Inconsistant existing spacing ratio in lines during symmetry operation

[DanJordy]

I created a 1/4 symmetric model of a PCB package that I want to expand to a full model (to place onto a board). When I expand the geometry using VSYMM, I get the following error message "Line XXXX has inconsistent spacing ratio with line YYYY". One line is the symmetric reflection of the other line. The volume generation then quits.

Does anyone know why this occurs and what can be done to work around it? I've tried different combinations of modeling, mirroring the area/volumes and meshing and still run into this problem. I've done it before without incident in another model, but am not sure why its happening now.

 

[meshparts]

The symmetry expansion is done about the active coordinate system. If you expand along the x axis (about the yz plane) of your active coordinate system, then the geometry must lie completly on the right or left hand side of the yz plane.

In your case I supose that you input the wrong symetry direction, or the active coordinate system ist is not properly set.

Regards,
Alex

 

[DanJordy]

The active coordinate system is properly set. I changed the order of the expansion (X then Y, or Y then X) and I have problems during the second expansion each time.

I modeled it this way:
1)Create the a single solder ball, including the package directly above it and the board directly below it.
2)Generate a pattern of solder balls in the upper R quadrant.
3)Create the area of the package in between the volumes created in 2)
4)Mesh the area(s) made in 3)
5)Extrude this area down to create the remaining package and board volume that lies in between the volumes from 2)
6)Mirror all the volumes about the YZ & XZ plane to create a full model
7) Generate the missing PCB and screw supports

I did find a workaround,by
a)meshing the area from 3) first,
b)mirroring only this area (not the unit cells from 2)
c)extruding the area created in b) down to create the remaining package & PCB
d)mirror the unit cells generated in 2)

I've had this work on previous models, so I'm not sure why I had to do this workaround, and what exactly the error message means.

 

[ansysfreak]

Hi

What do you want a 1/4 model and then graphic expand to full model?
Or 1/4 model to a real full model. Because if you mirror it and your model lies on one of the axes your model keypoints,lines,area's,elements etc. will lay on top of eatch outher.

Grtz
Garry

 

[DanJordy]

I have a chip that has 1/4 symmetry, but the chip does not lie in the center of the board. I need to move it to its actual position. In the future I'm going to need the quarter symmetry model, so I thought it would be easier to model it and then expand it to the real full model.

I use NUMMRG, ALL to get rid of keypoints, lines, areas, elements etc. lying on top of each other.