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Picking the Right Picking Solution

There are so many options available that your head might start to hurt as you seek to understand them all. New robotics companies are exiting stealth mode each year, with many promising to revolutionize the warehouse picking process as we know it. Several parameters must be carefully analyzed to make the best decision for your warehouse or distribution centre. Let’s start with a summary of the categories:

1. Manual Picking

In some warehouses, where Stock Keeping Unit (SKU) counts are relatively low, order volumes are modest, and delivery time commitments are not overly stringent, it is difficult to justify even modest levels of investment in automation. Manual workers, picking orders with the aid of printed pick lists, still have their place - but the automation bar is lowering each year.

2. Non-Mechanized Person to Goods (PTG) Picking

The next step up from manual picking is a low-automation environment, where lights may be utilized to illuminate the next pick location, or voice commands may be issued to instruct pickers donning headsets. Intelligent picking algorithms implemented within a Warehouse Management System (WMS) or Warehouse Execution System (WES) optimize walking paths and reprioritize them as needed in real time. There are multiple variations (zone picking, batch picking, cluster picking, discrete order picking, etc.), all of which can have a dramatic impact on picking efficiency, depending on the specific SKU and order profiles. Items are picked into barcoded totes, lined up in manual push carts, until the picks for all totes are complete. The carts are then pushed downstream to another pick location, or to an order consolidation or packing area.

3. Mechanized PTG Picking

The next logical progression in a PTG environment is to add in mechanization, typically in the form of automated conveyors and sorters. Rather than picking items into totes that are stored in manual carts, they are picked into totes that wind through the various zones and aisles on automated conveyor belts. This alleviates the need for warehouse workers to spend unproductive time pushing carts from one area to the next. Scanners read the barcodes on the totes, enabling the WES software to determine where to send the tote next, and to activate the appropriate sortation diverts within the conveyor network.

4. PTG Picking with collaborative Autonomous Mobile Robots (AMRs)

Rather than a bolted to the ground conveyor system, collaborative autonomous robots may be used for the same purpose. A picker walks through assigned aisles as in other PTG environments, but a collaborative AMR is always nearby. When a pick is completed, the items are deposited into a tote on an AMR. When all picks for the tote are complete, the WES directs the AMR to move to a downstream area to assist another picker. A new AMR replaces the one that just departed, to work alongside the first picker. Totes are continuously moved from one pick area to the next, until all picks are complete and orders can be consolidated or packed.

5. Highly automated Goods-to-Person (GTP) Picking

One of the best ways to reduce labor requirements in a warehouse is to bring the goods to the picker, rather than the other way around. Technologies like automated shuttle systems have been around for a long time. They can store tens of thousands of totes up to the ceiling in a warehouse, rapidly retrieving them in the required sequence before sending them to ergonomically designed picking workstations. Computer screens direct pickers to move the displayed number of items from the retrieved totes into adjacent order totes. The pickers never move, saving valuable walk time and dramatically improving efficiency.

6. GTP Picking using AMRs

GTP picking can also be achieved with AMRs. Swarms of robots move beneath modular storage racks, transporting them to human pickers when contained items need to be picked. When the associated picks are complete, the robot returns the modular rack to an appropriate location. The approach was initially deployed by Amazon with their Kiva system. Alternatively, storage and retrieval devices can be attached to select AMRs in a fleet, enabling them to move autonomously through aisles to extract the required totes. As with traditional GTP systems, the totes are presented to pickers at ergonomic workstations. When all picks from a retrieved donor tote are complete, the AMR returns the partially depleted tote to the rack.

7. Goods-to-Robot (GTR) and Robot-to-Goods (RTG) Picking

Sophisticated, machine learning based vision systems, utilizing 2D or 3D cameras, have made GTR picking a reality in recent years. Articulated arm robots with associated controllers and specially designed end effectors are able to pick items in many environments, at rates and accuracy levels that rival humans. Robotic pick stations replace some of the standard pick stations. In some environments, the WES is configured to send the more difficult picks to human pickers and simpler ones to robotic stations. While not yet deployed in production, RTG solutions are also under development by some vendors. AMRs, equipped with articulated arm robots, move up and down aisles much like human workers, picking individual items out of static storage locations.

So, how do you decide which approach is best for you? There are some basic metrics that can help you get started. At a high level, individual pick rates in manual warehouses average between 25 to 50 picks per hour. In non-mechanized PTG environments, they approach 100 picks per hour. In mechanized PTG environments, they average closer to 250 picks per hour, per person. In GTP environments, the pick rates usually exceed 500 picks per hour, per station. These guidelines should be compared against the average throughput requirements of your warehouse.

While automation is quite costly, so is labor. Automation prices vary widely based on the technology choices and the overall breadth of a solution. There are some useful rules of thumb, however, to help guide your decision. Non-mechanized PTG solutions usually range between $200k and $1M. Mechanized PTG solutions and highly automated GTP solutions have average price tags of approximately $10M and $30M respectively. The price of an AMR-based solution varies widely, as it depends on the number of deployed robots. With the fully burdened price of an AMR averaging around $75k and an articulated arm robot closer to $150k, it is possible to conduct a rough labor versus automation cost analysis.

If the return on investment (ROI) period is less than three years, a good case can usually be made in favour of automation. Assuming each warehouse worker earns around $50k per year, or $150k over a three-year period, a $1.5M investment in automation may be justified by hiring 10 less people over that period. If an operation runs multiple shifts, the investment may be even easier to justify. With staffing shortages prevalent in the warehousing industry and rising customer expectations for receiving ordered products on their doorsteps within a day, the automation decision usually extends well beyond a simple cost analysis. Efficiency gains cannot be achieved by adding people alone, and with the ever-increasing cost of land, automation is often required to maximize the value of smaller footprint warehouses.

Anticipated growth must be analyzed carefully and balanced against a company’s overall tolerance for risk. While the highest pick rates may be achieved using trusted technologies like shuttle systems, they do require a significant up-front investment, usually implemented with some added capacity to future proof against growth. AMR-based solutions provide new opportunities to help more reluctant customers, enabling them to prove out their automation strategies with more modest up-front investments. These solutions are inherently scalable, quick to deploy, and can easily be transported from one warehouse to another.

With the myriad of automation options available to customers and accelerating e-commerce growth rates, there is no mystery why the warehouse automation market is expected to continue its rapid rise.

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