A study of the effect of conventional drilling and helical milling in surface quality in titanium Ti-6Al-4V and Ti-6AL-7Nb alloys for medical applications

Abstract

In the manufacturing of a medical device, may occur the need to make a hole with a specific function. Among current methods, conventional drilling (CD) referred in this work as drilling (D) and helical milling (HM) are two options with different potential. When making the hole, it is important to choose the most suitable method to obtain the desired geometry and ensure the functionality of the device. This work aims to analyze surface parameters as, arithmetic average height (R a ), the maximum height of the profile (R t ), the average peak to valley height (R z DIN), chip formation and the geometric deviation of holes obtained by the previously referred manufacturing processes. The specimens, with cylindrical geometry, were made of titanium alloys, Ti- 6Al-4V and Ti-6Al-7Nb, currently used in the manufacture of medical devices. For this purpose, holes were made in a machining centre with different feed rate (F) for both methods and in the value of vertical step (a p ) in HM. The results obtained demonstrate that, at lower F and a p , HM presents better results. The Ti-6Al-7Nb alloy presents better roughness results compared to Ti-6Al-4V, validating it as a material able to be used in medical devices according to the fact that, a lower roughness is associated with higher corrosion resistance and fewer fatigue problems derived from it in components. By the work carried out, can be concluded that the roughness values obtained in HM are lower to those obtained by D making HM as a better option in hole making.