Inventor users begin by designing parts. These parts can then be combined into assemblies or design within the context of an assembly. As a parametric modeler, it should not be confused with traditional CAD programs. It is used in design and engineering to produce and perfect new products. Whereas in non-parametric CAD programs the dimensions are geometry-driven, a parametric modeler allows the geometry to be dimension-driven. If the dimensions are altered, the geometry automatically updates based on the new dimension. This allows the designer to store their design intent within the model, whereas non-parametric modeling is more akin to a 'digital drafting board'. Inventor also has tools for sheetmetal part creation, welded part creation, and, starting with Version 10, a rendering and animation environment called Inventor Studio based on the mental ray rendering engine.
The crucial building blocks of Inventor are parts. They are made by defining features, which are based on sketches. For example, in order to make a simple cube, a user would first make a square sketch, then use the Extrude tool to make a cube feature out of it. If a user then wanted to add a shaft coming out of the cube, he could add a sketch on the desired face, draw a circle, and then extrude that circle to create a shaft. One can also use work planes to produce sketches that may be offset from the usable planes of the part. The best aspect of this design is that all of the sketches and features can be edited later, without having to redo the entire part. This system of modeling is much more intuitive than in older modeling environments, where if you wanted to change basic dimensions, you would usually have to delete the entire file and start over.
As the final part of the process, parts are then connected to make assemblies. Assemblies can consist of both parts and other assemblies. Parts are joined together by adding constraints between surfaces, edges, planes, point and axes. For example, if one was adding a sprocket onto a shaft, an insert constraint could be added to the shaft and the sprocket saying that the center of the shaft was the same as the center of the sprocket. The distance between the surface of the sprocket and the end of the shaft can also be specified with the insert constraint. Other constraints include flush, mate, insert, angle, and tangent.
This method of modeling allows for the creation of very large, complicated assemblies, especially since sets of parts can be put together before they are joined to the main assembly, and some projects may have many sub assemblies.
Inventor uses specific file formats for parts (.IPT), assemblies (.IAM) and drawing views (.IDW or .DWG - DWG TrueConnect) but the DWG file format can be also imported/exported. Autodesk has been pushing Design Web Format (.DWF) as the preferred 2D/3D data interchange and review format within the Autodesk family of products.
In the last several years Inventor has grown to include functionality contained in many of the mid-level to high level 3D modelers. Inventor uses Shape Manager as its geometric modeling kernel, which is proprietary to Autodesk and was derived from the ACIS modeling kernel.