An independent user survey found that Cadkey users did not want to be forced into a parametric solid-only system nor give up the freeform design tools that they know. So Cadkey Parametrics was developed as an integrated enhancement product for those who can truly make use of the technology.

The software significantly expands the hybrid modelling approach with a high level of interaction between traditional 2D drawing, wireframe, freeform solid, surface and feature-based modelling. Functions in this new product can be accessed in a number of ways including hotkeys, icons, toolbars, classic mode and an optional new folder tree and pop-up menu system. The major time saving advantages to adding Cadkey Parametrics to a current toolkit can be separated into three benefit categories: feature-based modelling, hybrid parametric and sketching/constraining.

Feature-based modelling

Cadkey Parametrics makes editing solids easy, with full access to values used in each model's creation and interactions between sets of features and parts.

Changing the radius of a complex multi-edge fillet feature is as simple as selecting a blend face and typing in a new radius in the dialogue as shown in Figure 1. In this case the parametric fillet feature had been previously added to the imported nonparametric solid shown.

Changes to a group of parts with mating relationships such as the shaft, bushings and block (Figure 2) can easily be driven with a single variable. Updating mating parts this way saves time and more importantly, prevents errors that can result by editing each separately.

The creation of a set of prints for a family of parts can be automated by modelling and detailing a single parametric model. Adjusting the design parameters transforms the model and causes the layout to update automatically. This approach also prevents errors, saves the time in redrawing the other members of the family and allows changes to be propagated through the whole family, saving even more editing time.

Another advantage of feature-based modelling is suppression which significantly accelerates the display of large parametric models by temporarily turning off individual or categories of detail-level features, such as fillets or small holes that are unimportant to the visual clarity of the model.

Hybrid parametric

Typical midrange parametric solid modelling software forces users to completely rebuild legacy data in their own proprietary feature-based format before any changes can occur. Because of Cadkey Parametrics' hybrid abilities, there is no need to rebuild existing or imported solids. Parametric features can be added to and created from nonparametric solids. This integration still allows the nonparametric portions of a model to be edited with Cadkey's face modification functions.

Features such as the mould cavity (shown in Figure 3), formed by subtracting the volume of an imported nonparametric solid, will update automatically if the imported solid is replaced or modified. The position of features such as water lines dependant on the cavity will also update appropriately or provide feedback if conflicts arise. This capability allows contract manufacturers to quickly re-apply value-added changes to a customer's design if or when a new version is received.

Hybrid parametric modelling allows standard design features such as a bolt pattern for a model motor (shown in Figure 4), to be stored as a library of solids in industry-standard file formats like SAT, XT, STEP and IGES. This approach allows the library to be shared with other users and CAD systems.

Designers experienced in parametric modelling will appreciate that many complex models with hundreds of features become very difficult to work with due to congestion in the feature tree. In many cases significant numbers of design features do not require parametric editing or definition. Cadkey Parametrics provides a solution to these issues by allowing sets of features to be defined as a single nonparametric solid feature.

Sketching/constraining

Special sketching tools in Cadkey Parametrics offer major enhancement to the basic task of two-dimensional drawing and can be applied to more than just solid modelling.

Sketch entities and dimensions utilise animated 'click and drag' placement and editing capabilities resulting in improved visualisation and a reduced number of menu selections.

Dimensions and geometric constraints (like coincident, parallel, tangent and equal size) hold or drive the desired form of a sketch profile during editing. Ordinarily a sketch would be extruded or swept to generate a solid but not every part design or engineering task requires a 3D model. Sketching also provides a quick means of creating simple 2D drawings (see Figure 5). Intelligent associativity between 2D orthographic views can be constructed using constraints, so that changing the value of a dimension will update all views that are effected.

A constrained 2D sketch can be used in the study of multilink kinematic mechanisms. In the sketch (Figure 6), grabbing the link on the motor and dragging it in a circular path will animate the range of motion of the whole linkage.

Existing or imported wireframe data can be quickly converted into sketches and automatically constrained. Years of legacy CAD data can be re-used in this manner to speed up the redesign process by aiding in the creation of adjustable parametric solid models.

Mecad Systems

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