Week 3 - Electronic Enclosure

AIM:

To import the power board assembly in ANSYS Spaceclaim and modify the geometry of the model to make it compatible for import in Icepak.

INTRODUCTION:

A 2-D/3-D model used for thermal simulations in ANSYS Icepak is generally made in independent CAD packages like Solidworks, CATIA V5, etc., and is imported as neutral file formats like .igs, .step file. Now, before importing this model in Icepak it is necessary to make all the components of the assembly compatible with Icepak so that it can be imported to the Icepak environment.

After importing the model in ANSYS Spaceclaim following basic facts should be gathered before geometry cleanup:

• Model size (number of bodies)
• The functionality of individual bodies or group of bodies
• Goals of the Thermal and Flow analysis

Now, to decide which bodies should be kept and which ones should be removed we should divide all the bodies into four categories:

1. Focus Bodies: They are of greatest interest.
2. Necessary Bodies: These bodies affect focus bodies.
3. Peripheral Bodies: The influence of these bodies on focus bodies is uncertain.
4. Dispensable Bodies: These bodies do not affect the focus bodies.

It is clear for the definitions, the dispensable bodies can be deleted to simplify the geometry of the model.

In some cases there exist small details in the geometry that, if meshed, would result in very small elements and a potentially huge element budget. Small curves and surfaces can sometimes result from details in the design solid model that may not be necessary for analysis or may even be a result of the careless construction of the CAD model. In either case, it is important to remove or modify these features before meshing.

Thus, geometry cleanup is an important step before setting up a simulation.

PROCESS FOLLOWED FOR POWER BOARD ASSEMBLY:

Step 1: Removing Dispensable Bodies (Enclosure extra part, Screws, Washers)

In this step, the bodies which do not affect the results of the simulation significantly are removed from the model. This is done to reduce the number of components in the assembly which ultimately reduces the meshing and solving time. The parts that are removed in this step are enclosure extra parts, screws, and washers. These parts are shown in the images below.

Step 2: Filling the gaps that won't exist during the actual application of the model (Removing rounds in the geometry)

While setting up the simulation, it is necessary that the geometry of our model should match exactly with the actual application to get accurate results. One of the important things to consider during thermal simulations is the presence of gaps. In the case of electrical boards, geometry can have gaps that do not exist in its real-world application. So, these gaps must be filled and this is what is done in this step. Also, to simplify the geometry, rounds and chamfers are removed from the model.

Step 3: Converting the components into Icepak bodies and simplifying other objects.

As mentioned before, it is necessary to transform the geometry into Icepak compatible bodies for importing it to Icepak. The CAD objects can be simplified at three levels:

• Level 0 (Bounding Box): This level covers the body with a single bounding box. It is useful for simplifying simple geometries such as cubes and cuboids.
• Level 1 (A cube, cylinder): At this level, we can covert bodies that are cylindrical, cuboidal. This level is better than level 0 as it more closely follows the geometry of the object.

• Level 2 (A polygon fit): This level can closely replicate highly complex geometries involving curves and proves sometimes to be better than the level 3 as it simplifies the geometry but keeping the important information still intact.

• Level 3 (CAD object): This level is used for extremely complex geometries that cannot be simplified even with level 2 simplification without distorting the actual object. In this method, Spaceclaim converts the model into facets that define the geometry of the object, and we can control the quality of facets in this method.

The final model after conversion into Icepak bodies is shown in the image below.

Step 4: Importing the geometry in Icepak

The final model imported in the Icepak is shown in the image below.

In this model, we can see the openings are created using three different methods:

• Simplifying the body that contains the openings using Level 2 simplification
• By creating openings
• By creating a grille in the SpaceClaim

This was done to explore various options present in Spaceclaim to create an opening in the model.

CONCLUSION:

In this exercise, a power board assembly was taken and the goal was to transform the model to make it Icepak compatible. After performing basic cleanup operations such as deleting dispensable bodies, filling gaps, etc., the model was simplified into Icepak bodies using four levels of geometry simplification. At last, the transformed model was imported into Icepak and there were no errors found in the geometry after import.