The final project paper discusses the production procedure of a thermoplastic product with injection molding. The emphasis of the paper is on the calculation and determination of suitable and optimal molding parameters, which is also the subject under discussion. On the basis of technical specifications obtained from a client, a PBT polymer product was moulded with various parameters, i.e. by changing speed, and taking into account the switch-over and holding pressures. A suitable tool made by the company for this purpose was used to carry out the technological test of the product ordered by our client. Based on the test, we provided our findings which were taken into account by the company before the production of the product commenced.