That order pickers in a conventional warehouse spend almost
half their time busy walking from one pick location to another
is well enough known. Consider the report two years ago
of the BBC journalist who went undercover to work in a
Amazon.com warehouse. He complained of sore feet due to walking distances that
could reach as much as 17 kilometres during one shift.
Many warehouses try to reduce walking distances by allocating items to picking locations as smartly as possible, a process called slotting. In practice, this amounts to putting fast runners at the front and slow runners at the back. The warehouse management system (WMS) often lends a hand by calculating, based on past picking orders
which items are picked most or least often. Those items are then assigned to locations that are closest or furthest from the start or end point. This often already significantly reduces walking distances, but with a few handy tips, even more improvement is possible:
1. Look to the future
As mentioned, WMS bases its calculations of fast runners and slow runners on past pick orders. However, what was a fast runner last month may just become a slow runner next month. Much more interesting than the historical data is therefore the demand forecast: how many units of each item will be sold next month? So consult with sales and marketing what their expectations are and adjust the locations of items accordingly. Sales promotions and marketing campaigns in particular can significantly influence the demand for certain items. Vanderlande, Ortec, Centric and Slimstock have already
already explained this in a joint white paper.
2. Research which items belong together
In almost every warehouse, there are examples of items
that often appear together in one order. Think plastic coffee cups and
stirrers, matching scarves and gloves or smartphones and matching
cases. Those who want to reduce their walking distances would do well to place these
items near each other. When doing so, don't just rely on common sense
common sense, but do a thorough analysis of all orders. The chances are
chances are that this will result in combinations of items no one had thought of before.
thought of. Retailers have been doing this with their receipts for some time. For instance, a supermarket chain
once discovered that beer and nappies were often paid for at the same time in the evening. It turned out
that many young fathers were sent out around that time to replenish the supply of
stock of nappies and immediately took some refreshments for themselves.
3. Pay attention to the next link
When slotting, pay attention not only to efficiency in your own warehouse, but also to the efficiency of the next link in the chain. Supermarket chains already take into account the order in which items are shelved in the shop during order picking. Article groups that are
next to each other are also put together in the warehouses. As a result, these article groups are more likely to end up on one roll container, which prevents shelf stockers from having to slalom around the shop with roll containers between all the consumers during opening hours. What applies to supermarket chains may also apply to other warehouses. Think, for example, of warehouses for stocking production lines.
4. Look at the walking route
What makes slotting complex is that an order usually involves more than one item. Those who put their fast runners at the front and their slow runners at the back then actually ignore the fact that an order picker usually makes a round trip past multiple pick locations. So if the fast runners are spread across several aisles, the chances are that the order picker still has to visit several aisles and is therefore not actually working efficiently. Ronald Mantel and Peter Schuur of the University of Twente have therefore devised a method that aims to make the most efficient possible round trip along all the pick locations to be visited. With 'order-oriented slotting', the articles are placed in such a way that the total distance of all round trips is as small as possible. According to both scientists, this can save another 12 to 15 per cent in time.
5. Take pick height into account
Usually, slotting only takes into account
the distance to the pick location, not the height of the pick location. The
Peruvian scientist José Larco concluded in his doctoral research at Erasmus
University Rotterdam, concluded that pick height does
indeed affect productivity. Especially when it comes to bulky
items or a large number of items, picking from very high or very low
locations takes a relatively large amount of extra time. According to Larco, it is therefore
therefore best placed in the 'golden zone' between hip and shoulder height. That
is also better from an ergonomic point of view. Anyone who has to stoop or
all day, get tired sooner and may suffer physical complaints. That also
also reduces performance and efficiency in the long run.
Marcel te Lindert - Journalist logistics and supply chain
