Pick to Light or Put to Light?

Picking and sorting are one of the two fundamental activities carried out in a warehouse. Biggest piece of workforce is usually employed in these two activities. Thus, there is always a pre-eminent potential for improvement in these activities. Traditionally both activities were paper based, accuracy and productivity were vulnerable to worker’s skill and attention. With rise of sophisticated warehouse management systems (WMS), paper-based picking and sorting was replaced with system assisted picking and sorting with the help of hand-held terminals (HHT). But in both cases one thing was still reliant on worker’s competence and that was identifying the item to be picked and sorted physically. Although system can guide him to the location but reading the barcode, identifying the item and location number was still reliant on worker’s skills and attention. Easy solution for this; what if the location or the item identify itself to the workers and they can blindly pick them? In both pick to and put to light system, items identify themselves with the help of a light and screen showing quantity to be handled. Usually they are accompanied with a barcode to register activity in the system. And in elementary words this is how pick to and put to light system work. 

Pick to light is basically system assisted order picking system. Shelving locations are fitted with the light and screen to show which stock keeping unit (SKU) need to be picked against an order. One light usually represents one SKU and a location. These shelves are right in front of a conveyor which carries crates or cases which represents one customer or order. Picker needs to scan the crate arriving on the conveyor in front of him which triggers the lights on the shelves for the SKUs along with the quantity which need to be picked. Once he picks and places those SKUs in the crate, he need to register his pick in the system with the method available for him which may be scanning the barcode or pressing a button provided for each SKU on the shelve near the location. Then crate is moved to different zone. This process is repeated until the crate is full or order is fulfilled. Once the crate is full order is fulfilled it is moved to the packing area. 

Put to light is basically system assisted unit sorting system. Physical configuration of put to light system is identical to pick to light modules. The major difference is; in put to light locations on the shelves with lights and screen represent customer or order. Single SKU crates or cases inducted on the conveyor in front of these shelves are with the units those need to be sorted with the help of lights into the customer bin on shelves. Putter needs to scan the SKU crate on conveyor and in response to this, lights on the shelves with customer demanding that SKU will glow along with the quantity required. Putter puts the required units in those customer bins and registers the activity in the system. This process is repeated until the customer bin is full or all the units required for that order are sorted and fulfilled. Once the customer bin is full it is pushed behind the shelves on the packing conveyor.

Put to light is suitable for the distribution centers (DC) with very high throughputs and fixed number of SKUs and customers requiring many SKUs. Example of this type of profile can be witnessed at mother DCs of retail and wholesale stores. With this type of profile Picking effort is lessened with consolidation of orders SKU wise and are batch picked to be fed to put to light system for sorting. Physical characteristics of SKUs preferred are small, dense and easy to grab in a bunch. This system is not preferred when units per line is equal to units per case.