The objective of this paper is to describe a method to determine the scanning strategy for a CAD known mechanical part. The Research Center for Automatic control in Nancy (France) has initiated a project to create an automatic 3D digitizing system. Our previous papers focused on the visibility determinations using spherical geometry in a 3 ½ axis environment. Algorithms and results allowing us to continue the project and to improve this approach are presented. This communication is dedicated to a path planning method, including collision avoidance. The different algorithms presented were developed for a 5 degrees of freedom (DOF) but due to our digitizing environment, they are applied to a 3 ½ axis scanning cell that is composed of a plane laser sensor integrated onto a CMM by means of a mechanical indexed system. This enables the sensor to be directed in four directions around Z. Compared to a 5 axis system, the association between each indexed position and some parts of the piece that will be digitized from the sensor position has to be found. For each step of this methodology, algorithms are illustrated by a case study.