Issue: Volume: 23 Issue: 11 (November 2000)

CADkey Parametrics

By Jeffrey Rowe

I have always liked CADkey because it is a kind of blue collar CAD package. Although it might be unsexy, CADkey can do real work right out of the gate and therefore enjoys wide appeal and a large user base. I have believed for some time, however, that CADkey's lack of parametric capabilities has kept it from being accepted by a wider range of customers. Does every designer need parametric capabilities? No, but parameters are useful for feature-based and/or constraint-based design and modeling. Also, just about every MCAD product now has parametrics, so the capability has essentially become de rigueur.

A few months ago, CADkey began shipping CADkey Parametrics, which fully integrates parametric definition and editing of dimension-driven solid models into the company's CADkey software. CADkey's philosophy and implementation (based on the D-Cubed engine) is somewhat different from that of the competition when it comes to parametrics, however. With the CADkey product, parametrics is an option, not a mandatory requirement for the mechanical product development process. This is a refreshing change from the way much of the rest of the MCAD industry operates. This flexibility and freedom are aspects of CADkey that I've always liked.
With CADkey Parametrics, users can work with a mix of 3D wireframe, freeform, and parametric solids.

Parametrics consist of two basic principles: parameters and constraints. Simply put, parameters are user-defined variables, such as dimensions, that control the shape and size of modeled parts. In component parts, constraints determine how a part's shape or size can change. In assemblies, constraints define associative links between parts that control their locations relative to their placement within the assembly. Constraints come in two basic flavors: geometric and dimensional. Geometric constraints control the shape and relationships between lines, arcs, and so on, whereas dimensional constraints control the size of the geometry.

Unlike some modelers that require you to create parametric models from scratch with little regard for legacy data, CADkey Parametrics lets you convert existing data or import wireframe data into sketches and constrain them automatically. This seemingly simple ability lets you go from 2D to 3D in a relatively painless manner. It also reinforces an underlying CADkey strength: interoperability.

You can edit solid models relatively easily with CADkey Parametrics because you can access all the values used to create the models, as well as the interactions and relationships between sets of features and parts in assemblies. For example, you can change the radius of a multi-edged filleted feature by selecting a blend face and entering a new radius value. Modifying groups of parts with mating relationships can be accomplished by changing a single variable. During design editing, dimensional and geometric constraints, such as coincident, tangent, parallel, and equal size, can either hold or drive the form you want in a sketch profile. You also can add to and create parametric features from non-parametric solids.

As important as the ability to create and edit parametric features is, feature suppression is also an important consideration when modifying and regenerating (or redisplaying) models, and CADkey Parametrics does a decent job of this. Feature suppression can accelerate the display of large, complex parametric models by letting you temporarily turn off individual or categories of detail-level features, such as fillets or small holes that are less important to the "big-picture" visual display clarity of a model.

CADkey has extended Parametrics' capabilities to production drawings and printing as well. For example, you can automatically create a set of prints for a family of parts by modeling and detailing one parametric model. Adjusting the de sign parameters transforms the model, and the layout automatically updates.

CADkey Parametrics has been a bit long in coming, but its implementation and capabilities have made it well worth the wait. In fact, the only real limitation with the program is its sketching capability, which tends to be a bit labor intensive because you have to "overdraw" things and then trim to get the sketch outline that you want. Also, complex blend capabilities are not as comprehensive as they could be, but they are on par with those found in competing products, such as SolidWorks and thinkDesign. Although it doesn't break any new ground in terms of parametrics, it is certainly a welcome and useful addition to the CADkey flagship product and should find a home on the desktops of many CADkey users, as well as appeal to potential new users.

Jeffrey Rowe is a mechanical design, software development, and technical writing consultant. He can be reached at

Price: $1195
Minimum system requirements: CADkey 99; Windows NT/2000; 300MHz Pentium; 128MB of RAM; OpenGL video card
CADkey Corp.
Marlborough, MA