Yasser Zedan

ON CHIP FORMATION DURING DRILLING OF CAST ALUMINUM ALLOYS

Aluminum alloys are widely used in several applications. Cast alloys are usually considered to be brittle materials leading to short chip formation during machining. Although they can be produced near net shapes, products made of these alloys very often require some machining. The purpose of this study is to evaluate the machinability of A319 and A356 under T0 and T6 conditions. The machinability was assessed during the dry drilling machining process, with the machinability indexes including the chip form, chip breakability, and the cutting forces. It was found that A319 and A356 exhibit different machinability behaviors, especially under the T6-condition in terms of force requirements, chip breakability, and chip segmentation. The chip grain size obtained by X-ray diffraction techniques was also studied and correlated to the machining conditions. It was also found that both the microstructure of the workpiece materials and the machining conditions significantly affect the chip formation mechanism, and so the machining parameters could therefore be selected to promote a chip form that is easily manageable in production.

Machining Burrs Formation & Deburring of Aluminium Alloys

Although the machinability of most aluminium alloys can be classified as relatively easy when the tool wear and the cutting energy are considered, these materials could however raise some concerns when the chip formation and the burr formation are of concern. Burr formation, a phenomenon similar to chip generation, is a common problem that occurs in several industrial sectors, such as the aerospace and automobile sectors. It has also been among the most troublesome impediments to high productivity and automation, and large‐ ly affects the machined part quality. To ensure competitiveness, precise and burr-free com‐ ponents with tight tolerances and better surface finish are demanded. Intensive research conducted during the last decades has laid out the mechanisms of burr formation and de‐ burring in a very comprehensive fashion, and has introduced integrated strategies for burr prevention and minimization. Despite all the improvements realized, there are still many challenges encountered in understanding, modeling and optimizing the burr formation process and size, through production growth and cycle time reduction. Furthermore, acquir‐ ing a solid knowledge on deburring methods and the links between them and burr size is strongly recommended.

Effects of lubrication modes on part quality during drilling 6061-T6 aluminium alloy

The main objective of this research is to investigate the effects of the cutting fluid and application mode (dry, mist and flood drilling) and its interaction with cutting parameters on part quality during the drilling of 6061-T6 aluminium alloys. The part quality criteria include the burr form and sizes, and surface finish as well as the cutting forces generated. A multi-factorial design (DOE) is used to plan test and statistical analyses are used to determine the effects of lubrication and cutting parameters on part quality. The parameters governing the part quality are different from those governing the cutting force; the burr height and the surface roughness are mostly influence by cutting speed, cutting fluid modes and feed rate while the cutting force is mainly determined by the feed rate. It is found that dry machining and mist machining can produce parts whose quality is comparable to what is obtained in wet machining, when optimal cutting conditions are used.

Burr Size Minimization When Drilling 6061-T6 Aluminum Alloy

The burr formation mechanisms strongly depend on the machining methods as well as cutting conditions. Cutting fluids play significant roles in machining, including reduction of friction and temperature. Using a cutting fluid, however, degrades the quality of the environment and increases machining costs. In the present work, initially the effects of cutting fluid application (dry, mist and flood) and their interaction with cutting parameters on the burr size during drilling of 6061-T6 aluminum alloys were investigated using multi-level full factorial design. Second-order non-linear mathematical models were developed to predict burr height for various lubrication modes. The accuracy of the regression equations formulated to predict burr height when using different lubrication modes has been verified through carrying out random experiments in the range of variation of these variables. A procedure was developed to minimize burr size for drilling holes by presenting the optimal levels of process parameters. Taguchi optimization method based on L9 orthogonal array design of experiment was then used which has shown very accurate process parameters selection that leads to minimum burr height. According to experimental study, it was observed that dry and mist drilling can produce parts with quality comparable with those obtained in wet drilling when using the optimal cutting conditions. In addition, increase in cutting speed and feed rate exhibits a decrease in burr size.© 2012 ASME