Abstract: A modeling method for a workpiece and the workpiece are provided. When the workpiece, at least a part of the workpiece has a hollow region and two or more openings linking an inside and the outside of the hollow region, is additively manufactured, a temporary closure to block at least one of the two or more openings of the hollow region is manufactured at a same time as laminating of a wall section of the hollow region. A peripheral edge of the temporary closure joined to the wall section, and the temporary closure has a flow hole allowing a fluid to flow in or out of the hollow region, then the temporary closure is removed after the fluid has flowed in or out.

Abstract: A method for producing a resin sintered body 1 by applying an ink 3 to thermoplastic resin powder 2 and sintering the powder, the method including the step of immersing an intermediate resin sintered body 1m, which has an unevenly colored region on the surface thereof and the whole of which has been already sintered, in a surface treatment liquid containing sulfuric acid and chromic anhydride, in which the concentration of chromic anhydride is 300 g/L or more, for 5 minutes or longer. When producing a resin sintered body by sintering thermoplastic resin powder, the surface of the resin sintered body can be evenly and sufficiently colored to an extent required without an unevenly colored region on the surface thereof, and also the surface of the resin sintered body can have a good appearance and smoothness.