MODELING OF PHOTOPOLYMER CURING

The paper considers the process of curing a photopolymer material. The effect of light on a photopolymer material triggers a reaction that leads to the conversion of polymer chains, which leads to the release of heat and an increase of temperature, solidification or an increase of stiffness of the material, and is also accompanied by a volumetric shrinkage. Such processes cause the distortion of the initial shape of the material. With nonuniform irradiation of the material, the processes are initiated with different intensities and a certain delay causing residual stresses. Stereolithography technology has become widespread in industry, in which the material is irradiated in certain areas, the so-called masks, after which the uncured material is removed. Modern photopolymer 3d printers are focused on this effect, which cures the material in layers with various masks. In 3D printing, the curing of the upper layer is accompanied by a higher shrinkage relative to the lower one, which by this time has a higher degree of curing leading to residual stresses. Thus, each new layer in a produced part initiates a gradual accumulation of residual stresses. As a result, there is a distortion of the originally planned shape of the product and a loss of strength characteristics. Residual stresses realized during the printing process can exceed the strength of the material, which often leads to a rapid increase in cracks and damage of the printed structure. This study proposes a model of a photopolymer material and an algorithm for modeling curing. It considers the process of stereolithography based on the action of a movable laser. A comparison with the experiment is given.