Crystallinity control in parts produced from stereolithography injection mould tooling

Abstract

Abstract

The use of moulds produced by stereolithography (SL) for injection moulding provides a quick route to manufacturing a low volume of parts without expensivehard tooling. However, these parts have been shown to exhibit different material property characteristics than those produced from metal tooling. The aim of the present work is to research methods that would allow SL moulds to produce parts of similar material property characteristics to those from conventional metal tools. This work has identified that the different part characteristics are due to differing levels of crystallinity developed in the parts from the comparative mould varieties (SL and metal). These crystallinity differences have been associated with the cooling rates imparted owing to the thermal properties of the mould material. The latter part of this work concerns controlling and manipulating this degree of crystallinity. After a discussion of possible methods, two approaches are taken to modifying the crystalline content of parts produced by SL moulds. One of the approaches is material based, the other concerns the injection moulding process. Differential scanning calorimetry (DSC) is used to quantify the resulting levels of crystallinity in the parts. The results show that by process modification it is possible to produce parts by SL moulding that possess a similar crystalline content to those moulded from metal tooling. The use of modified materials allows parts created in SL and metal tools to be of a consistent crystalline content. The work concludes that not only are SL moulds capable of producing parts that are more like those from metal moulds but also present some unique opportunities that have been demonstrated to be unachievable in metal moulds.