Drilling process optimization for graphite/bismaleimide–titanium alloy stacks

In this study, the drilling process of graphite/bismaleimide-titanium alloy (Gr/Bi–Ti) stacks was optimized in terms of machined hole quality and machining cost. The drilling experiments were conducted by using two different cutter materials, HSS-Co and carbide. Drilled hole quality parameters include surface texture, titanium burrs, hole diameter, cylindricity, and roundness deviation. Machining cost was estimated through drill wear experimentations. A multiple objective linear program was used to optimize drilling feed and speed not only to maximize each hole quality parameter to the greatest extent possible but also to minimize machining cost. Optimum process conditions for achieving desired hole quality and process cost were found to be a combination of low feed and low speed when using carbide drills, and high feed and low speed in drilling with HSS-Co drills. The sensitivity of weighting factors on the feasible process conditions depends on the optimal point position and distribution of each objective.