A layout design of an excavator front is a coupled design. Parameters of the layout design are coupled each other. So it is difficult to make decisions to set the parameters of the layout of an excavator front. We analyze the parameters of the layout design of an excavator front. We regroup the parameters as interface groups. And we suggest a new design process which is based on the interface groups. And we redesign user-interfaces of the Knowledge based Excavator Design System(KEDS).