Fibre-reinforced composites consist of three key components: the reinforcing fibres, the matrix and the interface between the fibre and the matrix. The efficient impregnation of the reinforcing fibre bundle by the matrix is a primary prerequisite for the production of advanced fibre-reinforced composites. This process can be significantly enhanced by spreading the filaments in the reinforcing fibre bundle. The authors previously reported on a manual technique for spreading the filaments in a bundle. This involved subjecting a fibre bundle to a series of reciprocating motions over a rod. The effect of releasing the tension on the bundle was also considered. On the basis of the observations made in the previous study, a mechanised rig was designed, manufactured and optimised to enable the lateral spreading of the filaments in a bundle of E-glass fibres. A Taguchi-based approach was used to optimise the variables on the rig such as the number and configuration of rollers, haul-off speed of the fibre bundle, pre-tension in the bundle and the rotational speed of the roller carrier hub. The maximum degree of fibre spreading achieved for a commercially available 2400 tex E-glass fibre bundle was 250%.