How to optimize order picking and reduce warehouse errors with PTL systems

PTL (Pick To Light and Put To Light) systems are systems to assist warehouse order fulfillment. The first (Pick To Light) are used to guide the picker in the picking operations, while the others (Put To Light) are used to help the operator in the distribution of the goods picked up by indicating to which shipment and in what quantity to assign the products.

The peculiarity of these solutions consists in the fact that the operator is guided by a system of indicator lights that light up, in the correct sequence, at the locations containing the material to be taken or deposited, hence the name that describes them “Pick” To Light and “Put” To Light.

In the Pick To Light the system instructs the operator to pick up the materials contained in the positions corresponding to the lights on, while in the Put To Light the lamp lights up in the positions where the operator must pour the material taken.

The indicator lights are mounted on panels, also called spots. Normally on the spots, in addition to the luminous lamp that can be lit with different colors and intermittences in order to allow greater dynamism of use, a more or less extended alphanumeric display is also mounted to communicate additional information (for example the quantity to be moved) and one or more buttons to allow the operator to interact with the system.

The spots are governed with a dedicated control unit which is in turn controlled through a software module integrated with the departmental software for warehouse management (Warehouse Management System).

In some cases, accessories and sensors can be applied to the spots for the automatic detection of withdrawal or deposit operations. This adds further verification of the operator’s action and eliminates the need to confirm the operation by pressing the button.

Pick to light

The Pick to Light systems, also called Pick By Light, are part of a Man To Goods context that distinguishes conventional warehouses characterized by manual picking.

These systems are particularly suitable for the management of small bulky items, in situations where important performances are required, or in the kit composition activity where operators find themselves having to pick up a large number of references, very similar to each other, in a very short time.

The classic Pick by Light system consists of dynamic shelving and with multiple accumulation depths, which are divided into zones and compartments, on the front of each compartment a spot is mounted equipped with a light lamp, numerical display and confirmation button.

The picking sequence begins at the beginning of an area where the operator scans a barcode label attached to a carton or other container where the goods are collected for shipment. The displays in that area tell the operator which products and how many units of each to pick up. The operator confirms withdrawals via a validation button, then moves on to the next zone.

When the shelf is very large, each zone is assigned to an operator who receives the carton or container from an automatic belt, performs all the withdrawals provided in his area for that container and puts it back on the belt that transports it to the next area.

The situation described above is only one of the possible configurations that can be implemented depending on the needs and characteristics that distinguish each case.

The association of the progressive number to each box, in addition to serving the picking operator to indicate to the system for which order he wishes to make the withdrawals, ensures the traceability required by downstream activities (weighing, packing list, label printing, final destination).

Stocks in the multi-depth shelf are replenished on the opposite side of the shelf by operators or, in some cases, by automatic systems, for example by shuttles or miniloads.

Put to light

In Put-to-Light systems, also called Put-by-Light, the light displays instruct the operator on where and how to allocate the material taken by distributing it to the individual destination orders, thus allowing to increase the efficiency in picking by handling large quantities in the least number of passages in the warehouse possible.

Put to light systems are implemented both in Man To Goods and Goods To Man contexts and can be both fixed and mobile:

  • In the first case they consist of a shelf or in any case of a fixed structure divided into compartments, each of which is equipped with a spot equipped with a light lamp, numerical display and confirmation button. In some cases the shelf or structure has a buffer consisting of gravity rollers where the complete packages are stationed until, once the packaging of an entire order is finished, they are picked up to undergo the last processing before shipment (weighing, labeling, palletizing, etc.);
  • Mobile structures, on the other hand, are made up of trolleys organized like fixed structures, they are in fact divided into compartments and each compartment is equipped with spots. The trolleys are connected to the rest of the system via wifi network.

The fixed Put To Light are used to gut on individual destinations products that have previously been taken from the warehouse with a massive picking logic. The warehouse operator picks up, in a single turn, all the products necessary for the fulfillment of a batch of orders by aggregating them on a logistics unit and taking care to keep them divided by reference. Once the picks have been taken, he delivers the goods to the unwinding area where the operator reads the bar code of each product, or of the container that contains it and the indicator lights mounted on the structure indicate in which container to insert it.

When the picking orders include small quantities and a package is sufficient to contain the contents of an order, it is possible to pick and pack using the equipped trolleys, in this case the operator makes the mass withdrawal from the warehouse (for a number of orders that is usually equal to the number of compartments in which the cart is divided) and immediately guts the products following the instructions given by the spots mounted on the trolley.

The main advantages of this way of operating are represented by the simplicity of use and speed of execution while maintaining a high level of accuracy in verifying the operator’s activities. They are also particularly appreciated solutions as the operator can move easily, working completely hands-free.

whSystem®, the WMS produced and distributed by Technolog for the management of automatic and conventional warehouses, has a module for the management of PTL systems.

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