Every pallet ASRS project eventually reaches the same discussion.

"We need higher throughput."

The first reaction is usually predictable.

Increase the Stacker Crane speed or add another aisle.

On paper, these seem like reasonable solutions. In practice, they often solve the wrong problem.

After working on manufacturing warehouse projects over the years, we've found that throughput limitations rarely come from a single piece of equipment. More often, they come from how the entire material flow is designed.

Before deciding how many stacker cranes a warehouse needs, there is a more important question:

Where is the real bottleneck?

Finding the answer to that question usually changes the entire ASRS layout.

Throughput Is a System Problem

When customers evaluate pallet ASRS solutions, many naturally compare Stacker Crane specifications—travel speed, lifting speed, security, or positioning accuracy.

Those parameters matter.

But they do not determine the warehouse throughput by themselves.

A pallet movement is completed only when every step finishes successfully:

• the Stacker Crane retrieves the pallet;
• the pallet reaches the conveyor interface;
• the front-end transfer system accepts it;
• the material arrives at the production or shipping point.

If one of these steps slows down, the entire system slows down.

We've also seen projects where increasing crane speed produced almost no improvement because the real limitation was the front-end transport system.

This is why throughput should always be evaluated as a complete material flow rather than an equipment specification.

A Project That Challenged Our First Assumption

Hanbell presented exactly this type of problem.

The pallet warehouse had to be built between existing factory buildings, leaving space for only two Stacker Crane aisles.

At the same time, the warehouse needed to support material supply for both the first and second production floors.

Every working day, approximately 1,578 pallet movements had to be completed within an eight-hour production schedule.

The obvious question was:

Should we add more aisles?

The building made that impossible.

The second question was:

Should we simply use faster Stacker Cranes?

Cycle-time analysis suggested the improvement would be limited. Horizontal travel is only one part of a storage cycle. Lifting, positioning, fork movement, waiting for downstream equipment, and task sequencing still consume time.

Improving one motion could not solve the whole process.

So instead of asking how to make one crane faster, we changed the planning objective.

How can one aisle complete more useful work during the production window?

Improving Throughput Without Expanding the Warehouse

The final solution used four Stacker Cranes operating on two aisles, allowing two cranes to share each rail.

That decision alone did not increase throughput.

Without proper scheduling, two cranes in one aisle would simply spend more time waiting for each other.

The real solution was changing how work was distributed.

During normal production, each crane is assigned its own operating zone through WCS scheduling. Storage and retrieval tasks are processed in parallel while maintaining safe operating distances.

Inventory that needs to move between the two operating zones is scheduled during lower-load periods whenever possible, preventing relocation tasks from competing with production supply.

In other words, the design increased task concurrency, not simply equipment quantity.

That distinction is important.

More machines do not automatically create more throughput.

Better task organization often does.

Then We Looked Beyond the Rack

At this stage, many projects make another mistake.

Once storage and retrieval capacity increases, the bottleneck often moves somewhere else.

For Hanbell, that next bottleneck was the warehouse front end.

The ASRS was not only storing pallets.

It also needed to supply two production floors continuously.

To support that flow, DELIECN designed a two-level steel platform connecting the warehouse directly with the customer's factory.

Materials no longer needed unnecessary intermediate transfers between floors.

At the same time, the front-end logistics system was designed around the same throughput target.

Instead of asking stacker cranes to complete every transport task, pallet circulation outside the rack was handled by:

• four single-station RGVs;
• one dual-station RGV;
• multiple conveyor lines.

Each system performs the task it is best suited for.

The stacker cranes handle in-rack pallet movement, including storage and retrieval operations.
The RGVs connect the AS/RS with production areas, transferring pallets from the warehouse to production lines.
The conveyor systems link different production processes, ensuring continuous and efficient material flow.

Only when these systems are balanced can the warehouse actually deliver 1,578 pallet movements per day.

The Number That Really Matters

The Hanbell warehouse contains:

• 4 stacker cranes
• 2,872 pallet locations
• 5 RGV systems
• 12 storage levels

Those numbers describe the project.

They do not explain it.

The number that explains the entire design is still:

1,578 pallet movements in eight working hours.

Everything else—the dual-crane configuration, the two-level connection, the RGV layout, and the conveyor system—exists to support that operational requirement.

Without understanding that requirement, copying the equipment configuration would make little sense.

Three Questions Worth Asking Before Expanding Your ASRS

If you are planning a pallet ASRS today, these questions may be more valuable than comparing stacker crane specifications.

Is the bottleneck really inside the storage aisle, or has it already moved to the front-end logistics system?

Would adding another aisle increase useful throughput, or simply move congestion to another location?

Is your warehouse designed around storage capacity, or around the production rhythm it needs to support?

These questions rarely appear on equipment datasheets.

Yet they often determine whether an automated warehouse performs well after commissioning.

What This Project Changed for Us

The Hanbell project did not convince us that every pallet ASRS should use dual stacker cranes.

It reinforced something far more important.

Warehouse throughput is determined by the slowest part of the material flow—not by the fastest machine inside the warehouse.

Every project has a bottleneck.

The challenge is not buying more equipment.

The challenge is identifying the right bottleneck before the warehouse is built.

That is where good ASRS planning creates its greatest value.