User Manual
| User Manual | |
| We investigated a few options
for accessing the CAD geometry into ELECTROFLO� software. Many Finite
Element codes have incorporated direct CAD access into their packages.
Some have integrated the geometry kernel such as Parasolid into their
software. This gives them an ability to directly access the geometry in
the native format without any translation. However, each of the major
CAD packages use a different kernel for their geometry creation , many
software vendors rely on importing the files translated from the CAD
systems into a widely accepted formats such as IGES or STEP. These
translations work well for finite element structural codes, however may
not be the best suited approach to finite difference Cartesian solvers
for CFD such as ELECTROFLO�. ELECTROFLO� requires Cartesian mesh; which gives it greater flexibility in solution algorithms and also enhances its speed and efficiency and convergence. The CAD geometry is created by design engineers and they rightly put all the details appropriate for manufacture of the part or assembly. When an analyst has to analyze this part or assembly for functional aspects such as stress, temperature or survivability many of these details such as screw holes, etc, essential for the design are extraneous for analysis. It takes a lot of analyst valuable time cleaning up even a perfectly imported CAD geometry of unwanted detail. We have investigated methods to create a Cartesian mesh for the important components of an electronic assembly. One such approach is that the analyst creates a tri mesh in the CAD software around the components to be exported for cooling analysis. The Cartesian mesher will work on this triangular mesh and create a Cartesian mesh that can be readily used in ELECTROFLO�. To illustrate the point Figure 8 depicts a typical PC board assembly and Figure 9 shows a typical bus bar used in electronics designs. As can be seen in Figure 8, there many components and component details that contribute only clutter to the thermal analysis. We need the chips and other components producing significant heat and are not interested in all the electronic leads and other details. As analyst will mesh the components he wants to be included in thermal analysis in ELECTROFLO� with a triangular mesh shown in Fig. 8). A Cartesian mesher will take this triangular mesh and crate a Cartesian mesh that can be imported into ELFO and used in conjunction with the CFD mesh created inside ELFO. The mesh shown here is from Cartesian mesher in Harpoon who TES may use as partners for this technology. We are also in the process of writing the Cartesian meshing software ourselves. |
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| Figure 8: Typical PC Board Assembly | |
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| Figure 9: Typical Bus Bar in Aircraft Electronics Boxes | |
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| Figure 10 Triangular Mesh on the Bus Bar |
Figures below show two examples. In both cases the geometry was imported into ElectroFlo and transformed into ElectroFlo objects. The first example is a bus bar, typically used in aircraft electronics, and the second example shows an imported printed wiring board into the ElectroFlo� environment.
Figure 11: Bus bar imported from CAD into ElectroFlo�
Figure 12: Imported PWB into ElectroFlo�
Intermediate Data Format (IDF) Reader
We have added the IDF (version 2.0 and 3.0) file reader for ElectroFLO�. IDF stands for Intermediate Data Format, and was designed as a neutral format for exchanging PCA (Printed Circuit Assembly) information between PCB layout design (ECAD) systems like Altium and Allegro and Mechanical CAD systems such as SolidWorks.
The IDF file format was originally developed in 1992 and has evolved ever since. The current version of the file format is IDF 4.0, but most systems (including the CircuitWorks products) still read and write the earlier IDF 2.0 and IDF 3.0 formats.
File names and suffixes and contents
Each IDF 2.0 or 3.0 'file' is actually two files on disk. The two files normally have the file suffixes .emn and .emp, but other file suffixes are used as well such as .brd and .lib. Both sections of the file need to be present in the same location with the same name. For example an IDF 'file' called 'pcb_board' would consist of a file called pcb_board.emn and a file called �pcb_board.emp�. The first .emn file contains information about the physical size and shape of the PCB, its various holes and cut-outs, and the locations of the components on it. The .emp file contains information about the size and shape of each of the components on the PCB.
IDF 2.0 files contain basic information about the shape of the board, the position and size of plated and non-plated circular holes on the board, and the position and basic shape of the components on the board. IDF 3.0 expanded the concept further with support for more keep out and outline types but the two formats are very similar in structure and content.
The introduction of the IDF 4.0 file format brought the ability to interchange much more detailed information. IDF 4.0 files contain information about board features such as traces, pads, vias and filled areas which aren't supported by IDF 2.0 and 3.0. The IDF 4.0 format also allows shapes to be defined in much more detail than the previous versions of the format. IDF 4.0 file format is a lot more complex than IDF 2.0 and 3.0 and its adoption in the ECAD and MCAD communities has been fairly slow and very few ECAD vendors write out an IDF 4.0 file.
Here are a few screen shots of IDF files read into ElectroFLO�. This will improve the productivity of the users as they do not have to create the board and the components manually.
Figure 13: Imported PWB into ElectroFlo�
Figure 14: Imported PWB into ElectroFlo�