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Fast and efficient online order fulfilment has become a key part of the success of marketplaces as well as many other e-commerce stores. As part of warehouse automation, there are systems that help streamline and speed up the process of locating and picking all the products that form a customer order, putting them in a box, and automatically updating the warehouse management system (WMS) that those products are now removed from stock.

A technology commonly used to provide this capability is ‘pick-to-light’. As explained previously in Technology compared: picking systems pros and cons, pick-to-light is one of many technologies used for picking. Others include pick-by-paper, pick-by-voice and pick-by-vision. However, in comparison to most, pick-to-light can offer improved throughput and efficiency, and in comparison to paper picking, it can help improve productivity by up to 50%


Why is that? This requires an understanding of how the system works. Here’s a typical process scenario:

  • Customer order comes in for products which are in multiple picking locations in the warehouse, all of which are connected to a warehouse management system (WMS).
  • Based on the order contents, the WMS guides the human order picker to the location of each product in the order, as indicated by illuminated switches at each storage location.
  • The illuminated switch at the location also displays a number indicating how many of that item must be picked.
  • The picker picks the indicated number of items and puts them in the order box, pushes the light switch to confirm the items were picked. Since the lights are connected to the WMS, the system is automatically notified of the corresponding reduction of stock of that item.
  • The picker then moves on to the next storage location as indicated by the illuminated light(s), and continues this process until all items in the order are put in the box.
  • The order is then ready to be shipped.

Looking at this process, the visual clues offered by pick-to-light switches offer fast response time, and since light is universal, training is simple and there are few language barriers, if at all. The picker can be trained simply to pick on a color – for example pick on green. The fast drop time makes the system scalable for high volume order fulfilment at speed.

Many warehouses use mechanical switches or push buttons, but these are prone to breaking down, can be unreliable and in a dusty warehouse the mechanical switches can get clogged up and hence performance can deteriorate. It’s easy to imagine the scale of the potential breakdown in the system efficiency if a warehouse location has, say, 10 mechanical light switches which by chance all fail at the same time. The probability might be very low for this to happen, but the potential for multiple sensors failing is real.

One way to overcome the reliability and durability shortcomings of mechanical switches is to use capacitive touch sensor switches such as the smartCAP solution from CAPTRON. Capacitive sensing can offer much improved reliability compared to mechanical switches. They are completely waterproof and dustproof with IP69K rating, which means they can withstand the harshest of environments. In addition, when integrated with a SENSORhub, they can operate up to 80 storage locations to guide warehouse pickers to the correct picking location and pick the correct quantity of product.

As an example, the world’s largest online marketplace was working with a standard pick-to-light system which usually consists of a seven-segment or dot-matrix display and a mechanical activator to confirm the employees’ pick. While the display and activator units were relatively inexpensive, the mounting support, as well as the wires and necessary software licenses and installations, make a pick-to-light system a major investment.

To address the reliability issue, the marketplace deployed the smartCAP capacitive sensor solution for its pick-to-light switches, which has now been in operation for two years. The main benefit has been an increase in efficiency by another 13.5 percent – enabling a total 65 percent improvement compared to ordinary paper picking. In addition, they also reported zero failures in operation.

The smartCAP solution can have seven LED colors which enabled the marketplace to customize the switches using different colors, animations and different activation types. In general, compared to many other solutions that only have three colors, the CAPTRON capacitive sensing switch solution can help guide multiple workers in a single zone, for example each worker picks on a certain color. Additionally, with the smartCAP solution you may reduce your hardware cost by integrating one button for many locations. The LED's can be split to display top/bottom or left/right picking creating a potential of 4 product locations per 1 switch.

In summary, pick-to-light systems in an order fulfilment warehouse can offer huge throughput and efficiency to enable high volumes of order fulfilment much more rapidly than by using other picking technologies. The main reason is the simplicity and universality of light. In order to improve efficiency even further as well as reliability, solutions like smartCAP from CAPTRON can provide other benefits too including customizability of colors as well as animations, which can make all the difference.


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