Broken stl from very simple part

[Stu3d]

Hi, first forum post but used search to solve previous problems.
2d cad user for 30+ years. Have used Alibre for 5 years (started with Geomagic), currently V22. Generally produce parts for 3d printing.

I wanted to create a very simple adaptor from old slightly larger square rainwater downpipe to modern square pipe.
I drew a square and radiused corners.
Did same on a new plane 30mm away but larger.
Lofted the two sketches together.
I then projected the sketch and extruded it each end.
I shelled the part to 1.9mm wall thickness and finally removed the bottom to create a hollow adaptor.

An extremely simple part that took couple of minutes however when I export to stl it has the lofted middle section missing in my slicer, Simplify3D.
I have produced 100s of parts and never had a problem before. Does stl export dislike loft, I rarely use it?
I tried checking the stl in Netfabb, which I haven't had to do since I started using Alibre, and it said invalid stl file.
Very puzzled, any ideas anyone?
Thanks, Stuart.

 

[jfnewman]

You are correct in Cura the loft is missing.

 

[Stu3d]

You are correct in Cura the loft is missing.

Thanks for taking the time to check the part in another slicer.
I think I will draw some quick simple parts using loft tool to see if problem is repeatable.

 

[TonyF]

I had this same issue with lofts, I had success with exporting it as a step, then reimporting it, then export again to a stl. Its not Cura, but the stl export settings in Alibre. Alibre has a difficult time resolving overly constricted settings

I opened a case with Alibre, they asked me to change my stl export settings, I did and it worked fine. Try something like the attached image.

 

[jfnewman]

I had this same issue with lofts, I had success with exporting it as a step, then reimporting it, then export again to a stl. Its not Cura, but the stl export settings in Alibre. Alibre has a difficult time resolving overly constricted settings

I opened a case with Alibre, they asked me to change my stl export settings, I did and it worked fine. Try something like the attached image.

I tried the step route as well and the step file around the loft area was incorrect I will try those settings and see if that makes a differences.

 

[DavidJ]

Are you sure that the radii are correct on the corners? If I swap the radii size on the 2 sketches for the loft, then the STL turns out OK in Netfabb. It may be that the current geometry is just 'difficult' for the loft or shell function. Might take more digging to work out exactly what is causing the problem.

I'm not sure why you used an extra cut to remove one end - you can remove more than one face with the shell command.

 

[DavidJ]

Did a bit more looking - adding some fillets at the transitions removes the problem with the STL export.

 

[Stu3d]

I had this same issue with lofts, I had success with exporting it as a step, then reimporting it, then export again to a stl. Its not Cura, but the stl export settings in Alibre. Alibre has a difficult time resolving overly constricted settings

I opened a case with Alibre, they asked me to change my stl export settings, I did and it worked fine. Try something like the attached image.

The step file solution worked a treat thanks. The stl settings crashed Alibre so will experiment.

 

[Stu3d]

Are you sure that the radii are correct on the corners? If I swap the radii size on the 2 sketches for the loft, then the STL turns out OK in Netfabb. It may be that the current geometry is just 'difficult' for the loft or shell function. Might take more digging to work out exactly what is causing the problem.

I'm not sure why you used an extra cut to remove one end - you can remove more than one face with the shell command.

The stl file was fine when I removed the radii so it wasn't the loft alone causing my problem.
With the radii included I found something odd. When I project to sketch one end of the loft the 8 edges/radii are selected together with one click, when I project to sketch the other end I have to select the 8 items individually!

Thank you for the shell tip, in the past I had tried using the overrides settings on the right to achieve this without success. It seems so obvious now!

I opened the filleted Alibre part you posted in your other reply and fillet 9 seemed to be broken but I will experiment, thank you.

 

[DavidJ]

That 8 items thing seems to be a weakness of the preview. The fillet will still work if you only select 1 edge, though it is a bit odd that it shows that way.

Fillet 9 looks OK on my system...