Optimization of FFF Processing Parameters to Improve Geometrical Accuracy and Mechanical Behavior of Polyamide 6 Using Grey Relational Analysis (GRA)

One of the most widely used additive manufacturing (AM) methods is Fused Filament Fabrication (FFF), which can produce complex geometry parts. In this process, a continuous filament of thermoplastic material is deposited layer by layer to make the final piece. One of the essential goals in the production of parts with this method is to produce parts with high mechanical properties and excellent geometrical accuracy at the same time. Among the various methods used to improve the desired properties of produced parts is to determine the optimum process parameters in this process. This paper investigates the effect of different process parameters on four essential parameters: chamber temperature, Printing temperature, layer thickness, and print speed on cylindricity, circularity, strength, Young’s modulus, and deformation by Gray Relational Analysis method simultaneously. Taguchi method was used to design the experiments, and the PA6 cylindrical parts were fabricated using a German RepRap X500® 3D printer. Then the GRG values were calculated for all experiments. In the 8th trial, the highest value of GRG was observed. Then, to discover the optimal parameters, the GRG data were analyzed using ANOVA and S/N analysis, and it was determined that the best conditions for enhancing GRG are 60 °C in the chamber temperature, 270 °C in the printing temperature, 0.1 mm layer thickness, and 600 mm/min print speed. Finally, by using optimal parameters, a verification test was performed, and new components were investigated. Finally, by comparing the initial GRG with the GRG of the experiment, it was discovered that the GRG value had improved by 14%.

Predicting the effect of build orientation and process temperatures on the performance of parts made by fused filament fabrication

Purpose The performance of the parts obtained by fused filament fabrication (FFF) is strongly dependent on the extent of bonding between adjacent filaments developing during the deposition stage. Bonding depends on the properties of the polymer material and is controlled by the temperature of the filaments when they come into contact, as well as by the time required for molecular diffusion. In turn, the temperature of the filaments is influenced by the set of operating conditions being used for printing. This paper aims at predicting the degree of bonding of realistic 3D printed parts, taking into consideration the various contacts arising during its fabrication, and the printing conditions selected. Design/methodology/approach A computational thermal model of filament cooling and bonding that was previously developed by the authors is extended here, to be able to predict the influence of the build orientation of 3D printed parts on bonding. The quality of a part taken as a case study is then assessed in terms of the degree of bonding, i.e. the percentage of volume exhibiting satisfactory bonding between contiguous filaments. Findings The complexity of the heat transfer arising from the changes in the thermal boundary conditions during deposition and cooling is well demonstrated for a case study involving a realistic 3D part. Both extrusion and build chamber temperature are major process parameters. Originality/value The results obtained can be used as practical guidance towards defining printing strategies for 3D printing using FFF. Also, the model developed could be directly applied for the selection of adequate printing conditions.

Experimental study of infrared – assisted heat pump drying of lime slices

This paper describes the experimental drying of lime slices using an infrared –assisted heat pump dryer. Experiments were carried out on a heat pump dryer model with a capacity of 1 HP integrated with 2000 W infrared radiator whose power can be varied from 0% to 100%. Experiments have been performed with the drying capacity of 1,2 kg/batch and the drying air velocity of 1,2 m/s. Three evaluations were considered: the effect of material thickness on drying time; the effect of temperature in drying chamber and intensity of infrared radiation on drying time, power consumption and product quality. The results showed that the drying process having 3 mm thickness of lime slices, the temperature in the drying chamber of 42,5¸45oC and the radiation intensity of 110¸300W/m2 was the good effective drying range. In addition, the study formulated a linear regression equation for the drying time relationship with drying chamber temperature and infrared radiation intensity. This mathematical model can be used as reference to determine actual drying time as well as a helpful tool for designing infrared - heat pump dryer.

Profile of Producers and Production of Dry-Aged Beef in Brazil

No information is currently available on the profile of producers and production process of dry-aged beef in Brazil, to the best of the authors’ knowledge. We surveyed 37 Brazilian companies that were producing dry-aged beef in 2020 to investigate this market. The absolute and relative frequency of responses was calculated to obtain the sum, average, minimum, and maximum values. From the respondents, dry-aged beef was first produced in 2009, and most producers are located in big cities. Most respondents control and monitor chamber temperature; however, humidity and air velocity only are monitored. The aging period (mostly between 22 to 60 days) was the main indicator of product readiness. The process losses (water loss and crust trimming) can reach 65%. Some producers perform microbiological analyses to ensure product safety and others use tools such as GMP and SOP. The results of this survey may help governmental institutions to develop a standardized industrial protocol for producing dry-aged beef in Brazil.

PENGUJIAN PERFORMA REAKTOR DOWNDRAFT BIOMASSA KOTORAN SAPI

Biomass power plants are electricity generators with alternative energy that utilize organicmaterials, in this case cow dung. The cow dung is then processed to produce syngas. Syngas is used as fuelto turn turbines. In previous studies, a cow manure gasification reactor was designed and manufactured.This reactor is part of a biomass power plant system (PLTBm) which is made separately. The power outputtarget of this PLTBm is 370 kW. The purpose of this study was to examine the performance of the downdraftreactor of cow dung biomass, namely discharge, temperature, and analyze the gas content released by thereactor so that the power that can be generated by the reactor can be obtained. The test results obtained acombustion chamber temperature of 580°C and a discharge of 0.285 m3/s. The composition of the outputgas is acetylene 58.16%, hexane 27.66%, butane 6.38%, and methane 7.8%. From the calculation results,the power generated by the reactor is 342 kW.

Resistance of ETICS with Fire Barriers to Cyclic Hygrothermal Impact

The article presents the results of a set of hygrothermal experiments of an external wall insulated with an ETICS. As an add-on to previous studies, thermal insulation in the form of polystyrene with an additional horizontal strip of mineral wool was used. Laboratory tests were carried out in accordance with ETAG 004. The ETICS test rig was composed of combustible expanded polystyrene foam (EPS) and horizontal strips of noncombustible mineral wool (MW) fire barriers over windows. The physical and mechanical properties of four types of finishing renders (without an additional reinforcement mesh in base coat of the fire barriers) were analyzed across full hygrothermal cycles in a climate chamber. Temperature sensors were mounted onto different ETICS layers to collect thermal data during the weathering. The testing of ETICS regarding their hygrothermal performance revealed that there were no visible defects on any renderings and over the junctions depending on the type of used insulation materials. Results also showed that the joints of EPS and MW have approximately half of their bond strength from polystyrene strength.

Evaluation of heated air jet on pulp chamber temperature at different steps of the restorative protocol

Objectives: Evaluate of the heated air jet temperature (T) in the pulp chamber on cavity 5 depths and photoactivation stages for a bulk fill resin restorative protocol is evaluated. Methods: Class I cavity preparations were conducted at different depths (n = 8) through two protocols for adhesive volatilization (23 °C and 40 °C) and cavities were restored with the Filtek Bulk Fill resin. The pulp chamber temperature variation was evaluated at four steps (times) during the restorative protocol: I (initial), V (after volatilization), A (after photoactivation of the adhesive), and C (after photoactivation of the composite resin). To verify the assumptions of the normality of the errors and homoscedasticity, the Shapiro Wilk and Levene tests were conducted. Subsequently, two-way and three-way analysis of variance was carried out, followed by Tukey's post-hoc analysis (α = 0.05). Results: The maximum T at the different restorative steps, regardless of the volatilization protocol and cavity depth, was as follows: I (36.8 °C) = V (36.9 ºC) < A (37.2 °C) = R (37.8 ºC) (p <0.05). During V, a small greater variation was observed in pulp chamber temperature when dentin was volatilized at 40 °C (p <0.05) at very deep cavity depths (0.31 °C). The largest temperature variations (p <0.05) were observed during A (0.17–0.59 °C) and R (0.50–1.06 °C), reaching peak temperatures in the cavities.

Operative temperature analysis of the honey bee, Apis mellifera

A key challenge for linking experiments of organisms performed in a laboratory environment to their performance in more complex environments is to determine thermal differences between a laboratory and the energetically complex terrestrial ecosystem. Studies performed in the laboratory do not account for many factors that contribute to the realized temperature of an organism in its natural environment. This can lead to modelling approaches that use experimentally derived data to erroneously link the air temperature in a laboratory to air temperatures in energetically heterogenous ecosystems. Traditional solutions to this classic problem assume that animals in an isotropic, isothermal chamber behave either as pure heterothermic ectotherms (body temperature=chamber temperature) or homeothermic endotherms (body temperature is entirely independent of chamber temperature). This approach may not be appropriate for endothermic insects which exist as an intermediate between strongly thermoregulating endotherms and purely thermoconforming species. Here we use a heat budget modelling approach for the honey bee, Apis mellifera L., to demonstrate that the unique physiology of endothermic insects may challenge many assumptions of traditional biophysical modelling approaches. We then demonstrate under modeled field realistic scenarios that an experiment performed in a laboratory has the potential to both overestimate and underestimate the temperature of foraging bees when only air temperature is considered.

Karakterisasi Serbuk Timah dari Sistem Atomisasi Gas Argon Panas - Sub Sistem Gas Alir Tabung Gas

<p class="Abstract">The tin powder was used in some applications and technology such as for part manufacture through alloying, pressing, and sintering process, mixing material for the pyrotechnic application, the main material for solder pasta, mixing material on tin chemical, and others. Therefore, the demand for tin powder with a small size, spherical shape, and high purity is increasing severely. Indonesia (PT. Timah Tbk.) is one of the world’s largest producers of tin raw materials. This raw material can be processed be as powder by the atomization method. In this research, hot argon gas atomization system was used to generated tin powder. Raw tin was melted in a melting chamber with temperature variations of 600, 700, 800, and 900 °C. This experiment generates powder with a dominant size of 37 – 150 mm. Meanwhile, for size powder of 0 – 30 mm, dominated by size range of 0 – 10 mm. Furthermore, the size powder of 0 – 30 mm is composed of tin phase, without tin oxide. The tin powder of melting chamber temperature of 900 °C produces the largest tin powder with a size of 0 – 10 mm and spherical powder.</p>

3D printing of PLA and PMMA multilayered model polymers: an innovative approach for a better-controlled pellet multi-extrusion process

The present work deals with the 3D printing of multimaterials based on PLA/PMMA multilayers directly obtained from pellets. This polymer pair was chosen for their miscibility at the melt state and synergistic properties (i.e., to improve and weather tune the temperature resistance, transparency and thermomechanical properties of their PLA-based materials). Thus, 3D-printed parts with repeating PMMA/PLA/PMMA layers in the Z building direction were successfully prepared in different numbers but maintaining the same composition. The main objective was to better understand the interface/interphase properties developed during this innovative processing. First, further physicochemical and dynamic thermomechanical characterizations were performed. Second, the effects of multi-extrusion 3D printing processing parameters on the thermal stability of PLA, PMMA and their printed specimens were analyzed by GPC. Then, the structuralrheological and mechanical properties of the multilayered systems were investigated in comparison to their equivalent blend. The effects of flow kinematics during extrusion as well as printing chamber temperature (PCT) and infill density (ID) were specifically studied and rationalized. The triggered interfaces were characterized by SEM and subjected to flexural and short-beam three-point bending experiments that proved their dramatic influence on the final mechanical properties. The ultimate aim of this study is to enable successful control of the interfaces/interphases obtained in these 3D-printed PLA/PMMA systems in comparison to other forming processes.