Identification of Stability Domains for Flow Parameters in Fused Filament Fabrication Using Acoustic Emission

In Fused Filament Fabrication(FFF),the state of material flow significantly influences printing outcomes.However,online monitoring of these micro-physical processes within the extruder remains challenging.The flow state is affected by multiple parameters,with temperature and volumetric flow rate(VFR)being the most critical.The study explores the stable extrusion of flow with a highly sensitive acoustic emission(AE)sensor so that AE signals generated by the friction in the annular region can reflect the flow state more effectively.Nevertheless,the large volume and broad frequency range of the data present processing challenges.This study proposes a method that initially selects short impact signals and then uses the Fast Kurtogram(FK)to identify the frequency with the highest kurtosis for signal filtration.The results indicate that this approach significantly enhances processing speed and improves feature extraction capabilities.By correlating AE characteristics under various parameters with the quality of extruded raster beads,AE can monitor the real-time state of material flow.This study offers a concise and efficient method for monitoring the state of raster beads and demonstrates the potential of online monitoring of the flow states.

Development and Evaluation of Recycled Polypropylene and Bean Pod Powder Composite Biomaterial for Fused Filament Fabrication

Approximately 450 million tons of plastic and agricultural waste are produced each year in the world. Only a small portion of this plastic waste is recycled, and a small portion of this agricultural waste is used as fuel or fertilizer, and the rest of this waste is left in the environment or is burned, resulting in environmental and air pollution. For proper disposal, plastic and agricultural waste can be used in the manufacture of composites as raw materials. In this study, we had evaluated the use of bean pod powder (BPp) was used as natural reinforcing filler in recycled polypropylene (rPP) based composites. BPp/rPP composite filaments were developed using the extrusion method and the samples were printed by Fused Filament Fabrication (FFF). Composites with rPP matrix containing different weight fractions of BPp (5%, 10% and 15%) were fabricated to observe and compare the mechanical properties (tensile, flexural, and compressive strength) of the filament composites. In addition, the filament surface was analyzed for roughness and particle size of bean pod powder. The results established that BPp/rPP composites exhibited better tensile, flexural, and compressive strength than rPP and pure PP. By adding 5 wt% BPp, the tensile strength of rPP increased from 20.4 MPa to 22.8 MPa. The highest flexural strength (15.05 MPa) was obtained at 5 wt% BPp among all composites and the highest compressive strength (24.5 MPa), was obtained at 10 wt% BPp. Therefore, it can be concluded that by carefully selecting the ratio of BPp to bean pod powder, it is therefore possible to positively influence the mechanical properties of the resulting composite.

Optimization of Extrusion Process Parameters of Recycled High-Density Polyethylene-Thermoplastic Starch Composite for Fused Filament Fabrication

High-density poly-ethylene (HDPE) is a nonbiodegradable recyclable plastic which is widely utilized in single use packaging applications. Consequently, it constitutes a significant amount of plastic waste found in landfills. From literature, it has been shown that parts produced using composites of HDPE with carbohydrate-based polymers, such as thermoplastic starch (TPS), experience mechanical degradation through hydrolytic degradation process. The possible utilization of recycled-HDPE (rHDPE) and TPS composite in nonconventional manufacturing processes such as Fused filament fabrication (FFF) has however not been explored. This study explores the potential application of rHDPE and TPS composites in FFF and optimizes the extrusion process parameters used in rHDPE-TPS filament production process. Taguchi method was utilized to analyze the extrusion process. The extrusion process parameters studied were the spooling speed, extrusion speed and the extrusion temperatures. The response variable studied was the filament diameter. In this research, the maximum TPS content achieved during filament production was 40 wt%. This filament was however challenging to use in FFF printers due to frequent nozzle clogging. Printing was therefore done with filaments that contained 0 - 30 wt% TPS. The experimental results showed that the most significant parameter in extrusion process was the spooling speed, followed by extrusion speed. Extrusion temperature had the least significant influence on the filament diameter. It was observed that increase in TPS content resulted in reduced warping and increased rate of hydrolytic degradation. Mechanical properties of printed parts were investigated and the results showed that increasing TPS content resulted in reduction in tensile strength, reduction in compression strength and increase in stiffness. The findings of this research provide valuable insights to plastic recycling industries and researchers regarding the utilization of recycled HDPE and TPS composites as substitute materials in FFF.

Using fused filament fabrication to improve the tribocorrosion behaviour of 17-4 PH SS in comparison to other metal forming techniques

Fused filament fabrication(FFF)is one of the additive manufacturing processes which has gained more interest because of its simplicity and low-cost.This technology is similar to the conventional metal injection moulding(MIM)process,consisting of the feedstock preparation of metal powder and polymer binders,followed by layer-by-layer 3D printing(FFF)or injection(MIM)to create green parts and,finally,debinding and sintering.Moreover,both technologies provide near-dense parts.This work presents an in-depth study of the processing method’s influence.The porosity,microstructure,hardness,corrosion,and tribocorrosion behaviour are compared for 17-4 PH SS samples processed from powder by additive manufacturing using FFF and MIM,as well as conventional powder metallurgy(PM)samples.MIM samples exhibited the highest macro and microhardness,while corrosion behaviour was similar for both MIM and FFF samples,but superior in comparison to conventional PM samples.However,the FFF-as fabricated samples displayed a significant improvement in tribocorrosion resistance that could be explained by the higher proportion of delta ferrite and retained austenite in their microstructure.

Real-time monitoring of raster temperature distribution and width anomalies in fused filament fabrication process

The aim of this study is to monitor the raster temperature distribution and width anomalies in a fused filament fabrication(FFF)process by an infrared(IR)array sensor.To achieve this goal,two experiments were conducted on a desktop FFF machine.For the first experiment,three normal samples with different raster widths were fabricated,and thermal images of the newly deposited rasters were collected during the process.To process the low-resolution images,a segmentation-based image processing method was proposed.The temperature distributions along the horizontal direction of the raster section and along the raster length were obtained.The temperature features that could indicate the raster widths were extracted and then fed to recognition models for training and testing.The classification performance of the models were evaluated based on the F-score.The models with high F1-scores could be used to recognise width anomalies online.For the second experiment,an abnormal sample with raster width anomalies was fabricated.The temperature features were extracted from the collected experimental data.The obtained features were then fed to the built and evaluated models to recognise the width anomalies online.The effectiveness of the monitoring method was validated by comparing the recognition results with the actual optical images.The support vector machine(SVM)and k-nearest neighbour(KNN)were adopted to build the recognition models.The F1-score and online recognition results of the models were compared.The comparison study shows that SVM is more suitable for our situation than KNN.A method for monitoring the temperature distribution and width anomalies of the FFF raster is provided in this paper.To the best of the authors’knowledge,this is the first study to explore the actual temperature distribution along the horizontal direction of the raster section,and the first study to monitor the width anomalies of the raster in the FFF process.

Recipe Development and Mechanical Characterization of Carbon Fibre Reinforced Recycled Polypropylene 3D Printing Filament

Recycled polypropylene filaments for fused filament fabrication were investigated with and without 14 wt% short fibre carbon reinforcements. The microstructure and mechanical properties of the filaments and 3D printed specimens were characterized using scanning electron microscopy and standard tensile testing. It was observed that recycled polypropylene filaments with 14 wt% short carbon fibre reinforcement contained pores that were dispersed throughout the microstructure of the filament. A two-stage filament extrusion process was observed to improve the spatial distribution of carbon fibre reinforcement but did not reduce the pores. Recycled polypropylene filaments without reinforcement extruded at high screw speeds above 20 rpm contained a centreline cavity but no spatially distributed pores. However, this cavity is eliminated when extrusion is carried out at screw speeds below 20 rpm. For 3D printed specimens, interlayer cavities were observed larger for specimens printed from 14 wt% carbon fibre reinforced recycled polypropylene than those printed from unreinforced filaments. The values of tensile strength for the filaments were 21.82 MPa and 24.22 MPa, which reduced to 19.72 MPa and 22.70 MPa, respectively, for 3D printed samples using the filaments. Likewise, the young’s modulus of the filaments was 1208.6 MPa and 1412.7 MPa, which reduced to 961.5 MPa and 1352.3 MPa, respectively, for the 3D printed samples. The percentage elongation at failure for the recycled polypropylene filament was 9.83% but reduced to 3.84% for the samples printed with 14 wt% carbon fiber reinforced polypropylene filaments whose elongation to failure was 6.58%. The SEM observations on the fractured tensile test samples showed interlayer gaps between the printed and the adjacent raster layers. These gaps accounted for the reduction in the mechanical properties of the printed parts.

Additive manufacturing of antibacterial PLA-ZnO nanocomposites:Benefits,limitations and open challenges

Polymeric biomaterials such as polylactic acid(PLA)play a prominent role in the advancement of biomedical additive manufacturing(AM).PLA offers indeed a very advantageous combination of thermomechanical properties and functional attributes,as it is biobased,biodegradable,biocompatible and easy to print.However,PLA can be damaged by common sterilization methods and is sensitive to most chemical disinfectants,and this may impair its widespread usage.One of the most promising ways to overcome this shortcoming is to provide PLA with embedded antibacterial activity by the addition of appropriate fillers such as zinc oxide(Zn O)nanoparticles.After a detailed introduction to the basic properties of PLA and ZnO nanoparticles,the present review analyzes the main variables that govern the antibacterial activity of PLA-ZnO nanocomposites.Current applications and related manufacturing processes are also presented to showcase the importance of having embedded antibacterial functions in demanding applications such as food packaging and wound dressing.Emphasis is then placed on the emerging literature of the AM of PLA-ZnO nanocomposites,with a focus on fused filament fabrication(also known as fused deposition modeling).Existing gaps and hurdles related to the development and 3D printing of such composites is critically discussed.It is envisioned that a deeper understanding of the processability,thermo-mechanical behavior,biocompatibility and antibacterial efficacy of additively manufactured PLAZnO nanocomposites will foster their adoption in the biomedical field and,ultimately,in all circumstances where it is crucial to limit infection transmission.

3D printing of ABS Nanocomposites.Comparison of processing and effects of multi-wall and single-wall carbon nanotubes on thermal,mechanical and electrical properties

The following paper reports on a comparative study of the effects of two types of carbon nanotubes,namely multiwall(MWCNT)and single-wall(SWCNT)carbon nanotube,on the properties of 3D-printed parts produced with acrylonitrile-butadiene-styrene(ABS)nanocomposites with various CNT loadings of5-10 wt.%.Quasi-static tensile properties and Vicat softening temperature of 3D-printed parts were enhanced with the increasing CNT content.The highest enhancement in tensile properties was observed for the ABS/CNT nanocomposites at 10 wt.%filler loading.3D-printed ABS/SWCNT composites showed higher tensile modulus,better creep stability and higher Vicat temperature.However,the strength of ABS/SWCNT 3D samples is relatively lower than that of ABS/MWCNT.In addition,3D-printed parts exhibited anisotropic electrical conductive behaviour,which has a conductivity of through-layer of about2-3 orders of magnitude higher than cross-layer.The highest conductivity of 3D-printed samples reached25.2 S/m,and 9.3 S/m for ABS/MWCNT and ABS/SWCNT composites at 10 wt.%,respectively.The results obtained,i.e.the successful fuse filament fabrication and the consequent electromechanical properties,confirm that these 3D printable nanocomposite could be properly utilized for the production,and application up to about 90°C,of thermoelectric devices and/or resistors for flexible circuits.