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. The seamless alignment between the Cap and Housing of this Pen was the key challenge that the prototype testing delivered this point.
Prototyping to Production Step By Step:
Firstly, an aluminum prototype was milled to verify appearance and the seamless alignment, the aluminum prototype delivered the feasibility of seamless alignment, then two titanium prototypes were followed for the final testing.