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Additive Manufacturing

Together with various other chairs in the College of Mechanical Engineering, the Kunststofftechnik Paderborn is an integral part of the Direct Manufacturing Research Centers (DMRC). The DMRC is concerned with additive production processes, which can be used for producing individual components (Direct Manufacturing) and/or prototypes, and which represent an important technology of the future. Such new production techniques promise advantages in comparison to conventional methods, such as reduced production and processing costs, shorter lead times, complex component geometries, or the on-demand production of components and spare parts. The goal of the DMRC is to improve and further develop additive manufacturing processes and to bring these components to series production.

Additive manufacturing is characterized by joining volume elements in layers. A virtual part, available as a 3D-CAD file, is first sliced into layers of equal thickness before these layers are created and joined to form a physical component. The production of such components can be done according to several different principles; each process, however, relies on the same basic principle of layer-wise production. The DMRC is conducting research on the following processes:

·         Selective Laser Melting (SLM)

·         Laser Sintering (LS)

·         Fused Deposition Modeling (FDM)

This research concentrates on process-specific optimization, as well as cross-procedurally relevant topics such as design guidelines, cost minimization, or similar strategic aspects of all additive manufacturing processes. 

Screening of polymer based AM Technologies

In the field of additive manufacturing (AM), there are a large number of different technologies available on the market. According to ISO 52900, the plastic-based AM technologies alone can be divided into seven process categories, each of which in turn comprises a larger number of technologies. Some of the processes differ considerably in terms of the solidification mechanisms, the starting materials and the process chain. These major differences make a comprehensive, fair comparison of technologies difficult. When looking for a suitable process for an application, detailed knowledge of all processes is required for an optimal selection. For laypersons, a technology selection is therefore difficult to carry out without tools, and even AM experts often do not have detailed knowledge of all existing processes. This is where this project comes in.

The DMRC has many years of experience in the field of Fused Deposition Modelling (FDM), Laser Sintering (LS) and Arburg Plastic Freeforming (APF). This will be used in the project to carry out a comprehensive comparison of selected plastic-based AM technologies.

The aim of this project is to provide an overview of the technologies and to support the technology selection with a tool. The screening focuses on the technologies FDM, LS, APF and Digital Light Processing (DLP). These are the currently available plastic-based AM processes at the DMRC. In addition, the project will be extended to include Multi Jet Fusion (MJF) technology with the help of the expertise of the DMRC partners.


Fused Deposition Modelling with metal powder-filled plastic filaments 2021

A comparatively new approach to the production of metal components is the use of the Fused Deposition Modelling (FDM) process, in which a plastic filament filled with metal powder is used. The components are first generated in the FDM process. Here, the filament is drawn in, melted and then applied in layers in a defined strand geometry. The subsequent process steps correspond to the post-treatment of components manufactured in the Metal Injection Moulding (MIM) process. In a first step, the plastic binder (brown parts) contained in the components (green parts) is removed. Then the remaining metal particles are sintered in an oven to produce purely metallic components (finished parts).

The aim of the project "Fused Deposition Modelling with metal powder-filled plastic filaments 2021" is to investigate the processing of a support material adapted to the building material Ultrafuse 316L. In particular, the strand deposition and interaction between the building material and the support material are to be considered in order to ensure a reliable process. The support material used aims to stabilise the component geometry over the entire process chain and thus enable the production of more complex geometries.


Evaluation and improvement of the processability of TPU in the fused deposition modelling process

For both the design process and the dimensioning of an additively manufactured component, it is important to know the underlying process limits and ideally the design guidelines. In order to support users of additive manufacturing technologies in the design process, a number of research activities have been carried out at the DMRC in recent years. In the case of FDM, the initial focus was on materials such as ABS-M30 and Ultem 9085. However, the ongoing developments in the field of additive manufacturing are also leading to an expansion of the available materials and machines. Thus, the demand for materials with specific properties is also steadily increasing. One of these materials is thermoplastic polyurethane (TPU). To manufacture technical components from this material, the FDM process must be mastered and the limitations of processing must be known.

The aim of this research project is to analyse the process limits in the processing of a selected TPU and to simultaneously optimise the process parameters to improve processability. The material considered is Ultrafuse TPU 85A, which already has a very low hardness for the FDM process. The selection is made against the background that soft materials tend to be more critical to process in FDM. The material selection thus enables the transfer of the research results to other, harder TPU materials.


Development and modelling of the thermal conductivity of highly thermally conductive plastic compounds for the FDM process

The prevailing trend towards an increasing number of variants and, at the same time, shorter product life cycles is presenting product development with the challenge of having to develop an increasing number of product variants ever more quickly and cost-effectively. One way to meet these constantly changing market requirements is rapid tooling. This describes tool and mould construction using additive manufacturing processes. Areas of application are primarily found in injection moulding and deep-drawing mould construction. The advantages for injection mould making include the low development and production costs of additively manufactured mould inserts.

Due to existing disadvantages in the use of additively manufactured mould inserts made of plastic, the aim of the project is the development of highly thermally conductive plastic compounds for the production and use of injection mould inserts manufactured in Fused Deposition Modelling (FDM) for small series production. In this context, the research focus of Kunststofftechnik Paderborn is on the development of a model for the simulation of heat transfer in additively manufactured tools, the experimental testing of the process behaviour of the thermally conductive material in FDM, as well as the development of a prototypical injection moulding tool for testing the defined performance parameters of the filament.


Simulation of the shrinkage behaviour in the fused deposition modelling process

Fused Deposition Modelling (FDM) is one of the most widely used additive manufacturing processes. As with other additive manufacturing processes, components are created layer by layer in FDM. This offers the advantage of great design freedom, which cannot be realised with conventional manufacturing processes, or only with great effort. In addition, the components are produced directly from a prepared CAD file. Layer generation in FDM is achieved by depositing a plasticised thermoplastic strand. For this purpose, the starting material, a filament, is fed through a heated nozzle in the FDM head and melted. For the defined deposition of the melted material, the nozzle is moved in the X-Y plane. Overhangs are supported with a backing material, which is processed with another nozzle. After completion of a layer, the build platform is lowered relative to the nozzle by a layer thickness in the Z direction and the deposition process begins again.

The production of components in FDM usually takes place in a heated build room. The build room temperature is far below the melting temperature of the material to be processed in order to ensure the stability of the already deposited component areas. As a result, the deposited plastic strands cool down and shrink shortly after they are deposited. Thus, each component area shrinks separately. The resulting inhomogeneous shrinkage can cause residual stresses in the component, which in turn lead to distortion and thus to geometric deviations. The shrinkage is currently compensated for in the data preparation prior to production by linear scaling of the component along the three spatial directions. However, previous investigations have shown that this is not a generally valid solution. Therefore, further approaches to shrinkage compensation are to be investigated in this project.

First of all, the possibility of assembling a component from elementary cells is examined in this project. The scaling factors for individual elementary cells are determined and then applied to the entire component. In addition, the FEM simulation of the manufacturing process of components with suitable software will be examined. Accompanying investigations are carried out to determine boundary conditions such as the material exit temperature from the nozzle.

Research of Innovative and Breakthrough Additive Manufactured leading- edge concept (RIB-AM)

The project is part of the Clean Sky 2 funding programme and is carried out in cooperation with other research institutes and Airbus. Clean Sky 2 is a joint commitment between the European Commission and the European aviation industry (a public-private partnership) to achieve defined environmental goals. Environmental goals are, for example, the reduction of CO2, gas and noise emissions from aircraft. Within this project, the development of a novel leading edge concept based on advanced manufacturing and integration techniques will be advanced.

The aim of the project is to develop a novel manufacturing technology for large-format components that can be installed in the primary structure of aircraft. To achieve this goal, the focus will be on the following three key areas: Automated fibre placement with thermoplastics, the use of the FDM process with short fibre reinforced thermoplastics and the development of a new methodology for joining components based on rivet-free applications. The project is divided into several work packages:

The university, represented by Kunststofftechnik Paderborn (KTP), is working on the additive manufacturing of rib structures. The focus here is on the development and optimisation of the Fused Deposition Modelling (FDM) process for short-fibre reinforced thermoplastics. Within the project, a carbon fibre-reinforced polyetheretherketone (PEEK) is being investigated and the processing optimised. The aim is to achieve good processability and satisfactory quality of the resulting parts. To improve the part quality, a procedure has been developed to optimise the material discharge from the FDM nozzle during the manufacturing process. The concept takes into account various influences on the material discharge from the FDM nozzle, with the aim of generating a strand geometry that is as uniform as possible during the manufacturing process. With the help of various methods developed in this concept, the material discharge can now be adjusted depending on the acceleration profile.


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