<i>A 3D printer is the ultimate expression of a Lego set these days.</i><p>That&#x27;s a good analogy, but I believe it&#x27;s why 3D printing <i>won&#x27;t</i> be mainstream. The explosion in the popularity of Lego models recently is in the brilliant professional designs with commercial licensing that Lego come up with. Designing and making your own Lego models is popular among kids as it always has been, but adults don&#x27;t do it. For an adult a Lego set is a 3D jigsaw puzzle. There&#x27;s zero interest in making your own ideas.