An appts. to produce continuous uni-dimensional polyurethane shaped bodies has at least two mixt. heads for the polyurethane reactive components, working alternately. The change-over valves set the working for mixing and conditioning. A common dosing pump for each component is connected to each mixing head, and a common conditioning pump for each component is connected to each mixing head. The valves at the mixing heads, at the inlet for the components, switch the feed between the pumps according to the mixing or conditioning action. During conditioning at each head, a feedback is active for each component. Also claimed is an operation where the components are fed in common, but delivered in separate assemblies according to the mixing or conditioning mode at each head.