Assembly Of Parts Research Articles

Simulation of viscoelastic squeeze flows for adhesive joining applications

A backwards-tracking Lagrangian–Eulerian method is used to simulate planar viscoelastic squeeze flow. The momentum and continuity equations are discretized with the finite volume method and implicit immersed boundary conditions are used to describe objects in the domain. The viscoelastic squeeze flow, which involves moving solid geometry as well as free surface flow, is chosen for its relevance in industrial applications, such as adhesive parts assembly and hemming. The main objectives are to validate the numerical method for such flows and to outline the grid resolution dependence of important flow quantities. The main part of the study is performed with the Oldroyd-B model, for which the grid dependence is assessed over a wide range of Weissenberg numbers. An important conclusion is that the load exerted on the solids can be predicted with reasonable accuracy using a relatively coarse grid. Furthermore, the results are found to be in excellent agreement with theoretical predictions as well as in qualitative resemblance with numerical results from the literature. The effects of different viscoelastic properties are further investigated using the PTT model, revealing a strong influence of shear-thinning for moderate Weissenberg numbers. Finally, a reverse squeeze flow is simulated, highlighting important aspects in the context of adhesive joining applications. • Lagrangian–Eulerian used to simulate viscoelastic two-fluid flow. • Viscoelastic squeeze flow and extensional flow with applications for adhesive joining processes. • Viscoelastic flow with moving geometry treated with immersed boundaries and automatic adaptive grid generation. • Wide range of Weissenberg numbers for the Oldroyd-B model as well as the linear and exponential form PTT models.

Automatic Street Lighting Controller with Anti-Theft Alarm

In times when security is the topmost priority of every community, the provision of adequate and functional streetlights is deemed necessary as one of the measures to protect life and property. In this study, the researchers designed and constructed a prototype device Automatic Streetlight Controller with anti-theft alarm using a Light-dependent resistor (LDR) and Photodiode – Infrared LED tandem. This study was conducted to assess the qualitative description, functionality, and level of acceptability regarding the constructed Automatic Streetlight Controller with Anti-theft device in terms of its performance as to device and simulator/trainer, the convenience of use, safety, assembly of parts, and cost. A mixed research design was used that includes both qualitative and quantitative research design. The qualitative description of the device was presented in narrative form and assessed using a focused-group discussion. Quantitative research design is done using quasi-experimental in testing the functionality, trials were made to assess its functionality and descriptive survey method was used to assess the level of acceptability. Probability sampling was also used thru the lottery method to get the two (2) selected groups of respondents: the 3rd year BSIT- Electricity block B students and community barangay officials of Calunasan, Calape, Bohol. T-test was used to test its significance using the 0.05α. Results have shown that on testing the device has 100% good performance and is rated as it functions well. The acceptability level was rated “very high” which means highly acceptable by both respondents. Therefore, the device can be used if implanted in existing street lights or newly built ones to improve the condition of our street lights to properly illuminate the streets for an improved security system.

Regioselective approach to colchiceine tropolone ring functionalization at C(9) and C(10) yielding new anticancer hybrid derivatives containing heterocyclic structural motifs

The influence of base type, temperature, and solvent on regioselective C(9)/C(10) “click” modifications within the tropolone ring of colchiceine (2) is investigated. New ether derivatives of 2, bearing alkyne, azide, vinyl, or halide aryl groups enable assembly of the alkaloid part with heterocycles or important biomolecules such as saccharides, geldanamycin or AZT into hybrid scaffolds by dipolar cycloaddition (CuAAC) or Heck reaction. Compared to colchicine (1) or colchiceine (2), ether congeners, as e.g. 3e [IC50s( 3e) ∼ 0.9 nM], show improved or similar anticancer effects, whereby the bulkiness of the substituents and the substitution pattern of the tropolone proved to be essential. Biological studies reveal that expanding the ether arms by terminal basic heterocycles as quinoline or pyridine, decreases the toxicity in HDF cells at high anticancer potency (IC50s ∼ 1–2 nM). Docking of ether and hybrid derivatives into the colchicine pocket of αGTP/β tubulin dimers reveals a relationship between the favourable binding mode and the attractive anticancer potency.

A robot learning from demonstration framework for skillful small parts assembly

Increasing demand for higher production flexibility and smaller production batch size pushes the development of manufacturing industry towards robotic solutions with fast setup and reprogram capability. Aiming to facilitate assembly lines with robots, the learning from demonstration (LfD) paradigm has attracted attention. A robot LfD framework designed for skillful small parts assembly applications is developed, which takes position, orientation and wrench demonstration data into consideration. In view of constraints in industrial small parts assembly applications, two cascaded assembly polices are learned from separated assembly demonstration data to avoid potential under-fitting problem. With the proposed assembly policies, reference orientation and wrench trajectories are generated as well as coupled with the position data. Effectiveness of the proposed LfD framework is validated by a printed circuit board assembly experiment with a torque-controlled robot.

Improving the Quality of Small Pieces Made by Rapid Prototyping

Rapid Prototyping is the rapid fabrication of a part, model, or physical assembly that was designed using any design software (Autodesk Inventor Professional in this case), which is a CAD (Computer-Aided Design) application that helps in the creation of a digital prototype. The creation of the part, model, or assembly is usually completed using the manufacture of additives or more commonly known as 3D printing. The paper presents a 3D design, 3D printing, and verifying the actual dimensions of the printed „washer”. The purpose of this paper is to verify that printing errors are controllable and can be reduced. The paper contains and explains all the mandatory steps required to do this experiment and the laboratory equipment that was used to do this.

Identification of geometric errors of circular profiles at WEDM caused by the wire tool electrode vibrations and their reduction with support of acoustic emission method

High geometric precision of the machined surface after Wire Electrical Discharge Machining (WEDM) is in present one of the key quality parameters placed on machine parts manufactured for a wide range of industries. Despite the fact that WEDM belongs to the most precise finishing technologies, the deviations from the required geometric shape occur in the production of parts with rotary surfaces. These geometric deviations subsequently manifest in practice not only in the assembly of individual parts of the final product, but also in the operation. Another not the less important criterion considered at WEDM is the productivity of the WEDM process itself. WEDM productivity, in turn, is associated with the low overall productivity due to the need to apply multiple finishing cuts to achieve the desired quality of the machined surface in terms of geometric accuracy. Based on the already performed research, it is clear that the deviations of the geometric accuracy of the machined surface after WEDM are mainly caused by the vibrations of the wire tool electrode. Therefore, by eliminating these vibrations, it would be possible to achieve a substantial increase of the quality of the eroded surface, and thus reduce the number of finishing cuts. Ideally, the required quality level of the machined surface would be achieved right at the first cut. This would significantly increase productivity, enabling the WEDM technology to compete with other technologies in terms of productivity. In order to eliminate these undesirable vibrations of the wire tool electrode and to increase the quality of the machined surface after WEDM in terms of its geometric accuracy, the technical solution was proposed that applies the method of acoustic emission or laser beam vibration sensing in order to dynamically adjust the current values of technological parameters by the control system of the electroerosion machine. This way the given solution will increase the production accuracy of the circular holes, save the production time, increase the productivity, and ultimately bring the overall increase of the WEDM process economic efficiency.

Self-Strengthening, Self-Welding, Shape Memory, and Recyclable Polybutadiene-Based Material Driven by Dual-Dynamic Units.

A covalent adaptable network can endow rubber materials with recyclability and reprocessability and is expected to alleviate black pollution caused by end-of-life rubber. However, the loss of traditional vulcanization systems severely sacrifices their strength, and the tensile strength in the current study rarely exceeds 10 MPa unless fillers are added. In this work, we proposed a self-strengthening process based on dual-dynamic units (imine and disulfide), briefly, under heating, phenylsulfur radicals generated from aromatic disulfide bonds can react with double bonds (mostly vinyl) and/or couple with allyl sites, thus reforming a stronger cross-linked network. The neighboring imine unit is not affected and provides excellent thermal reprocessability and chemical recyclability. The result shows that the tensile strength can reach 19.27 MPa via self-strengthening without adding fillers or any other additives, and this ultra-high-strength is much higher than those of all known recyclable polybutadiene-based rubber materials. In addition, the material also has malleability, shape memory, and self-welding properties. By doping carbon nanotubes, a recyclable conductive composite can also be achieved. In general, we envision that this enhanced strategy has great potential to be generalized for all elastomers containing double bonds (such as styrene-butadiene rubber, nitrile rubber, isoprene rubber, and their derivatives). The reprocessability and self-welding are practical for on-site assembly or repair of composite parts and extend the service life of materials.

A modeling method of complex assembly based on digital twin

Assembly quality as a key indicator of the performance of complex products requires the development of a predictive product model that integrates part and process information. Furthermore, deriving a high-quality assembly model is important for accurate assembly modeling and simulation. At present, assembly modeling mainly considers the geometric errors of the parts induced by manufacturing processes, and ignores a number of parameters in the real environment, which leads to inconsistencies when assembling the parts, and difficulties in meeting the performance requirements of high-precision products. Therefore, to further improve the accuracy of assembly simulation, digital technologies are extensively used to reproduce the assembly process of complex products digitally and guide the actual production and assembly of parts. In this paper, by collecting and processing real data of complex products, a hierarchical model of a complex assembly including geometric shape, position constraint and physical state is constructed, and the corresponding reverse engineering model is built. Digital twins are thereafter constructed and mapped to the real parts. Based on this, real-time data of the resource layer, the process layer and the environment layer in the assembly process are integrated, and a digital representation of complex assembly is proposed. A case study of a bearing seat highlights the applicability of the proposed approach. The data collected from the scanned bearing seat integrates the constraint information of the assembly features and the bearing seat's physical information to construct a digital twin of the bearing seat.

Assembly of countersunk-hole parts based on 3D pose estimation and impedance control

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Based on the Influence of Standard parts Installation and Surface Quality on Aircraft Assembly

In the process of aircraft assembly, various parts have an important impact on the aircraft assembly, among which the fasteners play an important role in the aircraft assembly, affecting the stability of the aircraft assembly and the service life of the aircraft. Standardized fastener installation and surface quality affect the aircraft assembly quality. Proper fastener installation and guaranteed quality are conducive to reducing the risk of aircraft assembly. However, the characteristics of standard fasteners in aircraft assembly need to be studied urgently. This paper analyzes the assembly characteristics of aircraft standard parts, the information and constraints of standard parts, discusses the assembly information of standard parts, and explores the types and installation requirements of fasteners, hoping to improve the assembly effect of standard parts in aircraft assembly.

The SSU Processome Component Utp25p is a Pseudohelicase.

RNA helicases are involved in nearly all aspects of RNA metabolism and factor prominently in ribosome assembly. The SSU processome includes 10 helicases and many helicase-cofactors. Together, they mediate the structural rearrangements that occur as part of ribosomal SSU assembly. During the identification of the SSU processome component Utp25/Def, it was noticed that the protein displays some sequence similarity to DEAD-box RNA helicases and is essential for growth. Interestingly, mutational ablation showed that Utp25’s DEAD-box motifs are dispensable. Here, we show that the Utp25 AlphaFold prediction displays considerable structural similarity to DEAD-box helicases and is the first fully validated pseudohelicase.

Advances in powder bed based Additive Manufacturing of metal-glass-hybrid-components

As powder bed based additive manufacturing (AM) is gaining more traction in the research and industry, significant efforts are made to expand the capability of AM in combining different materials. Conventionally, multiple materials, sealants and processes are necessary in order to join metal and glasses in assemblies. The development of a single-step process for vacuum-tight and strong bonding between glass and metal could drastically reduce the part count and assembly cost.This paper investigates the feasibility of joining the iron-nickel-cobalt alloy Kovar with borosilicate glass. The powder bed fusion by laser beam is used to melt Kovar structures directly onto glass substrates. Suitable process parameter for an iron-silicon-oxide material-bonding layer of 3 µm thickness were developed using design of experiments. With an energy input of 333 J/mm³ for the initial layer and 60 J/mm³ for the bulk structure, tensile testing of the metal-glass-connection revealed bonding forces up to 0.5 MPa.

Influence of task time variation in adopting Walking Worker assembly systems: a design approach

Unlike traditional Fixed Worker (FW) assembly systems, in which an operator remains in the same workstation performing repetitive tasks, in the Walking Worker (WW) ones the operators travel along the line stations to produce the finished product. Interestingly, such a configuration enables to achieve a greater level of production volume flexibility, without changing the assembly system layout, parts disposition, and tools assignment. The basic requirement of a WW is to be cross-trained and able to fully assemble the product from beginning to end. The WW travel activity, which increases when the number of stations increases, negatively impacts on the system performance. On the other hand, the possibility to have extra-stations, i.e., a greater number of stations compared with the number of operators, makes the WW system able to dynamically balance the work overload differences between the operators.The aim of this paper is to investigate the effect of stations time variability, typical for example of mixed model assembly lines, on the system productivity, comparing the performance of a WW system and a FW one. A simulative study has been developed, considering as variables the task time coefficient of variation, the travel time, the number of stations, and the number of operators, to analyze when and how the WW system can outperform the FW one. The results show an assembly system design approach that defines the better system to adopt (WW or FW), the number of operators and the number of extra-stations to include, as a function of the considered target productivity and task time variation.

A case study on the integration of assembly line balancing and feeding decisions

Mass-customization of products imposes new challenges on the planning of assembly lines due to an increased number of product models and a large variety of parts. Traditionally, both academics and practitioners approached the planning of an assembly line by balancing the assembly line, i.e., assigning tasks to stations, and decided on line feeding policies based on this outcome. However, this approach neglects the reciprocal effects between the two decision-making outcomes, i.e., the impact of line feeding decisions on task times and the impact of balancing decisions on feeding requirements and constraints. This interaction is of peculiar interest for assembly lines in a mass-customization environment due to the large number of assembly tasks and parts. Therefore, this study describes a framework that simultaneously optimizes both problems and minimizes overall costs. We show preliminary results using real-world data from a large automotive company.

Количественная оценка неопределенности случайного рассеивания среднего зазора и натяга в сопряжениях

Actual dimensions of suitable parts made according to the same drawings can fluctuate between the given limit dimensions, and the clearances and interferences in the conjugations — depending on the random scattering of the actual dimensions with the deviation of the shape of the real surface or profile. The error of the shape of the real surface affects the probabilistic estimate of the results of sorting parts, leads to uncertainty in the size of the maximum of the material, a random scattering of the average clearance and interference in the mating and, as a consequence — the uncertainty to use all that come in for assembly of parts. The main result of the study is related with ensuring the receipt for the assembly of an equal number of parts, to the conclusion possessing novelty of the analytical dependences of finding a quantitative estimate of the uncertainty of the random scattering of the average clearance and interference in the mating, the random scattering of the average size relative to the upper and lower acceptance boundaries. Using the assembly method proposed with the initial reduction of real clearances and interferences in the mating by means of narrowing the tolerances of the actual dimensions to the tolerance of the shape of real surfaces in diametric terms within the random dispersion of the average size relative to the upper and lower acceptance boundaries allows to ensure the receipt on the assembly of an equal number of parts is achieved, including in the tested batches of parts with a breakdown of the tolerances of the actual dimensions into an equal number of dimensional groups.

Time-dependent springback of high strength titanium tubular materials: Experiment and modeling

• Residual stress and dislocation evolution of HSTT during bending and springback comprehensively obtained. • Compression-tension uneven axial residual stress-driven creep mechanism of time-dependent springback for HSTT revealed. • Viscoelasticity-Kelvin constitutive model considering stress attenuation developed for modeling time-dependent springback. • Combining Viscoelasticity-Kelvin with SIM and Chord modulus models for accurate prediction of time-dependent springback. • Deformation-history dependent effects of time-dependent springback for spatial multi-bending tubes clarified. Although time-dependent springback is minor compared with instantaneous springback, its deformation-history dependent effects may deteriorates the compactness of parts assembly and poses potential hazards to the safety and stability of the equipment systems especially under harsh service conditions. However, time-dependent springback still has not been paid enough attention, and how to accurately predict this phenomenon is still a challenge needed to be solved urgently. In this work, taking high-strength Ti-3Al-2.5V titanium tubular materials (HSTT) upon bending as a case, the experimental exploration of the physical mechanisms and the prediction modeling for time-dependent springback of the HSTT were conducted. First, the residual stress and dislocation evolution of HSTT during bending, instantaneous springback and time-dependent springback are comprehensively experimentally obtained, and the compression-tension uneven residual stress-driven creep deformation mechanism of time-dependent springback for HSTT was revealed. Then, considering stress attenuation, a Viscoelastic-Kelvin constitutive model for time-dependent springback was developed and combined with the stress invariant-based model (SIM) and Chord modulus model to accurately predict the whole process of bending, instantaneous springback and time-dependent springback of the HSTT. Finally, the verified model is employed to explore the evolution rules of time-dependent springback and residual stress of HSTT upon bending, and the deformation-history dependent effects of time-dependent springback for spatial multi-bending component are clarified. The findings and methods of this study could aid in achieving higher precision manufacturing of high performance tubular components.

Development of work design method considering work difficulty and analysis system in parts assembly works

Development of work design method considering work difficulty and analysis system in parts assembly works

AI-enhanced vision system for dispensing process monitoring and quality control in manufacturing of large parts

Assembly is one of the cornerstones of today’s manufacturing; thus, efficient automated assembly systems have become a necessity in the recent past. Challenges that have traditionally been present in such systems involve positioning accuracy, stable gripping, accommodation of several variants by the same resources and prevention of error aggregation. In robot-based applications the detection of parts and their components is a common task, but when it comes to large objects which cannot be portrayed in single camera frames, the complexity becomes significantly larger. This paper presents an AI based perception system which employs a 3D vision sensor to implement a smart dispensing application and perform online process quality control of large parts assembly. The aim of the system is to provide execution autonomy for a robotic manipulator that is responsible for glue dispensing on different types of aluminium profiles of varying cross-sections, length, and associated glue patterns. By using an eye-in-hand RGB-D camera and employing deep learning methods (Yolov3 algorithm), the framework recognizes the type of profile that is going to be processed, and depth information is used to extract the profile’s points (starting-ending points) on which glue must be dispensed. Point Cloud manipulation (DBSCAN clustering, plane segmentation) and 2D image-based processing were tested during the quality inspection, in order to validate the success and accuracy of the process (detection of glue discontinuities, calculation of the glue volume level). The system has been deployed on a case study involving the assembly of components on buses and the results indicate that a robust recognition and adhesive application can be obtained throughout each operation cycle.

Optimization of process variables in drilling of LM6/fly ash composites using Grey-Taguchi method

Drilling is a critical step in the hole-making operation. It is quite beneficial for part assembly. Hard particulatesintroduced into the continuous phaseof thecomposite materials, makes them hard to process. As a result, optimizing the drilling variables is inevitable . The primary goal of this study is to manufacture LM6/Fly Ash with weight percentages of fly ash 3, 6 and 9 adopting the stir casting technique. The second objective is to use Taguchi's Design of Experiments (L27 OA) to drill composite materials using feed rate (F), spindle speed (S), drill material (D), and % of reinforcement (R) as drillingprocess variables at 3 levels. The ultimate goal is to optimize the drilling process variables for obtaining minimumthrust force (TF), surface roughness (SR)and burr height (BH) using multi-objective Grey Relational Analysis. The optimum process variable achieved is F1S3D3R3, i.e., 50 mm/min, 3000 rpm, TiN-coated drill bit and 9 wt% of fly ash.

Low Thermal Conductivity Adhesive as a Key Enabler for Compact, Low-Cost Packaging for Metal-Oxide Gas Sensors

Metal-oxide (MOX) gas sensors commonly rely on custom packaging solution. With an ever-increasing demand for MOX gas sensors, there is a clear need for a low cost, compact and high-performance package. During normal operation, MOX sensors are heated up to a temperature in the typical range of 200-300°C. However, the generated heat must not damage or degrade any other part of the assembly. Using 3D finite elements modelling, we developed an optimal package configuration. To thermally insulate the assembly from the heated MOX sensor we have developed in-house a low thermal conductivity xerogel-epoxy composite with 22.7% by weight xerogel and a thermal conductivity of 107.9 mW m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> K <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> which is a reduction exceeding 30% compared to commercially available epoxy. Based on the low thermal conductivity xerogel-epoxy composite, we have developed a novel packaging approach that can suit the large family of MOX sensors. The developed alternative packaging solution includes a small number of assembly steps and uses standard processes and techniques. The assembled MOX sensor is low cost and has a low power consumption, while all thermally sensitive assembly parts remain at low temperature during the system’s lifetime.