Why is the machining time estimation in VisualMill sometimes not the same as the actual machining time on the machine tool?
Machining times are calculated in VisualMill using the user specified feed rates only. However on the actual machine tool the acceleration and the deceleration of the tool come into play and this will invariably be different than the ones calculated by VisualMill. Use the machining time calculated by VisualMill as a ball park estimate.