The use of stereolithography tools for injection moulding allows plastic parts to be produced in a very short time due to the speed of mould production. The process's greatest advantage is that it can provide a low volume of parts that are produced in the same material and process as parts that would be produced by the conventional hard tooling, but in a fraction of the time and cost. However, this work has demonstrated different rates of polymer shrinkage are developed by parts produced by stereolithography tools and conventional tooling methods. These revelations defy the greatest advantages of the stereolithography injection moulding tooling process—the moulded parts do not replicate parts that would be produced by conventional hard tooling. The aim of this work is to acquire an understanding of the mechanisms in stereolithography tooling that induce these different part properties and develop a modification of the process that could change these, which would allow the moulded parts to demonstrate characteristics like those produced by conventional means.