Comparison of picking techniques

Published on: April 6, 2021 / Update from: October 27, 2021 - Author: Konrad Wolfenstein

Comparison of picking techniques

In times of an increasingly tough national and international competitive environment for companies, the pressure to increase productivity is also constantly increasing in logistics. This does not stop at intralogistics, in which the focus of efforts is particularly on the area of ​​order picking: more and more goods, components or raw materials have to be stored and moved - and ideally this always faster, more cost-effectively and in a more resource-efficient manner. It's no wonder that, given this impression, automation is finding its way into more and more companies. Dynamic storage solutions such as shuttle systems or horizontal carousel warehouses are one way to increase productivity in the warehouse.

But even the extensive use of such devices requires human workers to pick all the items; even if their share continues to decrease with increasing automation. In order to make work easier for warehouse employees and increase throughput, there are a number of tools that guide people using visual or acoustic signals.

But which system is better when and for whom depends largely on the situation. Depending on the warehouse structure, type of item and noise level, one or the other picking system has advantages and disadvantages.

Pick by light

With pick-by-light, warehouse workers are guided to the storage compartment or order container using optical signals. There is a signal lamp with a display that shows employees all the information relevant to the picking process. With this system, items can be stored and retrieved: Employees either remove items from the storage compartment or distribute the quantity of goods to different locations. The employee then confirms the completion of the picking process using the acknowledgment button, which is also attached to the display. This information is then forwarded to the ERP system in real time.

Advantages

• Fast picking
• Reduced error rate
• High picking frequency per storage location
• No long learning time
• Employees have their hands free

Disadvantages

• Comparatively high costs for acquisition, maintenance and repair
• Inflexible because adjustments to storage location, items or number have to be laboriously incorporated into the displays
• Picking error due to undetected system failure

Pick-by-light is particularly suitable when high picking speed is required. The system is often used in combination with automated storage solutions, in which the items are provided goods-to-person principle Examples would be picking small parts, picking components for assembly or dividing large quantities of goods into small shipping units.

Pick by voice

Pick-by-voice is now one of the most proven picking methods. No wonder, as the system ensures maximum freedom of movement and flexibility for the order picker, as he always has his hands and eyes free to process the order.

Instead of a hand scanner, the warehouse worker wears a headset through which he receives orders via a computer voice. The orders are sent by the warehouse management system via radio and later reported directly back to the system in the same way. Once an order has been carried out, the employee acknowledges this via a confirming voice input.

Advantages

• Short search times
• Precise picking
• Employees have their hands and eyes free
• Freedom of movement and flexibility

Disadvantages

• High initial investment
• Limited use if there is a high level of noise in the warehouse
• Multilingualism may be required
• More complicated training

Comparison

The methods presented have specific advantages and disadvantages and are each suitable for certain types of articles and areas of application:

Size and weight
For large and heavy goods, pick-by-voice systems allow greater flexibility and easier operation, whereas pick-by-light reaches its limits for large and heavy goods. Pick-by-light can particularly demonstrate its advantages in small storage areas or in conjunction with automated storage systems.

Turnover rate
For fast-moving items that need to be picked more frequently, pick-by-voice can usually only achieve a medium picking performance. Pick-by-Light, on the other hand, scores points here with its high picking performance.

Especially compared to pick-by-light, the voice solution has advantages in terms of versatility, flexibility and greater precision. To do this, compromises have to be made in terms of speed.

Another advantage is that the pickers have a clear view of both their hands and are not distracted by lamps or displays. This means they can concentrate better on the actual tasks. In addition, the error rate is further reduced because information can not only be received by the controller, but also returned to it. This enables efficient control and, if necessary, immediate error correction. If shortages are detected, repeat orders can be initiated.

Pick-by-voice technology is becoming increasingly popular among intralogistics. But there are also counterexamples. The office supplies retailer Soennecken switched the picking processes for small parts in its logistics center from pick-by-voice to pick-by-light. According to the company, the conversion improved working conditions in picking and increased picking performance by 10 percent. The starting point for the change were complaints from employees who found the optical signals of the pick-by-voice system increasingly stressful. The conversion took place during ongoing operations, after which, according to Soennecken, the working conditions suddenly improved significantly.

Pick-by-Vision: Combination of advantages

One of the newer methods to make picking easier is pick-by-vision, which combines the advantages of pick-by-voice and pick-by-light in one system. In this approach, which was co-developed by the University of Munich , the employee works with data glasses whose display shows relevant data about the current order in real time. They are used to guide the order picker step-by-step through the order. A navigation function takes them directly to the storage location of the item to be picked, where the corresponding storage location and the required number of picks are displayed via a visual display. Optionally, the data glasses can be expanded to include a camera for recording barcodes. This makes the usual hand scanner unnecessary.

The advantage of data glasses (also known as head-mounted displays, HMDs for short) is that, in addition to the data projected onto the display, the user can still perceive the surroundings without interference and has both hands free to process the order. In this way, the employee is constantly informed about the type and nature of the items to be picked or their location. In addition, he receives immediate feedback if he has made a picking error.

But the data glasses are not a one-way street on which the warehouse worker is busy completing the tasks assigned to him. Instead, the order picker can use voice control to interact with the control system and make changes. This innovative method is still in its infancy, but as such communication systems continue to develop, it can be assumed that the glasses will be found in more and more logistics facilities in the near future.