error: Failed to build the external loop when CAD file imported into NUMECA

SNeCu · March 15, 2016, 04:22

When I import igs file including 4 faces of one blade into the autogrid5, it works. However, mesh generation cannot work as an error: Failed to build the external loop for one trimmed surface! The geometry is maybe defined with too low precision or the loop is not closed.
I do know how to do next?

colinda1 · March 21, 2016, 03:13

Probably the cause of the problem is exactly as described: the edges of a surface in the IGES file, are not connected in the corner to sufficient tolerance. If you zoom in on the corners you may see that in one or more corners there is a gap between the two edges in the corner.

The possible options are in order of preference:
- to go back to the CAD software and define the geometry with a higher accuracy.
- to use a CAD repair tool to repair the geometry
- to go into IGG™ and project a face on the surface using sufficiently fine resolution on the face and taking special care in the problematic corner. This face can then be exported as a surface and used in AutoGrid5.

SNeCu · March 23, 2016, 22:51

Yes, you got the problem and now I am struggle with how to give a geometry with higher accuracy. I use Solidworks to save the file in different formats but all of them are failed to work in autogrid5...
Which CAD repair tool is appropriate to deal with it?

colinda1 · March 24, 2016, 01:00

Parasolid export does not work? In that case just selecting another file format may not be sufficient and the geometry needs to be carefully reworked. What are the units used in Solidworks and what are the export units?

Cadfix and Datakit are examples of CAD repair softwares but not for free. Maybe somebody else knows a good free one.

alederiaz · October 5, 2016, 10:40

Dears,
I have the same problem right now. I tried to change the feature used for shaping the blade in CATIA but I do not get the accuracy required.
How can I find the edges where the problems are? Any other ideas..? (.igs attached)

..and Colinda, I did not get the third option you mentioned. You mean using IGG to create a new surface on the low resolution area?
Thank you

March 15, 2016, 04:22	error: Failed to build the external loop when CAD file imported into NUMECA	#1
SNeCu Member Nate Lau Join Date: Mar 2016 Posts: 33 Rep Power: 10	When I import igs file including 4 faces of one blade into the autogrid5, it works. However, mesh generation cannot work as an error: *Failed to build the external loop for one trimmed surface! The geometry is maybe defined with too low precision or the loop is not closed.* I do know how to do next? Last edited by SNeCu; March 15, 2016 at 04:23. Reason: No enough label

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March 21, 2016, 03:13		#2
colinda1 Senior Member Colinda Join Date: May 2012 Location: Brussels Posts: 151 Rep Power: 13	Probably the cause of the problem is exactly as described: the edges of a surface in the IGES file, are not connected in the corner to sufficient tolerance. If you zoom in on the corners you may see that in one or more corners there is a gap between the two edges in the corner. The possible options are in order of preference: - to go back to the CAD software and define the geometry with a higher accuracy. - to use a CAD repair tool to repair the geometry - to go into IGG™ and project a face on the surface using sufficiently fine resolution on the face and taking special care in the problematic corner. This face can then be exported as a surface and used in AutoGrid5.

March 23, 2016, 22:51		#3
SNeCu Member Nate Lau Join Date: Mar 2016 Posts: 33 Rep Power: 10	Yes, you got the problem and now I am struggle with how to give a geometry with higher accuracy. I use Solidworks to save the file in different formats but all of them are failed to work in autogrid5... Which CAD repair tool is appropriate to deal with it?

March 24, 2016, 01:00		#4
colinda1 Senior Member Colinda Join Date: May 2012 Location: Brussels Posts: 151 Rep Power: 13	Parasolid export does not work? In that case just selecting another file format may not be sufficient and the geometry needs to be carefully reworked. What are the units used in Solidworks and what are the export units? Cadfix and Datakit are examples of CAD repair softwares but not for free. Maybe somebody else knows a good free one.