A novel forming method of enhanced adhesion-efficient demolding integration is proposed to solve the problems of weak adhesion between the initial forming layer and the printing platform as well as the excessive stripping force at the bottom of the liquid tank when the printing platform rises. Therefore, a digital light processing (DLP) 3D printing forming device equipped with a porous replaceable printing platform and a swing mechanism for the liquid tank is manufactured and verified by experiments. The experimental results show that the porous printing platform can enhance the adhesion between the initial forming layer and the printing platform and improve the demolding efficiency of the forming device. In addition, the pull-out design of the printing platform plate reduces the maintenance cost of the forming device. Therefore, the device has a good application prospect.

In order to explore the effect of printing parameter configurations on the forming performance of Digital Light Processing (DLP) 3D printed samples, printing experiments were carried out on the enhanced adhesion and efficient demolding of DLP 3D printing devices. The molding accuracy and mechanical properties of the printed samples with different thickness configurations were tested. The test results show that when the layer thickness increases from 0.02 mm to 0.22 mm, the dimensional accuracy in the X and Y directions increases first and then decreases, while the dimensional accuracy in the Z direction decreases, and the dimensional accuracy is the highest when the layer thickness is 0.1 mm. The mechanical properties of the samples decline with an increasing layer thickness of the samples. The mechanical properties of the 0.08 mm layer thickness are the best, and the tensile, bending, and impact properties are 22.86 Mpa, 48.4 Mpa, and 35.467 KJ/m2, respectively. Under the condition of ensuring molding accuracy, the optimal layer thickness of the printing device is determined to be 0.1 mm. The analysis of the section morphology of samples with different thicknesses illustrates that the fracture of the sample is a river-like brittle fracture, and there are no defects such as pores in the section of samples.

No abstract

A calculation model of stress field in laser additive manufacturing of walnut shell composite powder (walnut shell/Co-PES powder) was established. The DFLUX subroutine was used to implement the moveable application of a double ellipsoid heat source by considering the mechanical properties varying with temperature. The stress field was simulated by the sequential coupling method, and the experimental results were in good accordance with the simulation results. In addition, the distribution and variation of stress and strain field were obtained in the process of laser additive manufacturing of walnut shell composite powder. The displacement of laser additive manufacturing walnut shell composite parts gradually decreased with increasing preheating temperature, decreasing laser power and increasing scanning speed. During the cooling process, the displacement of laser additive manufacturing of walnut shell composite parts gradually increased with the increasing preheating temperature, decreasing scanning speed and increasing laser power.

Powder laying is a necessary procedure during powder bed additive manufacturing (PBAM), and the quality of powder bed has an important effect on the performance of products. Because the powder particle motion state during the powder laying process of biomass composites is difficult to observe, and the influence of the powder laying process parameters on the quality of the powder bed is still unclear, a simulation study of the biomass composite powder laying process during powder bed additive manufacturing was conducted using the discrete element method. A discrete element model of walnut shell/Co-PES composite powder was established using the multi-sphere unit method, and the powder-spreading process was numerically simulated using two different powder spreading methods (rollers/scrapers). The results showed that the quality of powder bed formed by roller laying was better than that formed by scrapers with the same powder laying speed and powder laying thickness. For both of the two different spreading methods, the uniformity and density of the powder bed decreased as spreading speed increased, although the spreading speed had a more important influence on scraper spreading compared to roller spreading. As powder laying thickness increased, the powder bed formed by the two different powder laying methods became more uniform and denser. When the powder laying thickness was less than 110μm, the particles were easily blocked at the powder laying gap and are pushed out of the forming platform, forming many voids, and decreasing the powder bed’s quality. When the powder thickness was greater than 140 μm, the uniformity and density of the powder bed increased gradually, the number of voids decreased, and the quality of the powder bed improved.