CAD Model Exchange

New items are planned and created by utilizing Computer-aided structure (CAD) instruments, for example, CATIA, PRO E, UNIGRAPICS… and so forth. Associations pick their plan devices according to their prerequisites. After Design consummation the models ought to be moved to assembling, investigation… Etc.

So the information must be arranged so that other CAD/CAM (Computer-helped producing) devices ought to perceive. The nonpartisan organization is important to move the CAD information over the framework.

This report assists with understanding the significance and sorts of model exchange designs in CAD.

List of Abbreviations

CAD                                        Computer aided design

CAM Computer Aided Manufacturing

IGES                                        Initial Graphics Exchange Specification

STL                                         Stereolithography Tessellated Language

STEP                                      Standard for Exchange of Product data

VRML                                      Virtual Reality Modeling Language

VDA                                         Verband Der Automobilindustrie

 

Benefits

• Manufacturability becomes easier because these formats are readable by the CAD/CAM softwares so the quality of the product increases with less productivity time.
• The neutral formats reduces the time and money to transfer the data
• The original data need not be shared publicly (Especially to vendors)

So the awareness of the CAD model exchange is important factor to get the final product

Methods for exchange of CAD model data

The following methods are used to exchange the data between different CAD tools

• Neutral Formats
• Translators

Neutral Formats

The cad models are stored internally with specified formats in CAD tools. This may be different from the other softwares. For organizations to share designs across the various CAD & Computer aided manufacturing tools (CAM), their data must be formatted. So by using the neutral formats the cad data‘s are converted into compatible formats, which can be used by other CAD softwares

 

TYPES OF NEUTRAL FORMAT

Below mentioned are the widely used formats

• BASED ON THE OFFICIAL STANDARDS

1. Initial Graphics Exchange Specification (IGES)
2. Stereolithography Tessellated Language (STL)
3. Standard for Exchange of Product data (STEP)
4. Virtual Reality Modeling Language (VRML)
5. Verband Der Automobilindustrie (VDA)

• BASED ON THE INDUSTRIAL STANDARDS

1. Data exchange format  (DXF)
2. AutoCAD Drawing  (DWG)

 

Initial Graphics Exchange Specification (IGES)

IGES is used as a universal tool, providing a neutral format for many companies to transfer the engineering data between CAD/CAM systems.

• IGES is mainly a surface-based system, and the Latest versions of IGES fully support solid models using Boundary Representation

The following are the capabilities of the IGES format

–            The product definition includes geometric, topological, and non-geometric data

–            The geometry part defines the geometric entities to be used. (Wireframes, Surfaces  …etc)

–            The topology part defines the entities to describe the relationships between the geometric entities. The geometric shape of a product is described using these two parts (i.e.) geometry and topology.

–            The non-geometric part can be divided into annotation, definition, and organization. The annotation category consists of dimensions, drafting notations, text, etc.

–            The definition category allows users to define specific properties of individual or collections of entities. The organization category defines grouping of geometric, annotation, or property elements.

Disadvantages

 

• Few major CAD/CAM system developers have extended IGES in different ways, leading to minor losses of data during exchange between cad softwares. However, even a minor loss makes the file useless for NC manufacturing.
• Patching up or fixing the errors in an IGES file imported from different cad software requires considerable effort, leading to loss of productivity

 

Stereolithography Tessellated Language (STL)

 

STL format is widely used in Rapid prototyping system. STL file is generated from a precise CAD model using tessellation process (The format generates the triangles to approximate the CAD model).

• STL file consists of an unordered list of triangular facets representing the outside surface of the object
• This triangular facets are described by a set of X, Y and Z co-ordinates for each of the three vertices and a unit normal vector with X, Y and Z to indicate which side of facet is inside the object.
• The curved surfaces have to be decomposed into a number of facets by the CAD system before exporting. Higher faceting gives a more accurate surface, but increases the memory and computation requirement
• It is the preferred format for visualization and analysis programs, since these do not require accurate surface data. It is however, not suitable for NC manufacture, particularly with coarse faceting.

Standard for Exchange of Product Data (STEP)

The Standard for Exchange of Product data is proposed and managed by International Standards Organization.

• The STEP handles Wire frame, surface, and boundary-represented solid geometry
• STEP does not only define the geometric shape of a product. It also includes topology, features, tolerance specifications, material properties, etc. necessary to completely define the product for purposes of design, analysis, manufacture, test, inspection and product support.

STEP is a collection of standards to represent and exchange product information.The development is performed under the control of the International Standards organization (ISO)

Virtual Reality Modeling Language (VRML)

 

VRML is a file format for describing interactive 3D objects .It is also an interchange format for integrated 3D graphics and multimedia. The aim of VRML is to make to incorporate 3D models into virtual environments

• Models can be created with geometry, texture and color.
• In addition, these models can be animated and sound effects can also be incorporated using this file format. VRML graphics are displayed using a VRML browser.
• VRML file formats are used in Rapid prototyping
• One of the advantages of VRML files is that they contain less redundant data when compared with STL files
• VRML files are very convenient in storing the color information of a model

Verband Der Automobilindustrie (VDA)

VDA is a German standard and developed by the German Automobile Manufacturers Association.

• It is primarily meant for transferring surface data. This format is not universally used.
• This is one of format promoted by the German industry consortiums.

Data exchange format (DXF)

DXF (Data exchange Format) was developed by Autodesk. It is widely used to exchange 2D/3D wire frame data

• A DXF file is a complete representation of the AutoCAD drawing database. Some features or concepts can’t be used by other CAD systems.
• The DXF version R13 supports wire frame, surface, and solid representations.
• A DXF file consists of four sections: Header, Table, Block, and Entity section.
• The header section contains general information about the drawing. Each parameter has a variable name and an associated value. The table section contains definitions of line types, layers, text styles, views, etc.
• The block section contains entities for block definitions. These entities define the blocks used in the drawing. The format of the entities in the block section is identical to entities in the entity section.
• The entity section contains the drawing entities, including any block references. Items in the entity section exist in the block section and the appearances of entities in the two sections are identical.

AutoCAD Drawing (DWG)

 

DWG (“drawing”) is a format used for storing two / three dimensional design data. DWG format is developed by Autodesk and it is widely used to exchange 2D/3D wire frame data.

DWG transfers model geometry in binary files, while DXF represents the data in ASCII format.

Translator

 

Based on the requirements companies migrate their Cad data’s from one Cad software to another. The cad model created in their original software must be converted to the format of new one. So the translators are used to convert cad data’s between the two software. There are many translators are available in the market.

 

For example, if the original CAD model was designed and developed in Pro-e then the translator helps to convert the cad data from pro e to CATIA.

Applications

• Translators are very useful for migrating the data’s from one CAD tool to another CAD Tool.
• Conversion through translator is more economical and faster than remodeling the cad data (re mastering)
• The manual re mastering process can be eliminated.

Conclusion

The neutral formats and translator are widely used to translate the cad data’s between the cad software. It helps to reduce the productivity time and gives the quality products to the market.

The following methods are used to exchange the data between different CAD tools

• Neutral Formats
• Translators

Neutral Formats

The cad models are stored internally with specified formats in CAD tools. This may be different from the other softwares. For organizations to share designs across the various CAD & Computer aided manufacturing tools (CAM), their data must be formatted. So by using the neutral formats the cad data‘s are converted into compatible formats, which can be used by other CAD softwares

Source: https://catiatutor.com/cad-model-exchange/