Experimental Investigation On Machining Performance During Orbital Drilling of CFRP

As the most promising CFRP hole making method, orbital drilling is widely concerned. This paper aims to understand the influence of the cutting parameters, tool diameters and ratio between milling and drilling (Rm&d) on thrust force, cutting temperature, tool wear and machining quality in CFRP orbital drilling. The effects of cutting parameters on thrust force and cutting temperature were studied by orthogonal experiments, and experiments were performed to investigate the variations of tool diameters, ratio between drilling and milling on thrust force, cutting temperature, tool wear and machining quality. The experimental results show that the tangential feed rate has no apparent effects on thrust force, but it appreciably impacts on the cutting temperature. The selection of tool diameter and the Rm&d has specific influence on tool wear, machining quality and cutting temperature. The result is helpful for selecting cutting parameters and tool diameters for high quality holes machining in CFRP orbital drilling.

Machining temperature comparative analysis of end mill and novel tool in orbital drilling of CFRP composite

Applying Carbon fiber-reinforced plastics (CFRPs) instead of traditional materials can improve the structural strength and reduce the weight of the spacecraft. However, the defects and the rejections still impede the wide application of CFRP for the contrasting thermo-mechanical properties of fibers and resin. A lower machining temperature can reduce burrs and delamination effectively. To study the cutting temperature of orbital drilling in CFRP, the processing temperature of the conventional orbital drilling (COD) was compared with the novel orbital drilling and reaming tool (ODR), and a heat transfer model considering the influence of convective heat transfer on cutting temperature was also proposed in this research, which can explain the reason of the novel tool with a lower cutting temperature. On the basis of the analysis of the kinematic mechanisms, a cutting force prediction model for the process of orbital drilling was presented. The three-dimensional, unsteady state, nonhomogeneous partial differential heat transfer equation in polar coordinates was established, and solved with the finite difference approach. The results show that the predictions of models are coincided to the experimental data, and ODR tool can reduce the processing temperature of orbital drilling effectively.

Influence of the Hole Surface Integrity on the Fatigue Strength of an Aluminium Drilled Part

Fatigue strengths of aluminium 2024-T351 open-hole specimens drilled by axial and orbital drilling processes are compared. Two drilling diameters (Ø) are studied: 6.35 mm and 9.53 mm. Surface integrity characterization tests are conducted in order to study the link between drilling processes, surface integrity and fatigue life. Fatigue test results show an increase of the fatigue life for specimens drilled by axial drilling for Ø = 9.53 mm and no significant difference in fatigue life between the two drilling processes for Ø = 6.35 mm. Surface integrity results show no impact of the roughness on the fatigue strength but a potential positive influence of the hole microhardness on the fatigue life.

3D Finite Element Assisted Numerical Simulation of Orbital Drilling Process of Ti6Al4V

Drilling is one of most executed manufacturing operations to assist the assembling of different engineering components. In orbital drilling process, a milling tool is rotating along its own axis in combination with the spiral rotational movement. The rotation of tool about its own axis is with high rotational speed, but the spiral movement of tool is at low rotational speed. These rotational movements generate a hollow geometry when moved in combination. Orbital drilling process is emerging as a viable drilling process when burr formation has to be reduced from the metallic workpiece. It is gaining more popularity in the aerospace industry due to its ability to machine holes in difficult to cut alloys, composites and composite stacks. Major advantages of orbital drilling are linked with efficient chip evacuation, reduction in heat build-up and low thrust forces due to its intermittent cutting nature. The cutting forces generated during the process can be taken as a significant output parameter that play a vital role towards the overall performance of the cutting process. Controlling the cutting forces under threshold value can improve the overall machining efficiency by limiting associated deflections, tool wear and energy consumption. The current paper aims to study the orbital drilling process using finite element (FE) assisted numerical methodology. The study will utilize different orbital drilling parameters such as spindle speed, orbit speed and axial feed rate, and explore their influence on the over all machining process.