| Environmental, health, and safety issues related to cutting fluids have motivated many research attempts to develop dry machining operations. Open face cutting processes, such as turning and boring, are often performed dry without many changes to the process setup. Usually, just by applying a good coating, sufficiently resistant to generated temperatures, and by making slight changes to tool geometry, even dry turning of steel can be achieved. However, in closed face operations, the challenge of achieving dry machining becomes much more difficult due to the significant role that fluid plays in the process.; Common techniques applied for developing dry drilling operations include modification of tool geometry, development of new coatings, and adding different alloying elements to the workpiece material. These techniques have had some success for materials such as cast iron. However, it is still imperative to develop successful dry drilling operations for aluminum since aluminum is becoming more and more popular in the automotive industry due to its low density.; A new technology for dry deep hole drilling of aluminum by applying axial tool modulations is developed in this research. Previous attempts in this direction were only partially successful due to insufficient amplitude of the tool's motion or vibration problems due to high oscillating mass. In this research a new approach that uses a magnetostrictive tool holder is employed. Magnetostrictive materials are known for producing relatively large motions with fairly high force. A completely new piece of equipment, a tool holder/actuator assembly that incorporates a magnetostrictive actuator, has been designed, manufactured, and implemented. It is able to generate sufficient oscillatory motions at the tip of the drill tip to modulate the chip size and deterministically break chips under appropriate modulating conditions. It is postulated that smaller chips generated by employing axial drill modulations are easier to evacuate through the drill flutes in the absence of a cutting fluid. |
