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-   -   error when using boolean subtract (http://www.cfd-online.com/Forums/star-ccm/95326-error-when-using-boolean-subtract.html)

fshak92 December 13, 2011 16:04

error when using boolean subtract
 
hi
i have a surface meshed model of a cutting tool.
i want to create a block as a air boundary around my machine,,but the problem is that when i import the machine and create the block around that,,when i want to use boolean subtract(for subtracting the machine from my block) i get the error:: "the region is not closed and manifold",
do you have any idea about my problem?
thank you in advance

rwryne December 13, 2011 16:11

Quote:

Originally Posted by omid88 (Post 335726)
hi
i have a surface meshed model of a cutting tool.
i want to create a block as a air boundary around my machine,,but the problem is that when i import the machine and create the block around that,,when i want to use boolean subtract(for subtracting the machine from my block) i get the error:: "the region is not closed and manifold",
do you have any idea about my problem?
thank you in advance

I am assuming you are using around version 6.04 (6.02 - 6.06)

First import the geometry, preferrably as a part. If it imports as just 1 part, right click that entity and hit Repair Surface. Now you want to run the diagnostics, unchecking "Face Quality" and "Face Proxmity" (those are taken care of by the remesher).

Repair any errors you have prior to doing a boolean operation.

Alternatively if the geometry is very rough, you can use the surface wrapper to mesh the air volume. This is a backup method in my mind, only to be used if you dont have the time for repairs or the amount of repairs is too extensive.

fshak92 December 13, 2011 17:52

thank you for your reply,,
but before using any meshing method i should substract my machine from my block,,,after that i can assign the parts to the region and then meshing.....
i used surface repair but there were many errors and with using automatic fixing just many of error were fixed,,after that again i got the error:"the region is not closed and manifold"
is there any command or way to correct my machine automatically?
(yeah i use 6.04)

rwryne December 15, 2011 08:44

Quote:

Originally Posted by omid88 (Post 335741)
thank you for your reply,,
but before using any meshing method i should substract my machine from my block,,,after that i can assign the parts to the region and then meshing.....

Yes and no to this. If you are not using surface wrapper, you do need to subtract your part from the block. In order to do this subtraction, you will need to fix your surface to where it has basically no errors.

If you are using teh surface wrapper, you do not have to subtract from the block. The surface wrapper has methods of setting this up, but it will only mesh the air volume, not the solids. Look up "surface wrapper" in the help, specifically a tutorial of it, and I think you will understand what I mean. Again, I do not consider the surface wrapper as the "preferred" method, but if you need to get this done in short order and fixing the geometrty is proving too difficult, this is the way to go.

rwryne December 15, 2011 08:47

Quote:

Originally Posted by omid88 (Post 335741)
i used surface repair but there were many errors and with using automatic fixing just many of error were fixed,,after that again i got the error:"the region is not closed and manifold" is there any command or way to correct my machine automatically?
(yeah i use 6.04)

Personally I do not like the automatic fixing and would nto recmomend its use. It often makes huge changes in order to fix stu ff, and its hard to tell what it did after its done. I do all my repairs by hand.

That said, how many is "many errors"? 1000s? 100s? 10s? Even if it is hundreds, it does not mean it takes a huge amount of time to fix. Once you get used to the repair tool, you can fly through these repairs. Spending even 3 or 4 hours (if its really bad) now can save you lots of trouble later.

Alternatively, you can work on cleaning up the gemoetry in your original CAD package. I always use a mixture of this, fixing some things in CATIA and somethings in STAR-CCM+.


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