Challenge

A catheter balloon was formed by pressurised inflation in a heated mould. The resulting balloon shape form was irregular. In addition, process time was unacceptably long.

Engineering Approach

A transient thermal FE study was conducted which identified poor and irregular heat transfer within the mould. A materials study followed and identified that the mould material had been selected primarily on the basis of conductivity. Thermal diffusivity was found to be the critical material property. Candidate materials were evaluated on this basis and an alternative material selected.

Outcome

The critical material property was thermal diffusivity, not simply thermal conductivity. The revised mould corrected the balloon shape form and cycle time was reduced by 70%.