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In this letter, we show that explosive crystallization can occur sequentially along the same laser scan line either from the liquid phase or in the solid phase. Which phase dominates depends on the laser scan speed, the proximity of the a-Si melting isotherm, and the magnitude of the ’’thermal kick’’ provided by fluctuations in laser power or at localized regions of higher absorption.

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The fatigue performance of polypropylene (PP) at various amplitudes and frequencies on fatigue cycles under tensile test conditions is investigated in this study. The results show that increasing the frequency leads to a decrease in fatigue cycles due to increased cycle time. The decline rate can be divided into two stages, between 1 and 5 Hz. The first stage rapidly decreases fatigue performance as the frequency increases from 1 Hz to 2 Hz or 3 Hz. The second stage has a lower reduction rate, which occurs between 2 Hz or 3 Hz and 5 Hz due to the strengthening effect of increasing frequency. Furthermore, increasing the amplitude from 0.1 mm to 0.4 mm reduces the fatigue cycle due to the higher deformation rate. In summary, expanding both amplitude and frequency reduces the fatigue performance of the PP material. Moreover, according to the scanning electron microscope microstructure, increasing the frequency results in more microcracks in the polymer matrix.

Mold heating is an essential process in plastic injection molding. Raising the temperature of the mold before injecting liquefied plastic can ease the mold-filling process. A cooling channel can be used to transport high-temperature fluids for this purpose, such as hot water or oil. This dual purpose is a cost-effective solution for heating the mold because the target temperature is easily achieved using this method. In addition, a conformal cooling channel (CCC) can provide more efficient mold heating than a straight cooling channel. This study used the response surface methodology to determine the optimum CCC shape for heat distribution in a mold, and the simulation results confirmed its optimization. The average temperature of the mold using a CCC was better than that using a straight cooling channel, and the heat zone was uniform across the mold surface.

As 3D-printed (3DP) patterns are solid and durable, they can be used to create thin wall castings, which is complicated with wax patterns because of the wax’s fragility and high shrinkage ratio. According to this study’s experiment results, polylactic acid (PLA), polyvinyl butyral (PVB), and castable wax (CW) are suitable materials for preparing investment casting (IC) cavities. The results indicate that the casting product with the highest-quality surface is obtained using a cavity prepared using a CW-printed pattern. PLA- and PVB-printed patterns provide a good surface finish for casted products. In addition, the roughness of both the printed and casted surfaces increases as the printing layer height increases. The roughness of the casted surface varies from 2.25 μm to 29.17 μm. This investigation also considers the correlation between the infill ratio and mechanical properties of PLA-printed patterns. An increase in the infill ratios from 0% to 100% leads to a significant increase in the tensile properties of the PLA-printed pattern. The obtained results can be practically used.