This paper presents a novel optimization technique in straight-build assembly to control variation propagation. The optimization technique is developed by minimizing the eccentricity stage by stage in the assembly. The straight-build assembly model is derived from connective assembly models, easily expressing the part-to-part relationships. Any measurement error or process error in the assembly can be easily incorporated in the model. This approach can be also used to predict the final assembly quality while the design is still at the conceptual stage. The straight-build assembly is validated by using statistical analysis through two case studies: a simple identical cylindrical-component assembly and a practical non-identical cylindrical-component assembly. The variation propagation can be reduced significantly for the straight-build assembly, compared to the direct-build assembly without optimization. The results show how the variation propagation control is related to process noise and measurement accuracy. The simulation results also show that minimal variation can be achieved at reduced cost by properly selecting the accuracy of measurement, according to process procedures. The information obtained provides a practical and useful approach for design engineers. The potential applications of the straight-build assembly are also illustrated.
For a.ssembly of rotating machines, such as machining tools, industrial turbomachinery, or aircraft gas turbine engines, parts need to be assembled in order to avoid internal bending of the geometric axis of the rotor to meet functional and vibration requirements. Straight-build assembly optimization is a way of joining parts together in order to have a straight line between the centers of the components. Straight-build assembly is achieved by minimizing eccentricity error stage-by-stage in the assembly. To achieve minimal eccentricity, this paper proposes three assembly procedures: (i) table-axis-build assembly by minimizing the distances from the centers of components to table axis: (ii) minimization of the position error between actual and nominal centers of the component: and (iii) central-a.xi.s-buitd assembly by minimizing the distances from the centers of components to a central axis. To test the assembly procedures, two typical assembly examples are considered using four identical rectangular components and four nonidentical rectangular components, respectively. Monte Carlo simulations are used to analyze the tolerance build-up, based on normally distributed random variables. The results show that assembly variations can be reduced significantly by selecting best relative orientation between mating parts. The results also show that procedures (i) and (ii)have the most potential to minimize the error build-up in the straight build of an assembly. For the.se procedures, the variation is reduced by 45% and 40% for identical and nonidentical components, re.spectively, compared to direct-build assembly. Procedure (iii) provides better performance than direct-build assembly for identical components assembly, while it gives smaller variation at the first tv,o stages and larger variation at the third stage for nonidentical components assembly. This procedure could be used in an assembly with limited stages.
Plastic bottles are generally recycled by remolding them into numerous products. In this study, waste from plastic bottles was used to fabricate recycled polyethylene terephthalate (r-PET) nanofibers via the electrospinning technique, and high-performance conductive polyethylene terephthalate nanofibers (r-PET nanofibers) were prepared followed by copper deposition using the electroless deposition (ELD) method. Firstly, the electrospun r-PET nanofibers were chemically modified with silane molecules and polymerized with 2-(methacryloyloxy) ethyl trimethylammonium chloride (METAC) solution. Finally, the copper deposition was achieved on the surface of chemically modified r-PET nanofibers by simple chemical/ion attraction. The water contact angle of r-PET nanofibers, chemically modified r-PET nanofibers, and copper deposited nanofibers were 140o, 80o, and 138o, respectively. The r-PET nanofibers retained their fibrous morphology after copper deposition, and EDX results confirmed the presence of copper on the surface of r-PET nanofibers. XPS was performed to analyze chemical changes before and after copper deposition on r-PET nanofibers. The successful deposition of copper one r-PET nanofibers showed an excellent electrical resistance of 0.1 ohms/cm and good mechanical strength according to ASTM D-638.
In this article, the assembly of axi-symmetric rigid structures from imprecisely manufactured components is considered to produce a 'straight-build' assembly. The eccentricity of the assembly is improved by selecting the best relative orientation of each component and using four different strategies to control the assembly errors. The presentation is simplified by considering the assembly of two-dimensional structures, and the Monte Carlo simulation technique is used to quantify the propagation of random component variations on the resulting assembly. The axial and radial run-outs for each component are used to represent component variability and these quantities are represented as Gaussian random variables. The influence of component variations on the assembly is predicted using connective assembly models. Numerical results are presented for assemblies consisting of: (a) identical rectangular components; and (b) non-identical rectangular components. The results are compared with each other and those obtained using 'direct-build' assembly, which does not control the assembly errors. It is found that assembly variations can be reduced significantly using the proposed techniques.
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