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Abstract: This study applied a holistic approach to the problem of controlling the temperature of critical areas of tools using conformal cooling. The entire injection molding process is evaluated at the tool design stage using four criteria, one from each stage of the process cycle, to produce a tool with effective cooling that enables short cycle times and ensures good product quality. Tool manufacturing time and cost, as well as tool life, are considered in the optimization by introducing a novel tool-efficiency index. The multi-objective optimization is based on numerical simulations. The simulation results show that conformal cooling effectively cools the critical area of the tool and provides the shortest cycle times and the lowest warpage, but this comes with a trade-off in the tool-efficiency index. By using the tool-efficiency index with non-dominated sorting, the number of relevant simulation cases could be reduced to six, which greatly simplifies the decision regarding the choice of cooling system and process parameters. Based on the study, a tool with conformal cooling channels was made, and a coolant inlet temperature of 20 °C and a flow rate of 5 L/min for conformal and 7.5–9.5 L/min for conventional cooling channels were selected for production. The simulation results were validated by experimental measurements.
Keywords: conformal cooling, injection molding, tooling, additive manufacturing, numerical simulation, non-dominated sorting
Published in DKUM: 05.12.2024; Views: 0; Downloads: 1
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Abstract: This doctoral thesis focuses on the development of Space Vector Modulation (SVM) techniques adjusted for single-shunt current measurement and applied to the three-level three-phase voltage source inverter. Based on the single-shunt current measurement, three-phase load currents are then reconstructed. An overview of existing multilevel topologies and their main operating principles is provided within the thesis. To evaluate proposed SVM techniques adjusted for single-shunt current measurement, a three-level three-phase diode clamped voltage source inverter topology is selected. The main advantages of the selected topology are high efficiency, reduced semiconductor stress, the low capacitance of DC-link capacitors, etc. To reconstruct the three-phase load currents, a single-shunt is positioned inside the middle branch of the DC-link. An overview of existing modulation techniques for two-level and multilevel inverters is provided within the thesis. To reconstruct three-phase load currents, three SVM methods are proposed within the thesis. Due to the lack of a current measurement window, while the voltage vector is positioned near sector or region boundary areas, additional modifications are required. The first SVM method shifts the SVM signals to ensure the minimum current measurement window needed for measurement with minimum additional vector injection. Such an approach ensures the high modulation index values greater than 0.8 with the smallest current ripple due to the SVM signal symmetry. The second method intentionally injects the colinear voltage vector into the existing vector combination to ensure the minimum time window required for current measurement. As a drawback, a smaller modulation index compared to the first method can be achieved. As an advantage, a very low modulation index of less than 0.2 can be achieved. The third method simplifies the second method by using a single SVM pattern. Such a method can be used only for very low modulation indexes and can be applied for two-level and three-level inverters. The proposed SVM methods are implemented within the Digital Signal Processor (DSP). Experimental results confirm the proper operation of the proposed methods applied to the three-level diode clamped voltage source inverter.
Keywords: single-shunt, three-level inverter, SVM modification, current reconstruction, vector injection
Published in DKUM: 09.03.2023; Views: 396; Downloads: 57
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Abstract: The objective of the master thesis is to determine the filling properties of injection moulding process for newly created material, and to understand how the variation of processing parameters affects the flow possibilities. In thesis two materials were analysed, i.e. neat PLA material, which was used as a benchmark material and newly created composite CitrusPLA that is based on biodegradable PLA matrix and reinforced with citrus fibres. To fulfil the aim, the virtual and experimental design of experiment with the Taguchi methodology was conducted with use of spiral flow test, where the flow length of material through mould cavity was observed. The experimental results were the basis for the accuracy validation of numerical results and also to determine the optimum process parameters for injection moulding products with best flow conditions through statistical evaluation. It has been concluded that the newly created composite has lower viscosity compared to benchmark virgin PLA which results in better flow conditions in spiral flow test analysis. Both materials have the same optimal conditions in terms of flow conditions. The contribution of mould temperature is in both cases negligible. However, other two variated parameters i.e. melt temperature and injection speed have higher influence on filling characteristics for both materials.
Keywords: injection moulding optimization, material characterization, Moldflow, injection moulding simulations, Taguchi DOE, bio-composites, citrus waste fibres, PLA
Published in DKUM: 07.06.2019; Views: 1665; Downloads: 37
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Abstract: Izhodišče: Pri življenjsko ogroženih bolnikih je eden izmed najnujnejših ukrepov takojšnja vzpostavitev intravenozne poti, kadar pa ti ni mogoče je smiselno uporabiti intraosalni pristop. Namen diplomskega dela je predstaviti intraosalni pristop in možnosti apliciranja medikamentozne terapije po intraosalni poti. Raziskali smo v katerem primeru je priporočljivo uporabiti intraosalni pristop pri poškodovancu ter v kakšni meri se intraosalni pristop uporablja v praksi. Raziskovalne metode: Uporabili smo kvantitativno metodologijo in deskriptivno metodo dela. Podatke smo zbrali s pomočjo anonimne ankete, kot instrument raziskovanja smo uporabili anketni vprašalnik. Rezultati: Ugotovili smo, da je intraosalno pot uporabilo približno polovico vseh anketirancev (48 %). Najbolj poznana pripomočka za vzpostavitev intraosalne poti sta B.I.G. in EZ/IO. Po analizi rezultatov lahko ugotovimo, da anketiranci vedo, da lahko po intraosalni poti apliciramo zdravila, infuzije ter krvne pripravke. Diskusija in zaključek: Z ugotovitvami želimo izpostaviti, da je poznavanje intraosalnega pristopa na dobri poti, čeprav je potrebno najprej podkrepiti teoretično znanje, da bomo lahko v praksi dosegali pričakovane standarde. Potrebno je poudariti, da bi morali delodajalci zagotoviti več internih izobraževanj, kjer bi bil večji poudarek na alternativnih venskih pristopih in bi lahko zaposleni dobili teoretično in praktično znanje.
Keywords: intraosalni pristop, prehospitalno okolje, reševalci, terapija, bone injection gun, EZ/IO.
Published in DKUM: 19.07.2017; Views: 2453; Downloads: 353
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Abstract: Potentiometric determination of penicillamine (pen) is described based on a batch experiment and flow-injection analysis (FIA) using a chemical sensor with AgI-based membrane. The membrane was prepared by pressing silver salts (AgI, Ag2S) and powdered Teflon. This membrane was incorporated in a multipurpose electrode body for batch measurements, and in a tabular flow-through sensor body for FIA measurements. For batch measurements, the equilibrium potentials recorded with continuous addition of standard penicillamine solution were considered in relation to ▫$lg(c_pen/mol L^-1)$▫. Linear response with slope of 60 mV was obtained in the concentration range from 2.5 x ▫$10^5$▫ mol ▫$L^1$▫ to 1.8 x ▫$10^-2$▫mol ▫$L-1$▫. In using the tubular sensor with a membrane of the same coposition for FIA measurements, the linear response with slope of 59 mV was recorded in the concentration range from 1 x ▫$10^4$▫ mol ▫$L^1$▫ to 1 x ▫$10^-1$▫ mol ▫$L^-1$▫. The response of the applied chemical sensor to penicillamine (designated also as RSH) is explained by the formation of sparingly soluble RSAg in the reaction solution and/or the exposed surface of the sensor. The solubility product ▫$K_s(RSAg)$▫ was determined using experimental values recorded both by batch measurements and by the continuous-flow experiment. The mean value obtained by different measurements and using a membrane of the same composition is ▫$K_s(RSAg)$▫ = (1.4+-0.1) x ▫$10^-20$▫ mol ▫$L-2$▫).
Keywords: analytical chemistry, batch potentiometry, flow-injection analysis, membrane electrode, tubular sensors, penicillamine
Published in DKUM: 05.07.2017; Views: 1316; Downloads: 90
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