Material development of non-reinforced and fiber-reinforced polymers for extrusion deposition 3D printing

The aim of this project is to investigate the requirements for materials and semi-finished products which are processed in extrusion deposition 3D printing processes. By gainig a better understanding of these processes, a knowledge base should be created, to increase the variety of materials that are available. This project is conducted in cooperation with Albis Plastic and under the NRW Fortschrittskolleg “Lightweight – Efficient – Mobile” (FK LEM). As one of the six Fortschrittkollegs established in 2014, the FK LEM is sponsored by the Ministry of Culture and Science of the German State of North Rhine-Westphalia.

Objectives
The to be examined extrusion deposition additive manufacturing processes are among the most commonly used additive manufacturing processes. For example, they are known by the terms Fused Deposition Modeling (FDM), Fused Layer Modeling (FLM) or Fused Filament Fabrication (FFF). In this methods, the semi-finished product, commonly a wire of a thermoplastic polymer, is melted and forced through a nozzle. The continuous positioning of this nozzle allows the polymer to weld together strand by strand and layer by layer to produce a component. The energy for the welding of the individual strands largely results from the thermal energy of the deposited polymer melt.

It is desirable to be able to use a similarly wide variety of materials with this method as, for example, in the profile extrusion or injection molding technology. Therefore, the processing suitability of any thermoplastic polymer should be estimated based on the material properties or characteristics in advance of the processing. This is currently not possible because, in contrast to conventional methods, only little is known about the required and desirable material properties for the processing in extrusion deposition additive manufacturing processes.

Procedure
In this project, the requirements for materials, semi-finished products and processes are investigated by the means of example polymer types. For this purpose, different types of polyamide 6 (PA6) will be systematically extruded into monofilaments and then a supervised processing in an extrusion deposition additive manufacturing machine will follow. By varying important material properties, such as the viscosity, the material properties should be connected to the processing properties.

To reach that aim the processability in extrusion deposition additive manufacturing processes has to be defined so that it is evaluable for different materials. Therefore custom-built specimens are created to investigate some significant characteristics like tensile strength of the welding seams or process specific warpage. Other factors like machine quality or data processing should have no or minimal influence. For that reason machine and process specific influences are considered to create custom-built specimens.

After the specimens have been verified on known materials, series of tests should be run for each characteristics. Suitable material properties are identified by rating the processability as a function of the varied material properties. Those are supervised during the whole project by methods like differential scanning calorimetry or high pressure capillary rheometry.

Outlook

In this project, the requirements for materials, semi-finished products and processes are investigated by the means of example polymer types. For this purpose, different types of polyamide 6 (PA6) will be systematically extruded into monofilaments and then a supervised processing in an extrusion deposition 3D printing machine will follow. By varying important material properties, such as the viscosity, the material properties should be connected to the processing properties. In addition, the processing of fiber-reinforced materials should be examined. It is assumed that the procedural generation of components by juxtaposing many strands enables the influence of fiber orientation.