Using additive manufacturing with blow moulding to facilitate accurate consumer testing

A South African entrepreneur needed a fast and accurate route to consumer testing for a design of phlegm collection bottle for long-distance runners. Vaal University of Technology was presented with an initial product concept which had to be developed into a fully functional prototype required for field trials. The idea was converted into a practical product proposal and modelled using a 3D computer aided design (CAD) system. The CAD data were used for laser sintering of polyamide to produce an initial prototype for appearance and ergonomic evaluation. For product testing in the field, a short run of fully functional prototypes in thin-walled low density poly-ethylene (LDPE) was required. This required a further design iteration and the production of tooling for the blow moulding process. A novel hybrid modular approach to tool manufacture was followed, where the outer frame of the tools were machined in aluminium and the tool inserts were laser sintered in AlumideTM. Blow moulding trials were undertaken in LDPE which revealed a number of positive and negative issues. The rough surface of the tool inserts produced a desirable textured surface in the resultant blow-moulded bottles but also prevented a clean “shut-off” between the two halves of the tool. This allowed air to escape from the cavity along the split plane, creating unwanted holes in the bottles. In addition, the low thermal conductivity of AlumideTM resulted in an unwanted overheating of the tools. Strategies were identified to overcome these issues and these are explained in the paper.