Everyone – particularly retailers – wants less inventory in store so the amount of break-bulk and ground level picking of single items is growing fast. In this article John Maguire, sales and marketing director of Narrow Aisle Ltd, considers how warehouse designers can make maximum use of their storage space without compromising order picking efficiency.
Of all the processes involved in modern warehousing, order picking tends to be the focus of most attention when it comes to designing a new storage system. This is understandable as most warehouse or distribution centre operations process more outgoing orders than incoming loads and, of course, the ability to quickly and accurately collate picked goods is rightly regarded as having a direct link to efficiency, costs and, in the retail sector, customer satisfaction.
Of course, designers of internal logistics systems remain under pressure to make maximum use of all available storage space within the warehouse facility but, in their attempts to reduce aisle widths to an absolute minimum, they can, sometimes, compromise order picking efficiency.
“While the methods employed for order picking will depend on a wide variety of factors such as the characteristics of the product being handled, total number of transactions, total number of orders, picks per order, quantity per pick, picks per SKU, total number of SKUs, etc, in simple terms, the vast majority of customer order picking is undertaken from palletized loads placed at ground level within pallet racking – with the reserve or bulk stock stored above,” says John Maguire, sales and marketing director of articulated forklift truck specialist Narrow Aisle.
John Maguire continues: “Within e-fulfilment facilities and sites that serve the grocery retail and chilled and frozen food sectors, the trend is for customer orders to be made up of progressively smaller quantities of varied product lines, rather than full pallet loads of the same product. As a result, the proportion of ground level order picking is increasing and traditional deep-store storage systems can no longer be perceived as the most effective storage method.
In many grocery retail RDCs ‘zoned’ picking is designed to match the layout of the retail store that the order is destined for and, to minimize the time the pickers spend traveling between pick locations, pick-lists produced by the WMS often only feature products from one or two RDC aisles. Order picking staff will be instructed to pick the same items from the same SKU but for different store locations and place them onto perhaps two pallets or three roll containers. As a result, the low level order picking function in one location can take up to 10 minutes at a time. Therefore, to ensure that the aisle is not blocked for that kind of period, most existing manual warehouses have been built around 3.2 metre wide aisles – often with bridged intersecting aisles that allow order pickers and moving mast reach trucks to pass. While such designs optimize low level order picking volume and efficiency, the extra space required within the storage cube can lead to a 30 per cent increase in the overall cost per pallet stored within the facility.
To overcome this inefficient use of space many warehouse designers have traditionally tried to turn to wire- or rail-guided man-Up combi VNA machines. Man-up (or man-aloft as they are sometimes called) combis work in very narrow aisles and use a main lift to raise not only the load but also the cab – where the operator stands or sits – to the required position in the racking.
However, as John Maguire explains, a number of issues must be considered when using VNA man-up combi trucks if efficient ground level customer order picking is a significant part of the warehouse operation.
“To be efficient,” he says, “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.
John continues: “Furthermore, low level order picking in the same aisle at the same time as a man-up truck is working can be dangerous because the man-up machine’s elevated operator position makes it difficult to see an order picker working at ground level – 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.”
All of these factors, John Maguire contends, has led many logistics experts to believe that what – in the early days of the man-up VNA truck – were seen as the truck’s key advantages, are now handicaps. “Elevating an operator several metres into the air to pick single items often with large travel distances between picking locations can now be demonstrated to be uneconomical on a cost per pick basis for all but those applications where the most high value items are stored,” he says.
Many of the difficulties created by low level order picking within a guided VNA system can be overcome by the use of articulated forklift trucks.
“While they require slightly wider aisles than VNA man-up combis, articulated trucks – such as the FLEXI from Narrow Aisle – offer distinct advantages at sites where there is a need to low level order pick at ground-level stock locations,” says John Maguire.
“For example,” he explains, “the actual aisleway is not constrained by guidance systems and fixed stacking depths/traverse strokes so the whole building width can be utilized. By incorporating bridged intersections into the racking design, say, every 30 metres, 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, low level order pickers working in the same aisle can be easily seen – making the operation safer.
Narrow Aisle has a number of clients who, faced with the need to deliver greater pallet selectivity and order assembly, have changed the way they run their operations to ensure that both picking efficiency and worker safety are optimised.
“For instance,” explains John Maguire, “one of our clients – a third party warehousing company – stores frozen ready meals on behalf of one of the growing band of small businesses to have entered the sector. The firm is enjoying considerable success producing premium quality ‘home-made’ food in small batches, blast freezing it and selling it though delicatessens, farm shops and on-line outlets.”
“Traditionally the majority of movements in and out of the store had been full pallet loads. However, the success of its frozen ready meal-producing client forced the storage company to reconfigure its cold store to allow individual customer orders to be assembled.
“At first the company considered installing very narrow aisle trucks guided by either steel rails or inductive wires cut into the floor. However, the client decided against going down this route because, it was felt, that steel guide rails would limit access to key ground level picking locations. Furthermore, the proposed aisle dimensions were too narrow for low level order picking.”
Eventually the company settled upon a combination of Flexi articulated trucks and low level order pickers. The Flexi does not require wire guidance or steel rails and therefore the aisle width could be set to suit the customer’s order assembly profile. The lack of steel guide rails meant that the first rack beam could be set at two metres to allow fast case picking.
Meanwhile at another third party cold store client’s facility the combination of powered mobile racking and Flexi trucks has allowed 6200 pallet locations to be provided after initial tests showed that the use of static narrow aisle pallet racks and traditional VNA machines would have restricted the facility’s capacity to 5000 pallets.
The company – Norish – completed the acquisition of a 45,000 sq ft cold store facility in Gillingham, Kent, in March 2008. The site, which is located close to the M2, had previously been operated by Premier Food Group but had become surplus to the food manufacturer’s requirements.
On taking ownership of the unit, Norish embarked on a significant upgrade of the facility.
The previous owners had operated a storage system based around very narrow aisle racking and turret trucks. Norish considered this arrangement inefficient: the turret trucks, for example, required a five metre wide transfer aisle – something that Norish’s management team quickly identified as a waste of potentially valuable storage space. As a result, a new storage solution was sought.
Having considered several alternatives, Norish opted for a system with powered mobile very narrow aisle racking supplied and installed by Index Procon and served by Flexi articulated forklift trucks from Narrow Aisle at its heart.
The site’s original configuration had provided 4,000 pallet positions in two frozen chambers operating at -25°C.
Norish took the decision to sub-divide one of the chambers – giving three separate and self contained units in total; one of which would be operated at chill whilst the other two would operated as frozen storage chambers.
With each of the chambers fitted with powered mobile racking with very narrow aisles and fed by Flexi trucks, the Gillingham facility now offers 6,200 pallet locations – a 50 per cent increase pallet capacity. This remarkable expansion in available pallet spaces has been achieved without extending the physical dimensions of the building.
Another Narrow Aisle client – the Asian food wholesaler Natco – opted for a fleet of Flexi articulated trucks at its Buckingham site.
Natco had originally considered guided VNA man-down turret trucks at the facility which it moved in to in October 2006. These machines could operate in aisles as narrow as 1900mm wide with a UK pallet 1.2 metres deep, but because Natco’s operation involves a high degree of ground level order picking they were not the ideal choice as it can be difficult for low level order picking tasks to be carried out in such narrow warehouse aisles because an order picker needs at least 500mm clear each side of a 1000mm wide pallet to work safely and efficiently.
Man-up Combi trucks were another option but were considered a potential risk, as Sajid Khoker, Natco’s operations manager, explains: “In its elevated position a Man-up Combi VNA truck might lift the operator 10 metres in the air, but if you have someone in the same aisle order picking at ground level there is always the risk of the combi operator not seeing the orderpicker or worker below. In our opinion this made combis too risky.”
Having evaluated the various materials handling equipment options open to them, the company chose a fleet of five Flexi G4 HiMAX articulated VNA trucks from Narrow Aisle Ltd. Effectively two trucks in one, the Flexi’s design enables it to load like a counterbalanced machine – outside the aisles – but it can also work in very narrow aisles. This dual purpose functionality guarantees the user a wide range of benefits – not the least of which is the ability to travel to the goods-in area, then deliver pallets directly from goods-in to the VNA pallet racking in a single operation. By doing so, it increases efficiency and productivity while abolishing double handling and the costs associated with operating a bigger truck fleet than is necessary.
As well as providing greater operational flexibility, using a Flexi articulated truck ensures that warehouse operators get the most from their storage cube. It has been well documented that by operating a Flexi it is possible to increase pallet storage capacity by anything between 30 and 50 per cent depending on the current operation.
Clear aisle widths within the distribution centre at Natco are 2000mm wide and low level order pickers work at ground level in the same aisle as the Flexis safely and efficiently.
Natco’s operational efficiency has increased noticeably since the move to the new facility with products processed more quickly and deliveries to stores and restaurants up. Picking is also more accurate and order fill has increased significantly as all bulk products in stock can be found and replenished to the pick face at ground level during the pick wave.
John Maguire concludes: “There is a discernible trend in the mechanics of customer order picking with more demand for smaller volumes of outers per SKU more frequently which leads to more SKUs per pick list on customer orders to be picked. Everyone – particularly retailers – wants less inventory in store so the amount of break-bulk and ground level picking of single items within RDCs is growing fast. When the range of products (SKUs) increases the warehouse operator needs more ground level locations to maintain efficiency and, at the same time, they want to maximize the use of expensive warehouse space.
“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 traditional products such as man-up Combis can compromise order picking efficiency and health and safety within warehouses where there is a high degree of low level order picking.”
Narrow Aisle Ltd
Tel: 0121 557 6242
www.flexi.co.uk
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