Injection moulding is a manufacturing process which is suitable for high-volume production of polymer parts. These products are final and do not require any additional operations. The quality of the final product is significantly affected by the surface of the mould cavity. This paper reveals the influence of cavity surface roughness and technological parameters on the flow length of polyoxymethylene (POM) into the mould cavity. These results indicate that costly finishing methods used for working of mould cavities can be replaced with less expensive manufacturing methods. Furthermore, it might be possible to shorten the time necessary for the production of the injection mould.