In machining of composite materials, little research has been conducted in the area of optimal replacement time of the cutting tool in terms of cost and availability.

Due to the fact that tool failure represents about 20% of machine down-time, and due to the high cost of machining, optimization of tool replacement time is thus fundamental.

Finding the optimal replacement time has also positive impact on product quality in terms of dimensions, and surface finish.

In this paper, we are finding the tool replacement time when a tool is used under constant machining conditions, namely the cutting speed, the feed rate, and the depth of cut, during turning titanium metal matrix composites (TiMMCs).

Despite being expensive, MMCs are a new generation of materials which have proven to be viable in various fields such as biomedical and aerospace industrial. Proportional Hazard Model (PHM) is used to model the tool’s reliability and hazard functions using Exakt software.

Experimental data are obtained and used to construct and validate the PHM model, which is then used in decision making.

The results are discussed and show that finding the optimal replacement time of the cutting tool is valuable in saving cost of machining process and maximizing the tool availability.