Abstract: A method of forming an article comprising in combination the steps of: constructing in a computer (6) memory a first datafile 60) which is a definition of a three dimensional volume model of an article; executing a computer program (42), which reads the first datafile (60) and performs an algorithm which deconstructs the three dimensional volume model to produce a second datafile (62) comprising a string of sequential relative spatial co-ordinates describing a tool path (90,91) through the three dimensional volume model of the article; operating a multi-axis welding robot (2) to position the welding head (16) relative to the worktable (12) such that the relative movement follows the path (90,91) defined by the second datafile (62). The operation of the welding head (16) also being controlled to deposit a weld bead as it follows at least a part of the path to build up a solid representation of the three dimensional volume model of the article.