Time for someone to stand up for CaptainHurt. He's basically correct. You are not going to get replacement Lego pieces out of a fused filament printer, at least not ones that work with other Lego pieces. Fact is, the plastic parts you'll get out of a fused filament printer are mere representations of what you are seeking. The technology is crude and there are many,many ways that a print can go wrong. Start with the basic process, which is totally different from the injection molding or blow-molding processes by which most familiar plastic parts are manufactured. Fused filament is incapable of reproducing the uniformity and precision of injection molding. It's distinct advantage is that you can make a one-off item. The costs of producing a mold and the runner required to produce an injected molded part makes it an impractical technology for short production runs.I really want a 3D printer to make free Lego pieces.