Onshape is the first sketch/feature based modeler we are looking at in this series. To create a part, you create a 2D sketch to define a feature. Subsequent features are then built on top of one another. This is the same modeling paradigm that is used by many professional CAD programs (Solidworks, Inventor). The thing that really sets Onshape apart from these programs is the fact that it is completely web-based.
In my previous post in the series I talked about my experience with CAD and some platforms that are available for Hobbyists. What I did not discuss was the history of CAD software and some of the key concepts that may differentiate one platform from another. However, I am not going to write the unabridged history of CAD, if you want to read that, I highly recommend going to Wikipedia and falling down the rabbit hole.
First, what do I mean when I say CAD? CAD, or Computer Aided Design, is a rather broad topic. It encompasses pretty much any software that can be used to aid in the process of designing something. This could range from PCB layout software (such as EAGLE or KiCAD) to a 2D drafting package (LibreCAD, AutoCAD, etc) to a full 3D modeling suite (Inventor, Solidworks, Fusion360, etc). I prefer to think of each of these as ECAD, 2D CAD, and 3D CAD respectively. Based on the content of the first post in the series it should be no surprise that when I say CAD I am referring to 3D CAD, or more specifically a 3D CAD modeling package. It should also be noted that there is an entire other world of CAE, or Computer Aided Engineering, software out there. This consists of specialty automated design and simulation software. While CAD software can be classified under the CAE umbrella, I am not going to talk about much about CAE software in this series.