Push-back racking has lately grown quickly in popularity, because it provides comparable space savings as drive-in, with 3 to 5 times more selectivity. Marketing trends like fast increases in the amount of SKUs, mass customization, and faster product obsolescence have prompted this development. Every level in a push back scheme contains a sequence of nested rolling carts working in a lane that slopes upward away from the pick side.
The first pallet loaded in the lane must be loaded onto the top cart to load the lane. Then, to load the next pallet in the lane, the lift truck driver lines up in front of the first pallet and pushes against it, forcing the first pallet to slide back away from the pick side and revealing the next cart, which can be moved onto the second pallet once it is in place. Just repeat the process until the lane is full. To empty the lane, the operator removes the last pallet, and the others will roll back down to the pick side. The process is the same until the lane is empty. 
Key Benefits:
- High densities – three and four deep systems are common, which allows blocks of 6 or 8 deep, with back to back rows. Depths of up to 6 deep are also available, at higher costs.
- Improved selectivity over Drive-In, which Push-Back often replaces.
- Efficiency vs. Drive-In – trucks do not need to drive into rack loads come to them at the pick face.
- Less rack. Truck and product damage vs. Drive-In- with no trucks driving inside rack.
Advantages:
Over Single Selective Racking
- In a typical three deep, back to back Push Back system, space savings would amount to around 40% vs. Single Selective Rack.
- Converting an existing space from Single Selective to Push Back would accommodate an increase of about 60% in pallets stored.
- Over-head Push-Back (loaded and unloaded from replenishment aisle in rear) ensures optimal use of vertical space above floor level Pallet Flow picking system.
Comments:
There are a number of particular factors to satisfy before making a push-back purchase:
- Carts should be linked to avoid “runaway carts”.
- Pallet quality must be considered.
- Slope is critical for both safety and operating performance.
- The system must be designed for dynamic loads – in simple terms, that means it needs to be more robust than if pallets were static. This also means that Push-Back requires more complex engineering. One sub-standard component, and your system may not flow! Unfortunately, we’ve seen customers victimized this way.
- “Vertical Profile” of the nested carts may be critical, if there is a height restriction in the building.
- Push-Back systems are starting to be misapplied, the same as Drive-In systems once were. You need to make sure that you are storing the right cross-section of your SKU’s in Push-Back systems.