The biggest difference between AutoCAD and Inventor is that all work in AutoCAD takes place on a single plane viewed from one direction, while sketches in Inventor can be made on any plane and viewed from any direction. The multiple planes of Inventor allow three dimensional objects to exist. A sidebar is necessary to organize the multiple sketches and extrusions so that the user can easily navigate their work. Three dimensional objects are most often produced by extruding sketches, the revolve, loft tool, and sweep tool can also produce three dimensional objects form sketches. Other tools like the hole tool and fillet tool can removed material from a shape. Because there are three dimensions, Inventor has more tools than AutoCAD and some of the tools shared by both programs do different things.
Another difference between AutoCAD and Inventor is that Inventor can dimensions objects after they are drawn. I can draw the approximate shape of a sketch and use three dimension tool to constrain the lines to the correct length. I can also constrain lines to be parallel or tangent to other features. Dimensions and Constraints make construction lines unnecessary in Inventor. instead of drawing two lines to position a circle, I can just draw the circle and constrain its position in relation to other features.
I enjoy creating 3D objects in Inventor, but I often find the software frustrating. It sometimes difficult to see and select the proper objects in 3D. If I make a mistake early on it is not easy to fix because many sketches may be dependent on earlier sketches, so deleting a sketch might mean I have to start over completely. If I don't do things the right way, I will run into problems later, so I need to take my time and think about the best way to move forward. In the graphic above, the plate connecting the base at the bottom to the ring at the top was difficult to draw. I knew how tall it was an how wide it was at the top of the base plate, but not at the bottom, so i had to draw it and extend it further afterwards. I initially forgot to extend it down, so there was a hole in the base right below it. I only realized my mistake when I was adding fillets to the edges and an error message displayed. Luckily, I could fix the sketch without starting over.
Once I understood the basic mechanics of the program, Inventor began to make a lot of sense. When I master the new concepts, it will be a powerful tool. Inventor can do for more than AutoCAD because 3D models actually replicate the shape of a part instead of showing profiles from single views.
