Handheld 3D printing pens seem like a cheaper alternative to those giant autonomous boxes, but they require more patience than most of us can muster, and a decent level of artistic capability. This robot arm can help with the latter, by controlling where the pen can move to ensure better results. Like with a dedicated 3D printer, the Guided Hand system still requires a 3D model to work from. It won't improve your freehand creations. But if you wanted to recreate the Stanford Bunny, the robot arm attached to your 3D printing pen provides various types of feedback both guiding the motion of the pen, but also limiting where it can move.
The arm moves freely while the pen is positioned in areas required to build up the 3D model using extruded plastic. But when it attempts to move outside the area pre-defined by the source model, motors in the robot's arm provide force feedback and physically limit where you can move it. Imagine the feeling of using a ruler to limit where you can scribble with a marker on a piece of paper. Whenever the marker hits the ruler, it abruptly stops.
At the same time, the robot arm can be used to gently guide the pen where it needs to be, if the user has forgotten to print an important detail. Or through vibrations and force feedback, it could modify the texture of the plastic being extruded. If you've ever tried to decorate a cake with a frosting bag while kids were banging on the table, you get the idea.
The Guided Hand system still has its limits. Since the majority of the 3D printing is still being left to human hands, the results will never be comparable to the precision of a dedicated 3D printer that takes hours to create even tiny objects. But for artists looking to dabble in the new medium, think of it like a virtual form of tracing, allowing them to add their own creative flourishes, while still producing a recognisable piece.