Machine Design

How to model massive assemblies

The UGS Velocity Series software for the mid-market includes Solid Edge, NX CAM Express for generating toolpaths, Femap for FEA, and Teamcenter Express for collaboration.

—Raymond Kurland

Each program is modular and swaps data with the others. Solid Edge V20 runs on Microsoft Vista, adds more support for 64-bit processors, includes over 170 other new enhancements, sports a new Catia V5 bidirectional translator, and imports STL files for viewing.

Overall this is an impressive release. Many of the major modeling functions added to V20 focus on improving the ability to work with massive assemblies (more than 100,000 parts). This is a tough problem, often taxing the resources of even the fastest desktop processors. Solid Edge V20 has made substantial progress in this area and now has leadingedge capabilities. A few of these include:

Zones modeling, which improves performance by letting users define and work in small areas of large assemblies, without opening the whole assembly. Zones, thus, cut design time, speed system performance, and make working with massive assemblies more manageable. Zones are created several ways. For example, a user can select several parts to make a zone. The box-shaped area defined by the outer limits of the parts make up the geographical space of the zone. To work on different portions of an assembly, the user switches zones.

Assembly auto(mated) constraints allow rapid constraining of imported assemblies for motion studies. The feature performs in minutes what would normally take hours to do manually.

Component grouping allows better design control, yet does not effect how the assembly is physically constructed. Simplifying the pathfinder (history tree) yields more productive modeling because of the simpler presentation. Users can select components to form groups and then Move, Copy, or Rotate them while maintaining the internal mating relationships. (An option also allows deleting relationships.) Building digital versions of large machines frequently requires duplicating subassemblies, so this wellthought-out capability serves to speed modeling. Additionally, a Group feature lets users group parts that might not be thought of as a subassembly, such as all similar bolts. Then the group can be worked with commands such as Activate, Inactivate, Hide, Show, and Move Multiple Parts. Groups are invisible to the Draft environment, so BOM structures are unaffected.

Drawing review mode offers a complete visualization of massive assemblies in seconds, not hours. It is possible because Solid Edge stores independent drawing data. In addition, 2D drafting in V20 makes working with massive assemblies easier. Instead of many minutes to open a drawing of a severalthousand-part assembly, it takes about 6 seconds to open the same drawing in inactive mode. Users can even view and print inactive drawings, add dimensions and annotations, and add and remove BOM balloons. Having an independent copy of the 2D drawing derived from the 3D model also lets users open drawings when a 3D model is not found, or worse, inadvertently deleted.

V20 also speeds performance of fully active assemblies by inactivating (converting to a light-weight view) parts not recently used. User interface changes include: a dynamic preview of direct edits that shows what a change would be before it is made and committed, saving valuable design time, generating automatic tabulated drawing views for families of parts, and feature library helpers that displays explanations of how features are to be placed.

Goal seek, feature grouping, feature library helpers, and the variable rule editor all act to improve engineering productivity. Goal seek presents a simple solution to a vexing problem, eliminating trial-and-error solutions in many cases. For example, using a Sketch layout, users might vary a dimension (goal seek) while the software computes another parameter. Common tasks might include determining pulley locations from fixed belt lengths or solving for areas when changing a boundary dimension. 2D sketch geometry can also drive the size and position of 3D components.

A relationship assistant helps when migrating legacy data or working with imported assemblies where constraints need to be added for use in motion studies. Instead of a tedious manual process, the relationship assistant groups components and then computes possible mating relationships. Dialog boxes show relationships it has found, letting users accept or reject a particular relationship. In one example, the assistant took only 5 minutes to add about 50 relationships instead of an hour or more if done manually. I have not found this useful feature in any other software.

V20 comes from UGS PLM Software, 5800 Granite Pkwy., Suite 600, Plano, TX 75024, (972) 987-3000,

Raymond Kurland is president of TechniCom, a firm that specializes in analyzing MCAD and PLM software. Reach him at [email protected]

The Group feature creates an Assembly Group of gripper components for operations such as Activate, Inactivate, Show, Hide, or Move Multiple Parts. Making Groups like this can simplify the history tree (pathfinder).

A belt and pulley layout shows the tensioner pulley location being driven by the assembly sketch. This is an example of what Solid Edge calls its hybrid 2D-3D method.

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