Reinforced vacuum system component

A rotor assembly 1 for a turbo-molecular pump comprises an annular hub 2 and one or more annular arrays of substantially identical rotor blades 3 each extending radially from a rotor blade root 4 contiguous with the hub to a rotor blade tip 6. The hub and blades form a unitary structure. Each rotor blade comprises a continuous fibre reinforced matrix material, and has a continuous fibre which extends from the blade into the hub to increase the strength and/or stiffness in this region. A polymer matrix material is used for the structure. The blade may include a lattice core, and may be 3-D printed using continuous composite filaments and a fused filament matrix. The type and/or lay-up of fibres may be different in different portions of the blade depending on the mechanical properties required.