ANALYSIS OF ASSEMBLIES FROM CAD PROGRAMS BY GEOSTAR 2.5
(Extract the Macro files required for assembly analysis by GEOSTAR from ASSEMBLY.ZIP
and copy them into COSMOS/M directory. The ASSEMBLY.ZIP file is found in COSMOS/M
directory after installing COSMOS/M.)
A procedure for analyzing assemblies by GEOSTAR, that is fairly 13113w222n simple to perform if the number of
parts are few and the mating surfaces are cylindrical or flat, is described below. It involves three steps
as follows:
(This procedure is not needed for SolidWorks assemblies, as the .geo file of the assembly
can be exported to GEOSTAR and meshed without any special requirements.
In the CAD software, identify the mating faces between parts and use available editing tools to create
an imprint of the mating faces on each adjoining part and then write Cosmos files (.GEO) of each one naming them P1.GEO, P2.GEO, P3.GEO, P4.GEO .. The idea of making imprints is illustrated on the following page for a Bolt and Washer assembly.
Copy the macro file ASSEMBLY.GEO from the COSMOS/M directory into the current working
directory. Open GEOSTAR and create a new file by the name it P1 and then load the macro ASSEMBLY.GEO.
Map the coincident regions on all the mating faces using the RGMAP command for full mesh
compatibility
Above three steps are described in more detail below.
Step 1
In Solid Edge right-click on the part to be modified in the Assembly Pathfinder and do Edit.
Use 'Cutout' tools to make the imprints. As far as possible use the adjoining part profiles. After
making all the necessary imprints, save the assembly as a SAT file and open the SAT file assembly.
This model will have all the parts positioned in the assembly coordinates. Now open each part and use
Save Copy As to save each file as P1.GEO, P2.GEO, P3.GEO . Use Options to set units.
In Pro/Engineer and PT Modeler, use Modify>Modify Part from the Assembly menu. Make use of
the Use Edge and Offset Edge tools in the Geometric Tools menu to make the imprints. In the assembly
mode use Interface>Export>IGES>ALL PARTS with the usual options. This command writes .IGS
files for each part in the assembly coordinates. GEO files can be created at the command prompt by
executing the following command.
IGES_GEO /tm /el /i=king (to create king.GEO from king.IGS)
These GEO files can then be renamed to P1.GEO, P2.GEO, P3.GEO, .
In Microstation Modeler the Construct Trim Surface tool can be used to make the imprints. For parts
that are embedded, the Boolean tools palette also helps to create the assembly. FEM>File>Export will
directly generate the GEO file of the assembly. Microstation Modeler users can skip step2.
Step 2
Every time you want to load an assembly into GEOSTAR, copy ASSEMBLY.GEO from the COSMOS/M
folder into the working directory. Then open a new problem with the name P1 and load ASSEMBLY.GEO
using the File>Load command. When prompted for the TOTAL number of Parts in the assembly, enter it
and then let the macro do the remaining work for you. You may rename the file P1 into something else after
the assembly is done.
Step 3
At this stage only the edges are compatible at the mating faces. If you need full mesh compatibility,
coincident regions at all the mating faces have to be mapped (from one to the other).
Use Geometry>Regions>Map command to do this and use either of the region as 'Source' for each
pair of mating surfaces. Define a uniform element size for all the parts with 10% tolerance and mesh
them one by one.
Note that full mesh compatibility is achieved along coincident regions.
Example: Assembly of Bolt and Washer.
Imprint on Washer Imprint on Bolt
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