Fusion360?

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jonnybischof
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Re: Interior structures not printing

Post by jonnybischof » November 15th, 2017, 3:33 am

SpaceClaim. It's a professional direct modeling software, comparatively low price ~3000$ (half of what SolidWorks would cost) but absolutely genius workflow. I am privileged to be able to use it at my workplace. Its free counterpart would be 'DesignSpark Mechanical', which is basically an early version of SpaceClaim with old UI and less tools, but similar workflow.
Best regards,
Jonny

bmz
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Re: Interior structures not printing

Post by bmz » November 16th, 2017, 12:34 am

I was initially using a very old version of cura and did not know of options for infill.My first prints were all lines or grid infill, and I could vary the density. Now with newer version of cura, the infill options are more open. Yes, I agree that trying to skeletonize the part was a waste of time! My current setup for the same part did in fact use perimeter walls at 3x line width, and then 25% infill for the less critical areas, and 80% for the strong sections. It came out very strong, but now Im working on visual quality and print speed. The armadillo filament will make strong useable rc car parts for sure, but the visual quality is something to be fine tuned. Im considering trying fusion 360,, its downloaded, and I have a couple drawings from it,, but havent messed with it for 3d printing yet.

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