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The Effect of EBM Process Parameters upon Surface Roughness
Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.ORCID iD: 0000-0001-5954-5898
Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
2016 (English)In: Rapid prototyping journal, ISSN 1355-2546, E-ISSN 1758-7670, Vol. 22, no 3, p. 495-503Article in journal (Refereed) Published
Abstract [en]

Purpose-The surface roughness of products manufactured using the additive manufacturing (AM) technology of electron beam melting (EBM) has a special characteristic. Different product applications can demand rougher or finer surface structure, so the purpose of this study is to investigate the process parameters of EBM to find out how they affect surface roughness. Design/methodology/approach-EBM uses metal powder to manufacture metal parts. A design of experiment plan was used to describe the effects of the process parameters on the average surface roughness of vertical surfaces. Findings-The most important electron beam setting for surface roughness, accorDing to this study, is a combination of speed and current in the contours. The second most important parameter is contour offset. The interaction between the number of contours and contour offset also appears to be important, as it shows a much higher probability of being active than any other interaction. The results show that the line offset is not important when using contours. Research limitations/implications-This study examined contour offset, number of contours, speed in combination with current and line offset, which are process parameters controlling the electron beam. Practical implications-The surface properties could have an impact on the product's performance. A reduction in surface processing will not only save time and money but also reduce the environmental impact. Originality/value-Surface properties are important for many products. New themes containing process parameters have to be developed when introducing new materials to EBM manufacturing. During this process, it is very important to understand how the electron beam affects the melt pool.

Place, publisher, year, edition, pages
2016. Vol. 22, no 3, p. 495-503
Keywords [en]
Additive manufacturing, Electron beam melting, Process parameters, Surface roughness
National Category
Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:miun:diva-25708DOI: 10.1108/RPJ-10-2013-0102ISI: 000379421200006Scopus ID: 2-s2.0-84971264825OAI: oai:DiVA.org:miun-25708DiVA, id: diva2:848091
Available from: 2015-08-24 Created: 2015-08-24 Last updated: 2018-12-14Bibliographically approved
In thesis
1. SURFACE PROPERTIES OF IMPLANTS MANUFACTURED USING ELECTRON BEAM MELTING
Open this publication in new window or tab >>SURFACE PROPERTIES OF IMPLANTS MANUFACTURED USING ELECTRON BEAM MELTING
2016 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis summarizes the results concerning the manufacture of medical implants for bone replacement using electron beam melting (EBM) which is an additive manufacturing (AM) technology, and aims to satisfy the engineering needs for the medical functionality of manufacturing technology. This thesis has focused on some microscopic properties for surfaces and bone integration. The process parameters of EBM manufacturing were studied to ascertain whether they have impacts on surface appearance, as surface properties have impacts on bone integration and implant performance.

EBM manufacturing uses an electron beam to melt metal powder onto each layer in a manner akin to welding. The electron beam is controlled by process parameters that may be altered to a certain extent by the operator. There are individual process parameters for every material, and new parameters are set when developing new materials. In this thesis, process parameters in default settings were altered to ascertain whether it was possible to specify process parameters for implant manufacturing. The blood chamber model was used for thromboinflammation validation, using human whole blood. The model is used to identify early reactions of coagulation and immunoreactions. The material used in this study was Ti6Al4V-ELI, which is corrosion resistant and has the same surface oxide layers as titanium, and CoCr-F75, which has high stiffness, is wear-resistant and is commonly used in articulating joints.

The study shows that among the process parameters researched, a combination of speed and current have the most impact on surface roughness and an interaction of parameters were found using design of experiment (DOE). As-built EBM surfaces show thrombogenicity, which in previous studies has been associated with bone ingrowth.

Surface structure of as-build EBM manufactured surfaces are similar to implants surfaces described by Pilliar (2005), but with superior material properties than those of implants with sintered metals beads. By altering the process parameters controlling the electron beam, surface roughness of as-build parts may be affected, and the rougher EBM manufactured surfaces tend to be more thrombogen than the finer EBM manufactured surfaces. As-build EBM manufactured surfaces in general show more thrombogenicity than conventional machined implants surfaces.

Abstract [sv]

Denna avhandling behandlar tillverkning av medicinska implantat för integration i ben. I fokus är den additiva tillverkningstekniken ”elektronstrålesmältning” ( Electron Beam Melting –EBM), en av flera tekniker som populärt beskrivs med termen 3D-skrivare. Avhandlingen fokuserar på mikroskopiska ytegenskaper och dess inverkan på benintegration. Processparametrarna för EBM-tillverkning studerades för att fastställa hur de påverkar ytans utseende, efter som ytegenskaper har effekt på implantatens funktion.

EBM-tillverkning använder en elektronstråle som likt svetsning smälter ihop metallpulver. Elektronstrålen styrs av processparametrar som till viss mån kan justeras av maskinoperatören. Det finns individuella processparametrar för varje material och nya parametrar utvecklas till varje ny legering. I denna avhandling har ”grundinställningarnas processparametrar” studerats för att ta reda på om det är möjligt att ställa in specifika parametrar till implantattillverkning. Med hjälp av blodkammarmetoden, som använder humant blod, har thromboinflammatoriska egenskaper undersökts. Metoden identifierar tidiga koagulations- och immunologiska reaktioner. Legeringarna som undersökts i denna studie var Ti6Al4V-ELI, som är korrosionsbeständigt med samma uppsättning oxider på ytan som titan har, och CoCr-F75, en legering som har hög styvhet, är slitstarkt och är vanligt förekommande i implantat för leder.

Bland de undersökta processparametrarna visar en kombination av hastighet och ström ha mest inverkan på ytjämnhet och en interaktion mellan parametrar identifierades med hjälp av försöksplanering. EBM-tillverkade ytor visade på thrombogena egenskaper som i tidigare studier kan relateras till god integration i benvävnad.

Ytstrukturen hos EBM-tillverkade ytor liknar de implantatytor som Pilliar (2005) beskriver, men materialegenskaperna är bättre än de materialegenskaper som implantat, med sintrad yta, har. Genom att ändra processparametrarna som styr elektronstrålen kan ytstrukturen påverkas. Grövre EBM-tillverkade ytor tenderar att vara mer thrombogena än de finare EBM-tillverkade ytorna är. Obehandlade EBM-tillverkade ytor i allmänhet är mer thrombogena än vad konventionellt framställda implantatytor är.

Place, publisher, year, edition, pages
Sweden: Mid Sweden University, 2016. p. 40
Series
Mid Sweden University licentiate thesis, ISSN 1652-8948 ; 122
Keywords
electron beam melting, blood coagulation, bone ingrowth, surface roughness, process parameters
National Category
Production Engineering, Human Work Science and Ergonomics
Identifiers
urn:nbn:se:miun:diva-27125 (URN)978-91-88025-49-4 (ISBN)
Presentation
2016-01-22, G1353, Kunskapens väg 8, Östersund, 13:16 (Swedish)
Opponent
Supervisors
Available from: 2016-03-01 Created: 2016-02-24 Last updated: 2016-03-01Bibliographically approved
2. Electron beam melting: Impact of part surface properties on metal fatigue and bone ingrowth
Open this publication in new window or tab >>Electron beam melting: Impact of part surface properties on metal fatigue and bone ingrowth
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Abstract

The aim of this thesis is to investigate aspects on how additive manufacturing (AM) contributes to functional bone implants with the use of the electron beam melting (EBM) technology. AM manufactures parts according to computer-aided design, and the EBM technology melts powder using an electron beam, which acts similar to a laser beam. The topics discussed in this thesis are related to surface roughness that originate from the melted metal powder, and the thesis tries to define some aspects that affect implant functionality. Process parameters steering the electron beam and biocompatibility arising from the surface texture were the initial parts of the PhD studies, and the other half focused on post-processing and fatigue, which are important for medical and industrial applications. There are six studies in this compilation thesis. They are abbreviated as P - process parameters, M - medical applications, and F - fatigue. Studies P, M2, F2, and F3 are journal articles, and M1 and F1 are conference proceedings.

Study P used design of experiments to investigate how process parameters affect the surface roughness of as-built EBM-manufactured parts and concluded that beam speed and energy (current) were the most important parameters that influence the surface roughness.

In studies M1 and M2, EBM-manufactured specimens of cobalt-chromium and titanium alloys were used to evaluate biocompatibility. The blood chamber method quantified the reactions of the human whole blood in contact with the metal surfaces, and the results showed how the as-built EBM surface roughness contributed to coagulation and bone healing.

Rotating beam fatigue equipment was used in studies F1–F3 and study F1 discussed the size effect on fatigue loaded as-built specimens and included specimens with different sizes and with or without hot isostatic pressing (HIP). Study F2 compared as-built and machined specimens and study F3 investigated how Hirtisation, which is a patented electrochemical surface treatment, and HIP affect the fatigue properties that originate from the electrochemical polishing surface topography. The studies showed that a decreased surface roughness increased the fatigue resistance while the stress concentrations (Kt) in the surface of EBM-manufactured specimens decreased.

The thesis concludes that EBM-manufactured as-built surfaces are suitable for direct contact with the bone, and that HIP does not improve the fatigue resistance of parts with as-built surfaces, where crack initiation starts at notches.

Abstract [sv]

Svensk sammanfattning

Denna avhandling behandlar frågeställningar inom tillverkning av benimplantat med additiv tillverkning (Additive Manufacturing, AM), med fokus på EBM-tekniken (Electron Beam Melting, smältning med elektronstråle). Additiv tillverkning bygger produkter utifrån datorkonstruerade modeller (Computer Aided Design, CAD), och EBM-tekniken gör detta genom att smälta ihop metallpulver med hjälp av en energirik elektronstråle likt en laserstråle. Avhandlingen fokuserar på ytstrukturen från det smälta metallpulvret och hur dess egenskaper påverkar funktionen av EBM-tillverkade produkter. Under första delen av doktorandarbetet var fokus på processparametrar som styr elektronstrålen och biokompatibilitet, och under den senare delen har arbetet riktats mot efterbearbetningsmetoder och utmattningsegenskaper, vilket är viktigt för medicinska implantat och industriell användning. Avhandlingen är skriven på engelska och studierna som sammanläggningen består av är döpta och numrerade med förkortningarna P-Processparametrar, M-Medicinska applikationer och F-Fatigue (Utmattning). Avhandlingen består av fyra tidskriftsartiklar kallade studie P, M2, F2 och F3 och två konferensbidrag studie M1 och F1.

Studie P undersökte med hjälp av försöksplanering (Design Of Experiment, DOE) hur processparametrarna påverkar ytgrovheten för EBM-tillverkade produkter och resulterade i att elektronstrålens förflyttningshastighet och energi har störst inverkan på ytgrovheten.

Studierna M1 och M2 använde kobolt-krom- respektive titanlegeringar, tillverkat med EBM-tekniken, och undersökte biokompatibiliteten med hjälp av blodkammarmodellen som kvantifierar blodets reaktioner vid kontakt med metallytan. Resultaten visade att den mycket grova ytan som EBM-tillverkade implantat har, stimulerar till koagulation och implantatinläkning.

Roterande utmattning användes för studierna F1-3, och studie F1 avhandlar hur EBM-tillverkade provstavar med olika storlekar och med eller utan tempererad tryckbehandling (Het Isostatisk Pressning, HIP) påverkar resultaten. Studie F2 jämförde hur den EBM-tillverkade ytan och en maskinbearbetad yta påverkar materialegenskaperna, och studie F3 undersökte hur Hirtisering, en patenterad elektrokempoleringsmetod, och kombinerat med HIP påverkar utmattningsegenskaperna. Studierna visar att minskad ytgrovhet med elektrokempolering ökar hållfastheten samtidigt som spänningskoncentrationerna (Kt) minskar i ytan för EBM-tillverkade ytor.

Avhandlingen visar att EBM-tillverkade ytor lämpar sig för benkontakt och att HIP inte förbättrar utmattningsegenskaperna om den råa ytan behålls.

Place, publisher, year, edition, pages
Sundsvall: Mid Sweden University, 2019. p. 73
Series
Mid Sweden University doctoral thesis, ISSN 1652-893X ; 291
Keywords
Additive Manufacturing (AM), Electron Beam Melting (EBM), As-built surfaces, Bone Ingrowth, Metall Fatigue, Machined Surfaces, Hirtisation, Hot Isostatic Pressing (HIP)
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:miun:diva-35182 (URN)978-91-88527-82-0 (ISBN)
Public defence
2019-01-15, Q221, Akademigatan 1, Östersund, 09:15 (Swedish)
Opponent
Supervisors
Available from: 2018-12-14 Created: 2018-12-13 Last updated: 2018-12-14Bibliographically approved

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Ek, RebeccaRännar, Lars-ErikBäckström, MikaelCarlsson, Peter

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