Redistributed from Nest blog: https://nest.tech/hinging-on-design-nest-cam-iqs-hinge-22efb899ce76
In June, we introduced the Nest Cam IQ. Well-proportioned and seamless, it brings out the best in Nest hardware design and engineering innovation. When we started design work, we looked at it as a wide-open opportunity to define the new generation of indoor camera. Our objective was to design an evolution of the existing Nest Indoor Camera and make it feel even more Nesty.
To us, evolution meant keeping the aspects that people love and adding values that make their experience better, with a friendlier and more approachable design that blends well into homes.
After an in-depth evaluation of our own indoor camera and user trends, one of our top insights was that offering huge hinge articulation was one of the key differentiators that made our Indoor Cam so successful in the market. Camera users want this range of articulation to handle all the ways they use the camera, where they place it and what they want to see from each location.
With this learning in mind, we explored ways to make it even better by introducing more integrated and balanced design with the new generation.
One of the first things you notice when setting up your Nest Cam IQ is that the power cable plugs into the base, not the camera head, allowing for clean routing away from your device. We challenged ourselves to have the cable routing go through the hinge mechanism and have the power plug into the base for seamless look and solid stability. If we could do that, we’d create one of the slimmest, most versatile, and most elegant hinges on on any consumer device.
This was an important design choice we made in building Nest Cam IQ, but it also brought major design and engineering implications. How do power and data signals get from the base to the head through a tiny hinge? And how can the hinge move through such a large range of motion without any wires ever being seen?
We explored several mechanism designs to solve these problems. Ball joints were a natural design choice with our device form factor, but we quickly realized we couldn’t achieve the range of motion we wanted without pinching and exposing wires. Pogo pins, spring contacts, and flexible goosenecks are other common ways to route electrical signals through a moving joint, but each of these concepts either lacks the full range of motion we desired, or was aesthetically unacceptable.
Flexible printed circuits (FPCs) are another common technology to route electrical signals through tight spaces. However, FPCs are thin and flat, which means they are suitable for bending in one direction. Since our hinge swivels up and down, as well as left and right, we found our FPC concepts cracked internally with this combination of bending and twisting.
Finding design solutions — and more challenges
Eventually, we concluded that we needed to pass wires through the axle of the hinge to hide them through the full ± 90 degree range of motion. However, routing a concealed wire through the side of the hinge would surely cause the total width of design to grow. To get around this size constraint, we came up with a custom wire bundle that is round going through the hinge, but flat when it exists the hinge axle, saving precious space. This custom multi-section wire bundle gives us the best of both worlds — a slim external hinge profile and hidden wires through the full range of motion.
Wire routing wasn’t our only challenge. The head of the Nest Cam IQ is made of a thick plastic shell, and packs a huge speaker, multiple metal chassis and heat spreaders, and a 4K camera module. In total, the head weighs over 200 grams. All the technology packed into the head created big challenges for the hinge. How could we hold a heavy, densely packed head in place with the friction from such a small hinge mechanism? How could the hinge mechanism be strong enough to survive daily wear and tear?
Friction hinges usually have a stationary component and a moving component. Large stretches of area on the two components are compressed against each other with high force to create friction when the hinge moves. The holding torque from a friction hinge is generally correlated with the size of the hinge, since larger surfaces can support higher compression forces.
In the Nest Cam IQ hinge, we only had about a 10×10 mm envelope for our friction mechanism (including space for wires), so we had to think outside the box to get enough holding torque in such a small space. In the end, we created what we call a double-friction mechanism, which allowed us to have an unusually high torque density. First, we use the cosmetic “ball” surface as one friction interface by pushing against it with a plastic friction block and a high force spring. However, inherent in the mechanism design, we have a bonus friction source on the side of the mechanism by keeping the moving metal surfaces compressed together with a screw. This allows us to essentially double the holding torque without increasing the hinge size.
When it comes to strength of the hinge assembly, the major factors are part geometry, part material choice, and loading path between parts. With such a small hinge and thin individual parts, we knew we could not achieve our design goals through just part geometry, so we focused heavily on materials selection and creating a robust assembly design.
The internal hinge mechanism components are precision machined out of stainless steel and phosphor bronze. These are very strong materials which can withstand a lot of stress before deforming or cracking. The cosmetic shell around the hinge, which we call the Stem, looks like the plastic head and base enclosures, but is actually an extremely stiff steel tube which provides structural reinforcement to the entire hinge mechanism. It is a great example of how we can achieve the beautiful form conceived by our Industrial Designers without compromising on functional engineering requirements.
Speaking of the stem, it is actually one of the most interesting parts in the entire device from a manufacturing perspective. This is a painted steel part that is formed by a process called deep drawing. It is incredible to think this long, slender tube with complex 3D features started out as a flat, circular sheet. Essentially, the metal sheet is stretched little by little over about a dozen stages until it reaches its final shape. Forming metal parts is a common manufacturing process, but seeing a part with this extreme of an aspect ratio is rare for a consumer electronics device, and a great testament to the work of our Manufacturing Operations team.
Thanks for reading about some of the design and development considerations around the hinge, and stay tuned to this blog for other cool Nest engineering and design posts!
Jackson Systems distributes Nest Cam IQ for contractors, visit https://jacksonsystems.com/products/nest-cam-iq-indoor-camera.html for more information.