Wear of a Tool in Double-Disk Lapping of Silicon Wafers

Silicon wafers are the most widely used substrates for fabricating integrated circuits. A sequence of processes is needed to turn a silicon ingot into silicon wafers. One of the processes is flattening by lapping or by grinding to achieve a high degree of flatness and parallelism of the wafer [1, 2, 3]. Lapping can effectively remove or reduce the waviness induced by preceding operations [2, 4]. The main aim of this paper is to compare the simulation results with lapping experimental data obtained from the Polish producer of silicon wafers, the company Cemat Silicon from Warsaw (www.cematsil.com). Proposed model is going to be implemented by this company for the tool wear prediction. Proposed model can be applied for lapping or grinding with single or double-disc lapping kinematics [5, 6, 7]. Geometrical and kinematical relations with the simulations are presented in the work. Generated results for given workpiece diameter and for different kinematical parameters are studied using models programmed in the Matlab environment.

Effects of Carrier Material and Design on Microalgae Attachment for Biofuel Manufacturing: A Literature Review

Continuous use of petroleum derived fuels is widely recognized as unsustainable due to depleting supplies and the accumulation of greenhouse gases in the environment. Renewable, carbon neutral transport fuels are needed for environmental and economic sustainabilities. Algae have been demonstrated to be one of the most promising sources for biofuel production. However, large-scale algae production and harvesting for energy manufacturing are too costly using existing methods. The approach of growing algae on solid carriers is innovative and can potentially lead to cost-effective manufacturing of algae biofuels. As cells approach to the solid surface, many factors come in to influence microbial attachment such as the surface wettability, free energy, polarity, roughness and topography. Surface wettability plays an important role in the initial cell attachment. For further contact, surface free energy and polarity are more directly related to cell-substratum attachment strength. Surface roughness and texture are species-specific parameters and have been applied widely in attachment studies.

Optimization on the Production of Variable Thickness Aluminium Tubes

The variable thickness tube drawing is a new modification in the tube drawing methods which enables production of axially variable thickness tubes faster and easier in comparison with other similar methods like radial forging or indentation forging. The production of this type of tubes can be used in optimum design of mechanical parts which do not necessarily need constant thickness along the axis of tube and this method can strikingly reduce the overall weight of parts and mechanical assemblies like cars. In this paper, the variable thickness tube drawing were parameterized in a MATLAB code and optimized with the Ls-Opt software as an optimization engine and Ls-Dyna as a FE solver. The final objective of this optimization study is to determine the minimum thickness which can be produced in one step by this method with various tube dimensions (tube thickness and outer diameter). For verification of results, some experiments were performed in the tube drawing machine which was fabricated by this research group and acceptable correspondence was observed between numerical and experimental results.

Application of Electric Current in Friction Stir Welding

Friction Stir Welding (FSW) is a relatively new joining technique and has many applications. In FSW, heat generated due to friction between FSW tool and work-piece material softens the material and allows the materials in work-pieces to be stirred and joined together. FSW allows the work-pieces to be joined without reaching the melting point of the material, thus resulting in better welds. However, a large amount of mechanical energy has to be consumed for FSW of high-strength, difficult-to-weld metals such as titanium alloys. Hence, new FSW methods should be investigated to reduce the required energy. In this study, an innovative electrically-enhanced friction stir welding (EEFSW) has been developed. Electric current is passed in welding coupons of Aluminum 6061 plates and its effect on welding process and welds are examined. The results indicate that, with the aid of electric current, improvement in welding speed and reduction in energy consumption is obtainable, which enhances the productivity and widens the range of applications of FSW. Weld properties are found to be affected by the introduced current as well.

Manufacture of Aerospace Components With Pressure Welding

Pressure welding technology is a solid state bonding process and generally involves heating the metal surfaces and then applying a suitable amount of axial pressure. In this state the metal components being joined undergo only microscopic deformation and the joining region is homogeneous and complete metallurgical bonding is possible without secondary materials or liquid phases. In the present work, pressure welding of titanium alloys has been investigated to fabricate several aerospace components with various complex configure. The result shows that the pressure welding method has been successfully applied with blow forming for near net shape forming of aerospace components, including high pressure tank for attitude control of spacecraft, and other lightweight structural panels.

Method for Evaluating Machining Toolholder-Spindle Unbalance Due to Chips at the Toolholder Interface

Machining process monitoring method is developed for detecting and diagnosis of the presence of chips at the toolholder-spindle interface. Although toolholders can be simply balanced before they are placed in the spindle, there can be some balancing problems remaining when one or more loose machining chips are attached at the toolholder-spindle interface(s) during a tool change. A method is developed by considering the natural and geometric unbalances of the toolholder-spindle system combined with an analysis of the toolholder tilt due to the presence of loose machining chips around the spindle. The method can be integrated on-line as a real-time expert diagnostic system for toolholder tilt due to the presence of loose machining chips at the spindle nose. The expert diagnostic system makes intelligent decisions on toolholder unbalance and concerns with chips at the interface that result in unwanted tilting and vibrations. The tool unbalance algorithm was able to monitor the toolholder tilting according to the results of this study.

Effects of Deformation Speed and Type of Alloy on Friction and Lubrication by Tip Test

The tribological conditions in cold forging operations are extremely severe, especially with high ram speed, due to large surface expansion and normal pressure at the tool/workpiece interface. The effects of deformation velocity and type of alloy were determined in the two sets of experiments carried out in the present study. In the first set, two different deformation speeds of 0.1 and 1mm/s were used for the aluminum alloys of 6061-O, 1050-O and copper alloys tests. The results were further confirmed with the second sets of experiments using AA2024 and AA6061 and three deformation speeds of 0.1, 1 and 5mm/s to evaluate the performance of each lubricant under increasing ram speed. Four lubricants such as grease, corn oil, VG100 and VG32 were used. While all the lubricants show a reduction in maximum load with increasing deformation speed, grease shows a rise in the maximum load from zero to a maximum at a deformation speed of 1mm/s and then descends gradually to a minimum load at a speed of 5mm/s for AA2024-O and AA6061-O. Since the load reduction seen, with grease as lubricant, is probably due to thermal softening, it will not be considered a desirable lubricant under increasing deformation speed because of the adverse effects on the tooling. It is found that in choosing lubricant for cold forging operations the type of workpiece material and deformation speed should be properly considered. Of the liquid lubricants (corn oil, VG100 and VG32) considered, corn oil shows the best lubricant for cold forging operations of copper, aluminum 6061-O, 1050-O and 2024-0 under increasing speed magnitude.

Hot Forming Technique and Its Equipments for Ultra High Strength Steel

Hot forming of ultra high strength steel is an advanced forming technique which can not only represent the best solution to increasing the strength-to-mass ratio of sheet components, but also meet the need of higher passive safety and weight reduction. Based on independently developed mass production line of hot forming, its key forming and quenching technique and relative equipments are proposed and described, including multi-step and one-step method, die manufacturing with cooling system, continuous heating furnace and integrated manufacturing system composed of the advanced interdisciplinary technology of machining, electronic control, material and chemical engineering. Then the automobile body components are produced by the developed equipments of hot forming and moreover their mechanical properties are investigated. The typical tensile curve of the quenched components shows that the yield stress of the hot forming component is over 1000MPa, and the strength limitation is over 1600MPa. The three-point bending testing of the part is implemented. These experimental results indicate the validity of the developed technique and equipments.

Processing of Nanodiamond Loaded Poly(Lactic Acid) Co-Continuous Porous Structures

Porous poly(lactic acid) PLA materials are highly demanded as scaffolding templates in tissue engineering applications. In this study, a protocol for creating co-continuous porous PLA structures with nanodiamond (ND) as additive was investigated. First, a ternary blend of PLA/PS/ND was prepared with different mixing ratios under different mixing conditions. Next, a post annealing stage was applied to coarsen the phase structure. Finally, the PS phase was sacrificially extracted, leaving a porous matrix. The experimental results showed that ND can be an effective compatiblizer for increasing the miscibility between PS and PLA and reducing the phase size. It was further found that the post annealing conditions significantly affect the distribution of ND particles in the blend and finally in the porous PLA structure.

Comparison of Superabrasive Tools in Rotary Ultrasonic Machining of Stainless Steel

Many experiments on rotary ultrasonic machining (RUM) have been conducted to study how input variables (including tool rotation speed, ultrasonic power, feedrate, and abrasive size) affect output variables (such as cutting force, torque, surface roughness, and edge chipping) by using diamond tools. However, a literature review has revealed that there is no reported study on CBN tools in RUM. This paper, for the first time in literature, presents an investigation of RUM of stainless steel using CBN tools. Firstly, an introduction of superabrasive materials and RUM principle was provided. After presenting the experiment procedures and workpiece properties, it reports the results on tool wear, cutting force, torque, surface roughness in RUM of stainless. Finally, it discusses and compares the performances of diamond and CBN tools in RUM of stainless steel under certain conditions.