Comparison: Conveyor Systems and Autonomous Mobile Robotics
Use cases, advantages and applications
Conveyors and Autonomous Mobile Robots (AMRs) are both used in logistics, manufacturing, and warehousing, but have critical differences in terms of functionality, flexibility, and applications. Neither system is inherently superior to the other based on the use case, situation, load and operational goals. When you need to build a product transport system, they can often work in tandem to create the best solution.
Comparisons: AMRs vs. conveyors
Functionality and general usage
Conveyors: Conveyors are fixed, linear systems that efficiently and predictably transport items from point to point. Conveyors excel in operations where there are many repeatable steps, like a carton moving from induction, past pick locations and eventually to a defined destination. This is a sequence of movement very typical of a zone picking operation or fixed production line. Conveyors are ideal for longer distances and fixed missions. Conveyors can interface with most types of automation
AMRs: Autonomous Mobile Robots are versatile, self-propelled carriers equipped with sensors and navigation systems that let them move freely and autonomously. They move without much fixed infrastructure and can perform some more sophisticated tasks (sorting, collaboration with people, integration with other material handling systems).
Flexibility and scalability
Conveyors: Conveyors require a static layout, so it’s important to have a defined plan for your system and the ways your business might change over time. You can change a conveyor layout, but that typically requires new equipment, planning and time. Conveyors offer a less flexibility in terms of plant layout, but also have flexible options in terms of applications. You can build a system that runs at different speeds based on the shift, load profile, and application. For instance, with a conveyor system, you can buffer product vertically or on a line for upstream functions. Conveyors can use vertical space with spirals, or incline systems that AMRs cannot typically access.
AMRs: AMRs require no fixed floor infrastructure. Unlike conveyors, you don’t need to hang them from ceilings or bolt to the floor in a defined layout. They can be reprogrammed or reconfigured to adapt to layout changes, making them suitable for dynamic environments with evolving tasks. AMRs can be scaled up without adding infrastructure, in that you can add more robots when you can add more robots as needed. AMRs can traverse rack aisles and other areas where conveyors are inefficient.
Integration options
When it comes to integration options, both systems have their advantages. AMRs can work with many types of systems due to their mobile and flexible nature. Conveyors are similar in that they integrate with many other types of machinery and equipment, from packaging systems to scanners to carousels and AS/RS. Most modern packaging machinery, palletizers and production technology can accept input from and output to conveyors. Neither conveyors or AMRs are particularly better than the other when it comes to integrations.
Space utilization
Above: conveyors can become effective buffers for downstream processes
AMRs are often portrayed as more space-efficient than conveyors – which is partially true. AMRs don’t command a large share of facility floor space the way conveyor systems often do, but they do require operational space and storage zones. They’re particularly useful in “tricky” applications, complex operations and tighter spaces. AMRs shine in operations where they can execute tasks by moving through a twisty layout, across short distances.
Conveyors require fixed infrastructure, which eats space, but can also take advantage of the vertical cube in ways AMRs struggle to match. The larger the facility, the more conveyors make sense as they can run on elevated platforms, attached to ceilings and in areas on the perimeter of a large storage area like a pick module. AMRs don’t have any significant capacity to buffer products to wait for upstream processes like packing or assembly to occur.
Throughput and speed
Conveyors are faster than autonomous robots – in some cases, they’re orders of magnitude faster. But this speed comes at the price of rigid layouts. They shine in continuous, higher-volume applications where their speed simply outclasses AMRs. However, robots can operate fast enough for specific types of transport and in systems where speed isn’t the priority.
Safety
Both conveyors and AMRs are generally safe to operate.
- AMRs have navigational and other safety features to help avoid pedestrian collisions with pedestrians, machinery or equipment. These systems are reliable, but not infallible. As with human-driven forklifts, the dangers of a collision increase whenever there is clutter, lower visibility and more frequent pedestrian interaction. When people and vehicles operate in the same space, there is always the chance of an accident. Since they are software-controlled, cybersecurity must be robust.
- Conveyor safety is more focused on preventing people from being injured in gears, rollers or belts. These pinch points can cause injuries ranging from minor to severe. Conveyors can also spill products that can fall onto people below. Like any machine, conveyor may have electrical or mechanical issues that can injure people. Safety guards are critical for conveyor safety.
Whether you’re operating conveyors, AMRs or any other type of machinery, training, planning and vigilance are necessary for a safer operation.
Read more: How to Use Conveyors to Increase Warehouse Ergonomics
Investments and ROI
Both conveyors and AMRs have upfront costs and specific ROI cases, but have important cost differences.
- Conveyors cost more to install than AMRs, which are not “installed” like fixed conveyors. AMRs tend to have more IT and software integration needs.
- Both systems require ongoing maintenance and repair needs. However, a particular AMR can be offline without shutting down the operation, where a broken conveyor can shut down flow for at least the line it services.
- AMRs are easier to reconfigure than fixed-layout conveyor systems.
- On a cost-per-unit moved basis, AMRs tend to be more expensive. The more the system is operated, the more cost-effective it is. A conveyor that is used consistently over a long shift will move that load more economically than an AMR-based strategy. However: the lower the volume, the more cost-effective AMRs become.
The bottom line is that the technology you use must fit your application
The choice between conveyors and AMRs depends mostly on your operational needs. Conveyors are ideal for repeatable, high-volume, fast-moving and standardized material handling operations, while AMRs offer flexibility, adaptability, and versatility for tasks that require agility and navigation for operations that shift, move and change quickly. The reality is that they are often at their best in tandem, integrated with each other to leverage their strengths.
Scott Stone is Cisco-Eagle's Vice President of Marketing with more than thirty years of experience in material handling, warehousing and industrial operations. His work is published in multiple industry journals an websites on a variety of warehousing topics. He writes about automation, warehousing, safety, manufacturing and other areas of concern for industrial operations and those who operate them.