Experimental testing of 3D printed polymeric heat exchangers

Unlike conventional manufacturing technologies, additive manufacturing and 3D printing empower engineers with much more design freedom. Heat exchangers with complex internal channels or lattice structures can be designed for layerwise manufacturing by maximizing the surface to volume ratio. Low-weight polymeric heat exchangers are employed in aviation and aerospace applications. For increasing the thermal performance of polymers, additives can be used such as graphene. In this study, a Grafylon filament is used for the production of a simple heat exchanger by 3D printing. The heat exchanger is composed of two external shells and an interior duct with a two-stage 45-degree bend. For watertight purposes, the duct is manufactured by selective laser sintering of polyamide powder. Two replicas of the shells are fabricated by 3D printing of Grafylon and acrylonitrile butadiene styrene (ABS) respectively. The thermal performance of the two materials is experimentally tested and compared also to numerical simulations. The results of the study show that the Grafylon filament provides enhanced thermal performance to 3D printed heat exchangers of polymeric material

Experimental assessment of compensated distortion in selective laser melting of Ti6Al4V parts

Selective laser melting (SLM) is a well-established Additive Manufacturing technique for the fabrication of end-use metal components. Process reliability and maximum product quality are ensured by 20 years of technology development. Nevertheless, depending on the complexity of the part geometry and on the operator experience, different trials are often needed before getting a part first time right. To reduce the number of failed jobs, simulation software packages predict residual stresses and related distortions in SLM parts and propose a compensated geometry for the “right first time” production of the product. In this works, the simulation routines of Amphyon software by Additive Works are experimentally calibrated and validated for the fabrication of a reference geometry by means of an EOSINT M270 machine and Ti6Al4V powder. The calibration of Amphyon is performed using three cantilever specimens and the calibrated SLM simulation is then used to compute the compensated shape of the reference part. The validation of the compensated shape by comparison to the real part geometry shows that Amphyon routines have good prediction capability and dimensional accuracy

Benchmarking analysis of digital light processing resins in terms of dimensional accuracy and geometric tolerances

Additive Manufacturing (AM) is a groundbreaking fabrication technology that is revolutionizing traditional manufacturing processes. Generally, following a layer-by-layer approach, in AM the final shape of the product is built through the progressive deposition of one or more materials. The most common extrusion-based AM technique for thermoplastic polymers is Fused Filament Fabrication (FFF), whilst for photopolymer resins, Digital Light Processing (DLP) and Stereolithography (SLA) are widely used. In the last years, DLP has spread rapidly, due to its low average cost and simple use. Moreover, a lower layer thickness can be used in DLP if compared to the FFF process. Therefore, hobbyists or amateur end users and many companies use DLP to achieve high dimensional accuracy and smooth surfaces for small products. This work aims to evaluate the performance of three different DLP resins in terms of dimensional and geometrical accuracy. A benchmarking activity is carried out using a Rover printer by Sharebot to produce replicas of a reference part using Sharebot resins. After production, the replicas were inspected using a Coordinate Measuring Machine (CMM) for comparing the dimensional accuracy of the geometric features according to ISO IT grades and tolerances of the GD&T system. The results of this study are also compared with previous works from the literature in the conclusions

Development of a low-cost monitoring system for open 3d printing

3D printers for Rapid Prototyping and Additive Manufacturing have been widely accepted by large and small-scale industries or by many hobbyists. Due to its nature of layer by layer addition of material, identifying defects between the layers can be a crucial strategy to determine the quality of a 3D printed product by carefully monitoring the layerwise process during part building. This kind of approach gives an advantage in the applications where 3D printing of products requires high customization without compromise on part quality. In this work, a low-cost camera is installed in an open 3D printer, and computer vision algorithms are used to implement an in-situ monitoring system. The defects can be evaluated by comparing the printed layer to the deposition path of the open ISO G-code. The G-code printing file is modified to introduce the image capture step after each layer. The value of the area of missing or exceeding material is returned to the user with the corresponding images. A decision can be made to abort the job in case of important defects to avoid unnecessary waste in material, time, and costs

An approach to evaluate the wear of customized manufacturing fixtures through the analysis of 3D scan data

With the recent gain in popularity and adoption of additive manufacturing in various industrial sectors, quality assessments to determine the functionality of 3D printed parts are critical. This holds especially when the parts are subjected to wear as in the case of the production of customized fixtures. Some reinforced polymeric materials for additive manufacturing can be employed as a substitute for low-resistance metals like Aluminium. In this paper, a custom-made tribometer was used to simulate the wear of 3D printed fixtures of Alumide material for sheet metal inspection operations. Contact 3D scanning is used to monitor the condition of the fixture for increasing numbers of wear cycles. This study aims to calculate the wear volume of cylindrical pins starting from the surface points of 3D scan data. The methodology employs alpha shapes to obtain the progression of the volume and area of the worn zone. Experimental tests to evaluate the wear volume were carried out to compare the durability of Alumide to that of Aluminium, filling the gap of previous literature, which had focused exclusively on diametral wear. The findings indicate a better wear resistance for Alumide specimens and this work contributes to broadening the knowledge about the wear behaviour and the lifetime of 3D printed parts

Cardioprotective Effects of Taurisolo® in Cardiomyoblast H9c2 Cells under High-Glucose and Trimethylamine N-Oxide Treatment via de Novo Sphingolipid Synthesis

In addition to high plasma glucose, increased levels of trimethylamine N-oxide (TMAO) have been found in obese subjects, where are considered as a novel risk factor for cardiovascular diseases. The present study aimed to investigate the effect of a novel nutraceutical formulation based on grape polyphenols (registered as Taurisolo®) in counteracting TMAO- and high glucose (HG)-induced cytotoxicity in cardiomyoblast H9c2 cells. Cell damage was induced with HG (HG-H9c2) and HG+TMAO (THG-H9c2); both experimental cell models were, thus, incubated for 72 h in the presence or absence of Taurisolo®. It was observed that Taurisolo® significantly increased the cell viability and reduced lactate dehydrogenase and aspartate transaminase release in both HG- and THG-H9c2 cells. Additionally, through its antioxidant activity, Taurisolo® modulated cell proliferation via ERK activation in THG-H9c2. Furthermore, Taurisolo® was able to induce autophagic process via increasing the expression of LC3II, a protein marker involved in formation of autophagosome and ex novo synthesis of sphingomyelin, ceramides, and their metabolites both in HG- and THG-H9c2 cells. Finally, Taurisolo® reduced hypertrophy and induced differentiation of HG-H9C2 cells into cardiomyocyte-like cells. These data suggest that Taurisolo® counteracts the toxicity induced by TMAO and HG concentrations increasing autophagic process and activating de novo sphingolipid synthesis, resulting in a morphological cell remodeling. In conclusion, our results allow speculating that Taurisolo®, combined with energy restriction, may represent a useful nutraceutical approach for prevention of cardiomyopathy in obese subjects

Effect of restriction vegan diet's on muscle mass, oxidative status, and myocytes differentiation: A pilot study

This study was conceived to evaluate the effects of three different diets on body composition, metabolic parameters and serum oxidative status. We enrolled three groups of healthy men (omnivores, vegetarians and vegans) with similar age, weight and BMI and we observed a significant decrease in muscle mass index and lean body mass in vegan compared to vegetarian and omnivore groups, and higher serum homocysteine levels in vegetarians and vegans compared to omnivores. We studied whether serum from omnivore, vegetarian and vegan subjects affected oxidative stress, growth and differentiation of both cardiomyoblast cell line H9c2 and H-H9c2 (H9c2 treated with H2 O2 to induce oxidative damage). We demonstrated that vegan sera treatment of both H9c2 and H-H9c2 cells induced an increase of TBARS values and cell death and a decrease of free NO2- compared to vegetarian and omnivorous sera. Afterwards, we investigated the protective effects of vegan, vegetarian and omnivore sera on the morphological changes induced by H2 O2 in H9c2 cell line. We showed that the omnivorous sera had major antioxidant and differentiation properties compared to vegetarian and vegan sera. Finally, we evaluated the influence of the three different groups of sera on MAPKs pathway and our data suggested that ERK expression increased in H-H9c2 cells treated with vegetarian and vegan sera and could promote cell death. The results obtained in this study demonstrated that restrictive vegan diet could not prevent the onset of metabolic and cardiovascular diseases nor protect by oxidative damage. This article is protected by copyright. All rights reserved

A new inhibitor of glucose-6-phospate dehydrogenase blocks pentose phosphate pathway and suppresses malignant proliferation and metastasis in vivo

Pentose Phosphate Pathway (PPP) is a major glucose metabolism pathway which has a fundamental role in cancer growth and metastasis. Even though PPP blockade has been pointed out as a very promising strategy against cancer, effective anti-PPP agents are not still available in the clinical setting. Here, we demonstrate that the natural molecule polydatin inhibits glucose-6-phosphate dehydrogenase (G6PD), the key enzyme of PPP. Polydatin blocks G6PD causing accumulation of reactive oxygen species and strong increase of endoplasmic reticulum stress. These effects are followed by cell cycle block in S phase, an about 50% of apoptosis, and 60% inhibition of invasion in vitro. Accordingly, in an orthotopic metastatic model of tongue cancer, 100 mg/kg polydatin induced an about 30% tumor size reduction with an about 80% inhibition of lymph node metastases and 50% reduction of lymph node size (p< 0.005). Polydatin is not toxic in animals up to a dose of 200 mg/kg and a phase II clinical trial shows that a is also well tolerated in humans (40 mg twice a day for 90 days). Thus, polydatin may be used as a reliable tool to limit human cancer growth and metastatic spread

Anti-apoptotic seminal vesicle protein IV inhibits cell-mediated immunity.

The in vitro effect of seminal vesicle protein IV (SV-IV) on the cytotoxic activity of human natural or acquired cellular immunity has been investigated by standard immunological procedures, a 51Cr-release cytotoxicity assay, and labeled-ligand binding experiments. The data obtained demonstrate that: (1) fluoresceinated or [125I]-labeled SV-IV binds specifically to the surface of human purified non-adherent monuclear cells (NA-MNC); (2)SV-IV suppresses the cytotoxicity of natural killer (NK) cells against K562 target cells, that of IL-2-stimulated NK (LAK) cells against DAUDI target cells, and that of VEL antigen-sensitized cytotoxic T lymphocytes (CTLs) against VEL target cells; (3) treatment of K562 target cells alone with SV-IV decreases their susceptibility to NK-induced lysis. These findings indicate that the protein SV-IV has a marked in vitro inhibitory effect on NK, LAK and CTL cytotoxicity, providing a better understanding of its immune regulatory functions