Purpose: The paper aims to investigate the problem of heat distribution in FDM 3D printing. The temperature distribution of the material is important because of the occurrence of shrinkage and crystallization phenomena that affect the dimensional accuracy and strength of the material. Design/methodology/approach: The study uses a thermoplastic material (polylactide) and a test stand equipped with a 3D printer adapted to perform thermographic observations. The main source of heat in the study was a molten laminate material and a hot-end head. Findings: When the material is molten at the temperature of 190°C, the temperature of a previous layer increases above the glass transition point (T_g = 64.8°C) and reaches to about 80°C. In addition, at the boundary of the layers, there occurs a permanent bonding of the consecutive layers because of their partial melting. The paper also reports the results of porosity of PLA samples printed at the temperature ranging between 205 and 255°C. The degree of porosity depends on the temperature of the extruded material. Practical implications: The results may be helpful for designers of various printed parts and construction engineers of printing heads and 3D printer chambers. Originality/value: Thermograms of material layers with a height of 0.3 mm are obtained using a thermal imaging camera with a lens for macro magnification (43 pixels/mm).

This paper presents the results of numerical simulations of a non-linear, tristable system for harvesting energy from vibrating mechanical devices. Detailed model tests were carried out in relation to the system consisting of a beam and three permanent magnets. Based on the derived mathematical model and assuming a range of control parameter variability, a three-dimensional image of the distribution of the largest Lyapunov exponent was plotted. On its basis, the regions of chaotic and predictable movement of the considered system exist have been established. With reference to selected plane of the largest Lyapunov exponent cross-sections, possible co-existing solutions were identified. To identify multiple solutions, a diagram of solutions (DS) diagram was used to illustrate the number of existing solutions and their periodicity. The proposed calculation tool is based on the so-called fixed points of Poincaré cross-section. In relation to selected values of the control parameter ω, coexisting periodic solutions were identified for which phase trajectories and basins of attraction were presented. Based on the model tests carried out, it was found that in order to efficiently harvest energy, appropriate transducer adjustment is required. Calibration of the transducer is necessary to obtain the greatest amplitude of vibration of the beam, which corresponds to the phase trajectory limited by external energy potential barriers. As expected, the average voltage induced on the electrodes of the piezoelectric transducer and the average electrical power recorded on the resistive element are directly proportional to the amplitude and average kinetic energy of the beam.

A concept of non-linear electromagnetic system with the rotational magnetic pendulum for energy harvesting from mechanical vibrations was presented. The system was stimulated by vertical excitation coming from a shaker. The main assumption of the system was the montage of additional regulated stationary magnets inside coils creating double potential well, and the system was made with a 3D printing technique in order to avoid a magnetic coupling with the housing. In validation process of the system, modelling of electromagnetic effects in different configurations of magnets positions was performed with the application of a finite element method (FEM) obtaining the value of magnetic force acting on the pendulum. A laboratory measurement circuit was built and an experiment was carried out. The voltage and power outputs were measured for different excitations in range of system operational frequencies found experimentally. The experimental results of the physical system with electrical circuit and numerical estimations of the magnetic field of a stationary magnet’s configuration were used to derive a mathematical model. The equation of motion for the rotational pendulum was used to prove the broadband frequency effect.