Additive manufacturing of glass: CO2-Laser glass deposition printing

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Procedia CIRP 00 (2017) 000–000 Procedia CIRP 74 (2018) 272–275

www.elsevier.com/locate/procedia th 10 CIRP 10th CIRPConference Conferenceon onPhotonic PhotonicTechnologies Technologies [LANE [LANE 2018] 2018]

Additive manufacturing of glass: COMay printing 28th CIRP Design Conference, 2018, glass Nantes, deposition France 2-Laser a

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Philipp Witzendorff , Leonhard Pohl the , Oliver Suttmannand , Peter Heinrich architecture , Achim Heinrich A newvon methodology to analyze functional physical of, b b a Jörg Zander , Holger Bragard , Stefan Kaierle existing products for an assembly oriented product family identification b

a Laser Zentrum Hannover e.V., Hollerithallee 8, 30419, Hannover, Germany Quarzglas-Technologie Heinrich GmbH & Co. KG, Im Süsterfeld 4, 52072 Aachen, Germany

Paul Stief *, Jean-Yves Dantan, Alain Etienne, Ali Siadat

* Corresponding author. Tel.:+49-511-2788-337 ; fax: +49-511-2788-100. E-mail address: [email protected] École Nationale Supérieure d’Arts et Métiers, Arts et Métiers ParisTech, LCFC EA 4495, 4 Rue Augustin Fresnel, Metz 57078, France

*Abstract Corresponding author. Tel.: +33 3 87 37 54 30; E-mail address: [email protected]

Abstract

Additive manufacturing is used in several industrial sectors where polymers and metals are established materials. Different academic studies prove that additive manufacturing methods can be applied on glass materials using powder or fiber based material sources. In terms of quartz Abstract glass, with melting temperatures around 2200°C, laser sources are used to achieve the necessary intensities. In the present study, additive A combined laser head focusses laser of quartz glass is the achieved by melting a quartz fiberand with a CO2 laserissource. Inmanufacturing today’s business environment, trend towards more productglass variety customization unbroken. Due to this development, thethe need of radiation onto the glassproduction fiber in order to melt the fiber. A three axis system is used movefamilies. the printing stage and glass substrate. The agile and reconfigurable systems emerged to cope with various products and to product To design and optimize production experimental that COproduct 2-laser glass deposition printing allows for the creation of arbitrary 3D quartz glass structures. This systems as wellinvestigations as to chooseshow the optimal matches, product analysis methods are needed. Indeed, most of the known methods aim to method is envisioned to replace conventional manual glass processes forhowever, production complex hollow glassofstructures which analyze a product or one product family on the physical level. manufacturing Different product families, mayofdiffer largely in terms the number and are present in the medical sector. nature of components. This fact impedes an efficient comparison and choice of appropriate product family combinations for the production © 2018 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license © 2018 Authors. Published by Elsevier Ltd. This is an open access under CC BY-NC-ND license system. AThe new methodology is proposed to analyze existing products inarticle view of theirthe functional and physical architecture. The aim is to cluster (http://creativecommons.org/licenses/by-nc-nd/3.0/) (https://creativecommons.org/licenses/by-nc-nd/4.0/) these products in new assembly oriented product families for the optimization of existing assembly lines and the creation of future reconfigurable Peer-review underBased responsibility of Flow the Bayerisches Bayerisches Laserzentrum GmbH. Peer-review under responsibility of the GmbH. assembly systems. on Datum Chain, the Laserzentrum physical structure of the products is analyzed. Functional subassemblies are identified, and a functional analysis is performed. Moreover, a hybrid functional and physical architecture graph (HyFPAG) is the output which depicts the Keywords: Additive manufacturing, glass, laser similarity between product families by providing design support to both, production system planners and product designers. An illustrative example of a nail-clipper is used to explain the proposed methodology. An industrial case study on two product families of steering columns of thyssenkrupp Presta France is then carried out to give a first industrial evaluation of the proposed approach. © 2017 The Authors. Published by Elsevier B.V. 1. Introduction Several studies prove that additive manufacturing of glass Peer-review under responsibility of the scientific committee of the 28th CIRP Design Conference 2018.

is feasible by different approaches: Glass is a versatile material found in many applications Keywords: Assembly; Design method; Family identification where the glass composition or surface functionalization is • Glass extrusion printing [1,2] customized to meet the application requirements. When high • Selective laser melting/sintering [3,4] chemical inertness, transparency and temperature resistance is • Wire-fed additive manufacturing [4,5] 1.required, Introduction product range and subsequent characteristics quartz glass is usually used. For example, artificial of • the Stereolithography ovenmanufactured sintering [6] and/or kidneys or machines used within semiconductor assembled in this system. In this context, the main challenge in Due to the consist fast development in components. the domain The of modelling and analysis is now only to copeare with single manufacturing of quartz glass First industrial machines are not available which using the communication andthese an ongoing trend components of digitization and products, a limited product rangefor or additive existing manufacturing product families, manufacturing of quartz glass involves glass extrusion printing process of digitalization, manufacturing are facing also to beglass able to analyze and of to compare products to define machining processes such asenterprises milling, drilling and important polishing but borosilicate [7]. In terms quartz glass, temperatures challenges in today’s environments: continuing product families. It can be classical existing and hot processing such market as forming and welding.aThe latter are new above 2000 °C are required forobserved additive that manufacturing which tendency towards reduction of product development times and families regrouped in function clients or features. mostly performed by manual operation with a hydrogen gas product makes the glass are extrusion printing processofunfavorable due to shortened product In addition, there an increasing assembly oriented families are hardly flame as an energylifecycles. source. Small lot sizes, theishard and brittle However, high energy demand and product high temperature stress to atfind. the demand customization, being at the same time On the product family level, mainlytoinallow two materialofproperties and the manual operation leadin toa global a high extrusion nozzle. Selective laserproducts melting differ has shown competition competitors all overcomplex the world.quartz This trend, characteristics: (i) the parts. number of components (ii) led the scrap rate with when manufacturing glass main the creation of 3D printed However, residualand pores which is inducing the development to micro of components (e.g. mechanical, electrical, electronical). structures. These challenges motivatefrom the macro development of type to opaque glass parts [3,4]. The authors from [4,5] use glass markets, results in diminished sizeswhere due complex to augmenting Classical considering mainly single products additive manufacturing of quartzlotglass quartz rods whereasmethodologies the present study uses endless glass fibers which product varieties (high-volume to low-volume production) already existing coating. product Stereolithography families analyze and the glass structures are manufactured in a single step on [1]. one or aresolitary, coated with a polymer To cope with this augmenting variety as well as to be able to product structure a physical levelhigh (components which machine. subsequent oven on sintering allows resolutionlevel) 3D printing identify possible optimization potentials in the existing causes difficulties regarding an efficient definition and 2212-8271 ©system, 2018 Theit Authors. Published by Elsevier Ltd. This is an opencomparison access article of under the CC BY-NC-ND license Addressing this production is important to have a precise knowledge different product families. (http://creativecommons.org/licenses/by-nc-nd/3.0/)

2212-8271 ©under 2018responsibility The Authors. by Elsevier Ltd. ThisGmbH. is an open access article under the CC BY-NC-ND license Peer-review of Published the Bayerisches Laserzentrum (https://creativecommons.org/licenses/by-nc-nd/4.0/) 2212-8271 © 2017 The Authors. Published by Elsevier B.V. Peer-review under responsibility of scientific the Bayerisches Laserzentrum GmbH. Peer-review under responsibility of the committee of the 28th CIRP Design Conference 2018. 10.1016/j.procir.2018.08.109

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of transparent and pure fused silica. However, the part size is restricted by the size of the tank holding the silica-polymer mixture. In addition, shrinkage occurring during sintering has to be considered [6]. The current study aims to produce quartz glass for medical components where the additive manufacturing process also has to be performed on semi-finished quartz glass parts such as tubes. Therefore, wire-fed additive manufacturing of quartz glass is investigated where an endless glass fiber is molten with a CO2-laser. 2. Experimental Setup and Experiments A CO2-laser with a maximum output power of 120 W was used as an energy source. The glass printing head consist of a laser focusing lens with a focal length of f = 190 mm and a self-developed glass fiber feeding system. A three axis system is used to move the printing stage and glass substrate. The laser radiation was applied in defocused position perpendicular to the printing stage/glass substrate with spot diameters between 1-15 mm. The glass fiber was supplied under an angle between 25°-60° degrees with respect to the laser radiation. Printing was performed with fiber feed and axis movement in the same ( ) and opposite ( ) direction. The feed rate of glass fiber and the velocity of the axis movement were kept at the same speed. The supplied glass fiber diameter was approximately 0.5 mm. The glass fiber has a polymer coating with a thickness of 50 µm. The polymer coating is necessary to feed the fiber without breakage. The coating evaporates during laser processing without affecting the deposited quartz glass quality which was shown for welding of quartz glass [8]. Printing was performed on quartz glass plates (HSQ 100 from Heraeus Quarzglas).

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experiments were conducted with a distance of 20 mm between individual printed glass layers. The results are classified similar to the investigations of Lou et al. [9] with: • • • •

Evaporation Discontinuous printing Continuous printing Lack of fusion

Nomenclature ffiber feed rate of glass fiber faxis velocity of axis movement P……laser power 3. Results Figure 2 shows an image which was captured during an additive manufacturing process. The magnification (lower right corner) was taken with a grey filter in front of the camera. The figure illustrates how the experiments were conducted, printing straight glass layers with a distance of 20 mm.

Fig. 2. Process image

Fig. 1. Sketch of CO2 laser glass deposition printing setup

The investigations aim to show which combination of glass fiber feeding rate, laser power and velocity of the three axis moving system is suitable to perform reproducible and stable additive manufacturing of quartz glass with glass fibers as supplied additive. Glass layer consisting of five overlying printed glass filaments are produced for each investigated parameter combination. On each glass substrate multiple

Figure 3 shows the results of the process investigations. Two laser powers (P = 90 W and P = 120 W) were used. The feed rate of the glass fiber and the velocity of the axis movement were kept at the same speed. The direction of the axis movement and the fiber feeding was set in the same ( ) and opposite ( ) direction. At low feed rates evaporation occurs due to overheating of the glass fibers. With increasing feed rates the process shifts from strong evaporation to discontinuous printing. The top image of Figure 4 shows a result within the discontinuous printing regime. In this case the glass fiber temperatures are too high which leads to a very low viscosity of the fiber resulting in deposition of single quartz glass droplets. It has to be noted

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that these droplets are deposited in a very reproducible manner so that the deposition occurs in constant distance and on top of each other. To achieve continuous printing (see Fig. 4 bottom) where the glass fibers are fused on top of each other, the feed rates have to be increased. The process window is larger when using the higher laser power of P=120 W. At P = 120 W, a wide process window of approximately faxis = ffiber = 200 – 300 mm/min was found. Moreover, it was also investigated that printing should be performed with fiber feeding and axis movement in the same direction due to a slightly greater process window. When the feed rates exceed 300 mm/min, heating of the fibers is insufficient so that no fusion occurs between the individual layers.

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Fig. 5. Printed quartz glass cylinder with a diameter of 20 mm and 10 overlying glass layers, P = 120 W, faxis, = ffiber =250 mm/min, .

The process investigations were used to create a cylinder with 20 mm diameter which consists of 10 overlying glass layers, Fig. 5. For this purpose, a rotational axis was used and printing was performed with fiber feeding and axis movement in the same direction. The created cylinder is free of cracks and pores and shows a homogenous connection between the individual layers. 4. Conclusion

Fig. 3. Process regimes with respect to laser power, faxis, ffiber and direction of axis and fiber movement:   fiber and axis movement in same direction;   fiber and axis movement in opposite direction.

Additive manufacturing of quartz glass is feasible by using a CO2-laser which melts a continuously supplied quartz glass fiber. In order to create overlying structures consisting of multiple glass fibers, the heat input has to be controlled. A too high heat input occurring at low feed rates leads to strong evaporation and discontinuous printing. At high feed rates with insufficient heat input and temperatures, fusion between the individual fibers is not present. A reasonable process window was found which allows the creation of arbitrary printed quartz glass structures. The presented method is aimed to replace conventional manual quartz glass production processes. Acknowledgements The investigations were conducted within the project “Development of a new and flexible additive manufacturing method for the production of complex quartz glass products” funded by AIF-ZIM (ZF4102317AG7). References

Fig. 4. Top: Printing result within the discontinuous regime (P= 120 W; faxis=ffiber= 150 mm/min); Bottom: Printing result within the continuous regime (P= 120 W; faxis=ffiber=250 mm/min);

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[5] Luo J., Gilbert L., Qu C., Wilson J., Bristow D., Landers R., Kinzel E., Wire-Fed Additive Manufacturing of Transparent Glass Parts, ASME 2015 International Manufacturing Science and Engineering Conference, Charlotte, North Carolina, USA, June 8–12, 2015, doi:10.1115/MSEC2015-9377 [6] Kotz, F., et int., Rapp B.E. Three-dimensional printing of transparent fused silica glass, Nature volume 544, 2017, pages 337–339, doi:10.1038/nature22061 [7] http://www.micron3dp.com/

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