Abstract: A method of making a pipe string from separate pipes of arbitrary length welded end to end wherein the joints are positioned off forbidden zones. A reference model of the pipe string having the forbidden zones marked thereon and a working model of the arbitrary pipe lengths arranged in random sequence so as to exceed the length of the desired pipe string are prepared, and by shifting the working model with respect to the reference model, a mutual arrangement is found where all pipe joints lie off the forbidden zones marked on the reference model and the excess portions of the beginning and trailing pipe lengths which are to be cut off determined. An automatic line for measuring the pipe lengths, storing measured pipes, welding the pipe lengths together, and cutting off the excess parts in accordance with the working model is used to make the pipe string. A computing device for calculating a working model of the pipe string is also disclosed.