Imported .step file in Simulation Mechanical appears distorted

[sanziana_moldoveanu]

Hi! I am having an issue with an imported .step file from Fusion 360 to Simulation Mechanical. I don't know where the problem lies if it's in one or the other program. I will attach a photo so you have a better idea of what it's happening. Basically I reconstructed a mandible section using sketches and loft command and then split the body to model the implant site. Then exported as a .step file and imported in Simulation Mechanical. The model appears just fine in Fusion 360 but appears distorted in Simulation mechanical. What do you think is the problem? 

[TheCADWhisperer]

Change the threads to cosmetic.

Can you point to any reference that recommends using modeled threads in any analysis software?

There might be other issues going on here - but that is where I would start in idealizing the geometry for analysis.

Can you Attach your *.f3d file here?

[sanziana_moldoveanu]

Thanks for the response!

Unfortunately, I need to have a modeled thread. The thread of the implants positioned has a special design. 

I have read about the pros and cons of cosmetic and modeled threads but for this project, I can only use modeled threads.

https://caeai.com/blog/detailed-modeling-threaded-connections

I have attached just the part with the problem. Can you think of any other solution? I feel like it's a glitch that happens sometimes because I had this problem before and I just moved a bit the implants, resplit the bodies and voila, it worked! I have tried this method this time but no luck.

[TheCADWhisperer]

I have just started experimenting with this - first thing I would do is move to symmetry about the origin.

I have seen unexpected results in multiple CAD softwares when object is a long distance from the origin.

It doesn't appear excessive in this case, but I would move and check the export again.

[TheCADWhisperer]

It will be a while till I can get back to this - but I ran a Quality Check in other software and found two issues.

[John_Holtz · Accepted solution]

Hi @sanziana_moldoveanu 

Have you tried any of the other formats that are common between Fusion and Simulation Mechanical, such as Inventor files, IGES files, or SAT files? Perhaps one of those formats will work better.

What I see in Sim Mech is that some of the spiral surfaces along the threads are not coming in properly or are not meshing. So perhaps it will work (or work better) if you split the threads in half -- either into left and right halves or top and bottom halves. Instead of having one surface on a spiral that makes 3 or 4 complete turns, maybe a spiral that makes a half turn (split left-right) or 2 turns (split top-bottom) will work.

[sanziana_moldoveanu]

I have moved all the parts close to the origin but still, get the same distortion. In regards to your second post, I think that one is too advanced for me. 

[sanziana_moldoveanu]

I exported as a .IGES file and it actually crashed my Simulation Mechanical program but .SAT worked perfectly and did not distort parts. So I guess .SAT is the way to go. For now it works. I will report back if I have any more issues! Thanks a lot guys!