Geometry Preparation Tool for Thermal Desktop®

Product Overview

CRTech SpaceClaim eliminates analysis bottlenecks created when CAD-based design geometry is not directly accessible, or when it is too detailed for simulation purposes, or when equivalent geometry cannot easily be generated by a thermal/fluid engineer who is not also a CAD specialist.

For example, perhaps a CAD model has been created by a different organization such that the analyst does not have access to the same CAD software version, or perhaps the originating organization does not wish to release the design in the original CAD format to protect proprietary information. In either scenario, the organization may release “dumb geometry” such as STEP, IGES, or ACIS. Almost any translation eliminates the history of the part, leaving the analyst with bodies, faces, lines, and vertices. Traditional CAD systems rely on the history to be able to parametrically modify the geometry. However, with CRTech SpaceClaim, features are automatically recognized, and even "dumb geometry" can be parametrically modified. In fact, parameters may be arbitrarily added by the user to modify any aspect of the geometry, completely independent of how the geometry was originally created.

Any CAD conversions could also result in small surfaces and slivers, gaps between surfaces, and interference between components. Such defects can prevent surfaces from closing as a solid, and can defeat even the most advanced meshers.

Even without these geometric defects, the original CAD parts and assemblies were intended for manufacturing, not for analysis. Midsurfaces must be created when 2D meshes are preferable to 3D meshes. Planes of symmetry must be cut. Such simplifications are not possible in many CAD systems. Furthermore, unimportant holes, fillets, welds, etc. must be removed or defeatured, but to remove them they must first be recognized as design features. In the past, such defeaturing was only possible if the analyst owned and was trained in the same CAD software that the design engineer used, and if the design engineer use good modeling practices.

SpaceClaim Corporation’s SpaceClaim Engineer® is devoted to CAE preparation from CAD models. It can read native CAD files for most available formats, including STEP, IGES, or ACIS. It recognizes design features for any type of imported file, and analyzes geometry in order to automate simplification and healing operations. Imported geometry can be easily modified, and new geometry can also be added quickly using “push-pull” techniques that eliminate the need for extensive training and tracking of part histories. CRTech SpaceClaim extends this product with features appropriate to thermal modeling in general, and to Thermal Desktop specifically.

Additional Information

• For a quick example, click here
• For a detailed example, click here
• Visit SpaceClaim web site
• Top Ten Reasons to Use SpaceClaim Direct 3D Modelling

 

Introduction

CAD to CAE Bottlenecks

Parametric or history-based CAD modeling allows complex parts to be constructed algorithmically: a “recipe” is created by the designer. For example (in English): “Extrude this rectangle along an arc to create a solid, then cut a hole through the side, then chamfer the edges of that hole, then round the edges of the top and bottom faces that resulted from the extrusion.” In essence, the designer is creating a computer program (the history or “recipe”) complete with variables or parameters for each step. History-based modeling is extremely popular with designers, in part because the part construction often mimics manufacturing steps.

Unfortunately, an analyst who inherits the design drawings must learn the CAD system and each part’s recipe well enough to “roll back” features such as chamfers and small holes that disrupt meshing, or that slow radiation and convection solutions. Even then, some features cannot be easily removed, and some CAD systems don’t provide defeaturing tools critical to thermal analysis such as midsurfacing, or they don’t allow the analyst to store their simplified representations along with the detailed manufacturing drawing.

And that is the lucky analyst who has access to the same CAD software used by the designer, and was willing to be trained in that software and use it often enough to retain the necessary skills.  For some analysts, this meant acquiring licenses and maintaining their skills in multiple CAD systems. Nonetheless, this situation is appropriate for a designer who does occasional analysis, or for certain manufacturing applications where modification of the design geometry is either not possible or not desired.

For the remainder … for the unlucky analysts who cannot share the same CAD system or who do not have access to the native part and assembly files … the situation is even worse. To start, the “recipes” upon which the parts are based are intentionally unavailable outside the native CAD system (in part to prevent an organization from easily changing to different CAD software). Often, the organization originating the part often considers the design proprietary and will release only “dumb geometry” such as STEP, IGES, or ACIS files. Either way, not only are all recipes lost in the process (including identification of features such as holes, fillets, rounds, and chamfers), but defects in the geometry are generated as well, such as gaps and slivers.

The bane of the thermal engineer is receiving a detailed STEP or IGES file that cannot be defeatured, manipulated, or healed, and which often cannot even be closed as a solid. Thermal Desktop’s snap-on simplification, using the “dumb geometry” file as scaffolding, is very popular in such cases. The addition of CRTech SpaceClaim to the process of preparing Thermal Desktop models provides revolutionary advantages over that prior state of the art, as will be explained below.

Direct Modeling Technology

While driving dimensions can be specified parametrically in CRTech SpaceClaim, it is not a traditional history-based CAD system. Instead, it is a newer direct modeling system. In a direct modeling system, geometric components are still accessible and organized in tree-like structures, but there is no recipe because there is no need to know any recipe. Part dimensions and features can be changed directly, at any time, and in any order.

This method is possible because a direct modeling system is perpetually analyzing the topology of the model and the intentions of the designer. In a nutshell, it recognizes and “understands” the geometry, rather than blindly following a recipe. Direct modeling is like a grammar-checking word processor … versus a typewriter.

Direct modeling was introduced to try to make CAD modeling simpler and more accessible, and it certainly achieves this goal. Direct modeling is very easy to learn, use, and retain. Arguments over whether it is enough for all CAD applications abound on the internet, and it is unlikely to replace parametric or history-based modeling in all manufacturing applications. But for the analyst, it is perfect. It avoids the need to learn any other CAD system, and (in the case of SpaceClaim) has many features specifically designed for CAE model preparation.

Being easy to learn and use, analysts will often use it to create their own geometry. After all, creating an analysis model is not always a matter of subtracting or simplifying manufacturing geometry, but also adding what is not there … enclosures, terrestrial planes and other environments, planes of symmetry, expendables (e.g., fuel or coolant), etc.  Since the point of analysis is not just to verify a design but to adjust and optimize it, the ability of a thermal engineer to quickly modify a design, evaluating that variation, and then report any modifications to the design engineer is also valuable.

But when it comes to simplifying manufacturing geometry, from virtually any source including STEP and IGES, direct modeling shines. Why? Because the same “understanding” of the geometry and independence from the original recipe means that it can essentially import any CAD model or geometric file, and figure out how the basics of how it was formed, or how it should be automatically modified if adjusted. It automatically recognizes features based on the topology, without needing to be told that a rounded edge was formed by subtraction from a sharp edge, for example.

Once recognized … essentially reverse-engineered into the original CAD part … features such as holes and fillets can either be retained or removed according to the thermal analyst’s needs. A new and re-purposed model can be quickly created. It is important to keep in mind that once a complex and derivative part has been returned to a simplified state, it is now amenable to parametric manipulation. Simplification doesn’t just increase speed and accuracy, it restores accessibility.

If the intent of direct modeling was to reduce the time it takes to learn and use CAD software, then the “side effects” of nearly global import, healing, and defeaturing are gifts to every CAE analyst. For the thermal engineer, who often deals with system-level models that include air flow, radiation, etc., these gifts are doubly important because the need to simplify and reduce nodal density isn’t just a convenience, it is often enabling.

A Unique Focus on CAE

The power of direct modeling has not gone unnoticed by the major CAD software vendors, in part because it allows their users to import competitor’s files, and in part because it makes their products more attractive to casual or intermittent users where the retention of skills is a major issue. The “side effects” that make direct modeling appealing to the CAE analyst have also not gone unnoticed.

However, only one direct modeling tool has dedicated itself to CAE model preparation as a primary market: SpaceClaim Engineer. This is why C&R Technologies selected it as the basis for CRTech SpaceClaim, which offers extensions specific to thermal/fluid engineering.

Just the Beginning

C&R Technologies is actively developing both additional extensions to CRTech SpaceClaim, as well as corresponding extensions to Thermal Desktop to better exploit upstream preparation of thermal geometry within SpaceClaim. While SpaceClaim offers revolutionary improvements to the thermal engineer by removing CAD bottlenecks, the revolution isn’t over: it is just beginning.

C&R Technologies is also working to combine the thermal model tagging and advanced meshing features of SpaceClaim with CRTech Thermal Workshop, to achieve the ultimate in flexibility and power. Watch for announcements in the coming year!

For a quick example, click here
For a detailed example, click here

 

Features

Import

• ACIS, STEP, IGES, ECAD, Rhinoceros, SketchUp, CGR, DWG, DXF, STL, OBJ, XAML, VRML, and 3D PDF (requires Adobe Acrobat 9 Pro Extended)
• Optional (with additional Data Exchange Package I): Pro/E, Inventor, CATIA v4, VDA
• Optional (with additional Data Exchange Package II): SolidWorks, Parasolid, NX
• Optional (with CATIA v5 Data Exchange Package): CATIA v5

Adding/Modifying Geometry

• Sketch, push-pull, parametric driving dimensions
• Automatically identify changes using 3D Mark-up

Feature Recognition and Removal

• Fill, remove, combine, pull, extend
• Recognize holes, fillets, rounds
• Select similarly-sized features using power selection

Repair

• Identify and eliminate gaps and small faces
• Identify and add missing faces
• Identify and fix interference
• Locate and correct split and inexact edges
• Merge adjacent surfaces
• Stitch surfaces into solid bodies

CAE Preparation

• Midsurfacing (2D from 3D) and Extending
• Beam Extraction (e.g., centerlines for FloCAD®)
• Volume Extraction and Enclosures (preparation for fluid flow modeling)
• Imprinting and Splitting (to influence the mesh for mating faces, heaters, surface property variations, etc.)
• Simplify into planes, cones, cylinders (perhaps for Thermal Desktop® snap-on scaffolding)

System Requirements