Which Carton Flow Type Fits Your Application?
Skatewheel, roller track, wheel bed, shelves--which do you need?
Carton flow expedites pick operations by making stock accessible in an easily replenished first-in/first-out pattern. Gravity flow racks can reduce labor costs up to 75% in pick operations compared to static storage picking by delivering cartons and split case goods to the pick aisle rather pickers pulling from the static pallet rack storage. It is a commonly used storage/picking method in many operations, but there are many options and types of flow storage available. Which fits your need best?
Matching gravity flow features to applications
There are many different types of gravity carton flow – roller track feed, skate wheel bed lane-less, flow shelves and rail flow. Distinguishing the advantages and characteristics of each will help in finding the right solution for your needs. Additionally, understanding the structure and makeup of each will assist you in determining how best to locate and setup your carton flow systems.
Characteristics common to all gravity flow systems:
- Flow levels that have a slight incline to deliver product to the pick location
- Choices in setup as full-width, single & multiple-track partial width within pallet rack
- Simultaneously replenishment from the rear as pick operations continue on the pick face
- Availability in modular structures (some with cart wheels) that allow quick assembly and flexible location selection
- First-in/first-out traffic that keeps time on the shelf to a minimum
- The ability to maximize slotting efficiency of fast and slow movers
- Relying on gravity feed; it is non-powered, low/no maintenance
- Suitability for a variety of applications including distribution centers for carton goods to single pick operations for small parts, pharmaceuticals, electrical and computer components, assembly or maintenance, and more.
Define your needs
There are some key questions to ask about your particular operation in order to determine which gravity carton flow system to select.
- Do you re-slot frequently?
- Do your products have a consistent size or do they vary in size?
- Will your pick operations be in a permanent or temporary location with flow tracks being used in other locations?
- Does your business have seasonal peaks in volume?
- How much control do you have over the package sizes in your inventory?
The answers to these questions will provide you the information you need for finding a matching gravity carton flow solution.
Types of gravity carton flow and applications
Roller flow tracks are added to pallet rack bays or integrated into specialized racks. These full width rollers come in typical configurations of 6″, 9″, 12″, 15″, 18″ widths, with rollers on 1, 2, or 3″ centers. It’s important to understand that the roller centers help you with loads of various sizes and weights. Like plastic wheel lanes, loads are slotted into a one-per-lane configuration. These tracks come in low profile, high profile, and deck configurations. Low profile tracks nest between single or double deep rack beams to maximize vertical space for higher density live flow storage. High profile tracks install on top of pallet rack beams. They can overhang the front or back to maximize linear front-to-back space usage on single or double deep racks. Deck tracks drop directly into single-deep pallet rack beams without any additional connectors.
- Roller track lanes fill full width of bay
- Creates flow lanes within each level
- May be inserted into existing pallet rack, or pre-configured rack units
- Can be combined with pick trays or tote and conveyor systems
- Flow control and stop options at discharge points
- Special hangers used to connect roller tracks to step and structural rack beams
These racks can be specified with either steel skatewheel conveyors or black poly skatewheels. The key thing is that they don’t restrict your loads to lanes. Products of various sizes can be stored on the flow levels at various times to suit your needs. This provides more flexibility than either plastic wheel or roller options, but adds expense. These types or rack may not be suited to very regimented, static loads that do not change over time and do not require the level of flexibility they deliver.
- Lane-less flow allows maximum SKU storage
- Spans full width and depth of rack levels
- Flow control and stop options at discharge points
- Lane guides may be added to direct flow for some products
- May be inserted into existing pallet rack or pre-configured units
Inclined solid shelves allow product to slide forward to the pick face. For operations that do not require the depth of a true carton flow/roller solution, but need some first in, first out, flow storage functionality, these shelves are ideal. They do not run to the depths that flow solutions do, but are excellent for loads that easily slide without rollers, or to keep bins of product or components handy for pickers or assembly personnel. These shelves may be a very strong solution for slower moving items that do not warrant true carton flow.
- Holds columns of totes, bins, or cartons in dense storage
- A variety of carton/package sizes may occupy space on same shelf
- Integrate into pallet rack or modular rack units
- Inventory slots are easily adjusted or changed
- Mobile units allow relocation to other work stations/locations
Use plastic rails for consistent carton sizes; easy to adjust when new carton sizes are added. These systems tend to be less expensive than full width rollers, but have some issues with product tracking and additional maintenance
due to wheel failure.
- Consists of rails one wheel wide with wheels on specific centers based on size of containers flowed
- Rails are set up to match span of container bottom, 2-3 rails per lane
- Lane guides can be added to prevent containers from dropping off rails
- Easy to setup in pallet rack, easily reconfigured or moved
- FIFO flow relies on gravity feed; non-powered, low/no maintenance
It’s all in the size, weight, and your organizational style
Carton flow reduces foot travel, allows simultaneous restock and picking, increases pick rates, and works for both case and split case picking – all depending on the size of the product being picked, its weight and
application. Ask yourself the questions above, then consider capacities, carton size and weight, and how you want your flow system to deliver goods to the pick face. Don’t forget temporary options like single or multiple tracks of flow in partial width pick levels. Anytime you can save time and steps by flowing goods to a location, it’s probably a more efficient way of doing business.
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.