Optimizing Picking Systems

Picking systems describes the process in which a warehouse takes to select and pull items from inventory to fulfill a customer’s order. It is essential for warehouses to find their optimal method for picking that ensures accuracy and efficiency. The cost of labor, materials, technology, and accuracy can all play a crucial role in maximizing their bottom line. Thus, distribution centers are left with different methods to consider – all of which have some advantages depending on one’s needs. For this case, we will analyze three different methods: pick-to-light, pick-to-paper, and voice picking.

Pick-to-Paper

Pick-to-paper, also known as label processing, is entirely reliant on the paper orders for warehouse procedures. Typically, this is also paired with digitized methods of information storage via desktop terminals. A warehouse associated completes their tasks listed on pick lists, put-away labels, or other label documents. This process is most optimized for smaller processes and for those operations that cannot afford the large barrier to entry for other systems. Overall, this is a simple method to implement in even the most primitive settings.

However, this is one of the slowest methods of picking with upstream (how information is written in the label) and downstream (scan and verifying via desktop terminal) processes impacting its performance. Due to the nature of recording paper orders, it is impossible for a warehouse to maintain a real-time track of their inventory – dependent on data entries made by other associates. This inefficiency and many points for error make this process difficult to scale into larger settings.

The picture below is a depiction of what pick-to-paper looks like.

Source: NEConnected

Pick/Put-to-Light (PTL)

Pick-to-light systems are among the most popular methods used in distribution centers. This process is much more intuitive, guiding associates via light to the products needed for each order. It is a simple-to-use technology that can support large pick rates. PTL systems are equipped with software that activates light displays for every needed location, displaying the quantity needed for that order. These benefits result in a company’s ability to get an average worker productive quicker and with less down time.

Still, this system is very expensive, technologically complex, and requires a large initial capital investment to ensure functionality. The cost of the software alone, is in the excess of $100,000. Plus, this method cannot be applied to anything other than order selection. This limits the method’s versatility when dealing with receiving, put-away, and cycle counting.

Below is a depiction of what PTL systems look like.

Source: Pick to Light

Pick-to-Voice (PTV)

Alongside pick-to-light, voice picking has proven to be one of the most popular methods of picking. For this system, an associate is guided through picking via an audio device that lists its necessary items. Voice picking is an effective method of picking most useful for lower velocity SKUs, full case and pallet picking. It has the distinction of being slightly more accurate PTLs while also being slightly cheaper.

A drawback to voice picking, however, can be seen in its ability to integrate new workers. While training times can be relative short compared to pick-to-paper systems, it limits the distribution center of the kind of worker who can do the job. Language barriers and audio limitations can play a large role in limiting the effectiveness of the method.

Below is a depiction of what a pick-to-light system looks like.

Source: Bastian Solutions

Compiled together is a table between the advantages and disadvantages between the three different methods.

Pick-to-Light (PTL) vs. Pick-to-Voice (PTV)

In this blog, we have established that both options are much better alternatives to pick-to-paper. Both options present a system that is easy to use, has more of an increased efficiency, improves accuracy, and as a result lowers overall cost. However, both systems are more geared towards a bigger scale operation as both systems are expensive to implement. We have put together a list explaining the specific differences between the two below.

  • Training Time / Ease of Use – Both PTL and PTV can reduce training times significantly. On average both systems can cut down up to 50% of the training time needed for pick-to-paper systems.
  • Productivity – Pick-to-Light and Pick-to-Voice systems are roughly the same in productivity. However, PTL systems have an added variability component where cheaper systems can be less productive. PTL systems can do approximately 110 – 350 lines per hour. This is very comparable to PTV systems which can do approximately 300 lines per hour. Still, on average both systems preform 25% better than paper systems.
  • Improved Accuracy – A more mechanized system of picking can reduce human errors. Both PTL and PTV systems allow for an associate to focus specifically on the product, instead of having to worry about labels or interfaces. As a result, PTL systems have an industry average of error at about 4 – 6 per 1,000 picks. PTV systems have an industry average of error between 0.2 – 2 errors per 1,000.

System Cost – Overall, both options are expensive endeavors. Pick-to-light systems attain most of their cost in the software required. PTL systems run at excess of $100,000 with each display costing between $100 and $150.

Pick-to-voice systems have options for how to implement the system. Voice terminals run above $2,500, vehicle mounted terminals run above $3,500, and wearable terminals cost above $2,000. More innovative technologies such as smart glasses are progressively being introduced into this PTV systems for about $800.

In the Real World

Warehouses mostly investigate PTL or PTV when they have reached optimum pick metrics using more simpler technologies such as pick-to-paper. PTL and PTV are mostly reserved for larger corporations looking to further increase productivity, accuracy, and reduce overall costs. For examples, Amazon has reported used PTL systems in their warehouses. This has been due to the language limitations presented by voice directed picking systems.

Meanwhile, the fourth largest pizza delivery chain, Papa John’s has replaced its picking process with voice-directed picking processes. This is especially useful in freezers, where temperatures can make working with hands more difficult.

 

RFID

Regardless of the differences between the three different methods of picking, there is one common denominator between the three of them. When picked, all items need to be scanned to provide management with updated information regarding inventory and movement of goods. Traditionally, this need is supplemented by barcodes – an effective, but a suboptimal method. This is where RFID can play a major role.

RFID (radio frequency identification) is a technology that is comparable to barcoding in terms of keeping track of data stored in a tag/label captured by a device and stored in a database. However, RFID uses radio waves to determine the movement of goods. This means that there is no need for optical scanners and a picker can focus solely on obtaining the right products to fulfill an order. Listed below are some benefits to RFID.

  • Simplifies tracking assets and inventory management.
  • Electronic control/upload of information reduces transcription errors.
  • Provides up-to-date data on inventory, ensuring availability of goods.
  • Saves overall time by automating and optimizing scanning.

 

Multipicking

RFID can be combined with different methods of picking to further increase efficiency. This where multi-order picking comes in. Multipicking is an effective method of streamlining order picking. This process involves the warehouse associate locating and picking multiple orders at the same time. Multipicking saves time by cutting down the amount of travel time made by the associate. This is mostly ideal for situations where a company must deal with many small orders.

This is where solutions such as Ehrhardt-Partner’s RFID multipicker can save time and cost. This product implements pick-to-light systems for multiple order picking and combines it with RFID technology for simple scanning. The RFID multipicker optimizes both the movement of multiple orders and tracking of goods at the same time.

Source: Ehrhardt-Partner

Conclusion

Overall, pick-to-voice and pick-to-light systems are extremely reliable. These technologies are not new and have been perfected over the course of decades. They serve as reliable systems to increase worker productivity, reduce errors, provide for ease of use, and overall create a return on investment over time. While smaller companies may find pick-to-paper systems more effective and easier to implement, this method should not be considered for companies looking to grow and expand. PTL and PTV systems can be extremely effective in ensuring appropriate picking. As to which is better for you, this would require more extensive research and tailoring to your needs. But either way, both are truly better and modernized for the warehousing issues of today.