DVT Phase: CNC Tolerances for the Sensor Bay

During the Engineering Verification Test (EVT) phase, our prototypes were housed in 3D-printed SLA resin cases. They worked beautifully on the bench. However, when we moved to the Design Verification Test (DVT) phase and began simulating real-world aggressive typing, the optical tracking degraded significantly.

The Flex Problem

The three IR sensors rely on strict, immutable spatial relationships to triangulate the hand position. In the resin cases, heavy typing caused a microscopic flex across the length of the board. A flex of just 0.2mm on the outer sensor bays altered the stereoscopic baseline enough to introduce a "jitter" into the cursor movement.

Machined Aluminum

To solve this, the final chassis for BoardHand is milled from a solid block of 6061 aluminum. The top case, which houses the sensor bays, is essentially a rigid monolithic beam.

Furthermore, we isolated the PCB assembly from the top case using silicone gaskets. This means the shock of bottoming out a keystroke is absorbed by the internal assembly, and the kinetic energy is not transferred to the rigid top frame holding the optics. The sensors remain perfectly static regardless of typing force.