"Triangles with mixed winding order found" error

Hi everyone,

I was recently attempting to upload an stl and got the "Triangles with mixed winding order found" error. I'm a pretty experienced Netfabb Pro user and tried all the fixes with no success (self-intersections removed, piece booleaned into a single shell, etc).

Has anyone else ever run into this? Even the support staff member who emailed me said she didn't know what it meant!

I saw one other post on this subject, but that was a beginner with a problematic mesh, and mine looks clean as far as I can tell...

In Netfabb, did you apply the "Flipped Triangles" repair?

That's usually the cause of this message.

I did already, I'm afraid. Netfabb is showing 0 triangles with invalid orientation. Thanks for the suggestion though, good to know it could be a normals issue...

I had this issue with a model a while ago, always got the "triangles with mixed winding order" message, despite the model showing as fine in Netfabb and watertight in Accutrans. The really confusing thing was that the faulty model was a slight modification of one that went through without problems.
In the end I discovered a hole hidden inside the model, and when I fixed it manually the model uploaded successfully. The hole had been auto-fixed by Netfabb, and was present and didn't cause any problems on the original model, so I'm not entirely sure why this solved the problem, but it did.
So, possibly there is a hole somewhere that is mysteriously causing the problem despite it apparently being fixed by Netfabb?

One thing that Netfabb on Shapeways does is it also unions all the pieces that are touching.
This is so you don't get charged for the overlapping volume.

Netfabb basic doesn't have that function, so that might be why you get some extra error messages from Shapeways.

Sounds like you figured out what your issue was, so that's good.

Netfabb Basic doesn't union shells, but Netfabb Cloud service - http://cloud.netfabb.com/ - does so very neatly and is well worth using at any time before uploading -

DIdn't the OP's issue used to be called a 'winding check error'? - I used to get that quite regular attempting to upload a .dae file before I figured out to convert to and check everything as an stl file for non-colour models.

Thanks for all the thoughts, everyone!

I am actually using Netfabb Pro already. I'm still stuck unfortunately. I may just have to go back to an earlier version of the file and see if Shapeways will accept that.

I had this same error today and fixed it by running a boolean union on the finished part in Netfabb Pro

this operation removes self-intersecting portions

Cool, I'll try that, thanks for the tip

Sophie, are you still having issues with the file? If so, can you send me the file to look at and analyze? Since we are always trying to improve the acceptance rate of uploads, this will also give us another data point on error files.