Vertical Lift Modules Carousels

Thinking of making the leap into automated storage?

With either a vertical storage carousels or vertical lift modules (VLM)? Good news —your storage situation will be looking up.

Only now you have the daunting task of choosing which one of these technologies to invest in, install and use daily. No need to gaze to the heavens for divine intervention to help you decide, however.

I am here to help you understand the differences between the two technologies
as the first part of making your decision.

What are the benefits of vertical carousels and vertical lift modules?

As two types of goods-to-person automated storage and retrieval machines, vertical carousels and VLMs both offer:

  •   – High-density storage of slow- to medium-velocity items.  A 6-meter-high machine can provide anywhere from 5,000 to 7,000 locations (each roughly 6” x 6” x 4”).
  •   – Automatic delivery of required items to a waist-high window for ergonomic, high-throughput picking in just a few steps.
  •   – Full enclosures and lockable access for security.
  •   – Maximized storage in a compact footprint by leveraging a facility’s overhead space.

How do they store items?

Vertical Carousels are built with a series of carriers attached in fixed locations to a chain drive.
Movement is powered by a motor, which sends the carriers in a vertical loop around a track in both forward and reverse directions—like a Ferris wheel.

Vertical Lift Modules consist of two columns of trays with a mechanical inserter/extractor positioned in the centre.
The inserter/extractor travels up and down between the stored trays, automatically locating and retrieving them as needed – like an elevator with doors that open on both the front and rear.

How do they measure up?


Both technologies span roughly the same range of widths, not much of a differentiator there.
When it comes to depths:
Vertical lift modules can be about twice as deep as vertical carousels – giving vertical carousels an overall narrower footprint. For specifics, let us breakdown all the numbers for each technology.

A standard VLM unit is roughly 1.5 meters – 7 meters wide by 2.4 meters to 4 meters deep. The trays that store a max product height of just over 70mm.
(Think ergonomics:
You do not want the trays to be too deep or the operator will not be able to reach items with minimal effort.)

, Vertical Lift Modules Carousels

Example image of a Vertical Lift Module (VLM)

In comparison, vertical storage carousels range from 1.8 to 3.5 meters wide by 1.2 to just over 3 meters deep.
Designed for smaller product sizes, the carriers’ heights range from:
100mm that store the inventory measure from small triple carriers, to double carriers and finally bulk carriers which can be 620mm.

, Vertical Lift Modules Carousels

Example Image of a Vertical Storage Carousel system


VLMs start at 2.8 Meters and can be installed up to 15 meters high. In contrast, carousels start a little shorter, at just 2.6 meters, and can reach up to 15 meters.

Although both machines can reach straight up to your ceiling, it doesn’t mean they always should. Often, the taller the machine, the slower the throughput. 
So it’s really up to you to determine the machine height that gives you the perfect mix of space savings and throughput. (Do not worry; you’re not on your own. There are plenty of experts in the material handling field that can help you figure out the throughput rates of different-sized machines.)

Load Capacities

The latest vertical carousels handle up to 500kg per carrier. Vertical lift modules can be outfitted with trays that handle up to 1kg; for applications with heavier loads, lift-assist equipment can be added to a VLM.
This is a major difference between the two machines:
Vertical carousels are more difficult to fit with ergonomic lifts and cranes – so if it is heavy loads, you are looking to store the VLM if probably the choice for you.

How fast are they?

As you have probably heard by now.
Like any automated system throughput rates in vertical carousels and vertical lift modules are application dependent.
Depending on an individual machine’s configuration (mostly unit height), customer’s order profile (single line vs multi), single order or batch picking, etc.

Both units can perform at similar throughput rates
(vertical carousels can reach up to 400 items per hour while VLMs—depending on configuration—can deliver throughput up to 350 items per hour.)

iRide pick assist

To reach those top throughput speeds, both types of machines need to be outfitted with pick assist such as iRide on Icam Silo technology.
Located within the access window
These devices illuminate to show the operator where within the tray or carrier the required item is stored to eliminate search time.

, Vertical Lift Modules Carousels

Example image of IRide pick assist

So now you’ve learned about the physical differences between Vertical Lift Modules & Vertical Storage Carousels .Now, it is time to figure out which one is right for your operation and your stored items.

Product mix…

The size and weight of the items you plan to store in the machine
How frequently your mix of products changes—are the key deciding factors when picking between a VLM and a vertical carousel. That is because each system stores items differently.

More sophisticated than vertical carousels, Vertical Lift Modules use a height sensor that measures how tall the items placed in each storage tray are every time it has put away.
Integrated software crunches those numbers, then directs the VLM to store the trays dynamically—as close as one inch apart—to maximize storage density.

For example, if the tallest item you place on a tray measures 600mm tall,

The Vertical Lift Modules will store it in a 700mm space inside the machine.
If that product is picked and the next tallest product remaining in the tray measures 35mm tall
The VLM will automatically place the tray in a 40mm tall location. The machine prioritizes compressed storage to give you the highest storage density possible.

Conversely, in vertical carousels, the carriers are spaced evenly in fixed positions.
The shelf levels within the carrier can be adjusted up or down to compress the vertical space – but not automatically, adjustment is a manual task.
Because nobody wants to pay to inventory air, it is critical to know the heights of your stored items when specifying the machine to get those shelves as close together as possible.
That makes vertical carousels an ideal choice to store products that are similar in height (usually under 600mm), and whose sizes do not often change.

That said, every carrier in a vertical carousel can be subdivided further (both vertically and horizontally) to maximize storage density within the unit. In fact, they are frequently divided into two or three shelves to separate items for slotting and organization.  Adjusting those dividers—while possible to do—is a tedious task that requires all the product to be removed first, then the dividers unbolted, moved, and re-attached in a new position.

While it is not a big deal to change one carrier, if inventory changes frequently enough that a new carrier configuration is required often
A lot of labour hours will be spent to maximize the machine’s storage density. That is why vertical carousels are a great choice if your product mix is consistent in size.

, Vertical Lift Modules Carousels

So, which one do you need?

Because of their construction, operation and product handling differences, vertical carousels and VLMs are ideal for different applications. When you are deciding which system is right for you, keep the following in mind…
Vertical Carousels work best in situations with:

  •   – Ceiling heights under 8 Meters
  •   – Stored parts sharing relatively similar dimensions
  •   – Items that can be hand-picked without lift assistance

Vertical Lift Modules work best in situations with:

  •   – Ceiling heights up to 15 Meters
  •   – Highly variable sizes and weights of stored parts
  •   – Frequently changing inventory mix
  •   – Heavy items that require lifting assistance for the operator to safely handle

In conclusion…

While determining the material handling technology you need is not exactly rocket science, it is science. Would you re-side your house without asking the advice of a specialist – I would not.
So do not hesitate to ask questions and engage a material handling expert in your quest
We have people who have been doing this work for over 30 years (wow that’s commitment!). They know a thing or two about what you are looking to accomplish, and we are here to help.

Need more insight into whether a vertical lift module or vertical carousel is right for your operation?

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