Help needed regarding the numbering of COH3D6 element in Abaqus

Dear all,

I am working on create a zero thickness COH3D6 element in Abaqus. Part of the issue is to correct numbering the COH3D6 element. I tried one algorithm below to check the node numbering:



And the code I created based on this algorithm is below:

A1_A2 = Coor(A2,2:4) - Coor(A1,2:4);
A1_A3 = Coor(A3,2:4) - Coor(A1,2:4);
Bin_normal = cross(A1_A2, A1_A3);

CACB = El_Cen_B - El_Cen_A;
Bin_dot = dot(Bin_normal, CACB);

if Bin_dot>0
NewCohEl=[A1 A2 A3 B1 B2 B3];
end
if Bin_dot<0
NewCohEl=[A1 A3 A2 B1 B3 B2];
end

However, when I used these created COH3D6 elements to run the simulation, the Abaqus gave me an error below, and this error message applied to 30% of the COH3D6 elements I created.

"The thickness calculated from geometry is negative for element 267 instance instance-1. Check if node
numbering is correct. This message will be printed a maximum of 5 times.

THE THICKNESS CALCULATED FROM GEOMETRY IS EQUAL TO ZERO FOR ELEMENT 267 INSTANCE INSTANCE-1. THIS IS
NOT ALLOWED IN Abaqus. A NON-ZERO THICKNESS VALUE SHOULD BE SPECIFIED IN THIS CASE. THIS MESSAGE WILL
BE PRINTED A MAXIMUM OF 5 TIMES."

If somebody know the reason or could give me some hints regarding on this, it is much appreciated!

Thanks a lot for your time,
Bin