Robots vs. Conveyors: Which Is Right for Your Operations?

By Tennyson John and Dave Sessoms, Johnson Electric

Autonomous mobile robots (AMRs) are becoming increasingly common in U.S. logistics and manufacturing facilities. ABI Research, a global technology intelligence firm, estimates shipments of AMRs will grow from 547,000 units in 2023 to 2.79 million by 2030 — a compound annual growth rate (CAGR) of nearly 25% per year.

As the utilization of AMRs continues to grow, many operations are beginning to wonder whether they’re a viable alternative to conveyors. The simple answer is: “It depends.” Here are some of the most important factors to consider when weighing these two alternatives.

Cost Models

Many variables can influence the cost of either solution. If you only need a few robots to get the job done, the up-front capital cost of an AMR system is likely to be more attractive than if you need a sizable fleet. On the flip side, the further and faster you need items to travel, the more likely a conveyor will require a larger capital investment. Depending on the size and complexity of the system you need, either solution will typically deliver return on investment (ROI) in one to five years if you purchase it outright.

Some robot manufacturers offer robotics as a service (RaaS) models as an alternative, charging a monthly fee per AMR which includes the robots themselves plus some level of support and maintenance. This approach has the advantage of lower startup costs and allows end users to pay for the system as an operating — rather than a capital — expense.

The price tag of the system isn’t the only cost consideration that matters. Robots might come with a lower energy cost and relieve you of the hassles associated with pneumatic equipment. You’ll also want to factor in labor efficiency. If workers will need to spend a lot of time walking back and forth to a conveyor or pushing carts around, there’s a good chance you can increase productivity by having AMRs handle transport tasks instead. This allows human workers to stay focused on more complicated tasks such as order picking, assembly, inspecting, testing, and so on.

Flexibility and Scalability

AMRs have a clear advantage when it comes to versatility. They can change workflows quickly, transport items to different destinations every time, communicate and work with one another, and reroute around unexpected obstacles independently. Many fleets can become more efficient as they learn the unique patterns and quirks of their sites, use machine learning to improve decision-making, leverage edge computing power, or identify potential improvements with analytics.

AMR systems are also much easier to scale up or down as needed, especially under RaaS agreements. Since they’re essentially “plug and play”, AMRs can be added to a system quickly to assist with load management during peak seasons such as the fourth-quarter holidays. They also make it possible to set up temporary micro-fulfillment centers (MFCs) that benefit from robust automation without installing permanent infrastructure.

Flexibility makes AMRs especially ideal for variable tasks like cross-docking or machine tending. They also excel at working in brownfield sites, whether you’re expanding an existing facility or adapting to a location that wasn’t designed with automation in mind. Robots are compact and maneuverable enough to work in tight spaces and narrow aisles, and don’t have trouble with turning corners. Some can even open electric doors or use elevators to travel between levels.

Conveyors, on the other hand, are about as fixed as infrastructure gets. Most can only move items in one direction; TrueDrive™ MDR from Johnson Electric is a notable exception. Their starting points and destinations are limited and set when they’re designed. They often create barriers to human and vehicle traffic and are expensive to re-route, scale, or replace. Instead of getting smarter over time, they sometimes pose obstacles as operational needs change.

Throughput

If versatility is the superpower of AMRs, it’s tough to match the sheer volume a dedicated conveyor can move. High-speed shoe sorters, tilt tray systems, steerable wheel tables, and even basic motor-driven roller (MDR) lines are workhorse systems that can handle thousands of parcels per hour, day in and day out. They’re less flexible but are likely to be more efficient if you need to process many items quickly.

System Complexity and Safety

Robots continue to get smarter and safer and have evolved to the point where other factors play larger roles in customer decisions. That said, they’re still more complicated than conveyors, relatively new to many U.S. sites, and require complex training.

If a conveyor breaks down, there’s a good chance one of your seasoned employees will be able to grab a wrench and start fixing it right away. On the other hand, if the sensor stack on a robot goes down, you’ll probably need to call the manufacturer. Even if maintenance isn’t a frequent concern, robots and humans both need training to work together effectively. Depending on the system, either may have areas they’re not allowed to enter or travel through. Robots need cameras and other sensors to work safely around people. Human co-workers need to know when and how robots are aware of them, where any emergency stop switches are, and how to move a robot manually if it runs out of power or breaks down.

Infrastructure can also be more complicated. Robots require charging stations and regular downtime to use them, though many can now do so without human intervention. AMRs that move pallets often work best with bespoke pickup and delivery stands. Some fleets also need navigational help from QR codes, magnetic tape, dedicated Wi-Fi, or other extras.

By comparison, learning to interact with a conveyor can be as simple as: “Place stuff here. Don’t place stuff there. Stand on the same side as the O-rings and don’t stick your hand into the machine while it’s running.”

System Footprint

If you operate a sprawling distribution center in “the middle of nowhere,” your conveyor options are limited only by your budget. It’s a different story if you’re running an MFC in the heart of an urban jungle. In sites like these, every square foot needs to count and comes at a premium — if you can get it at all.

AMRs often make more sense in small spaces, where they’re easier to deploy and often cost less. They also make it possible to create temporary pop-up distribution sites during peak seasons.

Integration

Conveyors are typically easier to incorporate into existing systems or combine with equipment made by other manufacturers. This is partly because they’re less complicated than robots, but mostly because they’ve been around much longer.

Every robot manufacturer has their own unique software, and there are few incentives for them to prioritize interaction with competitors’ products. Some larger companies have developed ways to link their fleets to existing WMS and other types of management software, but most mid-tier and startup robotics companies need to rely on another service or partnership for that kind of expertise.

Item Weight

Conveyors have no trouble handling items up to 20 or 30 pounds. A heavy-duty conveyor might be able to go up to 80 pounds if pushed to its limits. Although conveyors designed to move full pallets are available, they’re expensive and take up a lot of floor space. You may want to consider a robotic solution instead if you’re regularly moving heavy stuff.

Even smaller AMRs can often handle loads well over 100 pounds. Those designed to move pallets can boast payload capacities of 4,000 pounds or more — about the weight of a small SUV or 40 bags of cement. Robotic forklifts are also a growing segment of the AMR industry.

Culture

Finally, it’s worth asking yourself how comfortable your organization may be with a relatively new technology like mobile robotics. Some teams are eager to be on the cutting edge, while “old school” workers may require more persuasion to get comfortable with the changes robots can bring.

It’s Not an Either/Or Decision

As we’ve seen, robots and conveyors each have their strengths. It’s even possible for them to work together. For example, robots can add flexibility to your operation by transporting items to and from conveyors or high-density storage systems. AMRs with MDR tops are designed specifically for this purpose. They can also be used for “conveyor bridging”, adding versatility by transporting loads between conveyors in different locations. Mobile robot arms and the emerging technology of humanoid robots can potentially interact with conveyors in much the same way people do.

Ultimately, the ideal approach may not be “conveyors or robots,” but using both technologies to capitalize on what each system does best.

For years, the cutting-edge innovative motion systems of Johnson Electric have enabled leading automotive and industry brands to support the development of the smart future. https://www.johnsonelectric.com/