Development of a quality management framework for powder-based additive manufacturing systems

Date
2023-12
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Stellenbosch : Stellenbosch University
Abstract
ENGLISH ABSTRACT: With the rise of the fourth industrial revolution, powder-bed-based Additive Manufacturing (AM) technologies have been rising alongside conventional manufacturing technologies in regulated industries such as aerospace and medicine. In recent years, the global drive has been to guarantee the quality of parts manufactured using these AM technologies to the same level as conventional technologies. While a significant portion of research was conducted on verifying part quality as part of the postprocessing process, this can usually only be done using non-destructive testing (NDT) methods. However, these processes are often expensive and time-consuming; thus, a requirement was identified for the in-situ monitoring of the part manufacturing process. There have been several studies that have attempted to address this requirement. Still, most of these studies have only focused on detecting defects that may occur during the build process and, in some cases, the classification of defects according to the defect type. The aim of this study was focused on developing a monitoring system that can be used to monitor the quality of the powder bed surface and, in the future, provide closed-loop feedback to the machine control system about the state of the powder bed surface. For the development of such a closed-loop feedback system, it is necessary to classify defects based on their type, severity, and position on the powder bed surface. This type of closed-loop feedback system is not yet implementable due to the proprietary nature of the machine control systems and manufacturer hesitance toward un-validated autonomous feedback systems. However, it is envisioned that with the correct frameworks in place, this may soon become a reality. Based upon these requirements, the first half of this study was primarily focused on developing a framework that can be used to classify defects according to the defect's type, severity, and position on the powder bed surface. The study also focused on how the framework could possibly be used in the future to implement an autonomous closed-loop feedback system that can apply corrective actions to the defects on the powder bed surface. The second half of this study was focused on the physical development of a monitoring system that could be used to monitor the powder bed surface. This monitoring system had the capability to autonomously detect and classify the defects present on the powder bed and then further process these defects according to the developed framework. This physical implementation of the monitoring system was then used to process images that were captured of real-world build jobs. The results recorded using this monitoring system were then evaluated, and it was proven that the proposed framework could be used to successfully classify these powder bed surface defects and provide feedback to the machine operator. These results demonstrated that the proposed framework could be used to create the foundation for further developing a closed-loop feedback system for powder-bedbased AM technologie
AFRIKAANSE OPSOMMING: Met die aanbreek van die vierde industriële revolusie, is daar 'n toenemende aaneming van poeierbedgebaseerde toevoegende vervaardiging (AM) tegnologieë saam met konvensionele vervaardigings tegnologieë in gereguleerde nywerhede soos die lugvaart en medies velde. Dit bring mee, dat daar vir die afgelope paar jaar n strewe was om die kwaliteit van onderdele wat met hierdie AM-tegnologie vervaardig word te waarborg in vergelyking met die van konfensionele tegnologieë. Hoewel 'n beduidende volume navorsing baseer was om onderdeel kwaliteit te verifieer as deel van die naverwerkingsproses, kan dit gewoonlik slegs gedoen word deur nie-vernietigende toetsmetodes (NDT) te gebruik. Hierdie prosesse is egter dikwels duur en tydrowend; dus is 'n vereiste vir die insitu monitering van die onderdeel vervaardigingsproses geïdentifiseer. Daar is verskeie studies wat gepoog het om hierdie vereiste aan te spreek. Tog het die meeste van hierdie studies slegs gefokus op die identifikasie van defekte wat tydens die vervaardigings proses mag voorkom en, in sommige gevalle, die klassifikasie van defekte volgens die defektipe. Die doel van hierdie studie was dus gefokus op die ontwikkeling van 'n monitering stelsel wat gebruik kan word om die kwaliteit van die poeierbed oppervlakte te monitor en in die toekoms geslote-lus terugvoer aan die masjien beheerstelsel te verskaf oor die toestand van die poeierbed oppervlak. Vir die ontwikkeling van so 'n geslote-lus terugvoer stelsel is dit nodig om defekte te klassifiseer gebaseer op hul tipe, erns en posisie op die poeierbed oppervlak. Hierdie tipe geslote-lus terugvoer stelsel kan nog nie geïmplementeer word nie as gevolg van die unieke aard van die masjien beheerstelsels en die vervaardiger se huiwering teenoor ongevalideerde outonome terugvoerstelsels. Daarom word daar in die vooruitsig gestel dat met die korrekte raamwerke in plek, dit binnekort 'n werklikheid kan word. Gebaseer op hierdie vereistes, was die eerste helfte van hierdie studie hoofsaaklik gefokus op die ontwikkeling van 'n raamwerk wat gebruik kan word om defekte volgens die defek tipe, erns en posisie op die poeierbe doppervlakte te kan klassifiseer. Die studie het ook gefokus op hoe die raamwerk moontlik in die toekoms gebruik kan word om 'n outonome geslote-lus terugvoerstelsel te implementeer wat regstellende aksies op die defekte op die poeierbed oppervlak kan toepas. Die tweede helfte van hierdie studie was gefokus op die fisiese ontwikkeling van 'n monitering stelsel wat gebruik kan word om die poeierbed oppervlak te monitor. Hierdie monitering stelsel het die vermoë gehad om outonoom die defekte op die poeierbed te identifiseer en te klassifiseer en dan verder te verwerk volgens die ontwikkelde raamwerk. Hierdie fisiese implementering van die moniteringstelsel is toe gebruik om beelde te verwerk wat vasgelê is van werklike vervaardigingswerk. Die resultate wat met hierdie monitering-stelsel aangeteken is, is toe evalueer, en dit is bewys dat die voorgestelde raamwerk gebruik kan word om hierdie poeierbed oppervlak defekte suksesvol te klassifiseer en terugvoer aan die masjienoperateur. Hierdie resultate het bewys dat die voorgestelde raamwerk gebruik kan word om die grondslag te skep vir die verdere ontwikkeling van 'n geslote-lus terugvoer-stelsel vir poeierbed-gebaseerde AM-tegnologieë.
Description
Thesis (PhD)-- Stellenbosch University, 2024.
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