1. Titanium alloy had fairly low thermal conductivity that probably resulted in burning or chip adhesion to cutting tool during milling.
2. Titanium alloy had less stiffness than many other metals, which led to the risk of distortion and cutting tool jarring during the milling.
3. Seamless alignment between Cap and Housing of this Pen was the key challenge that the rapid prototypes delivered this point.
Prototype to Production Step By Step:
Firstly, an aluminum prototype was milled to verify appearance and seamless alignment, the aluminum prototype delivered feasibility of seamless alignment, then two titanium milled prototypes were followed for final testing.