Problem With Cognex Calibration

Hello everyone, first of all I want to apologise if I make grammar mistakes because English is not my first language.

I am making a Project with a Cognex Camera and did the Calibration with the UR Caps, my problem is when the camera takes a photo as soon the part is not in the middle of the image the robot fails pickin the part. The bigger the distance of the part to the middle the bigger is the failed distance picking the part.

Could someone give me a hand?