The question we hear most from logistics and retail operators evaluating mobile robots is not "does it work" but "what does it cost in total, not just the unit price." That is the right question. A mobile robot that requires cage infrastructure, floor marking, and operational reconfiguration every time the layout changes has a total cost profile that looks very different from the unit purchase order.
This is a rough model for how that comparison works. It is not a sales tool. It is the actual framework we use when helping operators think through a deployment decision, including the variables where a cage-free approach does not save money.
The hidden cost structure of caged deployment
When an operator buys a conventional autonomous mobile robot that requires an exclusion zone, the upfront costs that appear on a capital expenditure request typically include the robot unit cost, the control system, and installation labor. What is often not on that first request: the cage or safety fencing hardware, floor marking and repainting, productivity loss during installation, and the recurring cost of reconfiguration when the facility layout changes.
In a Japanese warehouse context, safety fencing for a single-aisle caged mobile robot installation typically runs between 280,000 and 650,000 yen in materials, depending on aisle length and the grade of fencing specified. Labor for installation and floor marking adds another 80,000 to 200,000 yen in a standard-complexity installation. These numbers come from published supplier data and conversations with facility engineering contractors in the Kyushu region, not from our own verified installation contracts.
Reconfiguration is where the ongoing cost accumulates. A caged zone is not easy to reconfigure. Moving the fencing requires taking the robot offline, disassembling the safety perimeter, re-mapping the zone in the robot's navigation system, and getting the new configuration reviewed before the robot resumes operation. In a distribution facility that changes its slotting configuration seasonally, this cost occurs two to four times per year per installation zone. At 80,000 to 150,000 yen per reconfiguration event (labor, downtime, and any re-marking required), the cumulative cost over 24 months can equal or exceed the original fence installation cost.
The floor space cost
This is the cost category operators most commonly under-count. An exclusion zone around a mobile robot path reserves floor area that cannot be used for storage, picking operations, or other traffic. In a distribution center where usable floor space is priced against storage density, that is a real operational cost.
A rough rule of thumb: a caged single-aisle mobile robot path typically requires a safety exclusion zone width of 800mm to 1200mm on each side of the robot's path, per ISO 3691-4 guidance on minimum clearance distances for undetected-stop systems. In a 2.5-meter-wide aisle with 800mm exclusion zones on both sides, the effective working aisle width available to human pickers shrinks to roughly 900mm. That is operationally workable but constraining, and it frequently means that the human picker must adjust their route to avoid the robot's exclusion zone -- adding walking distance per pick cycle.
We do not assign a per-square-meter cost in this model because that number varies too much by facility type, region, and whether the space is owned or leased. What we ask operators to do is apply their own facility's cost-per-square-meter to the exclusion zone area and ask whether that space cost changes the payback horizon of the robot deployment.
The cage-free cost structure
A proximity-aware robot that operates in shared-space mode without an exclusion zone eliminates the fence, the floor marking, and the reconfiguration overhead. The tradeoff is a more complex robot system: three-layer sensing architecture, a motion planning layer that enforces deference behavior, and ongoing firmware maintenance to keep sensing calibration within specification.
The sensing and computing hardware in our current design adds roughly 15 to 22% to the robot unit cost compared to an equivalent-payload robot without proximity sensing. That is the upfront cost of the cage-free capability. The question for the ROI model is how quickly that premium pays back against the avoided cage, floor-marking, and reconfiguration costs.
In a simple scenario: one robot in a single warehouse aisle, 24-month deployment horizon, two layout reconfigurations per year. Cage installation and initial marking at 450,000 yen. Two reconfiguration events per year at 100,000 yen each adds 400,000 yen over 24 months. Total avoided cost: 850,000 yen. If the sensing hardware premium is 300,000 to 400,000 yen over the base robot, the payback on the premium occurs within the first reconfiguration cycle, not the 24-month horizon.
The scenario improves with additional robots in the same facility, because each caged unit requires its own exclusion zone and its own reconfiguration cost. At three robots in a facility with regular layout changes, the cage-free premium pays back faster per unit because the avoided reconfiguration cost scales with the number of units.
Where the cage-free model does not save money
We want to be direct about this: the cage-free approach does not reduce costs in all configurations.
In a facility where the robot operates on a fixed permanent path with no layout changes and no human co-occupation during robot operation hours (a common setup for after-hours restocking in some retail environments), cage infrastructure is cheaper than the sensing premium. If the robot never operates near people and the zone never changes, the cage's ongoing cost is near zero and the sensing premium adds cost for a capability that is not used.
Similarly, high-payload operations where the robot is carrying loads heavy enough that any collision at speed is a serious incident regardless of the sensing response time are not the right fit for proximity-aware shared-space operation. Our deceleration envelope is designed for service robot payloads in the 30 to 80kg range. Higher-payload applications -- pallets, heavy goods -- have different safety profiles where physical separation is appropriate.
Building the model for your facility
The four inputs that determine whether the cage-free premium pays back for a given deployment are: initial cage and marking cost, reconfiguration frequency, number of units, and floor space cost. We have a simple spreadsheet we share with operators who are doing this calculation. It is not complex, but putting actual facility-specific numbers into it usually changes the conclusion compared to a generic industry comparison.
One thing the model does not capture: operational continuity. In a caged deployment, a layout change means the robot goes offline until the reconfiguration is complete. In a shared-space deployment, a layout change can be implemented in the robot's navigation system as a software update while the robot continues operating in a limited zone. For facilities where robot uptime is directly tied to throughput targets, that operational continuity has a value that does not appear as a line item in the capital cost comparison but shows up in how facility managers talk about the decision after deployment.
