Optimization of an autonomous robotic drilling system for the machining of aluminum aerospace alloys

This paper aims to identify the capability of a highly flexible industrial robot modified with a high-speed machine spindle for drilling of aluminum 6061-T6. With a focus on drilling feed rate, spindle speed, and pecking cycle, the hole surface roughness and exit burr heights were investigated using the Taguchi design methodology. A state of the art condition monitoring system was used to identify the vibrations experienced during drilling operation and to establish which robot pose had increased stiffness, and thus the optimum workspace for drilling. When benchmarked against a CNC machine the results show that the CNC was capable of producing the best surface finish and the lowest burr heights. However, the robot system matched and outperformed the CNC in several experiments and there is much scope for further optimization of the process. By identifying the optimum pose for drilling together with the idealized settings, the proposed drilling system is shown to be far more flexible than a CNC milling machine and when considering the optimized drilling of aerospace aluminum this robotic solution has the potential to drastically improve productivity.

Evaluation of Forging Process Induced Residual Stress in Aluminum Die Forgings

Aircraft structural components are being produced from forgings with increasingly complex geometries in a wide range of aerospace alloys. The forging process involves a number of steps required to attain favorable material properties (e.g., heat treatment, rapid quench, cold work stress relieving, and artificial aging). These processing steps, however, also result in the introduction of bulk residual stress. Excessive bulk residual stresses can have negative consequences including: part distortion during machining and/or during service, reduced crack initiation life, increased crack growth rates, and an overall reduction in part life. This presentation will summarize recent work related to quantifying and accounting for residual stress in aluminum die forgings. Key residual stress engineering concepts will be described. Since the artifacts studied are associated with an aircraft supply chain (multiple parts and multiple lots), the results are relevant to the aerospace community. Overall, the results show that forging residual stress is a repeatable phenomenon with approximate repeatability less than 5% of A-basis yield strength.

Investigation of Tensile and Compressive Mechanical properties of Typical Aerospace alloy Materials

For the typical aerospace alloys, the mechanical properties of TC4 titanium alloy and 7075 aluminum alloy at different loading rates were investigated by uniaxial tension and compression experiments. The fracture microscopic morphology of two alloys was compared and analyzed by using scanning electron microscope. In addition, the experiment also combined infrared thermography technology (IRT) to compare and analyze the temperature variation characteristics of TC4 titanium alloy specimens under the same tensile and compressive loading rate. The research results show that the mechanical properties of TC4 titanium alloys are superior to 7075 aluminum alloys under the same tensile and compressive loading rate. The constitutive equations considering power-law hardening and tensile loading rate are derived to express the yield flow stress behavior.

Optimization of an Autonomous robotic drilling system for the Machining of Aluminum Aerospace Alloys

This paper aims to identify the capability of a highly flexible industrial robot modified with a high-speed machine spindle for drilling of Aluminum 6061-T6. With a focus on drilling feedrate, spindle speed and pecking cycle, the hole surface roughness and exit burr heights were investigated using the Taguchi design methodology. A state of the art condition monitoring system was used to identify the vibrations experienced during drilling operation and to establish which robot pose had increased stiffness, and thus the optimum workspace for drilling. When benchmarked against a CNC machine the results show that the CNC was capable of producing the best surface finish and the lowest burr heights. However, the robot system matched and outperformed the CNC in several experiments and there is much scope for further optimization of the process. Overall the proposed drilling system is far more flexible than a CNC milling machine and when considering the optimized drilling of aerospace aluminum this robotic solution has the potential to drastically improve productivity.