Creo Simulate > Reference Links > Minimum and Maximum Angles
  
Minimum and Maximum Angles
The angle between any two adjacent element edges or faces must be equal to or greater than 0 and less than 179, unless they are geometry-constrained angles. When AutoGEM is creating elements, edge and face angles should be between 5 and 175.
Angles less than 5 or greater than 175 can affect run time and results. For some models, angles less than 5 and greater than 175 may be useful for the following purposes:
creating elements in a difficult area
decreasing the total number of elements
helping AutoGEM to finish creating elements
When you first switch from creating to editing mode, Creo Simulate checks that the creation edge and face angles are between 5 and 175 and warns you if the angles are not in this range. Select Accept to keep the values you selected for the angles. Select Cancel to change the creation limits back to the previous limits.
Return to Allowable Edge and Face Angles.