With either system you can scale in the following ways:
-Add more shelving units to store more SKUs or to store more of faster moving SKUs.
-Add more robots to process more order lines simultaneously.
-Add more pack stations/labor
Adding more shelving units is limited by floor space. The equivalent scaling for shuttles is adding more aisles. Adding more aisles scales farther than adding more shelving units because it uses the entire vertical height of the building. Even taking mezzanines into account aisles are going to scale farther.
Adding more robots or shuttles will scale until the travel paths are congested. Whichever technology moves faster is going to scale better here. I don't know enough about the speed of the Kiva robots vs shuttles to say who is better here but I suspect shuttles can move faster.
Adding more pack stations is something either type of system can do and I can't see any advantage either system has over the other there. Kiva is probably more flexible here because you don't need expensive conveyor reconfiguration/addition if you want to add more pack stations. Shuttles, with the proper supporting conveyor can probably get higher throughput.
I think where Kiva really shines is in its flexibility. It can store a lot of different types of items and it is flexible in its ability to move stuff around. It is definitely not the most labor efficient goods-to-person automation technology and it is also not a great use of space. It runs into problems if you need to scale up in SKUs per order or overall order lines per day because you don't have enough travel space available to get all that stuff to the pack stations. Based on my ordering habits and what I have seen of friends Amazon is dealing with a very low number of SKUs per order so it works for them.
Adding more shelving units is limited by floor space. The equivalent scaling for shuttles is adding more aisles. Adding more aisles scales farther than adding more shelving units because it uses the entire vertical height of the building. Even taking mezzanines into account aisles are going to scale farther.
Adding more robots or shuttles will scale until the travel paths are congested. Whichever technology moves faster is going to scale better here. I don't know enough about the speed of the Kiva robots vs shuttles to say who is better here but I suspect shuttles can move faster.
Adding more pack stations is something either type of system can do and I can't see any advantage either system has over the other there. Kiva is probably more flexible here because you don't need expensive conveyor reconfiguration/addition if you want to add more pack stations. Shuttles, with the proper supporting conveyor can probably get higher throughput.
I think where Kiva really shines is in its flexibility. It can store a lot of different types of items and it is flexible in its ability to move stuff around. It is definitely not the most labor efficient goods-to-person automation technology and it is also not a great use of space. It runs into problems if you need to scale up in SKUs per order or overall order lines per day because you don't have enough travel space available to get all that stuff to the pack stations. Based on my ordering habits and what I have seen of friends Amazon is dealing with a very low number of SKUs per order so it works for them.