Purpose – The purpose of this paper is to systematically and critically review the literature related to process design and modeling of fused deposition modeling (FDM) and similar extrusion-based additive manufacturing (AM) or rapid prototyping processes. Design/methodology/approach – A systematic review of the literature focusing on process design and mathematical process modeling was carried out. Findings – FDM and similar processes are among the most widely used rapid prototyping processes with growing application in finished part manufacturing. Key elements of the typical processes, including the material feed mechanism, liquefier and print nozzle; the build surface and environment; and approaches to part finishing are described. Approaches to estimating the motor torque and power required to achieve a desired filament feed rate are presented. Models of required heat flux, shear on the melt and pressure drop in the liquefier are reviewed. On leaving the print nozzle, die swelling and bead cooling are ...

https://forums.reprap.org/file.php?1,file=42240,filename=A_review_of_melt_extrusion_additive_manufacturing_processes_Process_design_and_modeling.pdf

A review of melt extrusion additive manufacturing processes: I. Process design and modeling

Purpose – The purpose of this paper is to investigate the mechanisms controlling the bond formation among extruded polymer filaments in the fused deposition modeling (FDM) process. The bonding phenomenon is thermally driven and ultimately determines the integrity and mechanical properties of the resultant prototypes.Design/methodology/approach – The bond quality was assessed through measuring and analyzing changes in the mesostructure and the degree of healing achieved at the interfaces between the adjoining polymer filaments. Experimental measurements of the temperature profiles were carried out for specimens produced under different processing conditions, and the effects on mesostructures and mechanical properties were observed. Parallel to the experimental work, predictions of the degree of bonding achieved during the filament deposition process were made based on the thermal analysis of extruded polymer filaments.Findings – Experimental results showed that the fabrication strategy, the envelope temper...

Effect of processing conditions on the bonding quality of FDM polymer filaments

Purpose – The purpose of this paper is to critically review the literature related to dimensional accuracy and surface roughness for fused deposition modeling and similar extrusion-based additive manufacturing or rapid prototyping processes. Design/methodology/approach – A systematic review of the literature was carried out by focusing on the relationship between process and product design parameters and the dimensional and surface properties of finished parts. Methods for evaluating these performance parameters are also reviewed. Findings – Fused deposition modeling® and related processes are the most widely used polymer rapid prototyping processes. For many applications, resolution, dimensional accuracy and surface roughness are among the most important properties in final parts. The influence of feedstock properties and system design on dimensional accuracy and resolution is reviewed. Thermal warping and shrinkage are often major sources of dimensional error in finished parts. This phenomenon is explor...

A review of melt extrusion additive manufacturing processes: II. Materials, dimensional accuracy, and surface roughness

Modeling of Bond Formation Between Polymer Filaments in the Fused Deposition Modeling Process

Fused filament fabrication (FFF) is a 3D printing technique which allows layer-by-layer build-up of a part by the deposition of thermoplastic material through a nozzle. The technique allows for complex shapes to be made with a degree of design freedom unachievable with traditional manufacturing methods. However, the mechanical properties of the thermoplastic materials used are low compared to common engineering materials. In this work, composite 3D printing feedstocks for FFF are investigated, wherein carbon fibres are embedded into a thermoplastic matrix to increase strength and stiffness. First, the key processing parameters for FFF are reviewed, showing how fibres alter the printing dynamics by changing the viscosity and the thermal profile of the printed material. The state-of-the-art in composite 3D printing is presented, showing a distinction between short fibre feedstocks versus continuous fibre feedstocks. An experimental study was performed to benchmark these two methods. It is found that printing of continuous carbon fibres using the MarkOne printer gives significant increases in performance over unreinforced thermoplastics, with mechanical properties in the same order of magnitude of typical unidirectional epoxy matrix composites. The method, however, is limited in design freedom as the brittle continuous carbon fibres cannot be deposited freely through small steering radii and sharp angles. Filaments with embedded short carbon microfibres (∼100 μm) show better print capabilities and are suitable for use with standard printing methods, but only offer a slight increase in mechanical properties over the pure thermoplastic properties. It is hypothesized that increasing the fibre length in short fibre filament is expected to lead to increased mechanical properties, potentially approaching those of continuous fibre composites, whilst keeping the high degree of design freedom of the FFF process.

https://research-information.bris.ac.uk/files/159707908/1_s2.0_S2214860417305687_main.pdf

An investigation into 3D printing of fibre reinforced thermoplastic composites

FDM process fabricates prototypes by extruding a semi-molten filament through a heated nozzle onto a platform. The semi-molten material solidifies with the neighboring material diffusely after deposition. The bonding quality among ABS filaments in FDM2000 process determines the integrity and mechanical property of resultant prototypes. This paper describes heat transfer analysis of the FDM process. Sintering experiments were carried out to evaluate qualitatively the dynamics of bond formation between polymer filaments. Quantitative predictions of the degree of bonding achieved during the filament deposition process were made, based on experimental data used in conjunction with heat transfer and sintering models.

Investigation of Bond Formation in FDM Process

In this paper, dissimilar laser welding of PHS1500 and PHS2000 was carried out by laser welding and laser oscillation welding. The weld appearance, microstructure and mechanical properties of both welded joints were compared and analyzed. Compared to laser welding, an excellent dissimilar weld joint was achieved without any weld concave during laser oscillation welding. Laser oscillation welding was effective to inhibit the formation of δ-ferrite and full martensite was achieved in the weld seam. The hardness of CGHAZ and FGHAZ on PHS2000 side was higher than PHS1500 side due to the solution strengthening. Similar tensile strength for both welded joints and the fracture occurred in the MGHAZ and TZ on PHS1500 side. Laser oscillation welding is potential to reduce the requirement of high assembly accuracy in the industrial manufacture. 

Study on microstructure and properties of laser dissimilar welded joints of ultra-high strength PHS1500/PHS2000 steel

Comparative study of solder wettability on aluminum substrate and microstructure-properties of Cu-based component/aluminum laser soldering joint

Advanced high strength steels (AHSS) with zinc coatings are commonly jointed by using resistance spot welding (RSW). However, the steel/zinc alloy system causes the possibility of liquid metal embrittlement (LME). The role of zinc coatings on the plastic deformation and fracture mechanism of tensile and fatigue has not been systematically explored. In this study, the LME and mechanical properties of zinc-coated AHSS were systematically studied in terms of hot tensile tests by using bare and zinc-coated steel and lap-shear and fatigue tests utilizing RSW joints. The experimental results show that the zinc coating on the specimen surface damages the plastic deformation once the zinc coating appears, and the thickness of Zn coating remains constant regardless of temperature. LME cracking appears on one side due to the tilt of the electrode after the lap-shear test. The LME crack does not affect the fracture process of the fatigue test, as the fatigue crack and LME crack are located on opposite sides. 

Qian Sun

Papers

Modeling of Bond Formation Between Polymer Filaments in the Fused Deposition Modeling Process

Investigation of Bond Formation in FDM Process

Study on microstructure and properties of laser dissimilar welded joints of ultra-high strength PHS1500/PHS2000 steel

Comparative study of solder wettability on aluminum substrate and microstructure-properties of Cu-based component/aluminum laser soldering joint

Zn-induced liquid metal embrittlement and mechanical properties of advanced high-strength steel with resistance spot weld