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lee

Sketchup export - Cura not printing what it should

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Im using Sketchup (as its easy to use) to make a part for our toilet and the flush is broken...

basically ive created a hollow thread screew exported to stl then open in cura...

cura shows exact what i have created... but when i hit print, its prints the screw a a full screw instead of a hollowed out middle... why does cura 'show' the hollowed out centre but print something completely different =/

ta

Lee

 

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Do you have some of the 'fix horrible' settings enabled in 'Expert Settings'? Those are intended to fix bad STL's with overlapping parts etc.

If not, then it's something about how the STL is set up that is confusing Cura. You might try running it through Netfabb Basic, or their cloud service, and see if it finds problems to fix.

 

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I use sketchup quite a bit. Unfortunately it's too easy to create internal faces or holes in a face which confuse slicers.

The way the slicer works mostly is it finds the intersection of a plane with every (every!) polygon in the stl. This results in many unconnected lines. Then it looks to see which lines end at the same point and tries to create a loop. If it can't create a loop and if you didn't check any of the "fix horrible" checkboxes then it discards that. Then it takes the loops and figures out which loops represent an external wall and which an internal "hole" in the part.

Anyway the point is your model must be perfect for this to work. If 2 polygons don't quite meet then it won't work - one of the fix horrible will assume lines touch if they are "close enough". Other's try to repair holes and other mistakes.

If you view your part in cura in the "xray" view it will show most of the problem areas in red. If you see any red at all I recommend going back to sketchup and fixing those spots.

You can also try this which removes internal surfaces (but can remove important surfaces also if you aren't careful:

http://meshlabstuff.blogspot.com/2009/04/how-to-remove-internal-faces-with.html

But again - it's not just internal faces that are a problem - it's also holes in your surface that mess up the slicing of layers that intersect the hole or gap.

 

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Your STL model isn't a solid object - the walls have no thickness; it's just an outer surface, that's completely open at one end, and has a ring at the other end.

Take a look at it in Meshlab or netfabb to see what's going on.

You need to model the inside thickness too. Perhaps you need to union the parts together better in Sketchup to give a single solid object?

 

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You want this part completely hollow? What's the wall thickness?

I used NetFabb to "fix" this and got a solid object. What you can do in Cura is select 0% infill to print a hollow part. I think the top and bottom should also be 0mm if you want the top/bottom as holes. I would also do a brim support, that prints.. well.. a brim around your object so it adheres to the platform better while printing.

I used those settings in this print: http://iama3dprinter.tumblr.com/post/62926508437/julia-vase-002-flow-by-virtox

Solid file for your bolt: https://www.dropbox.com/s/aetwjlr49u3a1su/toilet-bolt-solid.stl

 

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i only wanted a few layers to print to see if i got the size right.. as the hole in the toilet is 41mm in diameter. But when i saw the whole of the bottom start to print i was confused... yes nancy i 'expected it to print like your vase, and then cancel print after 3-5 layers.

i need the hole in the centre to only be 10-20mm vacant (it isnt exact)then a 7mm pin hangs from the button... through the tube/screw and then connects to a lifting leaver

 

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But when i saw the whole of the bottom start to print i was confused.

 

I know the feeling. I always look at Cura "layer view" before printing. Carefully. I sometimes zip through every layer 5 or 6 times looking at it from a few different angles and staring at a different portion of the part.

 

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Nancy already answered your question. Your walls MUST HAVE THICKNESS.

Do you understand?

For example if you wanted a hollow vertical cylinder/tube you would need to have TWO cylinders - one inside the other to represent the inner and outer walls. You would also need a "ring" at the top and bottom to represent the top and bottom of the solid area.

So as this applies to your bolt.

Put a top and bottom onto your bolt. That will make it a solid object. If you really want it hollow then you can tell cura not to print a top and bottom (two seperate checkboxes and you can tell it to do zero infill. But the model must have a top and bottom. Or you can do it the hard way and give your walls of your bolt some thickness. Make it at least .8mm thick if you go this harder route as Cura usually won't slice walls thinner than .8mm.

 

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Or you can do it the hard way and give your walls of your bolt some thickness.

 

Just to explain further, this is difficult in sketchup (unless there is some plugin I don't know about). You would have to probably duplicate the threads and shrink the copy and then put the copy inside the larger threads where the smaller threads would be the inner wall. Then you would have to give your threads a top and bottom. For me this would probably take hours.

Much easier to give the threads a top and a bottom. Also I recommend "spiralize" if you want it hollow and I recommend lowering the part below the bed a bit (in cura quality settings) and also make the shell thickness between .4 and .6mm only (any thicker and spiralize doesn't work so well).

 

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I imported the STL into SpaceClaim, and managed to hack up what I think you wanted: a threaded rod with a hole through the middle. I had to chop half a mm or so off each end to get rid of some broken geometry, and give a flat surface at the open end of the spiral. The STL is attached, in case its any use to you.

These two screenshots of Meshlab show the differences between the your original file, and the new one:

Open Surface

 

Properly Closed Solid

 

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