Forum AM Science I

TUESDAY, 22 JUNE 2021

Location: CongressCenter, 3rd floor, Room Panoramasaal


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09:00 - 09:30
Check-In
09:30 - 09:45
Welcome Carl-Zeiss Saal
09:45 - 10:30

Presentation of the current status of Additive Manufacturing at Daimler Buses
Presentation of our 3D printing parts which have already been installed in our premium buses
Change of the current supply chain due to the 3D printing technology
AM Big Picture - Daimler Buses

Ralf Anderhofstadt and Janis Kretz | Daimler Truck AG / EvoBus GmbH - Daimler Buses

Ralf Anderhofstadt and Janis Kretz

10:30 - 11:00
Coffee break & Visit the exhibition
11:00 - 14:30
Forum"Medical, Dental & Orthopaedic Technology" in the room Panoramasaal
Session 1
14:30 - 15:00

In powder bed fusion of polymers (PBF-LB/P, laser sintering (LS)) components are generated by layerwise melting of plastic microparticles by a laser. PBF-LB/P allows for manufacture of individualized pieces at high freedom of design, however, the choice of commercially available feedstock materials is quite limited. Besides improvement of process robustness by further development of PA12-based feedstocks, making up the largest market share, or improvement of PBF devices, development of novel feedstock materials will widen the field of application of PBF-generated components.

Within this contribution the possibilities of liquid-liquid phase separation and crystallization for production of polyamide 11 (PA11), polyoxymethylene (POM) and L-polylactide (PLLA) feedstocks will be outlined. In this process the polymer is dissolved in a stirred autoclave at elevated temperatures in a moderate solvent. Nucleation and particle growth are triggered by cooling. The influence of important process parameters (system composition, stirring temperature) on product properties will be discussed. Moreover, nucleation kinetics and particle growth are addressed. The plastic powders are comprehensively characterized with respect to bulk solid properties (particle size distribution, shape, bulk density, flowability) and structural and thermal characteristics (degree of crystallinity, “sintering window”). Finally, the PBF processability of the obtained powders is assessed by manufacture of specimens.

Dr. Jochen Schmidt | Friedrich-Alexander-Universität Erlangen-Nürnberg

Dr. Jochen Schmidt is leader of the additive manufacturing group at the Institute of Particle Technology (LFG) of Friedrich-Alexander-Universität (FAU) Erlangen-Nürnberg. He studied chemistry at the Friedrich Schiller University Jena from 2000 to 2004. There, he also obtained his doctoral degree in Physical Chemistry in 2008.

His research focus is on the development of processes for production and functionalization of materials for Additive Manufacturing (AM), with an emphasis on novel particle systems for polymer powder bed fusion (PBF), and the characterization of AM materials. He is principal investigator in projects on production and characterization of AM powders being integrated into the Collaborative Research Center 814 "Additive Manufacturing“ (SFB814) established at FAU, respectively, the nationwide priority program SPP 2122 “Materials for Additive Manufacturing”.

15:00 - 15:30

In selective laser sintering of polymers, high process temperatures in conjunction with long processing times and mechanical stresess induced during powder recoating reduce the flowability of the not molten, supporting polyamide 12 material. This decrease can be compensated by refreshing with virgin powder or flow-enhancing additives.

Within this study the effect of hydrophobic fumed silica as flow-enhancing additive on the used powder properties, processability and resulting part properties is analyzed. A suitable additive concentration for refreshment is defined by thermal and bulk characteristics of the utilized powders. Isothermal crystallization kinetics of the polymer material are investigated at process-oriented temperatures and bulk properties are determined by measuring the powder’s bulk density and its angle of internal friction during steady-state shear conditions in an adapted rheometer setup. Furthermore, density, porosity and mechanical properties of parts built using virgin, used and refreshed powder are characterized.

An increase in bulk density, powder flowability and isothermal crystallization kinetics can be detected within the investigated additive concentration. By using refreshed powder, the part density increases while the dimensional accuracy decreases. Based on the results of this study refreshing rates can be reduced by using flow enhancing additives.

Andreas Jaksch | Sonderforschungsbereich 814 - Additive Fertigung, Friedrich-Alexander-Universität Erlangen-Nürnberg

Andreas Jaksch

15:30 - 16:00

The limited material variety of laser sintering increases with polypropylene and extends the technical fields of application. Similar to polyamide 12, which is mainly used in laser sintering, the surface topology of polypropylene components is often inadequate because technical applications increasingly require surface roughness at injection molding level. In addition to reducing surface roughness by chemical and mechanical post-treatment, there is a need to optimize mechanical properties. According to the current state of the art, the laser sintered samples are cleaned by mechanical-abrasive blasting after removal from the powder cake, which does not result in a significant reduction of roughness. Subsequently, further chemical and mechanical post-treatment steps can follow in the field of subtractive post-treatment. In the present investigations, polypropylene samples are immersed in 100 °C warm toluene for varying residence times. This results in a considerable reduction of roughness at constant component dimensions. The variation of the parameters during the mechanical post-treatment by vibratory grinding does not influence the surface roughness. The mechanical properties such as tensile strength and Young´s modulus show no change, regardless of the post-treatment process selected. The elongation at break increases significantly with the immersion time during chemical post-treatment, whereas mechanical post-treatment has no influence.

M.Eng. Livia Wiedau | Lehrstuhl Fertigungstechnik, Universität Duisburg-Essen

Since 07/2017: Scientific Assistant to the University Duisburg-Essen, Chair Manufacturing Technology, Field of Work "Additive Manufacturing Processes - Field of Polymers" Ecamination of post treatment methods of laser sintered PA12 parts
04/2016 - 10/2016: Master thesis
10/2014 - 10/2016: Master degree program, Product Development at the University of Applied Science
03/2014 - 08/2014: Bachelor thesis
09/2010 - 08/2014: Bachelor degree programm, Mechanical Engineering at the University of Applied Science

16:00 - 16:15
Coffee break & Visit to the exhibition
16:15 - 17:00

Panel Discussion "Sustainability" in room Carl-Zeiss

17:00
Get-together

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Wednesday, 23 June 2021

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