Benchmarking of FDM Machines through Part Quality Using IT Grades

The diffusion of Fused Deposition Modeling (FDM) was recently boosted by the expiration of the FDM patent and the subsequent worldwide development of low cost FDM machines by a huge number of small companies. In most of the cases, FDM machines are worth what they cost. Thus the performance of expensive industrial FDM systems is better than that of low cost machines, also known as 3D printers. In this paper a benchmarking is carried out between a Dimension EliteTM by Stratasys and a 3D TouchTM by Bits from Bytes (BFB). The study and comparison is based on a reference part that was designed to fit into the building volume of most of low cost FDM machines. The part includes several classic geometries (planes, cylinders, spheres and cones) of different sizes to cover several ranges of basic sizes as defined by the ISO 286 standard. Geometric features appear both in the concave and convex shapes to account for all design possibilities. The proposed reference part allows to consider a higher number of features for each range of basic sizes with respect to other benchmarking models presented in the literature. Moreover the part does not require support structures for its production, allowing for manufacturing on 3D printers that come with a unique extruder. Replicas of the reference part are printed out of ABS (acrylonitrile butadiene styrene) material with different layer thicknesses using the compared machines. After inspecting the replicas by means of a Coordinate Measuring Machine (CMM), the dimensional accuracy of the compared FDM systems is reported through part quality using IT grades associated with the ISO basic sizes. GD&T values are also evaluated for some of the geometric features appearing on the reference part

Evaluation of the flexural behaviour of 3D printed multimaterial beams

Among Additive Manufacturing (AM) processes, Fused Deposition Modelling (FDM), more popularly renown as 3D printing1, allows the fabrication of multimaterial parts by extrusion of multiple thermoplastic filaments that are then deposited layer after layer. In such a way parts are built bottom to top and the different materials can be deployed in each cross section according to strategies aiming at optimizing the reinforcement through the exploitation of the design freedom of AM technologies. Most diffused commercial materials for FDM are Acrylonitrile Butadiene Styrene (ABS) and the biodegradable PolyLactic Acid (PLA), that are amorphous polymers characterized by similar mechanical properties. The use of semicrystalline polymers in FDM is often avoided because of the higher amount of shrinkage which causes the warpage of the deployed layers during manufacturing. The innovative aspect of this paper is the use of a filament made of a Polyammide (PA) blend as a reinforcement in multimaterial beams of PLA that are fabricated by FDM. The flexural behaviour of the composite beams is evaluated by three point bending tests according to the ASTM D790 method. Owing to the lack of a specific reference for 3D printing, dimensions of the specimens are assumed equal to those of injection molded specimens. Their nominal overall dimensions are 3.25 x 12.7 x 127 mm. In this preliminary study, test specimens are 3D printed with a core of PA having a rectangular cross section, whose width (w) and height (h) are varied. Bending tests show that the PA core increases both the flexural stiffness and the flexural strength of the PLA beam. Experimental results are compared with those of the finite element (FE) simulation of the bending test performed by using Abaqus/CAE software. 3D printing issues are also considered and discussed along with the influence of the layer by layer fabrication on the beam resistance

Effect of recycled powder and gear profile into the functionality of additive manufacturing polymer gears

Purpose Polymer laser powder bed fusion (PBF-LB/P) is an additive manufacturing technology that is sustainable due to the possibility of recycling the powder multiple times and allowing the fabrication of gears without the aid of support structures and subsequent assembly. However, there are constraints in the process that negatively affect its adoption compared to other additive technologies such as material extrusion to produce gears. This study aims to demonstrate that it is possible to overcome the problems due to the physics of the process to produce accurate mechanism. Design/methodology/approach Technological aspects such as orientation, wheel-shaft thicknesses and degree of powder recycling were examined. Furthermore, the evolving tooth profile was considered as a design parameter to provide a manufacturability map of gear-based mechanisms. Findings Results show that there are some differences in the functioning of the gear depending on the type of powder used, 100% virgin or 50% virgin and 50% recycled for five cycles. The application of a groove on a gear produced with 100% virgin powder allows the mechanism to be easily unlocked regardless of the orientation and wheel-shaft thicknesses. The application of a specific evolutionary profile independent of the diameter of the reference circle on vertically oriented gears guarantees rotation continuity while preserving the functionality of the assembled mechanism. Originality/value In the literature, there are various studies on material aging and reuse in the PBF-LB/P process, mainly focused on the powder deterioration mechanism, powder fluidity, microstructure and mechanical properties of the parts and process parameters. This study, instead, was focused on the functioning of gears, which represent one of the applications in which this technology can have great success, by analyzing the two main effects that can compromise it: recycled powder and vertical orientation during construction

Accuracy of down-facing surfaces in complex internal channels produced by laser powder bed fusion (L-PBF)

5noAdditive manufacturing (AM) technology has great potential in manufacturing complex internal channels for several applications such as satellite communication systems, electronics and gas turbine airfoils. These applications can have complex shape and make traditional finishing processes a challenge for additive parts. Therefore, it is desirable that the internal surfaces be as close as possible to the tolerance of the field of application. In this study, a complex component was designed and manufactured in AlSi10Mg alloy through laser powder bed fusion (L-PBF) process. Using the data from the 3D scans, internal surface roughness and deviations from the CAD model were calculated.openopenCalignano F.; Iuliano L.; Galati M.; Minetola P.; Marchiandi G.Calignano, F.; Iuliano, L.; Galati, M.; Minetola, P.; Marchiandi, G

A methodology for evaluating the aesthetic quality of 3D printed parts

Abstract Nowadays, 3D printing is recognized as one of the key technologies that enables the distributed manufacturing adoption. However, inexperienced people might perceive this technology as far from easy user-usability because of evident aesthetic defects on 3D printed parts. In this paper, an indicator-based methodology is proposed for the assessment and the ranking of the aesthetic capability of 3D printers by evaluating the ability of a 3D printer to reproduce a reference part without defects. The reference part includes several geometric features that characterize most of as-built aesthetic defects. In addition, a benchmarking analysis was carried out to show an example of the methodology applied to three different machines

Ti-6Al-4V lattice structures produced by EBM: Heat treatment and mechanical properties

Abstract Additive manufacturing (AM) processes allow producing the complex components in a layerwise fashion. The complexity includes the design of lighter and stronger components by using lattice structures that can be quickly realized through AM technologies. However, the mechanical behaviour of lattice structures is not completely known, especially in the post-treated state. Thus, this work aims to explore the effect of post-treatment on the compressive strength of specimens with lattice structures. The samples are produced using Ti-6Al-4V powder processed by Electron Beam Melting (EBM). The outcomes of this work confirm the correlation between the heat treatment and final mechanical properties

Further development on DMFC device used for analytical purpose: real applications in the pharmaceutical field and possible in biological fluids

The analytical research devoted to the utilization of the direct methanol fuel cell (DMFC) for analytical purposes has been continued. The research reported in this paper concerns two points, one of which was the possibility of improving the features, from the analytical point of view, of a catalytic fuel cell for methanol and ethanol, by introducing an enzyme, immobilized into a dialysis membrane small bag, in the anodic area of the fuel cell. This objective has been fully achieved, particularly using the enzyme alcohol dehydrogenase, which has increased the sensitivity of the method and reduced dramatically the response time of the cell. The second point concerned the opportunity to determine two particular antibiotics having an alcohol functional group in their molecule, that is, imipenem and chloramphenicol. Also, this goal has been reached, even if the sensitivity of the method is not so high

Proposal of an Innovative Benchmark for the Evaluation of 3D Printing Accuracy for Photopolymers

In recent years, the diffusion of additive manufacturing (AM) or 3D printing (3DP) techniques for polymers have been boosted by the expiration of earlier patents from the last century and the development of low-cost machines. Since these technologies become more widespread, there is a need to assess the capability and accuracy of low-cost machines in terms of dimensional and geometric tolerance. To this aim, this work proposes an innovative reference part for benchmarking layerwise processes that involve the curing of photopolymers. The geometry of the part is conceived to include several classical shapes that are easily measurable for defining the part accuracy in terms of ISO IT grades and GD&T values. Two replicas of the reference part were fabricated by stereolithography (SLA) and digital light processing (DLP) using two machines and related proprietary materials by Sharebot Company. The replicas were printed with a layer thickness of 50 μm for the DLP process and 100 μm for the SLA one. The results of dimensional measurements of the replicas, that were carried out using a Coordinate Measuring Machine (CMM), show that the geometric accuracy of the time-consuming DLP process is slightly better than that of stereolithography