Building Robot Heads Using 3D-Printing, Silicone Molds, and Injected Plastic

Following up on last week's article about building robot hands with compliant under-actuated fingers, I'd like to examine a technique to build aesthetic shells for robot heads using a combination of 3D-printed master forms, silicone molds, and quick-setting plastic final products.  The technique examined was used by MIT alum Cory Kidd to build 18 prototypes of the Autom weight-loss coach for his PhD dissertation, a product that is being continuously refined at Cory's new startup, Intuitive Automata.  This technique seems a bit involved; I probably would have just outsourced a full 3D printed ABS version of the head, especially since there were 18 of them.  However, I always find these advanced robot fabrication techniques enlightening.

First, let's take a look at the end product.  This is a prototype of Autom, a robotic weight-loss coach to promote long-term dietary adherence that was created by Cory Kidd in pursuit of a PhD from MIT in human-robot interaction.  Crucially, Cory's work showed that a physical robot can be more engaging than a virtual character on a PDA, phone, or computer screen.

To fabricate the head, Cory started off with a 3D SolidWorks model of the final product (below left).  From this model, Cory extracted 3D designs for the various molds, including a 4-part master form that could be 3D printed (below right).

The master form was printed in four separate pieces on a ZCorp 3D printer -- the four-piece segmentation was required to fit in the printer's workspace.  After assembling the four pieces, they were coated in cyanoacrylate (a form or toxic superglue) for added rigidity and sanded down to create smooth surfaces and seems.  Finally, silicone molds were made from the masters by filling them with 7kg (!) of two-part V-1065 mold-making silicone that has been vacuum chambered to remove air bubbles (extra pics here).

These silicone molds are stuck together and filled with a quick-set plastic that hardens in 90 seconds and is fully set in under 5 minutes to produce the final product.

That does it for the aesthetic head covering.  For the internals, Cory built a multiple degree of freedom neck and eyes, as shown below.

The end result was 18 Autom prototypes used to study social robots as weight loss coaches.  If you'd like to read about his build process, you can find it here.

Cory went on to commercialize the concept by co-founding Intuitive Automata, where they have re-vamped the Autom design.  Based on a brief conversation with Cory at IROS 2008 in France, I believe the company is located in Hong Kong.  I'm sure they are using more "industrial" vacuum forming or injection molding for the new design -- perhaps we can get him to weigh in with those build techniques too...? 

While the technique examined above seems effective, it is probably too involved for my prototyping tastes.  With the availability of contract 3D printing houses, I probably would have opted to outsource the fabrication, though probably at higher costs.  At the very least, I would have requested quotes from the fabrication outsourcing general store: MFG.com.