Options for Pick Modules and Empty Carton Transport
What works to stock your pick module with cartons for pick & pass systems?
Order Fulfillment System Inquiry
Pick modules are commonly used in distribution operations when companies need to build high-density, high-throughput order fulfillment operations. This typically involves a multi-level platform system integrated with vertical storage options to move finished orders on and off platform levels toward other warehouse destinations.
One overlooked aspect is the addition or removal of empty cartons to picking positions. What are your options?
Pick modules are high-density, but require inputs
When orders are picked on multilevel systems, those systems must be stocked with product and materials. Inventories must be stored elsewhere in the facility and then transported to the pick module for replenishment. For rack-supported systems, that can involve a forklift feeding pallets to aisle-facing positions. Other methods become increasingly efficient for larger pick modules that lack forklift access at scale. Those inputs may include:
- Inventory for replenishment
- Full and partial cases
- Picking materials, such as cartons or void filling materials
- Tools or other needed inputs to the process.
The options for vertical transport often focus on finished picks, not picks in process. We’re covering empty carton transport options in this article. Previously we covered the removal of those cartons once they’re expended.
Read more: The Anatomy of a Pick Module
Options for pick module carton supply
#1: Store flattened corrugate at the ends of the pick module
With this strategy, you use forklifts to load pallets onto your pick module in an out-of-the-way area like the end of the platform.
- If there is a reserve storage area nearby, workers can stock it from these bulk deliveries.
- Once the pallets are on the platform, they can be broken down and distributed to picking, packing or assembly functions from this centralized source.
- This tends to involve people walking to retrieve flat cartons and other supplies.
Flat corrugate must be stored elsewhere in the warehouse, then transported to each level of the pick module using forklifts. This causes “deadheading” as forklifts bring over flat corrugate and load it to different levels. You can only load one level at a time.
Wasted motion: Also causes more “deadheading”, in the form of wasted associate movement to walk over and bring corrugate, and then erect and tape the boxes. Using pickers to build cartons means that if you are picking a thousand orders a day, your pickers are building a thousand cartons. They unfold, tape and then use them. Even if each carton takes only 45 seconds to build, that is a significant time sink over a large system. You must also deal with poorly-taped, poorly build cartons.
If the pick module is more than two levels high, you may need specialized forklifts to service it in some cases. If your production forklifts are working on tall racks this may not be an issue, but it’s a factor to consider. If your platform is served by a vertical conveyor lift, you can send up supplies that way as well, but those would still require distribution to pick locations.
You’ll need to implement safety processes, such as pick module and mezzanine fall prevention gates where the pick module edge is left open.
Read more: How to Choose the Right Pallet Drop Gate
The problem
This is a slower, manual method that requires significant transit and manual handling time, both on the floor and on pick module levels.
When it works
This method works best for lower-throughput operations that don’t require higher order fulfillment. This may work in tandem with your inventory replenishment system, if you’re loading stock this way during non-shift hours.
#2: Induct pre-built cartons into your pick module with belt or roller conveyors
You can use the same pick & pass conveyor system that takes cartons away from pick locations to stock those locations.
Inducting cartons
Induct your pre-built cartons into the pick module using the takeaway conveyor system, and then routing them to needed zones using pick-and-pass/zone-routing technology.
- Using this process, you eliminate carton erection by pickers because they pre-built boxes from the conveyor
- Transporting empty cartons on an MDR can cause damage during conveyance or transfers, as it is more difficult to keep the empty cartons aligned.
- Lack of alignment and resulting carton damage can create challenges for accurate label reading, resulting in misrouting of cartons downstream.
The problem
This method occupies some of the conveyor capacity for empty carton induction. When empty cartons need to be presented to higher levels of the pick module, they may need to share the line with filled orders, which may result in reduced picking capacity and congestion. Damage to light, empty, erected cartons can be a problem since they will share the line with full, heavy cartons that can impact them.
When it works
This can be designed around for the right system with the correct throughput rates. Well-designed applications can reduce conveyor line congestion to make this method efficient. If empty and full cartons are intelligently routed, they can co-exist on conveyor lines. The caveat is reduced throughput and buffering of loaded orders on the system. If you can restock all picking positions during off-hours, this method is less manual and requires no hardware investment.
#3:Use overhead (monorail) conveyor to deliver cartons
By using overhead conveyors, you’re providing cartons to pickers in real time at ergonomic heights. Your takeaway system is still MDR flat conveyors, which aren’t impeded by the overhead line at all, and don’t need to share it for carton replenishment. This method, like flat belt conveyors, eliminates operator walking and maximizes picking time.
The problem:
This system combines the efficiency of a flat-belt conveyor delivery, but occupies vertical space. This means you will need overhead space on any levels of the pick module it serves for the overhead system equal to the ceiling space plus the hang height for carriers and cartons.
When it works:
If you have, or can design the needed overhead space, monorail overhead systems give you the best of both worlds.
- They deliver cartons in real time to pickers without sharing the line with completed or ongoing orders.
- They avoid the damage that can happen when empty cartons share a line with full ones.
- Cartons are always presented to pickers in the same orientation, provided they are loaded correctly (no misalignment during conveyance).
- Like flat conveyors, it removes the need for pickers to fold and tape cartons, or leave their stations to acquire them.
Critically, this method results in making the takeaway conveyor system fully dedicated for filled and partially filled cartons.
Decoupling your order fulfillment line from carton delivery, maximizes the number of orders you can process and may end up being the highest-throughput method available, since you can run your fulfillment/picking lines at the maximum speed possible for your picking system.
The method you should use depends on volume, space and your goals
Do you need continuous access to flat cartons throughout the day for a high-volume, fast throughput operation? If so a continuous method like overhead conveyors may be the best option. If you can load less frequently, a forklift loaded system may work better and require less investment. If you have existing pallet elevation systems (like vertical conveyors), then you can utilize that, if it can meet your throughput needs.
Finding the right solution means analysis and understanding of volumes, space and time constraints. Do this work as early in the process as you can to make the right decision.
More resources
- Warehouse Productivity: Prove, Improve it – Cisco-Eagle blog
- Overhead Conveyor Performs Double Duty – Pacline
- Vertical Pallet Movement Options – Cisco-Eagle blog
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Tags: conveyors, Mezzanines, pick modules, Vertical Storage
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.