The trend for consumers to drift away from the traditional ‘bricks and mortar’ high street retail experience and spend more and more time and money shopping online has implications for warehouse operations and storage facility design, writes John Maguire.
One major challenge, for example, is how to effectively combine the storage and picking of small consumer online orders with large store replenishment orders in a safe and space efficient way.
Clearly online order fulfilment requires more ground level picking locations yet warehouse operators need to maximize the use of expensive warehouse space by keeping the width of the aisles between the racking to a minimum and reconciling these twin objectives is sometimes less than straightforward.
Traditionally, many narrow aisle storage schemes have been served by wire- or rail-guided man-up VNA trucks combi machines, but with the growing emphasis on access to ground level picking locations, the restricted use of guided equipment in the picking aisle becomes less viable.
Indeed, a number of issues must be considered before using VNA man-up combi trucks if ground level order picking is a significant part of any omni-channel warehouse operation.
For example, to be efficient man-up combis require long, uninterrupted aisles that allow the units to lift and lower while traveling between pallet positions and, although they are designed to allow single-item picking as well as handle entire pallets, combis arguably work best within high bay stores putting away and retrieving full pallet loads rather than picking individual order items.
Furthermore, low level order picking in the same aisle at the same time as a man-up truck is working is forbidden because the man-up machine’s elevated operator position makes it impossible to see an order picker working at ground level – or any other vehicle with all too obvious potential consequences.
Also, due to their size, combis require up to six metre wide transfer aisles which obviously makes the use of regular bridged intersections within the racking impractical. As a result, low level order picking becomes very inefficient because the picker is forced to travel the entire length of the aisle he or she is working in to change aisles – thereby increasing the average distance between picks to an unacceptable level.
Many of the difficulties created by low level order picking within a guided VNA system can be overcome by the use of articulated warehouse trucks like the Flexi. They require similar width aisles to a man-up combi truck, but articulated trucks offer distinct advantages at sites where there is a need to low level order pick at ground-level stock locations.
For example, the actual aisleway is not constrained by guidance systems and fixed stacking depths/traverse strokes so the whole building width can often be better utilised. By incorporating bridged intersections into the racking design, say, every 30 metres, pallet put-away, low level order picking and pick face replenishment is dramatically improved and congestion in the aisleways minimised.
Our research shows that it is more space and time efficient to incorporate three or four, three metre bridged transfer aisles for articulated trucks and low level order pickers than, say, two, six metre transfer aisles (one at the front and another at the back) to enable combi VNA machines to change aisles.
However, perhaps most importantly, the articulated truck operators are seated at ground level (like reach truck operators) and, therefore, can ‘share’ the aisle with other Flexi trucks, low level order pickers and feeder trucks in a safe and productive way.
Because of its design, the articulated truck is perfectly suited to working in narrower aisles alongside order picking staff without creating a health and safety issue. From the feedback we have had there is growing concern that the use of man-up combis can compromise order picking efficiency and health and safety within warehouses where there is a high degree of online order fulfilment picking required throughout the store.
John Maguire is managing director of Narrow Aisle Ltd and a past chairman of the UK Warehousing Association.
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