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How to change STL faceting of flat circular surfaces

Regular Member

How to change STL faceting of flat circular surfaces

Hello everyone, (First Post Ever Alert)

I make a lot of STLs for rapid prototyping and for fea, I want the stl triangles to be arrayed around the center of circular flat surfaces, the way they are when created in DEFORM (http://www.deform.com/).

The only way I have now, is to make all the surfaces either slightly concave or convex. Which works, but sometimes causes issues with the models.

stl_flat.jpgstl_concave.jpg

Thanks for any suggestions!

34 REPLIES 34

Re: How to change STL faceting of flat circular surfaces

From my many year of rapid prototyping, the triangular pattern on circles have typically been like your picture on the left irregardless of software. I am not sure how the algorithm is written for developing the triangles. If you change your resolution sometimes it will modify how the triangle are made.

Re: How to change STL faceting of flat circular surfaces

Back to Dale,

It's nice to know it's not just me.

The only reason I really care, is that in the fea program DEFORM, the mesh is created from these stls and the pattern on the end faces make the mesh behave poorly; which is the reason I do the models with concave/vex surfaces.

The DEFORM software makes stl models like the picture on the right, but I think everything is considered a simple revolve, so that is most likely the reason.

Thanks for your response.

Re: How to change STL faceting of flat circular surfaces

See how the VRML export does the faceting. If it is more to your liking, you can then import it again and the STL should now follow the VRML facets fairly closely.

I have a feeling that the "layering" of the facets in STL is probably intentional as the STL process is cone by layers rather than logical facet divisions. If the above test fails, it is very likely that this is the case and should be considered an enhancement to a generic STL generation.

Have you looked to see if there are options in the STL export?

Re: How to change STL faceting of flat circular surfaces

Back to Antonius,

I do like the VRML export better, but after importing and exporting as stl, the results are about the same.

I may have to live without having flat endfaces on my cylinders.

I have looked for STL options, but I haven't found any more than are in the export window. I may do more searching.

My next step is to send it to support and see if they can help (or maybe add it as an enhancement, sometime).

Re: How to change STL faceting of flat circular surfaces

Here's the thing, if it's a flat surface, the triangulation is completely irrelevant. Really. ONLY if there is some curve to a surface will it matter. In your case with a flat surface and the splined hole, only the amount of triangulation where the spline intersects the surface matters, not the look. The flat surface will ALWAYS be flat, it's just how accurate does the curve on the spline need to be, because the amount of segments where it intersects the flat plane is what determines the accurace longitudinally down the splined hole.

I would NEVER make what should be a flat surface concave or convex simply to make the file look better. The system knows what it's doing, don't worry about it. I've never had an issue and I worked at a place with 2 SLA machines I used constantly for about 2 years.

I haven't created an STL in creo yet, but there should be (read: WAS) settings you could set for, if I remember, chord angle and chord height. They or similar should still exist, just look for them when you create the STL file.

Best of luck.

Re: How to change STL faceting of flat circular surfaces

Its probably still the same Frank...

stl_dialog.JPG

Re: How to change STL faceting of flat circular surfaces

Back to Frank,

True, it is flat as an STL. But, it does make a difference in my FEA analysis program (DEFORM) how the triangulation is oriented. When the mesh is created with a curvature bias, the mesh is definitely affected by the triangulation. The STL models created in DEFORM do not have this issue, and the mesh looks very good.

You are right about the settings for creation, they have even added a few more options, but they don't help my issue. I've been making a lot of STLs for quite a while, so I am familiar with controls, I'm just not happy with the method.

I have a call in to tech support, I will let everyone know if I ever get a better solution than my current workaround (no flat round surfaces)

Re: How to change STL faceting of flat circular surfaces

Frank,

I should have been a bit more clear in my original post, sorry. I don't do this often.

These pics might have helped explain why I would like a different mesh generation.

creo-mesh.jpgdeform-mesh.jpgcreo-stl.jpgdeform-stl.jpg

Re: How to change STL faceting of flat circular surfaces

Sorry, I didn't catch the lower-case "fea" in your post. Why not let your analysis program make the mesh? We have Mechanica and Ansys here and we always let the FEA program mesh it. Is there a reason you're trying to use an STL mesh for FEA?