Vertical Package Transport: Incline Conveyors vs. Reciprocating Lifts vs. Spiral Conveyors
You can transport cartons vertically in a number of ways, each of which has its advantages
High-velocity order picking operations frequently need to transport cartons vertically–on and off mezzanines or pick modules, into workstations, onto work platforms, over traffic aisles or to merge with overhead conveyor lines. You can accomplish this with incline conveyors, vertical package lifts, spiral conveyors, automated package lifts and manual methods. Each method has its limitations and its advantages.
Automated package lifts: small footprint, economical
Above: video of continuous vertical package lift
Package lifts generally come in two configurations: reciprocating and continuous.
- Reciprocating lifts move carriers vertically, up and down. They stop, then change directions and can have multiple discharge/input points.
- Continuous lifts rotate package carriers uninterrupted on circular tracks and achieve higher throughput rates than reciprocating lifts. You can set them to C and Z rotations depending on your needs.
Throughput considerations
Automated package lifts are space efficient and can have higher throughput speeds. Reciprocating lifts can move up to 420 products an hour, while continuous lifts can handle 400 per hour in standard configurations and can be customized for speeds up to 2,000 products per hour.
Space efficiency
Package lifts have perhaps the smallest footprint of these alternatives. Reciprocating lifts occupy only 7.5 total square feet of floor space, while continuous lifts require 16 square feet–both less than spirals or inclines.
Above: package lifts used to create an underpass, where forklifts, people and other traffic can pass through safely.Â
Costs
Package lifts are more economical than spiral conveyors and costlier than incline conveyors. For the right applications, they are an economical package up/down movement solution.
Vertical package lifts: space efficiency and access from up to 3 sides
VRCs (vertical reciprocating conveyors) are usually associated with pallet handling but are also a solution for package conveyance between multiple levels.
Vertical package lift (VRC) factors
- Multiple packages can be conveyed at the same time on the VRC platform as it is relatively large.
- Vertical travel up to 60 feet per minute, with 400 feet per minute available in continuous cycles. This isn’t as much throughput as some of the other methods available but works for the correct kind of packages in the right application.
- You can access cartons from three sides of the lift. This means that three different conveyor lines or people can work on them when they reach their destination.
- VRCs are more space efficient than incline or spiral conveyors, with a 3′ x 3′ compact footprint.
- Easily integrates with conveyor systems for automated vertical movement, infeed or takeaway.
Spiral conveyors: high-density, high-throughput
Spiral conveyors are a high-density and high-throughput package elevation alternative. If your application needs to convey and hold packages onto or away from an overhead platform, they’re ideal. They are a relatively expensive method, so be sure you need the density and capacity.
Versatility
Spirals can accommodate a variety of different package sizes on the same conveyor line. They come in a variety of widths to match infeed and takeaway conveyor lines so you’ll be able to transport almost any carton you can convey with them. Many types of spirals are reversible, which adds versatility for picking and in-process buffer applications. Spirals work well in retrofit situations due to their vertical profile and modular design.
They frequently serve as work-in-process buffers to hold product in place as they await sortation, packaging or machine integrations.
Cost factors
Spirals’ adaptability and modularity mean higher acquisition costs than many vertical transport alternatives. They’re worth it when you need their combination of flexibility, density and speed.
Speed: the fastest method
They’re fast. Spiral conveyors give you constant product flow and the best possible throughput. This is why they’re frequently installed into pick modules and high-velocity distribution applications. For fast-moving order-picking operations, speed is critical. Standard spiral conveyors operate at speeds up to 200 feet per minute, completely full of packages.
Read more: Vertical Spiral Accumulation Buffers
Incline conveyors: economical, consistent throughput
Incline conveyors are made to stream packages from floor levels to an upper level–an overhead conveyor line, a mezzanine, pick module or work platform in a configuration similar to an automated ramp. They work well for all types of product flow applications with strong throughout and demand for continuous flow. They aren’t terribly space-efficient, as they require the physical space to incline or decline between levels.
- While they don’t serve as carton buffers as well as spiral conveyors, inclines are capable of holding a significant volume.
- Throughput is a strength. Incline conveyors can continuously flow packages at speed up or down in a safe manner.
- Inclines are economical, and feature a relatively quick install time. They typically bridge only between two levels, where spirals, package lifts and VRCs can be built in multilevel configurations.
You can use inclined conveyors to create overpasses for personnel and equipment passage. Floor-installed conveyor systems can incline up over an aisleway, cross it, then decline down on the other side to allow passage. This lets you move cartons overhead without interrupting the flow of traffic or the conveyor system. Spirals aren’t useful for this type of application, but inclines are ideal. Vertical package lifts (see above) can also function to build system underpasses.
Read more:Vertical Pallet Movement Options
Finding a balance: space, time, cost, density and product flow
When you’re designing a material handling system, density vs. product flow vs. the space vs. the time vs. the costs must be balanced. Each of these vertical transport solutions has its advantages and has its limitations. The answer is often a blend of options that takes into account the balance between these factors. Some places in a plant might be starved for workspace, while others need more storage and a buffer between processes. We’ll help you design a system that works for you.
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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.