Help, I cannot figure out how to create solid STL file out of this part

[victor.aminoff]

I recently got a 3D printer and one of the first things I want to do was print some parts for my RC cars. I found an .IGS file of one of the RC cars that I have, it is the whole car with each individual part down to the smallest detail included. I started by isolating the part that I wanted to print (the gearbox) and when I converted it into and STL file it was a complete mess with most of the part missing when I had it in Ultimaker Cura. 

I realised that the problem was that the part is made up of many surfaces, and I mean over a thousand, and from what I have understood they are not stitched together. I have tried endlessly with both Autodesk Meshmixer and Autodesk Fusion 360 to fix the problem both with the original file and the STL. I have been through countless forums and videos, and even though I have gotten just a little bit closer to fixing it I am still very far away. I have managed to stitch the majority of the surfaces together into different groups but I cannot seem to get the whole thing to become one objet. I then tried using the loft tool, but every time I try something, I get an error, I then google it, fix it, and get a new error.

There are a lot of other parts form this car that I would like to do the same with, so a solution to this would be amazing.

I am extremely new to all these applications and I would like to know if there even is a solution, any help would be so appreciated. I am on a Mac so it does slightly limit me to what softwares I can use. 

I have attached the latest STL file of the gearbox below and the .f3d file, I can't seem to be able to upload the original .IGS file since it gives me an error when I try to upload it here, but I would be happy to upload/send it so someone if they would like to see it.

Thank you in advance for the help everyone!

[TheCADWhisperer]

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@victor.aminoff wrote:

I can't seem to be able to upload the original .IGS file since it gives me an error when I try to upload it here, 

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Zip the file to attach here.

Pinging attention of @shaan.hurley IGES (*.igs or *.IGES ) is a common neutral CAD format. (Search Wikipedia if you are not familiar with this file format.)

[WHolzwarth]

Hmm. I've looked at the F3d file without success.

On the other hand, I could grab an IGS of TT-01 Chassis Type E in the net, that's looking better than your F360 file.

Let's talk about your starting IGS.

[hfcandrew]

I opened you .stl in 'Windows 3D Builder' and used the repair tool. I swear this thing is magic, worked perfect. See attached.

[victor.aminoff]

Hi everyone and thank you all for the help, I have managed to fix all the other parts myself, this one was just particularly tricky.