AnyCAD is Inventor`s ability to work with and exchange data from a variety of sources. And not only with 3rd party formats, Inventor talks with AutoCAD, Revit, Fusion 360, and other products within the Autodesk family.
Paul Munford once described Fusion 360 as Inventor’s little brother. This comparison makes sense as Fusion is the new kid on the block, shares many similarities to Inventor, and they are both in the same Autodesk manufacturing family.
So as Inventor and Fusion are in the same family, it would be appropriate that they can read each other’s files? Right? Put on top of this Inventor’s AnyCAD and Fusion 360’s openness to data and it seems like the start of a beautiful relationship.
Inventor to Fusion 360
Fusion 360 offers the ability to open Inventor parts (IPT) and assemblies (IAM) directly. After selecting the file the upload process begins, which you can dismiss and allow to complete in the background.

The imported model is NOT associative to the original, meaning changes within Inventor will NOT update the model within Fusion 360.
Parts
Fusion treats an Inventor part as it would other 3rd part files (like STEP). Even though the Inventor model is fully featured, it imports as a single bodied part with no features. The result is similar to what occurs when modeling within Fusion with History turned off.

Fusion 360, however, will import a multi solid body Inventor part file as a multi-body design. This is good as the flow between bodies and components within Fusion 360 kicks butt.

Even without the features (history), you can use the editing tools, like Press Pull, to make adjustments to the model. Also, there is no limitation in adding features.
By default, capturing design history is disabled. You can (via the browser) enable Capture Design History. Therefore any feature added after will be captured in the timeline.

I’ve found that the import process does not honor the orientation within Inventor. So, in most instances, I need to use the ViewCube to set the Front (or Top) view.
Assemblies
For Inventor assemblies (IAM), I find it easier to upload the model through the data panel.

A big must-do with assemblies is you must upload all the related components simultaneously. Because of this, Autodesk highly recommends doing a pack-and-go from within Inventor first. Then use the pack-and-go to upload into Fusion, ensuring you have all the bits-and-bites.
Fusion 360 to Inventor
Fusion stores its designs in the cloud. Not really files, designs are a collection of 0’s-and-1’s bound together. To get the design out of Fusion and into your Inventor, you need to export it.

Fusion provides an export option of Inventor, both parts (IPT) and assemblies (IAM). The type of design sets the default export, but you can set the extension when selecting the export location.
As the process may take time, it goes into the queue. You can dismiss the Job Status window and continue working. It will let you know when it’s done.

With assemblies, Fusion exports a ZIP which is a collection of the assembly and the components for the assembly.
The exported Inventor data is no different than what would come from a third-party (SolidWorks, Creo, STEP, etc) in that there are no features nor assembly relationships. However, it does maintain the assembly hierarchy structure and Fusion meta-data.

Wrap Up
Hopefully, you can see how easy it is to exchange data between the two systems. Fusion 360 opens Inventor natively, without the need for translation or export. Fusion exports data into the Inventor format, again meaning no third-part-neutral-intermediate.
It is important to remember that the data is non-associative. If the model changes in either application you’ll need to re-import/re-export.
Features do not translate, however, you can tweak the models once opened in the other application. In addition, add features to your heart’s content.
Assembly component relationships are the real downer, although more importantly missing within Inventor. As the components are located in the correct location, ground them to prevent them from inadvertently moving. Constrain only what you are changing or need to move.
Use this workflow when you are not intending for the data to come back. It works well for tossing the part over the fence, for use in the other application.
Next time, I’ll dive in and attempt to set up an associative relationship between Inventor and a Fusion design.