I recently came across a great chart by the PMMI regarding automated technologies in warehouses. What surprised me is that while conveyors are no surprise as the top technology, sortation systems are one of the technologies that are lagging in implementation.
A conveyor’s main objective is to move products, goods, totes, or pallets from one location to another. Some conveyors can have vertical systems to maximize space, but despite whatever shape they come in, conveyors help transport whatever is needed.
Conveyors are also great at relieving bottlenecks, creating buffers, and increasing throughput. But what is more unfamiliar is the sorting options and technologies, which can integrate within a conveyor system.
I’ve helped support a great number of warehouse automation engineering teams and have learned a great deal of what’s important to know when designing warehouse automation equipment and machinery. Here is what to consider when designing a conveyor as part of a warehouse sortation system.
Cross Belt Sorter
A cross belt sorter is a high-throughput sortation system that uses a continuous loop or main conveyor to carry and kick out items from the main conveyor depending on the sortation need, such as putaway, order fulfillment, docking, shipping, etc. It comes with a throughput of around 500 parts per minute, depending on the application.
In addition to high throughput, the continuous loop conveyor is flexible with integrating into already existing or adding onto automated layouts. Another benefit is that it is one of the lower-cost sortation systems with a generally simple mechanical assembly. Lastly, it’s flexible at handling various kinds of shapes and weights to be sorted on the same line.
Tilt Tray Sorter
A tilt tray sorter is a sortation system that processes items in a similar fashion as the cross belt but uses a tilt tray mechanism instead of a belt. Instead of a belt or mini conveyor to move the part through, mechanically this sortation mechanism tilts or lifts the part at an angle to use gravity to move the items to be further sorted.
The benefits again are similar to a cross belt:
- Tilt trays have very high throughput
- Easy to add on to and integrate
- Can handle a variety of sizes and weights
- Uses a double tray tilt approach for extra-long or large items.
While throughput is very high, it is slightly less than crossbelt. As well as because most tilting mechanisms have one side lifted or slightly higher than level, the weight capacity for parts is generally lower than that of cross belt. While I’ve seen this sortation style used for luggage, it is often most popular with smaller items of varying sizes in a high-speed application.
Shoe Sorter/Slat Sorter
A shoe or slate sorter is another high-throughput system of around 300 pieces per minute. It’s usually straight but can be curved or looped and has a raised shoe, which you can visualize as a raised block that slides along the slat conveyor to push the part to be sorted/diverted depending on the process.
If you’ve watched a video of an automated distribution center, you’ve probably seen these shoe sorters work. In most cases, the shape of the items being pushed by the shoe is typically standardized: boxes of varying sizes, totes or bins, pallets, containers, or crates.
Automation technology has improved so much that many intralogistics companies design a shoe sorter that can accommodate bags and uniquely shaped items. A shoe sorter is good at gently handling products when you do not want to use a gravity-powered conveyance mechanism with more unpredictable movement.
Push Tray Sorter
A push tray sorter has traits of both shoe and tilt tray sorter. But instead of a shoe, you have a bar running the length of the tray, which no longer tilts. The tray allows for the accommodation of all kinds of shapes with the option of using a double tray for larger/longer items.
The bar mechanism, just like the shoe sorter, will physically push the item through. As a bar is a continuous piece the size of the entire tray it allows the flexibility to sort small, light, and difficult to convey items on the same line as heavier items.
Despite the seemingly complexity of this technology, push trays offer high throughput with fewer motors, meaning they are lower cost than a cross belt sorter.
Narrow Belt Sorter
A narrow belt sorter (NBS) uses narrow belt conveyors to transport the items. This system is often seen in high-mid throughput with mid-size and mid-weight items. When the part reaches the designated divert point, high friction wheels pop up between the narrow belt conveyor to push the item down the divert area. Divert lanes are usually installed at a 90-degree or 30-degree angle, depending on the speeds and throughput needed.
NBS are usually simple and allow for flexibility if needed to be reconfigured or integrated with other systems, as well as being quieter and generally lower running costs.
Pivot/Swivel Wheel Sorter
A pivot/swivel wheel sorter is a medium-throughput sortation option with up to 90 items per minute output. As the name implies, parts go down a conveyor until it reaches it’s divert point, where a pivot or swivel wheel section turns the wheels to divert the part on top to divert to a different section for further sortation. Generally, this system is more compact and less costly than a shoe sorter but mostly optimized for mid-sized weights and sizes.
In addition, unconventional sizes and shapes aren’t the best for this style of sorter being optimized for poly bags, bins, totes, and boxes.
Paddle & Pusher Sorter
Paddle and pusher sorters are great for varying sizes and irregular shape sortation with low to mid-throughput. The mechanical process varies slightly, but both generally use a pneumatic-powered paddle or pusher at the divert point. Paddles are large with no clearance underneath for smaller items to slip through as the paddle diverts the entire length of the conveyor to the divert area.
The pusher sorter, which is mechanically different than the push tray sorter, has a pneumatically driven pusher arm across from the divert area that will push the conveyed part down to the divert area. Paddle sorters are great for irregular-shaped items as the paddle is large enough to divert any-sized item.
Pusher sorters are more suited for small- to medium-sized items and can have multiple pusher arms mounted next to each other to increase the amount of divert points and throughput.
ARB Sorter
An ARB sorter is an activated roller belt patented by Intralox, but the technology is used by many sortation and packaging companies. It is a system that uses a modular plastic belt with integrated conveyor rollers to sort, align, and divert products. Great at medium to low speeds and be very compact, saving on reducing the amount of roller or belt conveyors needed, and in some cases, can replace a shoe sorter.
This type of sorter is flexible with integration and used frequently in packaging processes. However, being a plastic system, heavier-weight items and parts without an even flat bottom should not be used with an ARB.
Improve Warehouse Efficiency with Sortation Systems
Sortation systems reduce or eliminate labor needs to keep a warehouse running efficiently. The future of warehouse automation involves both sortation and a well-run conveyor system, as well as other automation technology, such as AMR and ASRS, and robots.
Sortation and conveyor systems can include slow, medium, and high-speed systems to move and sort packages. Diverter sections often require components such as aluminum extrusion, linear shafts & bushings, drive shafts, and more, which you can find at MISUMI.
If you’re looking for a manufacturing partner with experience and product knowledge in warehouse automation, MISUMI is your go-to for prototyping, product selection, and production needs.
