This project conducted scientific investigation on how tension applied on the cut chip in machining affects mechanics and dynamics of cutting and improves machineability of difficult-to-cut materials. In conventional machining processes, cutting effort is directed towards shearing the material and to overcome the friction forces. Energy consumed for shearing generates the chip; however, energy is wasted on friction as the cut chip flows on the rake face. In this project, the chip is pulled by a mechanical pulling device to cancel the effect of friction forces during machining. Theoretical and experimental investigations are conducted to understand how pulling the chip with tension improves machineability.

Firstly, micro-textured cutting inserts are designed to control the flow of the chip on the rake face and to navigate it successfully towards a puling system. It is found that engraving groves on the rake face of the cutting tool can effectively suppresses side curling of the chip. Thus, guide grooves can be used to generate straight and continuous chip in machining ductile materials. Such grooved tool tip geometry helps eliminate chip-jam, and more importantly allow control of the chip flow direction. The depth and width of "guide" grooves are key design parameters and play a critical role in chip control. Theoretical and experimental investigations are conducted to understand mechanics of cutting with guide-grooved cutting inserts. It is found that guide grooves can alter chip flow direction consistently for various cutting conditions for ductile materials such as low carbon steel, copper, and aluminum. Oblique cutting models can be adapted to capture the physics of the cutting processes.

Next, mechanics of the cutting process assisted by chip pulling is investigated. When chip is pulled with tension during cutting, the chip pulling force (tension) reduces/cancels the friction force component on the rake face. As a result, it allows machining with effectively "zero" friction force. The project uncovered that eliminating adverse effects of friction force by pulling the chip significantly improves the cutting mechanics. It reduces cutting forces and the overall cutting energy. Thus, chip-pulling improves machinability of difficult-to-cut materials. Experimental investigations are conducted to demonstrate such improvement. Within the scope of the project, physics-based models are also developed to capture the fundamental mechanics of this "chip-pulling cutting" process and for maximizing its advantage. Developed models are validated through machining tests.

Finally, dynamics of the machining process is also investigated. Self-excited chatter vibrations pose great limitation on the attainable productivity of machining processes. They occur due to flexibilities in machine/tooling/workpiece structure, and chip pulling can potentially improve the chatter stability margins. Novel control techniques are developed to actively suppress chatter vibrations and attain larger material removal rates in turning. It is found that regenerative effects can be suppressed to improve chatter stabilyt margins of the process to attain greater material removal rates.

Overall, this project generated new knowledge to improve productivity of the machining processes. In particular, chip pulling cutting has been developed as a novel machining process to attain better machineability in difficult-to-cut materials. New scientific knowledge generated in this project is disseminated to the manufacturing community through several conference and journal publications. Collaboration with the industrial partner (The Boeing Company) help better understand limitations in applying the developed techniques in practice in aerospace and energy sections and contributed to the broader impact of the project.

Last Modified: 08/24/2021
Modified by: Burak Sencer