It is very difficult to answer this question. What is the best way to design CAD models? Some engineers like the flexibility of direct modeling. Whereas some engineers prefer the way parametric modeling works. Parametric modeling is leading the race. But direct modeling is also not far away. This article covers various types of cad modeling approaches : Parametric, Direct and synchronous modeling.
Parametric Modeling (History Based CAD)
A parametric model contains information like feature dimensions, constraints, relationships and mates between various sketch, features and assembly. Parametric modeling helps in capturing design intent using features and constraints. This aids users while working on similar type of product line such as gear or fasteners industry.
Parametric modeling is very effective for companies who work on similar family of products, where one part is very slightly different from another part.
For any change in design, cad model feature parameters are modified. This has an impact on all features created after that feature. Therefore complete model is updated instantly. But if the model is complex and design intent is not correct. Any change in feature can break the cad model.
Features of Parametric CAD Modeling:
- Dimension Driven.
- Structured CAD Modeling.
- Feature History.
- Parent Child Relationship.
- Sketch Constraints.
- Part, Assembly and drawing Modes.
- Assembly Mates.
Benefits of Parametric CAD Modeling:
- Parametric cad tools also have some of direct editing tool capability.
- Industry specific parametric cad tools extensions are also available.
- Designed parts can be reused.
- Cad model history tree shows product design intent.
Challenges with Parametric CAD Modeling:
- Good modeling practices need to be followed.
- How to design cad model need to be planned.
- Long learning curve.
- Difficult to modify dumb files (step/iges).
- Large file size can slow the system.
- To modify cad data, user need to first understand the complete feature history.
Direct CAD Modeling (History Free)
In direct cad modeling features are created one on another. In this process modeling features are not captured. Therefore feature history is not available. For any design modification new feature is added.
Direct modeling aid designers to create CAD geometry quickly. It is used for dumb parts (step/iges) or parts where design history is not available. It helps designers to focus on innovation and creativity. Therefore direct modeling is more popular during initial design phase when creativity and innovation matters.
Features of Direct CAD Modeling:
- Flexible CAD Modeling Process.
- Feature history is not available.
- Direct Edit.
- Parent Child relationship is not available.
- Parts and assemblies are created in one single mode.
- Constraints and mates are not used.
Benefits of Direct CAD Modeling:
- Any type of geometry can be created or edited.
- Works best with native and dumb data (step/iges).
- No need to plan for cad modeling. Therefore designers concentrate on innovation and creativity.
- Short learning curve.
- Geometry Editing is independent of how it is created.
- Relatively smaller file size.
Challenges of Direct CAD Modeling:
- Cad design automation is not possible.
- Users can not understand design intent using cad model.
- Legacy data can not be used.
Hybrid Approach : Synchronous Modeling
Synchronous technology is very helpful for tool and industrial designers. Industrial designers utilize this technology to create designs in a natural way. CAD Models created using synchronous technology can be used by CAD experts to create feature based CAD model for manufacturing. This makes complete design process more robust.
Features of Synchronous Modeling
- Dimension Driven.
- Feature Based.
- Synchronous Technology.
- History is available.
- Flexible Editing.
- Flexible Edit in Part and Assembly mode.
- Easy to use.
Various CAD Modeling Tools
To sum up, Parametric and direct cad modeling approaches are used to design cad models. Both approaches have their own advantages and limitations. To overcome the limitations of both approaches. Hybrid approach (Synchronous Technology) is making its way.
For complex product designs, both parametric and direct cad modeling is required. For example product A class surfaces are designed using direct cad modeling and detailed design is done in parametric cad software.
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