Why does FEMM fail with a triangle precision error?

When running a MANATEE electromagnetic simulation with FEMM you may encounter the following error :
I attempted to split a segment to a smaller size than can be accommodated by the finite precision of floating point arithmetic.
Try increasing the area criterion and/or reducing the minimum allowable angle so that tiny triangles are not created.

FEMM : Triangle precision error
FEMM : Triangle precision error

As you can see the error is raised by "Triangle" which is the meshing tool of FEMM. It means that FEMM wasn’t able to mesh your machine with the current parameters. You can also see that the message contains the coordinate of the problem. So by opening the machine file in FEMM you can have a better understanding of what is causing the issue (and find a way to modify your geometry to remove the problem).

This error can in particular appeared with narrow geometry. For instance, on the following machine :

Narrow geometry that creates issues in FEMM
Narrow geometry that creates issues in FEMM

One can see that the space between the magnet and the lamination is very thin and therefore it can create some meshing issues.

In this particular case, the problem is that the angle between the magnet and the lamination is too small to create "correct mesh triangle". A "correct mesh triangle" is defined (amount other criteria) by the minimum acceptable angle for triangle. In MANATEE, this parameter can be change with :

% finite element mesh min angle (default: +30°)
Input.Simu.min_angle_FEMM = 30;

So by reducing this minimum angle we are able to mesh our machine and run our simulation. Keep in mind that, by lowering this parameter, you have also lower the quality of your mesh.

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