Comparing 3D CAD modelers

What designers should know about history-based and "dynamic" schemes Only four steps are needed to generate a 3D part in CoCreate's OneSpace Designer Modeling software: Draw the profile (top left), Extrude it, (top right), Use the blend command on all eight outward edges (bottom right), and Shell the part (lower left). A historytree such as this for a crankshaft in Pro/Engineer tracks all relationships and parameters and stores the order in which designers create features. The tree effectively serves as a part recipe. Changing a step and replaying the recipe forces associations in the history tree to ripple through the model and regenerate the new part. Once a part is built, users need only type in variables to change a pre-programmed model. An assembly was built quickly in KeyCreator without relationships or mating conditions (left-hand image). During design review, a new customer wanted the side of the machine highlighted in orange moved 1/2 in. to the right. To the customer, this represented a minor change. In the manufacturing process, this change could take hours using a sketch-based model with assembly relations. The software accommodated the change with just a few clicks, moving 600 components and changing the length of 28 others (right-hand image). CAD software with what is called a history-based approach to design has topped the field in market share since Needham, Mass., introduced Pro/ Engineer in the late 1980s. About a year ago, Ft. Collins, Colo., started pushing an alternative approach to 3D product development it calls " Dynamic Modeling." This is a proprietary term intended to stress the dynamic — that is, fast and flexible — design the company says its OneSpace Designer Modeling software provides by letting users directly push and pull models to make changes any time during the design process. But terminology brings a potential for confusion. The CAD industry in general uses the term "explicit modeling" to describe methods of directly editing