Assignment 1
Objective: To perform geometry clean up and mesh operation on the given three models with the given quality criteria specification.
1) Practice
2) Clip repair
3) Mounting Bracket
*conditions
- ignore holes less than diameter 5 mm
- take mesh target length as 5 mm
- take minimum length as 3.5 mm
- take maximum length as 7 mm
- assign thickness to the 2D shell elements as the respective model already had.
- save in ‘.hm’ format
Observation: The given models are all solid sheet metal parts which have no different parts them and have uniform thickness throughout their length.
The three models are:
1) Practice
2) Clip repair
3) Mounting Bracket
Theory:
-Purpose of doing: When the CAD models are translated/imported into a pre-processor in order to prepare it ready for the post-processing software, the geometry of the model gets distorted and deformed most of the times.
-Some of the common errors are missing/deformed/extra surfaces, missing fillets/champers/beads, missing holes etc.
Thus a proper cleaning of geometry is required to shape the geometry as identical as possible to the original CAD model.
-There are two ways to do topology clean up in hyper mesh, the geometry can be cleaned either manually with the use of verity of commands in the geometry menu or either by the auto clean up command in the geometry menu.
-Manual method: in manual method commands such as quick edit, edge edit, Line/node/surface edits, line/node/surface (for creation), disfeature, and temp nodes, etc. are used. It is a time consuming processes but much effective and accurate against the distorted portions of the translated CAD model.
-Auto clean up: In this process, if required, the clean-up parameters can be optimized or else the default values are used by the system in order to clean topological errors in the model.
Procedure:
1) I checked for any topological errors and distorted geometry portions. There were no portions of the geometry where the geometry was either distorted or misaligned or improper in the second and third model. However in the first model there are portions where the surfaces are missing and needed to be pathed.
I did it manually with the options such as
- (Geometry > edge edit option).
-and Edit points option
There were other missing surfaces that can be found through toggling the view options for showing free edge of any surface.
Checked again for the errors if any.
Found some extra extended surface at the edge. Then used project line on surface option and then trimmed the surface with that line to delete it finally.
2) Extract mid surface out of all small thickness components. For extracting
The mid surface, I used the (Geometry > mid surface > extraction option
> offset) option.
3) Clean-up the mid surface and preparing it for mid surface. Looked for
Any missing or misaligned surface as I used the automatic method, but found nothing. Then used some clean up commands such
As:-
Geometry > quick edit / edge edit / surface / surface edit
Deleted extra lines used for creating geometry, which were no longer in use
And will only consuming space in the model's file.
Found holes on surfaces that were less than 5 mm diameter and created surface inside them.
Also made some washer splits on the edges around the holes bigger than 5 mm diameter.
(Geometry > quick edit > washer split)
4) Observed the symmetry of model part's and then for time saving, I cropped the geometries into their respective symmetrical half and quarter in some the third case.
Delete the remaining half and other useless lines from delete option.
5) Change the quality criteria parameters with the given values by going to the
Following menu:
2D > Auto mesh > QI optimize > edit criteria
Select surfaces and press mesh.
6) Then I did some mesh flow correction with the options shown below.
7) Tried to solve maximum of the quality criteria errors, such as min length,
Maximum length, skew, etc.
Tried to avoid maximum of the flow errors such as;
Opposite Tria’s, rotating quads and edge Tria’s.
8) The completed mesh then copied along the symmetrical axis with the option,
Tools > reflect > duplicate > select points > press MMB
9) Create a property id for each of the models with the thickness of the respective model thickness. For example for the first model-
10) At the end save the completed file from going to the file menu and save option, the default save format would be “ .hm “ . Save the file in “.hm” format.
Result: The given models are meshed with the given quality criteria and thickness were assigned to their elements. The final completed models are as shown below:
Conclusion and learning outcome:
In this challenge I learned the following points:
*understanding the geometry for symmetry and managing the working technique
According to it.
*suppress and unsuppressed the lines for preparing geometry for meshing.
*joining/equivalenting elements which were meshed separately before.
*improving mesh flow.
*figure out the ideal surface connectivity of any missing part.
*use auto filler surface option in surface menu to fill surface as shown below.