BTOL-Command

[madnut]

Hi!

For creating a geometry in ANSYS CLASSIC, with which I don´t have a lot of experience, it is inevitable that I add two volumes using the boolean operation. However I´m receiving the following error message:
"Boolean operation failed: Adjust the tolerance value on the BTOL command to some fraction of the minimum keypoint distance. Model size (current problem) 2.081640e+01, current BTOL setting 1.0e-05, minimum keypoint distance 4.354838e-03."
I then tried different point coincidence tolerances by using the BTOL command and using different factors (10x, 50x, 100x, etc) on the value given in the error message above. As a result the error message is changing ("Try loosening the tolerance...", "The following entities do not support boolean operation..."), or the calculation time is skyrocketing.

Various approaches such as splitting the volumes and adding the parts step by step to avoid the error failed, since I have limited possibilities of changing the geometry itself.

Is there anybody with experience on the BTOL command? Are there any general guidelines for executing this command?


Thanks in advance

Madnut

 

[qwicker]

Usually this error means there are problems with your geometries. If you want to add volumes, they must be very very close (basically touching) in order for the add command to work.

Are your volumes generated from a CAD interface then brought into Ansys?

 

[madnut]

The volumes are generated directly in Ansys 11.

They share boundery lines and therfore also boundary surfaces, but can't be attached. Another attempt with overlapping volumes wasn't successful either.

Regards,

Madnut

 

[qwicker]

Hmmm... if you plot lines only, are the lines shared? Check out the keypoint XYZ locations as well. It will let you know if the parts are truly touching.

Also, if the parts were created perfectly in Ansys and already share lines, keypoints, areas etc, you could always glue them together and assign them the same material properties. That would have the same effect as adding.

 

[Stringmaker]

Ansys is a nasty critter for stuff like this. One thing you can do is look at the minimum keypoint distance it prompts you with and set BTOL slightly larger. In your case I'd recommend trying BTOL,.005 for starters. Don't set BTOL too large or bad things will happen. For instance, try BTOL,10 and see what happens. Just don't save the database afterwards.

Ansys is very picky about geometry. Go back through and interrogate what you did previously. Also, the help is very good as well!