FDM is 3D printing technology using mainly PLA and ABS as filament materials. PP has close characteristics to PLA and, due to that, is a potential material for for deposition. Paper aims to analyse the behaviour of PP during heating cycle specific to 3D printing process. Macroscopic and microscopic analysis of the deposited strings have been performed. They revealed less stiffness of the PP deposition comparing to PLA, which is due to the lower viscosity of PP. DSC Thermal analysis has been done at it revealed a 30% higher heat flux in PP comparing to PLA and that increases its fluidity. It was recorded a difference between the elongation viscosity of the PP filament and the PP deposited by FDM process. After 5s the deposited PP proves higher values for the elongation viscosity. Dynamic shear rheology measurements the was applied on samples deformed under 210 kN at 190oC. It has been found that the PP requires lower storage energy and that means that it has a lower viscosity for the entire range of applied frequencies. In the same time, the complex viscosities prove different behavior. To improve the control of the deposition shape, it is necessary to reduce the extrusion temperature with 4-5%. That leads to economy in power consumption.

No abstract

The paper aimed to reveal, qualitatively and quantitatively, the modifications suffered by the PLA during the complex heating cycle specific to the 3D printing followed by laser marking. The obtained results showed that the melting point of the PLA decreases from 162.2oC (which is specific to PLA filament) to 153.1oC after the 3D printing process and to 149.7oC after the laser heating. The glass transition suffered the same lowering after the printing process but an important increasing after the laser heating. The elastic modulus evolution proved a decreasing of the plasticity and that is hapenning when the material suffers an increasing of its rigidity. The elongation viscosity was analyzed and its values were decreasing with the increasing of the temperature that happened on the material. The decreasing was produced by the reduction of the elasticity, when the chain branches are decreasing their length. The decreasing is more pronounced with the increasing of the temperature. The ratio between the loss modulus to the storage modulus and quantifies the way in which the PLA absorbs and disperses energy moves its peak from 65oC (curve specific to the PLA filament) to 45oC (curve specific to the last layer deposited by 3D printing process and re-heated by laser beam for marking). The peak means the lowest storage modulus, which is a measure of elastic response of a material, so the transition from glass to high elasticity moves to the lower temperatures.

No abstract

Soldering processes are applied in the fabrication of electronic circuits used in most modern domestic and industrial technologies. This article aims to introduce a new soldering technology based on the microwave joining of copper materials used in electronic applications. The study was focused on microwave technology used as the thermal source for soldering. A simulation model of temperature distributions in copper plates with overall dimensions of 50 × 10 × 0.8 mm was developed in order to determine the necessary microwave power for soldering. For 270 °C simulated on the surface of copper plates, the microwave-injected power was determined to be 598.89 W. An experimental program for 600, 650, 700, and 750 W was set in order to achieve soldering of copper plates in less than 1 min. Soldered copper plates were subject to electrical resistance measurements being obtained with variations up to ±1.5% of the initial electrical resistance of the base materials. The quality of joints has also been analyzed through microscopy after the soldering process. In addition, mechanical properties were determined using a universal testing machine. The results have shown similar behavior of the samples layered with SAC on the one-side and double-side but also a significantly lower force before breaking for one-side-layered samples. An economic analysis was performed and the results obtained have shown that in terms of energy efficiency and total costs for microwave soldering compared with manual soldering, microwave soldering is cost-effective for industrial processing.