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How to create Free Edges

Pioneer
Pioneer

Hi folks,

The subject title may be a little bit misleading. As mentioned in my earlier thread, I am working on a fuselage project. I extracted the midsurfaces of the Frame and most of it was created. There is still significant geometrical clean up to be done. In one section of the frame, I had to manually extract the midsurface for the web and had to create the flange as well. I applied Midsurface->Intersect->All command and then proceeded to check for free edges. The section where I manually created surfaces are not included in the part of free edge. I want to know how to make them part of the overall surface geometry so that FEMAP recognizes them as free edge? I am including a screenshot of the affected area with illustrations. Please feel free to ask for more info if needed.

 

Fus1.png

14 REPLIES

Re: How to create Free Edges

Solution Partner Phenom Solution Partner Phenom
Solution Partner Phenom

Hello!,

Isolate your model and post it here, then we will be able to take a look to it. Include the original solid in one layer, and the generated midsurfaces in another, this way we can investigate if the problem is caused by a bad use of FEMAP.

Best regards,

Blas.

Blas Molero Hidalgo, Ingeniero Industrial, Director
IBERISA • 48004 BILBAO (SPAIN)
WEB: http://www.iberisa.com
Blog Femap-NX Nastran: http://iberisa.wordpress.com/

Re: How to create Free Edges

Phenom
Phenom

You should give Geometry -> Surface -> Non-manifold Add  a try.  With this you set a tolerance which provides a little more lenience in the precision needed between intersecting surfaces where you need them properly connected together, as is required in this case.   If you are working in mm, a tolerance somewhere around 1e-4 to 1e-3 is often good, while ~ 1e-6 is a better tolerance for inch or metre modelled geometery.

 

A couple of minor cautions (which should not stop you using this command):

1. Non-manifold Add can make minor adjustments to the geometry, so be careful about using too loose a tolerance.  Points/Edges can move larger distances than the tolerance value.

2.  There are some commands which cannot be used after Non-Manifold Add if the solid is more complex than a basic sheet solid (eg. if it has tee intesections).  These include modifying the surface normal, and using Geometry -> Midsurface -> Extend (also available in the Meshing Toolbox).  However, the new V11.2 Project/Move Point options in the Meshing Toolbox add some very nice extra's for fixing untidy geometry - even for Non-Manifold Added geometry.

 

Re: How to create Free Edges

Pioneer
Pioneer

Hi folks,

I need to find out if I can post the model here (even if it is a part of the whole). May take a couple of days.

 

In the mean time, I am cleaning up the model further. I thought about nonmanifold option and that may eventually create "free edges". Let me make back ups as I go along and once I get the geometry as I want, I will use the above command, especially after the cautions that were posted by EndZ about limitations post using the command.

 

Thanks for the replies. I appreciate the quick support here. 

Re: How to create Free Edges

Pioneer
Pioneer

Hi,

I am kinda hijacking this thread with a different question. How do I change the base plane in FEMAP while drawing a curve using Geo -> Curve-Arc command? I want the curve to be drawn in Z-Y plane but the curve always gets drawn in the default XY plane. Is there an option where I can specify which plane to use as base while drawing the curve?

Re: How to create Free Edges

Legend
Legend

Hi VN1981,

 

there are more way to modify Workplan:

 

1. Tools -> Workplan... command

2. Right Mouse Button -> Workplane... command

3. F2 shortcut key

 

There are also Arc and Circle commands too that work without a Workplan (in 3D):

 

Geometry -> Curve - Arc -> Points...

Geometry -> Curve - Arc -> Center and Points...

Geometry -> Curve - Arc -> Start-End-Direction...

Geometry -> Curve - Circle -> Points on Arc...

Geometry -> Curve - Circle -> Center and Points...

 

Best regards,

 

Peter Kaderasz

Re: How to create Free Edges

Phenom
Phenom

As an FYI, you will see that when you access Geometry -> Curve commands (eg. Line, Arc, Circle) through the menus, the menu is divided into "above the lline" and "below the line" commands. The commands "above the line" will create the geometry on the workplane, so the workplane must be positioned / oriented where needed for these commands to create the geometry in the intended location.  The commands "below the line" are general 3D commands and the position of the workplane has no influence on where the geometry is created.

Hope that helps.

Re: How to create Free Edges

Pioneer
Pioneer

Hi folks,

I am still continuing with geometry clean up of my fuselage project. Geometry is quite complicated and STL import really rearranges many of the verticies & surfaces and thus is very a tedious process.

 

I am seeing a strange color (red) surfaces, points & curves. What does it mean and how can I rectify it? I have already applied Geo -> Surface -> Non-manifold Add command.

 

I have attached pictures of the affected region.

 

Fus1.png

 

Another image in Wireframe mode

 

Fus2.png

 

Also, when I display the model in wireframe, some of the surfaces are cross hatched while the rest are not. What is the significance of a hatched surface?

 

Fus3.png

 

Thanks in advance

Re: How to create Free Edges

Solution Partner Phenom Solution Partner Phenom
Solution Partner Phenom

Hello!,

When you import any geometry using STEP, Parasolid, etc.. make sure to deactivate the option INCREMENT COLOR, if you do not do it then FEMAP will increment colors randomly for points & curves of your assembly parts, as you has noted.

Actually this option in ON by default, but I strongly suggest to FEMAP developers to set OFF by default in all importing geometry commands (ACIS, STEP, Parasolid, etc), the result is not good and later the user should have to issue commands like "MODIFY > COLOR > POINTS", and "MODIFY > COLOR > CURVES" to set the desired color, etc.., then loosing time.

 

step-import-increment-color-off.png


By the way, what is worse: when importing ANY NATIVE GEOMETRY like SolidEdge Assemblies (*.asm), NX assemblies (*.prt), etc.. the option INCREMENT COLOR is ON internally set by default, not available to choose OFF in the command GUI, then time loosing again.

Please FEMAP developers, set OFF by default in ANY import geometry command, thanks!!.

Best regards,
Blas.

Blas Molero Hidalgo, Ingeniero Industrial, Director
IBERISA • 48004 BILBAO (SPAIN)
WEB: http://www.iberisa.com
Blog Femap-NX Nastran: http://iberisa.wordpress.com/

Re: How to create Free Edges

Pioneer
Pioneer

Hello Sir,

Thanks for replying,

 

I think you may be right. It was possibly due to mismatch between different layers or something.

 

BTW, do you know the difference between hatched & unhatched surface as shown in the 3rd picture. What does hatched surface mean & how to make it unhatched?