The well-slotted warehouse

02/01/2015

Slotting for picking
Order picking can be the most labor-intensive and costly activity in a warehouse. The average full-time warehouse worker spends between 50 and 60 percent of his time in it. Personnel travel represents an obvious waste of time and money for any storage facility. The best way to address this issue is slotting references properly. Slotting consists of determining the most appropriate storage location for every product in a distribution center. The goal is to create the most highly efficient system where items are retrieved quickly, accurately and safely. Each design configuration depends on the facility’s products, traffic and storage properties.

We do slotting in our lives all the time. Construction workers do not throw their tools loosely in a bag, they use a compartmentalized bag to separate screwdrivers from hammers and other gadgets, so they can easily access them. We slot our kitchens, placing everyday items in the most accessible spots in our cabinets. Warehouse storage spaces are no different. With hundreds of SKUs, it is imperative to know where everything is and have access to it in a timely manner.

It is not only about configuration
The varied nature of products stored in warehouses makes slotting a complex process. The dimensions of the items stored and any special characteristics (cold storage or hazardous materials for example) have to be taken into account. Weight and height also play a role in how and where items should be placed.

The configuration of the installed rack has a big role in the slotting process. If a warehouse is storing outdoor equipment, for example, such as skis and camping gear, they will need to determine where to store each one in order to access them easily during their high seasons; spring and summer for camping and fall and winter for skiing. The difference in dimensions and configurations of these products will have to be considered when selecting the rack. In this case, a cantilever rack, with its extensive range of load capabilities and adjustable arms, offers the greatest versatility and will accommodate camping tents or skis. This way, the product will change seasonally, while the rack stays in place in the most convenient location.

Placement Rules
A well-organized warehouse with the highest picked items in the most accessible areas, stored in the right rack system, will save money in labor, space utilization and inventory control. The economic benefits of a well-sorted warehouse have helped warehouse owners and facility managers recognize slotting as an often misunderstood and overlooked building block of warehouse optimization. It is indeed a very important component of storage design, and although there is not a one-size-fits-all method, there are some basic rules and considerations that make the process easier and more effective.

Some of the rules include placing fast moving items close to the shipping docks and storing items with slower turnover further away from the loading area and on higher levels. Taller and heavier cases should be placed at the beginning of the pick path in the picking areas, while the faster moving cases would be better stored at floor level. Again, everything is relative to a specific facility’s layout and schedule, but patterns emerge that may be helpful to acknowledge when determining the effectiveness of a space’s slotting area (generally considered the space reserved for forward picking) and zoning (the area in which reserve inventory used to picked in full pallets or used to replenish forward pick area is held).

When storing items in carton flow rack, positioning the fastest products on the center level and balancing the workload among the flow rack units will prevent congestion during retrieval and speed up the picking process.

Slow moving items can be placed on standard rack, while the fastest ones can be closer to the conveyor belt. It is always important to balance the loads, with the heavier items on the center levels.

Step up the Organization Process
The first step to completing a slotting project is determining traffic flow and allocation of SKUs. A Warehouse Management System can help with this task by defining what items are retrieved most frequently and establishing a ranking system. An ABC classification is used by most distribution centers, with “A” being the fastest moving items and “C” being the slowest.

Once the hierarchy of products is established, the next step is to puzzle out the best location for those items. A common practice is to place the “A” items in the center levels of the flow rack, also called the “golden” zone, which is situated between chest and waist height, at an easy ergonomic level for the workers. This placement makes the retrieval of SKUs easier and safer.

Once the particulars of the items to be stored are sorted out, an implementation system has to be created. A well-developed WMS, such as EasyWMS from Mecalux, can make the execution of the process easier by performing calculations of the rotation of each item at intervals determined by the user. The program can also generate reports suggesting changes in the rotation of references and provide images of the warehouse with the exact location of references.

A storage facility is an evolving organism and, as such, it needs to be slotted and reorganized periodically. A study by the Insight Group showed that slotting every three to six months can increase efficiency 7 to 15 percent more than doing it once a year or less. Logical times to do this during the year would be at the beginning and end of each season (understanding this as summer, holidays, winter, etc.) or before and after promotions, when inventory needs and quantities change and shift.

Since warehouses are as varied as the products they store, each facility will have to adjust to its particular market fluctuations. A food storage facility will experience more demand of turkeys or hams, for example, during Thanksgiving and Easter, so they will stock up on those items and put them in the most accessible area of their cold storage units. A beverage distributor would benefit from keeping sparkling wine and champagne stocked in greater quantities in easy to pick areas for a couple of months leading to New Year, while that preferential space will be better utilized to store beer and soda in the summer months.

Smaller products that are rarely ordered in bulk, can be placed in the picking area in a vertical lift module, which often have easy retrieval systems that don’t require traveling time around the warehouse.

No matter the warehouse, slotting is as much of a necessity as an organized garage or a fridge with easy access to the beer. And much like the shelves in the fridge or the pegboard hanging the tools, the right warehouse system and WMS make slotting easier and maximizes any company’s resources.