The hand is the bottleneck, and Mujin's 2021 patent says so out loud. US11117256B2, "Robotic multi-gripper assemblies and methods for gripping and holding objects," fences off a robot that carries more than one kind of gripper and chooses between them per object.
The boring truth this addresses: a suction cup is great for a flat box and useless for a mesh bag; mechanical fingers grip the bag and fumble the slick box. A warehouse full of mixed inventory defeats any single end-effector. Classified under B25J 9/1612 (vision-guided manipulation), B25J 15/0616 (gripping heads) and B25J 13/08 (sensing for control), the patent's answer is to stop choosing and carry both.
ROI per square foot, not per keynote: a robot that handles 70 percent of SKUs is not a deployable picker, because the other 30 percent stall the line and force a human intervention. Multi-gripper assemblies push that coverage number up, and coverage is the metric that decides whether the cell runs lights-out or babysat.
The honest cost is mechanical complexity and cycle time. Switching grippers, or carrying a heavier multi-tool head, eats payload and adds the seconds it takes to select and engage the right tool. The patent is a bet that broader coverage is worth the per-pick overhead — a bet that holds in high-mix fulfillment and fails in single-SKU palletizing.
Mujin is one of the quieter winners in warehouse automation precisely because it focused on this unglamorous coverage problem rather than humanoid spectacle. The multi-gripper grant is characteristic: it is not a moonshot, it is a careful answer to why bin-picking pilots stall.
For anyone auditing a picking-robot claim, ask the coverage question. A demo that shows one gripper handling cherry-picked items proves little; a system that switches tools to clear a real, messy bin is the one that earns its floor space.