1. Titanium alloy had fairly low material thermal conductivity that probably resulted in burning or chip adhesion to cutting tool during its milling.
2. Titanium alloy had less stiffness than many other metals, which led to the risk of distortion and cutting tool jarring during milling this metal.
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 CNC milled to verify appearance and seamless alignment between Cap and Housing, the milled aluminum prototype delivered the feasibility of seamless alignment, then a titanium prototype was milled for final testing before volume production.