AS most readers understand, the productivity of order pickers depends largely on the location of goods, which can be determined entirely by a Warehouse Management Solution (WMS). Using software to specify the optimum warehouse slot can improve productivity, ergonomics, security and quality.
But how do you determine the best location in a warehouse for your products? Most companies begin by looking at their order pattern. Fast-moving products are placed in the front of the warehouse while slow-moving ones are placed in the back.
This strategy works as long as fast-moving products do not all end up in the same aisle. If this happens, a new problem can arise: congestion. It is very easy for activity levels in one place to become so high that order pickers find themselves in each other’s way.
Determining the best location for each product is a complex job, as productivity, ergonomics and security all need to be taken into account. It is impossible to apply a simple rule of thumb or a formula to all warehouses or distribution centres as product characteristics, movement of goods and warehouse layout are different for each company.
Daily slotting
All warehouses and distribution centres need to set up a slotting plan at least once, to determine the best location for products.
In reality, most warehouses have to optimise slotting layouts more than once. As new products are introduced and demand for existing products increases, fast-moving goods are added and slow-moving goods disappear. Many companies therefore carry out a yearly, monthly and even weekly slotting review. In a few cases this may even take place on a daily basis.
Some warehouses operate a fully automated system, whereby goods are arranged automatically at night by machines, ready to be picked the next day. A similar procedure takes place in warehouses where large volumes of orders have to be picked within a short period of time.
In order to free up the maximum level of manpower for order picking, incoming goods are set aside initially, and positioned later. Some systems can also support automated slotting of new items as the WMS becomes aware of them. This helps avoid costly delays in receiving and put-away of new items.
Location, location, location
One benefit of optimised slotting is higher productivity gained by a reduction in walking distances. This can be achieved not only by putting fast-moving goods to the front but also by grouping together those products that are regularly sold together. It is also more efficient to put bulk stock close together for replenishment.
Fast-moving goods are best located at waist-height in warehouses with ‘roll-on’ racks. This serves not only to improve pick rate and productivity but also provides the best ergonomic solution. For the same reasons heavy products are best placed at hip or shoulder level.
In addition to productivity and ergonomics, efficient slotting brings security benefits. For instance, in warehouses containing volatile substances, products may not be placed close to each other because of possible chemical reactions.
A good slotting plan can also help to limit damage and mistakes. Heavy products should be loaded at the bottom of a pallet and not on top of breakable products, for example. Furthermore, picking errors can be reduced by avoiding the placement of similar-looking products together.
The job of calculating an optimised slotting plan, one that takes into account all of these factors, is vast and nearly impossible with a paper-based system, which is where a WMS with a slotting optimisation function comes in.
Data is entered into the WMS, including the measurements, location, number of products in a box, number of boxes on a pallet and storage conditions of each article. Information about the pick location is also needed; this includes its measurements, carrying capacity, walking distance, and the type of products that may be put on it.
Finally, the system requires data about the movement of goods, such as the number of picks per product and its demand forecast.
To make its calculation, the system distinguishes between constraints and goals. Constraints, such as weight restrictions or storage conditions for harmful substances, have to be met by the location layout. Goals are elements that have to be optimised, such as the walking distance between picking points or the allocation of jobs.
The result from the WMS will be a series of suggested re-slotting moves for layout alterations. It is up to the management of the warehouse to follow these plans. In addition, a WMS can determine racking requirements for new facilities or determine if changes are required within existing facilities to ensure a fully optimised slotting layout.
*Anil Chinnabhandar is consulting manager of performance services at Manhattan Associates, 02 9452 3200.