Creating textures on abrasive wheels is a strategy that allows a significant improvement in grinding operations. The reduction of the internal stresses in the workpiece and the temperature during the grinding operation generates an increase in the dimensional accuracy of the workpiece and a longer tool life. Textured abrasive wheels can be produced in many different ways. Depending on the processing method, the dimensional accuracy of the tool and its applicability is changed. Some methods can produce tools with three-dimensional grooves; there are also methods that are employed for the re-texturing of grooves after the grooved zone wears out. In the literature, the benefits of textured grinding wheels over traditional wheels have been extensively discussed. However, information on the particularities of texturing methods is still lacking. To clarify the advantages, limitations, and main advances regarding each of the groove production methods, the authors of this article carried out a systematic review. The objective of this work is to establish the factors that are affected by groove production methods and the technological advances in this area. The benefits and drawbacks of various grooving techniques are then reviewed, and potential study areas are indicated.
One of the most important negative consequence in the fusion welding processes is the generation of tensile residual stresses in welded joints. The main goals of this work are to determine the optimal combination of welding parameters to minimize the residual stress level and the influence of each welding parameter in that feature to weld 6082-T6 aluminum alloy plates using the GMAW welding process. To achieve these goals was implemented the Taguchi orthogonal array (L27) to define the design of numerical and experimental tests. All combinations were simulated in the Simufactwelding 6.0 software, from which it was possible to obtain the values of maximum residual stresses. The data treatment was carried out, reaching the combination of levels for each parameter. With ANOVA analysis was found that the parameter with the greatest influence in the residual stress generation was the welding speed, while the parameter with the least influence was the torch angle. Also, to minimize the residual stresses it was observed that the optimal combination of welding parameters is welding current intensity of 202 A, welding speed of 10 mm/s, and 30° of inclination of the angular torch. The two simulations that resulted in the highest and lowest residual stresses were validated experimentally by the hole drilling method to measure the residual stresses.
This work discusses challenges in conventional grinding wheels: heat-induced tool wear and workpiece thermal damage. While textured abrasive wheels improve heat dissipation, the current surface-only methods, such as those based on laser and machining, have high renewal costs. The proposed manufacturing technology introduces an innovative 3D cooling channel structure throughout the wheel, enabling various channel geometries for specific abrasive wheel applications. The production steps were designed to accommodate the conventional pressing and sintering phases. During pressing, a 3D organic structure was included in the green body. A drying cycle eliminated all present fluids, and a sintering one burnt away the structure, revealing channels in the final product. Key parameters, such as binder type/content and heating rate, were optimized for reproducibility and scalability. Wear tests showed a huge efficiency increase (>100%) in performance and durability compared of this system to conventional wheels. Hexagonal channel structures decreased the wear rates by 64%, displaying superior wear resistance. Comprehensive CFD simulations evaluated the coolant flow through the cooling channels. This new design methodology for three-dimensionally structured grinding wheels innovates the operation configuration by delivering the coolant directly where it is needed. It allows for increasing the overall efficiency by optimizing cooling, reducing tool wear, and enhancing manufacturing precision. This 3D channel structure eliminates the need for reconditioning, thus lowering the operation costs.
27 June 2022 in Soldering & Surface Mount Technology
Purpose: In a printed circuit board assembly (PCBA), the coefficient of thermal expansion (CTE) mismatch between the solder joint materials has a detrimental impact on reliability. The mechanical stresses caused by the thermal changes of the assembly lead to fatigue and sometimes the failure of the solder joints. The purpose of this study is to propose a novel pad design to obtain an interrupted solder/substrate interface, to improve the PCBA reliability. Design/methodology/approach: An interruption in the continuous intermetallic compound (IMC) layer of a solder joint was implemented, by the deposition of a silicone film in the pad, changing its geometry. That change allows a redistribution of stresses in the most ductile zone of the solder joint, the solder. The stress concentration at the solder/substrate interface is reduced, as well as the general state of stress at the solder joint. Findings: A new way was developed to reduce the stress on the solder joints, caused by thermal variations, because of the different components CTEs mismatch. This new method consists of interrupting the IMC layers of the solder joint, strategically, redirecting the usual stresses to a more ductile area of the joint, the solder. This is an innovative method that allows increase the lifetime of PCBAs and the equipments. Originality/value: In this study, a new pad design concept for higher solder joint reliability was developed to reduce the shear stress in the solder joints because of the CTE mismatch between all the solder joint components.