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Nowadays, with the increasing demands for quality and precision in microelectronic packaging, the study and prediction of droplet parameters before packaging have become increasingly important. This paper aims to derive a predictive formula for droplet volume dispensing to improve packaging quality, optimize process parameters, reduce resource waste, enhance process control, and enhance product quality and reliability. Based on the needle transfer method for ultra-microdroplet dispensing, a droplet dispensing device that meets packaging requirements is established, and precise control of droplet volume is achieved by changing the factors that affect droplet formation. The droplets obtained from experiments are analyzed using pixel extraction, and a numerical fitting method is employed to establish a droplet volume model. It is found that the pixel method is a practical approach for determining droplet volume, with an average deviation of approximately 1.85%. By conducting droplet dispensing experiments with varying initial distances, the smallest droplet volume achieved is 24.33 pL, and it is concluded that larger initial distances result in smaller droplet volumes and reduced droplet contact area. Based on the droplet dispensing experimental data obtained by varying the initial distance, mathematical predictive models for droplet volume and droplet contact area are derived. The results show that the average difference rate between predicted and actual volumes is 0.51%, and the average difference rate between predicted and actual contact areas is 0.56%. [ABSTRACT FROM AUTHOR]

Electromagnetic clinching (EMC) is a high-speed connection technology that combines electromagnetic forming and mechanical clinching. The die structure significantly affects the mechanical properties of the joint. In this paper, an optimal method based on response surface methodology (RSM) and particle swarm optimization algorithm (PSO) is proposed to improve the mechanical properties of joints clinched by EMC. The mathematical models of die geometrical parameters and cross-sectional parameters of the joint are obtained by RSM and numerical simulation. Then, the die structure is optimized through PSO. Finally, the experiments are carried out using the optimized and standardized die. The results show small errors between the simulation and the experiment. The joint strength using a standardized die is 878 N, and energy absorption is 0.758 J. The joint strength using the optimized die is 1322 N, and energy absorption is 1.335 J. Compared with the standardized die, the joint strength and energy absorption of parts obtained by the optimized die are increased by 50.5% and 76.1%, respectively. [ABSTRACT FROM AUTHOR]

The whirl-machining process is a precise, efficient, and promising machine process for manufacturing workpieces over the milling process. At the same time, the roller-gear cam has advantages over the other cam-follower system. However, the whirl-machining process has not been applied to manufacture the roller-gear cam. Therefore, this paper proposes a novel method for roller-gear cam manufacturing using a whirl-machining process. Mathematical modeling is described for generating the roller-gear cam, roller, and whirl-milling tool surface. A novel CNC machine and its coordinate system are proposed. Cutting simulations for obtaining the surface topologies and normal deviations are conducted. Globoidal cam with different cylindrical rollers, globoidal cam with a conical roller, and cylindrical cam with a conical roller are taken as case studies, and results are discussed. A virtual cutting simulation was conducted using VERICUT. Some machining examples are shown to verify the benefits of the proposed method in roller-gear cam manufacturing. [ABSTRACT FROM AUTHOR]

Due to gravity, a change in the welding position will significantly affect the flow of the molten pool, thus affecting the weld bead shape. An all-position welding process of low-power pulsed laser-MAG (metal active gas) hybrid welding was proposed to improve the welding efficiency and quality of all-position welding. This paper used the response surface method (RSM) to develop the weld bead geometry mathematical model. The analysis of variance confirmed the significance and accuracy of the model. The results show that the models can accurately predict the weld geometry, percentage errors for any models are less than 8.1%. Then, the effects of welding parameters and welding position on weld width, weld reinforcement, and weld penetration were analyzed. Finally, the optimal welding parameters at five positions of 0°, 45°, 90°, 135°, and 180° were obtained by numerical optimization with RSM. The study results can provide a reference for applying laser-MAG hybrid welding in all-position welding. [ABSTRACT FROM AUTHOR]

Ultrasonic power plays an important role in ultrasonic surface rolling, and the maximum contact stress and springback generated by ultrasonic power during ultrasonic rolling also affect the surface quality of mechanical materials. In order to study the effect of different ultrasonic powers on the maximum contact stress and springback during the ultrasonic rolling process, in this paper, based on the elastic–plastic theory, a mathematical model for predicting the maximum contact stress and springback is proposed. In order to verify the mathematical model, the ultrasonic surface rolling experiment was carried out with 20 steel as the experimental sample. Through the analytical derivation of the mathematical model, and study other characteristic parameters of the model, such as rolling depth, Mises. And the ultrasonic surface rolling process is simulated numerically by ABAQUS. The results show that the mathematical model can effectively predict the maximum contact stress, rolling depth, Mises, and springback, and the average deviation is 10%. With the increase of ultrasonic power, Mises, pressure, and springback gradually decrease, and the rolling depth increases. [ABSTRACT FROM AUTHOR]

This paper proposes a topology modification method of generating gear grinding based on multi-axis linkage parameter optimization. In order to improve the accuracy of tooth flank modification in generating gear grinding and to reduce the transmission error of modified gear pair, a multi-objective optimization genetic algorithm is adopted to adjust machine movement. Firstly, according to the position and motion relationship among diamond wheel, worm wheel, and workpiece gear, the mathematical models of worm wheel dressing and generating gear grinding are established. The linkage relationships between motion axes are redefined to achieve topology modification. The radial feed F X 1 , tangential feed F Y 1 of worm wheel, and gear rotational angle φ g are defined as the fourth-order polynomial function of axial feed F Z 1 . Secondly, the transmission error model of modified gear is developed. And the polynomial coefficients of each axis are optimized with the objective of minimizing total tooth flank deviation and transmission error. Finally, the effectiveness of this method is verified by three numerical examples with different parameter groups. In addition, the diamond wheel and worm wheel used in the study are standard profile, which saves the cost of gear machining and improves the efficiency of production cycle. The research results could provide a theoretical reference for the improvement of generating gear grinding process. [ABSTRACT FROM AUTHOR]

Currently, the quality check of bike frame still heavily relies on human operation. In practice, an entire checking process usually takes more than 30 min to complete. To overcome this dilemma, this paper aims to develop a fast high-precision measurement system using robotic arm based on 3D geometry mathematical model. Instead of four points needed to find coefficients of a space sphere, only three investigation points are required to achieve the sphere axis coordinates for measurement. The personal computer (PC) works as a control core, which to perform the mathematical model and control robotic arm movement. The robotic arm combined with contact sensor (probe) is used to move to the desired inspection points in shaft length, internal diameter, verticality, and parallelism following up the designated path planning route. The experimental results confirm that the proposed system can accurately reach the measurement outcomes. The entire checking cycle can be completed in 3 min at the range of 0.15 mm error, effectively reducing the process time with a high precision. [ABSTRACT FROM AUTHOR]

With the rapid development of precision micro-manufacturing technology, the connection and assembly processes of precision micro-devices have placed higher demands on the volume and precision of micro-dispensing technology. In the dispensing process, the adhesive dispensing volume is crucial to the bonding quality. In this paper, based on the analysis of the composition of critical contact force and the mechanism of action, a method was proposed to control the ultra-micro-adhesive dispensing volume at pL level. Firstly, a mathematical model describing the change of droplet size and critical contact force during the extrusion of adhesive was established, which provided a theoretical basis for analyzing the mapping relationship between contact force and adhesive dispensing volume. Then, the mathematical models describing the droplet initial volume, dispensing volume, and transfer ratio were derived. Based on this, a mechanism and method to control the volume of dispensing to the substrate by contact force control to trigger the liquid bridge pull-off action was developed. The critical contact force was detected in real time to determine the changing state of the process of adhesive contacting the substrate, and used as the basis for triggering the stretching stage of the liquid bridge, and then achieved the prediction and control of the adhesive dispensing volume. In this paper, a series of experimental studies were conducted on the method of controlling the adhesive dispensing volume through contact force by embedding a micro-force sensor with high resolution into the dispensing system. The experiments were conducted with the critical contact force in the range of 0.5–4.5 mN. The results showed that the increase of the critical contact force was approximately linear with the increase of the adhesive dispensing volume. The deviation rate of the dispensing volume under the same critical contact force was less than 1.7%, and the average deviation rate of the overall adhesive dispensing volume was about 0.6%, so it was basically possible to precisely control the adhesive dispensing volume at the pL level by changing the contact force. This study revealed the composition and variation mechanism of contact force, and the proposed method for controlling the adhesive dispensing volume have significant value and potential in the micro-assembly of viscous ultra-microfluids and other applications. [ABSTRACT FROM AUTHOR]

This paper aims to study tasks' allocation problem in a single-station collaborative robot assembly system 4.0. Two products with identical demands are run in a system simultaneously in mixed mode to reduce the idle time and improve the system utilization. The idle time occurs due to balancing difficulties and particularly in this case restrictions in the task vs. robot-worker feasibility matrix. It is not allowed for the resources to assemble a same product simultaneously to avoid any direct contact between resources. Thus, the products are swapped between resources as needed to complete the assembly tasks. Two approaches, a novel mathematical model and the shortest processing time (SPT) rule, are propounded in this study to reduce the cycle and idle times and enhance the production rate of an assembly system. The two proposed methods rely on dividing the timeline of a station into unknown stages with unknown lengths. The performance of the proposed mathematical model and SPT rule are evaluated by two performance measures: the total number of stations and the % average station utilization. The obtained results are compared to the results of the modified COMSOAL heuristic. The findings revealed that the novel mathematical model dominated results. It guaranteed minimizing the cycle time and maximizing the production rate compared to the SPT rule and modified COMSOAL heuristic. However, many companies value a 1-s reduction in cycle time as valuable. This directly relates to the reduction of direct resources costs and the total number of stations. [ABSTRACT FROM AUTHOR]

The die undergoing severe loads induces inevitable wear in the pressure forming process, and the wear of die arouses obsessions about the die's service lifetime. In order to predict the wear and lifetime for a pair of rollers in net-shape blade rolling process, this paper quantified the distributions and evolutions of the local wear over roller cavities based on the local contact load responses and predicted the lifetime which related to wear by a mathematical model. Firstly, the net-shape blade rolling process and the local contact load responses were summarized. Then, an improved wear model was provided based on the Archard formula, and the impact factors of the model were standardized by a regression analysis experiment. The transient wear distributions and evolutions over the roller cavities were enumerated, and the wear distribution for one rolling cycle was calculated based on wear accumulation effect. Finally, a lifetime prediction model was proposed to predict the service lifetime of the rollers according to the wear accumulation effect, and an experimental verification was carried out to validate the model. The results show that the wear model and lifetime prediction model can be used for investigating the wear and lifetime of the roller cavities for the net-shape blade rolling process. [ABSTRACT FROM AUTHOR]