Three-dimensional molding device and method for molding three-dimensional molded object

A three-dimensional molding device comprising:

• a plasticizing unit that plasticizes a material containing a thermoplastic resin into a molding material;
• a discharge unit that discharges the molding material supplied from the plasticizing unit towards a stage;
• a moving mechanism that changes a relative position between the discharge unit and the stage;
• a heating unit that heats the discharge unit;
• a temperature acquisition unit that acquires a temperature of the molding material placed on the stage;
• and
• a control unit that controls the plasticizing unit and the moving mechanism to arrange the molding material in a layer along a predetermined path, wherein
• the control unit controls the heating unit such that a relationship of a temperature Tb of an existing layer that is a layer of the molding material placed on the stage, a path cross-sectional area Sb of the existing layer, a specific gravity ρb of a first thermoplastic resin contained in a material used for molding the existing layer, a specific heat Cb of the first thermoplastic resin, a temperature Tu of the heating unit, a path cross-sectional area Su of a subsequent layer that is a layer of the molding material placed on the existing layer, a specific gravity ρu of a second thermoplastic resin contained in a material used for molding the subsequent layer, a specific heat Cu of the second thermoplastic resin, a thermal decomposition temperature Td that is a lower temperature between a thermal decomposition temperature of the first thermoplastic resin and a thermal decomposition temperature of the second thermoplastic resin, and a glass transition point Tg that is a higher glass transition point between a glass transition point of the first thermoplastic resin and a glass transition point of the second thermoplastic resin satisfies the following expression (1):
• Td>(Tu×Su×ρu×Cu+Tb×Sb×ρb×Cb)/(Su×ρu×Cu+Sb×ρb×Cb)>Tg (1).