Fiber-reinforced thermoplastic resin filament for 3D printer, and molded article thereof

A fiber-reinforced thermoplastic resin filament for a 3D printer, the fiber-reinforced thermoplastic resin filament comprising:

• a thermoplastic resin impregnated into a plurality of continuous reinforcing fibers, wherein an average value S of a roundness parameter s of a cross section evaluated by a method is 60% to 100%, and a coefficient of variation of diameter lengths of circumscribed circles, which are bases of a plurality of roundness parameters s used to calculate the average value S, is 0% to 10%, wherein the roundness parameter s is determined by:
• (i) taking a photograph of a cross section perpendicular to an axial direction of the fiber-reinforced thermoplastic resin filament for a 3D printer,
• (ii) drawing an inscribed circle and a circumscribed circle of the filament in a cross-sectional image and determining a diameter of the inscribed circle and a diameter of the circumscribed circle,
• (iii) calculating the roundness parameter s defined by equation (1), and
• (iv) repeating (i)-(iii) at a plurality of locations on the fiber-reinforced thermoplastic resin filament for a 3D printer and calculating the average value S of the roundness parameter s
• roundness parameter s=the diameter of the inscribed circle/the diameter of the circumscribed circle×100 (1);
• and
• wherein the fiber-reinforced thermoplastic resin filament has a flexural stiffness of 1 N·m2 or less.