  The aim of this paper is the isotropic design of a hybrid morphology
dedicated to 3-axis machining applications. It is necessary to ensure the
feasibility of continuous, singularity-free trajectories, as well as a good
manipulability in position and velocity. We want to propose an alternative
design to conventional serial machine-tools. We compare a serial PPP
machine-tool (three prismatic orthogonal axes) with a hybrid architecture which
we optimize only the first two axes. The critrerion used for the optimization
is the conditioning of the Jacobian matrices. The optimum, namely isotropy, can
be obtained which provides our architecture with excellent manipulability
properties.
