March 9, 2023
March 9, 2023

How Does Bin Digging Maximize Throughput?

AutoStore™ constantly adjusts Robot workflows through a process called Bin preparation or Bin digging, which is critical to ensuring maximum throughput for the more than 1,150 AutoStore systems running throughout the world. This article and animation explains how it all works.


AutoStore isn't magic

It's important to keep in mind that AutoStore isn't magic. It was inspired by a Rubik’s Cube. In 1996, Ingvar Hognaland had an idea to improve storage density: “Why store things like dominos, when we should store them like a Rubik’s Cube?” While you might not know how Rubik’s Cubes are solved, watching one go from mixed to solved can be mesmerizing. (Side note: I happen to love Rubik’s Cubes, my own parlor trick I can pull off in about 3 minutes.)

While a magician never reveals secrets, engineers like myself are more than willing to share scientific facts to help demystify the unexplainable or complex. Here are two facts I'm sure of: The solution to a Rubik’s Cube is merely a series of well-planned algorithms. Likewise, the "magic" of AutoStore isn't magic at all, but the logical result of arranging inventory in the world’s densest order fulfillment engine.

How does slotting affect warehouse efficiency?

Let’s talk about one of the worst jobs in warehouses – slotting. This hidden cost is pure “muda,” the Japanese term for waste. Using people to rearrange inventory only adds cost. Ironically, slotting used to be a way of reducing travel distances in a traditional setup. But in today’s fulfillment centers there are too many products to rearrange inventory with manual labor.

However, the performance of any inventory storage system, even manual, is a function of slotting. Even in traditional automated storage and retrieval systems (ASRS), popular items that sell frequently are stored at the front of aisles or outside of double- or triple-deep locations. But item usage is rarely predictable, never stable, and highly seasonal, so static slotting usually fails.

To sum it all up, slotting is essential but too cumbersome for people to undertake these days. E-commerce is expected to reach $7 trillion annually by 2025, making the pressure on warehouses beyond human capabilities.

That leaves the average warehouse operator in a conundrum, unless they have robots to do the heavy lifting.


What is natural slotting how is it beneficial to warehouse automation?

AutoStore completely eliminates manual slotting by embracing three key assumptions:

  1. Inventory isn’t static, it’s highly dynamic - constantly growing and changing.
  2. Order demand is the strongest predictor for which Bins are needed.
  3. New inventory is inherently popular and can be placed on top of older inventory.

AutoStore performance is unaffected by how much product volume is stored inside the Grid or how the individual SKUs are arranged. The system achieves high performance through what we call “natural slotting.”

Bins used are returned and stored at the top layer of the Grid. Over time, slower moving Bins descend to the bottom of stack. This design philosophy ensures that only on rare occasions will Robots have to dig to the bottom of a stack.

Everything is placed into inventory and perfectly arranged by Robots, eliminating costly “muda” from warehouses, and replacing it with a highly efficient automated system.

Slower moving Bins naturally descend to the bottom of the stack, whereas fast movers stay on top. On average 39% of Bins come right off the top with zero digging.

How much digging does AutoStore require?

A typical AutoStore Robot fleet spends 80% of the time serving Bins and only 20% digging. Much of the digging is opportunistic, during breaks and overnight, while other systems sit idle.

Robots never wait to dig. Bins needed for orders are proactively set on top through Bin preparation based on warehouse management system (WMS) priorities before fulfillment at Ports. This means operators are never waiting.

It is always possible to produce a Bin without notice. In the worst case, a bottom bin takes 3 minutes and 36 seconds, say for a hot order. If this is needed frequently, we merely add a few more robots.

AutoStore Bin digging explained
The average Bin is located just 2.5 cells deep in the stack and takes about 27 seconds to retrieve.

But keep in mind that more than a third of Bins require zero digging. Let’s use a typical AutoStore customer to understand why. This system is 25-feet-tall, the equivalent of 16 Bins stacked in the Grid. About 80% of products ordered from this warehouse make up only 20% of the overall inventory. Based on this 80/20 example:

  • 39% of Bins would come right off the top with zero digging.
  • The average Bin is located just 2.5 cells deep in the stack and takes about 27 seconds to retrieve.
  • The bottom half, or 8 levels, represent less than 5% of Bins needed.

Compared to other ASRS systems that move Bins vertically by climbing or using lifts, AutoStore is just as efficient, and often faster at fulfilling orders.

Digging effort is offset further by three unique AutoStore features that save Robot time:

  • Density makes travel distances 25-40% shorter once we have the Bin.
  • A wide-open Grid at the top provides a high-capacity environment for Robots to move efficiently, especially with Router™ software.
  • No time is wasted in queue when Bins are delivered to Ports and the decoupling of Robot and human work takes place.

Many other systems have longer travel distances and their robots waste time by having to move around warehouse structures, navigate aisles, or wait in long queues at workstations. The addition of sorter loops and elevators create additional bottlenecks and central points of failure.

Meanwhile, the average AutoStore Robot can achieve 30+ Bin deliveries an hour.

Here's further proof of how well the system performs: As of March 6, 2023, the average digging depth of 350 AutoStore systems measured just 2.6 Bins deep, which is a perfect 80/20 distribution within a Grid 16 Bins high. This statistic shows how well AutoStore manages digging for a huge range of customers.

No system on the market can achieve that level of performance.

How do AutoStore and its partners meet service level agreements?

Every AutoStore is simulated to ensure it meets customers’ performance expectations. In fact, we simulate over 500 designs a day to test different scenarios and Robot counts for our integration partners who design, install, and commission each system. The most important outputs are: 1) did we achieve the throughput and 2) did we maintain high port utilization.

Accurate simulation testing allows us to fine tune the AutoStore system so that it's optimized for high performance. For example, the testing process helps detect bottlenecks or study wide-ranging scenarios in an effort to minimize Bin wait times while using the minimum number of Robots.

Think outside the cube

Much like you don’t question where your hard drive stores bits, you can trust AutoStore to manage stacks of inventory inside the Grid. Remember, the "magic" of AutoStore isn't magic at all. It's a perfectly organized cube that keeps every item at your fingertips, just when you need it.

With AutoStore, your operations team won’t need to worry what's going on inside the cube, and instead spend their time on what matters most — fulfilling customer orders.

“The solution to a Rubik’s Cube is merely a series of well-planned algorithms. Likewise, the 'magic' of AutoStore isn't magic at all, but the logical result of arranging inventory in the world’s densest order fulfillment engine.”

Jon Schechter
Vice President, North American Business Development
Peter Bimmermann
Managing Director, Germany

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