Vertical lift modules (VLMs) and vertical carousels (VCs) are both system-controlled, automated storage and retrieval systems (ASRS) that occupy small foot print by taking advantage of the vertical storage technologies to make the best use of the vertical space in warehouse.
With either vertical storage solutions, companies can increase warehouse productivity significantly, simply by eliminating unnecessary walking, searching, and climbing.
Although both dense inventory storage solutions in manufacturing and warehousing applications are very helpful, but storage systems function in different ways.
A vertical carousel storage system stores parts on trays or carriers affixed to a chain that rotates all the way, like a Ferris wheel. While vertical lift module moves each tray independently, with a lifting cart in the center, more like a vending machine.
In the past, the only vertical storage solution in the market was the carousel storage system.
Due to the lack of flexibility and limited configurations options, vertical carousels were misused or configured incorrectly in many applications.
The introduction of the vertical lift module about 37 years ago started to change the situation.
Thanks to the large number of configuration combinations and advanced technology, the vertical lift module (VLM) offers a very flexible and convenient solution allows operations to modify or grow, and it is easy to install. Customers no longer need to worry about the decisions they made today might fail to work in the future. Because of teasy configurability and scalability, VLMs can grow with companies as business strategies develop with emerging market trends and technologies.
9 Disadvantages Of The Vertical Carousel
The vertical carousel (VC), also described as a storage carousel or vertical rotating shelf system, has many disadvantages when compared to the Vertical Lift Module.
1. Limited Depth of the vertical carousel storage system
The vertical carousels come in different sizes in terms of width and height. However, when it comes to depth, a vertical carousel only offers 1.5 m at the most.
- But a vertical lift module can go more than two times deeper than carousel storage, offering a much bigger inventory space.
For applications with limited space, choose compact vertical warehouse solution, it offers all the benefits of normal size vertical lift module, but could install in the same footprint as a vertical carousel system, such as the Modula Slim, one of the most compact VLMs on the market, Modula Slim has almost twice the load capacity (25,000 kg )of a typical vertical carousel, without any unbalancing issues.
2. Imbalanced Load Restrictions of Carousel Storage
A vertical carousel consists of shelves or carriers connected in a chain that rotates vertically and delivers the goods to be picked to the operator. The movement is like a Ferris wheel. As the carriers are connected in a fixed order, the entire carousel system needs to rotate for each picking or replenishment, often causes imbalance problems.
To avoid load imbalances, Items store inside should have identical weights and similar sizes to optimise the storage space since the tray positions can’t be changed.
Vertical carousels also have height limitations, due to load balance issues.
Based on the model, there are different restrictions on weight ranges. If load with any substantial height, lighter duty, or a few empty carries in a row, could easily cause imbalanced conditions. Machine works under this condition, over time, creates a lot of stress on critical components in the unit, requiring regular maintenance or worse, premature failure of critical wear items.
If the unit reaches an imbalanced state, the motor can overload, and the carousel could shut down completely until the unbalance is corrected. Sometime the motor might struggle to get the carriers through the curve of the unit. A carousel with an odd number of carriers will experience these issues even more.
- There are no load imbalance issues with the VLM.
Vertical lift modules are composed with two tray towers — one in front and one in the back — along with a central elevator. Once the operator calls the item to pick, the elevator extracts and presents only the tray with the required item, quickly, efficiently, and with picking bay an ergonomic height for the operator.
The trays are built to accommodate heavy loads (up to 990 kg per tray) without strain or imbalance issues.
Vertical lift modules can reach up to 16.1 m or more (please consult us for other heights) and contain trays locate at different heights, no space is wasted. For example, small items can be stored in one tray, while larger items can be stored in another tray. All of them could store in the same VLM.
The modular design of the VLM ensures almost unlimited flexibility. The height can be modified and adjusted to optimise the ceiling height by adding or removing modules.
If you need to move to different locations, the VLM can be disassembled and install quickly to adapt to the new height requirements.
A vertical lift module can be easily integrated with additional lifting equipment and can be configured with a tray removal cart.
3. Fixed Height Restrictions (pitch)
Again, because the carousel storage system is a closed-loop system with all carriers being tied together, there is no chance to adjust heights above the max height chosen at the beginning of the project. This is called the pitch of the carrier.
A carousel with a 12 pitch has a clear height of approx. 27cm. This means that the tallest product that can ever be put into the system is 27cm. You can add additional shelf levels to divide the 27cm up into smaller levels, but you can never go taller. Thus would require a new unit. For this reason, there is no room for mistake when designing the system and no modification flexibility for future product or process changes.
- The VLM offers dynamic storage locations and flexible configurations. The VLM has dynamic storage locations that could change with the size of the product being placed into the tray. These heights range has no limitation within the height of your picking bay.
- Vertical lift modules can easily accommodate items of different sizes and weights. Trays can be organised for all types and sizes of stored item. Thanks to partitions and dividers, companies can create the exact number of storage locations they need, and their configurations can be adjusted any time to accommodate changes in the size or quantity of stored items or seasonal peak.
A height-detection system determines the vertical dimensions of items as the tray is put in, it calculates adjustments in real-time to maximise storage density within the unit.
The VLM has dynamic storage locations that change with the size of the product being placed into the tray.
4. Product Movement in the Carousel Storage System
Due to the carousel’s rotating retrieval method and the fixed locations, every carrier must move in order to get the required product to the access window. This means that all products need to travel during every transaction. It may not be good for some products, especially for fragile or sensitive products, continuous movement could damage them.
- The VLM only moves the required tray, one at a time, to the picking bay for picking. This eliminates unnecessary product movement and reduces the risk of damages to the product.
5. Front Picking Restriction
Because the Vertical carousel storage system is a closed loop system and there is always another carrier directly above it, the product must be picked from the front, not from the top. This means that you must reach into the face of the carrier to pick up parts.
It restricts not only the visibility of the products but picking efficiency. Top picking in a carousel is only possible using totes or boxes that can be pulled out of the carrier, thus will expose the entire box of products to outside environment. And after picking, you will need to put it back. This adds unnecessary steps to the picking process.
- The VLM always provides top picking, making all products easy to see and access. There are no additional movements added to the pick cycle. The selected tray is brought into the picking bay, where it is 100% visible and accessible for operators.
6. Security Issues with Vertical Carousel System
The vertical carousel rotates all carriers to pass the picking window in order to get to the required storage location. This makes all products accessible to operators, not easy to guarantee products safety. Any carrier can be stopped at the picking window along the way, it is easy for operators to pick the wrong part or a part they like.
- Because the VLM only delivers one tray at a time, the rest of trays are kept secure inside the VLM. Only the required product is brought to the picking bay, making it possible to restrict access to other products if necessary. The vertical lift module can also be equipped with several safety aids options, such as EKS or RFID readers. Thanks to the automatic door, the materials stored are kept inaccessible when the machine is off or unattended.
EKS or RFID readers Badge readers Automatic Closing door
7. Dual Access
Dual access functionality for a vertical carousel is much different than with the vertical lift module. Because the VC system of carriers is tied together in one chain, it is not possible to work at two access windows at one time, orders need to fulfill one after another.
Again, this is because if one carrier needed, all carries should move. Also, it is not possible to get various combinations of carriers to appear at each corresponding access window at any given time. Some systems even require that the door of the opposite opening be closed while the other opening is working. If this is true, if one side couldn’t close the door, the other side will be shut down.
- The VLM has the ability to work from both picking bays simultaneously. This means once one tray is delivered to picking bay, it can continue to deliver (or remove) another one from another picking bay. Workers are free to work on their respective trays at any time while they are at the picking bay position. This creates a more productive environment for both picking and replenishment, as replenishment can be done during the picking cycle without interrupting each other.
- The vertical lift module can also across different floors, with picking bays on the front and rear, allowing operations on multiple floors simultaneously. The units can also be installed outside of the building to further recover storage space.
Vertical Lift Modules -Internal and external bay, opposite bays, bays on different floors
8. Less Efficiency and Speed in Picking with the carousel storage system
Both in picking and replenishment operations, vertical carousels tend to be slower and less efficient.
When users need to pick an item, they need to wait for the entire set of carriers to move before accessing to the needed part.
During loading operations, due to the unbalancing risks, items and carts need to be loaded with careful consideration. Once items are placed into a carrier, the carousel needs to rotate 180 degrees, to ensure that the loads are evenly distributed.
Based on retrieval methods, the picking speed and efficiency of a VC are quite limited.
- Vertical lift modules can save you time in picking since you don’t need to wait for the entire set of trays to move – just the tray contains items to be picked.
- In addition, the machine can be equipped with a dual delivery bay to further enhance the picking efficiency. While the operator is working one tray, the elevator is retrieving and staging the second tray in the queue, reducing waiting time and speeding up the picking process.
And there is a list of visual aids that they can provide (for example, laser pointers to indicate where the needed item is located), vertical lift modules provide faster and more accurate retrieval for your operators. Modula Lift Modules offer picking speeds of 300 lines per hour or more.
9. Installation process and time
One of the major problems with vertical storage carousels is getting the carousel into the facility, as they are pre – installed as one unit and can’t be installed in sections.
A VC will usually take up to four days for installation.
- Vertical lift modules come in separate pieces that can be easily transported, and it is possible to install a VLM within two days. The maintenance processing also tends to be faster with VC, due to the most advanced technology these units are built on.
What Is the ROI for Vertical Carousels Storage system and Vertical Lift Modules?
The price of a new vertical carousel storage system and a vertical lift module is roughly the same.
But considering the previously mentioned disadvantages that come with a vertical carousel, you’ll see a quicker ROI with vertical lift modules.
Summary on Vertical Carousels and Vertical Lift Modules
Vertical carousels may have been in the market longer than vertical lift modules, but the advantages you can get from VLMs are clear. If you are considering an automated storage and retrieval system, it is important to carefully evaluate which system is right for your material handling needs.
At Modula, we offer two vertical lift modules:
- Modula Lift: Bestselling vertical lift module in the past 37 years, Modula Lift is available in a wide array of configurations, widely used by all businesses sectors to modernise their warehouse operations.
- Modula Slim: Most compact VLM in the market, This vertical lift module is designed to fit small spaces (about 3 square meters) with similar functionalities as Modula Lift.
The advantages of a vertical lift module include:
- Minimise footprint, saving valuable ground space while maximising storage potentials.
- High throughput rates
- High inventory accuracy to eliminate errors during picking and replenishment.
- Increased security while providing clean storage for your products.
- Modular design for future growth and adaptability
- Ergonomic pick height for all products and operators
- Ability to train workers in a few hours.
Ready To Start Your Automation Journey?
From analysis, configuration to implementation, Modula experts are ready to help you achieve your operation’s goals, boost your productivity through:
- Increase throughput
- Lower warehouse operation cost
- Eliminate residuals completely
- Reduce floor space waste
- Increase capacity
- Improve order accuracy
- Dramatically increase efficiency
- Reduce labor requirements and costs
