Hi @AliBuildsAI ,
As you mentioned the conventional hand-eye calibration functions in OpenCV won’t give you good results for 4DOF setups since they require high rotation values along all three axis to work properly. However I have found some papers that try to solve this for 4DOF setups :
https://www.researchgate.net/publication/269104808_Hand-Eye_Calibration_of_SCARA_Robots
Also, an implementation od this is available on git : GitHub - QuantuMope/handeye-4dof: Handeye calibration for 4DOF manipulators using dual quaternions.
You may find these useful.